Introduction: Breast cancer is the most common cancer in women. The treatment of breast carcinoma has advanced in the last decade and nowadays there are treatment protocols for all stages of the disease. Depending on ...Introduction: Breast cancer is the most common cancer in women. The treatment of breast carcinoma has advanced in the last decade and nowadays there are treatment protocols for all stages of the disease. Depending on the histopathology and stage breast cancer is treated with surgery, chemotherapy and radiotherapy. Regarding radiation, the field of irradiation includes the chest wall in patients with mastectomy, or the breast glandular tissue in patients with conserving surgical approaches. It is often treated with radiation therapy with two opposing tangential fields, and when indicated supraclavicular lymph nodes have to be irradiated. In this case an additional anterior field is applied. The tangential as well as the other radiation beams have a potential damaging effect on the healthy surrounding tissues, particularly over the heart in the left breast irradiation and in the lungs as well. Material and Methods: The study included 25 patients with left breast carcinoma, all post surgery, treated with radiation therapy, with the Elekta accelerator at our department. For academic purpose the treatment plans were generated following two methods. The first one with two tangential opposite beams plus a supraclavicular beam. In this method the angles of the tangential internal and external create an angle that is equal to 180˚{310˚& 130˚};no further changes were made to the beam geometry. Even though this is not the best option from the dose distribution point of view, it is still the most applied method, probably because of the semplicity of it. For each patient, a second plan was generated using two opposite tangential beams plus the supraclavicular beam. The angles of the internal and external beam were changed from 1˚to 3˚, depending on the surface of the body, so that the resulting angle was 180˚± 3˚{310˚± 3˚& 130˚± 3˚} with the aim to adapt the beam geometry as much as possible to the shape of the thoracic wall and to spare the OAR-s. Results and Discussion: The data show that the dose in the organs at risk, in terms of dose percentage, is lower when the angles of the beams are changed with 1˚- 3˚, compared to the classic method where the internal and external angles equal 180˚. This dose is not only non-negligible but significant;for every angle change from 1˚to 3˚, there is a significant reduction in the integral dose in the radiated volume, expressed in percentage, up to 5%. Conclusion: In most centers, the radiation treatment of breast is realized with two tangential opposite beams, which usually are mirror beams, or in other words, the internal and external beam angles create an angle of 180˚{α + β = 180˚}. This is a simple method, which provides a good dose distribution, but leaves a relatively high dose in the organs at risk. This study shows the difference in the dose percentage in the heart and lung when the beam angles are changed adapting to the anatomy of the patient. Reducing these doses allows for better overall treatment and less longtime toxicity, particularly for the heart tissues.展开更多
<strong>Aims:</strong> Research the possibility of using IMRT for rectal cancer patients in preoperative radiotherapy. <strong>Methods and Material:</strong> The research object is the preopera...<strong>Aims:</strong> Research the possibility of using IMRT for rectal cancer patients in preoperative radiotherapy. <strong>Methods and Material:</strong> The research object is the preoperative radiotherapy plan for rectal cancer patients. The research group made two plans (IMRT, 3DCRT) for each image series of 34 rectal cancer patients who have received preoperative radiotherapy in Hanoi Oncology Hospital;and then compared the dose distribution on PTV, bladder, intestine, femoral bones, the average MU, and QA results of two types of plan. <strong>Results:</strong> The 95% isodose line and 50% isodose of IMRT plan are closer than those of 3DCRT plan. The average dose of PTV in IMRT plan and 3DCRT plan are 5006 ± 23 cGy and 5036 ± 42 cGy, respectively. The HTCI and HI values of IMRT and 3D plan are 0.97 ± 0.026 and 5.37 ± 1.32;1.00 ± 0.003 and 7.08 ± 0.88. About the dose of organ at risk: The maximum dose, average dose on the right, left femoral head in the IMRT plan are less than those values in the 3DCRT plan (6.2 Gy, 6 Gy, 7.4 Gy, 9 Gy, respectively). The maximum dose and average dose on the bladder of the IMRT plan are smaller than those values of the 3DCRT plan (5.3 Gy, 1.5 times, respectively). The maximum dose and average dose of intestine in the IMRT plan was less than those values in the 3DCRT plan (4.3 Gy, 1.54 times, respectively). The MU number of IMRT plan is 1.5 times bigger than that of 3DCRT plan. Gamma index of IMRT plan is better than that of 3DCRT plan (99% compared with 97%). <strong>Conclusions:</strong> Using IMRT plan in preoperative radiotherapy for rectal cancer patients can still ensure covered PTV as well as the 3D PLAN. Furthermore, the dose of PTV in the IMRT plan is more uniform than those in the 3D plan, and the dose effect on the OAR surrounding PTV is much lower than when using the 3D plan. When IMRT plan were used to treat the preoperative rectal cancer patients, the LINAC took more time than when using 3DCRT plan.展开更多
Purpose: Both physical and virtual wedges are used in radiotherapy to get uniform and desired dose distribution in clinical setting. All linear accelerators of different venders have computer controlled dynamic wedges...Purpose: Both physical and virtual wedges are used in radiotherapy to get uniform and desired dose distribution in clinical setting. All linear accelerators of different venders have computer controlled dynamic wedges called virtual wedge filters. Penumbra is one of the important photon beam characteristics needed to be understood in radiation therapy at the time of commissioning of Treatment Planning system (TPS) as well as applying various treatment planning algorithms in clinical applications. In this study we measured the dose profiles of open field, physical wedges (PW) and virtual wedges (VW) for energies (6 MV & 15 MV), various field sizes (10 × 10, 15 × 15 & 20 × 20 cm2), depths (dmax, 10 cm, 20 cm) and wedge angles (15°, 30°, 45° and 60°). From beam profile we calculated the penumbral width for open and wedged fields. The study was carried out on Siemens ONCOR IMRT Plus linear accelerator. The obtained penumbral width of PW and VW of all wedge angles was subtracted from the penumbral width of open field. The deviations in penumbral width were compared and statistically analyzed as a function of energy, depth, field size and wedge angles. Material and Method: The penumbral width was measured using IBA CC13 ion chamber in IBA Blue phantom (a 3D water phantom). The source to surface distance (SSD) during our study was kept 100cm and measurement was taken for 10 × 10, 15 × 15, 20 × 20 cm2 field sizes and for 15°, 30°, 45°, 60° wedges. These measurements were taken for both 6 MV and 15 MV photon energies. Virtual wedge profiles were acquired using LDA-99 linear detector array (IBA, Germany). The deviations in penumbral width for both PW and VW were calculated by subtracting the penumbral width from open field penumbral width in gun direction (in-plane) and deviation in VW penumbral width, and were obtained by subtracting the open field penumbral width in left-right direction (cross-plane) direction. The measured deviations were plotted for both PW and VW. Statistics on the measured deviations was performed by using SPSS Version 15. Results & Conclusion: The results of one way ANOVA (Analysis of Variance) show that the deviations are significant with energy and the deviations are higher in lower energy than higher energy. The deviations increase as depth increases, the deviations are also significant with depth. The deviations increase with field sizes;the deviations as a function of field size are highly significant. The deviations are higher in PW than VW but the deviations with wedge type are in-significant. As wedge angle increases, deviations also increase and the effect of wedge angle is highly significant on deviations.展开更多
Objective: The aim of this study was to evaluate the functional characteristics of ArcCheck? array detectors and the application for Tomotherapy IMRT plan verification. Method and Materials: The basic character of the...Objective: The aim of this study was to evaluate the functional characteristics of ArcCheck? array detectors and the application for Tomotherapy IMRT plan verification. Method and Materials: The basic character of the ArcCheck applying on Tomotherapy system was tested. The diode testing procedures included the followings: The short term reproducibility, linearity, dose rate dependence, the profile measurement compared to ion chamber. The effect of insert on gamma passing rate was also studied. A total number of 602 Tomotherapy Delivery Quality Assurance (DQA) plans were retrospectively analyzed to obtain the action limit results with statistical significance evaluation. Results: The short term reproducibility, linearity, dose rate dependence, profile to ion chamber correlation and clinical application were all compared with satisfactory outcome with this device. If anterior diode points were properly calibrated with machine absolute output, then there was no significant difference between the ArcCheck phantom with and without insert on gamma passing rate. The average passing rate was 97.5% and the recommend action level was established at 92% based on the 602 patients’ clinical data with 95% confidence level criteria. Conclusion: This comprehensive study shows that ArcCheck is an accurate and efficient device for quality assurance of Tomotherapy with remarkable consistency of 3D volume analysis of arc therapy.展开更多
