Key factors in the optimization of paediatric X-ray practice

STATUS OF RADIATION DOSE LEVELS IN PAEDIATRIC CHEST RADIOGRAPHY IN A TERTIARY HOSPITAL IN GHANA

Determination of appropriate radiation doses to paediatric patients in accordance with the as low as reasonably achievable (ALARA) principle is important, as it allows for effective optimization of imaging techniques. This study assessed the status of radiation dose levels in paediatric patients undergoing chest X-ray examinations at a tertiary hospital in Ghana. A population encompassing 86 paediatric patients categorised as infants (<1 y), young children (1-5 y) and older children (6-12 y) was selected using a quasi-experimental study design. The patients' anatomical data and X-ray beam exposure parameters were used to indirectly calculate the entrance surface doses (ESDs) received during the examinations. The infants received the highest mean ESD of 196 μGy (uncertainty = 0.37) compared to 158 μGy (uncertainty = 0.46) among the older children. The risk of developing radiation-induced biological effects was therefore higher for infant patients. The ESDs were generally higher than the internationally recommended reference doses. Careful adoption of internationally accepted exposure factors (high tube voltage and low tube load) is most recommended to optimise the dose.

Chest X-rays of newborns in a medical facility: variation between the entrance skin dose measurements using the indirect and direct methods for clinical dose audit

PURPOSE

This study aims to determine the mean and 75th percentile entrance skin dose (ESD_cal) from anteroposterior (AP) chest X-rays using machine parameters (indirect method). Also, a comparison was made between the ESD_cal and already determined thermoluminescent dosimeter (TLD) measurements (ESD_TLD) from a previous study from the same patients' data. In addition, the results were compared to similar articles, where the direct and indirect methods were used in estimating ESD to newborns.

MATERIALS AND METHODS

The study determined the digital radiography (DR) X-ray machine output using a calibrated XR Multidetector (silicon photodiode). X-ray machine milliampere-seconds (mAs), peak kilovoltage (kVp), focus to detector distance (FDD) and focus to skin distance (FSD) were used from a previous study. The mean kVp and mAs were 56.63 (52-60) and 5.7 (5-6.3) and the patient thickness was 9.5 (8-11.5) cm.

RESULTS

The mean ESDs of the newborn between 0 and 28 days were 0.67 ± 0.09 mGy, and the 75th percentile was 0.75 mGy. The effective dose (E) for the 40 patients was 0.19 mSv and the estimated prenatal cancer risk ranged from (5-24.7) 10^-6 Sv^-1. The variation between the indirect and the direct methods for assessing ESD was 39.6 (33.7-45.1)%.

CONCLUSION

The 75th percentile ESD was the highest compared to the American College of Radiology-American Association of Physicists in Medicine-Society for Pediatric Radiology (ACR-AAPM-SPR), European Commission (EC) and United Kingdom (UK) reports. Comparison of both methods for assessing ESD was within 40% as compared to other studies. Based on the above results, the indirect method can be implemented for clinical dose audit.

Optimization of dose and image quality in pediatrics chest digital radiography

INTRODUCTION

In this study, pediatric chest digital radiography (DR) is evaluated in response to the high volume of chest DR examinations and high radiosensitivity of children and young adults. The aim of the study is to optimize irradiation parameters in chest DR to have dose as low as reasonably achievable (ALARA) and simultaneously obtain improved or preserved image quality.

MATERIALS AND METHODS

Homogeneous phantoms in terms of density, dimensions, and composition were constructed to produce equivalent chest phantoms with less than 5% error for the 5-10 and 10-15-year-old age groups. The modulation transfer function (MTF), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured for both the reference and new conditions for the two age groups.

RESULTS

The results indicate that for the 5-10 year old age group, the optimized technique was 75 kVp and 6.3 mAs, in which the dose reduced 10% and the SNR and CNR increased by 0.4% and 6%, respectively, compared to the reference condition. For the 10-15-year-old age group, the 85 kVp and 5 mAs was close to the optimum condition, in which the dose reduced 37% and the SNR and CNR increased by 16% and 4%, respectively, compared to the reference condition.

