Strategies for cardiac CT imaging.

We review the scanning techniques for cardiac CT imaging with single slice and multislice scanners. Combined with prospective triggering for transaxial scanning and retrospective gating for helical scanning the potential advantages and the basic limitations are discussed. Based on those theoretical considerations, the major conclusion is that high resolution data sets with isotropic spatial resolution can be acquired with quadslice, spiral scanning, only. First clinical results support this conclusion.

Motion artifacts in cardiac CT. The Novacor left ventricular assist device and its implications for clinical imaging.

PURPOSE: Cardiovascular applications of CT are primarily limited by temporal resolution of the scanner. Recent development in scanner technology has greatly increased temporal resolution. We here describe a standardized method of assessing temporal properties of various CT techniques. MATERIAL AND METHODS: The Novacor left ventricular assist device was mounted in a water-filled circulation phantom and scanned at different pump rates with a spiral CT unit and an electron beam unit. We also evaluated the use of ECG-triggered subsecond scanning on a spiral CT unit. RESULTS: Using the fastest conventional scanning protocol, severe motion artifacts occurred. These artifacts could not be reproduced from image to image, even if the pump rate was adjusted to scan rate (l/s). Electron beam tomography (EBT) reproducibly yielded few artifacts at 100 ms and practically no artifacts at 50 ms scanning time. Even without ECG-triggering, pump motion could be reproduced as a cine-cycle. With the ECG-triggered partial scanning CT technique, limited motion artifacts could be reproduced during diastole at a heart rate of 70-80 beats/min. CONCLUSION: The Novacor ventricular assist device may serve as a benchmark test in the evaluation of new scanning techniques for cardiovascular CT. While EBT presently remains the only CT technique to freeze cardiac motion throughout its cycle, ECG-triggered subsecond scans may, under certain conditions, capture cardiac anatomy in diastole.

[Control of percutaneous biopsy with CT fluoroscopy]. / Steuerung von perkutanen Biopsien mittels CT-Fluoroskopie.

PURPOSE: Clinical evaluation of CT fluoroscopy and comparison with conventional CT guidance for monitoring of non-pulmonary percutaneous biopsy procedures. MATERIALS AND METHODS: 20 non-pulmonary CT-guided biopsy procedures were prospectively performed either with CT fluoroscopy or with conventional CT guidance. CT fluoroscopy was performed using 120 kV and 50, 70 or 90 mA at a frame-rate of three or six images per second. Number of punctures and biopsies, procedure times, radiation doses and histologic results were analyzed separately for conventional CT guidance and for CT fluoroscopy. RESULTS: With CT fluoroscopy, yield of biopsies was improved (p = 0.005, t-test) and procedure times were shorter than for conventional CT guidance (11.4 +/- 6.0 vs. 23.6 +/- 13.8 min; p = 0.03, t-test). Analysis of procedure related radiation exposure and histologic outcome showed no significant difference between conventional and fluoroscopic CT-guided procedures (p > 0.05, t-test). CONCLUSIONS: CT fluoroscopy facilitates guidance of percutaneous biopsy procedures. Compared to conventional CT assistance, procedure times are decreased while yield of biopsies is improved.