Purpose: The CyberKnife system equipped with multileaf collimator (MLC) has been shown promising in treatment-time reduction and plan-quality improvement, because of the enhanced coverage of larger lesions and the imp...Purpose: The CyberKnife system equipped with multileaf collimator (MLC) has been shown promising in treatment-time reduction and plan-quality improvement, because of the enhanced coverage of larger lesions and the improved target conformity. In this study, we aim to develop an efficient non-coplanar beam selection program for CyberKnife-based IMRT. Method: The candidate beam set in this study consists of 94 non-coplanar beams, each defined by a vector connecting a CyberKnife node and a target point. Our goal is to choose an adequately small number of beams that will allow the generation of high quality IMRT plans. We use the beam coverage of patient-surface as a surrogate for the solution space of beamlet-based inverse planning. Based on body-surface coverage and beam-projection overlap on the surface, a beam-selection program was developed. To evaluate the effectiveness of the beam selection method, IMRT plans with the selected beams for different treatment sites were generated using the Varian Eclipse treatment planning system and compared with the IMRT plans with conventional coplanar beams. Results: Our program efficiently selected a subset of relatively small number of non-coplanar beams, while pre-serving the body-surface coverage and therefore the solution space for inverse planning optimization. For example, a set of 17 beams were selected for a pancreatic cancer case, covering 92.5% of the surface area which was covered by all the 94 candidate beams with the same field size. The IMRT plans with the selected beams show superior quality with dramatically improved critical structure sparing, as compared with the clinically approved IMRT plans. Conclusion: One can efficiently select effective sets of non-coplanar beams with our program, which allow the generation of high-quality plans for MLC-based robotic radiotherapy.展开更多
Medical linac based imaging modalities such as portal imaging can be utilized for highly accurate measurements. An intensity-weighted centroid method for determining object center is proposed that can detect the posit...Medical linac based imaging modalities such as portal imaging can be utilized for highly accurate measurements. An intensity-weighted centroid method for determining object center is proposed that can detect the position of small object at subpixel accuracy. The principles and algorithms of the intensity-weighted centroid method are presented. Analytical results are derived for positional accuracy of a rod and a sphere in digital images, and the theoretical accuracy limits are calculated. The method was experimentally examined using phantoms with embedded ball bearings (BBs). Images of the phantoms were taken by the MV portal imager of a medical linac. The image pixel size was 0.26 mm when projected at the linac isocenter plane. The BB coordinates were calculated by applying the intensity-weighted centroid method after removing the background. The reproducibility of BB position detection was measured with 3 monitor unit (MU) exposures at various dose rates. A stationary BB, of 0.25 image contrast, showed position reproducibility in the range of 0.004 - 0.013 mm. When the method was used to measure the displacement of a moving BB, the difference between the measured and expected BB position had a standard deviation of 0.006 mm. The effect of image noise on the BB detection accuracy was measured using a phantom with multiple BBs. The overall detection accuracy, represented by standard deviation, steadily improved from 0.13 mm at 0.03 MU to 0.008 mm at 5.0 MU, and showed an inverse correlation with contrast-to-noise ratio. We demonstrated that intensity-weighted centroid method can achieve subpixel accuracy in position detection. With a linac based imaging system, precise mechanical measurement with accuracy of microns could be achieved.展开更多
Significant advancement in thin-film cadmium telluride (CdTe) deposition techniques in recent years has made this material attractive for the development of low-cost large area detector. Here we evaluate the intrinsic...Significant advancement in thin-film cadmium telluride (CdTe) deposition techniques in recent years has made this material attractive for the development of low-cost large area detector. Here we evaluate the intrinsic performance of the detector for a range of energies relevant to diagnostic imaging applications, such as fluoroscopy. The input x-ray spectra for a set of tube potentials ranging from 70 to 140 kVp were computed with the tungsten anode spectral model using interpolating polynomials (TASMIP) based on the measured output of our diagnostic x-ray simulator. Frequency-dependent detector performance analysis was conducted through Monte Carlo simulations of energy deposition within the detector. Intrinsic modulation transfer functions (MTF), noise power spectra (NPS), and detective quantum efficiencies (DQE) were computed for a set of CdTe detectors of varying thickness, from 100 to 1000 μm. MTF behavior at higher frequencies was affected by thickness and input energy, NPS increased with film thickness and energy, and the resultant DQE(f) decreased with increasing the input energy, but increased with the thickness of the detector. We found that the optimal thickness of CdTe under diagnostic x-ray beam is in the range of 300 to 600 μm. Physical properties of CdTe, such as the high atomic number and density, used in direct detection configuration, together with the recently established thin-film manufacturing techniques makes this technology a promising photoconductor for large area diagnostic flat panel imaging.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;">The purpose of this study was to evaluate a planning strategy based on Acuros with density override in comparison wi...<div style="text-align:justify;"> <span style="font-family:Verdana;">The purpose of this study was to evaluate a planning strategy based on Acuros with density override in comparison with AAA without and with the override. Ten lung-tumor patients were selected with each PTV size around 2 - 4 cm and were imaged using slow scan, followed by four-dimensional (4D) imag</span><span style="font-family:Verdana;">ing limited to the target. On each phase-specific image, gross tumor </span><span style="font-family:Verdana;">volume (GTV) was contoured. Summed over all phases, an integrated GTV (iGTV) was generated and copied to the slow scan. A treatment plan was created using a dynamic-conformal-arc technique with AAA to prescribe 60 Gy to 95% of PTV (iGTV + 0.5 cm). Each AAA-based plan was regenerated by overriding the density of the setup margin of PTV by GTV density (modeling tumor-position uncertainty). It was also regenerated with Acuros and the override. The three plans were validated in 4D dose to PTV, after similarly overriding PTV density (phase-specific), accurately calculating with Acuros, and summing the phase-specific plans through organ/dose registration. The Acuros-based plan with the override, the AAA-based plan, and the AAA-based plan with the override provided 4D PTV doses of 63.9, 67.9, and 62 Gy at D95%, respectively, averaged over all patients. The override with Acuros and AAA produced lesser 4D doses, closer to the associated 3D doses, respectively, than that without the override, with better conformity and inhomogeneity. With the override in common, Acuros provided a greater dose to PTV than that by AAA. The Acuros with the override, which was more accurate than the AAA without the override, is clinically recommended.</span> </div>展开更多
Purpose: To explore the effect of rhIL-12 on the number of the blood cells and CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells in liver cancer patients following radiation therapy. Methods: We selected forty liver canc...Purpose: To explore the effect of rhIL-12 on the number of the blood cells and CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells in liver cancer patients following radiation therapy. Methods: We selected forty liver cancer patients who carried out by cyber knife (the patients were given 5 Gy every time for 5 times continuously) to observe the size of the tumor. After thirty hours, rhIL-12 was injected into the liver cancer patients via subcutaneous at the concentration of 50 ng/kg, 100 ng/kg, 200 ng/kg and 300 ng/kg in different patients, respectively. And there were ten patients in the four groups, respectively. The twenty patients who were selected from the hospital without rhIL-12 treatment were used as controls. All the blood cells were collected from different groups on day 0, hour 12, day 7, day 14, day 21 and day 28 after rhIL-12 treatment, respectively. The full number of blood cells in every group was analyzed by ELISA. The number of CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells were detected by Flow Cytometry. After one month with rhIL-12 treatment, ECOG and WHO were used to evaluate the prognosis of liver cancer. Results: In present study, we found that the number of blood cells was significantly decreased on day 0 - day 3, while recovered from day 7 - day 14 and down-regulated on day 21 after rhIL-12 treatment. The number of CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells was elevated with any concentration of rhIL-12. Furthermore, results showed that number of white blood cells was obviously higher than in patients without rhIL-12 treatment (P < 0.05). However, there was no significant difference of erythrocyte and platelet, between groups treated with rhIL-12 and control groups. In addition, the immune cells including CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells were reduced on day 0 - day 3, recovered from day 7, and then decreased from day 21 in rhIL-12 treatment groups related to control groups (P < 0.05). Furthermore, studies showed that five patients developed symptoms of fever, bilirubin increased and liver dysfunction with the dose of 300 ng/kg. So we found that the safe and well-tolerated human dose of 200 ng/kg is within this efficacious range based on exposure parameters through the research. Higher ECOG and WHO scores were observed in rhIL-12 treatment groups compared to control groups (P = 0.025, P = 0.044, respectively). Conclusion: Our results suggested that rhIL-12 could recover the liver cancer induced aberrant blood cell number and CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells , which may be an effective method to alleviate the progress of liver cancer and played an important role in treating liver cancer.展开更多
