Multi-slice CT-colonography in low-dose technique--Preliminary results.
OBJECTIVE
Assessment of Multi-Slice CT-colonography (MSCTC) with standard and low-dose technique in comparison to conventional colonoscopy (CC).


METHODS
After standardized bowel cleansing, 28 men and 24 women (mean age 60,3 years) underwent CC within two hours after MSCTC had been performed (4 x 2.5 mm collimation, 3 mm slice width, 17.5 mm table feed, 120 kVp). In 19 patients, MSCTC was performed with 120 mAs (CTDI w, eff : 11.28 mGy), and in 33 patients with 10 mAs (CTDI w, eff : 0.94 mGy), respectively. After noise reduction using mathematical algorithms by a dedicated software (ECCET), images were analyzed by two blinded readers in simultaneously displayed 2D- and 3D-modes. Findings in MSCTC were compared to the results obtained with CC.


RESULTS
Calculated effective doses ranged between 9 and 12 mSv for 120 mAs, and between 0.75 and 1 mSv for the low-dose technique. In standard dose MSCTC, 20 of 25 lesions (80 %) were found: all 7 tumors (100 %), one large polyp (> 10 mm; 100 %), 6 of 7 medium sized polyps (9.9 to 5 mm; 86 %) and 6 of 10 small polyps (< 5 mm; 60 %). In low-dose MSCTC, 32 of 44 lesions (73 %) were seen: all three large polyps (100 %), 13 of 14 medium sized polyps (93 %) and 16 of 27 small polyps (59 %). An overall sensitivity of 78 % with a specificity of 68 % was calculated. False positive findings were seen mostly for small lesions (12 for standard dose, 11 for low-dose).


CONCLUSIONS
Despite a 12-fold reduction of radiation exposure, MSCTC in low-dose technique performs comparably well to standard dose MSCTC. After mathematical noise reduction, more than 90 % of polyps larger than 5 mm can be detected.
Cohnen
M
M
Institute of Diagnostic Radiology, University Hospital, Düsseldorf, Germany. cohnen@uni-duesseldorf.de
Vogt
C
C
Aurich
V
V
Beck
A
A
Häussinger
D
D
Mödder
U
U
D000465:Algorithms; D003106:Colon / Q000000981:diagnostic imaging*; D003110:Colonic Neoplasms / Q000000981:diagnostic imaging*; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D003113:Colonoscopy; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014584:User-Computer Interface