CONCLUSION

The introduced optimized conditions in this study are accompanied by lower dose and higher SNR and CNR; therefore, they can be proposed as guides for optimization in clinical practice for pediatric chest digital radiography.

Inter-rater reliability in quality assurance (QA) of pediatric chest X-rays

PURPOSE

The goal of the study is to determine the inter-rater agreement on multiple factors that were utilized to evaluate the quality of pediatric chest X-ray exams from different levels of healthcare provision in an African setting.

METHODS

The image quality of pediatric chest X-rays from 3 South African medical centers of varying level of healthcare service were retrospectively assessed by 3 raters for 12 quality factors including: (1) absent body parts; (2) under inspiration; (3) patient rotation; (4) scapula in the way; (5) patient kyphosis/lordosis; (6) artefact/foreign body; (7) central vessel visualization; (8) peripheral vessels visualization; (9) poor collimation; and (10) trachea and bronchi visualization; (11) post-cardiac vessel visualization; and (12) absent or wrong image orientation. Analysis was performed using the Brennan--Prediger coefficient of agreement for inter-rater reliability and Cochran's Q statistic and McNemar's test for inter-rater bias.

RESULTS

1077 X-rays were reviewed. The least difference between observers in the frequency of the errors was noticed for factors (1) absent body parts and (12) absent or wrong image orientation with almost perfect agreement between raters. κ score for these two factors among all raters and between each pair of raters was more than 0.95 with no significant inter-rater bias. Conversely, there was poor agreement for the remaining factors with the least agreed on being factor (3) patient rotation with a κ score of 0.23. This was followed by factors (2) under inspiration (κ score of 0.32) and factors (4) scapula in the way (κ score of 0.35) respectively. There was significant inter-rater bias for all these three factors.

CONCLUSION

Many of the factors used to assess the quality of a chest X-ray in children demonstrate poor reliability despite mitigation against variations in training, standard quality definitions and level of healthcare service provision. New definitions, objective measures and recording tools for assessing pediatric chest radiographic quality are required.

Radiation dose of digital radiography (DR) versus micro-dose x-ray (EOS) on patients with adolescent idiopathic scoliosis: 2016 SOSORT- IRSSD "John Sevastic Award" Winner in Imaging Research

BACKGROUND

Patients with adolescent idiopathic scoliosis (AIS) frequently receive x-ray imaging at diagnosis and subsequent follow monitoring. The ionizing radiation exposure has accumulated through their development stage and the effect of radiation to this young vulnerable group of patients is uncertain. To achieve the ALARA (as low as reasonably achievable) concept of radiation dose in medical imaging, a slot-scanning x-ray technique by the EOS system has been adopted and the radiation dose using micro-dose protocol was compared with the standard digital radiography on patients with AIS.

METHODS

Ninety-nine participants with AIS underwent micro-dose EOS and 33 underwent standard digital radiography (DR) for imaging of the whole spine. Entrance-skin dose was measured using thermoluminescent dosimeters (TLD) at three regions (i.e. dorsal sites at the level of sternal notch, nipple line, symphysis pubis). Effective dose and organ dose were calculated by simulation using PCXMC 2.0. Data from two x-ray systems were compared using independent-samples t-test and significance level at 0.05. All TLD measurements were conducted on PA projection only. Image quality was also assessed by two raters using Cobb angle measurement and a set of imaging parameters for optimization purposes.

RESULTS

Entrance-skin dose from micro-dose EOS system was 5.9-27.0 times lower at various regions compared with standard DR. The calculated effective dose was 2.6 ± 0.5 (μSv) and 67.5 ± 23.3 (μSv) from micro-dose and standard DR, respectively. The reduction in the micro-dose was approximately 26 times. Organ doses at thyroid, lung and gonad regions were significantly lower in micro-dose (p < 0.001). Data were further compared within the different gender groups. Females received significantly higher (p < 0.001) organ dose at ovaries compared to the testes in males. Patients with AIS received approximately 16-34 times lesser organ dose from micro-dose x-ray as compared with the standard DR. There was no significant difference in overall rating of imaging quality between EOS and DR. Micro-dose protocol provided enough quality to perform consistent measurement on Cobb angle.