Dose in radiation therapy has been reported as the water-equivalent dose using conventional dose calculation algorithms. The Monte Carlo (MC) algorithm employs characterization of human tissues by elemental compositio...Dose in radiation therapy has been reported as the water-equivalent dose using conventional dose calculation algorithms. The Monte Carlo (MC) algorithm employs characterization of human tissues by elemental composition and mass density. It enables more accurate dose calculation for radiation therapy treatment planning and typically reports absorbed dose to medium. Whether one should use dose to medium or tissue (Dm) in place of dose to water (Dw) for MC treatment planning remains the subject of debate. The aim of the current study is to evaluate the differences between dose-volume indices for Dm and Dw MC-calculated IMRT plans. Thirty-seven spine patients were selected for this study. The IMRT optimization and MC calculations were performed using the iPlan RT DoseTM ver 4.1.2 (Brainlab, Munich, Germany) treatment planning system (TPS) with an X-ray Voxel Monte Carlo (XVMC) dose calculation engine. Dw and Dm results for target and critical structures were evaluated using the dose-volume-based indices. Systematic differences between dose-volume indices computed with Dw and Dm were up to 5.2%, 4.2%, and 4.5% for D2, D50 and D98 indices of the clinical target volume (CTV), respectively and up to 1% for the critical structure dose indices. Our study demonstrates that employing Dm in place of Dw in MC-calculated IMRT treatment plans introduces a significant systematic difference in target DVHs. We recommend that for diffused target structures (such as spine tumors), dose to water is a better quantity for dose prescription in photon beam treatment planning using existing MC TPS. While for critical structures, it would be reasonable to report Dm always. However in future with the availability of finer spatial resolution, Dm will be the most suitable variable for both target and critical structures’ dose prescription and reporting in MC treatment planning.展开更多
Cone-beam CT (CBCT) images acquired during radiation treatment can be used to recalculate the dose distribution as well as to confirm the treatment location. However, it is difficult to obtain the electron densities (...Cone-beam CT (CBCT) images acquired during radiation treatment can be used to recalculate the dose distribution as well as to confirm the treatment location. However, it is difficult to obtain the electron densities (EDs) necessary for dose calculation from CBCT images because of the effects of scatter contamination during CBCT image acquisition. This paper presents a mathematical method for converting the pixel values of CBCT images (CBCT values) into Hounsfield units (HUs) of radiation treatment simulation CT (simCT) images for use in radiation treatment planning. CBCT values are converted into HUs by matching the histograms of the CBCT values with the histograms of the HUs for each slice via linear scaling of the CBCT values. For prostate cancer and head-and-neck cancer patients, the EDs obtained from converted CBCT values (mCBCT values) show good agreement with the EDs obtained from HUs, within approximately 3.0%, and the dose calculated on the basis of CBCT images shows good agreement with the dose calculated on the basis of the simCT images, within approximately 2.0%. Because the CBCT values are converted for each slice, this conversion method can account for variation in the CBCT values associated with differences in body size, body shape, and inner tissue structures, as well as in longitudinally displaced positions from the isocenter, unlike conventional methods that use electron density phantoms. This method improves on conventional CBCT-ED conversion and shows considerable potential for improving the accuracy of radiation treatment planning using CBCT images.展开更多
The majority of EPID dosimetry literature discusses response linearity and the so-called image lag and ghosting effects despite the lack of a common definition of these quantities. However, the results of these studie...The majority of EPID dosimetry literature discusses response linearity and the so-called image lag and ghosting effects despite the lack of a common definition of these quantities. However, the results of these studies are generally not consistent, and it is often difficult to compare the results from different studies. We present here a detailed study of the acquisition and readout characteristics of a-Si EPID and its dosimetric performance. EPID response was assessed over the range of 1 - 500 MU using different dose rates and integration times. In addition, a computer model was designed to simulate the EPID image formation with different dose, dose rate, and integration time combinations. All aspects of image processing and readout simulation were carried out using custom written MatLab codes. Two distinct signal profiles were observed depending on the delivered dose, dose rate and integration time combination. Total integrated signal (S<sub>T</sub>) is linear with the delivered dose. For dosimetry, image lag and ghosting effects mainly result in the residual signal (S<sub>R</sub>) that appears as delayed signal after the end of irradiation. At its maximum, S<sub>R</sub> is less than 2.5% of S<sub>T</sub>. The readout technique is such that it is impossible to measure S<sub>R</sub> accurately. S<sub>R</sub> is definable only when readout equilibrium occurs. Signal profiles provide a through and reliable description of the EPID response incorporating the dose, dose rate, integration time, and the residual signal. The definition of EPID signals based on this method shall provide an accurate universal EPID dosimetry framework.展开更多
The objective of this study is to investigate the dose perturbations introduced by the implanted gold fiducial markers in the prostate cancer intensity modulated proton therapy (IMPT) and the impacts of different plan...The objective of this study is to investigate the dose perturbations introduced by the implanted gold fiducial markers in the prostate cancer intensity modulated proton therapy (IMPT) and the impacts of different plan designs on the pertur-bations. Five proton plans: a single lateral field 3D-modulation (3D-mod) plan, 2 fields laterally opposing 3D-mod plan, 6-, 9-, and 18-field distal edge tracking (DET) plans were designed on the CT images of a prostate patient. The dose distributions were first generated for the plans free of fiducial markers with 78 Gy prescribed to 95% of the PTV. To derive the dose perturbations of the gold fiducial markers, three cylindrical shaped gold fiducial markers (3 mm long and 1 mm in diameter) were artificially inserted into the prostate, and the dose distributions were re-computed. Monte Carlo method was used for dose computation. It was found that the gold fiducial markers perturbed the dose distribu-tions, especially along the beam paths. The markers caused a shadowing effect reducing the doses in the areas beyond the markers. Overall, due to the presence of the fiducial markers, D99% of prostate were reduced by 2.96 Gy, 4.21 Gy, 0.16 Gy, 0.34 Gy, 0.15 Gy for the plans of single field 3D-mod, 2-field parallel opposed 3D-mod, 6-, 9-, and 18-field DET respectively. Our study showed these dose perturbation effects decreased with the increase of number of beam angles. Up to 6 beam angles may be required to reduce the dose perturbations from the gold fiducial markers to a clini- cally acceptable level in IMPT.展开更多
