Radiation dose to breast during digital mammography in Tanzania.

The aim of this study was to evaluate the mean glandular dose (MGD), to assess the potential for optimization, and to propose diagnostic reference levels (DRLs). MGD was estimated from air kerma measurements and patient information collected during mammography examinations. The 75th percentile values were determined as the third quartile of the median MGD values for all hospitals, and DRLs set as 75th percentile of MGD values. The estimated median values of MGD ranged from 1.5 to 3.9 mGy for craniocaudal projection for median range of 15-59 mm compressed breast thickness (CBT). For a CBT range of 15-63 mm, the median MGD value was 1.5-5.1 mGy for medio-lateral oblique projection. Comparison with other studies showed that the MGD values obtained in this study were relatively high. The magnitude and wide variation of the exposure parameters suggest existing potential for optimization. The training of radiology staff was identified as a top priority.

Entrance surface air kerma to patients during digital radiographic examinations in Tanzania.

The aim of this study was to determine the entrance surface air kerma (ESAK) in adult patients during digital radiography and to evaluate the optimisation potential in five common X-ray examinations in Tanzania. Based on a sample of 240-610 patients, ESAK was estimated using X-ray tube output measurements, patient information and backscatter factors. The results show that the mean ESAK values were higher or comparable to data from the literature. The diagnostic reference values of ESAK for digital radiography were 0.31 mGy (chest PA), 4 mGy (lumbar spine AP), 5.4 mGy (lumbar spine LAT), 3.8 mGy (abdomen AP) and 2.4 mGy (pelvis AP). For computed radiography, the mean ESAK ranges were 0.44-0.57 mGy (thoracic AP), 3.59-3.72 mGy (lumbar spine AP), 6.16-6.35 mGy (lumbar spine LAT), 3.89-3.44 mGy (abdominal AP) and 2.92-3.47 mGy (pelvic AP). In conclusion, high ESAK variations show the potential for optimising protection in digital radiology.

Radiation exposure during CT procedures in Tanzania.

The aim of this study was to evaluate optimisation status during common computed tomography (CT) procedures by determining values of volume computed tomography dose index (CTDIvol) and dose-length product (DLP) per examination. Patient and exposure data were collected from the CT console during various CT procedures. The results show that variations in CTDIvol and DLP values were mainly because of differences in the techniques used. The 75th percentile values were set as the third quartile of the median CTDIvol or DLP values for all hospitals. These values of 40.9, 9.0, 9.4 and 16.2 mGy for CTDIvol were determined for head, high-resolution chest, abdomen-pelvis and lumbar spine, respectively. The corresponding DLP values for the same sequence of CT procedures were 900, 360, 487 and 721 mGy.cm, respectively. The updated results provide a basis for optimising the procedures of CT in this country.

Determination of Dose Distributions by Monte-Carlo Simulation of 6 MV Photon Beam of Varian VitalBeam Accelerator Using Geant4 Multithreaded Code.

Background: Accuracy of dose delivery in radiation therapy is a primary requirement for effective cancer treatment. In practice, dose delivery accuracy of ±5% is desired. To achieve this accuracy level, an accurate method for calculating the dose distributions in the tumor volume is required. Monte-Carlo method is one of the methods considered to be the most accurate for calculating dose distributions. Materials and Methods: G4 linac-MT code was used to simulate a 6 MV photon beam. The initial electron beam parameters were tuned to validate the beam modeling from depth doses and beam profile. The dose distributions measured in water phantom were compared to the calculated dose distributions based on gamma index criterion. Results: The beam tuning showed the initial electron energy, sigma and full width at half maximum of 6.2 MeV, 0.8 MeV, and 1.18 mm, respectively, best match the measured dose distributions. The gamma index tests showed the calculated depth doses and beam profile were generally comparable with measurements, passing the standard acceptance criterion of 2%/2 mm. The simulated photon beam was justified by the index of beam quality, which showed excellent agreement with measured doses with a discrepancy of 0.1%. Conclusion: The observed agreement confirm the accuracy of the simulated 6 MV photon beam. It can therefore be used as radiation source for calculating dose distributions and further investigations aimed at improving dose delivery and planning in cancer patients.

