Figure 1.

State-of-the-art hybrid cardiac PET/CT protocol for delineation of the extent and functional consequences of atherosclerosis. With use of an integrated PET/CT imaging system, both anatomic CAD and resulting myocardial ischemia can be characterized in a single setting. In patients with known CAD, the coronary artery calcium (CAC) scan may be omitted (although its use may be helpful for identifying patients who have extensive coronary calcification and are thus poor candidates for nonenhanced CT angiography [CTA] performed with a relatively low radiation dose). Alternatively, if detailed delineation of the extent of CAD is not required, the CAC scan alone, without coronary CT angiography, may allow additional risk stratification at lower radiation doses without iodinated contrast material. Because the attenuation-correction CT is not electrocardiographically (ECG) gated and is performed during free breathing to best match the PET study, it is not useful for quantitative ascertainment of the calcium score. However, approximate evaluation of the calcium score from attenuation-correction CT images may be possible (15).