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A Novel Proton Pencil Beam Scanning Technique for Postmastectomy Chest Wall Irradiation
S932
International Journal of Radiation Oncology Biology Physics
3828
cover the whole chest wall and the potentially involved lymph nodes (axillary, supraclavicular, internal mammary), all of which volumes are combined into a single scanning target volume (STV) for the spot map optimization. An 8 cm thick range shifter, made of Lucite, is used to reduce the proton beam energy in order to appropriately cover the superficial portion of the target volumes. The PBS field usually contains less than 15 layers equally spaced about 5 mm, with a total number of spots in the range of 1500 to 2000. For patients with breast implants, the stopping power ratio of the implant materials was separately measured, and the remaining range uncertainty is limited to that from the chest wall only. Surface imaging, along with daily radiography, is used for patient positioning in order to improve setup accuracy for the largely superficial target volume and to monitor anatomical changes during the course of treatment. Results: Over 20 patients (mostly left sided) have been treated at the institution using the described technique. A single PBS field proves to be sufficient to deliver full and more homogeneous dose coverage of all the target volumes as well as less dose to cardiac tissues compared to conventional photon/electron treatment plans. All treatment fields pass QA gamma test by more than 95% (3 mm / 3% of prescription dose). A planning study, based on 4D CT, showed that the PBS dose distribution is robust to patient’s breathing, as well as to patient’s setup uncertainties, 3 mm shifts and 2 rotations. Conclusions: A novel treatment technique for post-mastectomy chest wall irradiation using proton PBS fields is currently offered by the institution. While improving both target coverage and OAR sparing, this technique also offers simpler planning and reduced treatment time. Author Disclosure: N. Depauw: A. Employee; Massachusetts General Hospital. E. Batin: A. Employee; Massachusetts General Hospital. J. Daartz: A. Employee; Massachusetts General Hospital. S. MacDonald: A. Employee; Massachusetts General Hospital. H. Kooy: A. Employee; Massachusetts General Hospital. H. Lu: A. Employee; Massachusetts General Hospital.
Direction Modulated Brachytherapy (DMBT) for Cervical Cancer D. Han,1 M.J. Webster,1 D.J. Scanderbeg,1 C. Yashar,1 D. Choi,2 B. Song,2 S. Devic,3 A. Ravi,4 and W.Y. Song1; 1University of California, San Diego, San Diego, CA, 2University of California, San Diego, CA, 3McGill University, Montreal, QC, Canada, 4Sunnybrook Odette Cancer Centre, Toronto, ON, Canada Purpose/Objective(s): A new intra-uterine tandem design is proposed for creating non-isotropic 192-Ir dose distribution and give unprecedented dose conformality for treatment of cervical cancer. Materials/Methods: A DMBT design was made of non-magnetic high density tungsten alloy (18.0g/cc) cylinder with 6 peripheral grooves running along the length for an 192-Ir HDR afterloader source to travel along. The groove has 1.3mm in diameter and evenly distributed on the tungsten alloy, which has a diameter of 5.4mm. The tungsten alloy is enclosed in a total diameter of 6.4mm polyoxymethylene tube (1.41 g/ cc). For calculating dose distribution, 51 million decay events are simulated on Monte Carlo simulation and resulting non-isotropic dose distributions. 75 plans (5 fraction [fx] of 15 patient cases), clinically treated with conventional tandem & ovoids (T&O) applicator, were replanned on an in-house development HDR brachytherapy planning platform, which is intensity modulated planning capability using Simulated Annealing and Constrained-Gradient Optimization algorithms. All DMBT plan results were compared against the T&O clinically treated plans, which were normalized to match the HRCTV V100 coverage. Also all the plans were optimized with the same ovoids in place as the conventional T&O plans. Results: Generally, the plan qualities were markedly better using DMBT. Among the 75 plans, an average bladder, rectum, and sigmoid dose (D2cc) reduction were 0.590.87 Gy (8.528.7%), 0.480.55 Gy (21.127.2%), 0.100.38 Gy (40.6214.9%) among the 75 plans, respectively. The bladder dose, 3.20Gy (40.8%), was the best single plan reduction, due to the horseshoe-like bladder around the CTV. The best sigmoid dose reduction was 1.26Gy (27.5%) for endophytic growth type cervical cancer. Overall, the most dose reduction was caused by the dose flexibility of DMBT. The HRCTV D90 was similar with 6.550.96 Gy for T&O and 6.591.06 for DMBT. Conclusions: The new tandem designs that advance the conformality of image-guided cervix HDR were created in congruence with the current trend of 3D image based planning to maximize the therapeutic ratio. Author Disclosure: D. Han: None. M.J. Webster: None. D.J. Scanderbeg: None. C. Yashar: None. D. Choi: None. B. Song: None. S. Devic: None. A. Ravi: None. W.Y. Song: None.
