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VMAT for localized prostate cancer
Abstracts of the SFPM Annual Meeting 2013 / Physica Medica 29 (2013) e1–e46
Reproducibility of surface acquisition and setup procedure was better than 0.5 mm and 0.5° and 1 mm and 1°, respectively. The system accuracy was better than 1 mm and 1° when a catalyst image was used as reference. A global worsening was observed using an external surface extracted from CT study. Conclusion: This localization and positioning system is expected to become an important component within our radiation therapy process, so a quality assurance of this system is essential. Moreover, this study allows us to refine and to adapt our clinical procedure. http://dx.doi.org/10.1016/j.ejmp.2013.08.015
13 QUALITY CONTROL ON BREATH CONTROL SYSTEM AND ANALYSE OF INCERTAINITY EFFECT ON TREATMENT F. Peretti, S. Gempp, A. Dorenlot, J. Desrousseaux, S. Hibert. AP-HM, Marseille, France Introduction: ABC system of Elekta is a breath control system for respiratory motion using a spyrometer. The goal of this system is to reduce marging around CTV and make feasible a dose escalation. Recommendations for spyrometer quality control only exist in pneumology unit. We organized some control to evaluate system deviation and the effect on treatment. Materials and methods: ABC system contain a spyrometer and at the end of system, a balloon. The respiration state is the inhale blocked state to make treatment. Quality controls equipment were made with a 3L syringe (Hans Rudolph). Measure volume was checked between 1.5 L and 2.5 L. Some controls were done at different times (linearity, accuracy, reproducibility) like in recommendations. Controls were made on every ABC system in attend to test inter-system reproducibility. Some variations were noted. The effects on treatment were analysed. Results: Reproducibility test showed standard deviation between 4.9% and 2%. Some deviations inter-ABC system were observed between 3.4% and 3.2%. Recommendations are ±3%. The effects on lung voulme are more important in inferior lobe than superior lobe. Tumor motion was affected by this deviation like 1.5 cm in sup-inf and 2 cm in ant-post. Conclusion: To take account of no-reproducibility, we modified the ITV-marging. A limit was fixed to decide a spyrometer changing. A system of quality control was realized. http://dx.doi.org/10.1016/j.ejmp.2013.08.019
14 LET US STOP TREATMENTS BY IMRT/VMAT FOR LOCALIZED PROSTATE CANCER M. Rouzaud. Radiation Oncology, Geneva University Hospitals, Switzerland Introduction: The goal of this study is to determine the best treatment technique for prostate cancer treatments depending on various patients repositioning methods. Material and methods: Five patients treated for localized prostate cancer to a total dose of 60 Gy in 15 fractions were enrolled in this study. For 6 treatment fractions, different repositioning methods (tattoos, bones, fiducial markers, and organs) were simulated. Plans were calculated on CBCT for each method and treatment technique: conformal 6 fields with various PTV margins, IMRT and VMAT. Dose calculation on CBCT, respect to CT, was estimated to be correct
e5
within 2%. Approximately 500 DVHs for PTVs and rectum were obtained. Integrated doses for target volumes and rectum for each couple of treatment technique versus positioning method were calculated. An optimization function using weights for the integral doses of PTVs and rectum was created to find the best compromise between target coverage and rectum sparing. Results: Conformal 6 fields plan, with PTV margins of 3 mm, was the best technique, when re-calculating the dose on the daily CBCT image with newly delineated organ contours. Unless we give considerable weight to the rectum, all other techniques appeared inferior with in particular repositioning on tattooed points to proscribe. VMAT plans simply re-calculated with no optimization on newly delineated organs but with repositioning on CBCT was the second treatment option. Conclusions: The results showed clearly that a conformal 6 beams plan with reduced margins based on daily redefined contours on each CBCT is an excellent treatment choice. On-line adaptive planning for this technique would be fast enough to avoid patient’s internal organ movements, without need of pre-treatment QA on phantoms, therefore feasible and superior to a dose modulated plans not adapted to daily organ motion. It is obvious that the best choice depends on department technical possibilities, on the staff organization as well as patients’ acceptance of invasive acts (installation of fiducial markers, spacer, purging, etc.). Nevertheless an advanced treatment technique (IMRT/VMAT) is not necessarily the best choice.
