Measurement of radiation doses in the most frequent simple examinations in paediatric radiology and its dependence on patient age

Reducing the Breast Cancer Risk and Radiation Dose of Radiography for Scoliosis in Children: A Phantom Study

Full-spinal radiographs (FRs) are often the first choice of imaging modality in the investigation of scoliosis. However, FRs are strongly related to breast cancer occurrence due to multiple large-field radiographic examinations taken during childhood and adolescence, which may increase the risk for breast cancer in adulthood among women with scoliosis. The purpose of this study was to consider various technical parameters to reduce the patient radiation dose of FRs for scoliosis. To evaluate breast surface doses (BSDs) in FRs, radio photoluminescence dosimeters were placed in contact with a child phantom. Using the PC-based Monte Carlo (PMC) program for calculating patient doses in medical X-ray examinations, the breast organ dose (BOD) and the effective dose were calculated by performing Monte Carlo simulations using mathematical phantom models. The BSDs in the posteroanterior (PA) view were 0.15-0.34-fold those in the anteroposterior (AP) view. The effective dose in the PA view was 0.4-0.61-fold that in the AP view. BSD measurements were almost equivalent to the BODs obtained using PMC at all exposure settings. During FRs, the PA view without an anti-scatter grid significantly reduced the breast dose compared to the AP view with an anti-scatter grid.

Theoretical breast cancer induction risk from thoracic spine CT in female pediatric trauma patients

OBJECTIVES

To quantify the radiation dose received during thoracic spine computed tomography (CT) versus plain radiographs as well as the theoretical risk of breast cancer induction in a pediatric trauma population.

METHODS

A retrospective evaluation of 179 female pediatric trauma patients who received CT or plain radiographs for clearance of the thoracic spine was performed. Subjects were secondarily grouped as children (0-<12 years) or adolescents (≥12-17.9 years). Radiation doses were calculated by using the ImPACT Patient Dosimetry Calculator. Excess absolute risk (EAR) of induction of breast cancer was determined by multiplying the radiation dose by breast cancer induction rates taken from the National Academy's Biological Effects of Ionizing Radiation Committee's seventh report.

RESULTS

The average radiation dose to the breast from a thoracic spine CT was 41.1 (SD 11.4) mSv and 1.8 (SD 0.9) mSv for plain radiographs. The EAR for plain radiographs was 2.7 (95% confidence interval [CI] 2.48-2.85) excess cases of breast cancer per 10 000 studies for female children and 1.4 (95% CI 1.14-1.55) for female adolescents. The breast cancer EAR for thoracic spine CT was significantly higher -79.6 (95% CI 58.6-100.5) and 45.8 (95% CI 42.0-49.6) excess cases per 10 000 scans for female children and adolescents, respectively. There was a substantially higher risk of breast cancer induction for children receiving thoracic spine CT compared with adolescents.

CONCLUSIONS

CT clearance of the thoracic spine in the pediatric trauma patient results in a high dose of radiation and an age-dependent increase in theoretical breast cancer induction.

Gonad shielding in paediatric pelvic radiography: disadvantages prevail over benefit

OBJECTIVE

To re-evaluate gonad shielding in paediatric pelvic radiography in terms of attainable radiation risk reduction and associated loss of diagnostic information.

METHODS

A study on patient dose and the quality of gonad shielding was performed retrospectively using 500 pelvic radiographs of children from 0 to 15 years old. In a subsequent study, 195 radiographs without gonad shielding were included. Patient doses and detriment adjusted risks for heritable disease and cancer were calculated with and without gonad shielding.

RESULTS

For girls, gonad shields were placed incorrectly in 91% of the radiographs; for boys, in 66%. Without gonad shielding, the hereditary detriment adjusted risk for girls ranged between 0.1 × 10(-6) and 1.3 × 10(-6) and for boys between 0.3 × 10(-6) and 3.9 × 10(-6), dependent on age. With shielding, the reduction in hereditary risk for girls was on average 6 ± 3% of the total risk of the radiograph, for boys 24 ± 6%. Without gonad shielding, the effective dose ranged from 0.008 to 0.098 mSv.

CONCLUSIONS

With modern optimised X-ray systems, the reduction of the detriment adjusted risk by gonad shielding is negligibly small. Given the potential consequences of loss of diagnostic information, of retakes, and of shielding of automatic exposure-control chambers, gonad shielding might better be discontinued.