CONCLUSIONS

Entrance-skin dose, effective dose and organ dose were significantly reduced in micro-dose x-ray. The effective dose of a single micro-dose x-ray (2.6 μSv) was less than a day of background radiation. As AIS patients require periodic x-ray follow up for surveillance of curve progression, clinical use of micro-dose x-ray system is beneficial for these young patients to reduce the intake of ionizing radiation.

Short-term impact of pictorial posters and a crash course on radiographic errors for improving the quality of paediatric chest radiographs in an unsupervised unit - a pilot study for quality-assurance outreach

BACKGROUND

Chest radiography is the most commonly performed diagnostic X-ray examination. The radiation dose to the patient for this examination is relatively low but because of its frequent use, the contribution to the collective dose is considerable. Optimized image quality not only allows for more accurate diagnosis but also supports radiation protection, which is particularly important in children.

OBJECTIVE

To determine whether the introduction of a poster of technical errors in paediatric radiography accompanied by a short lecture (crash course) for radiographers on common errors can sustainably decrease the number and rate of these errors in an unsupervised radiology department (without a paediatric-trained radiologist or paediatric-trained radiography personnel).

MATERIALS AND METHODS

We conducted a pilot study for quality-assurance outreach, with retrospective and prospective components, in the paediatric radiology department of a teaching hospital. The technical errors in frontal chest radiographs performed in the unit were assessed by quality-assurance analysis using a customized tick-sheet. The review was performed before and after an intervention that involved a half-hour crash course and poster displays in the department. We compared the rate of technical errors made before and after the intervention.

RESULTS

There was statistically significant improvement in quality of radiographs (P < 0.0083) performed immediately after the intervention. There was a statistically significant decline in the quality of radiographs performed >2 months after the intervention.

CONCLUSION

A simple intervention of a crash course and poster placement resulted in improved quality of paediatric chest radiographs. A decline in quality after 2 months suggests the need to repeat this or another type of intervention regularly.

A comparative study of collimation in bedside chest radiography for preterm infants in two teaching hospitals

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Potential factors influencing non-optimal image collimation in the setting of bedside chest X-ray in preterm infants were investigated.

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A comparable rate of optimal images was observed in two hospitals.

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Size, weight or disease severity had no influence on collimation quality.

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Unrelated to the years of experience a large variation of the technician in correct collimation was noted (18–86%).

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Individualized quality control and education is necessary.

Objective

Unnecessary exposure of the abdomen, arms or head may lead to a substantial increase of the radiation dose in portable chest X-rays on the neonatal intensive care unit. The objective was to identify potential factors influencing inappropriate exposure of non-thoracic structures in two teaching hospitals.

Methods

The study analysed 200 consecutive digital chest radiographs in 20 preterm neonates (mean gestation 25 ± 1 weeks). Demographical data, tube settings and exposure parameters were recorded. To grade the collimation, we used a scoring system with a maximum of 12 exposed non-thoracic structures. Length of gestation, age, the radiographer, years of experience in performing X-rays and the number of in situ catheters or lines, were correlated with collimation quality.

Results

There was no significant difference between the rates of optimal images obtained in the two hospitals (0.32 vs 0.39, n.s.). Scores showed that most suboptimal images had only mildly reduced image quality (1.40 ± 1.38 vs 1.20 ± 1.43, n.s.). Length of gestation or presence of surgical drains, catheters and tubes had no obvious effects on the exposure of non-thoracic structures. Large intra-individual variation in optimal collimation (14–86%) was noted for the radiographers in both hospitals; this was unrelated to their respective years of experience.

Conclusion

In our study, the only identifiable factor influencing the collimation of portable chest radiographs in preterm infants was the radiographer’s dedication and awareness. There were no apparent differences between the hospitals investigated. Exposure of non-thoracic structures was relatively frequent and mainly involved the proximal humeri.