3829 A Novel Proton Pencil Beam Scanning Technique for Postmastectomy Chest Wall Irradiation N. Depauw,1,2 E. Batin,1 J. Daartz,1 S. MacDonald,1 H. Kooy,1 and H. Lu1; 1 Massachusetts General Hospital, Boston, MA, 2University of Wollongong, Wollongong, Australia Purpose/Objective(s): Post-mastectomy radiation therapy treatment (PMRT) is conventionally performed using a composition of photon and electron fields. Including the internal mammary nodes is always a challenge in such treatment for patients with unfavorable cardiac anatomy and/ or breast implants. Furthermore, multi-field matching results in hot and cold spots, as well as extended treatment time. We have developed a PMRT technique using a single proton pencil beam scanning (PBS) field that includes the whole chest wall and all nodal regions with complete target coverage and reduced dose to cardiac and lung tissues. Materials/Methods: The patients undergo a CT scan on an angled breast board, as for regular photon/electron treatment, but with the addition of a chin strap and hand grips to provide additional immobilization and reproducibility. An in-house software, with multi-criteria optimization (MCO) capability, is used for PBS treatment planning. A single isocentric field, angled at 30 degrees from vertical, is used to
3830 Real-Time Gall Bladder Motion and Deformation During Fractionated Stereotactic Body Radiation Therapy D. Gupta, T. Kataria, A. Abhishek, S.S. Bisht, K.P. Karrthick, V. Subramani, T. Basu, S. Goyal, A. Srivastava, K. Sharma, and H.B. Govardhan; Medanta The Medicity, Gurgaon, India Purpose/Objective(s): To analyze real time intra-fractional rotational and translational motion of Gall bladder during cyber knife based stereotactic body radiation therapy (SBRT). Materials/Methods: We analyzed 1,500 alignment shifts in target positions during 15 treatment sessions in 5 consecutive gall bladder cancer patients being treated with hypofractionated SBRT with CyberKnife using synchrony model. The shifts were obtained by tracking 3-4 gold seeds implanted via a pair of in-room kV X-ray imagers. Images were acquired every 15 seconds for first 25 minutes of treatment. For each sequential pair of images, the correction to the target position was calculated in six-degrees of motion (3 rotations and 3 translations). The threshold for translational and rotational motion were 10 mm and 3 respectively. Rigid body error(RBE) was also analyzed for each patient to find out the deformation during the course of treatment. Results: The rotational mean and standard deviation for the intra-fraction Gall bladder motion were 0.13 1.33, 0.87 1.49 and -0.27 2.09 in roll, pitch and yaw directions respectively. The translational mean and standard deviation for the intra-fraction Gall Bladder motion were 0.53mm 4.34, -0.37mm 2.63 and 0.87mm 1.76 in the Left-right (LR), anterior-posterior (AP), superior-inferior (SI) directions respectively. Intra-fraction Gall Bladder motion of less than 3 was observed 95.67%, 89.9%, and 86.2%, while greater than 3 was only observed in 4.33%, 10.1% and 13.8% in the Roll, Pitch, and Yaw directions, respectively. Intra-fraction Gall Bladder motion of less than 2mm was observed 34.6%, 78.6%, and 72.3%, in the LR, AP, and SI directions, respectively, and 47.4%, 88.2%, and 86.2%, in the LR, AP, and SI directions, respectively,
International Journal of Radiation Oncology Biology Physics
3828
cover the whole chest wall and the potentially involved lymph nodes (axillary, supraclavicular, internal mammary), all of which volumes are combined into a single scanning target volume (STV) for the spot map optimization. An 8 cm thick range shifter, made of Lucite, is used to reduce the proton beam energy in order to appropriately cover the superficial portion of the target volumes. The PBS field usually contains less than 15 layers equally spaced about 5 mm, with a total number of spots in the range of 1500 to 2000. For patients with breast implants, the stopping power ratio of the implant materials was separately measured, and the remaining range uncertainty is limited to that from the chest wall