Multidetector computed tomography chest examinations with low-kilovoltage protocols in adults: effect on image quality and radiation dose.J Comput Assist Tomogr. 2009 May-Jun; 33(3):416-21.JC
The purpose of our study was to assess the effect on image quality and radiation dose of chest multidetector computed tomography (CT) examinations with low-kilovoltage protocols for adults.
This study was approved by the institutional review board of our medical center. Two hundred ten patients (83 women, 127 men; mean age, 56.1 years) requiring contrast-enhanced chest CT examination were randomly assigned to 1 of 3 protocol groups: (1) protocol A, the standard protocol, with 120 kilovolt (peak) (kV[p]) and 100 effective milliampere-second (eff mA s); (2) protocol B, with 100 kV(p) and 140 eff mA s; and (3) protocol C, with 80 kV(p) and 180 eff mA s. Each group included 70 patients. Contrast material injection protocols were standardized for all groups. Three radiologists blinded to the CT parameters used assessed images in random order for 20 items from 4 anatomical regions. They ranked the subjective image quality using a 4-point scale. The volume computed tomography dose index (CTDIvol) and dose length product (DLP) were displayed by the CT unit after the automatic exposure control-driven acquisition was recorded for each group; the differences were analyzed for statistical significance.
When the overall agreement was pooled from the 3 observers, the qualitative score analysis revealed no significant difference between the 100-kV(p) and the standard protocols (P > 0.05). However, when the scores were compared between the 80-kV(p) and the standard protocols, a marginal significance (P = 0.054) was observed. When the patients in the group with an 80-kV(p) protocol were subcategorized according to body mass index (BMI), the image quality scores of all BMI subgroups, of the 80-kV(p) protocol, were not significantly different from those of the standard protocol. However, an increase in the BMI tended to be associated with a decrease in the subjective image quality. The mean values of CTDIvol for 120-, 100-, and 80-kV(p) protocols were 5.042, 4.507, and 2.883, respectively. The mean values of DLP for each protocol were 187.5, 158.7, and 105.8, respectively. The CTDIvol and DLP of the low-kilovoltage protocols were significantly lower than those of the standard protocol (P < 0.01). The DLP of the 100- and 80-kV(p) protocols were reduced radiation exposure doses in 15.36% and 43.57%, respectively, as compared with the standard protocol.
The use of low-kilovoltage protocol resulted in a significant reduction in the radiation exposure at chest CT, with image qualities comparable with those of the standard protocols.