Susanne Rylander1, Simon Buus2, Erik M Pedersen3, Lise Bentzen2, Kari Tanderup4. 1. Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark; Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark. Electronic address: susaryla@rm.dk. 2. Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 3. Department of Radiology, Aarhus University Hospital, Aarhus, Denmark. 4. Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark; Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.
Abstract
BACKGROUND AND PURPOSE: The purpose was to evaluate the dosimetric impact of target contouring and needle reconstruction uncertainties in an US-, CT- and MRI-based HDR prostate BT treatment planning. MATERIAL AND METHODS: US, CT, and MR images were acquired post-needle insertion in 22 HDR-BT procedures for 11 consecutive patients. Dose plans were simulated for an US-, CT- and MRI-based HDR-BT treatment planning procedure. Planning uncertainties in US- and CT-based plans were evaluated using MRI-based planning as reference. Target (CTVProstate) was re-contoured on MRI. Dose results were expressed in total equivalent dose given in 2Gy fractionation dose for EBRT (46Gy) plus 2 HDR-BT fractions. RESULTS: Uncertainties in US- and CT-based planning caused the planned CTVProstate-D90% to decrease with a mean of 2.9±5.0Gy (p=0.03) and 2.9±2.9Gy (p=0.001), respectively. The intra-observer contouring variation on MRI resulted in a mean variation of 1.6±1.5Gy in CTVProstate-D90%. Reconstruction uncertainties on US resulted in a dose variation of±3Gy to the urethra, whereas data for CT were not available for this. CONCLUSIONS: Uncertainties related to contouring and reconstruction in US- and CT-based HDR-BT treatment plans resulted in a systematic overestimation of the prescribed target dose. Inter-modality uncertainties (US and CT versus MR) were larger than MR intra-observer uncertainties.
BACKGROUND AND PURPOSE: The purpose was to evaluate the dosimetric impact of target contouring and needle reconstruction uncertainties in an US-, CT- and MRI-based HDR prostate BT treatment planning. MATERIAL AND METHODS: US, CT, and MR images were acquired post-needle insertion in 22 HDR-BT procedures for 11 consecutive patients. Dose plans were simulated for an US-, CT- and MRI-based HDR-BT treatment planning procedure. Planning uncertainties in US- and CT-based plans were evaluated using MRI-based planning as reference. Target (CTVProstate) was re-contoured on MRI. Dose results were expressed in total equivalent dose given in 2Gy fractionation dose for EBRT (46Gy) plus 2 HDR-BT fractions. RESULTS: Uncertainties in US- and CT-based planning caused the planned CTVProstate-D90% to decrease with a mean of 2.9±5.0Gy (p=0.03) and 2.9±2.9Gy (p=0.001), respectively. The intra-observer contouring variation on MRI resulted in a mean variation of 1.6±1.5Gy in CTVProstate-D90%. Reconstruction uncertainties on US resulted in a dose variation of±3Gy to the urethra, whereas data for CT were not available for this. CONCLUSIONS: Uncertainties related to contouring and reconstruction in US- and CT-based HDR-BT treatment plans resulted in a systematic overestimation of the prescribed target dose. Inter-modality uncertainties (US and CT versus MR) were larger than MR intra-observer uncertainties.
Authors: Nicholas G Zaorsky; Brian J Davis; Paul L Nguyen; Timothy N Showalter; Peter J Hoskin; Yasuo Yoshioka; Gerard C Morton; Eric M Horwitz Journal: Nat Rev Urol Date: 2017-06-30 Impact factor: 14.432
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