Purpose: To test the concept of Statistical Process Control (SPC) as a Quality Assurance (QA) procedure for dose verifications in external beam radiation therapy in conventional and 3D Conformal Radiotherapy (3D-CRT) ...Purpose: To test the concept of Statistical Process Control (SPC) as a Quality Assurance (QA) procedure for dose verifications in external beam radiation therapy in conventional and 3D Conformal Radiotherapy (3D-CRT) treatment of cervical cancer. Materials and Methods: A study of QA verification of target doses of 198 cervical cancer patients undergoing External Beam Radiotherapy (EBRT) treatments at two different cancer treatment centers in Kenya was conducted. The target doses were determined from measured entrance doses by the diode in vivo dosimetry. Process Behavior Charts (PBC) developed by SPC were applied for setting Action Thresholds (AT) on the target doses. The AT set was then proposed as QA limits for acceptance or rejection of verified target doses overtime of the EBRT process. Result and Discussion: Target doses for the 198 patients were calculated and SPC applied to test whether the action limits set by the Process Behavior Charts could be applied as QA for verified doses in EBRT. Results for the two sub-groups of n = 3 and n = 4 that were tested produced action thresholds which are within clinical dose specifications for both conventional AP/PA and 3D-CRT EBRT treatment techniques for cervical cancer. Conclusion: Action thresholds set by SPC were within the clinical dose specification of ±5% uncertainty for both conventional AP/PA and 3D-CRT EBRT treatment techniques for cervical cancer. So the concept of SPC could be applied in setting QA action limits for dose verifications in EBRT.展开更多
The Halcyon O-ring gantry linear accelerator from Varian Medical Systems is delivered with a hardcoded beam-source model and Analytical Anisotropic Algorithm dose calculation algorithm as standard, while the Acuros XB...The Halcyon O-ring gantry linear accelerator from Varian Medical Systems is delivered with a hardcoded beam-source model and Analytical Anisotropic Algorithm dose calculation algorithm as standard, while the Acuros XB algorithm is a purchasable option. The models in both algorithms are factory-configured and do not permit fine-tuning by the user. In this study, we compared the two algorithms for sequential boost RapidArc treatment planning of Head & Neck cancers using D98%, D95%, D50%, D2% and maximum dose to assess dose coverage of nodal and tumor planning target volumes (PTV_N and PTV_T, respectively), and cochlear D5%, parotid D20%, D50%, mean dose, and cord maximum dose to evaluate doses to organs- at-risk. The conformity index (CI), homogeneity index (HI) and total number of monitor units (MU) quantified plan quality. We found statistically significant differences in PTV_N D2%, maximum dose, HI, PTV_T D98%, D95%, D2%, Max, HI, and total MU. Statistically significant differences in Cochlear D5% and Parotid mean doses were also encountered. These differences may not necessarily be clinically significant, however. Therefore, we believe that both calculation algorithms are adequate for RapidArc planning of Head & Neck cancers.展开更多
In the linear accelerator-based stereotactic radio surgery (SRS) and stereotactic body radiotherapy (SBRT) programs, single isocenter-multiple metastases’ treatment has become more and more popular due to their high ...In the linear accelerator-based stereotactic radio surgery (SRS) and stereotactic body radiotherapy (SBRT) programs, single isocenter-multiple metastases’ treatment has become more and more popular due to their high efficiency in treatment time. However, the absence of a comprehensive quality assurance program is still the challenge for medical physicists. The Winston-Lutz-Gao test, which we developed two years ago, was performed for the first time on a True Beam STx (Varian Medical System) linear accelerator in this study. Beams were designed by Eclipse with gantry, collimator, and couch full rotations, and a 200-pound weight was placed on the couch to mimic real treatment. The “frameless SRS QA target pointer” from the Brainlab company, with a 3.5-mm metallic ball embedded in the center, was used as a phantom. Images were acquired by the portal imager built-in linear accelerator and analyzed directly by the Image browser in ARIA. We found that the farther the metastases were from the linac isocenter, the worse the congruence was between the beam mechanical and the radiation center. The farthest metastases should be within 6 cm from the linac isocenter per the AAPM TG-142 and American Society for Radiation Oncology (ASTRO) white paper criteria. To the best of our knowledge, this is the first off-isocenter Winston-Lutz test performed on a True Beam STx linear accelerator.展开更多
In the present work, a treatment technique for trigeminal neuralgia (TN) using LINAC radiosurgery is shown. The technique is based on the optimization of ten static arcs in such a way as to minimize the overlapping of...In the present work, a treatment technique for trigeminal neuralgia (TN) using LINAC radiosurgery is shown. The technique is based on the optimization of ten static arcs in such a way as to minimize the overlapping of the treatment fields with the brainstem. We will call this technique brainstem-optimized (BO). The results are compared with another technique described in the literature known as a virtual cone (VC). The comparison of dosimetry results that have been carried out essentially shows that the doses in the brainstem V12Gy-brainstem, D0.5cm<sup>3</sup>-brainstem and D0.035 cm<sup>3</sup>-brainstem are lower in the BO versus VC technique, and with the parameters V50% (whole brain) and V12Gy-cerebrum higher in BO versus VC. Our goal is to keep the dose to the brainstem as low as possible and, if possible, at most between 12 Gy and 15 Gy. The BO technique meets our purposes and is considered clinically acceptable at our institution.展开更多
Polymer gels are three-dimensional dosimetric tools. The purpose of the present study was to investigate the temperature dependence of polymer gels during scanning Magnetic Resonance Imaging. Prepared gels were irradi...Polymer gels are three-dimensional dosimetric tools. The purpose of the present study was to investigate the temperature dependence of polymer gels during scanning Magnetic Resonance Imaging. Prepared gels were irradiated with a 6MV X-ray beam at intensities ranging from 0 to 20 Gy in order to investigate their dose-R2 and dose-R1 responses. Irradiated gels were evaluated from 1.5-T magnetic resonance R2 and R1 images for each 5°C change in temperature from 5°C to 41°C, and then the four-field box technique irradiation plan was used to deliver a total dose of 4 Gy using the same beam weight in each direction to the prepared gels. The profile of the dose map generated from the four-field irradiated gel data at 20°C was then compared with the planned data. The dose-R2 response curve was linear up to 20 Gy at 20°C, with a slope of 1.17 Gy-1˙s-1. The slopes of the fitted curves of the dose-R2 decreased as gel temperature increased. The slopes of the dose-R1 curves were more parallel than the slopes of the dose-R2 curves between 5 and 41°C. The difference in the full width of half maximum of the gel profile data obtained using the four-field box technique at 20°C and the planned data were below 5% on average. The dose map from the irradiated gels obtained using the dose-R2 curve was the same as that from the planned data under the same temperature conditions. Measurement of difference between various temperatures is significant with dose accuracy. It is suitable to evaluate the gel dosimeter under the thermal equilibrium condition, MRI room temperature from the point of view of the stability of the irradiated gels.展开更多
Aim: Dosimetric analysis of three different Radiotherapy techniques in patients with Breast Cancer and their impact on OAR’s. Materials and Methods: 12 patients of Carcinoma Breast who received breast radiotherapy we...Aim: Dosimetric analysis of three different Radiotherapy techniques in patients with Breast Cancer and their impact on OAR’s. Materials and Methods: 12 patients of Carcinoma Breast who received breast radiotherapy were selected for analysis. Computed tomography (CT) simulation image data sets were retrieved. Planning target Volume (PTV), heart and ipsilateral lung were contoured for planning and analysis of doses. Three different plans using conventional bi-tangential fields were prepared, Plan 1 with SAD full beam with wedge (SAD-FBW), Plan 2 with SSD half beam with wedge (SSD-HBW) and plan 3 with SSD half beam without wedge techniques (SSD-HBO) in CMS Xio TPS. Statistical analysis was done using SPSS version 16.0. Results: The PTV coverage was significantly better in SAD-FBW techniques when compared with the other two techniques i.e. SSD-HBW (mean = 92.33, SD = 4.69, p = 0.005) and SSD-HBO (mean = 75.05, SD = 11.92, p = 0.002). The mean heart doses were significantly better in SAD-FBW compared to SSD-HBW (mean = 3.75, SD = 2.27, p = 0.017) but in SSD-HBO technique mean heart doses were better than SAD-FBW technique (mean = 3.27, SD = 1.94, p = 0.004). Similarly, the left lung V20 values were significantly better in SSD-HBO technique than SAD-FBW technique (mean = 11.75, SD = 4.34, p = 0.004) but there was statistically insignificant difference between the SAD-FBW and SSD-HBW techniques. The treatment monitor units were significantly less in SAD-FBW compared to SSD-HBW but SSD-HBO has less MU compared to SAD-FBW technique. Conclusion: SAD Full Beam with wedge technique is practically better than SSD Half Beam technique with or without wedge without compromising PTV coverage considering other dosimetric parameters. We also recommend that centers treating patient with half beam SSD techniques should shift immediately to SAD techniques.展开更多
