Cardiac CT is emerging as an important tool for the diagnosis and monitoring of heart disease. The incidence of heart disease in the United States is already quite high and is expected to increase as the “baby boomer” segment of the population ages. To use complex multiple-row detector CT scanners most efficiently for cardiac examinations, it is important to understand many of the technical components. In addition, radiation dose for cardiac CT studies is fairly high and demands constant vigilance.
Cardiac CT techniques are generally similar to those used for routine chest CT—with a few important exceptions. Although the tube potential (measured in kilovolts) and current (measured in milliamperes) are often similar to those used for a routine chest CT study, the rotation speed is generally the fastest that can be achieved by the scanner model, and the pitch value used is often much lower than that used in routine chest examinations (typically 0.2–0.4). The use of extremely low pitch values can cause some alarm with respect to radiation dose values. However, the scan extent (start-to-stop distance for the image acquisition) is generally limited (usually 12 cm), which results in a dose range that is near accepted values for similar CT examinations of the torso.
No comments:
Post a Comment