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Lookup NU author(s): JJ Wyatt, Dr George Petrides, Dr Rachel Pearson, Dr Hazel McCallum, Dr Ross Maxwell
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2023 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.Background: Positron Emission Tomography-Magnetic Resonance (PET-MR) scanners could improve ano-rectal radiotherapy planning through improved Gross Tumour Volume (GTV) delineation and enabling dose painting strategies using metabolic measurements. This requires accurate quantitative PET images acquired in the radiotherapy treatment position. Purpose: This study aimed to evaluate the impact on GTV delineation and metabolic parameter measurement of using novel Attenuation Correction (AC) maps that included the radiotherapy flat couch, coil bridge and anterior coil to see if they were necessary. Methods: Seventeen ano-rectal radiotherapy patients received a 18F-FluoroDeoxyGlucose PET-MR scan in the radiotherapy position. PET images were reconstructed without (CTACstd) and with (CTACcba) the radiotherapy hardware included. Both AC maps used the same Computed Tomography image for patient AC. Semi-manual and threshold GTVs were delineated on both PET images, the volumes compared and the Dice coefficient calculated. Metabolic parameters: Standardized Uptake Values SUVmax, SUVmean and Total Lesion Glycolysis (TLG) were compared using paired t-tests with a Bonferroni corrected significance level of (Formula presented.). Results: Differences in semi-manual GTV volumes between CTACcba and CTACstd were approaching statistical significance (difference (Formula presented.), (Formula presented.)), with larger differences in low FDG-avid tumours ((Formula presented.)). The CTACcba and CTACstd GTVs were concordant with Dice coefficients 0.89 ± 0.01 (manual) and 0.98 ± 0.00 (threshold). Metabolic parameters were significantly different, with SUVmax, SUVmean and TLG differences of (Formula presented.) ((Formula presented.)), (Formula presented.) ((Formula presented.)) and (Formula presented.) ((Formula presented.)) respectively. The TLG difference resulted in 1/8 rectal cancer patients changing prognosis group, based on literature TLG cut-offs, when using CTACcba rather than CTACstd. Conclusions: This study suggests that using AC maps with the radiotherapy hardware included is feasible for patient imaging. The impact on tumour delineation was mixed and needs to be evaluated in larger cohorts. However using AC of the radiotherapy hardware is important for situations where accurate metabolic measurements are required, such as dose painting and treatment prognostication.
Author(s): Wyatt JJ, Petrides G, Pearson RA, McCallum HM, Maxwell RJ
Publication type: Article
Publication status: Published
Journal: Journal of Applied Clinical Medical Physics
Year: 2024
Volume: 25
Issue: 3
Print publication date: 01/03/2024
Online publication date: 03/11/2023
Acceptance date: 11/10/2023
Date deposited: 21/11/2023
ISSN (electronic): 1526-9914
Publisher: John Wiley and Sons Ltd
URL: https://doi.org/10.1002/acm2.14193
DOI: 10.1002/acm2.14193
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