Use of Multiphase CT Protocols in 18 Countries: Appropriateness and Radiation Doses.

PURPOSE: To assess the frequency, appropriateness, and radiation doses associated with multiphase computed tomography (CT) protocols for routine chest and abdomen-pelvis examinations in 18 countries. MATERIALS AND METHODS: In collaboration with the International Atomic Energy Agency, multi-institutional data on clinical indications, number of scan phases, scan parameters, and radiation dose descriptors (CT dose-index volume; dose-length product [DLP]) were collected for routine chest (n = 1706 patients) and abdomen-pelvis (n = 426 patients) CT from 18 institutions in Asia, Africa, and Europe. Two radiologists scored the need for each phase based on clinical indications (1 = not indicated, 2 = probably indicated, 3 = indicated). We surveyed 11 institutions for their practice regarding single-phase and multiphase CT examinations. Data were analyzed with the Student t test. RESULTS: Most institutions use multiphase protocols for routine chest (10/18 institutions) and routine abdomen-pelvis (10/11 institutions that supplied data for abdomen-pelvis) CT examinations. Most institutions (10/11) do not modify scan parameters between different scan phases. Respective total DLP for 1-, 2-, and 3-phase routine chest CT was 272, 518, and 820 mGy·cm, respectively. Corresponding values for 1- to 5-phase routine abdomen-pelvis CT were 400, 726, 1218, 1214, and 1458 mGy cm, respectively. For multiphase CT protocols, there were no differences in scan parameters and radiation doses between different phases for either chest or abdomen-pelvis CT (P = 0.40-0.99). Multiphase CT examinations were unnecessary in 100% of routine chest CT and in 63% of routine abdomen-pelvis CT examinations. CONCLUSIONS: Multiphase scan protocols for the routine chest and abdomen-pelvis CT examinations are unnecessary, and their use increases radiation dose.

Inadvertent Thyroid Radiation During Computed Tomography of the Chest: A Retrospective Study.

Background: The thyroid, along with the breast, lung, and bone marrow, is among the most radiosensitive organs. This study aims to assess the rate of unnecessary radiation exposure to the thyroid gland in patients who had chest Computed Tomography (CT) at a large teaching hospital. Method: Hospital-based retrospective cross-sectional study on 1,306 patients who underwent chest CT from July 2018 to January 2019. Thyroid gland inclusion along with the CT dose of the studies was evaluated. Data was collected by evaluating chest CT scans from Picture Archive and Communication System (MedWeb). Result: Out of 1306 patients, who had Chest CT scans intravenous iodinated contrast media was used in 95.4% of the CT scans. The thyroid was included in 99.8% of the scans, out of which 76.9% included the whole thyroid gland. Among the patients who had previous CT scans, 75.3% had one previous scan and 24.7% had two previous scans. DLP (Dose Length Product) in mGycm was lower in females (360.33±32) compared to males (426.45±378.4). The lowest DLP value was observed in the pediatric patients in the age range of 1-5 years which was 146.83, while the highest was observed among those above 18 years of age with mean DLP of 418.31. Conclusion: The majority of chest CT scans unnecessarily include the whole thyroid gland, which is one of the most sensitive organs for radiation-induced effects. Authors recommend optimized technique for chest scans to avoid future impacts.

Entrance surface dose measurement in pediatric patients undergoing common diagnostic x-ray examinations in black lion and Yekatit 12 Hospital Addis Ababa, Ethiopia.

BACKGROUND: Early childhood exposure carries an enhanced radiation risk and estimated that the probability of induction of cancer especially leukemia is about two to three times as high as in adults. Hence, dose measurement is mandatory for optimization in radiation protection to comply with international reference levels. OBJECTIVES: To estimate pediatric patient's radiation dose arising from common diagnostic x-ray examinations by measuring Entrance Surface Dose, thereby, to compare the results from established reference values and other published studies. MATERIAL AND METHODS: A cross-sectional study was conducted on pediatric patients under 15 years of age in Black Lion and Yekatite 12 Hospitals on May and August, 2009 respectively. Exposure factors used for commonly performed x-ray examinations like, chest, skull, abdomen, pelvis and spine were obtained from each Hospital. For each examination four age groups 0-1, 1-5, 5-10 and 10-15 years were studied. Entrance Surface Dose in air was measured using dositime dx X-ray Digital Dosimeter and Exposure Time Meter. RESULT: In Black lion hospital, the lowest and the highest calculated mean Entrance Surface Doses in microGY were 104 and 2482 for chest Anteroposterior (0-1) years and lumbo-sacral lateral (10-15) years, respectively. In Yekatit 12 hospital, the lowest and the highest calculated mean Entrance Surface Doses in microGY were 200 and 3570 for chest antrioposterior (0-1) years and lumbo-sacral lateral (10-15)years, respectively. Wide variations of doses for the same type of examination and projection have been detected in each hospital. CONCLUSION: The wider dose variation suggests that there is a pressing need to seek dose optimization to children in order to reduce the detriment caused by the unnecessary high doses imparted to them.

Local diagnostic reference levels for adult posteroanterior (PA) chest x-ray examination in Addis Ababa, Ethiopia.

