Optimisation of patient protection and image quality in diagnostic radiology.

OBJECTIVE: To determine the examination frequencies, quality of radiographic images and the entrance surface dose (ESD) in patients undergoing general radiographic examinations. DESIGN: Prospective study on the device performance, film reject rate, patient dose, and image quality during the use of standard and fast speed film screen combination. SETTING: Radiology Department of Kenyatta National Hospital, a referral, teaching and research hospital in Kenya. SUBJECTS: A total of 837 adult and 229 paediatric patients undergoing diagnostic examinations were assessed for patient dose and image quality. INTERVENTIONS: The X-ray tube output measurements and X-ray exposure parameters were determined. The patients ESD on standard 200 and fast 400 speed film screen combination was determined. The radiographic image quality was assessed. MAIN OUTCOME MEASURES: The findings were compared with the international diagnostic reference levels (DRL's) for determination of dose optimisation in diagnostic radiography. RESULTS: The relative frequency of examination was 80% and 20% for adults and paediatric patients respectively. The image quality improvement by 13% was achieved and patient dose reduction range of 31% to 77%. CONCLUSIONS: The patient dose reduction and image quality was achieved through a quantitative quality control (QC) assessment of processes involved in producing radiographs. The study leads to the introduction of the concept of plan- do-check-act on QC results and optimise with a view of patient dose reduction. The department appreciated the value of a quality assurance (QA) programme and continues to collect data for establishment of DRL's.

A survey of computed tomography imaging techniques and patient dose in Kenya.

OBJECTIVES: To assess the level of patient dose in Computed Tomography examination in Kenya, compare with the international diagnostic reference levels and establish the initial national diagnostic reference levels. DESIGN: The patient doses for brain, chest, abdomen and pelvis examinations were assessed using typical exposure factors on head and body dosimetry phantoms. A log normal graphical method was developed and used in deriving the initial national diagnostic reference levels for the two dose quantities. SETTING: Twenty one representative Computed Tomography facilities at different hospitals and clinics. SUBJECTS: A questionnaire method was developed and used in recording the scanning parameters for head, chest, abdomen and pelvis adult examinations at each facility. RESULTS: The radiation exposure from Computed Tomography examinations was determined to be below the weighted Computed Tomography Dose Index (CTDIw) and Dose Length Product (DLP) reference levels by 90% and 62% respectively. CONCLUSION: The mean CTDIw measurements for the adult patients were below Diagnostic Reference levels (DRLs). The mean DLP values for adult patients in some examination were above DRLs, with large variations of up to a factor of eleven. This indicates the need for local optimised scanning protocols and use of local diagnostic reference level in order to reduce patient doses without affecting diagnostic image quality.

Chlamydia as a cause of late neonatal pneumonia at Kenyatta National Hospital, Nairobi.

BACKGROUND: Neonatal pneumonia is a common cause of morbidity and mortality all over the world. The problem is known to be higher in resource poor third world countries. Organisms (such as chlamydia) not covered by routine laboratory tests and regular antibiotic regimes may frequently contribute towards the causation of late neonatal pneumonia. It is therefore useful to gather epidemiological evidence to guide in the routine diagnosis and treatment of such infections. OBJECTIVE: To determine the prevalence of chlamydia associated pneumonia among infants developing the disease between the 7th and 30th days of life (late neonatal pneumonia). DESIGN: Cross sectional survey. SETTING: Newborn Unit, Kenyatta National Hospital. SUBJECTS: Fifty two newborns clinically diagnosed as having late neonatal pneumonia. They were all subjected to chest X-rays to confirm the clinical diagnosis. Nasopharyngeal aspirates for chlamydia antigen detection tests were then performed on all patients. The study was undertaken during the months of September through to November 2000. MAIN OUTCOME MEASURES: The proportion of newborns with late neonatal pneumonia that have chlamydia trachomantis as the sole or contributory causative agent. RESULTS: Fifty two newborns of postnatal age between seven and 30 days were recruited. Their sex distribution was about 1:1. Thirty three (63.5%) of these infants were found with chlamydia in their upper airways. Thirty out of 47 available chest X-rays, representing 63.8% had evidence of interstitial pneumonitis. Chlamydia associated pneumonia indicated by the presence of both interstitial pneumonia and colonization of the upper air ways was present in 24 out of 47 patients, 51% of the total cases of late neonatal pneumonia. When X-rays alone were compared with our gold standard for the diagnosis of chlamydia pneumonia (radiology and colonization), we computed a sensitivity of 100%, specificity 73%, negative predictive value 100% and positive predictive value of 80%. Mode of delivery, birth weight and gestation had no association with nasopharyngeal colonization by chlamydia or actual diagnosis of chlamydia pneumonia. CONCLUSION: The prevalence of chlamydia associated infection among newborns with late neonatal pneumonia at Kenyatta National Hospital is 51%, eight times more than that reported elsewhere. Chest X-rays appear to be a reliable diagnostic tool in this group. The use of antichlamydial drugs in addition to the regular antibiotics whenever a diagnosis of late neonatal pneumonia is made is justifiable.

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 children's 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.

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.

Paediatric CT examinations in 19 developing countries: frequency and radiation dose.

The aims of this study were to investigate the frequency of computed tomography (CT) examinations for paediatric patients below 15 y of age in 128 CT facilities in 28 developing countries of Africa, Asia and Eastern Europe and to assess the magnitude of CT doses. Radiation dose data were available from 101 CT facilities in 19 countries. The dose assessment was performed in terms of weighted CT dose index (CTDI(w)), volume CT index and dose length product (DLP) for chest, chest (high resolution), lumbar spine, abdomen and pelvis CT examinations using standard methods. The results show that on average the frequency of paediatric CT examinations was 20, 16 and 5 % of all CT examinations in participating centres in Africa, Asia and Eastern Europe, respectively. Eleven CT facilities in six countries were found to use adult CT exposure parameters for paediatric patients, thus indicating limited awareness and the need for optimisation. CT images were of adequate quality for diagnosis. The CTDI(w) variations ranged up to a factor of 55 (Africa), 16.3 (Asia) and 6.6 (Eastern Europe). The corresponding DLP variations ranged by a factor of 10, 20 and 8, respectively. Generally, the CTDI(w) and DLP values in Japan are lower than the corresponding values in the three regions in this study. The study has indicated a stronger need in many developing countries to justify CT examinations in children and their optimisation. Awareness, training and monitoring of radiation doses is needed as a way forwards.

Patient doses in CT examinations in 18 countries: initial results from International Atomic Energy Agency projects.

The purpose of this prospective study at 73 facilities in 18 countries in Africa, Asia and Eastern Europe was to investigate if the CT doses to adult patients in developing countries are higher than international standards. The dose assessment was performed in terms of weighted computed tomography dose index (CTDIw) and dose length product (DLP) for chest, chest (high resolution), lumbar spine, abdomen and pelvis CT examinations using standard methods. Except in one case, the mean CTDIw values were below diagnostic reference level (DRL) while for DLP, 17 % of situations were above DRLs. The resulting CT images were of adequate quality for diagnosis. The CTDIw and DLP data presented herein are largely similar to those from two recent national surveys. The study has shown a stronger need to create awareness and training of radiology personnel as well as monitoring of radiation doses in many developing countries so as to conform to the ALARA principle.