Improving fiducial and prostate capsule visualization for radiotherapy planning using MRI.
Abstract
BACKGROUND AND PURPOSE: Intraprostatic fiducial markers (FM) improve the accuracy of radiotherapy (RT) delivery. Here we assess geometric integrity and contouring consistency using a T2*-weighted (T2*W) sequence alone, which allows visualization of the FM. MATERIAL AND METHODS: Ten patients scanned within the Prostate Advances in Comparative Evidence (PACE) trial (NCT01584258) had prostate images acquired with computed tomography (CT) and Magnetic Resonance (MR) Imaging: T2-weighted (T2W) and T2*W sequences. The prostate was contoured independently on each imaging dataset by three clinicians. Interobserver variability was assessed using comparison indices with Monaco ADMIRE (research version 2.0, Elekta AB) and examined for statistical differences between imaging sets. CT and MR images of two test objects were acquired to assess geometric distortion and accuracy of marker positioning. The first was a linear test object comprising straight tubes in three orthogonal directions, the second was a smaller test object with markers suspended in gel. RESULTS: Interobserver variability for prostate contouring was lower for both T2W and T2*W compared to CT, this was statistically significant when comparing CT and T2*W images. All markers are visible in T2*W images with 29/30 correctly identified, only 3/30 are visible in T2W images. Assessment of geometric distortion revealed in-plane displacements were under 0.375 mm in MRI, and through plane displacements could not be detected. The signal loss in the MR images is symmetric in relation to the true marker position shown in CT images. CONCLUSION: Prostate T2*W images are geometrically accurate, and yield consistent prostate contours. This single sequence can be used to identify FM and for prostate delineation in a mixed MR-CT workflow.
Collections
Subject
Humans
Prostatic Neoplasms
Observer Variation
Tomography, X-Ray Computed
Magnetic Resonance Imaging
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Image Processing, Computer-Assisted
Male
Radiotherapy, Intensity-Modulated
Fiducial Markers
Radiotherapy, Image-Guided
Biomarkers
Research team
Stereotactic and Precision Body Radiotherapy
Language
eng
Date accepted
2018-12-10
License start date
2019-03
Citation
Journal of applied clinical medical physics, 2019, 20 (3), pp. 27 - 36
Publisher
WILEY
Except where otherwise noted, this item's license is described
as
https://creativecommons.org/licenses/by/4.0
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