Determination of National Diagnostic Reference Levels in Computed Tomography Examinations of Iran by a New Quality Control-Based Dose Survey Method

Abstract

National diagnostic reference levels (NDRLs) of Iran were determined for the four most common CT examinations including head, sinus, chest and abdomen/pelvis. A new 'quality control (QC)-based dose survey method', as developed by us, was applied to 157 CT scanners in Iran (2014-15) with different slice classes, models and geographic spread across the country. The NDRLs for head, sinus, chest and abdomen/pelvis examinations are 58, 29, 12 and 14 mGy for CTDIVol and 750, 300, 300 and 650 mGy.cm for DLP, respectively. The 'QC-based dose survey method' was further proven that it is a simple, accurate and practical method for a time and cost-effective NDRLs determination. One effective approach for optimization of the CT examination protocols at the national level is the provision of an adequate standardized training of the radiologists, technicians and medical physicists on the patient radiation protection principles and implementation of the DRL concept in clinical practices.

Determination of Diagnostic Reference Level (DRL) in Common Computed Tomography Examinations with the Modified Quality Control-Based Dose Survey Method in Four University Centers: A Comparison of Methods

“…The difference between measurement of national DRL (NDRL) with QC method in the study conducted by Sohrabi et al [21] and this study that used the same for calculating DRL based on CTDI vol was 6%, 44%, 6.6%, and 6.4%, respectively. This difference shows an ascending trend in all examinations (Table 4).…”

“…If we add the patient effective diameter to the cause of the difference in the calculated CT-DI vol and the scan parameters in QC method respected to DC method, reflected more in the chest and abdomen/pelvis examinations, it reveals the cause of the statistically significant difference between MQC and QC method in each examination (P<0.001). Also, the DRL calculated based on CTDI vol and DLP for four examinations was higher than (except for sinus) all studies conducted with QC method [11,23] and NDRL studies with the QC and DC methods [18,21] (Table 4 and Figure 4). The decrease in the sinus examination dose in studies using QC (2, 3) and dual-purpose QC methods [23] is not particularly linked to the patient size and it may be originated from the low values of the mAs in this examination, also in the present study (Table 1).…”

“…Moreover, the DRL calculation by the QC method needs the scan parameters for the Brix formula, and this requirement has only been mentioned in Parsi's study [11], where this information was directly obtained by the devices, like QC and DC method in the present study. Consequently, the implementation time increased, but it is more cost-effective and less time-consuming than DC and Di methods for collecting information through questionnaires and direct measurement, respectively [11,21].…”

“…An American study conducted by Kanal et al [20] is the only study, used the SSDE method to measure NDRL. Based on the measurement of the water equivalent diameters of the CT images of the organs of 1,300,000 patients, which obtained from the National Radiology Data Registry (NRDR) through ACR, NDRLs with normalized CTDI vol of the 16-and 32- [21,23], Deevband et al [22], respectively. The MQC, QC, DPQC, DC and Di stand for: modified quality control based, quality control based, dual purpose quality control based, data collection and direct methods, respectively.…”

Assessment and comparison of radiation dose and image quality in multi-detector CT scanners in non-contrast head and neck examinations

“…In the case of head scan, overall, the mean values of the CTDIv, DLP, and ED were lower than those of other research studies summarised in Table 5. Sohrabi et al [27] recently proposed a National Diagnostic Reference Level (NDRL) for some CT procedures, comprising head scans. They proposed the values of 58 mGy and 750 mGy for the CTDIv and DLP, respectively.…”