only. Surface imaging, along with daily radiography, is used for patient positioning in order to improve setup accuracy for the largely superficial target volume and to monitor anatomical changes during the course of treatment. Results: Over 20 patients (mostly left sided) have been treated at the institution using the described technique. A single PBS field proves to be sufficient to deliver full and more homogeneous dose coverage of all the target volumes as well as less dose to cardiac tissues compared to conventional photon/electron treatment plans. All treatment fields pass QA gamma test by more than 95% (3 mm / 3% of prescription dose). A planning study, based on 4D CT, showed that the PBS dose distribution is robust to patient’s breathing, as well as to patient’s setup uncertainties, 3 mm shifts and 2 rotations. Conclusions: A novel treatment technique for post-mastectomy chest wall irradiation using proton PBS fields is currently offered by the institution. While improving both target coverage and OAR sparing, this technique also offers simpler planning and reduced treatment time. Author Disclosure: N. Depauw: A. Employee; Massachusetts General Hospital. E. Batin: A. Employee; Massachusetts General Hospital. J. Daartz: A. Employee; Massachusetts General Hospital. S. MacDonald: A. Employee; Massachusetts General Hospital. H. Kooy: A. Employee; Massachusetts General Hospital. H. Lu: A. Employee; Massachusetts General Hospital.
Direction Modulated Brachytherapy (DMBT) for Cervical Cancer D. Han,1 M.J. Webster,1 D.J. Scanderbeg,1 C. Yashar,1 D. Choi,2 B. Song,2 S. Devic,3 A. Ravi,4 and W.Y. Song1; 1University of California, San Diego, San Diego, CA, 2University of California, San Diego, CA, 3McGill University, Montreal, QC, Canada, 4Sunnybrook Odette Cancer Centre, Toronto, ON, Canada Purpose/Objective(s): A new intra-uterine tandem design is proposed for creating non-isotropic 192-Ir dose distribution and give unprecedented dose conformality for treatment of cervical cancer. Materials/Methods: A DMBT design was made of non-magnetic high density tungsten alloy (18.0g/cc) cylinder with 6 peripheral grooves running along the length for an 192-Ir HDR afterloader source to travel along. The groove has 1.3mm in diameter and evenly distributed on the tungsten alloy, which has a diameter of 5.4mm. The tungsten alloy is enclosed in a total diameter of 6.4mm polyoxymethylene tube (1.41 g/ cc). For calculating dose distribution, 51 million decay events are simulated on Monte Carlo simulation and resulting non-isotropic dose distributions. 75 plans (5 fraction [fx] of 15 patient cases), clinically treated with conventional tandem & ovoids (T&O) applicator, were replanned on an in-house development HDR brachytherapy planning platform, which is intensity modulated planning capability using Simulated Annealing and Constrained-Gradient Optimization algorithms. All DMBT plan results were compared against the T&O clinically treated plans, which were normalized to match the HRCTV V100 coverage. Also all the plans were optimized with the same ovoids in place as the conventional T&O plans. Results: Generally, the plan qualities were markedly better using DMBT. Among the 75 plans, an average bladder, rectum, and sigmoid dose (D2cc) reduction were 0.590.87 Gy (8.528.7%), 0.480.55 Gy (21.127.2%), 0.100.38 Gy (40.6214.9%) among the 75 plans, respectively. The bladder dose, 3.20Gy (40.8%), was the best single plan reduction, due to the horseshoe-like bladder around the CTV. The best sigmoid dose reduction was 1.26Gy (27.5%) for endophytic growth type cervical cancer. Overall, the most dose reduction was caused by the dose flexibility of DMBT. The HRCTV D90 was similar with 6.550.96 Gy for T&O and 6.591.06 for DMBT. Conclusions: The new tandem designs that advance the conformality of image-guided cervix HDR were created in congruence with the current trend of 3D image based planning to maximize the therapeutic ratio. Author Disclosure: D. Han: None. M.J. Webster: None. D.J. Scanderbeg: None. C. Yashar: None. D. Choi: None. B. Song: None. S. Devic: None. A. Ravi: None. W.Y. Song: None.