Objective: To investigate better dosimetric distribution of volumetric modulated arc therapy (VMAT) vs. 5F intensity modulated radiotherapy (IMRT) and 3D conformal radiotherapy (3DCRT) in patients with locally advance...Objective: To investigate better dosimetric distribution of volumetric modulated arc therapy (VMAT) vs. 5F intensity modulated radiotherapy (IMRT) and 3D conformal radiotherapy (3DCRT) in patients with locally advanced rectal cancer (LARC) when treated with neoadjuvant chemoradiotherapy. Methods: 3D-CRT, 5F-IMRT and VMAT plans for preoperative radiotherapy were 66011designed in 12 patients with locally advanced rectal cancer. The conformity index (CI) and homogeneity index (HI) in target volume, and the dose and volume of the organs at risk (OAR) irradiated including small bowel, bladder and bilatera1 femoral heads were compared among the three plans. Results: The CI for planning target volume (PTV) 2 and HI for PTV1 of VMRT and 5F-IMRT were superior to 3D-CRT. The CI of VMAT, 5F-IMRT and 3D-CRT plans were 0.71, 0.69 and 0.62 (p = 0.011 and p = 0.019, respectively). The HI of the VMAT and 5F-IMRT plans were both 1.04 and 3D-CRT planning was 1.06 (p = 0.022 and p = 0.006, respectively). The V35 - V45 of small bowel in VMAT were significantly less than in 5F-IMRT and 3D-CRT. V35 was 47.0, 56.4, and 72.8 cm3 for VMAT, 5F-IMRT, and 3D-CRT (p = 0.021 and p = 0.034, respectively), while V40 was 30.5, 35.5, 45.1 cm3 (p = 0.024 and p = 0.032, respectively) and V45 was 15.1, 18.1, 30.0 cm3 (p = 0.033 and p = 0.032, respectively). The D5, V30 and V50 of bladder in 3D-CRT were less than in VMAT and 5F-IMRT planning (p = 0.034, 0.004, 0.002 and p = 0.027, 0.003, 0.002, respectively). The Dmean of left femoral head in VMAT and 5F-IMRT were less than in 3D-CRT planning (p = 0.028 and p = 0.022, respectively) and the Dmean, V30 of right femoral head in VMAT and 5F-IMRT were better than in 3D-CRT planning (p = 0.044, 0.036 and p = 0.023, 0.028, respectively). Conclusions: Dosimetric analyses demonstrated that IMRT is superior to 3D-CRT in the conformity and homogeneity of dose distribution to the target volume, and provide a better protection to OARs sparing in patients with locally advanced rectal cancer for preoperative radiotherapy. With similar target coverage, VMRT is superior to 5F-IMRT in normal tissue sparing.展开更多
文摘Introduction: Breast cancer is the most common cancer in women. The treatment of breast carcinoma has advanced in the last decade and nowadays there are treatment protocols for all stages of the disease. Depending on the histopathology and stage breast cancer is treated with surgery, chemotherapy and radiotherapy. Regarding radiation, the field of irradiation includes the chest wall in patients with mastectomy, or the breast glandular tissue in patients with conserving surgical approaches. It is often treated with radiation therapy with two opposing tangential fields, and when indicated supraclavicular lymph nodes have to be irradiated. In this case an additional anterior field is applied. The tangential as well as the other radiation beams have a potential damaging effect on the healthy surrounding tissues, particularly over the heart in the left breast irradiation and in the lungs as well. Material and Methods: The study included 25 patients with left breast carcinoma, all post surgery, treated with radiation therapy, with the Elekta accelerator at our department. For academic purpose the treatment plans were generated following two methods. The first one with two tangential opposite beams plus a supraclavicular beam. In this method the angles of the tangential internal and external create an angle that is equal to 180˚{310˚& 130˚};no further changes were made to the beam geometry. Even though this is not the best option from the dose distribution point of view, it is still the most applied method, probably because of the semplicity of it. For each patient, a second plan was generated using two opposite tangential beams plus the supraclavicular beam. The angles of the internal and external beam were changed from 1˚to 3˚, depending on the surface of the body, so that the resulting angle was 180˚± 3˚{310˚± 3˚& 130˚± 3˚} with the aim to adapt the beam geometry as much as possible to the shape of the thoracic wall and to spare the OAR-s. Results and Discussion: The data show that the dose in the organs at risk, in terms of dose percentage, is lower when the angles of the beams are changed with 1˚- 3˚, compared to the classic method where the internal and external angles equal 180˚. This dose is not only non-negligible but significant;for every angle change from 1˚to 3˚, there is a significant reduction in the integral dose in the radiated volume, expressed in percentage, up to 5%. Conclusion: In most centers, the radiation treatment of breast is realized with two tangential opposite beams, which usually are mirror beams, or in other words, the internal and external beam angles create an angle of 180˚{α + β = 180˚}. This is a simple method, which provides a good dose distribution, but leaves a relatively high dose in the organs at risk. This study shows the difference in the dose percentage in the heart and lung when the beam angles are changed adapting to the anatomy of the patient. Reducing these doses allows for better overall treatment and less longtime toxicity, particularly for the heart tissues.
文摘<strong>Aims:</strong> Research the possibility of using IMRT for rectal cancer patients in preoperative radiotherapy. <strong>Methods and Material:</strong> The research object is the preoperative radiotherapy plan for rectal cancer patients. The research group made two plans (IMRT, 3DCRT) for each image series of 34 rectal cancer patients who have received preoperative radiotherapy in Hanoi Oncology Hospital;and then compared the dose distribution on PTV, bladder, intestine, femoral bones, the average MU, and QA results of two types of plan. <strong>Results:</strong> The 95% isodose line and 50% isodose of IMRT plan are closer than those of 3DCRT plan. The average dose of PTV in IMRT plan and 3DCRT plan are 5006 ± 23 cGy and 5036 ± 42 cGy, respectively. The HTCI and HI values of IMRT and 3D plan are 0.97 ± 0.026 and 5.37 ± 1.32;1.00 ± 0.003 and 7.08 ± 0.88. About the dose of organ at risk: The maximum dose, average dose on the right, left femoral head in the IMRT plan are less than those values in the 3DCRT plan (6.2 Gy, 6 Gy, 7.4 Gy, 9 Gy, respectively). The maximum dose and average dose on the bladder of the IMRT plan are smaller than those values of the 3DCRT plan (5.3 Gy, 1.5 times, respectively). The maximum dose and average dose of intestine in the IMRT plan was less than those values in the 3DCRT plan (4.3 Gy, 1.54 times, respectively). The MU number of IMRT plan is 1.5 times bigger than that of 3DCRT plan. Gamma index of IMRT plan is better than that of 3DCRT plan (99% compared with 97%). <strong>Conclusions:</strong> Using IMRT plan in preoperative radiotherapy for rectal cancer patients can still ensure covered PTV as well as the 3D PLAN. Furthermore, the dose of PTV in the IMRT plan is more uniform than those in the 3D plan, and the dose effect on the OAR surrounding PTV is much lower than when using the 3D plan. When IMRT plan were used to treat the preoperative rectal cancer patients, the LINAC took more time than when using 3DCRT plan.
文摘Purpose: Both physical and virtual wedges are used in radiotherapy to get uniform and desired dose distribution in clinical setting. All linear accelerators of different venders have computer controlled dynamic wedges called virtual wedge filters. Penumbra is one of the important photon beam characteristics needed to be understood in radiation therapy at the time of commissioning of Treatment Planning system (TPS) as well as applying various treatment planning algorithms in clinical applications. In this study we measured the dose profiles of open field, physical wedges (PW) and virtual wedges (VW) for energies (6 MV & 15 MV), various field sizes (10 × 10, 15 × 15 & 20 × 20 cm2), depths (dmax, 10 cm, 20 cm) and wedge angles (15°, 30°, 45° and 60°). From beam profile we calculated the penumbral width for open and wedged fields. The study was carried out on Siemens ONCOR IMRT Plus linear accelerator. The obtained penumbral width of PW and VW of all wedge angles was subtracted from the penumbral width of open field. The deviations in penumbral width were compared and statistically analyzed as a function of energy, depth, field size and wedge angles. Material and Method: The penumbral width was measured using IBA CC13 ion chamber in IBA Blue phantom (a 3D water phantom). The source to surface distance (SSD) during our study was kept 100cm and measurement was taken for 10 × 10, 15 × 15, 20 × 20 cm2 field sizes and for 15°, 30°, 45°, 60° wedges. These measurements were taken for both 6 MV and 15 MV photon energies. Virtual wedge profiles were acquired using LDA-99 linear detector array (IBA, Germany). The deviations in penumbral width for both PW and VW were calculated by subtracting the penumbral width from open field penumbral width in gun direction (in-plane) and deviation in VW penumbral width, and were obtained by subtracting the open field penumbral width in left-right direction (cross-plane) direction. The measured deviations were plotted for both PW and VW. Statistics on the measured deviations was performed by using SPSS Version 15. Results & Conclusion: The results of one way ANOVA (Analysis of Variance) show that the deviations are significant with energy and the deviations are higher in lower energy than higher energy. The deviations increase as depth increases, the deviations are also significant with depth. The deviations increase with field sizes;the deviations as a function of field size are highly significant. The deviations are higher in PW than VW but the deviations with wedge type are in-significant. As wedge angle increases, deviations also increase and the effect of wedge angle is highly significant on deviations.
