Question

Compare and contrast conventional CT with spiral CT in terms of image quality, image acquisition method, speed of acquisition, post-processing functions and patient dose.

Answer 1

Conventional CT scan: Conventional CT (also called dynamic incremental scanning), is generated by directing an X-ray beam at several different angles and levels of the abdomen. Contrast dye, given to the patient orally and/or intravenously, helps to make the organs visible by appearing white on the X-ray films. A computer processes the X-ray information and produces the CT images, usually as 1/2-inch cross-sectional slices of the abdomen. In this type of scan, we get two-dimensional images with fewer details compare to the spiral scan.

In this method, the X-ray beam is turned on discretely with respect to the position to position, like once the patient is positioned, the X-ray beam is turned on for approximately 1-2 seconds and then turned off. Then the table is moved to the next position or increment and the X-ray is turned on again. Because of this, it’s a relatively slow technique, the timing may not coincide with when the dye is optimal for imaging. The resulting image may not be adequate. After some time the dye also goes away. The resulting image is not very good and crisp.

Spiral CT (also called helical) is the most recently developed and accurate method. Unlike the conventional CT, during the spiral CT, the X-ray beam remains on continuously and rotates around the patient as the patient is moved through. This is a much more efficient technique that reduces the scanning time of the entire process from approximately two minutes. The resulting images are three-dimensional rather than the two-dimensional images created with conventional techniques. And we don’t need to overdose the patient compare to conventional CT scan.