Paediatric x-ray radiation dose reduction and image quality analysis

Collaboration of multiple staff groups has resulted in significant reduction in the risk of radiation-induced cancer from radiographic x-ray exposure during childhood. In this study at an acute NHS hospital trust, a preliminary audit identified initial exposure factors. These were compared with European and UK guidance, leading to the introduction of new factors that were in compliance with European guidance on x-ray tube potentials. Image quality was assessed using standard anatomical criteria scoring, and visual grading characteristics analysis assessed the impact on image quality of changes in exposure factors. This analysis determined the acceptability of gradual radiation dose reduction below the European and UK guidance levels. Chest and pelvis exposures were optimised, achieving dose reduction for each age group, with 7%-55% decrease in critical organ dose. Clinicians confirmed diagnostic image quality throughout the iterative process. Analysis of images acquired with preliminary and final exposure factors indicated an average visual grading analysis result of 0.5, demonstrating equivalent image quality. The optimisation process and final radiation doses are reported for Carestream computed radiography to aid other hospitals in minimising radiation risks to children.

Variation in radiographic protocols in paediatric interventional cardiology

The aim of this work is to determine current radiographic protocols in paediatric interventional cardiology (IC) in the UK and Ireland. To do this we investigated which imaging parameters/protocols are commonly used in IC in different hospitals, to identify if a standard technique is used and illustrate any variation in practice. A questionnaire was sent to all hospitals in the UK and Ireland which perform paediatric IC to obtain information on techniques used in each clinical department and on the range of clinical examinations performed. Ethical and research governance approval was sought from the Office for Research Ethics Committees Northern Ireland and the individual trusts. A response rate of 79% was achieved, and a wide variation in technique was found between hospitals. The main differences in technique involved variations in the use of an anti-scatter grid and the use of additional filtration to the radiation beam, frame rates for digital acquisition and pre-programmed projections/paediatric specific programming in the equipment. We conclude that there is no standard protocol for carrying out paediatric IC in the UK or Ireland. Each hospital carries out the IC procedure according to its own local protocols resulting in a wide variation in radiation dose.

An analysis of radiation dose reduction in paediatric interventional cardiology by altering frame rate and use of the anti-scatter grid

The purpose of this work is to investigate removal of the anti-scatter grid and alteration of the frame rate in paediatric interventional cardiology (IC) and assess the impact on radiation dose and image quality. Phantom based experimental studies were performed in a dedicated cardiac catheterisation suite to investigate variations in radiation dose and image quality, with various changes in imaging parameters. Phantom based experimental studies employing these variations in technique identified that radiation dose reductions of 28%-49% can be made to the patient with minimal loss of image quality in smaller sized patients. At present, there is no standard technique for carrying out paediatric IC in the UK or Ireland, resulting in the potential for a wide variation in radiation dose. Dose reductions to patients can be achieved with slight alterations to the imaging equipment with minimal compromise to the image quality. These simple modifications can be easily implemented in clinical practice in IC centres.

ICRP publication 121: radiological protection in paediatric diagnostic and interventional radiology

Paediatric patients have a higher average risk of developing cancer compared with adults receiving the same dose. The longer life expectancy in children allows more time for any harmful effects of radiation to manifest, and developing organs and tissues are more sensitive to the effects of radiation. This publication aims to provide guiding principles of radiological protection for referring clinicians and clinical staff performing diagnostic imaging and interventional procedures for paediatric patients. It begins with a brief description of the basic concepts of radiological protection, followed by the general aspects of radiological protection, including principles of justification and optimisation. Guidelines and suggestions for radiological protection in specific modalities - radiography and fluoroscopy, interventional radiology, and computed tomography - are subsequently covered in depth. The report concludes with a summary and recommendations. The importance of rigorous justification of radiological procedures is emphasised for every procedure involving ionising radiation, and the use of imaging modalities that are non-ionising should always be considered. The basic aim of optimisation of radiological protection is to adjust imaging parameters and institute protective measures such that the required image is obtained with the lowest possible dose of radiation, and that net benefit is maximised to maintain sufficient quality for diagnostic interpretation. Special consideration should be given to the availability of dose reduction measures when purchasing new imaging equipment for paediatric use. One of the unique aspects of paediatric imaging is with regards to the wide range in patient size (and weight), therefore requiring special attention to optimisation and modification of equipment, technique, and imaging parameters. Examples of good radiographic and fluoroscopic technique include attention to patient positioning, field size and adequate collimation, use of protective shielding, optimisation of exposure factors, use of pulsed fluoroscopy, limiting fluoroscopy time, etc. Major paediatric interventional procedures should be performed by experienced paediatric interventional operators, and a second, specific level of training in radiological protection is desirable (in some countries, this is mandatory). For computed tomography, dose reduction should be optimised by the adjustment of scan parameters (such as mA, kVp, and pitch) according to patient weight or age, region scanned, and study indication (e.g. images with greater noise should be accepted if they are of sufficient diagnostic quality). Other strategies include restricting multiphase examination protocols, avoiding overlapping of scan regions, and only scanning the area in question. Up-to-date dose reduction technology such as tube current modulation, organ-based dose modulation, auto kV technology, and iterative reconstruction should be utilised when appropriate. It is anticipated that this publication will assist institutions in encouraging the standardisation of procedures, and that it may help increase awareness and ultimately improve practices for the benefit of patients.

