A Method for the Automatic Exposure Control in Pediatric Abdominal CT: Application to the Standard Deviation Value and Tube Current Methods by Using Patient's Age and Body Size.

We aimed to apply the pediatric abdominal CT protocol of Donnelly et al. in the United States to the pediatric abdominal CT-AEC. Examining CT images of 100 children, we found that the sectional area of the hepatic portal region (y) was strongly correlated with the body weight (x) as follows: y=7.14x + 84.39 (correlation coefficient=0.9574). We scanned an elliptical cone phantom that simulates the human body using a pediatric abdominal CT scanning method of Donnelly et al. in, and measured SD values. We further scanned the same phantom under the settings for adult CT-AEC scan and obtained the relationship between the sectional areas (y) and the SD values. Using these results, we obtained the following preset noise factors for CT-AEC at each body weight range: 6.90 at 4.5-8.9 kg, 8.40 at 9.0-17.9 kg, 8.68 at 18.0-26.9 kg, 9.89 at 27.0-35.9 kg, 12.22 at 36.0-45.0 kg, 13.52 at 45.1-70.0 kg, 15.29 at more than 70 kg. From the relation between age, weight and the distance of liver and tuber ischiadicum of 500 children, we obtained the CTDIvol values and DLP values under the scanning protocol of Donnelly et al. Almost all of DRL from these values turned out to be smaller than the DRL data of IAEA and various countries. Thus, by setting the maximum current values of CT-AEC to be the Donnelly et al.'s age-wise current values, and using our weight-wise noise factors, we think we can perform pediatric abdominal CT-AEC scans that are consistent with the same radiation safety and the image quality as those proposed by Donnelly et al.

Modified method for automatic exposure control in pediatric brain CT-application of the standard deviation value method by use of patient's age and head size.

We examined the optimum conditions for pediatric brain CT scans. CT controls the X-ray transit dose using tube current alteration called automatic exposure control (AEC) to adjust the standard deviation (SD) value for each scanning region, and it also reduces exposure. If the SD value is inappropriate, children may be exposed to increased radiation. Therefore we acquired images of 500 children from the server, and examined the most suitable SD value for each age using the data of their SD value and age. X-ray transit control with AEC was influenced by scan position and the age of a child. We enabled accurate scanning and decreased radiation exposure by adjusting AEC to the age and the cephalic volume of each child. As a result, reduction of the X-ray exposure by up to 31.2% per slice in tube current alteration was possible using a suitable SD value for each age. On the other hand, it was possible to reduce X-ray exposure by up to 67.9% per slice with the scan technique that used age and corrected cephalic volume without adjusting AEC. Using the tube current alteration protocol for each age with the data of the SD value or cephalic volume in CT, we can more easily conduct scans of children under optimal conditions.