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Simulation software has aided the estimation of organ dose from computed tomography (CT) examinations. The aim of this study was to use the CT-Expo (SASCRAD, Fritz-Reuter-Weg, Buchholz, Germany) software to determine volume CT dose index (CTDI vol), dose length product (DLP), organ dose and effective dose. Methods: A total of 171 patient data were retrieved from a Toshiba Aquillion 16-slice CT scanner (Toshiba Corp., Tokyo, Japan) representing CT unit A and a Philips Brilliance 16-slice CT scanner (Konin klijke Philips N.V., Amsterdam, Netherlands) representing CT unit B and a CT-Expo spreadsheet was used to estimate the dose delivered. Results: Head CT scans were the most frequently seen (64%) at the 2 facilities studied. The CT parameters of peak kilovoltage (kVp) and pitch between the 2 units were statistically different (p<0.05). There was no significant difference in CTDI vol between CT unit A and B (p=0.199). A comparison of CTDI vol and DLP of CT units A and B with other studies revealed no statistically significant difference (p<0.05). The mean effective dose (E) for the abdomen was greater compared with other studies, but without a statistically significant difference (p<0.05). Furthermore, no significant difference in organ dose was seen between CT units A and B (p=0.677). A comparison of organ dose with other studies indicated no relevant difference (p<0.05). Conclusion: The CT-Expo software showed good results with the imPACT software (ImPACT scanner evaluation group, London, UK). CT unit A had greater differences in CTDI vol and DLP compared with unit B. This difference could be associated with the significant difference seen in the kVp and pitch of both scanners.

The magnitude of radiation dose imparted to patients who underwent Head Computed Tomography examination in a large tertiary hospital in South-Southern Nigeria has been estimated. CT-ExPO dosimetry software was used to determine the effective and organ doses to the head region of 40 adult patients. Scanning parameters were retrieved from the CT monitor for both contrast-enhanced and non-contrast head CT examinations. The tube potential ranged from 100 kVp to 120 kVp, while the mAs ranged from 127 mAs to 202 mAs. The mean values of the volume Computed Tomography Dose Index (CTDI vol) and Dose Length Product (DLP) for the contrast-enhanced Head CT examination were 166.4 ± 39.6 mGy and 3568.6 ± 756.1 mGy•cm, respectively, while for the non-contrast examination they were 86.6 ± 30.4 mGy and 2102.3 ± 870.3 mGy•cm, respectively. The effective doses were higher for the contrast-enhanced study than for the non-contrast study by a factor of 1.6. Results were compared with the European Union reference doses and other published data and were found to be higher. Doses to the organs which comprise of brain, red bone marrow, thyroid and eye lens were also estimated. The high variation in the doses in this study may be due to differences in imaging protocols such as large range of mAs and scan lengths and also the algorithm of the scanner.

Objectives. Large percentages of X-ray facilities in Nigeria do not use radiation monitoring device; a few percentage that use them do not evaluate or carryout out assessment programs to ascertain the detriment to occupationally exposed workers. This study was aimed at evaluating dose reports from 2013 to 2016 for personnel who operate radiation facilities and those that work within radiation field during certain X-ray procedures/examinations in the department of radiology and dentistry respectively; to ascertain if there is correlation between personnel dose and workload in both department and to determine if dose records are within acceptable limit recommended by the International Atomic Energy Agency (IAEA) safety series. Methods. Direct Ion Storage (DIS) dosimeter was used for a total of 35 occupationally exposed personnel who work in the department of radiology and dentistry. The DIS dosimeter was read every two months and results were authomatically saved on the instadose TM platform. Results. The mean (total) dose in radiology department for the first, second, third and fourth year was 0.17 ± 0.08 (3.52) mSv, 0.08 ± 0.03 (0.77) mSv, 0.07 ± 0.04 (0.72) mSv and 0.07 ± 0.05 (0.55) mSv and in Dentistry was 0.08 ± 0.02 (0.73) mSv, 0.05 ± 0.02 (0.42) mSv, 0.05 ± 0.02 (0.24) mSv and 0.07 ± 0.04 (0.34) mSv; respectively. There was significant difference in mean personnel dose from 2013-2016 in Radiology (p=0.028) and in Dentistry Department (p=0.004). Correlation of workload and personnel dose in Radiology (p=0.240) and Dentistry Department (p=0.765) wasn't significant. There was no correlation in mean dose between both department (p=0.256). Conclusion. Overall mean dose in both department for occupationally exposed personnel were below IAEA annual dose limit of 20 mSv averaged over a period of 5 consecutive years. Dose reports of personnel in both department reduced as the year progressed due to radiation safety awareness.

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