OCCUPATIONAL EXPOSURE TO EXTERNAL IONISING RADIATION IN TANZANIA (2011-17).

The objectives of this paper were to evaluate the occupational radiation exposure data from 2011 to 2017 and to compare the results with status in 1996-2010 periods. The evaluation was performed in terms of annual collective effective dose, the average annual effective dose, the individual dose distribution ratio and the annual collective effective dose distribution ratio. Irrespective of work category, the results indicate that the average effective dose ranged from 0.64 to 1.55 mSv and broadly comparable to data in the previous analysis. Over seven year period, the maximum annual individual dose was 4 mSv and therefore below the dose limit of 20 mSv y-1. The impact of radiological practice on the exposed population was <1.1 person.Sv. The results demonstrate satisfactory radiation protection conditions at workplaces, a situation which is mainly explained by the existing effective regulatory enforcement and improved workers' awareness.

CHALLENGES IN CLINICAL PRACTICE OF CR MAMMOGRAPHY IN TANZANIA.

The aim of this study was to evaluate the clinical practice of CR mammography in Tanzania. The equipment performance and operational conditions were studied; and mean glandular dose (DG) estimated to 75 women undergoing diagnosis at three mammography facilities. All mammograms during this study were reported to be useful for the intended diagnosis. The median DG for craniocaudal and mediolateral oblique projections ranged from 1.27 ± 0.18 mGy to 1.9 ± 0.27 mGy and from 1.3 ± 0.18 mGy to 1.9 ± 0.27 mGy, respectively, and were below the national regulatory guidance of 2.5 mGy. Despite this positive result, unavoidable inappropriate use of beam quality and tube loading settings which could have been through appropriate staff training and performing routine quality control were not uncommon. This work provides an insight of current operational conditions of CR in Tanzania and what strategy should be employed to this service to improve patient care in the country.

Review of the current status of radiation protection in diagnostic radiology in Africa.

The aim of this paper is to review the available published studies from African countries on patient doses and medical radiation protection and identify strengths, weaknesses, and challenges. Papers on radiation doses to patients published until 2016 pertaining to studies in African countries were reviewed. Radiography, interventional radiology, computed tomography (CT), and mammography modalities were covered. In radiography, the entrance surface air kerma values were below the established diagnostic reference levels (DRLs) provided by the International Atomic Energy Agency, European Commission, and National Council on Radiation Protection and Measurements. Patient and staff doses in interventional procedures were not on the higher side when compared with other published reports from developed countries. The dose length product values in CT in many situations were higher than established DRLs. In mammography, the variations of clinical image quality and dose to standard breast between African countries and other countries were insignificant. In conclusion, like in any continent, not all countries in Africa are active, but some have produced good results. The potential for optimization of radiation protection using simple and inexpensive techniques has been demonstrated. The lack of medical physicists is one of the important challenges.

Defining the diagnostic divide: an analysis of registered radiological equipment resources in a low-income African country.

INTRODUCTION: Diagnostic radiology is recognised as a key component of modern healthcare. However there is marked inequality in global access to imaging. Rural populations of low- and middle-income countries (LMICs) have the greatest need. Carefully coordinated healthcare planning is required to meet the ever increasing global demand for imaging and to ensure equitable access to services. However, meaningful planning requires robust data. Currently, there are no comprehensive published data on radiological equipment resources in low-income countries. The aim of this study was to conduct the first detailed analysis of registered diagnostic radiology equipment resources in a low-income African country and compare findings with recently published South African data. METHODS: The study was conducted in Tanzania in September 2014, in collaboration with the Tanzanian Atomic Energy Commission (TAEC), which maintains a comprehensive database of the country's registered diagnostic imaging equipment. All TAEC equipment data were quantified as units per million people by imaging modality, geographical zone and healthcare sector. RESULTS: There are 5.7 general radiography units per million people in the public sector with a relatively homogeneous geographical distribution. When compared with the South African public sector, Tanzanian resources are 3-, 21- and 6-times lower in general radiography, computed tomography and magnetic resonance imaging, respectively. CONCLUSION: The homogeneous Tanzanian distribution of basic public-sector radiological services reflects central government's commitment to equitable distribution of essential resources. However, the 5.7 general radiography units per million people is lower than the 20 units per million people recommended by the World Health Organization.