Comparison of dose from radiological examination for scoliosis in children among two pediatric hospitals by Monte Carlo simulation

The radiation exposures of children undergoing full spine radiography were investigated in two pediatric hospitals in Greece. Entrance surface kerma (Ka,e) was assessed by thermoluminescence dosimetry and patient's effective dose (E) was estimated by Monte Carlo simulation. All required information regarding patient age and sex, the irradiation geometry, the x-ray spectra, and other exposure parameters (tube voltage and current) were registered as well. Values of Ka,e were measured to range from 0.22 mGy to 2.12 mGy, while E was estimated to range from 0.03 mSv to 0.47 mSv. In general, all values were greater in one of the two hospitals, as higher tube currents and exposure times were used in the examinations because of the difference in radiographers' training and practice. Moreover, dose to red bone marrow was found to be between 0.01 to 0.23 mSv and dose to breast ranged between 0.02 and 1.05 mSv depending on the age, projection, and hospital. These values are comparable with literature sources.

Paediatric x-ray examinations in Rio de Janeiro

This work presents the results of a dose survey performed for paediatric patients and carried out in two large paediatric public hospitals in Rio de Janeiro city. The entrance surface dose (ESD) and the effective dose (ED) were evaluated for chest, skull, abdomen, lumbar spine, cervical spine and pelvis in antero-posterior (AP), postero-anterior (PA) and lateral (LAT) projections. For each examination, four age groups 0-1, 1-5, 5-10 and 10-15 years were studied. The DoseCal software was used to calculate these doses. Wide variations for the same type of examination and projection have been detected. These variations were evident, in Brazil, from previous work. In spite of the present results being still preliminary, they can give an idea of what paediatric ESDs are like in Brazil. Also, with respect to the entrance surface dose, some of the results are above the reference levels, which cause high ED, as well. On the other hand, the wide range of ESD reflects the disparity of radiographic techniques and demonstrates that the ALARA principle is not being applied in Brazilian hospitals and becomes a concern in terms of public health.

Radiation dose and cancer risk to children undergoing skull radiography

BACKGROUND

Limited data exist in the literature concerning the patient-effective dose from paediatric skull radiography. No information has been provided regarding organ doses, patient dose during PA skull projection, risk of cancer induction and dose to comforters, i.e. individuals supporting children during exposure.

OBJECTIVE

To estimate patient-effective dose, organ doses, lifetime cancer mortality risk to children and radiation dose to comforters associated with skull radiography.

MATERIALS AND METHODS

Data were collected from 136 paediatric examinations, including AP, PA and lateral skull radiographs. Entrance-surface dose (ESD) and dose to comforters were measured using thermoluminescent dosimeters. Patients were divided into the following age groups: 0.5-2, 3-7, 8-12 and 13-18 years. The patient-effective dose and corresponding organ doses were calculated using data from the NRPB and Monte Carlo techniques. The risk for fatal cancer induction was assessed using appropriate risk coefficients.

RESULTS

For AP, PA and lateral skull radiography, effective dose ranges were 8.8-25.4, 8.2-27.3 and 8.4-22.7 microSv respectively, depending upon the age of the child. For each skull projection, the organs receiving doses above 10 microGy are presented. The number of fatal cancers was found to be less than or equal to 2 per 1 million children undergoing a skull radiograph. The mean radiation dose absorbed by the hands of comforters was 13.4 microGy.

CONCLUSIONS

The current study provides detailed tabular and graphical data on ESD, effective dose, organ doses and lifetime cancer mortality risk to children associated with AP, PA and lateral skull projections at all patient ages.

Avaliação dos padrões de dose em radiologia pediátrica

Neste trabalho avaliou-se o produto dose área e estimou-se a dose na entrada da pele em exames pediátricos, cujos resultados mostraram valores, em média, 100% acima do adotado como referência para a realização deste trabalho (0,070 mGy). Simultaneamente, fez-se a aferição dos parâmetros técnicos dos equipamentos usados para a obtenção das imagens radiográficas. Os resultados revelaram que o desempenho dos equipamentos está de acordo com a legislação sanitária vigente. Logo, as doses elevadas foram atribuídas ao emprego de técnicas de baixa tensão e à falta de especialização para a realização de exames pediátricos. Realizaram-se medidas das doses absorvidas na região gonadal durante as exposições radiográficas utilizando-se dosímetros termoluminescentes, que se mostraram inadequados para a obtenção destas medidas. Usou-se então uma câmara de ionização e os valores obtidos revelaram que as doses absorvidas sobre a região gonadal estão abaixo dos limites que poderiam causar esterilidade temporária ou permanente.