文摘Objective: The aim of this study was to evaluate the functional characteristics of ArcCheck? array detectors and the application for Tomotherapy IMRT plan verification. Method and Materials: The basic character of the ArcCheck applying on Tomotherapy system was tested. The diode testing procedures included the followings: The short term reproducibility, linearity, dose rate dependence, the profile measurement compared to ion chamber. The effect of insert on gamma passing rate was also studied. A total number of 602 Tomotherapy Delivery Quality Assurance (DQA) plans were retrospectively analyzed to obtain the action limit results with statistical significance evaluation. Results: The short term reproducibility, linearity, dose rate dependence, profile to ion chamber correlation and clinical application were all compared with satisfactory outcome with this device. If anterior diode points were properly calibrated with machine absolute output, then there was no significant difference between the ArcCheck phantom with and without insert on gamma passing rate. The average passing rate was 97.5% and the recommend action level was established at 92% based on the 602 patients’ clinical data with 95% confidence level criteria. Conclusion: This comprehensive study shows that ArcCheck is an accurate and efficient device for quality assurance of Tomotherapy with remarkable consistency of 3D volume analysis of arc therapy.
文摘Purpose: The CyberKnife system equipped with multileaf collimator (MLC) has been shown promising in treatment-time reduction and plan-quality improvement, because of the enhanced coverage of larger lesions and the improved target conformity. In this study, we aim to develop an efficient non-coplanar beam selection program for CyberKnife-based IMRT. Method: The candidate beam set in this study consists of 94 non-coplanar beams, each defined by a vector connecting a CyberKnife node and a target point. Our goal is to choose an adequately small number of beams that will allow the generation of high quality IMRT plans. We use the beam coverage of patient-surface as a surrogate for the solution space of beamlet-based inverse planning. Based on body-surface coverage and beam-projection overlap on the surface, a beam-selection program was developed. To evaluate the effectiveness of the beam selection method, IMRT plans with the selected beams for different treatment sites were generated using the Varian Eclipse treatment planning system and compared with the IMRT plans with conventional coplanar beams. Results: Our program efficiently selected a subset of relatively small number of non-coplanar beams, while pre-serving the body-surface coverage and therefore the solution space for inverse planning optimization. For example, a set of 17 beams were selected for a pancreatic cancer case, covering 92.5% of the surface area which was covered by all the 94 candidate beams with the same field size. The IMRT plans with the selected beams show superior quality with dramatically improved critical structure sparing, as compared with the clinically approved IMRT plans. Conclusion: One can efficiently select effective sets of non-coplanar beams with our program, which allow the generation of high-quality plans for MLC-based robotic radiotherapy.
文摘Medical linac based imaging modalities such as portal imaging can be utilized for highly accurate measurements. An intensity-weighted centroid method for determining object center is proposed that can detect the position of small object at subpixel accuracy. The principles and algorithms of the intensity-weighted centroid method are presented. Analytical results are derived for positional accuracy of a rod and a sphere in digital images, and the theoretical accuracy limits are calculated. The method was experimentally examined using phantoms with embedded ball bearings (BBs). Images of the phantoms were taken by the MV portal imager of a medical linac. The image pixel size was 0.26 mm when projected at the linac isocenter plane. The BB coordinates were calculated by applying the intensity-weighted centroid method after removing the background. The reproducibility of BB position detection was measured with 3 monitor unit (MU) exposures at various dose rates. A stationary BB, of 0.25 image contrast, showed position reproducibility in the range of 0.004 - 0.013 mm. When the method was used to measure the displacement of a moving BB, the difference between the measured and expected BB position had a standard deviation of 0.006 mm. The effect of image noise on the BB detection accuracy was measured using a phantom with multiple BBs. The overall detection accuracy, represented by standard deviation, steadily improved from 0.13 mm at 0.03 MU to 0.008 mm at 5.0 MU, and showed an inverse correlation with contrast-to-noise ratio. We demonstrated that intensity-weighted centroid method can achieve subpixel accuracy in position detection. With a linac based imaging system, precise mechanical measurement with accuracy of microns could be achieved.
文摘Significant advancement in thin-film cadmium telluride (CdTe) deposition techniques in recent years has made this material attractive for the development of low-cost large area detector. Here we evaluate the intrinsic performance of the detector for a range of energies relevant to diagnostic imaging applications, such as fluoroscopy. The input x-ray spectra for a set of tube potentials ranging from 70 to 140 kVp were computed with the tungsten anode spectral model using interpolating polynomials (TASMIP) based on the measured output of our diagnostic x-ray simulator. Frequency-dependent detector performance analysis was conducted through Monte Carlo simulations of energy deposition within the detector. Intrinsic modulation transfer functions (MTF), noise power spectra (NPS), and detective quantum efficiencies (DQE) were computed for a set of CdTe detectors of varying thickness, from 100 to 1000 μm. MTF behavior at higher frequencies was affected by thickness and input energy, NPS increased with film thickness and energy, and the resultant DQE(f) decreased with increasing the input energy, but increased with the thickness of the detector. We found that the optimal thickness of CdTe under diagnostic x-ray beam is in the range of 300 to 600 μm. Physical properties of CdTe, such as the high atomic number and density, used in direct detection configuration, together with the recently established thin-film manufacturing techniques makes this technology a promising photoconductor for large area diagnostic flat panel imaging.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">The purpose of this study was to evaluate a planning strategy based on Acuros with density override in comparison with AAA without and with the override. Ten lung-tumor patients were selected with each PTV size around 2 - 4 cm and were imaged using slow scan, followed by four-dimensional (4D) imag</span><span style="font-family:Verdana;">ing limited to the target. On each phase-specific image, gross tumor </span><span style="font-family:Verdana;">volume (GTV) was contoured. Summed over all phases, an integrated GTV (iGTV) was generated and copied to the slow scan. A treatment plan was created using a dynamic-conformal-arc technique with AAA to prescribe 60 Gy to 95% of PTV (iGTV + 0.5 cm). Each AAA-based plan was regenerated by overriding the density of the setup margin of PTV by GTV density (modeling tumor-position uncertainty). It was also regenerated with Acuros and the override. The three plans were validated in 4D dose to PTV, after similarly overriding PTV density (phase-specific), accurately calculating with Acuros, and summing the phase-specific plans through organ/dose registration. The Acuros-based plan with the override, the AAA-based plan, and the AAA-based plan with the override provided 4D PTV doses of 63.9, 67.9, and 62 Gy at D95%, respectively, averaged over all patients. The override with Acuros and AAA produced lesser 4D doses, closer to the associated 3D doses, respectively, than that without the override, with better conformity and inhomogeneity. With the override in common, Acuros provided a greater dose to PTV than that by AAA. The Acuros with the override, which was more accurate than the AAA without the override, is clinically recommended.</span> </div>
文摘Purpose: To explore the effect of rhIL-12 on the number of the blood cells and CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells in liver cancer patients following radiation therapy. Methods: We selected forty liver cancer patients who carried out by cyber knife (the patients were given 5 Gy every time for 5 times continuously) to observe the size of the tumor. After thirty hours, rhIL-12 was injected into the liver cancer patients via subcutaneous at the concentration of 50 ng/kg, 100 ng/kg, 200 ng/kg and 300 ng/kg in different patients, respectively. And there were ten patients in the four groups, respectively. The twenty patients who were selected from the hospital without rhIL-12 treatment were used as controls. All the blood cells were collected from different groups on day 0, hour 12, day 7, day 14, day 21 and day 28 after rhIL-12 treatment, respectively. The full number of blood cells in every group was analyzed by ELISA. The number of CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells were detected by Flow Cytometry. After one month with rhIL-12 treatment, ECOG and WHO were used to evaluate the prognosis of liver cancer. Results: In present study, we found that the number of blood cells was significantly decreased on day 0 - day 3, while recovered from day 7 - day 14 and down-regulated on day 21 after rhIL-12 treatment. The number of CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells was elevated with any concentration of rhIL-12. Furthermore, results showed that number of white blood cells was obviously higher than in patients without rhIL-12 treatment (P < 0.05). However, there was no significant difference of erythrocyte and platelet, between groups treated with rhIL-12 and control groups. In addition, the immune cells including CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells were reduced on day 0 - day 3, recovered from day 7, and then decreased from day 21 in rhIL-12 treatment groups related to control groups (P < 0.05). Furthermore, studies showed that five patients developed symptoms of fever, bilirubin increased and liver dysfunction with the dose of 300 ng/kg. So we found that the safe and well-tolerated human dose of 200 ng/kg is within this efficacious range based on exposure parameters through the research. Higher ECOG and WHO scores were observed in rhIL-12 treatment groups compared to control groups (P = 0.025, P = 0.044, respectively). Conclusion: Our results suggested that rhIL-12 could recover the liver cancer induced aberrant blood cell number and CD4/8+ T, CD45+ leukocytes, and CD56+ NK cells , which may be an effective method to alleviate the progress of liver cancer and played an important role in treating liver cancer.
