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Potential Added Value of Structure-Based Deformable Image Registration for Dose Accumulation in External Beam Radiotherapy and Brachytherapy in Cervical Cancer
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Abstracts / Brachytherapy 15 (2016) S21eS204
Comparison with other imaging modalities (Fig. 1) showed good agreement between US- and MR-based target D90 (!4 Gy EQD2 difference), but a large discrepancy between US and CT values, mainly due to overestimation of the CTVHR width on CT. Analysis of the TRUS/CT plan on MRI resulted in a clinically acceptable dose distribution.
fraction (EQD2). For the uniform dose (UD) method, the prescribed EBRT dose was added to the brachytherapy D2cc and D1cc. For the overlapping high dose method (OHD), the EBRT D2cc and D1cc was added to the brachytherapy D2cc and D1cc. Next, we performed two structure-based DIRs for each patient for the bladder and rectum separately, using the EBRT CT as the frame of reference. The FeatureBased Deformable Registration tool, available in a research version of Oncentra Brachy (Elekta Brachytherapy, Veenendaal, The Netherlands) was used for the DIR. For 3D addition of the doses with DIR, the transformation vectors were used to deform the EBRT dose distribution for each organ separately (Figure A, B). Next, the EBRT and brachytherapy doses were converted to EQD2 and summed voxel-byvoxel. The cumulative D2cc and D1cc in bladder and rectum were calculated and compared to the UD method and the OHD method. Results: The results are shown in Fig. C. Comparing the DIR method to either the UD method or the OHD method gave significantly different results. With the OHD method, the mean difference in D2cc and D1cc with 3D DIR was O1.1 GyEQD2, while the mean difference with the UD method was !0.4 GyEQD2. However, the difference between DIR and the other methods was small compared to the total cumulative D2cc and D1cc. Conclusions: The mean difference in D2cc and D1cc with the DIR method and the UD method or OHD method was small in the bladder and the rectum. However, the DIR method seems to provide added value to the OHD method in some cases, since the maximum difference with the DIR method could be as high as 3.2 GyEQD2. For the dose parameters under consideration, the EBRT dose can be considered uniform both in rectum and bladder when performing dose summation.
Figure 1. TRUS/CT planning workflow and comparison with other imaging modalities. Conclusions: During this feasibility study of a TRUS/CT treatment planning workflow for cervix cancer BT a full treatment could be simulated for one patient, resulting in a clinically acceptable dose distribution. A need for improved applicator localisation in TRUS volumes has been identified. Image registration accuracy could be improved by automatic applicator tracking during US acquisition, thus minimizing reconstruction uncertainties due to insufficient depiction of the whole applicator on US images.
PHSOR16 Presentation Time: 2:15 PM Potential Added Value of Structure-Based Deformable Image Registration for Dose Accumulation in External Beam Radiotherapy and Brachytherapy in Cervical Cancer Laura E. van Heerden, MSc, Anette C. Houweling, PhD, Kees Koedooder, PhD, Zdenko van Kesteren, PhD, Coen R.N. Rasch, MD, PhD, Bradley R. Pieters, MD, PhD, Arjan Bel, PhD. Radiation Oncology, Academic Medical Center, Amsterdam, Netherlands. Purpose: Advanced stage cervical cancer is commonly treated with a combination of external beam radiotherapy (EBRT) and a brachytherapy boost to the tumor area using an intracavitary applicator. In clinical practice, the cumulative D2cc and D1cc are calculated by simply adding the separate dose parameters, assuming that the EBRT dose can be considered uniform. Alternatively, it is assumed that the high dose volumes overlap for both treatments. To account for dose non-uniformity and deformation of the anatomy due to tumor shrinkage and organ movement in the cumulative dose parameters, it is preferable to sum the 3D dose distributions. Deformable image registration (DIR) can be applied to evaluate the total planned (biological equivalent) dose. The aim of this study is to determine the potential added value of DIR in the evaluation of cumulative dose parameters by testing if the clinically applied methods yield similar results. Materials and Methods: Twelve patients with cervical cancer, treated with a combination of EBRT (VMAT, 23 x 2Gy), planned on CT, and MRIguided PDR brachytherapy (24 x 1Gy, hourly) were retrospectively studied. Dose parameters were converted to equivalent dose in 2Gy per
Figure. A) MR image of a patient with the original brachytherapy bladder contour in red, and the warped EBRT bladder contour obtained with DIR in blue, B) Warped EBRT dose in the bladder region, C) The planned cumulative D2cc and D1cc calculated with the DIR method, the uniform dose method and the overlapping high dose method, and the difference DD2cc and DD1cc with the DIR method, in bladder and D) rectum. The mean and the range over all patients are shown.
PHSOR17 Presentation Time: 2:20 PM Evaluation of an Automated Deformable Registration Algorithm for MRI-Guided Focal Boost Integrated with Ultrasound-Based High-Dose Rate Brachytherapy in the Treatment of Prostate Cancer Joelle Helou, MD1,2, Amir Khojaste, PhD1,2, Niranjan Venugopal, PhD3, Andrew Loblaw, MD, MSc1,2, Gerard Morton, MD1,2, Hans Chung, MD1,2, Laura D’Alimonte, BSc, MHSc1,2, Ananth Ravi, PhD1,2. 1Radiation Oncology, University of Toronto, Toronto, ON, Canada; 2Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada; 3 Saskatchewan Cancer Agency, Saskatoon, SK, Canada.