Diagnostic x rays, DNA repair genes and childhood acute lymphoblastic leukemia

A model for childhood leukemia proposes that characteristic chromosomal translocations can arise in utero and that for most cases a second hit occurring postnatally will be necessary. Possible causal mechanisms for leukemias are environmental factors such as ionizing radiation from x rays and inherited susceptibility from polymorphisms in DNA repair genes. We performed a case-control study of childhood acute lymphoblastic leukemia measuring reported postnatal x rays in 701 cases aged 0-14 y and in as many population-based controls matched on age and sex. In addition we performed a case-only study in 207 cases to evaluate the interaction between x ray exposure and polymorphisms in DNA repair genes. There was an increase in risk of leukemia with number of x rays: the adjusted odds ratio for two or more x rays vs. none was 1.48 (95% confidence interval: 1.11-1.97). That risk was slightly higher among girls (odds ratio = 1.67). A polymorphism in the APE gene (ex 5) involved in the base excision repair system was suggestive of an increased risk among boys and a reduced risk among girls. HMLH1 (ex 8), a mismatch repair gene, was associated with reduction of risk among girls. Results from the genetic data are still preliminary and must be interpreted with caution especially because of the relatively small number of genotyped cases. However, ionizing radiation from x rays as well as polymorphisms in DNA repair genes are plausible risk factors for childhood leukemia and should be studied more.

Investigation of dose reduction in neonatal radiography using specially designed phantoms and LiF:Mg,Cu,P TLDs

Many departments still do not use recommended radiographic parameters to X-ray neonates. Direct, accurate dose measurements of individual examinations may assist a department in justifying technique modifications that provide a substantial dose reduction without a significant loss of image quality. The aim of this study was to investigate dose reduction techniques for neonates in the intensive care unit. Alterations in beam energy (kVp and filtration) and collimation were investigated using specially designed phantoms mimicking a 700 g and 2000 g neonate, and ultrasensitive LiF:Mg,Cu,P thermoluminescence dosimeters (TLDs). Differences in entrance surface dose (ESD) and dose at depth (3 cm or 5 cm) were compared for two, overlapping fields centred individually on the chest and abdomen (Technique 1) and one large chest-abdomen field (Technique 2 or babygram). The large phantom was irradiated at 54 kVp, 60 kVp and 70 kVp without additional filtration and at 66 kVp and 70 kVp with a rare-earth hafnium filter. Focus-film distance (FFD) and mAs were adjusted to maintain optical density (OD) on each radiograph. The baseline dose at 54 kVp and 100 cm FFD was (46+/-2) micro Gy. Increasing the tube potential from 54 kVp to 70 kVp without additional filtration reduced the ESD by 27%. However, the addition of a 0.05 mm hafnium filter at 66 kVp further reduced the radiation dose by 13%, to produce an ESD of (28+/-2) micro Gy. All contrast details were observable at 66 kVp with hafnium filtration. Technique 1 may lead to an increase in effective dose due to field overlap, which diverges at depth, and increased scatter at the periphery of the fields.

Radiation dose considerations in common paediatric X-ray examinations

BACKGROUND

For paediatric radiology, diagnostic reference levels (DRLs) have been proposed by the National Radiological Protection Board and the European Commission, representing a baseline above which re-evaluation of the equipment and the techniques used is necessary.

OBJECTIVE

To measure the entrance surface dose (ESD) in various paediatric radiological examinations carried out at a large paediatric hospital in Greece and compare them with the existing DRLs.

MATERIALS AND METHODS

Measurements of ESD using thermoluminescent dosemeters were carried out in a sample of 168 paediatric patients who underwent various common radiological examinations (chest, skull, pelvis, lumbar spine, full spine). The patients were categorised according to age, and the mean ESD was calculated for each examination and age category. Additionally, the effective doses were estimated from measured ESD using appropriate conversion coefficients found in the literature.

RESULTS

The mean ESD values were found to be well below the proposed DRLs for all the examinations studied except for the chest, owing to the low tube potential used and tube filtration.

CONCLUSIONS

Even in examinations that did not exceed the DRL, patient protection can be optimised further by appropriate collimation of field size to that necessary for diagnosis.

