Development of three-dimensional transperineal ultrasound for image-guided radiation therapy of the prostate: Early evaluations of feasibility and use for inter- and intrafractional prostate localization

Publication date: Available online 2 September 2016
Source:Practical Radiation Oncology
Author(s): Apoorva Trivedi, Takamura Ashikaga, Daphne Hard, Jessica Archambault, Martin Lachaine, David T. Cooper, Harold James Wallace
Transperineal ultrasound (TPUS) allows for continuous imaging of the prostate gland, but the accuracy of TPUS has not been rigorously studied. We determined the feasibility of prostate imaging with TPUS and subsequently compared prostate localization with TPUS and Computed Tomography (CT).Methods and MaterialsWe completed two sequential evaluations of TPUS. The feasibility study included 15 men with localized prostate cancer and tested if TPUS adequately imaged the prostate. Image qualities of the prostate and adjacent normal structures were measured. The subsequent study included 17 men who at the time of initial radiation treatment planning and in three subsequent sessions had CT and TPUS imaging performed and compared.ResultsFeasibility of TPUS was confirmed in the first trial. After expected hardware and software modifications were completed, TPUS provided near complete edge definition of the prostate in the final 5 patients in the feasibility trial. The second study allowed for the comparison of 30 image sets. The differences between TPUS and CT in each direction (mean+standard deviation) were found to be 0.06±2.86mm (A/P), 0.49±3.49mm (S/I), and 0.63±3.27mm (L/R), with no significant difference between the two modalities (all p's>0.32). The Euclidean distance variance using the two techniques was 5.25±1.79mm, which was significantly different.ConclusionsTPUS provides good imaging of the prostate gland. We noted excellent correlation in gland localization when TPUS is compared to CT when comparing routine three-dimensional positional data. Euclidean distance variation suggests the potential that summation of small errors may in fact lead to significant differences in actual gland positional certainty. The reported difference is within the range of standard planning target volume (PTV) expansion however requires additional evaluation.



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