Application of off-line image processing for optimization in chest computed radiography using a low cost system.

 The objective of this study was to improve the visibility of anatomical details by applying off-line postimage processing in chest computed radiography (CR). Four spatial domain-based external image processing techniques were developed by using MATLAB software version 7.0.0.19920 (R14) and image processing tools. The developed techniques were implemented to sample images and their visual appearances confirmed by two consultant radiologists to be clinically adequate. The techniques were then applied to 200 chest clinical images and randomized with other 100 images previously processed online. These 300 images were presented to three experienced radiologists for image quality assessment using standard quality criteria. The mean and ranges of the average scores for three radiologists were characterized for each of the developed technique and imaging system. The Mann-Whitney U-test was used to test the difference of details visibility between the images processed using each of the developed techniques and the corresponding images processed using default algorithms. The results show that the visibility of anatomical features improved significantly (0.005 ≤ p ≤ 0.02) with combinations of intensity values adjustment and/or spatial linear filtering techniques for images acquired using 60 ≤ kVp ≤ 70. However, there was no improvement for images acquired using 102 ≤ kVp ≤ 107 (0.127 ≤ p ≤ 0.48). In conclusion, the use of external image processing for optimization can be effective in chest CR, but should be implemented in consultations with the radiologists.

Quality Control Measures in Tanzania: Is it Done?

BACKGROUND: Regular implementation of a quality control (QC) programme in diagnostic radiology is vital if consistent optimal equipment performance, quality images, and accurate diagnosis at optimum radiation dose and costs are to be achieved. This highlighted the necessity for the Tanzania Atomic Energy Commission (TAEC) to establish a training programme to enable radiographers to implement a QC programme in their departments because there are no clinical medical physicists in diagnostic radiology in the country. However, the status of programme implementation is not precisely known. AIM: The aim of this study was to investigate the status of implementation of the QC measures as performed by radiographers in diagnostic radiography departments in Tanzania. METHOD: A quantitative cross-sectional survey, using a questionnaire, was conducted on a sample of 84 radiographers who had been trained in the QC programme and who were practising in 54 hospitals within Tanzania. RESULTS: A large number of respondents were not implementing the following QC tests: tube output, kV, mAs and timer (94%), collimation (53.5%), and densitometry and sensitometry (87.7%). The tests for film viewing box and lead rubber protective apparel were not implemented by 64.2% and 59% of the respondents, respectively. The cassette inspection and darkroom inspection were reported as being implemented by most respondents, although the testing was not observing the recommended schedule. Furthermore, the departments had no records and procedures for the QC programme, and only the locally improvized QC test tools were reported to be available. CONCLUSION: The QC training objectives of TAEC have not been largely achieved because radiographers are not adequately implementing the QC programme. Without the QC programme in place, equipment malfunctioning will not be revealed at an early stage, and this can cause poor image quality and/or higher dose to patients. Therefore, active involvement of the TAEC, the ministry of health, hospital management teams, and radiographers is desirable to achieve full implementation of the programme.

IAEA survey of paediatric computed tomography practice in 40 countries in Asia, Europe, Latin America and Africa: procedures and protocols.

