Characterization of ultrasound elevation beamwidth artifacts for prostate brachytherapy needle insertion.
OBJECTIVE
Ultrasound elevation beamwidth leads to image artifacts and uncertainties in localizing objects (such as a surgical needle) in ultrasound images. The authors examined the clinical significance of errors caused by elevation beamwidth artifacts and imaging parameters in needle insertion procedures.


METHODS
Beveled prostate brachytherapy needles were inserted through all holes of a grid template under real-time transrectal ultrasound (TRUS) guidance. The needle tip position as indicated by the TRUS image was compared to their observed physical location. A new device was developed to measure the ultrasound elevation beamwidth.


RESULTS
Imaging parameters of the TRUS scanner have direct impact on the localization error ranging from 0.5 up to 4 mm. The smallest localization error was observed laterally close to the center of the grid template and axially within the beam's focal zone. Largest localization error occurs laterally around both sides of the grid template and axially within the beam's far field. The authors also found that the localization errors vary with both lateral and elevation offsets.


CONCLUSIONS
The authors found properly adjusting the TRUS imaging settings to lower the ultrasound gain and power effectively minimized the appearance of elevation beamwidth artifacts and in turn reduced the localization errors of the needle tip.
Laboratory for Percutaneous Surgery (Perk), School of Computing, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Mohammad
M
Peikari
Thomas Kuriran
TK
Chen
Anras
A
Lasso
Tamas
T
Heffter
Gabor
G
Fichtinger
Everette C
EC
Burdette
D016477:Artifacts; D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008297:Male; D009339:Needles; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D019919:Prosthesis Implantation / Q000379:methods*; D011677:Punctures / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018084:Ultrasonography, Interventional / Q000295:instrumentation / Q000379:methods*