Quantification of inter-observer variation before and after an educational intervention in MRgRT
Rodgers, John Hales, Rosie Whiteside, L. Parker, J. McHugh, Louise Cree, Anthea Van Herk, Marcel Eccles, Cynthia L
Rodgers, John
Hales, Rosie
Whiteside, L.
Parker, J.
McHugh, Louise
Cree, Anthea
Van Herk, Marcel
Eccles, Cynthia L
Citations
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Abstract
Purpose or Objective
Accurate image registration is essential for magnetic
resonance (MR) guided online treatment adaptive
workflows (MRgRT). On-treatment MR-computed
tomography (CT) image registration is a novel method for
radiographers (RTTs) familiar with more established
imaging platforms such as conebeamCT. In treatment
sites demonstrating significant interfraction anatomical
variation, such as the cervix, image registration can be
particularly challenging. This work aims to validate the
use of a guide developed by RTTs to improve interobserver
variation for on-treatment image registration for
cervix plan of the day MRgRT.
Material and Methods
Off-line, retrospective soft tissue image registration was
undertaken by 4 RTTs for 10 cervical cancer patients
undergoing radiotherapy on an ethics-approved imaging
study. RTTs used the cervix to guide the registration of
T2w MR images to the planning CT in Monaco (v5.19.05
Research, Elekta, Stockholm, Sweden). Resulting
translations and RTT confidence scores for each
registration were used to determine inter-observer
variations. The exercise was repeated following the
creation of a registration guide (including a case study
atlas). This guide was developed collaboratively between
RTTs and diagnostic MR radiographers, in consultation with
clinicians, to identify the most relevant anatomic regions
for registration. The guide was used as a reference for
repeat registrations several weeks after the initial
exercise. The mean, standard deviation (SD) and range of
absolute difference among the three observers in right-left
(RL), superior-inferior (SI) and anterior-posterior (AP)
directions for each registration were calculated.
Results
Less variability was observed for MR-CT registrations when
radiographers referenced a detailed registration protocol
compared to matching the cervix alone. The interobserver
mean, SD and range improved for all
directions. Details can be found in table 1. Comparison
by paired t-test of results before and after the use of the
registration guide showed statistically significant
differences for both the SI (p = 0.003) and AP directions (p
= 0.001). Additionally, RTT confidence in registrations,
using a Likert scale (1-5), improved from a mean score of
3.2 prior to the intervention to 3.9 following the use of the
registration protocol.
Conclusion
This study has demonstrated the importance for
radiographers operating in MGgRT to develop and evaluate
robust consensus driven image registration procedures.
These protocols aim to minimise uncertainty in image
matching and ensure consistent and accurate treatment.
Affiliation
Description
Date
2020
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Rodgers J, Hales R, Whiteside L, Parker J, McHugh L, Cree A, et al. PO-1899: Quantification of inter-observer variation before and after an educational intervention in MRgRT. Radiotherapy and Oncology . 2020 Nov;152:S1059