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Assessment of an ultrasound bladder scanner in prostate radiotherapy: A validation study and analysis of bladder filling variability

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journal contribution
posted on 27.05.2021, 11:51 by L Smith, J Gittins, K Ramnarine, EML Chung
Introduction
During prostate radiotherapy treatment, it is important to ensure the position of the bladder and prostate is consistent between treatments. The aim of this study was to provide a quantitative basis for incorporating ultrasound bladder volume estimates into local practice for prostate radiotherapy.

Methods
Agreement between bladder volume estimates obtained using computed tomography (CT) and ultrasound was assessed. Analysis of bladder volumes between planning and treatment scans was used to quantify expected variations in bladder volume over the course of radiotherapy. Dose–volume statistics were estimated and compared to planned dose constraints to propose a target bladder volume and tolerance.

Results
Bladder volume measurements were obtained from 19 radiotherapy patients using ultrasound and CT. Ultrasound underestimated bladder volume compared to CT with a mean bias of –28 ± 30 ml. Pre-treatment (planning) bladder volumes varied from 71 to 383 ml with a mean of 200 ml. Treatment bladder volumes reduced by more than half in 9% of patients during the course of their treatment, potentially leading to a 30% increase in mean bladder dose. Patients with pre-treatment bladder volumes < 200 ml were most likely to exhibit differences in bladder volume, resulting in ‘out of tolerance’ increases in dose.

Conclusions
A pragmatic individualised drinking protocol, aimed at achieving a minimum ultrasound bladder volume of 200 ml at planning CT, may be beneficial to reproducibility in radiotherapy treatment. Ultrasound measurements prior to treatment should ideally confirm that bladder volume is at least half the volume measured at planning.

History

Author affiliation

Department of Cardiovascular Sciences

Version

AM (Accepted Manuscript)

Published in

Ultrasound

Publisher

SAGE Publications

issn

1742-271X

eissn

1743-1344

Acceptance date

26/01/2021

Copyright date

2021

Available date

27/05/2021

Language

English