A study of the application of paediatric reference levels

Radiation exposure of paediatrics is of particular concern because of the greater health detriment. In this study, the application of patient dose reference levels to paediatric radiographic examinations has been investigated. The relationships between entrance surface dose and patient age and size parameters have been studied in three hospitals. The data have been used to derive conversion factors to describe relationships between doses for children of different ages. The usefulness of equivalent patient diameter, weight and age as variables relating to doses has been examined. Simple conversion factors in look-up tables have been derived that link doses for patients of a variety of ages and sizes for particular examinations. It is proposed that factors of this type could be applied to data for individual patients to allow a wider range of ages to be included in any group. This would enable sufficient dose data to be collected from non-specialist hospitals for comparison with reference levels. It would facilitate identification of hospitals where doses are higher so that changes could be made to radiographic practice.

The risk of carcinogenesis from radiographs to pediatric orthopaedic patients

This study set out to determine whether cumulative radiograph exposure of children significantly increases their risk of radiation-induced carcinogenesis or hereditary defects. Records of children treated for idiopathic scoliosis, hip dysplasia, or leg-length discrepancy between 1980 and 1993 at the Shriners Hospital in Spokane, WA, were retrospectively reviewed. Total radiation and organ dose exposures were calculated using information from individual radiology reports. Surgically treated idiopathic scoliosis patients had the largest total radiation skin entrance and organ dose exposures. This group's risks for developing leukemia, breast cancer, or a heritable defect, respectively, were 0.8%, 2.1%, and 3.0% higher than baseline risks. The other treatment groups had increased carcinogenic risks of <1%. The use of serial radiographs during the treatment of idiopathic scoliosis, hip dysplasia, and leg-length discrepancy appears relatively safe. The increased risk of carcinogenesis or hereditary defects in these patients is minimal.

Radiation exposure to children during coil occlusion of the patent ductus arteriosus

The risks of excessive exposure to ionizing radiation are well described and measures are routinely taken to limit such exposure to both patient and personnel in the catheterization laboratory. Coll occlusion of the patent ductus arteriosus (PDA) as well as other more complex pediatric interventions has raised concern regarding radiation exposure, particularly as minimally invasive surgical techniques are being developed which lack such exposure risk. In eight consecutive patients, aged 0.7-7 years (median, 2.3 years), coil occlusion of a PDA was performed and surface entrance radiation dose determined by thermoluminescent dosimetry (TD). Total cumulative doses (PA + lateral dose) were also calculated for each patient. Entrance and cumulative dose was likewise measured in 12 patients undergoing standard diagnostic catheterization (DC) and in 5 consecutive patients undergoing pulmonary balloon valvuloplasty (PBV). The groups were comparable in age, weight, and body surface area (BSA). Total cumulative dose in the PDA patients was 97 +/- 25 mGy (mean +/- SE). There was no significant difference between the three groups in entrance dose absorbed at each location or in total cumulative dose. The mean total fluoroscopy time in the PDA occlusion group was significantly less than that of the PBV group (10.1 +/- 1.81 min vs. 19.3 +/- 2.29 min, P < 0.05) but was comparable to the DC group (13.2 +/- 1.5 min, P = NS). When the subjects were analyzed collectively, no correlation between fluoroscopy time and measured entrance dose was observed. The strongest correlates of total cumulative dose were patient weight (r = 0.67, P < 0.001) and BSA (r = 0.62, P = 0.001). Patients undergoing coil occlusion of a PDA are not exposed to increased radiation entrance dose compared to those undergoing standard DC and PBV. Furthermore, surface entrance radiation dose as determined by TD varies according to patient size for a given fluoroscopy time.