文摘Dose in radiation therapy has been reported as the water-equivalent dose using conventional dose calculation algorithms. The Monte Carlo (MC) algorithm employs characterization of human tissues by elemental composition and mass density. It enables more accurate dose calculation for radiation therapy treatment planning and typically reports absorbed dose to medium. Whether one should use dose to medium or tissue (Dm) in place of dose to water (Dw) for MC treatment planning remains the subject of debate. The aim of the current study is to evaluate the differences between dose-volume indices for Dm and Dw MC-calculated IMRT plans. Thirty-seven spine patients were selected for this study. The IMRT optimization and MC calculations were performed using the iPlan RT DoseTM ver 4.1.2 (Brainlab, Munich, Germany) treatment planning system (TPS) with an X-ray Voxel Monte Carlo (XVMC) dose calculation engine. Dw and Dm results for target and critical structures were evaluated using the dose-volume-based indices. Systematic differences between dose-volume indices computed with Dw and Dm were up to 5.2%, 4.2%, and 4.5% for D2, D50 and D98 indices of the clinical target volume (CTV), respectively and up to 1% for the critical structure dose indices. Our study demonstrates that employing Dm in place of Dw in MC-calculated IMRT treatment plans introduces a significant systematic difference in target DVHs. We recommend that for diffused target structures (such as spine tumors), dose to water is a better quantity for dose prescription in photon beam treatment planning using existing MC TPS. While for critical structures, it would be reasonable to report Dm always. However in future with the availability of finer spatial resolution, Dm will be the most suitable variable for both target and critical structures’ dose prescription and reporting in MC treatment planning.
文摘Cone-beam CT (CBCT) images acquired during radiation treatment can be used to recalculate the dose distribution as well as to confirm the treatment location. However, it is difficult to obtain the electron densities (EDs) necessary for dose calculation from CBCT images because of the effects of scatter contamination during CBCT image acquisition. This paper presents a mathematical method for converting the pixel values of CBCT images (CBCT values) into Hounsfield units (HUs) of radiation treatment simulation CT (simCT) images for use in radiation treatment planning. CBCT values are converted into HUs by matching the histograms of the CBCT values with the histograms of the HUs for each slice via linear scaling of the CBCT values. For prostate cancer and head-and-neck cancer patients, the EDs obtained from converted CBCT values (mCBCT values) show good agreement with the EDs obtained from HUs, within approximately 3.0%, and the dose calculated on the basis of CBCT images shows good agreement with the dose calculated on the basis of the simCT images, within approximately 2.0%. Because the CBCT values are converted for each slice, this conversion method can account for variation in the CBCT values associated with differences in body size, body shape, and inner tissue structures, as well as in longitudinally displaced positions from the isocenter, unlike conventional methods that use electron density phantoms. This method improves on conventional CBCT-ED conversion and shows considerable potential for improving the accuracy of radiation treatment planning using CBCT images.
文摘The majority of EPID dosimetry literature discusses response linearity and the so-called image lag and ghosting effects despite the lack of a common definition of these quantities. However, the results of these studies are generally not consistent, and it is often difficult to compare the results from different studies. We present here a detailed study of the acquisition and readout characteristics of a-Si EPID and its dosimetric performance. EPID response was assessed over the range of 1 - 500 MU using different dose rates and integration times. In addition, a computer model was designed to simulate the EPID image formation with different dose, dose rate, and integration time combinations. All aspects of image processing and readout simulation were carried out using custom written MatLab codes. Two distinct signal profiles were observed depending on the delivered dose, dose rate and integration time combination. Total integrated signal (S<sub>T</sub>) is linear with the delivered dose. For dosimetry, image lag and ghosting effects mainly result in the residual signal (S<sub>R</sub>) that appears as delayed signal after the end of irradiation. At its maximum, S<sub>R</sub> is less than 2.5% of S<sub>T</sub>. The readout technique is such that it is impossible to measure S<sub>R</sub> accurately. S<sub>R</sub> is definable only when readout equilibrium occurs. Signal profiles provide a through and reliable description of the EPID response incorporating the dose, dose rate, integration time, and the residual signal. The definition of EPID signals based on this method shall provide an accurate universal EPID dosimetry framework.
文摘The objective of this study is to investigate the dose perturbations introduced by the implanted gold fiducial markers in the prostate cancer intensity modulated proton therapy (IMPT) and the impacts of different plan designs on the pertur-bations. Five proton plans: a single lateral field 3D-modulation (3D-mod) plan, 2 fields laterally opposing 3D-mod plan, 6-, 9-, and 18-field distal edge tracking (DET) plans were designed on the CT images of a prostate patient. The dose distributions were first generated for the plans free of fiducial markers with 78 Gy prescribed to 95% of the PTV. To derive the dose perturbations of the gold fiducial markers, three cylindrical shaped gold fiducial markers (3 mm long and 1 mm in diameter) were artificially inserted into the prostate, and the dose distributions were re-computed. Monte Carlo method was used for dose computation. It was found that the gold fiducial markers perturbed the dose distribu-tions, especially along the beam paths. The markers caused a shadowing effect reducing the doses in the areas beyond the markers. Overall, due to the presence of the fiducial markers, D99% of prostate were reduced by 2.96 Gy, 4.21 Gy, 0.16 Gy, 0.34 Gy, 0.15 Gy for the plans of single field 3D-mod, 2-field parallel opposed 3D-mod, 6-, 9-, and 18-field DET respectively. Our study showed these dose perturbation effects decreased with the increase of number of beam angles. Up to 6 beam angles may be required to reduce the dose perturbations from the gold fiducial markers to a clini- cally acceptable level in IMPT.
文摘Purpose: To test the concept of Statistical Process Control (SPC) as a Quality Assurance (QA) procedure for dose verifications in external beam radiation therapy in conventional and 3D Conformal Radiotherapy (3D-CRT) treatment of cervical cancer. Materials and Methods: A study of QA verification of target doses of 198 cervical cancer patients undergoing External Beam Radiotherapy (EBRT) treatments at two different cancer treatment centers in Kenya was conducted. The target doses were determined from measured entrance doses by the diode in vivo dosimetry. Process Behavior Charts (PBC) developed by SPC were applied for setting Action Thresholds (AT) on the target doses. The AT set was then proposed as QA limits for acceptance or rejection of verified target doses overtime of the EBRT process. Result and Discussion: Target doses for the 198 patients were calculated and SPC applied to test whether the action limits set by the Process Behavior Charts could be applied as QA for verified doses in EBRT. Results for the two sub-groups of n = 3 and n = 4 that were tested produced action thresholds which are within clinical dose specifications for both conventional AP/PA and 3D-CRT EBRT treatment techniques for cervical cancer. Conclusion: Action thresholds set by SPC were within the clinical dose specification of ±5% uncertainty for both conventional AP/PA and 3D-CRT EBRT treatment techniques for cervical cancer. So the concept of SPC could be applied in setting QA action limits for dose verifications in EBRT.
文摘The Halcyon O-ring gantry linear accelerator from Varian Medical Systems is delivered with a hardcoded beam-source model and Analytical Anisotropic Algorithm dose calculation algorithm as standard, while the Acuros XB algorithm is a purchasable option. The models in both algorithms are factory-configured and do not permit fine-tuning by the user. In this study, we compared the two algorithms for sequential boost RapidArc treatment planning of Head & Neck cancers using D98%, D95%, D50%, D2% and maximum dose to assess dose coverage of nodal and tumor planning target volumes (PTV_N and PTV_T, respectively), and cochlear D5%, parotid D20%, D50%, mean dose, and cord maximum dose to evaluate doses to organs- at-risk. The conformity index (CI), homogeneity index (HI) and total number of monitor units (MU) quantified plan quality. We found statistically significant differences in PTV_N D2%, maximum dose, HI, PTV_T D98%, D95%, D2%, Max, HI, and total MU. Statistically significant differences in Cochlear D5% and Parotid mean doses were also encountered. These differences may not necessarily be clinically significant, however. Therefore, we believe that both calculation algorithms are adequate for RapidArc planning of Head & Neck cancers.
