Geoffrey K. Korir

Radiation exposure in interventional procedures

The aim of this study was to estimate radiation doses patients and staff are exposed to during interventional procedures (IPs), compare them with the international diagnostic reference levels and to develop initial National Diagnostic Reference Levels. The IP survey was undertaken as the initial task of which, retrospective data were collected from the only four Kenyan hospitals carrying out interventional radiology and cardiology procedures at the time of the study. Real-time measurement of radiation dose to patients and staff during these procedures was done. To the patients, kerma-area product (KAP) and fluoroscopy time measurements were done using an in-built KAP meter, while peak skin dose (PSD) was measured using slow Extended Dose Range (EDR2(®)) radiographic films. The staff occupational doses were measured using individual thermoluminescence dosemeters. The maximum and minimum KAP values were found to be 137.1 and 4.2 Gy cm(2), while the measured PSD values were 740 and 52 mGy, respectively. The fluoroscopic time range was between 3.3 and 70 min. The staff doses per procedure ranged between 0.05 and 1.41 mSv for medical doctors, 0.03 and 1.16 mSv for nurses, 0.04 and 0.78 mSv for radiographers and 0.04 and 0.88 mSv for clinical staff. The measured patient PSDs were within the threshold limit for skin injuries. However, with the current few IP specialists, an annual increase in workload as determined in the study will result in the International Commission on Radiation Protection annual eye lens dose limit being exceeded by 10 %. A concerted effort is required to contain these dose levels through use of protective gear, optimisation of practice and justification.

Establishment of local diagnostic reference levels in paediatric screen-film radiography at a children's hospital

To assess the frequency of examination, image quality (IQ) and establishment of local diagnostic reference levels (LDRLs) in paediatric radiographic examinations. The X-ray device performance, film reject rate and IQ grading were assessed at Radiology Department of a referral and teaching childrens hospital in Kenya. A questionnaire method was developed and used in recording the exposure factors used to indirectly calculate patient doses. The study established the first age- and technique-specific diagnostic reference levels (DRLs) for paediatric patients with respect to grid and non-grid radiographic techniques. The mean doses in most grid examinations exceeded the available international DRLs. The non-grid radiography imaging technique provided better IQ and an optimal patient dose. In this study, the preliminary age-specific paediatric DRLs, based on the mean values of the dose distribution, have been suggested for the type of examination considered. They form the preliminary LDRLs, which are lower than the few available international DRLs.

PATIENT DOSES USING MULTIDETECTOR COMPUTED TOMOGRAPHY SCANNERS IN KENYA

Assessment of patient dose attributed to multislice computed tomography (CT) examination. A questionnaire method was developed and used in recording the patient dose and scanning parameters for the head, chest, abdomen and lumbar spine examinations. The patient doses due to brain, chest and abdomen examination were above the international diagnostic reference levels (DRLs) by factors of between one and four. The study demonstrated that the use of multislice CT elevates patient radiation dose, justifying the need for local optimised scanning protocols and the use of institutional DRL for dose management without affecting diagnostic image quality.

National diagnostic reference level initiative for computed tomography examinations in Kenya

The purpose of this study was to estimate the computed tomography (CT) examination frequency, patient radiation exposure, effective doses and national diagnostic reference levels (NDRLs) associated with CT examinations in clinical practice. A structured questionnaire-type form was developed for recording examination frequency, scanning protocols and patient radiation exposure during CT procedures in fully equipped medical facilities across the country. The national annual number of CT examinations per 1000 people was estimated to be 3 procedures. The volume-weighted CT dose index, dose length product, effective dose and NDRLs were determined for 20 types of adult and paediatric CT examinations. Additionally, the CT annual collective effective dose and effective dose per capita were approximated. The radiation exposure during CT examinations was broadly distributed between the facilities that took part in the study. This calls for a need to develop and implement diagnostic reference levels as a standardisation and optimisation tool for the radiological protection of patients at all the CT facilities nationwide.

