Determinants of vessel contrast in BMI-adapted low dose CT coronary angiography with prospective ECG-triggering

Abstract

Methods: Seventy patients underwent low-dose CTCA using BMI-adapted tube parameters and a fixed contrast material bolus. Contrast to noise ratio (CNR) was calculated from contrast (between coronaries and perivascular tissue) and image noise (standard deviation of aortic attenuation). Cardiac output (CO) was calculated from gated 99m Tc-tetrofosmin-SPECT.Results: Mean radiation dose was 2.13 0.69mSv. Image noise was not affected by BMI (r=0.1, P=0.36), while CNR was inversely related to body surface area (BSA) (r= -0.5, P<0.001) and CO (r= -0.49, P<0.001). Conclusions:After successfully overcoming the impact of BMI on image noise by adapting tube parameters, CNR mainly depends on coronary vessel contrast. The latter reflects the dilution of the contrast material by blood volume and CO, which are both correlated to BSA. Therefore, BSA adapted contrast administration may help to compensate for this effect.

Validation of a new contrast material protocol adapted to body surface area for optimized low-dose CT coronary angiography with prospective ECG-triggering

“…The findings of the present study document that the BSA-adapted CM administration protocol is feasible and successful as the inverse correlation between BSA and coronary attenuation found in our control group, and also documented in previous reports [13,19], could be abolished. As a result, range and standard deviation of coronary attenuation were smaller in the BSA-adapted group compared to the control group indicating a well balanced consistent contrast enhancement throughout a large range of BSA (Fig.…”

“…By contrast, the adverse effect of body mass on coronary attenuation is less well understood but recent reports have suggested increased CM dilution due to higher blood volume as explanation. Consequently, the hypothesis has been generated that BSA would be the most promising parameter to be used for CM protocol adjustment [13,19]. Our study provides the evidence to approve this hypothesis.…”

“…Attenuation of coronary vessel in CTCA is closely related to several factors including patient specific characteristics on one side such as body mass, blood volume and cardiac output [8,9,11,13] as well as protocol related parameters on the other side such as concentration and injection rate of the administered CM [7,19,25]. In patients with increased body mass CTCA image quality is degraded by an unfavorable shift in the signal-to-noise ratio due to increase in noise and loss of attenuation.…”

“…However, the protocol was designed based on the upslope of the coronary attenuation -BSA curve previously reported [19]. Third, coronary attenuation was measured only in two proximal vessels (RCA and LMA).…”

“…Recently a BMI adapted protocol was introduced in order to reduce the impact of BMI on image noise. However, coronary contrast remained subject to large variations [19], presumably due to bolus dilution depending on blood volume. As increased blood volume is well paralleled by BSA we identified BSA as the most promising parameter to be of potential value for adjusting the contrast bolus in future protocols.…”