Purpose: The aim of this study was to assess the variation of probe rotation angles for detecting a single needle using sagittal images of transrectal ultrasonography (TRUS).
Materials and methods: A phantom study was performed. One needle was inserted through each of 10 holes of the template, and variations in the probe rotation angles for detecting the needle were measured.
Results: The mean variation of probe rotation for detecting a single needle was 17.0 degrees (range 4 degrees -25 degrees ). Slightly broader variation was seen for the needle in holes farther away from the probe.
Conclusion: Probe rotation angles for detecting a single needle displayed considerable variation. Seed locations recognized on sagittal imaging by TRUS are thus indeterminate, and real-time dose calculations using TRUS for (125)I seed implantation should be used with care.