OBJECTIVE: To survey procedures and protocols in paediatric computed tomography (CT) in 40 less resourced countries. METHODS: Under a project of the International Atomic Energy Agency, 146 CT facilities in 40 countries of Africa, Asia, Europe and Latin America responded to an electronic survey of CT technology, exposure parameters, CT protocols and doses. RESULTS: Modern MDCT systems are available in 77 % of the facilities surveyed with dedicated paediatric CT protocols available in 94 %. However, protocols for some age groups were unavailable in around 50 % of the facilities surveyed. Indication-based protocols were used in 57 % of facilities. Estimates of radiation dose using CTDI or DLP from standard CT protocols demonstrated wide variation up to a factor of 100. CTDI(vol) values for the head and chest were between two and five times those for an adult at some sites. Sedation and use of shielding were frequently reported; immobilisation was not. Records of exposure factors were kept at 49 % of sites. CONCLUSION: There is significant potential for improvement in CT practice and protocol use for children in less resourced countries. Dose estimates for young children varied widely. This survey provides critical baseline data for ongoing quality improvement efforts by the IAEA.

IAEA survey of pediatric CT practice in 40 countries in Asia, Europe, Latin America, and Africa: Part 1, frequency and appropriateness.

OBJECTIVE: The purpose of this study was to assess the frequency of pediatric CT in 40 less-resourced countries and to determine the level of appropriateness in CT use. MATERIALS AND METHODS: Data on the increase in the number of CT examinations during 2007 and 2009 and appropriate use of CT examinations were collected, using standard forms, from 146 CT facilities at 126 hospitals. RESULTS: The lowest frequency of pediatric CT examinations in 2009 was in European facilities (4.3%), and frequencies in Asia (12.2%) and Africa (7.8%) were twice as high. Head CT is the most common CT examination in children, amounting to nearly 75% of all pediatric CT examinations. Although regulations in many countries assign radiologists with the main responsibility of deciding whether a radiologic examination should be performed, in fact, radiologists alone were responsible for only 6.3% of situations. Written referral guidelines for imaging were not available in almost one half of the CT facilities. Appropriateness criteria for CT examinations in children did not always follow guidelines set by agencies, in particular, for patients with accidental head trauma, infants with congenital torticollis, children with possible ventriculoperitoneal shunt malfunction, and young children (< 5 years old) with acute sinusitis. In about one third of situations, nonavailability of previous images and records on previously received patient doses have the potential to lead to unnecessary examinations and radiation doses. CONCLUSION: With increasing use of CT in children and a lack of use of appropriateness criteria, there is a strong need to implement guidelines to avoid unnecessary radiation doses to children.

Image quality and dose in mammography in 17 countries in Africa, Asia and Eastern Europe: results from IAEA projects.

PURPOSE: The objective is to study mammography practice from an optimisation point of view by assessing the impact of simple and immediately implementable corrective actions on image quality. MATERIALS AND METHODS: This prospective multinational study included 54 mammography units in 17 countries. More than 21,000 mammography images were evaluated using a three-level image quality scoring system. Following initial assessment, appropriate corrective actions were implemented and image quality was re-assessed in 24 units. RESULTS: The fraction of images that were considered acceptable without any remark in the first phase (before the implementation of corrective actions) was 70% and 75% for cranio-caudal and medio-lateral oblique projections, respectively. The main causes for poor image quality before corrective actions were related to film processing, damaged or scratched image receptors, or film-screen combinations that are not spectrally matched, inappropriate radiographic techniques and lack of training. Average glandular dose to a standard breast was 1.5 mGy (mean and range 0.59-3.2 mGy). After optimisation the frequency of poor quality images decreased, but the relative contributions of the various causes remained similar. Image quality improvements following appropriate corrective actions were up to 50 percentage points in some facilities. CONCLUSIONS: Poor image quality is a major source of unnecessary radiation dose to the breast. An increased awareness of good quality mammograms is of particular importance for countries that are moving towards introduction of population-based screening programmes. The study demonstrated how simple and low-cost measures can be a valuable tool in improving of image quality in mammography.

Performance evaluation of three computed radiography systems using methods recommended in American Association of Physicists in Medicine Report 93.

