Comparison of Two Transabdominal Ultrasound Image Guidance Systems for Prostate and Prostatic Fossa Radiotherapy

Publication date: Available online 8 July 2016
Source:Practical Radiation Oncology
Author(s): Bill J. Salter, Martin Szegedi, Christine Boehm, Vikren Sarkar, Prema Rassiah-Szegedi, Brian Wang, Hui Zhao, Jessica Huang, Long Huang, Kris Kokeny, Jonathan D. Tward
PurposeOur clinic is a long-term user of a 1^stgeneration transabdominal (TA) Bi-Planar (2.5D) Ultrasound Image Guidance (USIG) system for prostate cancer treatments. We are also an early adopter and development partner for a new, second generation, fully 3D USIG system which allows for volumetric TA localization of the prostate. This new system has been evaluated at our institution by direct comparison with the previously established 1st generation TA method for prostate alignment.Methods and MaterialsWe compared the two TA-USIG methods on the same subjects, same treatment sessions. 1428 fractions delivered to 41 treated patients (16 intact prostate, 25 fossa) were analyzed regarding the agreement of alignments between the two US positioning systems. Patients were first aligned to tattoos using treatment room lasers. TA-USIG using the 3D system was then performed to align contours derived during the CT simulation process to their corresponding daily ultrasound-visualized structures. The US-3D system image guidance shifts were performed and recorded as the "initial" shifts. A 2.5D system alignment was then immediately performed using the same CT derived reference contours and the indicated shifts, relative to the 3D system, were recorded as the difference between the two alignment methods.ResultsThe average difference between the two TA-USIG alignments for all patients was 0.4±0.7mm, 0.7±0.9mm, and 0.5±0.9mm in the left–right, anterior–posterior, and superior–inferior directions, respectively. No significant difference in system agreement between intact prostate versus fossa patients was observed.ConclusionOur comparison of an established 2.5D USIG method with a newer, fully 3D approach for prostate alignment of 41 different patients (1428 fractions) shows excellent agreement with each other, despite the non-trivial difference in imaging approaches. This shows that the two specific USIG approaches yield results that are consistent with each other, and that the USIG modality yields consistent results within the modality.



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