ABSTRACT
INTRODUCTION: Radiotherapy outcomes are influenced by treatment delivery geometric accuracy and organ-at-risk dose. The location of abdominal structures such as the liver, kidneys and tumour volumes can be strongly influenced by respiratory motion. This increases geometric uncertainty and dose to organs-at-risk. One common method of minimising respiratory motion is abdominal compression (AC). METHODS: Fifteen patients being treated for radiotherapy to upper abdominal tumours were analysed. Each patient underwent 2 four-dimensional computerised tomography (4D-CT) scans, one with and one without AC with a pneumatic compression belt. Liver and kidney positions were measured on the 4DCT scans at the peak inspiratory and expiratory respiratory phases. The patient received radiation therapy treatment planned on the CT data set with the technique (compression or no compression) that provided the least respiratory motion. RESULTS: There was no statistically significant motion difference over the sample population with AC for the kidneys or liver. Of the 14 evaluable patients, 4, 6 and 6 saw reduction in superior-inferior motion for left kidney, right kidney and liver respectively. The remainder either had negligible (<2 mm) or increase in motion with AC. For anterior-posterior motion, 2, 2 and 1 saw a reduction for left-kidney, right-kidney and liver respectively. CONCLUSION: AC through the use of a pneumatic compression belt was found to result in inconsistent reduction in kidney and liver respiratory motion. It is recommended that the effect of AC is evaluated on a per-patient basis.