Technical Note: Efficient and accurate MRI‐only based treatment planning of the prostate using bulk density assignment through atlas‐based segmentation

Purpose This study investigates the dosimetric accuracy as well as the robustness of a bulk density assignment approach to magnetic resonance imaging (MRI)‐only based treatment planning of the prostate, with bulk density regions automatically identified using atlas‐based segmentation (ABS). Methods...

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Bibliographic Details
Published in:Medical physics (Lancaster) 2020-10, Vol.47 (10), p.4758-4762
Main Authors: McCallum, Hazel Mhairi, Andersson, Sebastian, Wyatt, Jonathan James, Richmond, Neil, Walker, Christopher Paul, Svensson, Stina
Format: Article
Language:English
Subjects:
atlas‐based segmentation
bulk density assignment
Humans
magnetic resonance
Magnetic Resonance Imaging
Male
MRI‐only based radiotherapy
Prostate
prostate patients
Prostatic Neoplasms - diagnostic imaging
Prostatic Neoplasms - radiotherapy
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Intensity-Modulated
VMAT
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Summary:Purpose This study investigates the dosimetric accuracy as well as the robustness of a bulk density assignment approach to magnetic resonance imaging (MRI)‐only based treatment planning of the prostate, with bulk density regions automatically identified using atlas‐based segmentation (ABS). Methods Twenty prostate radiotherapy patients received planning computed tomography (CT) and MRI scans and were treated with volumetric modulated arc therapy (VMAT). Two bulk densities were set, one for bone and one for soft tissue. The bone contours were created by using ABS followed by manual modification if considered necessary. A range of soft tissue and bone density pairs, between 0.95 and 1.03 g/cm3 with increments of 0.01 for soft tissue, and between 1.15 and 1.65 g/cm3 with increments of 0.05 for bone, were evaluated. Using the density pair giving the lowest dose difference compared to the CT‐based dose, dose differences were calculated using both the manually modified bone contours and the bone contours from ABS. Contour overlap measurements between the ABS contours and the manually modified contours were calculated. Results The dose comparison shows a very good agreement with the CT when using 0.98 g/cm3 for soft tissue and 1.20 g/cm3 for bone, with a dose difference less than 1 % in average dose in all regions of interest. The mean Dice similarity coefficient for bone was 0.94 and the Mean Distance to Agreement was
ISSN:0094-2405
2473-4209
DOI:10.1002/mp.14406