Radiation Dose In Children Research Articles

Paediatric multi detector computed tomography radiation doses in a dedicated paediatric hospital in Greece

Introduction Multi detector CT (MDCT) X-ray systems provide high quality paediatric imaging. However, the last years, concern has been expressed on radiation exposure to children. Very few surveys depicting paediatric exposure from MDCT s are available. Purpose To shape the status of radiation dose in children from MDCT practice in a dedicated paediatric hospital in Greece. Materials and methods This was a retrospective study in a 160 bed paediatric hospital equipped with a Philips Brilliance 16 CT scanner installed in 2010. Patient data and acquisition parameters were recorded for CT studies of head, abdomen, chest and spine and were divided in three age groups (1–5 years, 5–10 years, 10–15 years). The dosimetric results were reported in terms of volumetric CT dose index (CTDIvol) (mGy), dose length product (DLP) (mGycm), and total DLP for multiphase studies. The results were compared with adult national DRLs and paediatric European published data. Results Data were collected from 97 MDCT examinations and included 39 head CTs, 12 abdomen CTs, 20 chest CTs and 26 spine CTs. Acquisition parameters used were according to age for head CTs and weight-dependent for the other scans. Spiral or axial scan depended on anatomic area and on the radiologist on duty. Multiphase studies accounted for 10% of patient sample, 80% of these in the abdomen region. For the three age groups, CTDIvol, DLP and total DLP average values were significantly lower than adult national DRLs, although they increased with age, and were in accordance with published paediatric European data. Conclusion Initial data showed that use of protocols tailored to patient’s age or weight results in significant dose reduction. Use of standardized CT protocols should be encouraged.

A Matlab based interface for infrared thermographic diagnosis of pediatric musculoskeletal injuries

Background and objectiveOne of the main causes of emergency medical consultations done by children are musculoskeletal injures. In such cases, radiological tests are a common practice to diagnose the gravity of the trauma and determine the likely existence of a fracture. In order to avoid, or at least to reduce, the use of ionizing radiations with children, the infrared thermographic technique was studied as an alternative solution, since it is a non-harmful, non-invasive and non-contact technique, without excessive technical complications and moderate cost when compared to other types of imaging tools. MethodologyWhen an infrared thermographic diagnostic test is performed, and once the pictures of the studied limb are taken accordingly to the established methodology, an imaging post-processing protocol becomes necessary to make a correct interpretation and diagnosis. Aimed at performing the analysis in situ and in real time, in this work we present a software tool based on a Matlab interface. The software programming is based on the results obtained in clinical tests, where several variables were took into consideration. The program is able to determine the probability of fracture basing the diagnosis on a non-linear cataloguing approach, using decision trees. ResultsThe tool implemented allows to diagnose musculoskeletal injures in children shortly after taking the infrared thermographic picture. ConclusionsThe diagnosis tool provides the means for the interpretation of the IT pictures, allows to obtain a diagnosis in a fast way, and may help to decrease the radiation doses in children.

Radiation Dose in Diagnostic and Therapeutic Procedures of Congenital Heart Diseases in Children

Background: There is concern about radiation dose in children during cardiovascular catheterization and many believe that the use of computerized tomography is much better than conventional catheterization and angiography. The aim of this study is to compare the radiation dose between diagnostic and therapeutic procedures in children. Methods: 178 patients with congenital heart disease enrolled in this study. Patients have been divided into 3 groups of CT angiography, conventional angiography and intervention. Data include: sex, age, weight, fluoroscopy time, total radiation dose of CT angiography, the amount of reference point air Kerma (Ka, r) (reference dose) and kerma area product (Pka) of fluoroscopy machine. Peak skin dose (PSD) was calculated for intervention and conventional angiography patients using the following formula: PSD = 249 + 5.2 × PKA. The data has been analyzed by SPSS version 20. In this study the P-value less than 0.05 was considered meaningful. Results: The patients were similar in sex, age and weight in all the three groups. The mean reference point air kerma (ka,r) in intervention group was meaningfully higher than the other two groups (P < 0.001) , but in some patients of CT Angiography group the radiation dose was higher than conventional angiography group. The mean kerma area product (pka) in intervention group was higher than angiography group, although this difference is less meaningful statistically (P = 0.049). The Fluoroscopy time (P = 0.035) in intervention group was meaningfully higher than angiography group. The mean calculated pick skin dose (PSD) was 437 ± 383 miligray and 213 ± 508 miligray for intervention and conventional angiography groups respectively (P < 0.001). In intervention group, Fluoroscopy time (P = 0.037), ka,r (P = 0.17) ( and Pka (P = 0.02) are more about VSD closure than other procedures. Conclusions: Given the results of this study, the use of fluoroscopy for diagnosis and treatment of pediatric cardiovascular diseases is safe but with due attention to sensitivity of children to some side effects of X-ray compared to adults, considering safety advices in order to reduce fluoroscopy time, radiation dose and the use of standard protection to reduce X-ray absorption is necessary.

