Balancing radiation dose and image quality: clinical applications of neck volume CT

The advancement of multidetector CT technology has resulted in improved image quality as well as an increase in ionizing radiation dose to patient. The purpose of this study was to assess radiation dose and overall image quality of CT examination of the neck between fixed-tube current and automatic tube current modulation (ATCM) at 2 separate noise index levels.

A total of 84 patients underwent neck CT with use of a 64-section multidetector row CT (MDCT) scanner. Patients were divided into 3 groups: fixed-tube current (n = 28), ATCM with a noise index of 11.4 (n = 28), and ATCM with a noise index of 20.2 (n = 28). All other scan parameters remained constant. Scan coverage length and transclavicular distance were measured. Two radiologists blinded to the scanning parameters assessed overall image quality, noise level, and streak artifacts using a 5-point grading scale. The radiation dose in dose-length product (DLP) and CT dose index (CTDI) was recorded.

Compared with a fixed-tube current technique, ATCM with a noise index of 11.4 reduced CTDI by 20% (P < .01 x 10(-6)), and ATCM with a noise index of 20.2 reduced CTDI by 34% (P < .01 x 10(-12)). Although the difference in image quality between the fixed-tube current technique and the noise index reached statistical significance (P < .05), the magnitude of the difference was small, with average scores of 3.79 (+/-0.59) and 3.57 (+/-0.53), respectively.

Compared with the fixed-tube current technique, ATCM resulted in significant reduction of radiation dose without substantially reducing the image quality of the CT of the neck. Judicious monitoring of radiation dose to patients has to be balanced with diagnostic image quality.