Pediatric cardiovascular CT angiography: radiation dose reduction using automatic anatomic tube current modulation.
OBJECTIVE
The purpose of this study was to assess the effect of weight-based scanning protocols and automatic tube current modulation on the tube current-time product and image quality at pediatric cardiovascular 64-MDCT angiography.


METHODS
Our pediatric cardiovascular 64-MDCT protocols use a weight-based algorithm to determine nominal tube voltage settings with 80, 100, and 120 kV. Automatic tube current modulation was used for each case. The mAs, volume CT dose index (CTDI(vol)), and dose-length product (DLP) values were recorded and the effective dose calculated. On the basis of the selected nominal tube current, the dose values that would have been delivered without tube current modulation were also calculated. Scans were compared with 16-MDCT using 120 kVp and 120 mAs. Two radiologists independently rated image quality on a 5-point scale. Image noise was objectively measured within four different regions of interest. Findings at CT were clinically correlated with results of cardiac sonography, angiography, or surgery.


RESULTS
Thirty-eight 64-MDCT and 30 16-MDCT scans were evaluated. Mean diagnostic quality for 64-MDCT was rated at 3.6 +/- 0.4 and mean image noise was 8.9 +/- 4.5 H. Results with 16-MDCT were not significantly different: diagnostic quality (3.6 +/- 0.4; p = 0.97) and image noise (9.1 +/- 2.8 H; p = 0.31). Scanning with automatic tube current modulation significantly (p < 0.05) reduced the tube current time-product compared with scanning without automatic tube current modulation (-57.8%/54.1/128 mAs) or with 16-MDCT (-47.9%/54.1/104.37 mAs), respectively. The mAs values were significantly (p < 0.05) lower for 80 kVp than for 100 or 120 kVp scans, but image quality and image noise were not significantly (p = 0.24) different. Agreement between MDCT and clinical findings was excellent.


CONCLUSIONS
Under simulated conditions, automatic tube current modulation combined with low tube voltage settings significantly reduced radiation exposure and thus appears preferable in pediatric cardiovascular 64-MDCT.
Herzog
Christopher
C
Department of Radiology, Medical University of South Carolina, 169 Ashley Ave., Charleston, SC 29425, USA.
Mulvihill
Denise M
DM
Nguyen
Shaun A
SA
Savino
Giancarlo
G
Schmidt
Bernhard
B
Costello
Philip
P
Vogl
Thomas J
TJ
Schoepf
U Joseph
UJ
D000293:Adolescent; D000792:Angiography / Q000379:methods*; D016477:Artifacts; D001835:Body Weight; D018376:Cardiovascular Abnormalities / Q000000981:diagnostic imaging*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D011829:Radiation Dosage; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*