Radiation exposure in bone mineral density assessment

Osteoporosis is a systematic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue which leads to diminished biomechanical competence of the skeleton and low-trauma or atraumatic fractures. Due to increased awareness of the impact of osteoporosis on the elderly population, the use of bone densitometric techniques is becoming more widespread. Considerable progress has been made in the development of non-invasive methods for the assessment of the skeleton. While DXA and QCT are commonly used techniques, the popularity of other approaches such as RA, SXA and QUS is gaining grounds. QCT has an advantage over the other techniques in its ability to measure the true volumetric density of trabecular or cortical bone. We therefore present an overview of these current techniques for bone mineral density (BMD) measurements. In the second section we discuss the radiation doses incurred in BMD measurements by patients and methods for reducing patient and staff radiation exposure are given. Studies of radiation dose to patient from DXA confirms that patient dose is small (0.08-4.6 muSv) compared to that given by many other investigations involving ionizing radiation. Fan beam technology with increased resolution has resulted in increase patient dose radiation dose (6.7-31 muSv) but this is still relatively small. Carrying vertebral morphometry using DXA also incurs less radiation dose (< 60 muSv) than standard lateral radiographs QCT has radiation dose (25-360 muSv) comparable to simple radiological examination such as chest X-ray but lower than imaging CT. Radiation dose from other techniques such as RA and SXA are in the same order of magnitude as pencil beam DXA. For pencil beam DXA and SXA systems the time average dose to staff from scatter is very low even with the operator sitting as close as 1 m from the patient during measurement. However the scatter dose from fan beam DXA systems is considerable higher and approaches limits set by regulator bodies for occupational exposure.

Comparison of radiation dose from intravenous urography and 99Tcm DMSA scintigraphy in children

Intravenous urography (i.v.u.) and 99Tcm DMSA scintigraphy are possible alternative diagnostic techniques in paediatric renal investigation. Radiation dose comparisons between them have been complicated in the past by the lack of paediatric data. In this study, evaluations relevant to children are used to compare estimates of effective dose from the two techniques. For the radiographic procedures, standard operating parameters and representative age-dependent values of entrance surface dose were established from recent literature. Conversion factors relating effective dose to entrance surface dose and dose-area product are presented and used to obtain values of effective dose for single radiographs of abdomen, kidneys and pelvis. Suggested i.v.u. procedures consisting of four ("minimum") or eight ("average") radiographs were adopted to derive the effective dose for full i.v.u. examinations. 99Tcm DMSA dose estimates, taken from our published work using an administered activity schedule based on body surface area, are almost constant at about 1 mSv for all children. In comparison, mean i.v.u. doses based on the "average" number of radiographs are similar to DMSA doses for infants (< 1 year) but may be twice as high for older children. Although the differences between procedures at this level of dose do not in themselves provide grounds for preference, when coupled with the lower diagnostic sensitivity of i.v.u. they suggest limitations of this procedure for detection of a renal scar.

Digital radiography in paediatrics: radiation dose considerations and magnitude of possible dose reduction

The purpose of this study was to evaluate the radiation doses received by paediatric patients examined using a digital radiography unit, and to compare these doses with those received from conventional screen-film systems. In this way, guidelines could be drawn up concerning the magnitude of possible dose reductions achievable using digital radiography. The study was undertaken on approximately 900 patients undergoing abdomen, chest, pelvis and skull examinations. Patients were categorized into the following age groups: 0-1 month, 1-12 months, 1-5 years, 5-10 years and 10-15 years. Approximately half were X-rayed using a Fuji computed radiography system and half using a conventional screen-film system. Entrance surface dose was calculated from the recorded exposure parameters and measured X-ray tube outputs. Dose-area product was recorded directly. Image quality was assessed clinically using criteria recommended by a working group of the Commission of the European Communities. Apart from chest examinations, it was found possible to reduce doses by about 40% on average, by using a computed radiography system instead of a 600 speed screen-film combination. There was no significant difference in the dose for chest examinations. Satisfactory image quality can therefore be achieved by using computed radiography as a 1000 speed system for abdomen, pelvis and skull examinations, and as a 600 speed system for chests. Since very few departments appear to use screen-film systems of speeds greater than 400, then, for most departments, the use of computed radiography would result in dose reductions of at least 60%, or 33% for chests.

Radiation dose and in vitro precision in paediatric bone mineral density measurement using dual X-ray absorptiometry

