Dose-area product measurements in paediatric radiography

Radiation exposure and estimated risk of radiation-induced cancer from thoracic and abdominal radiographs in 1307 neonates

OBJECTIVE

This study examined radiation exposure and the possible risk of radiation-induced cancer in a large sample of newborn and premature patients.

MATERIAL AND METHODS

In this retrospective study, we included all hospitalised neonates treated at our university hospital who received at least one X-ray examination from 1 January 2013 to 31 December 2018. We evaluated the dose area product (DAP), effective dose (ED), and estimated risk. The International Commission on Radiological Protection Publication 60 defines values (2.8-13 × 10-2 Sv-1) to calculate the estimated risk in relation to the ED.

RESULTS

Of the 3843 patients (aged 241.1 ± 35.45 days) treated in the neonatal care unit, 1307 (34%) received at least one X-ray. The mean number of X-ray examinations per patient was 3.19 and correlated negatively with birth weight. The mean cumulative DAP was 5.9 mGy*cm2, and the cumulative ED was 23.7 µSv per hospital stay. Patients with a birth weight of < 1000 g showed the highest cumulative ED and DAP (p < 0.001). Patients with a birth weight of < 2500 g had the highest ED and DAP per image (p < 0.001). The highest radiation exposure (ED/DAP) occurred for thoracic/abdominal examinations, especially for neonates < 500 g (p < 0.001).

CONCLUSION

There is a strong correlation between immaturity, the number of X-ray examinations, and radiation exposure. The total exposure was minimal, and the number of X-rays per patient has been decreasing in recent years.

CLINICAL RELEVANCE

Possible risks to newborns and premature infants caused by ionising X-rays are often the subject of scientific and clinical discussion. Nevertheless, conventional X-ray imaging remains a frequently used tool, and total exposure remains at a very low level.

KEY POINTS

The number of X-rays per patient has been decreasing in a large university hospital. Half of all patients received only one X-ray; most had a birth weight over 1500 g. This radiation risk can be classified as 'minimal' for patients with a birth weight of < 500 g and as 'negligible' for others.

Age-specific Dose Catalog for Diagnostic Fluoroscopy and Fluoroscopically Guided Interventional Procedures from a Pediatric Hospital

Background Fluoroscopy is an imaging modality associated with a wide range of dose levels, characterized using a variety of dose metrics, including effective dose. However, for clinical procedures, effective dose is a seldom-used and unregulated metric in the United States, and thus, it is not extensively studied in radiology despite potentially large clinical implications for patients, especially children and infants. Purpose To formulate and report a dose catalog across all diagnostic and interventional radiology (IR) fluoroscopy examination or procedure types at a specialized tertiary care pediatric hospital. Materials and Methods In this retrospective study, dose metrics taken from radiation dose structured reports of fluoroscopy between October 2014 and March 2023 were analyzed. The reports included fluoroscopy across 18 diagnostic examination types and 24 IR procedure types. The National Cancer Institute dosimetry system for Radiography and Fluoroscopy Monte Carlo software was used to estimate age-specific effective dose from dose-area product (DAP). The DAP-to-effective dose conversion factors were estimated per IR procedure type and diagnostic fluoroscopy examination type based on age. Results A total of 11 536 individual diagnostic fluoroscopy examinations (18 types) and 8017 individual IR procedures (24 types) were analyzed. Median effective dose values per diagnostic fluoroscopy examination type ranged from 0.0010 to 0.44 mSv (mean, 0.0808 mSv ± 0.0998 [SD]). Calculated DAP-to-effective dose conversion factors ranged from 0.04 to 2.48 mSv/Gy · cm2 (mean, 0.758 mSv/Gy · cm2 ± 0.614) across all diagnostic fluoroscopy examination types. Median effective dose values per IR procedure type ranged from 0.0007 to 3.90 mSv (mean, 0.6757 mSv ± 0.8989). Calculated DAP-to-effective dose conversion factors ranged from 0.001 to 0.87 mSv/Gy · cm2 (mean, 0.210 mSv/Gy · cm2 ± 0.235) across all IR procedure types. Conclusion A pediatric fluoroscopy dose catalog was created, including age-specific effective dose, using a repeatable robust method based on accurate clinical data. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Borrego and Balter in this issue.

