Estimation of organ-specific cancer and mortality risks associated with common indication-specific CT examinations of the abdominopelvic region.

INTRODUCTION: There is a paucity of large-scale studies reporting organ doses and cancer risks in patients who undergo indication-specific CT examinations. This study estimated organ-specific lifetime attributable risk (LAR) of cancer incidence and mortality among patients who underwent indication-based computed tomography (CT) examinations [(involving abdominopelvic lesion, kidney stones and computed tomography-intravenous urography (CT-IVU)] in about 70% of the functioning CT facilities in Ghana. METHODS: With a total of 1,100 data sets, organ doses were first determined using the National Cancer Institute Dosimetry System for CT (NCICTX) software version 2.1, and LAR values were predicted using the BEIR VII model. RESULTS: The estimated radiation-induced colon cancer risks were likely in 39.4-59.8 out of 100,000 patients who underwent CT because of abdominopelvic lesion. The risk was even higher in CT-IVU examinations (53.3-66.4 patients in 100,000 procedures) but was relatively less (16.8-26.3 patients) in kidney stone procedures. Accordingly, the risk of radiation-induced colon mortality was more common in CT-IVU than in kidney stone procedures (22.7-28.2 versus 7.2-12.5 patients in 100,000 procedures). CONCLUSION: These results call for further optimisation actions for indication-specific CT examinations to appropriately reduce the potential risk levels for patients' protection and safety.

Adult Computed Tomography examinations in Uganda: Towards determining the National Diagnostic Reference Levels.

INTRODUCTION: Diagnostic Reference Levels (DRLs), typically set at the 75th percentile of the dose distribution from surveys conducted across a broad user base using a specified dose-measurement protocol, are recommended for radiological examinations. There is a need to develop and implement DRLs as a standardisation and optimisation tool for the radiological protection of patients at Computed Tomography (CT) facilities. METHODS: This was a retrospective cross-sectional study conducted in seven (7) different CT scan facilities in which participants were recruited by systematic random sampling. The study variables were dose length product (DLP) and volume-weighted CTDI (CTDIvol) for the radiation doses for head, chest, abdomen and lumbar spine CT examinations. The DRLs for CTDIvol and DLP were obtained by calculating the 3rd quartiles of the radiation doses per study site by anatomical region. The national diagnostic reference levels were determined by computation of DRLs using the 75th centile of the median values. RESULTS: A total of 574 patients were examined with an average age of 47.1 years. For CTDIvol estimates; there was a strong positive significant relationship between the CTDIvol and examination mAs (rs = 0.9017, p-value < 0.001), and reference mAs (rs = 0.0.7708, p-value < 0.001). For DLP estimates; there was a moderate positive significant relationships between DLP and total mAs (rs = 0.6812, p-value < 0.001), reference mAs (rs = 0.5493, p-value < 0.001). The DRLs were as follows; for head CT scan - the average median CTDIvol was 56.02 mGy and the DLP was 1260.3 mGy.cm; for Chest CT, the CTDI volume was 7.82 mGy and the DLP was 377.0 mGy.cm; for the abdomen CT, the CTDI volume 12.54 mGy and DLP 1418.3 mGy.cm and for the lumbar spine 19.48 mGy and the DLP was 843 mGy.cm, respectively. CONCLUSION: This study confirmed the need to optimize the CT scan parameters in order to lower the national DRLs. This can be achieved by extensive training of all the CT scan radiographers on optimizing the CT scan acquisition parameters. Continuous dose audits are also advised with new equipment or after every three years to ensure that values out of range are either justified or further investigated.

Towards the establishment of national imaging practice guidelines: A preliminary study of the basic computed tomography imaging protocols in Ghana.

