Measurement of the ultrasound backscatter signal from three seed types as a function of incidence angle: application to permanent prostate brachytherapy.
OBJECTIVE
To measure the relative ultrasound backscatter of different seed types as a function of seed orientation and to evaluate the corresponding images of these seeds.


METHODS
Three seed types were evaluated: OncoSeed (standard), EchoSeed (corrugated), and RAPID Strand(RS). Ultrasound images for angles of incidence varying from 90 degrees (perpendicular) to 20 degrees at 5MHz and 7.5MHz were produced by raster scanning the seeds in a degassed water bath. Seed images were visually inspected and analyzed using the integrated-optical-density (IOD) method.


RESULTS
Corrugated seeds appear as contiguous objects over the range of frequencies and orientations examined, whereas standard seeds appear as contiguous objects from 90 degrees to 80 degrees only. The ranges and means of the backscattered IOD ratio of the seeds from 85 degrees to 20 degrees were: (corrugated vs. standard) 1.48 to 3.72 (2.32 +/- 0.62) for 5 MHz and 1.26 to 3.77 (2.19 +/- 0.84) for 7.5 MHz and (corrugated vs. RS) 1.21 to 9.53 (2.98 +/- 2.48) for 5 MHz and 1.008 to 10.86 (2.79 +/- 3.08) for 7.5 MHz. Backscattered signal increase ranged from 1.66 dB to 20.7 dB for the corrugated seed as compared to the other seeds.


CONCLUSIONS
Corrugated seeds produce greater backscatter signal and a more readily identifiable seed image over a large range of seed orientation as compared with standard brachytherapy seeds.
Division of Radiation Oncology, Department of Physiology, Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA. davis.brian@mayo.edu
Brian J
BJ
Davis
Randall R
RR
Kinnick
Mostafa
M
Fatemi
Eugene P
EP
Lief
Richard A
RA
Robb
James F
JF
Greenleaf
D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D014465:Ultrasonics; D014463:Ultrasonography
D007457:Iodine Radioisotopes