Dose reduction in spiral CT coronary angiography with dual-source equipment. Part I. A phantom study applying different prospective tube current modulation algorithms.
OBJECTIVE
The authors sought to compare different algorithms for dose reduction in retrospectively echocardiographically (ECG)-gated dual-source computed tomography (CT) coronary angiography (DSCT-CA) in a phantom model.


METHODS
Weighted CT dose index (CTDI) was measured by using an anthropomorphic phantom in spiral cardiac mode (retrospective ECG gating) at five pitch values adapted with two heart-rate-adaptive ECG pulsing windows using four algorithms: narrow pulsing window, with tube current reduction to 20% (A) and 4% (B) of peak current outside the pulsing window; wide pulsing window, with tube current reduction to 20% (C) and 4% (D). Each algorithm was applied at different heart rates (45, 60, 75, 90, 120 bpm).


RESULTS
Mean CTDI volume (CTDIvol) was 36.9+/-9.7 mGy, 23.9+/-5.6 mGy, 49.7+/-16.2 mGy and 38.5+/-12.3 mGy for A, B, C and D, respectively. Consistent dose reduction was observed with protocols applying the 4% tube current reduction (B and D). Using the conversion coefficient for the chest, the mean effective dose was the highest for C (9.6 mSv) and the lowest for B (4.6 mSv). Heart-ratedependent pitch values (pitch=0.2, 0.26, 0.34, 0.43, 0.5) and the use of heart-rate-adaptive ECG pulsing windows provided a significant decrease in the CTDIvol with progressively higher heart rates (45, 60, 75, 90, 120 bpm), despite using wider pulsing windows.


CONCLUSIONS
Radiation exposure with DSCT-CA using a narrow pulsing window significantly decreases when compared with a wider pulsing window. When using a protocol with reduced tube current to 4%, the radiation dose is significantly lower.
Martini
C
C
Dipartimento di Radiologia e Cardiologia, Azienda Ospedaliero-Universitaria, Parma, Italy.
Palumbo
A
A
Maffei
E
E
Rossi
A
A
Rengo
M
M
Malagò
R
R
Dijkshoorn
M
M
Weustink
A
A
Mollet
N
N
Krestin
G
G
Cademartiri
F
F
D015502:Absorptiometry, Photon; D000465:Algorithms; D017023:Coronary Angiography / Q000295:instrumentation* / Q000379:methods; D004562:Electrocardiography; D004867:Equipment Design; D006321:Heart / Q000000981:diagnostic imaging; D006339:Heart Rate; D006801:Humans; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013819:Thermoluminescent Dosimetry; D036542:Tomography, Spiral Computed