Leaf open time sinogram (LOTS): a novel approach for patient specific quality assurance of total marrow irradiation
- PDF / 1,203,851 Bytes
- 12 Pages / 595.276 x 790.866 pts Page_size
- 42 Downloads / 133 Views
Open Access
RESEARCH
Leaf open time sinogram (LOTS): a novel approach for patient specific quality assurance of total marrow irradiation Rajesh Thiyagarajan1,4, Dayananda Shamurailatpam Sharma1* , Suryakant Kaushik1, Mayur Sawant1, K. Ganapathy1, N. Arunai Nambi Raj3, Srinivas Chilukuri2, Sham C. Sundar2, Kartikeswar Ch. Patro1, Arjunan Manikandan1, M. P. Noufal1, Rangasamy Sivaraman1, Jose Easow5 and Rakesh Jalali2
Abstract There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for Total Marrow (TMI) and Lymphoid (TMLI) Irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured Leaf Open Time Sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with (a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and (b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98% ( D98%) and 2% (D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ± 1.80% of planned and IC measurement. The planned dose distribution agreed with reconstructed and ArcCheck measured dose with mean (SD) 3Dγ of 98.70% (1.57%) and 2Dγ of 99.48% (0.81%). The deviation in D98% and D2% were within 1.71% and 4.10% respectively. In all 25 measurement locations from TMI/ TMLI patients, planned and IC measured absolute dose agreed within ± 1.20%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from the five upper body TMI/TMLI plans showed mean ± SD 2Dγ of 97.82% ± 1.27%, the reconstruction method resulted poor mean (SD) 3Dγ of 92.00% (± 5.83%), 64.80% (± 28.28%), 69.20% (± 30.46%), 60.80% (± 19.37%) and 73.2% (± 20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were 90%) except P12. The 3Dγ values (28%-94%) of PTV Chest of every patient were much lesser than corresponding 2Dγ (> 96%) estimated from ArcCHECK measurement. For reasons not clear to us, we observed poor 3Dγ values from the analysis of the first patient (P11) itself. In an attempt to remove any possible error, we carried out a series of investigations including various email communication and data sharing with Accuray Medical Physics support team based in Europe. MVCT detector output was re-calibrated and baselined again following recommended protocol described in the manual. As per the suggestions from Accuray medical physics support,
Thiyagarajan et al. Radiat Oncol
(2020) 15:236
Page 9 of 12
Table 4 3D gamma (γ%) values resulted from the comparison of planned and reconstructed dose distribution in 6 planning target volumes (PTVs) and two external (body) from the two plans (upper body and lower body) of every TMI/ TMLI patients. 3Dγ values of 3%@3mm from the original plans
Data Loading...