Sonography of Magnetically Controlled Growing Rods: A Quality Initiative in the Creation of a Multidisciplinary Clinic

Objective:

The MAGEC (Magnetic Expansion Control) rods were introduced to a medical institution in 2015. The rod expansion procedures were initially evaluated with radiographs. The staff undertook a quality initiative to reduce radiation exposure by utilizing sonography.

Material and Methods:

The radiation dose for a typical visit was measured by examining DICOM imaging data, stored in PACS. Imaging visit time was determined from the difference between times of first radiograph/sonogram before distraction to last radiograph/sonogram after distraction.

Results:

The 21 patients (8 male, 13 female) were an average age of 11.4 ± 2.82 years (age at implant = 7.5 ± 1.94) when evaluated. The average length of time for a radiographic visit was 40.7 ± 20.7 minutes, whereas a sonography visit was 10.7 ± 3.7 minutes. Radiation dose per study visit prior to the introduction of the MAGEC clinic was 0.42 ± 0.39 mSv. Given an ideal patient schedule, the MAGEC clinic could reduce radiation dose by 1.3 to 2.5 mSv annually, with 95% confidence.

Conclusion:

This quality improvement study demonstrated a reduction in radiation exposure and imaging time. The added benefits were providing a successful multidisciplinary imaging clinic and creation of a new exam that aligned with the “ultrasound first” initiative.

Paediatric radiation dose measurements undergoing X-ray examination in Tasmania

A pilot study was carried out involving six radiology centres across the state of Tasmania, Australia, with two main goals. First, to compare the choice of exposure factors used by each centre for four common paediatric projections of a 'standard' infant, 5-, 10- and 15-year-old patients. Second, to measure dose area product (DAP) at each radiology centre using the factors obtained and compare it against published diagnostic reference levels (DRLs). Significant variation was observed between the six radiology centres studied which has been attributed to the variability in exposure factors provided by the centres. Notably, the measured DAP values in the case of infant and 5-year-old patients were observed to be significantly lower than the published reference DAP DRLs. While significantly higher exposure factors have been observed for 15-year-old patients as illustrated in measured DAP values.

Diagnostic radiation exposure in children with spinal dysraphism: an estimation of the cumulative effective dose in a cohort of 135 children from The Netherlands

OBJECTIVE

Based on the assumption that children with spinal dysraphism are exposed to a large amount of ionising radiation for diagnostic purposes, our objective was to estimate this exposure, expressed in cumulative effective dose.

DESIGN

Retrospective cohort study.

SETTINGS

The Netherlands.

PATIENTS

135 patients with spinal dysraphism and under 18 years of age treated at our institution between 1991 and 2010.

RESULTS

A total of 5874 radiological procedures were assessed of which 2916 (49.6%) involved ionising radiation. Mean cumulative effective dose of a child with spinal dysraphism during childhood was 23 mSv, while the individual cumulative effective dose ranged from 0.1 to 103 mSv. Although direct radiography accounted for 81.7% of examinations, the largest contributors to the cumulative effective dose were fluoroscopic examinations (40.4% of total cumulative effective dose).

CONCLUSIONS

Exposure to ionising radiation and associated cancer risk were lower than expected. Nevertheless, the use of ionising radiation should always be justified and the medical benefits should outweigh the risk of health detriment, especially in children.

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.

Measurement of entrance skin dose and estimation of organ dose during pediatric chest radiography