http://dx.doi.org/10.1016/j.ejmp.2013.08.020
15 EVALUATION OF THE ACQUISITION PROTOCOLS OF THE XVI ELEKTA IMAGING SYSTEM F. Werle, E. Buffard, K. Brune, B. Perrin, D. Atlani. Hôpitaux Civils de Colmar, Colmar, France Introduction: The use of kV-CBCT for patient positioning during radiotherapy treatments requires the evaluation of acquisition protocols proposed by the manufacturer. Optimization of protocols consists in adapting the kV-CBCT acquisitions according to both patient size and treatment localization, in order to obtain sufficient image quality while minimizing the dose to the patient. The aim of this study is to evaluate the image quality and to measure the dose for each acquisition protocols proposed by the XVI ELEKTA system. Material and methods: The image quality is evaluated using the Catphan 600. For each protocol, a comparison of the CT number uniformity, the geometric distortion, the low contrast resolution and the high contrast spatial resolution is performed. The CBDIw is measured using a UNFORS CT chamber and an PTW 0.3 cc ionization chamber. In our institution, the kV-CBCT acquisitions are mainly used for prostate localizations. Thermoluminescent measurements are then performed to compare the dose delivered in the prostate and the femoral heads. Results: The pelvis and prostate are the first protocols evaluated. The results show that the prostate protocol is more irradiating than the pelvis with a CBDIw equal to 2.8 cGy against 1.8 cGy for the pelvis. In terms of image quality, the results show no significant differences. The CT number homogeneity is equal to 2.6% for prostate and 2.4% for pelvis protocol. For the low contrast resolution, we obtain values of 1.5% and 1.4% respectively for prostate and pelvis protocols. The high contrast spatial resolution is very low for both, with only 2 lp/cm. No geometric distortion is detected. We are studying the other protocols.
Reproducibility of surface acquisition and setup procedure was better than 0.5 mm and 0.5° and 1 mm and 1°, respectively. The system accuracy was better than 1 mm and 1° when a catalyst image was used as reference. A global worsening was observed using an external surface extracted from CT study. Conclusion: This localization and positioning system is expected to become an important component within our radiation therapy process, so a quality assurance of this system is essential. Moreover, this study allows us to refine and to adapt our clinical procedure. http://dx.doi.org/10.1016/j.ejmp.2013.08.015
13 QUALITY CONTROL ON BREATH CONTROL SYSTEM AND ANALYSE OF INCERTAINITY EFFECT ON TREATMENT F. Peretti, S. Gempp, A. Dorenlot, J. Desrousseaux, S. Hibert. AP-HM, Marseille, France Introduction: ABC system of Elekta is a breath control system for respiratory motion using a spyrometer. The goal of this system is to reduce marging around CTV and make feasible a dose escalation. Recommendations for spyrometer quality control only exist in pneumology unit. We organized some control to evaluate system deviation and the effect on treatment. Materials and methods: ABC system contain a spyrometer and at the end of system, a balloon. The respiration state is the inhale blocked state to make treatment. Quality controls equipment were made with a 3L syringe (Hans Rudolph). Measure volume was checked between 1.5 L and 2.5 L. Some controls were done at different times (linearity, accuracy, reproducibility) like in recommendations. Controls were made on every ABC system in attend to test inter-system reproducibility. Some variations were noted. The effects on treatment were analysed. Results: Reproducibility test showed standard deviation between 4.9% and 2%. Some deviations inter-ABC system were observed between 3.4% and 3.2%. Recommendations are ±3%. The effects on lung voulme are more important in inferior lobe than superior lobe. Tumor motion was affected by this deviation like 1.5 cm in sup-inf and 2 cm in ant-post. Conclusion: To take account of no-reproducibility, we modified the ITV-marging. A limit was fixed to decide a spyrometer changing. A system of quality control was realized. http://dx.doi.org/10.1016/j.ejmp.2013.08.019
