MRI-guided prostate radiation therapy planning: Investigation of dosimetric accuracy of MRI-based dose planning

Lambert, Jonathan, Greer, Peter B., Menk, Fred, Patterson, Jackie, Parker, Joel, Dahl, Kara, Gupta, Sanjiv, Capp, Anne, Wratten, Chris, Tang, Colin, Kumar, Mahesh, Dowling, Jason, Hauville, Sarah, Hughes, Cynthia, Fisher, Kristen, Lau, Peter, Denham, James W. and Salvado, Olivier (2011) MRI-guided prostate radiation therapy planning: Investigation of dosimetric accuracy of MRI-based dose planning. Radiotherapy and Oncology, 98 3: 330-334. doi:10.1016/j.radonc.2011.01.012

Author Lambert, Jonathan
Greer, Peter B.
Menk, Fred
Patterson, Jackie
Parker, Joel
Dahl, Kara
Gupta, Sanjiv
Capp, Anne
Wratten, Chris
Tang, Colin
Kumar, Mahesh
Dowling, Jason
Hauville, Sarah
Hughes, Cynthia
Fisher, Kristen
Lau, Peter
Denham, James W.
Salvado, Olivier
Title MRI-guided prostate radiation therapy planning: Investigation of dosimetric accuracy of MRI-based dose planning
Journal name Radiotherapy and Oncology   Check publisher's open access policy
ISSN 0167-8140
Publication date 2011-03
Sub-type Article (original research)
DOI 10.1016/j.radonc.2011.01.012
Volume 98
Issue 3
Start page 330
End page 334
Total pages 5
Place of publication Shannon, Co. Clare, Ireland
Publisher Elsevier Ireland
Collection year 2012
Language eng
Formatted abstract
Background and purpose: Dose planning requires a CT scan which provides the electron density distribution for dose calculation. MR provides superior soft tissue contrast compared to CT and the use of MR alone for prostate planning would provide further benefits such as lower cost to the patient. This study compares the accuracy of MR-alone based dose calculations with bulk electron density assignment to CTbased dose calculations for prostate radiotherapy.

Materials and methods:
CT and whole pelvis MR images were contoured for 39 prostate patients. Plans with uniform density and plans with bulk density values assigned to bone and tissue were compared to the patient’s gold standard full density CT plan. The optimal bulk density for bone was calculated using effective depth measurements. The plans were evaluated using ICRU point doses, dose volume histograms, and Chi comparisons. Differences in spatial uniformity were investigated for the CT and MR scans.

The calculated dose for CT bulk bone and tissue density plans was 0.1 ± 0.6% (mean ± 1 SD) higher than the corresponding full density CT plan. MR bulk bone and tissue density plans were 1.3 ± 0.8% lower than the full density CT plan. CT uniform density plans and MR uniform density plans were 1.4 ± 0.9% and 2.6 ± 0.9% lower, respectively. Paired t-tests performed on specific points on the DVH graphs showed that points on DVHs for all bulk electron density plans were equivalent with two exceptions. There was no significant difference between doses calculated on Pinnacle and Eclipse. The dose distributions of six patients produced Chi values outside the acceptable range of  values when MR-based plans were compared to the full density plan.

Conclusions: MR-alone bulk density planning is feasible provided bone is assigned a density, however, manual segmentation of bone on MR images will have to be replaced with automatic methods. The major dose differences for MR bulk density plans are due to differences in patient external contours introduced by the MR couch-top and pelvic coil.
Keyword Radiotherapy treatment planning
Prostate cancer
Electron density
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Non HERDC
School of Information Technology and Electrical Engineering Publications
Centre for Advanced Imaging Publications
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Citation counts: TR Web of Science Citation Count  Cited 35 times in Thomson Reuters Web of Science Article | Citations
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