Entrance skin dose (ESD) was measured to calculate the organ doses from the anteroposterior (AP) and posteroanterior (PA) chest x-ray projections for pediatric patients in an Indian hospital. High sensitivity tissue-equivalent thermoluminescent dosimeters (TLD, LiF: Mg, Cu, P chips) were used for measuring entrance skin dose. The respective organ doses were calculated using the Monte Carlo method (MCNP 3.1) to simulate the examination set-up and a three-dimensional mathematical phantom for representing an average 5-y-old Indian child. Using this method, conversion coefficients were derived for translating the measured ESD to organ doses. The average measured ESDs for the chest AP and PA projections were 0.305 mGy and 0.171 mGy, respectively. The average calculated organ doses in the AP and the PA projections were 0.196 and 0.086 mSv for the thyroid, 0.167 and 0.045 mSv for the trachea, 0.078 and 0.043 mSv for the lungs, 0.110 and 0.013 mSv for the liver, 0.002 and 0.016 mSv for the bone marrow, 0.024 and 0.002 mSv for the kidneys, and 0.109 and 0.023 mSv for the heart, respectively. The ESD and organ doses can be reduced significantly with the proper radiological technique. According to these results, the chest PA projection should be preferred over the AP projection in pediatric patients. The estimated organ doses for the chest AP and PA projections can be used for the estimation of the associated risk.

Assessment of dosimetric quantities for patients undergoing X-ray examinations in a large public hospital in Brazil--a preliminary study

The introduction of routine patient dosimetry to Brazilian radiological institutions is very necessary in order to meet national and international standard requirements for radiation protection. This work presents a survey of the air kerma-area product (P(KA)), the entrance surface air kerma (K(e)) and the effective dose (E) in common radiographic examinations during the routine of a large public hospital in the city of Belo Horizonte, Brazil. Results draw attention to the use of field sizes larger than the cassette dimension, the lack of both the collimation X-ray beam and the standardisation of the exposure parameters by radiology technicians.

Patient dosimetry in paediatric diagnostic radiology

A study of patient exposure in paediatric diagnostic radiology was conducted in three dedicated paediatric departments. The entrance surface dose was assessed by three methods: direct measurement by thermoluminescent dosemeters, calculation from the dose-area product and from the tube output. The results obtained by the these methods were compared, proving that all of them are applicable for the assessment of paediatric doses. Subsequently, the accumulated data were compared with the mean values from other similar studies and to the reference dose levels set by the Commission of European Communities, which clearly demonstrated the need for further investigation of the paediatric dose levels in Bulgaria and for optimisation of the radiological practice.

Diagnostic reference levels for thorax X-ray examinations of paediatric patients

Based on the Medical Exposure Directive of the European Commission, 97/43/Euratom, The Radiation and Nuclear Safety Authority (STUK) in Finland has the responsibility for setting national diagnostic reference levels (DRLs) for the most common radiological examinations. Paediatric patients deserve special attention because of the higher radiation risk compared with adults. The purpose of this paper is to present a method that takes into account patient size when setting DRLs in paediatric patients. The overall data consisted of patient doses collected from six hospitals during the years 1994-2001, and new measurements in two hospitals in 2004. In total, there were 700 chest examinations. The method established by the National Radiological Protection Board (UK) for setting DRLs was not considered feasible in Finnish practice. Patient doses correlated exponentially with the projection thickness, which was measured directly for each patient. Since 1 January 2006, paediatric DRLs for conventional chest examinations have been specified in Finland as a DRL curve by using both dose quantities (entrance surface doses (ESD) and dose-area product (DAP)) as a function of patient projection thickness.

Optimisation in general radiography

Radiography using film has been an established method for imaging the internal organs of the body for over 100 years. Surveys carried out during the 1980s identified a wide range in patient doses showing that there was scope for dosage reduction in many hospitals. This paper discusses factors that need to be considered in optimising the performance of radiographic equipment. The most important factor is choice of the screen/film combination, and the preparation of automatic exposure control devices to suit its characteristics. Tube potential determines the photon energies in the X-ray beam, with the selection involving a compromise between image contrast and the dose to the patient. Allied to this is the choice of anti-scatter grid, as a high grid ratio effectively removes the larger component of scatter when using higher tube potentials. However, a high grid ratio attenuates the X-ray beam more heavily. Decisions about grids and use of low attenuation components are particularly important for paediatric radiography, which uses lower energy X-ray beams. Another factor which can reduce patient dose is the use of copper filtration to remove more low-energy X-rays. Regular surveys of patient dose and comparisons with diagnostic reference levels that provide a guide representing good practice enable units for which doses are higher to be identified. Causes can then be investigated and changes implemented to address any shortfalls. Application of these methods has led to a gradual reduction in doses in many countries.

