Detection of prostate calcification with megavoltage helical CT.
OBJECTIVE
Prostate calcification is a noninvasive landmark for daily positioning of image-guided radiation therapy. However, detectability of prostate calcification with megavoltage helical computed tomography (MVCT) has not been evaluated. The purpose of this study was to evaluate the detectability of prostate calcification and to investigate how to predict detectability of calcification with MVCT.


METHODS
Thirty patients with prostate cancer who were scheduled for helical tomotherapy were included in this study. The detectability of prostate calcification on MVCT was evaluated by comparing against kilovoltage multidetector-row CT (KVCT) as the standard of reference. Maximum signal intensity (SImax), area (A) of calcification, and the product of both (SImax·A) were compared between undetectable and detectable calcifications. Then, the threshold values of SImax, A, and SImax·A were decided to achieve 100% sensitivity on MVCT.


RESULTS
KVCT identified 49 calcifications in 28 of 30 patients. MVCT detected 19 (39%) of 49 calcifications in 15 (50%) of 30 patients. The minimum threshold values of SImax, A, and SImax·A to detect prostate calcifications were 953 HU, 20.98 mm(2), and 7784 HU mm(2), respectively. Using the threshold values of SImax, A, and SImax·A, 20% (10/49), 18% (9/49), and 35% (17/49) of calcifications were in the detection range, respectively.


CONCLUSIONS
MVCT can depict about one-third of prostate calcifications detectable on KVCT. The product of maximum signal intensity and area of calcification is the most distinguishable index for predicting patients showing prostate calcifications on MVCT.
Department of Radiology, Tokyo Edogawa Cancer Center, Edogawa Hospital, 2-24-18 Higashikoiwa, Edogawaku, Tokyo, 133-0052, Japan. Electronic address: yjhama2005@yahoo.co.jp.
Yukihiro
Y
Hama
D000368:Aged; D002114:Calcinosis / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D036542:Tomography, Spiral Computed / Q000379:methods*
CT scan; Helical tomotherapy; image analysis; image-guided radiation therapy; megavoltage imaging