Additive value of semiautomated quantification of coronary artery disease using cardiac computed tomographic angiography to predict future acute coronary syndrome.

OBJECTIVES: The purpose of this study was to investigate whether the use of a semiautomated plaque quantification algorithm (reporting volumetric and geometric plaque properties) provides additional prognostic value for the development of acute coronary syndromes (ACS) as compared with conventional reading from cardiac computed tomography angiography (CCTA). BACKGROUND: CCTA enables the visualization of coronary plaque characteristics, of which some have been shown to predict ACS. METHODS: A total of 1,650 patients underwent 64-slice CCTA and were followed up for ACS for a mean 26 ± 10 months. In 25 patients who had ACS and 101 random controls (selected from 993 patients with coronary artery disease but without coronary event), coronary artery disease was evaluated using conventional reading (calcium score, luminal stenosis, morphology), and then independently quantified using semiautomated software (plaque volume, burden area [plaque area divided by vessel area times 100%], noncalcified percentage, attenuation, remodeling). Clinical risk profile was calculated with Framingham risk score (FRS). RESULTS: There were no significant differences in conventional reading parameters between controls and patients who had ACS. Semiautomated plaque quantification showed that compared to controls, ACS patients had higher total plaque volume (median: 94 mm(3) vs. 29 mm(3)) and total noncalcified volume (28 mm(3) vs. 4 mm(3), p ≤ 0.001 for both). In addition, per-plaque maximal volume (median: 56 mm(3) vs. 24 mm(3)), noncalcified percentage (62% vs. 26%), and plaque burden (57% vs. 36%) in ACS patients were significantly higher (p < 0.01 for all). A receiver-operating characteristic model predicting for ACS incorporating FRS and conventional CCTA reading had an area under the curve of 0.64; a second model also incorporating semiautomated plaque quantification had an area under the curve of 0.79 (p < 0.05). CONCLUSIONS: The semiautomated plaque quantification algorithm identified several parameters predictive for ACS and provided incremental prognostic value over clinical risk profile and conventional CT reading. The application of this tool may improve risk stratification in patients undergoing CCTA.

Intravenous contrast material administration at 16-detector row helical CT coronary angiography: test bolus versus bolus-tracking technique.

PURPOSE: To compare test bolus and bolus-tracking techniques for intravenous contrast material administration at 16-detector row computed tomographic (CT) coronary angiography. MATERIALS AND METHODS: This study had institutional review board approval, and patients gave informed consent. Thirty-eight patients (mean age, 60 years; three women) were randomized into two groups according to bolus timing technique: group 1 (20-mL test bolus with 100-mL main bolus) and group 2 (bolus tracking with 100-mL main bolus). All patients underwent electrocardiography-gated 16-detector row CT coronary angiography with 12 detectors (collimation, 0.75 mm; rotation time, 420 msec). In group 1, test bolus peak attenuation was used as a delay, while in group 2, a +100-HU threshold in ascending aorta triggered angiographic acquisition, with an additional 4-second delay for patient instruction. Attenuation was measured in the longitudinal direction throughout the examination in three main vessels: ascending aorta (region of interest [ROI] 1), descending aorta (ROI 2), and main pulmonary artery (ROI 3). Mean attenuation and slope of bolus geometry curve were calculated in each patient and ROI. Attenuation at origin of coronary arteries was measured. Student t test was used to compare results. RESULTS: Mean scan delay was 6 seconds longer in group 2 (P < .05). Average attenuation values were 306.6 HU +/- 44.0 (standard deviation) and 328.2 HU +/- 58.6 (P > .05) in ROI 1, 291.6 HU +/- 45.1 and 326.4 HU +/- 62.6 (P > .05) in ROI 2, and 354.7 HU +/- 78.0 and 305.3 HU +/- 71.4 (P < .05) in ROI 3 for groups 1 and 2, respectively. Average slope values were 5.8 and -0.8 (P < .05) in ROI 1, 7.7 and 0.7 (P < .05) in ROI 2, and -1.0 and -13.3 (P < .05) in ROI 3 for groups 1 and 2, respectively. Average attenuation values in left main, left anterior descending, and left circumflex arteries were higher in group 2 (P < .05); there were no differences (P > .05) between groups in right coronary artery. CONCLUSION: Bolus-tracking yields more homogeneous enhancement than does the test bolus technique.

Multi-detector row CT angiography in patients with abdominal angina.

Abdominal angina (AA) is an infrequently occurring syndrome characterized by postprandial abdominal pain due to reduced blood flow to organs in the territory of the celiac trunk, superior mesenteric artery (SMA), and inferior mesenteric artery. Multi-detector row computed tomographic (CT) angiography with four- or 16-row scanners has become a primary tool for the evaluation of patients with suspected steno-occlusive diseases of the abdominal vessels. In patients with suspected AA, multi-detector row CT angiography can help evaluate the presence and degree of stenosis in the celiac trunk and SMA, demonstrate the collateral circulation, and help exclude other causes of vascular obstruction. It also allows visualization of small vessels and of vessel wall abnormalities in the absence of significant stenosis. Vessels with a complex anatomic configuration can easily be visualized with proper postprocessing techniques. This modality can also be used to follow up patients who have undergone percutaneous interventional treatment. Limitations include the lack of dynamic representation of flow abnormalities and difficulty in evaluating heavily calcified vessels. Nevertheless, multi-detector row CT angiography with appropriate postprocessing techniques is highly effective for the diagnosis, evaluation, and treatment of suspected AA. Additional studies will help further evaluate the performance and applications of this modality.