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TU‐EE‐A3‐06: Comparison of Prostate Localization with Online Ultrasound and Mega‐Voltage Cone‐Beam Computed Tomography
Journal article   Peer reviewed

TU‐EE‐A3‐06: Comparison of Prostate Localization with Online Ultrasound and Mega‐Voltage Cone‐Beam Computed Tomography

M Miften, O Gayou, B Reitz, R Fuhrer and D Parda
Medical physics (Lancaster), v 34(6), pp 2565-2565
Jun 2007
DOI: https://doi.org/10.1118/1.2761415

Abstract

Purpose: To analyze the online image‐guided localization data from 846 ultrasound (US)and 350 MV‐CBCT couch alignments for patients undergoing IMRT of the prostate. Method and Materials: Daily volumetric MV‐CBCT and US images were acquired for 11 and 23 patients, respectively, after each patient was immobilized in a vacuum cradle and setup to skin markers as the center‐of‐mass. The couch shifts applied in the lateral (left‐right/LR), vertical (anterior‐posterior/AP), and longitudinal (superior‐inferior/SI) directions, along with the magnitude of the three‐dimensional (3D) shift vector, were analyzed and compared for both methods. The percentage of shifts larger than 5 mm in all directions was also compared. CTV‐to‐PTV expansion margins were estimated based on the localization data with US and CB image‐guidance. Results: Systematic and random shifts from CB versus US were: laterally, 1.6 ± 3.8 mm vs. − 0.7 ± 6.9 mm; vertically, − 0.9 ± 5.4 mm vs. − 0.2 ± 6.4 mm; longitudinally, −1.4 ± 2.9 mm vs. −2.9 ± 5.2 mm. The mean 3D shift distance was smaller using CB (6.6 ± 3.6 mm vs. 9.1 ± 6.5 mm) with a p‐value < 0.05. The US data show greater variability. The percentage of US shifts larger than 5 mm were 33%, 40%, and 31% in the LR, AP, and SI directions, respectively, compared to 17%, 31%, and 7% for CB. Conclusion: MV‐CBCT localization data suggest a different distribution of prostate center‐of‐mass shifts with smaller variability, compared to US. The online MV‐CBCT image‐guidance data show that for treatments that do not include daily prostate localization,one can use a CTV‐to‐PTV margin that is 2.5 mm smaller than the one suggested by US data,hence allowing more rectum and bladder sparing and potentially improving the therapeutic ratio.

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Collaboration types
Domestic collaboration
Web of Science research areas
Radiology, Nuclear Medicine & Medical Imaging
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