Application of dosimetry systems and cytogenetic status of the child population exposed to diagnostic X-rays by use of the cytokinesis-block micronucleus cytome assay

Low-dose ionizing radiation used for medical purposes is one of the definite risk factors for cancer development, and children exposed to ionizing radiation are at a relatively greater cancer risk as they have more rapidly dividing cells than adults and have longer life expectancy. Since cytokinesis-block micronucleus cytome (CBMN Cyt) assay has become one of the standard endpoints for radiation biological dosimetry, we used that assay in the present work for the assessment of different types of chromosomal damage in children exposed to diagnostic X-ray procedures. Twenty children all with pulmonary diseases between the ages of 4 and 14 years (11.30 ± 2.74) were evaluated. Absorbed dose measurements were conducted for posterior-anterior projection on the forehead, thyroid gland, gonads, chest and back. Doses were measured using thermoluminescence and radiophotoluminescent dosimetry systems. It was shown that, after diagnostic X-rays, the mean total number of CBMN Cyt assay parameters (micronucleus, nucleoplasmic bridges and nuclear buds) was significantly higher than prior to diagnostic procedure and that interindividual differences existed for each monitored child. For the nuclear division index counted prior and after examination, no significant differences were noted among mean group values. These data suggest that even low-dose diagnostic X-ray exposure may induce damaging effect in the somatic DNA of exposed children, indicating that immense care should be given in both minimizing and optimizing radiation exposure to diminish the radiation burden, especially in the youngest population.

Primary DNA damage assessed with the comet assay and comparison to the absorbed dose of diagnostic X-rays in children

The aim of this work is to assess DNA damage in peripheral blood lymphocytes of children prior to and following airway X-ray examinations of the chest using the alkaline comet assay and to compare data with the measured absorbed dose. Twenty children with pulmonary diseases, between the ages of 5 and 14 years, are assessed. Absorbed dose measurements are conducted for posterior-anterior projection on the forehead, thyroid gland, gonads, chest, and back. Doses are measured using thermoluminescent and radiophotoluminescent dosimetry systems. Differences between tail lengths, tail intensity, and tail moments as well as for the long-tailed nuclei before and after exposures are statistically significant and are dependent on the individual. The results demonstrate the usefulness of the comet assay as a measure of X-ray damage to lymphocytes in a clinical setting. Doses measured with both dosimeters show satisfactory agreement (0.01 mSv) and are suitable for dosimetric measurements in X-ray diagnostics.

The additional dose to radiosensitive organs caused by using under-collimated X-ray beams in neonatal intensive care radiography

Radiographic technique and exposure parameters were recorded in five Israeli Neonatal Intensive Care Units for chest, abdomen and both chest and abdomen X-ray examinations. Equivalent dose and effective dose values were calculated according to actual examination field size borders and proper technique field size recommendations using PCXMC, a PC-based Monte Carlo program. Exposure of larger than required body areas resulted in an increase of the organ doses by factors of up to 162 (testes), 162 (thyroid) and 8 (thyroid) for chest, abdomen and both chest and abdomen examinations, respectively. These exposures increased the average effective dose by factors of 2.0, 1.9 and 1.3 for the chest, abdomen and both chest and abdomen examinations, respectively. Differences in exposure parameters were found between the different neonatal intensive care units-tube voltage, current-time product and focal to skin distance differences up to 13, 44 and 22%, respectively. Reduction of at least 50% of neonate exposure is feasible and can be implemented using existing methodology without any additional costs.