Dual X-ray absorptiometry (DXA) is one of the most widely used techniques for non-invasive assessment of bone integrity. There is a growing demand for measurement of paediatric bone status. In DXA the principal radiation risks to patients are the carcinogenic and genetic effects. Radiation dosimetry is well established for DXA in adults, but there are limited paediatric data available. We report on a study to estimate the effective doses (EDs) received by typical 5- and 10-year-old children using the paediatric scan mode on the Lunar DPX-L bone mineral density scanner. Entrance surface doses (ESDs) and percentage depth doses for the total body and PA spine scan modes were measured using lithium borate thermoluminescent dosemeters (TLDs) located at the surface and distributed at various organ locations in anthropomorphic child phantoms. The EDs were calculated from the percentage depth doses, amount of each organ irradiated and tissue weighting factors. The ESDs were measured to be 6.0 and 0.12 microGy for the posteroanterior (PA) spine and total body, respectively. PA spine EDs were calculated as 0.28 and 0.20 microSv for the 5- and 10-year-old, respectively. Total body EDs were 0.03 and 0.02 microSv for the 5- and 10-year-old children, respectively. These results compare with an adult ED of 0.21 microSv for the PA spine. They are also more than two orders of magnitude lower than reported ESDs and EDs for paediatric chest X-rays. Bone mineral density (BMD) short-term in vitro precision was 0.5% and 1% in the 5- and 10-year-old phantoms, respectively. In conclusion, the Lunar DPX-L in the paediatric mode has a high precision and very low radiation doses, similar to those reported for the adult mode.

Examination technique, image quality, and patient dose in paediatric radiology. A survey including 19 Swedish hospitals

PURPOSE

Investigation of examination technique, image quality, and absorbed dose to the patients in paediatric radiology.

MATERIAL AND METHODS

In total, 19 Swedish hospitals participated in the study. Using a questionnaire, the hospitals described their examination technique for the pelvis, urinary tract, colon, scoliosis, and lung. The image quality and patient dose were experimentally studied for the simulated pelvis examination of a 1-year-old child. This examination was carried out with a test object containing a contrast-detail phantom. TL dosimeters were used to determine the absorbed dose on the surface of the phantom, approximately corresponding to the absorbed dose on the surface of the patient.

RESULTS

Examination techniques varied considerably among the hospitals, the most striking difference concerning the film-screen sensitivity. Consequently, there was a variation in the absorbed dose on the surface of the phantom, from 0.09 mGy to 1.7 mGy (mean 0.65 mGy). For a large range of doses, 0.4-1.7 mGy, the image quality was not significantly different.

CONCLUSION

The unharmonized, and in many places unoptimized, examination techniques led to a great variation in the absorbed dose to the children examined.

Dose-area product measurements in paediatric radiography

The dose-area product (DAP) could provide a useful quantity for monitoring doses for paediatric radiography, because it is a sensitive parameter, which is simple to record. A study of DAP measurements has been carried out for single radiographic projections for paediatric patients and comparisons made with measurements of entrance dose. The technique has been used to investigate doses for examinations performed with and without a grid. There is a linear relationship between DAP and entrance dose, with a variation of +/- 20% for pelvis, abdomen, spine and skull radiographs, but data for chests are more scattered. Logarithm of the DAP is linearly related to an equivalent patient diameter and reference levels could be set in terms of DAP either by patient age range or size. Effective doses determined from DAPs were 0.1-0.3 mSv for abdomen, pelvis and spine anteroposterior radiographs for 5-15 year olds, and less than 0.03 mSv for 0 and 1 year olds. Doses for examinations performed without a grid were only 20% of those for which a grid was used in the X-ray room studied. Significant reductions in doses for paediatric radiology can be achieved, where the use of grids can be avoided.

Dose distribution at radiographic examination of the spine in pediatric radiology

STUDY DESIGN

The radiation dose distribution at radiographic examinations of the lumbar spine and the thoracic spine and at examinations for scoliosis has been investigated in pediatric patients.

OBJECTIVES

To derive the conversion factors between the entrance surface dose and the mean absorbed dose to the most radiation-sensitive organs, and to determine the dose level and its variation for patients.

SUMMARY OF BACKGROUND DATA

Fifty-five patients participated in the survey. Mathematically describable phantoms were used to simulate the body of children of various ages.

METHODS

Relative absorbed dose in the body was determined with measurements. The entrance surface dose and the dose-area product were measured for a number of patients. The effective dose and its variation between patients were estimated.

RESULTS

The mean entrance surface doses were highest for the lumbar spine examinations (2.6 mGy, anteroposterior projection; 6.7 mGy, lateral projection). The female gonads received the highest dose. The mean entrance surface doses for the thoracic spine examinations were 2.1 mGy for the frontal view and 6.1 mGy for the lateral view. The breasts, thyroid, lungs, and esophagus received the highest absorbed dose. Mean effective dose for one frontal and one lateral view was slightly higher for lumbar spine examinations than for thoracic spine examinations. An optimized scoliosis examination gives a much lower effective dose, about 0.05 mSv (frontal view). If an additional exposure determining the "skeletal age" is performed, the effective dose rises with 0.12 mSv.

