Diagnostic image quality of mobile neonatal chest X-rays and the radiation exposure incurred

Radiation dose evaluation to organs in neonatal patients by field size during potable X-ray examination in incubators: A Monte Carlo simulation study

BACKGROUND

Neonatal patients located in incubators are exposed to as many as 159 radiographs until discharge. To reduce the dose exposed to the patient, factors that may cause unnecessary exposure to the patient were judged. When conducting portable X-rays of neonatal patients located in an incubator, it is not easy to determine the exact field size because collimation light is exposed on the acrylic plate, an incubator canopy, and the resulting shadow is reflected on the patient's body.

OBJECTIVE

This study aims to measure the organ dose exposed to the patient according to the field size when a portable radiograph is given to a neonatal patient in a neonatal intensive care unit (NICU) incubator.

METHODS

To identify the absorbed organ dose depending on the radiation field size during portable X-ray examination of neonatal patient, a Monte Carlo N-Particle (MCNP) simulation, a SpeckCalc program, and a neonatal phantom from the ICRP 89 are applied for the calculation. According to the minimal field size (MinFS) standards of the European Commission (EC), the smaller field size is intended to measure tightly from the top of the lung apices to the bottom of the genitals; a larger field size is also calculated by adding 6 cm in width and length.

RESULTS

Compared to the hospital C condition from the previous study, the larger and smaller field sizes are decreased by an average of 45% and 67%, respectively. Study results also show a 42% reduction in smaller field size compared to the larger field size.

CONCLUSION

When taking chest and abdomen radiographic images of neonatal patients in incubators, appropriate field sizes are required to prevent inappropriate dose absorption for non-thoracic organs.

Organ doses in preterm and full-term neonates and infants - a retrospective study on 1,064 chest radiographs

BACKGROUND

Chest radiography is the most frequent X-ray examination performed in the neonatal period. However, commonly used dosimetric entities do not describe the radiation risk sufficiently.

OBJECTIVE

The aim of this study was to investigate selected organ doses and total body dose of chest radiographs in preterm and full-term neonates and infants.

MATERIALS AND METHODS

In this retrospective study, we evaluated 1,064 chest radiographs of 136 preterm and 305 full-term babies with respect to field size and centering. We calculated the entrance dose from the dose-area product. Upper and lower field borders referred to the corresponding vertebrae. We calculated individual organ doses of the thyroid, the breast, the liver and active bone marrow for each chest radiograph using the neonatal PCXMC program, a Monte Carlo program for calculating patient doses in medical X-ray examinations.

RESULTS

The median field size of chest radiographs ranged from 90 cm² in preterm neonates at birth to 290 cm² in full-term infants at the age of 6 months. Median values of entrance dose varied, depending on age, from 15 μGy to 25 μGy. The median organ doses ranged 1-20 μSv for the thyroid, 3-30 μSv for the breast, 2-20 μSv for the liver and 0.5-3.5 μSv for the bone marrow in preterm and full-term neonates and infants, respectively.

CONCLUSION

The analysis of chest radiographs in preterm and full-term neonates and infants revealed high variability in field size. By contrast, the entrance dose varied to a minor extent. Organ dose calculations using the PCXMC program might be a valuable tool to calculate the individual radiation risk in neonates and infants.

An investigation of Saudi Arabian MR radiographers' knowledge and confidence in relation to MR image-quality-related errors

OBJECTIVE

To investigate MR radiographers' current knowledge base and confidence level in relation to quality-related errors within MR images.

METHOD

Thirty-five MR radiographers within 16 MRI departments in the Kingdom of Saudi Arabia (KSA) independently reviewed a prepared set of 25 MR images, naming the error, specifying the error-correction strategy, scoring how confident they were in recognising this error and suggesting a correction strategy by using a scale of 1-100. The datasets were obtained from MRI departments in the KSA to represent the range of images which depicted excellent, acceptable and poor image quality.

RESULTS

The findings demonstrated a low level of radiographer knowledge in identifying the type of quality errors and when suggesting an appropriate strategy to rectify those errors. The findings show that only (n = 7) 20% of the radiographers could correctly name what the quality errors were in 70% of the dataset, and none of the radiographers correctly specified the error-correction strategy in more than 68% of the MR datasets. The confidence level of radiography participants in their ability to state the type of image quality errors was significantly different (p < 0.001) for who work in different hospital types.

CONCLUSION

The findings of this study suggest there is a need to establish a national association for MR radiographers to monitor training and the development of postgraduate MRI education in Saudi Arabia to improve the current status of the MR radiographers' knowledge and direct high quality service delivery.

Image quality and dose differences caused by vendor-specific image processing of neonatal radiographs

BACKGROUND

Image processing plays an important role in optimizing image quality and radiation dose in projection radiography. Unfortunately commercial algorithms are black boxes that are often left at or near vendor default settings rather than being optimized.

OBJECTIVE

We hypothesize that different commercial image-processing systems, when left at or near default settings, create significant differences in image quality. We further hypothesize that image-quality differences can be exploited to produce images of equivalent quality but lower radiation dose.

MATERIALS AND METHODS

We used a portable radiography system to acquire images on a neonatal chest phantom and recorded the entrance surface air kerma (ESAK). We applied two image-processing systems (Optima XR220amx, by GE Healthcare, Waukesha, WI; and MUSICA(2) by Agfa HealthCare, Mortsel, Belgium) to the images. Seven observers (attending pediatric radiologists and radiology residents) independently assessed image quality using two methods: rating and matching. Image-quality ratings were independently assessed by each observer on a 10-point scale. Matching consisted of each observer matching GE-processed images and Agfa-processed images with equivalent image quality. A total of 210 rating tasks and 42 matching tasks were performed and effective dose was estimated.