Dose and image quality optimization in neonatal radiography

In a special care baby unit, neonates, mainly premature, encounter serious to life-threatening diseases, the timely diagnosis and treatment of which may require a large number of radiographs. Increased neonatal radiosensitivity and longer life expectancy increase the risk of radiation-induced cancer, which emphasizes the importance of minimizing dose while maintaining clinically satisfactory image quality. An optimization study on radiation dose and image quality in neonatal radiography is presented. Neonates were categorized into four groups depending on birthweight. For a total of 378 chest and chest-abdomen radiographs, exposure parameters were recorded. Entrance surface dose (ESD) was estimated and dose-area product (DAP) was measured. Image quality evaluation was performed by two observers and was based on the visibility of certain anatomical features and catheters placed during treatment using a five-grade scale. ESD values increased with neonatal weight and demonstrated wide variation (16.4-76.9 microGy, mean 38.2 microGy). A wide variation was also observed in DAP values (1.2-15.0 mGycm2, mean 7.2 mGycm2). Image quality evaluation revealed the feasibility of achieving a diagnostically satisfactory image (score >70%) using both low and high tube voltage techniques, with the latter resulting in reduced ESDs. The majority of estimated ESDs are in accordance with the reference level of 50 microGy recommended by the National Radiological Protection Board for neonatal radiography. The results suggest that the use of high tube voltage techniques could result in further reductions in neonatal dose, without image quality degradation, underlying the requirement for establishing standard examination protocols for neonatal radiography with respect to neonatal weight.

Unintentional exposure of neonates to conventional radiography in the Neonatal Intensive Care Units

OBJECTIVE

To evaluate the extent of unintentional exposure to X-rays performed during routine diagnostic procedures in the Neonatal Intensive Care Units (NICUs).

STUDY DESIGN

During a 1-month period, 157 consecutive neonates from five level-III NICUs were recruited for this study. The mean birth weight was 1747+/-911 g (range: 564-4080 g), and gestational age was 31.6+/-3.6 weeks (range: 24-41 weeks). A total of 500 radiographs were performed including chest (68%), abdomen (17%) and combined chest and abdomen (15%). The average number of radiographs taken per infant was 4.2+/-3.6 (range: 1-21). Unintentional inclusion of body regions other than those ordered was determined by comparing the areas that should be included in the radiation field according to International recommendations, to those that appeared in the actual radiograph.

RESULT

A comparison of the recommended borders to the actual boundaries of the radiographs taken show an additional exposure to radiation in all three procedures: 85% of chest radiographs also included the whole abdomen, 64% of abdomen radiographs included both thigh and upper chest and 62% of chest and abdomen radiograph included the thigh. (The range in all procedures was from ankle to upper head.) Between 2 and 20% of the relevant targeted body tissues were not included in the exposed fields resulting in missing data. The gonads of both sexes were exposed in 7% in all chest X-rays. Among male infants, the testes were exposed in 31% of plain abdomen radiographs and 34% of chest and abdomen radiographs.

CONCLUSION

In the NICUs participating in the study, neonates are currently being exposed to X-ray radiation in nonrelevant body regions. Higher awareness and training of the medical teams and radiographers are required to minimize unnecessary exposure of newborns to ionizing radiation.

Revisit image control for pediatric chest radiography

PURPOSE

The aim of this study was to analyze the fraction defectiveness and efficacy of the patient immobilization device (PID) for pediatric chest radiography.

MATERIALS AND METHODS

We examined 840 plain chest radiographs in six hospitals, including four children's hospitals and two general hospitals. The mean age of the patients was 1.9 years (range 0-5 years). Two board-qualified pediatric radiologists rated (into three grades, by consensus) the degree of inspiration, rotation, lordosis, scoliosis, and cutoff or coning as well as the quality of the chest radiographs.