The performances of three clinical computed radiography (CR) systems, (Agfa CR 75 (with CRMD 4.0 image plates), Kodak CR 850 (with Kodak GP plates) and Kodak CR 850A (with Kodak GP plates)) were evaluated using six tests recommended in American Association of Physicists in Medicine Report 93. The results indicated variable performances with majority being within acceptable limits. The variations were mainly attributed to differences in detector formulations, plate readers' characteristics, and aging effects. The differences of the mean low contrast scores between the imaging systems for three observers were statistically significant for Agfa and Kodak CR 850A (P=0.009) and for Kodak CR systems (P=0.006) probably because of the differences in ages. However, the differences were not statistically significant between Agfa and Kodak CR 850 (P=0.284) suggesting similar perceived image quality. The study demonstrates the need to implement quality control program regularly.

Initial quality performance results using a phantom to simulate chest computed radiography.

The aim of this study was to develop a homemade phantom for quantitative quality control in chest computed radiography (CR). The phantom was constructed from copper, aluminium, and polymenthylmethacrylate (PMMA) plates as well as Styrofoam materials. Depending on combinations, the literature suggests that these materials can simulate the attenuation and scattering characteristics of lung, heart, and mediastinum. The lung, heart, and mediastinum regions were simulated by 10 mm x 10 mm x 0.5 mm, 10 mm x 10 mm x 0.5 mm and 10 mm x 10 mm x 1 mm copper plates, respectively. A test object of 100 mm x 100 mm and 0.2 mm thick copper was positioned to each region for CNR measurements. The phantom was exposed to x-rays generated by different tube potentials that covered settings in clinical use: 110-120 kVp (HVL=4.26-4.66 mm Al) at a source image distance (SID) of 180 cm. An approach similar to the recommended method in digital mammography was applied to determine the CNR values of phantom images produced by a Kodak CR 850A system with post-processing turned off. Subjective contrast-detail studies were also carried out by using images of Leeds TOR CDR test object acquired under similar exposure conditions as during CNR measurements. For clinical kVp conditions relevant to chest radiography, the CNR was highest over 90-100 kVp range. The CNR data correlated with the results of contrast detail observations. The values of clinical tube potentials at which CNR is the highest are regarded to be optimal kVp settings. The simplicity in phantom construction can offer easy implementation of related quality control program.

Patient doses in radiographic examinations in 12 countries in Asia, Africa, and Eastern Europe: initial results from IAEA projects.

OBJECTIVE: The purpose of this study was to survey image quality and the entrance surface air kerma for patients in radiographic examinations and to perform comparisons with diagnostic reference levels. SUBJECTS AND METHODS: In this multinational prospective study, image quality and patient radiation doses were surveyed in 12 countries in Africa, Asia, and Eastern Europe, covering 45 hospitals. The rate of unsatisfactory images and image quality grade were noted, and causes for poor image quality were investigated. The entrance surface doses for adult patients were determined in terms of the entrance surface air kerma on the basis of X-ray tube output measurements and X-ray exposure parameters. Comparison of dose levels with diagnostic reference levels was performed. RESULTS: The fraction of images rated as poor was as high as 53%. The image quality improved up to 16 percentage points in Africa, 13 in Asia, and 22 in Eastern Europe after implementation of a quality control (QC) program. Patient doses varied by a factor of up to 88, although the majority of doses were below diagnostic reference levels. The mean entrance surface air kerma values in mGy were 0.33 (chest, posteroanterior), 4.07 (lumbar spine, anteroposterior), 8.53 (lumbar spine, lateral), 3.64 (abdomen, anteroposterior), 3.68 (pelvis, anteroposterior), and 2.41 (skull, anteroposterior). Patient doses were found to be similar to doses in developed countries and patient dose reductions ranging from 1.4% to 85% were achieved. CONCLUSION: Poor image quality constitutes a major source of unnecessary radiation to patients in developing countries. Comparison with other surveys indicates that patient dose levels in these countries are not higher than those in developed countries.