Dual-source CT

Dual-source CT (DSCT) was designed to overcome the limitation in gantry rotation time by doubling the number of X-ray sources and detectors. By mounting two X ray sources and detector arrays at angle of 90^oon the rotating time. This has the effect of doubling temporal resolution compared to standard MSCT. For example, a dual source scanner with gantry rotation time of 330ms will have a temporal resolution of 83 ms. Several studies have shown the value of DSCT in producing diagnostic image quality in patients with heart rates up to 100bpm,potentially still improved if the heart rate controlled

Dual source data are acquired simultaneously in the same relative phase of a patients cardiac cycle and at the same anatomical level. The two rows detectors in DSCT tend to vary in the entire filed view (FOV; about 50cm), whilst the other is restricted to a smaller central FOV. The radiation burden from DSCT is roughly equivalent to a similar single source MSCT acquisition.

 

Comparison of (a) single –source and (b) dual-source CT. Doubling the number of X ray tube/detector array pairs reduces the arc required to obtain an image to 90⁰. thus improving temporal resolution two-fold

Another important feature of DSCT is that the voltage and current of each x ray can varied individually, allowing dual energy CT (DECT) scans to be performed. This technique uses the phenomenon that tissues attenuate x ray beams of different energies to differing energies to differing degrees, depending on their density. Although not extensively validated, cardiac applications of DECT potentially include digital subtraction of calcium from coronary arteries (although spatial resolution is currently a limiting factor) and characterization of myocardial enhancement patterns.