In the past 5 y, the number of computed tomography (CT) studies has doubled at Dubai Health Authority hospitals. This situation, along with patient's overdoses reported internationally, has prompted action to establish a system to manage patient doses incurred due to medical imaging practices. In this work, the authors aim to homogenise dose reporting to monitor radiation dose levels and facilitate the establishment of local and national dose reference levels. The two hospitals enrolled in this study are equipped with three CT systems (two 4 slices and one 64 slices). Through the Picture Archive and Communication Systems (PACS) tracking system, it is mandatory to fill CT patient doses in radiology information system (RIS). Dose length product (mGy cm) was recorded for 2502 adult and 178 paediatric patients. All patients' dosimetry data were collected from the RIS by Cogonos statistical software. The PACS data were reviewed to exclude incomplete data. Average and range of effective doses for adult and paediatric patients were calculated using an appropriate weighting factor. Individual accumulated effective doses for adult and paediatric patients were calculated for 4s-scanner-1 only. Adult average effective doses for the head (1482 exams) were 1.23 ± 0.58, 2.84 ± 0.83 and 2.98 ± 1.103 mSv, the chest (545 exams) were 5.39 ± 1.63, 21.85 ± 5.63 and 18.19 ± 3.22 mSv and for the abdomen and pelvis (1183 exams) were 10.85 ± 4.26, 25.66 ± 8.83 and 26.46 ± 13.75 mSv for 4s-scanner-1, 4s-scanner-2 and 64 s, respectively. The paediatric average effective dose for the head (127 exams) was 1.77 ± 0.82 mSv, for the chest (22 exams) was 3.3 ± 1.29 mSv and for the abdomen and pelvis (27 exams) was 6.16 ± 2.64 mSv. Results of individual accumulated effective doses for adult and paediatric patients were presented. PACS dose reporting facilitated dosimetry clinical auditing. Effective doses obtained in this work demonstrated that the results of one scanner were within the international dose levels while the other two scanners were higher. Technical actions are recommended to standardise the dose levels.

No abstract

Background - In PET/CT imaging the amount of 18 F-FDG activity injected to patient is mainly based on the patient body weight (BW) or on body mass index (BMI). Imaging overweight and obese patients using standard protocols results quite often in poor diagnostic images. The purpose of this study was to optimise BMI-based whole body 18 F-FDG PET images obtained from overweight and obese patients and assess the added value in terms of image quality, quantitative accuracy and radiation dose in comparison to BW-based images. Methods - The NEMA-IEC-body phantom was scanned on the mCT 128 slices scanner (Siemens Healthineers). The spheres and background were filed with F-18 activity. Spheres-to-background (2.1kBq/mL) ratio was 4:1. Data was reconstructed using the OSEM-TOF-PSF routine reconstruction (2 iterations, 21 subsets, 3mm Gaussian filter). The optimisation was performed by varying number of iterations, number of subsets, filter’s size and type and matrix size. The phantom images were assessed using contrast recovery coefficients (CRCs). The optimised reconstruction was applied to 17 overweight and obese patients. The optimised BMI-based images and BW-based images were compared visually and using signal-to-noise ratio (SNR), SUVmax and SUVpeak measurements. Results- The visual assessment of the optimised phantom images using 1 iteration, 21 subsets, 3mm Hamming filter showed better image quality and CRC values compared to the routine reconstruction. On patient data, the optimised BMI-based images provided better image quality compared to BW-based images in 87.5% of the overweight cases and 66.7% for obese cases. Compared to BW-based images, the optimised BMI-based images resulted in reduction of 18.6% in SUVmax, 10.6% in SUVpeak and 59% in radiation dose for overweight patients. Similar trends were observed in obese patients. SNR improvement on BMI optimised images over BW images was 55% and 59% on overweight and obese patients, respectively. Conclusions - The optimised BMI-based approach using 1 iteration, 21 subsets, 3mm Hamming filter improves image quality, reduces radiation dose and provides, at least, similar quantitative accuracy compared to the BW-based approach for both overweight and obese patients. These findings are compelling enough support to conducting a full assessment of the approach on a large patient population.