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.

Mesure pratique de l’irradiation en radiopédiatrie : utilisation du produit dose surface en fluorographie numérique et pour les radiographies pulmonaires néonatales

PURPOSE

Control of radiation dose in pediatric radiology requires knowledge of the reference levels for all examinations. These data are useful for daily quality assessment, but are not perfectly known for some radiographic examinations. The purpose of our study was to evaluate the dose related to voiding cystourethrograms (VCUG), upper GI (UGI) and intravenous urography (IVU). Neonatal chest radiographs in the intensive care unit were also evaluated.

MATERIAL AND METHODS

For examinations with contrast material (478VCUG, 220UGI, 80IVU), the children were divided in groups based on their weight, from 5 to 30 Kg. Measurements were performed using an ionization chamber and expressed with the dose-area product (DAP). For chest radiographs, a direct measurement of the entrance-skin dose was performed, with secondary calculation of the DAP.

RESULTS

For VCUGs, the DAP ranged between 42.89cGy.cm2 and 125.41cGy.cm2. The range was between 76.43 and 150.62cGy.cm2 for UGIs and between 49.06 and 83.33cGy.cm2 for IVUs. For neonate chest radiographs, DAP calculations were between 0.29 and 0.99cGy.cm2.

CONCLUSION

These values represent our reference doses. They allow continuous monitoring of our radiographic technical parameters and radiographic equipment and help to correct and improve them if necessary.

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.

Neonatal chest and abdominal radiation dosimetry: a comparison of two radiographic techniques

Radiographs of the chest and the abdomen are the most commonly requested diagnostic X-ray examinations undertaken in neonatal intensive care units. Frequently, for a single child, both radiographs are requested simultaneously. These images can be obtained either as two separate exposures (one of the chest and one of the abdomen), or as a single exposure to include both anatomical regions on one film. This study compared the effective dose imparted as a result of each technique. A neonatal anthropomorphic phantom was designed and constructed, and each radiographic technique was simulated. Entrance surface dose (ESD) and dose-area product (DAP) were measured and estimates of effective dose were made from the DAP values. The mean effective dose for the separate exposure technique was estimated to be 37.3 microSv compared with 35.5 microSv for the combined exposure technique. However, observed variations in field size gave rise to uncertainties in DAP and thus the effective doses estimated from it. Hence, no significant difference in effective dose was observed between the radiographic techniques. The observed coefficient of variation in field size (16% for a 2.5 kg neonate) demonstrates that good standards of radiographic practice are more important than choice of technique.

Effective dose at pneumatic reduction of paediatric intussusception

AIM

The purpose of this study was to assess screening times and resulting dose implication at pneumatic reduction of intussusception in the paediatric age group and to examine the relationship with the outcome of the procedure.

MATERIALS AND METHODS

We retrospectively reviewed the case notes and departmental records of 143 children who had undergone a total of 153 pneumatic reductions in our department over a 4-year period. Success rates, screening times and available dose-area products (DAP) were recorded. The DAPs were converted to effective dose (ED) for 77 procedures.

RESULTS

A 76.5% (117/153) success rate was achieved with a recurrence rate of 6.5% and only one complication: a perforation. Screening times were recorded in 137 reductions and ranged from 15 s to 22.6 min. Although the longest screening time was associated with an unsuccessful outcome, the second longest time of 21 min was successful. This gave a DAP of 1278 cGy cm(2)and an ED of 12.73 mSv, which is equivalent to approximately 400 abdominal films for a 1-year-old. A lifetime risk of fatal cancer of one in 1000 was achieved, assuming the worst case, after a screening time of 30 min on our conventional fluoroscopy unit.

CONCLUSION

Our success rate compares well with other centres. Our institution is a tertiary referral centre and the occasional long screening time may reflect the delay and complex nature of the patients referred. Persistence at air reduction may be successful and the success rate increases with delayed attempts but the risks of the increasing radiation burden must be weighed against the risks of emergency surgery and anaesthesia.Heenan, S. D. (2000). Clinical Radiology 55, 811-816.

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.