14 LET US STOP TREATMENTS BY IMRT/VMAT FOR LOCALIZED PROSTATE CANCER M. Rouzaud. Radiation Oncology, Geneva University Hospitals, Switzerland Introduction: The goal of this study is to determine the best treatment technique for prostate cancer treatments depending on various patients repositioning methods. Material and methods: Five patients treated for localized prostate cancer to a total dose of 60 Gy in 15 fractions were enrolled in this study. For 6 treatment fractions, different repositioning methods (tattoos, bones, fiducial markers, and organs) were simulated. Plans were calculated on CBCT for each method and treatment technique: conformal 6 fields with various PTV margins, IMRT and VMAT. Dose calculation on CBCT, respect to CT, was estimated to be correct
e5
within 2%. Approximately 500 DVHs for PTVs and rectum were obtained. Integrated doses for target volumes and rectum for each couple of treatment technique versus positioning method were calculated. An optimization function using weights for the integral doses of PTVs and rectum was created to find the best compromise between target coverage and rectum sparing. Results: Conformal 6 fields plan, with PTV margins of 3 mm, was the best technique, when re-calculating the dose on the daily CBCT image with newly delineated organ contours. Unless we give considerable weight to the rectum, all other techniques appeared inferior with in particular repositioning on tattooed points to proscribe. VMAT plans simply re-calculated with no optimization on newly delineated organs but with repositioning on CBCT was the second treatment option. Conclusions: The results showed clearly that a conformal 6 beams plan with reduced margins based on daily redefined contours on each CBCT is an excellent treatment choice. On-line adaptive planning for this technique would be fast enough to avoid patient’s internal organ movements, without need of pre-treatment QA on phantoms, therefore feasible and superior to a dose modulated plans not adapted to daily organ motion. It is obvious that the best choice depends on department technical possibilities, on the staff organization as well as patients’ acceptance of invasive acts (installation of fiducial markers, spacer, purging, etc.). Nevertheless an advanced treatment technique (IMRT/VMAT) is not necessarily the best choice.
http://dx.doi.org/10.1016/j.ejmp.2013.08.020
15 EVALUATION OF THE ACQUISITION PROTOCOLS OF THE XVI ELEKTA IMAGING SYSTEM F. Werle, E. Buffard, K. Brune, B. Perrin, D. Atlani. Hôpitaux Civils de Colmar, Colmar, France Introduction: The use of kV-CBCT for patient positioning during radiotherapy treatments requires the evaluation of acquisition protocols proposed by the manufacturer. Optimization of protocols consists in adapting the kV-CBCT acquisitions according to both patient size and treatment localization, in order to obtain sufficient image quality while minimizing the dose to the patient. The aim of this study is to evaluate the image quality and to measure the dose for each acquisition protocols proposed by the XVI ELEKTA system. Material and methods: The image quality is evaluated using the Catphan 600. For each protocol, a comparison of the CT number uniformity, the geometric distortion, the low contrast resolution and the high contrast spatial resolution is performed. The CBDIw is measured using a UNFORS CT chamber and an PTW 0.3 cc ionization chamber. In our institution, the kV-CBCT acquisitions are mainly used for prostate localizations. Thermoluminescent measurements are then performed to compare the dose delivered in the prostate and the femoral heads. Results: The pelvis and prostate are the first protocols evaluated. The results show that the prostate protocol is more irradiating than the pelvis with a CBDIw equal to 2.8 cGy against 1.8 cGy for the pelvis. In terms of image quality, the results show no significant differences. The CT number homogeneity is equal to 2.6% for prostate and 2.4% for pelvis protocol. For the low contrast resolution, we obtain values of 1.5% and 1.4% respectively for prostate and pelvis protocols. The high contrast spatial resolution is very low for both, with only 2 lp/cm. No geometric distortion is detected. We are studying the other protocols.