Small coronary calcifications are not detectable by 64-slice contrast enhanced computed tomography

Area of Science:

• Cardiovascular Imaging
• Radiology
• Interventional Cardiology

Background:

• Small calcifications are increasingly linked to unstable atherosclerotic plaques.
• Both intravascular ultrasound (IVUS) and multi-slice computed tomography (MSCT) can identify plaque calcifications.
• MSCT's lower resolution may lead to the omission of smaller calcifications.

Purpose of the Study:

• To compare the detection rates of coronary artery calcifications between contrast-enhanced MSCT and IVUS.
• To determine the size limitations for detecting calcifications using MSCT.

Main Methods:

• Coronary arteries of patients with myocardial infarction or unstable angina were imaged using 64-slice MSCT angiography and IVUS.
• IVUS and MSCT images were registered for direct comparison of calcification detection.
• The length and maximal circumferential angle of calcifications were measured using IVUS.

Main Results:

• Out of 99 calcifications detected by IVUS in 31 arteries, only 47 were identified by MSCT.
• Calcifications missed by MSCT were significantly smaller in angle (27° vs. 59°) and length (1.4 mm vs. 3.7 mm) compared to those detected.
• Reliable MSCT detection required calcifications >2.1 mm in length or >36° in angle.

Conclusions:

• Approximately half of the calcifications visualized by IVUS are undetectable by contrast-enhanced 64-slice MSCT angiography.
• The limited resolution of MSCT is the primary factor responsible for missing smaller coronary artery calcifications.
• This highlights a significant limitation of MSCT in fully characterizing plaque burden, particularly small calcifications associated with plaque instability.