3829 A Novel Proton Pencil Beam Scanning Technique for Postmastectomy Chest Wall Irradiation N. Depauw,1,2 E. Batin,1 J. Daartz,1 S. MacDonald,1 H. Kooy,1 and H. Lu1; 1 Massachusetts General Hospital, Boston, MA, 2University of Wollongong, Wollongong, Australia Purpose/Objective(s): Post-mastectomy radiation therapy treatment (PMRT) is conventionally performed using a composition of photon and electron fields. Including the internal mammary nodes is always a challenge in such treatment for patients with unfavorable cardiac anatomy and/ or breast implants. Furthermore, multi-field matching results in hot and cold spots, as well as extended treatment time. We have developed a PMRT technique using a single proton pencil beam scanning (PBS) field that includes the whole chest wall and all nodal regions with complete target coverage and reduced dose to cardiac and lung tissues. Materials/Methods: The patients undergo a CT scan on an angled breast board, as for regular photon/electron treatment, but with the addition of a chin strap and hand grips to provide additional immobilization and reproducibility. An in-house software, with multi-criteria optimization (MCO) capability, is used for PBS treatment planning. A single isocentric field, angled at 30 degrees from vertical, is used to
3830 Real-Time Gall Bladder Motion and Deformation During Fractionated Stereotactic Body Radiation Therapy D. Gupta, T. Kataria, A. Abhishek, S.S. Bisht, K.P. Karrthick, V. Subramani, T. Basu, S. Goyal, A. Srivastava, K. Sharma, and H.B. Govardhan; Medanta The Medicity, Gurgaon, India Purpose/Objective(s): To analyze real time intra-fractional rotational and translational motion of Gall bladder during cyber knife based stereotactic body radiation therapy (SBRT). Materials/Methods: We analyzed 1,500 alignment shifts in target positions during 15 treatment sessions in 5 consecutive gall bladder cancer patients being treated with hypofractionated SBRT with CyberKnife using synchrony model. The shifts were obtained by tracking 3-4 gold seeds implanted via a pair of in-room kV X-ray imagers. Images were acquired every 15 seconds for first 25 minutes of treatment. For each sequential pair of images, the correction to the target position was calculated in six-degrees of motion (3 rotations and 3 translations). The threshold for translational and rotational motion were 10 mm and 3 respectively. Rigid body error(RBE) was also analyzed for each patient to find out the deformation during the course of treatment. Results: The rotational mean and standard deviation for the intra-fraction Gall bladder motion were 0.13 1.33, 0.87 1.49 and -0.27 2.09 in roll, pitch and yaw directions respectively. The translational mean and standard deviation for the intra-fraction Gall Bladder motion were 0.53mm 4.34, -0.37mm 2.63 and 0.87mm 1.76 in the Left-right (LR), anterior-posterior (AP), superior-inferior (SI) directions respectively. Intra-fraction Gall Bladder motion of less than 3 was observed 95.67%, 89.9%, and 86.2%, while greater than 3 was only observed in 4.33%, 10.1% and 13.8% in the Roll, Pitch, and Yaw directions, respectively. Intra-fraction Gall Bladder motion of less than 2mm was observed 34.6%, 78.6%, and 72.3%, in the LR, AP, and SI directions, respectively, and 47.4%, 88.2%, and 86.2%, in the LR, AP, and SI directions, respectively,