RESULTS

Median Agfa-processed image-quality ratings were higher than GE-processed ratings. Non-diagnostic ratings were seen over a wider range of doses for GE-processed images than for Agfa-processed images. During matching tasks, observers matched image quality between GE-processed images and Agfa-processed images acquired at a lower effective dose (11 ± 9 μSv; P < 0.0001).

CONCLUSION

Image-processing methods significantly impact perceived image quality. These image-quality differences can be exploited to alter protocols and produce images of equivalent image quality but lower doses. Those purchasing projection radiography systems or third-party image-processing software should be aware that image processing can significantly impact image quality when settings are left near default values.

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.

Radiation exposure to premature infants in a neonatal intensive care unit in Turkey

Objective

The aim of this work was to determine the radiation dose received by infants from radiographic exposure and the contribution from scatter radiation due to radiographic exposure of other infants in the same room.

Materials and Methods

We retrospectively evaluated the entrance skin doses (ESDs) and effective doses of 23 infants with a gestational age as low as 28 weeks. ESDs were determined from tube output measurements (ESD_TO) (n = 23) and from the use of thermoluminescent dosimetry (ESD_TLD) (n = 16). Scattered radiation was evaluated using a 5 cm Perspex phantom. Effective doses were estimated from ESD_TO by Monte Carlo computed software and radiation risks were estimated from the effective dose. ESD_TO and ESD_TLD were correlated using linear regression analysis.

Results

The mean ESD_TO for the chest and abdomen were 67 µGy and 65 µGy per procedure, respectively. The mean ESD_TLD per radiograph was 70 µGy. The measured scattered radiation range at a 2 m distance from the neonatal intensive care unit (NICU) was (11-17 µGy) per radiograph. Mean effective doses were 16 and 27 µSv per procedure for the chest and abdomen, respectively. ESD_TLD was well correlated with ESD_TO obtained from the total chest and abdomen radiographs for each infant (R² = 0.86). The radiation risks for childhood cancer estimated from the effective dose were 0.4 × 10^-6 to 2 × 10^-6 and 0.6 × 10^-6 to 2.9 × 10^-6 for chest and abdomen radiographs, respectively.

Conclusion

The results of our study show that neonates received acceptable doses from common radiological examinations. Although the contribution of scatter radiation to the neonatal dose is low, considering the sensitivity of the neonates to radiation, further protective action was performed by increasing the distance of the infants from each other.

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.

Radiation risk assessment in neonatal radiographic examinations of the chest and abdomen: a clinical and Monte Carlo dosimetry study

Seeking to assess the radiation risk associated with radiological examinations in neonatal intensive care units, thermo-luminescence dosimetry was used for the measurement of entrance surface dose (ESD) in 44 AP chest and 28 AP combined chest-abdominal exposures of a sample of 60 neonates. The mean values of ESD were found to be equal to 44 +/- 16 microGy and 43 +/- 19 microGy, respectively. The MCNP-4C2 code with a mathematical phantom simulating a neonate and appropriate x-ray energy spectra were employed for the simulation of the AP chest and AP combined chest-abdominal exposures. Equivalent organ dose per unit ESD and energy imparted per unit ESD calculations are presented in tabular form. Combined with ESD measurements, these calculations yield an effective dose of 10.2 +/- 3.7 microSv, regardless of sex, and an imparted energy of 18.5 +/- 6.7 microJ for the chest radiograph. The corresponding results for the combined chest-abdominal examination are 14.7 +/- 7.6 microSv (males)/17.2 +/- 7.6 microSv (females) and 29.7 +/- 13.2 microJ. The calculated total risk per radiograph was low, ranging between 1.7 and 2.9 per million neonates, per film, and being slightly higher for females. Results of this study are in good agreement with previous studies, especially in view of the diversity met in the calculation methods.

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.

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.

Portable chest radiographs in the intensive care units: referral patterns and estimated cumulative radiation exposures

The objective of this article was to determine the frequency of referrals for portable chest radiographs from medical and (noncardiac) surgical intensive care units (NICU and SICU) and their respective stepdown units (NICA and SICA). Additionally, the cumulative entrance skin exposure (ESE) using an ion chamber was determined. We retrospectively reviewed the medical records of all adult patients admitted to the MICU, SICU, MICA, and SICA at a tertiary referral center during a 6-month interval. The duration of stay and the number of portable chest radiographs were determined for each patient. The measured ESEs from all portable radiography units ranged from 5 to15 mR (average: 10mR). The cumulative radiation exposure for each patient was calculated. There were 567 patients admitted to the units: 146 surgical and 421 medical. Their ages ranged from 15 to 87 years. The duration of stay varied from 1 to 68 days. A total of 3,794 portable chest radiographs were obtained. The number of radiographs per patient varied from 1 to 94. The number of radiographs and the corresponding cumulative radiation doses were as follows: 406 patients (72%) had fewer than five radiographs (<50 mR); 76 (13%) had five to 10 radiographs (<100 mR); 35 (6%) had 11 to 20 (<200 mR); and 50 (9%) had more than 20 chest radiographs (>200 mR). The cumulative ESE ranged from 10 to 940 mR. It exceeded 450 mR in only nine (1.5%) patients. Most (73%) patients undergoing intensive care undergo fewer than five radiographs during their stay in the units. Patient exposure from portable chest radiographs in this population is less than the average annual exposure from background radiation in the USA (450-500 mR), and is much less than the average annual exposure from teratogenic radiation.

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.