文摘In the linear accelerator-based stereotactic radio surgery (SRS) and stereotactic body radiotherapy (SBRT) programs, single isocenter-multiple metastases’ treatment has become more and more popular due to their high efficiency in treatment time. However, the absence of a comprehensive quality assurance program is still the challenge for medical physicists. The Winston-Lutz-Gao test, which we developed two years ago, was performed for the first time on a True Beam STx (Varian Medical System) linear accelerator in this study. Beams were designed by Eclipse with gantry, collimator, and couch full rotations, and a 200-pound weight was placed on the couch to mimic real treatment. The “frameless SRS QA target pointer” from the Brainlab company, with a 3.5-mm metallic ball embedded in the center, was used as a phantom. Images were acquired by the portal imager built-in linear accelerator and analyzed directly by the Image browser in ARIA. We found that the farther the metastases were from the linac isocenter, the worse the congruence was between the beam mechanical and the radiation center. The farthest metastases should be within 6 cm from the linac isocenter per the AAPM TG-142 and American Society for Radiation Oncology (ASTRO) white paper criteria. To the best of our knowledge, this is the first off-isocenter Winston-Lutz test performed on a True Beam STx linear accelerator.
文摘In the present work, a treatment technique for trigeminal neuralgia (TN) using LINAC radiosurgery is shown. The technique is based on the optimization of ten static arcs in such a way as to minimize the overlapping of the treatment fields with the brainstem. We will call this technique brainstem-optimized (BO). The results are compared with another technique described in the literature known as a virtual cone (VC). The comparison of dosimetry results that have been carried out essentially shows that the doses in the brainstem V12Gy-brainstem, D0.5cm<sup>3</sup>-brainstem and D0.035 cm<sup>3</sup>-brainstem are lower in the BO versus VC technique, and with the parameters V50% (whole brain) and V12Gy-cerebrum higher in BO versus VC. Our goal is to keep the dose to the brainstem as low as possible and, if possible, at most between 12 Gy and 15 Gy. The BO technique meets our purposes and is considered clinically acceptable at our institution.
文摘Polymer gels are three-dimensional dosimetric tools. The purpose of the present study was to investigate the temperature dependence of polymer gels during scanning Magnetic Resonance Imaging. Prepared gels were irradiated with a 6MV X-ray beam at intensities ranging from 0 to 20 Gy in order to investigate their dose-R2 and dose-R1 responses. Irradiated gels were evaluated from 1.5-T magnetic resonance R2 and R1 images for each 5°C change in temperature from 5°C to 41°C, and then the four-field box technique irradiation plan was used to deliver a total dose of 4 Gy using the same beam weight in each direction to the prepared gels. The profile of the dose map generated from the four-field irradiated gel data at 20°C was then compared with the planned data. The dose-R2 response curve was linear up to 20 Gy at 20°C, with a slope of 1.17 Gy-1˙s-1. The slopes of the fitted curves of the dose-R2 decreased as gel temperature increased. The slopes of the dose-R1 curves were more parallel than the slopes of the dose-R2 curves between 5 and 41°C. The difference in the full width of half maximum of the gel profile data obtained using the four-field box technique at 20°C and the planned data were below 5% on average. The dose map from the irradiated gels obtained using the dose-R2 curve was the same as that from the planned data under the same temperature conditions. Measurement of difference between various temperatures is significant with dose accuracy. It is suitable to evaluate the gel dosimeter under the thermal equilibrium condition, MRI room temperature from the point of view of the stability of the irradiated gels.
文摘Aim: Dosimetric analysis of three different Radiotherapy techniques in patients with Breast Cancer and their impact on OAR’s. Materials and Methods: 12 patients of Carcinoma Breast who received breast radiotherapy were selected for analysis. Computed tomography (CT) simulation image data sets were retrieved. Planning target Volume (PTV), heart and ipsilateral lung were contoured for planning and analysis of doses. Three different plans using conventional bi-tangential fields were prepared, Plan 1 with SAD full beam with wedge (SAD-FBW), Plan 2 with SSD half beam with wedge (SSD-HBW) and plan 3 with SSD half beam without wedge techniques (SSD-HBO) in CMS Xio TPS. Statistical analysis was done using SPSS version 16.0. Results: The PTV coverage was significantly better in SAD-FBW techniques when compared with the other two techniques i.e. SSD-HBW (mean = 92.33, SD = 4.69, p = 0.005) and SSD-HBO (mean = 75.05, SD = 11.92, p = 0.002). The mean heart doses were significantly better in SAD-FBW compared to SSD-HBW (mean = 3.75, SD = 2.27, p = 0.017) but in SSD-HBO technique mean heart doses were better than SAD-FBW technique (mean = 3.27, SD = 1.94, p = 0.004). Similarly, the left lung V20 values were significantly better in SSD-HBO technique than SAD-FBW technique (mean = 11.75, SD = 4.34, p = 0.004) but there was statistically insignificant difference between the SAD-FBW and SSD-HBW techniques. The treatment monitor units were significantly less in SAD-FBW compared to SSD-HBW but SSD-HBO has less MU compared to SAD-FBW technique. Conclusion: SAD Full Beam with wedge technique is practically better than SSD Half Beam technique with or without wedge without compromising PTV coverage considering other dosimetric parameters. We also recommend that centers treating patient with half beam SSD techniques should shift immediately to SAD techniques.
文摘Objective: To investigate better dosimetric distribution of volumetric modulated arc therapy (VMAT) vs. 5F intensity modulated radiotherapy (IMRT) and 3D conformal radiotherapy (3DCRT) in patients with locally advanced rectal cancer (LARC) when treated with neoadjuvant chemoradiotherapy. Methods: 3D-CRT, 5F-IMRT and VMAT plans for preoperative radiotherapy were 66011designed in 12 patients with locally advanced rectal cancer. The conformity index (CI) and homogeneity index (HI) in target volume, and the dose and volume of the organs at risk (OAR) irradiated including small bowel, bladder and bilatera1 femoral heads were compared among the three plans. Results: The CI for planning target volume (PTV) 2 and HI for PTV1 of VMRT and 5F-IMRT were superior to 3D-CRT. The CI of VMAT, 5F-IMRT and 3D-CRT plans were 0.71, 0.69 and 0.62 (p = 0.011 and p = 0.019, respectively). The HI of the VMAT and 5F-IMRT plans were both 1.04 and 3D-CRT planning was 1.06 (p = 0.022 and p = 0.006, respectively). The V35 - V45 of small bowel in VMAT were significantly less than in 5F-IMRT and 3D-CRT. V35 was 47.0, 56.4, and 72.8 cm3 for VMAT, 5F-IMRT, and 3D-CRT (p = 0.021 and p = 0.034, respectively), while V40 was 30.5, 35.5, 45.1 cm3 (p = 0.024 and p = 0.032, respectively) and V45 was 15.1, 18.1, 30.0 cm3 (p = 0.033 and p = 0.032, respectively). The D5, V30 and V50 of bladder in 3D-CRT were less than in VMAT and 5F-IMRT planning (p = 0.034, 0.004, 0.002 and p = 0.027, 0.003, 0.002, respectively). The Dmean of left femoral head in VMAT and 5F-IMRT were less than in 3D-CRT planning (p = 0.028 and p = 0.022, respectively) and the Dmean, V30 of right femoral head in VMAT and 5F-IMRT were better than in 3D-CRT planning (p = 0.044, 0.036 and p = 0.023, 0.028, respectively). Conclusions: Dosimetric analyses demonstrated that IMRT is superior to 3D-CRT in the conformity and homogeneity of dose distribution to the target volume, and provide a better protection to OARs sparing in patients with locally advanced rectal cancer for preoperative radiotherapy. With similar target coverage, VMRT is superior to 5F-IMRT in normal tissue sparing.