RESULTS

The incidence of "poor" and "very poor" quality examinations was 2/140 and 3/140 in each of two children's hospitals using PID. The corresponding figures were 9/139 and 17/140 in the two children's hospitals that did not use PID. The general hospital using PID had 14/140 "poor" and "very poor" examinations. The general hospital that did not use PID had 28/140 "poor" and "very poor" examinations. Thus, statistically better quality chest radiography was obtained with the use of PID (P < 0.001). Likewise, rotation, lordosis, and scoliosis were less frequently diagnosed as present when PID was used (P < 0.001, 0.001, 0.05). Cutoff or coning had no relation to the use of PID (P = 0.13). No significant difference was found between the degree of inspiration and the use of PID (P = 0.56).

CONCLUSION

Fraction defectiveness in the general hospital that did not use PID was as much as 14 times higher than that of the children's hospitals that used PID. The patient immobilization device is recommended for hospitals with technologists not specifically trained for pediatric examination.

Optimized radiographic spectra for small animal digital subtraction angiography

The increasing use of small animals in basic research has spurred interest in new imaging methodologies. Digital subtraction angiography (DSA) offers a particularly appealing approach to functional imaging in the small animal. This study examines the optimal x-ray, molybdenum (Mo) or tungsten (W) target sources, and technique to produce the highest quality small animal functional subtraction angiograms in terms of contrast and signal-difference-to-noise ratio squared (SdNR2). Two limiting conditions were considered-normalization with respect to dose and normalization against tube loading. Image contrast and SdNR2 were simulated using an established x-ray model. DSA images of live rats were taken at two representative tube potentials for the W and Mo sources. Results show that for small animal DSA, the Mo source provides better contrast. However, with digital detectors, SdNR2 is the more relevant figure of merit. The W source operated at kVps >60 achieved a higher SdNR2. The highest SdNR2 was obtained at voltages above 90 kVp. However, operation at the higher potential results in significantly greater dose and tube load and reduced contrast quantization. A reasonable tradeoff can be achieved at tube potentials at the beginning of the performance plateau, around 70 kVp, where the relative gain in SdNR2 is the greatest.

Evaluation of radiation dose and image quality following changes to tube potential (kVp) in conventional paediatric chest radiography

PURPOSE

A study of radiation dose and image quality following changes to the tube potential (kVp) in paediatric chest radiography.

MATERIALS AND METHOD

A total of 109 patients ranging from 1 month to 15 years were included in two phases of the study. Phase 1 investigated the range of entrance surface air kerma (ESAK) values received from patients exposed to the existing exposure factors. In the second phase, new exposure factors using recommended values of tube potential (kVp) with reduced mAs were used. ESAK values were measured using thermoluminescent dosemeters (TLDs). Image quality in both phases was evaluated using image quality criteria proposed by the Council of the European Communities (CEC). Results of both techniques were analysed for any differences.

RESULTS

The overall mean ESAK before the changes was 0.22 mGy (range: 0.05-0.43) Following changes in tube potential, the overall mean reduced to 0.15 mGy (range: 0.03-0.38), a significant reduction by 34%. The interquartile range was reduced from 45% to 40%. However, doses to those below a year in age still remained high. Assessment of image quality was found to have no significant differences as far as the two techniques used were concerned. However, higher image scores were achieved using higher kVps.

CONCLUSION

Significant dose reduction was achieved through appropriate changes in tube potential and reduction of mAs without any loss in image quality.

A review of current local dose-area product levels for paediatric fluoroscopy in a tertiary referral centre compared with national standards. Why are they so different?

A prospective single centre study has been performed to assess dose-area product (DAP) values in children having fluoroscopic examinations and to revise local diagnostic reference levels (DRLs). DAP measurements for 2658 examinations performed in a dedicated fluoroscopy room over a period of 21 months were analysed. Data for the eight most commonly performed examinations (2215 cases) are presented. DAPs (75th centile) for upper gastrointestinal studies and micturating cystograms are substantially lower (by a factor of between x 5 and x 25) than the current national reference doses (NRDs), with some of the median values being 50 times lower. The small DAP values in all examinations demonstrate the substantial reduction in dose and consequent risk that can be achieved when both equipment performance and operator technique are optimized. Whilst we recognize that different institutions will have differing practices, it is important that practitioners are aware of the range of DAPs achievable and that NRDs do not necessarily represent best practice, and may falsely reassure.

