Jones, Lowri, Oliver, Lauren 
ORCID: 0000-0001-5816-5498, Callender, Jenny and Kirby, Michael ORCID: 0000-0001-9765-5641
(2022)
A service evaluation of 2D planar vs 3D volumetric on-treatment verification for radiotherapy to the upper gastrointestinal tract.
[Poster]
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LJ LO JC MCK BIRTO22 poster FINAL2.pdf - Unspecified Download (345kB) | Preview |
Abstract
INTRODUCTION On-treatment verification using image-guided radiotherapy (IGRT) techniques is fundamental in upper GI radiotherapy for ensuring treatment accuracy. Strategies may include 2D kV planar and 3D kV volumetric cone-beam computed tomography (CBCT) imaging, but required frequencies are under debate. There is currently no national UK imaging standard with many departments adopting their own local protocols. Therefore, understanding potential differences between the modalities and their impact on plan objectives is important. METHODS The aim of this service evaluation was to determine the validity of 2D kV planar imaging compared with 3D volumetric kV-CBCT imaging for correcting patient set-up errors. This was investigated through retrospective assessment of various region of interest (ROI) boxes on 150 CBCT images of 50 patients, by examining any significant differences between bony anatomy and soft tissue matching. Discrepancies in different translational parameters and anatomical distinctions were calculated and a pilot dosimetric assessment was conducted to determine whether 2D kV planar imaging was sufficient or whether daily 3D kV CBCT imaging was warranted to meet plan objectives. RESULTS The key findings of this study were; (a) Inter-observer variability when conducting a bone match is minimal. (b) The greatest difference in patient set-up error correction between a bone and soft tissue match, occurred in the longitudinal direction, for patients with tumours of the lower oesophagus and GOJ/stomach. (c) Only a small percentage of patients required a re-plan or a change to daily CBCT imaging during their treatment course. (d) Only 14% of the overall study cohort had a mean systematic difference in couch shifts between the bone and soft tissue match of +/-0.3cm or greater over the course of treatment. (e) The pilot dosimetry assessment showed that even for the ‘worst-case’ mean systematic difference reported between a bone and soft tissue match, a bone match was sufficient to achieve plan objectives. CONCLUSION The acquisition of 2D kV planar images is a quick and straightforward method of performing on-treatment verification and can be considered an accurate modality for the correction of patient set-up errors in upper GI radiotherapy. Although the value of kV-CBCT imaging for providing indispensable soft tissue detail is well understood, the evidence suggests that the additional concomitant dose factor may not be justified for daily use in this patient group if not deemed absolutely necessary and that kV planar imaging is a sufficient alternative that can be conducted with a reduced dose to the patient.
| Item Type: | Poster |
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| Divisions: | Faculty of Health and Life Sciences Faculty of Health and Life Sciences > Institute of Population Health Faculty of Health and Life Sciences > Institute of Population Health > School of Health Sciences |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 21 Apr 2022 07:48 |
| Last Modified: | 18 Jan 2023 21:04 |
| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3153528 |
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