Patient radiation exposure during general fluoroscopy examinations

The purpose of this study was to assess the level of patient radiation dose received in general fluoroscopy examinations, compare the findings with the international diagnostic reference levels (IDRLs), and establish the initial institutional (local) LDRLs. A comprehensive survey was conducted for general fluoroscopy examinations using the medical records of a Radiology Department of a leading regional hospital over a period close to one year. The cumulative reference point air kerma (Ka,r), kerma area product (KAP) and fluoroscopy time (FT) were recorded for six hundred and fifty (30% pediatric and 70% adult) patients undergoing routine fluoroscopy examinations using X‐ray equipment with built‐in integrated dose measuring system. Results which were obtained for adult general fluoroscopy indicated that 83% and 33% were below the IDRLs for KAP and fluoroscopy time, respectively. In children, 60% were found to be below the only available KAP diagnostic reference levels. Local diagnostic reference levels (LDRLs) have been proposed with respect to the missing DRLs for the Ka r, KAP, and fluoroscopy time. The majority of the examinations in the study were performed with longer fluoroscopy time, patient dose values per examination type were found to be broad and the mean values above the international diagnostic reference levels. This calls for proper and improved training and radiation protection skills for the responsible personnel, especially the equipment operators. PACS numbers: 87.53.Bn, 87.59.C‐, 87.59.cf, 87.53.Bn, 87.50.‐a, 87.53.‐j

Frequency and collective dose of medical procedures in Kenya.

AbstractThe first comprehensive national survey on frequency and radiation dose imparted to the population from radiological procedures was carried out in Kenya and reported here. This survey involved assessment of frequency, typical patient radiation exposure, and collective effective dose from general radiography, fluoroscopy, interventional procedures (IPs), mammography, and computed tomography. About 300 x-ray facilities across the country were invited to participate in the survey, and a 31% response was recorded. The individual and collective radiation burdens of more than 62 types of pediatric and adult radiological examinations were quantified using effective and collective dose. The average effective dose for each radiological examination was assessed from the x-ray efficiency performance tests and patient data from over 30 representative radiological facilities. The results found indicated that over 3 million x-ray procedures were performed in 2011, resulting in an annual collective effective dose of 2,157 person-Sv and an annual effective dose per capita of 0.05 mSv. The most frequent examinations were general radiography (94%), computed tomography (3.3%), and fluoroscopy (2.5%). Although the contribution of computed tomography was small in terms of frequency, this procedure accounted for 36% of the effective dose per capita. General radiography was the most frequent type of examination with a contribution of 55% of the effective dose per capita.

Assessment of patient doses during mammography practice at Kenyatta National Hospital.

Background Breast cancer constitutes 21% of all cancer cases and ranks third according to cancer type in Kenya. Mammography therefore remains a powerful radiographic imaging technique for detecting and managing breast cancer. However, the active and radiosensitive glandular tissue calls for the need of an effective quality assurance program. Materials and Methods A questionnaire method was developed and used in recording the displayed patient dose, compressed breast thickness and exposure factors. The average glandular dose, device performance, and film quality grading were also carried out. Results There were 3264 films taken from 1252 women between 25 to 90 years old. The AGD per film was 2.14 (range 0.27-9.43) mGy for the cranio-caudal (CC) projection and 2.44 (range 0.20-10.12) mGy for the medio-lateral oblique (MLO) projection. In this study 17% of CC and 30% of MLO films recorded doses above the 3 mGy American College of Radiology using grid diagnostic reference level. Conclusion In view of the diagnostic dose finding of this study, the variation of mammography imaging techniques revealed the need for imaging guidelines, quality assurance and optimization of mammography practice in Kenya.

Establishing the quality management baseline in the use of computed tomography machines in Kenya

The objective of this study was to assess the level of compliance to quality assurance and image quality standards in computed tomography facilities in Kenyan hospitals. A quality assurance inspection and physical image quality assessment in eighteen representative computed tomography facilities were completed. A quantitative method was developed and used to score the results obtained from the physical image quality measurements using the American Association of Physicists in Medicine (AAPM) water phantom. Inspection was done in order to establish the level of compliance with internationally recognized standards such as those stipulated in the European Guidelines Quality Criteria for Computed Tomography and the International Basic Safety Standards for Protection against Ionizing Radiation. The overall findings placed the national quality management performance at 50±3%, while image quality and quality assurance performance were 61±3% and 37±3%, respectively. The quality assurance assessment benchmarked the countrys level of quality management system compliance in diagnostic radiology. During accreditation appraisal, the scrutiny of scores from each stage in the medical imaging chain per facility will encourage continual implementation of the quality improvement process. PACS number: 87.57.C, 87.57.cf, 87.57.cj, 87.57.cm, 87.57.cp, 87.57.Q, 87.55.N