CONCLUSIONS

Thoracic spine and lumbar spine examinations lead to relatively high-absorbed doses to radiation-sensitive organs. Because the scoliosis investigation is repeated several times, the total effective dose could be considerable.

Dose-area product values in frequently performed complex paediatric radiology examinations

Mean values of the dose-area product for barium meal, micturating cystourethrography and intravenous urography examinations from three health centres and for four age groups are presented in this study. Values measured are between 13% and 86% higher than results previously reported, which justifies the importance of applying procedures which reduce risks to patients.

The radiation dose to children from X-ray examinations of the pelvis and the urinary tract

X-ray examinations of the pelvis and the urinary tract are frequent examinations of children, in which a large part of the trunk is irradiated. The irradiated volume contains many of the most radiation sensitive organs and tissues. The absorbed dose to children during the examination was estimated from measurements with a dose-area product meter and thermoluminescent dosemeters (TLDs). Entrance surface dose and the dose-area product results are presented. Conversion factors between the entrance surface dose and the organ dose were derived. The energy imparted, organ dose and effective dose were determined. The entrance surface dose for one single exposure varied between 0.32 mGy and 8.6 mGy for the urinary tract examination and between 0.26 mGy and 2.89 mGy per exposure for the pelvis examination. These variations are mainly influenced by the body size of the patient. The number of images taken during one examination varied. For the urinary tract investigation, the average number of exposures was six, while the corresponding number for the pelvis examination was two. The average effective dose for a typical urinary tract investigation ranged from 0.9 mSv to 8.5 mSv and from 0.3 mSv to 1.4 mSv for the pelvis examination. The radiation dose depends greatly on the body size. The recommendations to present the results in relation to age have been followed; however, the variation of body size even within each specified age range is significant. It is suggested that doses should be quoted in relation to a more critical parameter than age.

Radiation doses to paediatric patients undergoing micturating cystourethrography examinations and potential reduction by radiation protection optimization

Dose-area product values were measured in paediatric micturating cystourethrography examinations in two dedicated facilities. The results are compared, taking into account features of the X-ray rooms and differences in examination protocol. Several optimization procedures were simulated or implemented, in order to estimate the dose savings which could be attained. Potential savings identified in the dose-area values reach about 85% for both centres.

A study of the relationship between patient dose and size in paediatric radiology

Entrance doses and dose-area products have been measured for paediatric X-ray examinations in a dedicated paediatric department. Dose-area products for barium meal and micturating cystourethrogram examinations involving fluoroscopy were substantially less than results from other studies. A number of factors contribute to this, including a high gain image intensifier used without a grid, shorter screening times, smaller numbers of films, exclusive use of a 100 mm camera and careful collimation of the X-ray field. Entrance air kerma has been measured for pelvis, abdomen, chest and skull radiographs. The relationship between dosimetric quantities and an equivalent patient diameter derived from data on patient height and weight has been studied. The results show a linear relationship between the logarithm of entrance air kerma and equivalent patient diameter for radiographic examinations performed on a single X-ray unit. Application of exponential correction factors could allow entrance doses for radiographs of children of different ages to be compared with appropriate reference doses.

Patient exposure to ionising radiation in the intensive care unit due to portable chest radiography

The chest X-ray is the most commonly performed radiological examination in the intensive care unit. We used TLDs to measure the radiation exposure in 30 ICU patients due to portable chest radiography. The mean number of CXR was 3 (range 1-11). The mean surface entry dose at the xiphisternum was 1.8 mGy (range 0.43-5.14 mGy) per patient and 0.63 mGy per CXR. Very small amounts of radiation were detected at the symphysis pubis and in more than half of the patients no radiation was detected at this site. These values are well above accepted norms. Patient exposure may be reduced by ordering fewer X-rays or by changing to a faster screen-film combination.

Evolution of diagnostic radiology in a big hospital during a 5 year period, and the derived collective dose

An analysis is presented of the trends in the annual number of radiological examinations and in the average effective dose equivalent for each type of examination in a big Spanish hospital. Annual frequencies for each type of examination, annual average effective dose equivalent values for each study group, and the contribution of each examination group to the collective dose are presented. Also, sex and age distributions for several important examinations are given, and their impact on the collective dose is reviewed.