BACKGROUND: There is a need to harmonize imaging practices in computed tomography (CT) imaging. This study, therefore, investigated the variability of the basic imaging protocols used for CT imaging of common indications in Ghana in order to generate recommendations for the development of national imaging practice guidelines in CT imaging. METHOD: A cross-sectional study, utilizing a structured online questionnaire, was undertaken (between December 2018 to March 2019) to collect indication-based imaging protocol data (scan coverage, scan series, image quality requirement, slice thickness, reconstruction, scan mode and orientation, required window, AEC usage, scan and breath hold techniques etc.,) across the various CT facilities in the country. Data were analysed and with experts' input, recommendations were made. RESULTS: The imaging protocols used across the CT facilities in the country were largely similar, with a few variabilities for similar examinations. These variabilities were found in scan coverages, series and slice thicknesses. In particular, for a brain tumour examination, 92% of the 25 facilities used both non-contrast and contrast phases while 8% preferred only the IV contrast phase. Seventy percent of all the facilities (n=10) performing pulmonary angiograms in the country also used a two-sequence scan, and others (30%) worked with only the angiogram phase. A majority (89%) of the 19 facilities that were engaged in CT-IVU procedures also used 3-4 scan phases, while 11% preferred a split-bolus technique. None of the facilities employed the low-dose or ultra-low dose protocol for kidney stone examination. CONCLUSIONS: The study's outcome provides an important preliminary roadmap that could lead to the development of imaging practice guidelines to ensure harmonization of imaging practices to improve the protection and safety of patients across the CT facilities.

Variability of redundant scan coverages along the Z-axis and dose implications for common computed tomography examinations.

BACKGROUND: Scan length optimization is a method of optimization which ensures that, imaging is performed to cover just the area of interest without unnecessarily exposing structures that would not add value to answer a given clinical question. PURPOSE: This study assessed the variability and degree of redundant scan coverages along the z-axis of CT examinations of common indications and the associated radiation dose implications in CT facilities in Ghana for optimization measures to be recommended. METHODS: On reconstructed acquired CT images, the study measured extra distances covered above and below anatomical targets for common indications with calibrated calipers across 25 CT facilities. The National Cancer Institute Dosimetry System for CT (NCICT) (Monte Carlo-based-software) was used to simulate the scanning situations and organ dose implications for scans with and without the inclusion of the redundant scan areas. RESULTS: A total of 1,640 patients' CT data sets were used in this study. The results demonstrated that CT imaging utilized varying scan lengths (16.45±21.0-45.99±4.3 cm), and 70.6% of the scans exceeded their pre-defined anatomic boundaries by a mean range of 2.86±1.07-5.81±1.66 cm, thereby resulting in extra patient radiation dose. Hence, scanning without the redundant coverages could generate a dose length product (DLP) reduction of 17.5%, 18.8%, 15.5% and 9.0% without degrading image quality for brain lesion, lung lesion, pulmonary embolism and abdominopelvic lesion CT imaging, respectively, whilst ensuring organ dose reduction of0.8%-79.1%. CONCLUSION: The study strongly recommends that radiographers should avoid the inclusion of redundant areas in CT examinations to reduce organ doses.

National indication-based diagnostic reference level values in computed tomography: Preliminary results from Ghana.

PURPOSE: This study was conducted to develop national indication-based DRL values for common indications of adult computed tomography (CT) examinations for clinical application in Ghana. MATERIALS AND METHODS: The methodological approach recommended by the International Commission on Radiological Protection (ICRP), Publication 135, for the development of DRLs, was employed. Studies on CT infrastructure, common indications and quality control tests were first undertaken. A sample of 20 CT dose descriptor/quantity data sets were collected from each centre for each indication. Overall, 3960 data sets were collected for all identified common indications from 71.4% of the total CT scanners in Ghana (25/35). The data were collected from image folders reported and accepted by radiologists. The objective image quality was assessed through a signal to noise ratio (SNR) analysis prior to using the data and extracting DRL values. RESULTS: Clinical indications and their respective DRL values in terms of volume weighted CT dose index (CTDIvol) and dose length product (DLP) were cerebrovascular accident (CVA)/stroke (77 mGy; 1313 mGy.cm), head trauma/injury (76 mGy; 1596 mGy.cm), brain tumour/space occupying lesion (SOL) (77 mGy; 2696 mGy.cm), lung tumour/cancer (12 mGy; 828 mGy.cm) and chest lesion with chronic kidney disease (CKD) (13 mGy; 467 mGy.cm). Others were abdominopelvic lesion (17 mGy; 1299 mGy.cm), kidney stones (15 mGy; 731 mGy.cm), urothelial malignancy/CT-intravenous urogram (CT-IVU) (11 mGy; 1449 mGy.cm) and pulmonary embolism (PE) (14 mGy; 942 mGy.cm). CONCLUSION: National Indication-based DRL values developed in this study are recommended to be used to manage CT radiation dose in Ghana.