Estimating the effective dose to children undergoing heart investigations--a phantom study

The aim of the investigation was to assess the conversion factor (F) for derivation of effective dose from measured dose-area product (DAP) during radiological examination of congenital heart diseases. Two anthropomorphic phantoms corresponding to a 1-year-old and a 5-year-old child were irradiated at several projections to imitate irradiation conditions at heart examinations. Organ doses were measured using thermoluminescent dosimeters for calculation of mean organ doses and effective dose according to ICRP. DAP values were measured simultaneously. The conversion factor (F) was calculated from the ratio of effective dose (mSv) to DAP value (Gy cm2). The conversion factor (F) correlated strongly to the size of the phantom but less to the irradiation projection. However, at major beam angulation and at lateral projection F deviated note-worthily from that obtained at true or slightly angulated frontal views. Effective dose can therefore be estimated from the DAP values at heart investigation using two different F values. The following values are recommended for PA and lateral view respectively: for children weighing 7-11 kg, 1.8 and 1.4; for children weighing 15-26 kg 0.9 and 0.7.

Balancing patient dose and image quality

The formation of images in diagnostic radiology involves a complex interdependence of many factors. The ideal balance is to obtain an image which is adequate for the clinical purpose with the minimum radiation dose. Factors which affect radiation dose and image quality can be grouped under three headings; radiation quality, photon fluence and removal of scattered radiation. If optimal performance is to be achieved, it is necessary to understand how these factors influence image formation and affect radiation dose, and apply methodology for image quality and dose analysis at each stage in the development and use of X-ray equipment.

Dose reduction in a paediatric X-ray department following optimization of radiographic technique

A survey of radiation doses to children from diagnostic radiography has been carried out in a dedicated paediatric X-ray room. Entrance surface dose (ESD) and dose-area product (DAP) per radiograph were simultaneously measured with thermoluminescent dosemeters (TLDs) and a DAP meter to provide mean dose values for separate age ranges. Results of ESD and DAP were lower than the mean values from other UK studies for all ages and radiographs, except for the infant pelvis AP radiograph. Comparison of ESD and radiographic technique with CEC quality criteria highlighted a need for reduction of dose to infants and implied an increase in tube filtration might overcome the limitations of the room's three-phase, 12-pulse generator, allowing higher tube potentials to be used on infants. Additional tube filtration of 3 mmA1 was installed following assessment of dose reduction and image quality with test objects and phantoms, and confirmation from the paediatric radiologist that clinical image quality was not-significantly altered. The tube potential was increased from 50 to 56 kVp for the infant pelvis AP radiograph. The resulting ESD and effective dose fell by 51% and 38%, respectively. The CEC quality criteria have proved useful as a benchmark against which technique in X-ray departments can be compared, and as such are a useful tool for optimizing radiographic technique and reducing patient dose.

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.

Optimization and deconvolution of lithium fluoride TLD-100 in diagnostic radiology

Lithium fluoride (LiF) TLD-100 is one of the most commonly used thermoluminescent (TL) materials for the measurement of entrance surface dose (ESD) in diagnostic radiology. However, the minimum detectable dose (MDD) achieved, as derived from measurements of the random uncertainty present in the background signal, is usually quoted as being 50-100 microGy. A more appropriate definition of MDD for use in the clinical setting is the dose at which measurements exhibit a specified level of random uncertainty. This definition will give rise to a higher value for the MDD. An MDD of 50-100 microGy precludes accurate measurement of ESD in high tube potential (kVp) chest or neonatal radiography. Techniques described in the specialist literature for the reduction of the MDD of LiF were assessed both in the laboratory, and during a patient dose survey of high kVp chest radiography. Optimization of the pre-irradiation annealing and post-irradiation TL read heating cycles in terms of sensitivity and precision resulted in an MDD of 5/80 microGy (derived from background signal variation and 20% random uncertainty at 95% confidence limits, respectively). Deconvolution of the glowcurve was found to result in an MDD of approximately 10 microGy. Clinical measurements were contrasted with calculated values derived from ionization chamber measurements of tube output. The results support the hypothesis that glowcurve deconvolution permits the measurement of ESDs from low dose examinations using basic TL dosimetry equipment available to virtually all medical physics departments.