AbstractID: 8121 Title: An ultrasound-based seed detection method for dynamic
brachytherapy of the prostate
We report an intraoperative seed localization and dosimetry verification system for
prostate brachytherapy. It incorporates an electromagnetic (EM) sensing-based image
capture system, an image processing- and pattern recognition-based needle tracking and
seed localization algorithm performed on transrectal ultrasound (TRUS) images at 0.5mm
intervals, and DVH-based dosimetry verification. An EM sensor is attached onto the
ultrasound transducer. Immediately after seed implantation, an ultrasound scan is
performed by pulling back the transducer from base to apex of the prostate. The EM
sensor measures the distance from the start point and triggers the frame grabber installed
in a personal computer to capture images at each 0.5mm increment. Prostate boundaries
are drawn on the TRUS images separated by 5mm. The TRUS image series is then
processed to localize the seeds, thus enabling the DVH calculation. All of the above steps
can be performed intraoperatively immediately after seed implantation, when
supplemental seed placement is still possible. The performance of the system has been
tested by collecting both phantom and patient data using dosimetry results based on the
same-day CT scan as the gold standard. The average 3D position discrepancy between
CT and TRUS detected seeds is 1.12 ±1.02 mm (mean±standard deviation) for phantom
and 2.6±1.5mm for actual patients. The percentage of the seeds within 5mm discrepancy
is 98% for phantom and 75~80% for patients. The DVH discrepancy is 2.7% for V100
and 5.6% for D90 RMS-averaged over 4 patients. Conclusion: An intraoperative TRUSbased seed detection and dosimetry system has been developed and validated.