An Investigation into the Infrastructure and Management of Computerized Tomography Units in Ghana.

INTRODUCTION: In Ghana, there is a need to document computed tomography (CT) infrastructure and management systems for the development of interventions to promote CT practices while ensuring patient protection through the establishment of diagnostic reference levels and improved dose management systems. METHODS: A quantitative inquiry using a descriptive, cross-sectional approach was used to collect data, using a semistructured questionnaire related to CT infrastructure and management from the technical heads responsible for CT scanners. Data collected included the scanner characteristics, basic management system and organizational arrangements, number of attending practitioners, clinical indications for CT examinations, and the operation of CT facilities in Ghana. RESULTS: Of the 35 CT scanners installed across the country, 31 were involved in the study. The majority (29%) were Toshiba models. Equipment slices ranged from 1 to 640, of which 45.2% were 16-slice scanners. Many (n = 28, 90.3%) were functioning, and most were installed in the capital city, Accra. The equipment mean age was 7.3 ± 4.4 years, and 25.6% were 10 or more years old. There were 107 operating radiographers, 60 reporting radiologists, and 10 medical physicists employed across the facilities. A total of 204,760 CT examinations were performed yearly (6.8 CT procedures per 1000 people in Ghana). Head CT procedures were the most common, and suspicion of cerebrovascular accident or stroke (32.8%) was the most common indication. Some basic quality management system and policy driving CT infrastructure in Ghana were lacking. CONCLUSION: The results have provided essential information on the status of CT infrastructure and management systems for policy development and planning in CT facilities in Ghana. This study provides those interested in CT services, jobs, or medical equipment investment in Ghana the information needed to make appropriate decisions.

Status of Quality Management Systems in Computed Tomography Facilities in Ghana.

PURPOSE: To assess the status of quality management systems in computed tomography (CT) facilities in Ghana. METHODS: A questionnaire and quality control measurements were used to assess the status of quality management systems in CT facilities in Ghana. Thirty-one CT facilities took part in the study. The evaluation included quality assurance (QA), quality control (QC), and quality improvement (QI). RESULTS: Seventeen (54.8%) of the 31 CT facilities had a QA-QC committee in place to ensure patient protection. Fifteen facilities (48.4%) had documented protocols for CT scanning. Ten facilities (32.3%) lacked QC assessment and recordkeeping after notable repairs. Regular QC check records were available in 20 (64.5%) facilities. All scanners passed the QC assessments; however, none of the facilities had established local diagnostic reference levels. DISCUSSION: Quality management systems in some Ghanian CT facilities are unsatisfactory; not all facilities have the needed infrastructure in place for quality management system purposes. CONCLUSION: Quality management systems in Ghanaian CT facilities should be strengthened to optimize patient protection and safety with acceptable image quality.

PAEDIATRIC NECK MULTIDETECTOR COMPUTED TOMOGRAPHY: THE EFFECT OF BISMUTH SHIELDING ON THYROID DOSE AND IMAGE QUALITY.

This study investigated the effect of bismuth shielding on thyroid dose and image quality in paediatric neck multidetector computed tomography (MDCT) performed with fixed tube current (FTC) and automatic exposure control (AEC). Four paediatric anthropomorphic phantoms representing the equivalent newborn, 1-, 5- and 10-y-old child were subjected to neck CT using a 16-slice MDCT system. Each scan was performed without and with single- and double-layered bismuth shield placed on the skin surface above the thyroid. Scans were repeated with cotton spacers of 1, 2 and 3 cm thick placed between the skin and shield, to study the effect of skin-to-shielding distance on image noise. Thyroid dose was measured with thermoluminescent dosemeters. The location of the thyroid within the phantom slices was determined by anthropometric data from patients' CT examinations whose body stature closely matched the phantoms. Effective dose (E) was estimated using the dose-length product (DLP) method. Image quality of resulted CT images was assessed through the image noise. Activation of AEC was found to decrease the thyroid dose by 46 % to the 10-y-old phantom subjected to neck CT. When FTC technique is used, single- and double-layered bismuth shielding was found to reduce the thyroid dose to the same phantom by 35 and 47 %, respectively. The corresponding reductions in AEC-activated scans were 60 and 66 %, respectively. Elevation of shields by 1-, 2- and 3-cm cotton spacers decreased the image noise by 69, 87 and 92 %, respectively, for single-layered FTC, without considerably affecting the thyroid dose. AEC was more effective in thyroid dose reduction than in-plane bismuth shields. Application of cotton spacers had no significant impact on thyroid dose, but significantly decreased the image noise.

