ESTRO 2024 - Abstract Book

S5502

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

Patient factors impacting free-breathing motion magnitude and variability on MRI for radiotherapy.

Holly F Egan 1 , Ananya Choudhury 1,2 , Ganesh Radhakrishna 2 , Cynthia L Eccles 1,3 , Mairead Daly 1

1 University of Manchester, Faculty of Biology, Medicine and Health, Manchester, United Kingdom. 2 The Christie Hospitals NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom. 3 The Christie Hospitals NHS Foundation Trust, Radiotherapy, Manchester, United Kingdom

Purpose/Objective:

Respiratory motion is a challenge for stereotactic ablative body radiotherapy (SABR) of abdominal targets. Individual patient factors may impact the choice of respiratory motion management strategies. This project identified the impact of factors such as body mass index (BMI), age, sex, and presence of diabetes and cirrhosis on free breathing (FB) respiratory motion magnitude and variability.

Material/Methods:

Retrospective review of pancreas, liver, adrenal and abdominal node radiotherapy patients who underwent magnetic resonance imaging (MRI) under an institutional (QUANTUM, NCT0474809 (1)) and a multi-institution imaging study (PRIMER arms B & D (2)). Each patient underwent 1-3 imaging sessions, although only one session was used for this study. Each imaging session used a single-slice 3-plane balanced steady-state free procession gradient echo (bFFE) cine-MRI in both free breathing and with abdominal compression on a 1.5T MR Linac for motion quantification. Motion was quantified in the craniocaudal and medio-lateral directions on the coronal images. Rigid automatic registration of each of the subsequent cine images to the static first cine image was used to generate a pseudo-motion trace. Motion trace data was used to calculate amplitude. The interquartile range (IQR) was used to measure intra-fraction motion variability for each patient. Quartile (Q) 1+3 was calculated as a surrogate of motion magnitude variability. Data on participant sex, age, height, weight, diabetes, and cirrhosis status were collected and BMI calculated. Patients were subdivided by BMI based on the World Health Organisation (WHO) classification. To determine the influence of patient characteristics on magnitude and variation of respiratory motion, Mann Whitney U test for significance and two-tailed Spearman Rank Correlation were used.

Results:

16 patients were included, characteristics are presented in Table 1. Mean FB motion (mm) was higher for males than females in the craniocaudal (19.56mm and 12.55mm respectively, p=0.95) and medio-lateral (13.88mm and 2.55mm respectively, p=0.36) directions respectively. A stepwise increase in mean FB motion in the craniocaudal direction was observed for patients with normal, overweight, and obese BMIs (12.41mm, 19.44mm and 23.46mm respectively). There was a trend towards larger IQR with increasing BMI in craniocaudal and medio-lateral directions, although this was not statistically significant (r=0.11 and -0.33, respectively). Mean FB motion in the medio-lateral direction was largest in patients classified as overweight (18.77mm). For both craniocaudal and left-right directions, patients with cirrhosis had larger FB motion (Figure 1). Mean FB motion was higher in non-diabetic patients compared to diabetics. There was no correlation between BMI and craniocaudal (r=0.11) or medio-lateral (r=0.06) motion.