Quantification of fat on MRI and impact on effectiveness of abdominal compression for radiotherapy
Daly, M. Benson, Rebecca Chuter, Robert Clough, Abigael McDaid, Lisa McWilliam, Alan Nelder, Claire L Pitt, Eleanor Radhakrishna, Ganesh Choudhury, Ananya
Daly, M.
Benson, Rebecca
Chuter, Robert
Clough, Abigael
McDaid, Lisa
McWilliam, Alan
Nelder, Claire L
Pitt, Eleanor
Radhakrishna, Ganesh
Choudhury, Ananya
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Abstract
Purpose or Objective
High body mass index (BMI) has been identified as a factor in reduced abdominal compression effectiveness, however, does
not consider body composition or fat distribution. Patients with higher levels of abdominal subcutaneous adipose tissue
(SAT) may have reduced effectiveness of abdominal compression, due to attenuation of the compression force.
Quantification of SAT on cross-sectional imaging, including diagnostic MRI, is used as a biomarker in metabolic conditions
such as diabetes. This work quantified SAT percentage fat fraction (%FF) using MRI acquired on a MR-Linac and identified
the optimal point for quantification of abdominal SAT for radiotherapy motion management. The impact of SAT levels on
reduction of respiratory motion with abdominal compression for radiotherapy was also investigated.
Materials and Methods
Eight participants (6 patients and 2 healthy volunteers) were imaged on a 1.5T MR-Linac as part of an institutional study.
T2-weighted 3D MRI and cine-MRI were acquired with and without an abdominal compression belt. External contour and
SAT were segmented retrospectively on a single slice at three points: the junction of vertebral levels T12/L1, L1/2, and
L2/L3. The inner and outer boundaries for SAT were defined as the external border of skeletal muscle, and the external
contour respectively. Images were segmented and evaluated by an experienced therapeutic radiographer (RTT). %FF (SAT
volume relative to external contour volume) was calculated. Respiratory motion, defined as craniocaudal motion of the
central apex of the liver from highest to lowest point was measured on coronal cine-MRI averaged across three breathing
cycles. Bivariable correlation analysis was used to evaluate the relationship between %FF and change in amplitude with
compression at each vertebral level, as well as the relationship between %FF and BMI.
Results
Median BMI was 27.9 (range, 25.3 – 38.0), and all participants were considered overweight or obese. Seven out of eight
participants saw a reduction in peak-to-peak liver apex motion with abdominal compression (Table 1). One patient
volunteer saw an increase of 0.62 mm from 5.12 mm (BMI 26.1, %FF 41.5). Change in motion amplitude was strongly
correlated with initial motion (r = 0.85). %FF showed strongest correlation with BMI at the level of T12/L1 (r = 0.61). %FF
at T12/L1 and L2/3 had a moderate negative correlation with amplitude change with abdominal compression. Conclusion
Single-slice SAT measurements on MR images acquired on the MR-Linac are feasible. SAT %FF demonstrated a stronger
relationship with amplitude change with abdominal compression than BMI, particularly at the level T12/L1. In patients
with smaller initial motion (≤ 5 mm), care should be taken when using abdominal compression as increases in liver motion
are possible. This work will be validated on a larger cohort as part of ongoing work.
Description
Date
2022
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Daly M, Benson R, Chuter R, Clough A, McDaid L, McWilliam A, et al. Quantification of fat on MRI and impact on effectiveness of abdominal compression for radiotherapy. Radiotherapy and Oncology. 2022 May;170:S1627-S8. PubMed PMID: WOS:000806779900650.