Medical physics practice and training in Ghana.

Medical physics has been an indispensable and strategic stakeholder in the delivery of radiological services to the healthcare system of Ghana. The practice has immensely supported radiation oncology and medical imaging facilities over the years, while the locally established training programme continues to produce human resource to feed these facilities. The training programme has grown to receive students from other African countries in addition to local students. Ghana has been recognised by the International Atomic Energy Agency as Regional Designated Centre for Academic Training of Medical Physicists in Africa. The Ghana Society for Medical Physics collaborates with the School of Nuclear and Allied Sciences of the University of Ghana to ensure that training offered to medical physicists meet international standards, making them clinically qualified. The Society has also worked together with other bodies for the passage of the Health Profession's Regulatory Bodies Act, giving legal backing to the practice of medical physics and other allied health professions in Ghana. The country has participated in a number of International Atomic Energy Agency's projects on medical physics and has benefited from its training courses, fellowships and workshops, as well as those of other agencies such as International Organization for Medical Physics. This has placed Ghana's medical physicists in good position to practice competently and improve healthcare.

Natural radioactivity levels of some medicinal plants commonly used in Ghana.

Natural radioactivity levels in some selected medicinal plants commonly used in Ghana from the Centre for Scientific Research into Plant Medicine were investigated to determine the activity concentration and the annual committed effective dose due to naturally occurring radionuclides of (238)U, (232)Th and (40)K. The activity concentration was determined using gamma-ray spectrometry. The results of the analysis indicated an average activity concentration of (238)U, (232)Th and (40)K in the medicinal plants to be 31.8±2.8 Bq kg(-1), 56.2±2.3 Bq kg(-1) and 839.8±11.9 Bq kg(-1) respectively. Khaya ivorensis recorded the highest activity concentration of (238)U and (232)Th while Lippia multiflora recorded the highest activity concentrations of (40)K. The total annual committed effective doses ranged from 0.026±0.001 to 0.042±0.002 mSv a(-1) with an average value of 0.035±0.001 mSv a(-1). The average annual committed effective dose due to ingestion of the natural radionuclides in the medicinal plant samples were far below the world average annual committed effective dose of 0.3 mSv a(-1) for ingestion of natural radionuclides provided in UNSCEAR 2000 report. Therefore, the radiological hazard associated with intake of the natural radionuclides in the medicinal plants is insignificant. The results provide baseline values which may be useful in establishing rules and regulations relating to radiation protection as well as developing standards and guidelines for the use of medicinal or herbal plants to the appropriate authorities.

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.

Radiological assessment of the structural shielding adequacy of the radiotherapy facility at Korle-Bu Teaching Hospital, Accra, Ghana.

A (60)Co radiotherapy source with an initial activity of 185 TBq has exhausted its useful half-life and has been replaced with a 222 TBq (60)Co source at the Korle-Bu Teaching Hospital; a radiological assessment was performed to ascertain the shielding integrity of the facility. Dose rate at selected critical positions were calculated for the old and new sources. Dose rate measurements were also performed at these critical locations for the new source. The dose rates at all the critical locations of the public and staff access areas were within the recommended dose rate limit of 0.5 and 7.5 µSv h(-1) for the public and controlled area, respectively. The concrete biological shielding at the facility at the moment is adequate enough to attenuate the gamma photons from the new 222 TBq (60)Co source. High dose rates were recorded at the entrance to the treatment room, it is therefore recommended that optimisation of procedures should be encouraged to restrict activities in this area.

Systematic approach to training occupationally exposed workers in Ghana and the rest of Africa.

The International Basic Safety Standards requires that all personnel on whom protection and safety depends be trained and qualified. The Radiation Protection Institute of the Ghana Atomic Energy Commission has adopted a systematic approach to training those occupationally exposed to ionizing radiation in the course of their work. In collaboration with the International Atomic Energy Agency several training courses have been implemented at the national level and in the African region. From 1993 to 2008, more than 400 occupationally exposed workers in Ghana were trained on radiation safety. Several African regional training events on radiation safety have also been executed with a total participation number of 583 individuals. The training events have contributed towards upgrading the safety culture within institutions that have participated.