Cumulative effective doses delivered by radiographs to preterm infants in a neonatal intensive care unit

OBJECTIVE

We sought to determine the number and distribution of radiographs and the cumulative effective radiograph doses (cED) received by a population of preterm infants (PIs) hospitalized in an NICU.

STUDY DESIGN

We reviewed the files of all preterm infants (gestational age: <34 weeks) who were admitted to an NICU during an 18-month period and were discharged alive. A generalized additive model was used to study the relationship between cED and patient characteristics.

RESULTS

Four hundred fifty files were analyzed. The median gestational age was 30.1 weeks (range: 24.1-33.9 weeks), and the median birth weight was 1250 g (range: 520-2760 g). The median number of radiographs per infant was 10.6 (range: 0-95), and the median cED was 138 microSv (range: 0-1450 microSv). The cumulative dose exceeded 500 microSv in 7.6% of the cases. Factors that influenced the cumulative effective dose were gestational age, birth weight, care procedures, and clinical adverse events.

CONCLUSIONS

Given the potentially life-threatening complications of PIs, cumulative radiograph doses received in the ICU seem low with regard to environmental exposure and international recommendations. Additional studies are needed to evaluate the possible lifetime consequences of exposure to ionizing radiation at this age.

Optimal exposure parameters for digital radiography of the infant skull: A pilot study

AIM

To determine optimal exposure parameters when performing digital skull radiographs in infants with suspected non-accidental injury (NAI).

METHOD

Anteroposterior and lateral post-mortem skull radiographs of six consecutive infants with suspected NAI were made at six exposure levels for each projection. Entrance surface doses ranged from 75-351 microGy. Exposures were made with a Fuji 5000R computed radiography system onto a standard resolution imaging plate. In three patients exposures were repeated using a high-resolution imaging plate. Hard copy images with an edge-enhancement factor of 0.5 were produced. Six observers assessed and scored the radiographs from 1=poor to 5=excellent for visualization of five criteria. The criteria scored included outer table of skull vault, inner table of skull vault, suture margins, vascular markings and soft tissues of the scalp. Radiographs were then ranked in order of overall image quality. Film density and sensitivity values were recorded. Local research committee approval was obtained.

RESULTS

Current parameters give an average entrance surface dose of 253 microGy and 246 microGy for anteroposterior and lateral radiographs, respectively. The study demonstrated no perceived improvement in image quality above an entrance surface dose of 200 microGy (80% of current dose) or by the use of a high-resolution imaging plate.

CONCLUSION

The potential exists to reduce radiation exposure in infants. A study has commenced to determine the effects of dose reduction on diagnostic accuracy in suspected NAI.

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.

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.

Evaluation of the Commission of the European Communities quality criteria for the paediatric lateral spine

The study aimed to evaluate the Commission of the European Communities (CEC) quality criteria for paediatric lateral spine radiographs, and to use these to assess and compare the quality of film-screen and digital images. 286 paediatric lateral spine radiographs (89 film-screen and 197 digital) were independently analysed by two observers according to the CEC criteria. Based on fulfilment of criteria, images were assigned two scores, an image criteria score and a visual grading analysis score. Sensitivity values (S) on digital radiographs were recorded and correlated with image quality. Variability for assignment of scores between observers was lower for the image criteria than the visual grading analysis technique. Analysis of variance for fulfilment of criteria between techniques, and (for digital images) age and sensitivity values was calculated. Film-screen did significantly better (p<0.05) than digital imaging for Criterion 6 (visually sharp reproduction of the cortex and trabecular markings consistent with age), but significantly worse for Criterion 7 (reproduction of the adjacent soft tissues). There was a significant difference in mean S values for each age group when Criterion 6 was or was not met. Results show that although interpretation between two observers was ambiguous, the CEC criteria were able to detect differences in quality of film-screen and digital images. It is also possible to use them when optimizing target S values.