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The Australian Clinical Dosimetry Service (ACDS) plans to implement an end-to-end dosimetric audit encompassing respiratory motion management (MM). The audit design will be informed by a survey of motion management techniques used at Australian and New Zealand radiation therapy (RT) facilities.

The survey was distributed via REDCap (v10.8) to all ACDS-subscribed facilities. The survey aimed to capture the extent to which different MM techniques were utilised, as well as how each of them were implemented practically in the clinic. Five techniques were considered (breath-hold gating (BHG), internal target volume (ITV), free-breathing gating (FBG), mid-ventilation (MidV), and tumour tracking (TT)), across three main stereotactic ablative body radiation (SABR) treatment locations (lung/thorax, liver/upper abdomen, and kidney/lower abdomen). For each combination of MM technique and site, participants described specific practices including use of motion limitation (compression or ventilation), types of imaging available for motion assessment, and dataset used for dosimetric calculation. Responses were extracted from REDCap, anonymised and analysed with Python (v3.8).

The survey was completed by 78% of facilities in the region, with 98% of respondents indicating that they use at least one form of MM. The ITV approach was common to all MM-users, used for thoracic treatments by 89% of respondents, upper abdominal treatments by 38%, and lower abdominal treatments by 38%. BHG was the next most prevalent (41% MM users), with applications in upper abdominal and thoracic treatment sites (28% vs 25% MM users respectively), but minimal use in the lower abdomen (9%). FBG and TT were utilised sparingly (17%, 7% of MM users respectively), and MidV was not selected at all. Motion limitation used in upper abdominal treatments in more than 50% of facilities, but was used sparingly outside this. Upper abdominal SABR sites also saw a more prevalent use of external imaging modalities including contrast CT and MRI for pre-treatment motion assessment. Choice of planning dataset for dose calculation was largely determined by choice of MM technique – breath-hold CT for BHG, 4DCT average intensity projection for ITV, rather than by treatment site.

The survey showed that some MM techniques (ITV, BHG) are widely used for the thorax and upper abdomen, but are implemented in different ways. A MM audit thus must include ITV and BHG applied to these anatomical treatment sites but ideally be adaptable to different combinations of treatment site and MM techniques. Further, the audit will not be prescriptive in details critical to accurate treatments incorporating MM such as target delineation and choice of dose calculation dataset.