Coronary Artery Angiography Using Multislice Computed Tomography Images
Multislice CT scanners are the newest class of CT scanners and they have not one but many detectors. These scanners can acquire up to 4 slices of data from the body in the same time it takes a single-slice CT scanner to acquire one. Multislice CT allows for rapid cardiac imaging during a single breath-hold. A multislice scanner operated in helical mode provides information that can be used to reconstruct 3D cardiac images in arbitrary phases of the cardiac cycle.
A 71-year-old man with hypertension, hypercholesterolemia, and known aortic and peripheral vascular disease was imaged with a LightSpeed 4-slice, multislice CT scanner (GE Medical Systems). Ten minutes before the cardiac scan, the patient received intravenous contrast material (150 mL of 300 mgI/mL) for a CT study of his abdomen. The cardiac scan was acquired during a 35-s breath-hold, and simultaneous acquisition of the ECG enabled reconstruction using retrospective gating (Figure 1⇓). The helical pitch was 0.85 (relative to the detector elements), with a 2.5-mm nominal slice thickness (interpolated to 0.625 mm). The interpolated volume elements (voxels) were 0.39×0.39×0.625 mm in a 512×512×130 data matrix covering a 200×200×81 mm volume. The effective temporal acquisition window was 160 ms. Postprocessing tools were used to separate the coronary arteries from the cardiac chamber blood pool. Three-dimensional images can be displayed as projections similar to those obtained at catheter angiography (Figure 2⇓).
These first results of ECG-gated multislice CT cardiac imaging are encouraging. At present, the quality of these scans is dependent on heart rate, rhythm, and patient ability to suspend respiration. Current developments will make this technique more robust. Increasing the number of detector rows will result in improved temporal and spatial resolution and fewer motion artifacts. Faster and variable gantry rotation speeds will improve temporal resolution and image quality over a greater range of heart rates and rhythms. A cardiac gated-pulse x-ray tube could be used to decrease patient dose if diastolic imaging is sufficient. Imaging of the coronary arteries, for example, can be limited to diastole without a diagnostic penalty. A clinical study comparing multislice CT coronary angiography with conventional x-ray angiography is required for validation of this new method.
The authors thank Erdogan Cesmeli, PhD, Siegwalt Ludke, BS, Christopher Hardy, PhD, James Miller, PhD, William Lorensen, MS, Nagesh Mallugari, and Tony Pan for their contributions.
Drs Cline, Yavuz, Edie, Pan, Iatrou, and Ishaque and Mr Avila and Mr Turek work for General Electric, which manufactures the LightSpeed multislice CT scanner discussed in the article.
The editor of Images in Cardiovascular Medicine is Hugh A. McAllister, Jr, MD, Chief, Department of Pathology, St Luke’s Episcopal Hospital and Texas Heart Institute, and Clinical Professor of Pathology, University of Texas Medical School and Baylor College of Medicine.
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