Cardiac CTA has proved to be a promising and robust technique for imaging coronary plaque and specific types of coronary lesions. The revolutionary capabilities of cardiac CT provide radiologists with a reliable and noninvasive method of analysis to the nation's number one killer, cardiovascular disease.

Cardiac CTA has proved to be a promising and robust technique for imaging coronary plaque and specific types of coronary lesions. The revolutionary capabilities of cardiac CT provide radiologists with a reliable and noninvasive method of analysis to the nation's number one killer, cardiovascular disease.

When using EKG gated CTA, "it is imperative for us to look at how it compares to some of the mainstays of cardiac imaging," warns Dr. Michael Atalay, Assistant Professor at Brown Medical School. There are several obvious advantages to cardiac CTA. For one, it is fast. It provides tremendous 3D techniques for high spatial resolution as well as high temporal resolution and... it is convenient.

Another benefit to EKG gated cardiac CT is that it offers an easy channel in providing the patient with a 'triple rule out'. "It is protocol in our department that every CTA that is EKG gated becomes an automatic triple rule out," states Atalay. But with advantages there are usually a few disadvantages. In addition to iodinated contrast, when it comes to CT angiography, "radiation is clearly a major issue," he adds.

Measuring and analyzing coronary artery plaque can be a challenge. "They are small, they are fuzzy and they overlap with other surrounding areas," says Dr. Oleg Pianykh of Beth Israel Medical Center.

Speaking at the 2008 annual ARRS meeting, Dr Pianykh proposed an improved automatic plaque analysis tool with morphology-based vessel segmentation. Dr. Pianykh and researchers created a novel, fully-automated vessel analysis tool for CT images that enhances HU-based vessel processing with morphology-driven segmentation. "Plaque is commonly segment-based and their Hounsfield density changes," adds Pianykh.

With knowledge of vessel morphology, three radiologists using the software processed eight cardiac CT cases, performed for coronary artery disease analysis. Vessel walls were manually excluded from the plaque analysis, and plaques were manually traced. Researchers noted that the resulting plaque volumes were identical in each case. With less than two seconds per vessel segment, this algorithm was implemented into Dr. Pianykh's imaging software and provides a reliable, reproducible, and robust plaque analysis tool that eliminates subjectivity in object identification, and alleviates the effects of partial volume.

Data has shown that, compared with expert manual planimetric measurements, automated processing tools enable accurate volumetry of noncalcified plaque burden. Use of such tools should facilitate fast, objective and reproducible assessment of noncalcified plaque burden for risk stratification and therapeutic monitoring.

In a 37 patient study, Dr. Kevin Blackmon and researchers from the Medical University of South Carolina evaluated a post-processing software tool for automated volumetric quantification of noncalcified coronary artery plaque burden at noninvasive coronary CT angiography.

Utilizing a 64 slice scanner, patients underwent a contrast enhanced coronary artery CTA. Two experienced observers in consensus evaluated each scan and identified 40 non-calcified coronary artery plaques. As the reference standard, they also performed manual 3D planimetric measurements on each plaque. Utilizing a threshold-based software tool for automated assessment of non-calcified plaque burden, the same two observers performed volumetric measurements on each plaque. Two different and less experienced observers performed these same objectives, first independently and then in consensus.

Researchers noted automated volumetric assessment was successfully performed on each plaque, and there was excellent correlation between the expert manual measurements and measurements using the automated volumetry tool. On the other hand, for the less experienced observers, results showed there was better correlation with expert manual measurements using the automated tool.

Interestingly, Blackmon states, "Inter-reader correlation for volume measurements by the two less experienced observers with and without use of the automated tool, significantly increased."

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