Patient dosimetry during chest, abdomen, skull and neck radiography in SW Nigeria

Typical effective dose values from diagnostic and interventional radiology

Effective dose (E) in medical procedures is of practical value for comparing doses from different types of procedures which is not possible with the different measurable dose quantities. In this survey we estimated and compared the values of E in 12 medical imaging procedures. The mean E for conventional X-ray in mSv were ranged between 0.01 for skull lateral to 0.5 for abdominal while the mean E for cardiac interventional radiology in mSv was up to 16 for percutaneous transluminal coronary angioplasty (PTCA). For dental radiology the mean E in μSv was 1.2 for intraoral and 10 for panoramic. In mammography the mean E was 0.5 mSv. Compared with the literature, chest postero-anterior (PA), lumbar spine AP, PTCA and mammography procedures had shown larger E values. The obtained results can help in justification of techniques.

PHANTOM EXPERIMENTAL STUDY ON PATIENT DOSES OBTAINED FROM 320-MULTIDETECTOR-ROW COMPUTED TOMOGRAPHY IN WHOLE-BRAIN PERFUSION SCAN

This study aimed to precisely evaluate organ dose and effective dose (E) obtained from a 320-multidetector-row computed tomography (CT) scanner in brain perfusion scans and to estimate the conversion factor (k) between E and dose length product (DLP). A total of 270 thermoluminescent dosemeters were implanted in a male anthropomorphic phantom to measure air kerma. The ratios of mass-energy absorption coefficients were used to convert air kerma into organ doses. The organ doses ranged from 0.01 to 150 mGy. Doses in brain, salivary glands and red bone marrow were relatively high, and dose in eye lens reached about 110 mGy. The resulting effective dose was 5.30 mSv. The resulting conversion factor k = (0.0022 ± 0.0002) mSv·(mGy·cm)-1 was not significantly different from that of 0.0021 mSv·(mGy·cm)-1 reported for head CT scan in ICRP Publication 102.

Updated effective doses in radiology

The aim of this study was to review recent literature in order to provide updated values of the typical effective doses associated with the top 20 imaging tests for adults and children and for the most widely used set of weights (ICRP60) as well as for the most recent one (ICRP103). We performed a systematic research on radiation dosimetry in radiology published from 2007 onwards through the Medline, Embase and Cochrane Library Plus databases. We also included studies backed by scientific or governmental organizations. Other variables included: year and type of study (survey or descriptive), country, method and sample used for the measurement. Mean effective dose, minimum, maximum and standard deviation were calculated. We compared our results with previous evidence and with data from DDM2. We included 27 articles and 5 web references in the study. A total of 378 values from the 20 procedures included were obtained, 280 (74%) using ICRP60 and 98 (26%) using ICRP103. Effective doses for CT procedures in children were very similar to those for adults, with the exception of CT Trunk, but fluoroscopy procedures had consistently lower dose. There were differences between the current data with either ICRP60 or ICRP103, and the previous published data. In conclusion, we provided the best available evidence from literature to evaluate the effective dose received by each patient for the most typical examinations. According to the recommendations from the Report 154 and from the European Council Directive, these results could also be useful to estimate the range of average exposures to the population.

Evaluation of dose-area product of common radiographic examinations towards establishing a preliminary diagnostic reference levels (PDRLs) in Southwestern Nigeria

In Nigeria, a large number of radiographic examinations are conducted yearly for various diagnostic purposes. However, most examinations carried out do not have records of doses received by the patients, and the employed exposure parameters used are not documented; therefore, adequate radiation dose management is hin-dered. The aim of the present study was to estimate the dose-area product (DAP) of patients examined in Nigeria, and to propose regional reference dose levels for nine common examinations (chest PA, abdomen AP, pelvis AP, lumbar AP, skull AP, leg AP, knee AP, hand AP, and thigh AP) undertaken in Nigeria. Measurement of entrance surface dose (ESD) was carried out using thermoluminescent dosimeter (TLD). Measured ESDS were converted into DAP using the beam area of patients in 12 purposely selected hospitals. Results of the study show that the maximum/ minimum ratio ranged from 3 for thigh AP to 57 in abdomen AP. The range of determined mean and 75th percentile DAPs were 0.18-17.16, and 0.25-28.59 Gy cm2, respectively. Data available for comparison show that 75th percentile DAPs in this study (in chest PA, abdomen AP, pelvis AP, lumbar AP) are higher than NRPB-HPE reference values. The DAP in this study is higher by factor of 31.4 (chest PA), 9.9 (abdomen AP), 2.2 (pelvis AP), and 2.1 (lumbar AP) than NRPB-HPE values. The relative higher dose found in this study shows nonoptimization of practice in Nigeria. It is expected that regular dose auditing and dose optimization implementation in Nigeria would lead to lower DAP value, especially in abdomen AP. The 75th percentile DAP distribution reported in this study could be taken as regional diagnostic reference level in the Southwestern Nigeria; however, a more extensive nationwide dose survey is required to establish national reference dose.