Abstracts / Brachytherapy 15 (2016) S21eS204
Comparison with other imaging modalities (Fig. 1) showed good agreement between US- and MR-based target D90 (!4 Gy EQD2 difference), but a large discrepancy between US and CT values, mainly due to overestimation of the CTVHR width on CT. Analysis of the TRUS/CT plan on MRI resulted in a clinically acceptable dose distribution.
fraction (EQD2). For the uniform dose (UD) method, the prescribed EBRT dose was added to the brachytherapy D2cc and D1cc. For the overlapping high dose method (OHD), the EBRT D2cc and D1cc was added to the brachytherapy D2cc and D1cc. Next, we performed two structure-based DIRs for each patient for the bladder and rectum separately, using the EBRT CT as the frame of reference. The FeatureBased Deformable Registration tool, available in a research version of Oncentra Brachy (Elekta Brachytherapy, Veenendaal, The Netherlands) was used for the DIR. For 3D addition of the doses with DIR, the transformation vectors were used to deform the EBRT dose distribution for each organ separately (Figure A, B). Next, the EBRT and brachytherapy doses were converted to EQD2 and summed voxel-byvoxel. The cumulative D2cc and D1cc in bladder and rectum were calculated and compared to the UD method and the OHD method. Results: The results are shown in Fig. C. Comparing the DIR method to either the UD method or the OHD method gave significantly different results. With the OHD method, the mean difference in D2cc and D1cc with 3D DIR was O1.1 GyEQD2, while the mean difference with the UD method was !0.4 GyEQD2. However, the difference between DIR and the other methods was small compared to the total cumulative D2cc and D1cc. Conclusions: The mean difference in D2cc and D1cc with the DIR method and the UD method or OHD method was small in the bladder and the rectum. However, the DIR method seems to provide added value to the OHD method in some cases, since the maximum difference with the DIR method could be as high as 3.2 GyEQD2. For the dose parameters under consideration, the EBRT dose can be considered uniform both in rectum and bladder when performing dose summation.
Figure 1. TRUS/CT planning workflow and comparison with other imaging modalities. Conclusions: During this feasibility study of a TRUS/CT treatment planning workflow for cervix cancer BT a full treatment could be simulated for one patient, resulting in a clinically acceptable dose distribution. A need for improved applicator localisation in TRUS volumes has been identified. Image registration accuracy could be improved by automatic applicator tracking during US acquisition, thus minimizing reconstruction uncertainties due to insufficient depiction of the whole applicator on US images.
PHSOR16 Presentation Time: 2:15 PM Potential Added Value of Structure-Based Deformable Image Registration for Dose Accumulation in External Beam Radiotherapy and Brachytherapy in Cervical Cancer Laura E. van Heerden, MSc, Anette C. Houweling, PhD, Kees Koedooder, PhD, Zdenko van Kesteren, PhD, Coen R.N. Rasch, MD, PhD, Bradley R. Pieters, MD, PhD, Arjan Bel, PhD. Radiation Oncology, Academic Medical Center, Amsterdam, Netherlands. Purpose: Advanced stage cervical cancer is commonly treated with a combination of external beam radiotherapy (EBRT) and a brachytherapy boost to the tumor area using an intracavitary applicator. In clinical practice, the cumulative D2cc and D1cc are calculated by simply adding the separate dose parameters, assuming that the EBRT dose can be considered uniform. Alternatively, it is assumed that the high dose volumes overlap for both treatments. To account for dose non-uniformity and deformation of the anatomy due to tumor shrinkage and organ movement in the cumulative dose parameters, it is preferable to sum the 3D dose distributions. Deformable image registration (DIR) can be applied to evaluate the total planned (biological equivalent) dose. The aim of this study is to determine the potential added value of DIR in the evaluation of cumulative dose parameters by testing if the clinically applied methods yield similar results. Materials and Methods: Twelve patients with cervical cancer, treated with a combination of EBRT (VMAT, 23 x 2Gy), planned on CT, and MRIguided PDR brachytherapy (24 x 1Gy, hourly) were retrospectively studied. Dose parameters were converted to equivalent dose in 2Gy per
Figure. A) MR image of a patient with the original brachytherapy bladder contour in red, and the warped EBRT bladder contour obtained with DIR in blue, B) Warped EBRT dose in the bladder region, C) The planned cumulative D2cc and D1cc calculated with the DIR method, the uniform dose method and the overlapping high dose method, and the difference DD2cc and DD1cc with the DIR method, in bladder and D) rectum. The mean and the range over all patients are shown.
PHSOR17 Presentation Time: 2:20 PM Evaluation of an Automated Deformable Registration Algorithm for MRI-Guided Focal Boost Integrated with Ultrasound-Based High-Dose Rate Brachytherapy in the Treatment of Prostate Cancer Joelle Helou, MD1,2, Amir Khojaste, PhD1,2, Niranjan Venugopal, PhD3, Andrew Loblaw, MD, MSc1,2, Gerard Morton, MD1,2, Hans Chung, MD1,2, Laura D’Alimonte, BSc, MHSc1,2, Ananth Ravi, PhD1,2. 1Radiation Oncology, University of Toronto, Toronto, ON, Canada; 2Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada; 3 Saskatchewan Cancer Agency, Saskatoon, SK, Canada.