BACKGROUND: The Local Diagnostic Reference Levels (LDRLs) form an efficient, concise and powerful standard for optimizing the radiation protection of a patient. OBJECTIVES: To calculate the Entrance Surface Doses (ESDs) received by patients undergoing PA chest X-ray examinations in major public hospitals in Addis Ababa, thereby to establish the first Ethiopian LDRLs as part of ongoing dose reduction program. MATERIALS AND METHODS: The entrance dose in air per examination was measured in eight hospitals comprising nine X-ray units and a sample of 192 radiographs. The entrance dose in air was measured using dositime dx X-ray Digital Dosimeter and Exposure Time Meter. The data were analyzedstatistically, and the minimum, median, mean, maximum, and third quartile values of ESDs are reported Finally, the proposed LDRLs are compared with the international reference dose values reported by the Commission for European Community (CEC), the International Atomic Energy Agency (IAEA) and the National Radiological Protection Board (NRPB). RESULTS: The third quartile value of the distribution of mean doses at individual hospitals participating in this survey is found to be 1.08 milligray (mGy). Hospitals mean ESDs for PA chest X-ray examination is found with the range of 0.0.76 to 1.48 mGy. Most of the ESD measured doses were slightly greater than the NRPB, CEC and IAEA reference doses. CONCLUSION: The results of the present study indicate a need for Quality Assurance (QA) programs to be undertaken to avert considerable cost and high patient doses. The results are useful to national and professional organizations and can be used as a baseline upon which future dose measurements may be compared.

Variation of Pediatric Doses Undergoing Digital and Computed Radiography Examination in Addis Ababa, Ethiopia.

BACKGROUND: Various researchers who carried out national and international surveys have reported wide variations in patient dose arising from specific X-ray examinations. Thus, assessment of radiation dose is an essential part in the optimization process. The aim of this study was to compare the entrance surface doses delivered to pediatric patients undergoing digital and computed radiography X-ray examination. MATERIAL AND METHODS: A cross-sectional study was conducted on 389 pediatric X-ray projections less than 15 years of age on eight X-ray machines in Addis Ababa in February 2009 E.C. The tube output of the X-ray machines in air was measured using RaySafe XI dosimeters. Then, entrance surface dose was estimated for common x-ray examinations like chest, skull, extremities and pelvis using established relation between X-ray tube output and radiographic parameters. These data were analyzed statistically using computer (Excel and SPSS method). RESULT: The third quartile estimated ESDs in mGy for both computed and digital radiography examinations of chest (AP) for age (0-1 year) were 0.24 and 0.15, (1-5 year) 0.3 and 0.16. For the age group (5-10 year), it was 1.97 and 0.26 and for the (10-15 year) group, 0.56 and 0.18 respectively. These values were higher than those of the United Nations Scientific Committee's on the Effects of Atomic Radiation's established dose reference levels (in mGy for age (0-1 year) 0.02, (1-5 year) 0.03, (5-10 year) 0.04, and (10-15 year) 0.05 respectively). CONCLUSION: The wider dose variation between computed and digital radiography shows that there is a pressing need to minimize the detriment caused by unnecessary computed radiography.

Pediatric Residents' and Medical Interns' Awareness about Pediatric Ionizing Radiation Dose from Computed Tomography and Its Associated Risks in Tertiary Hospital in Ethiopia.

BACKGROUND: The international literature on physicians' knowledge regarding radiation dosages and risks due to computed tomography showed a widespread underestimation of diagnostic radiation doses. Hence, the objective of this work is to assess the awareness of pediatric residents and medical interns about pediatric CT dose and possible risks. METHODS: A cross-sectional study was conducted on May/2016 among year I to year III pediatric residents and 2015/2016 year medical interns attaching Pediatrics Department during the study period in Tikur Anbessa Specialized Referral and Teaching Hospital. Data was collected by distributing standardized structured questionnaires. Finally, after the data was checked for clarity and completeness, it was analyzed by using SPSS software. RESULT: While the majority (76.3%) of the residents and interns knew that children were more sensitive to radiation than adults, 93.7% did not know that there is currently no annual dose limit set for medical exposure of patients. The majority of the respondents (81.3%) know the risk of cancer from CT scan, but most (60%) of the respondents did not know that many imaging facilities still use adult doses for pediatric patients. Furthermore, 18.8% thought that magnetic resonance imaging involves ionizing radiation, and 8.9% of the physicians associated ultrasound examinations with ionizing radiation. CONCLUSION: Within resident group, since the level of clinical experience did not affect the outcome, we recommend that formal education and training on awareness of radiation with special concern on pediatric population is mandatory especially for pediatric residents and pediatricians who are major caretakers of children.

Visualization, volume and surface area calculation of three dimensional (3D) ultrasound images.

OBJECTIVE: To segment a 3D ultrasound image data that comprises extraction of surface of interests, smoothing of segmented image, thereby to estimate the surface area and volume of segmented 3D objects (e.g. fetus). METHOD: (a) Seeded Region Growing (SRG) together with connectivity and marching cubes algorithms are used to segment the three dimensional (3D) ultrasound image data (I) (b) Using VTK (Visualization Tool Kit) a c++ program was developed which relies on the Maximum Unit Normal Component (MUNC) used for surface area measurement and Divergence Theorem Algorithms (DTA) used for volume estimation. The agreement between the program and the formula was tested on (1) computer generated spheres and cube (2) cylindrical shaped phantoms scanned by ultrasound scanner System Five, GE Vingmed (Horten, Norway) using a 3D annular array of 7.5 MHz. (3) 3D ultrasound fetus using cronbach alpha RESULTS: The cylindrical shaped phantom (diameter 15.4 mm, length. 21.7 mm) with x and y voxel size 1.24921 mm and 0.613032 mm respectively and z voxel size 1.249221 mm yield a percentage error of 5.3% for the surface area and 2.6% for the volume. The volume and surface area of the fetus with x, y, z voxel size 0.465508mm, 0.529645 mm, 1.014201 mm respectively as estimated with the developed program was 3.758ml for volume and 1.937 mm2 fbr surface area, while the measured volume of fetus with EchoPAC-3D was 3.74 ml. CONCLUSIONS: It was concluded that. The agreement between the formula and the program for different shaped objects indicate that the methodology can provide measurements of the volume and the surface area of different anatomical structures.