Radiation dose reduction in paediatric coronary computed tomography: assessment of effective dose and image quality.

To assess the impact of different protocols on radiation dose and image quality for paediatric coronary computed tomography (cCT). From January-2012 to June-2014, 140 children who underwent cCT on a 64-slice scanner were included. Two consecutive changes in imaging protocols were performed: 1) the use of adaptive statistical iterative reconstruction (ASIR); 2) the optimization of acquisition parameters. Effective dose (ED) was calculated by conversion of the dose-length product. Image quality was assessed as excellent, good or with significant artefacts. Patients were divided in three age groups: 0-4, 5-7 and 8-18years. The use of ASIR combined to the adjustment of scan settings allowed a reduction in the median ED of 58%, 82% and 85% in 0-4, 5-7 and 8-18years group, respectively (7.3 ± 1.4 vs 3.1 ± 0.7mSv, 5.5 ± 1.6 vs 1 ± 1.9mSv and 5.3 ± 5.0 vs 0.8 ± 2.0mSv, all p < 0,05). Prospective protocol was used in 51% of children. The reduction in radiation dose was not associated with reduction in diagnostic image quality as assessed by the frequency of coronary segments with excellent or good image quality (88%). cCT can be obtained at very low radiation doses in children using ASIR, and prospective acquisition with optimized imaging parameters. • Using ASIR allows 25 % to 41 % reduction in the ED. • Prospective protocol is used up to 51 % of children after premedication. • Low dose is possible using ASIR and optimized prospective paediatric cCT.

Direct physician reporting is associated with reductions in radiation exposure in pediatric cardiac catheterizations.

The objective is to quantify radiation dose in children undergoing cardiac catheterization and determine the impact of increased reporting transparency on total radiation exposure. Cardiac catheterization (cath) can result in significant radiation exposure in children. There has been growing interest in quantifying and reducing radiation exposure in pediatric cath procedures. Our center underwent a slight change in practice recently that resulted in direct physician reporting of radiation dose following every case. We reviewed cath procedures across three different eras in four cath categories: post-heart transplant annual cath, unilateral pulmonary artery (PA) stent placement, pre-Fontan cath, and pre-Glenn cath. The eras were defined as: Era 1, 1/2009-1/2011; Era 2, 1/2011-9/2013; and Era 3, 9/2013-5/2014. In Era 3, the physician performing the cath was responsible for reporting the radiation data. Across the three eras, there were significant decreases in cumulative air KERMA (mGy) among all four cath categories. From Era 2 to Era 3, the greatest decreases in radiation were noted, particularly in dose area product (cGy·cm2) in the transplant annual evaluation and pre-Glenn cases. In Era 1, 2 cases (1.2%) had a frame rate reduction, while in Era 2, 22 cases (12.0%), and in Era 3, 83 cases (21.6%) had frame rate changes (P<0.01). Increased physician awareness of radiation exposure is associated with a significant reduction in radiation dose across a variety of cath procedures. This is seen not only by the overall reduction in radiation across case types, but also as the frame rate was more frequently changed during individual cases, indicating an important change in physician behavior and practice.

Limiting CT radiation dose in children with craniosynostosis: phantom study using model-based iterative reconstruction.

Medical professionals need to exercise particular caution when developing CT scanning protocols for children who require multiple CT studies, such as those with craniosynostosis. To evaluate the utility of ultra-low-dose CT protocols with model-based iterative reconstruction techniques for craniosynostosis imaging. We scanned two pediatric anthropomorphic phantoms with a 64-slice CT scanner using different low-dose protocols for craniosynostosis. We measured organ doses in the head region with metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters. Numerical simulations served to estimate organ and effective doses. We objectively and subjectively evaluated the quality of images produced by adaptive statistical iterative reconstruction (ASiR) 30%, ASiR 50% and Veo (all by GE Healthcare, Waukesha, WI). Image noise and contrast were determined for different tissues. Mean organ dose with the newborn phantom was decreased up to 83% compared to the routine protocol when using ultra-low-dose scanning settings. Similarly, for the 5-year phantom the greatest radiation dose reduction was 88%. The numerical simulations supported the findings with MOSFET measurements. The image quality remained adequate with Veo reconstruction, even at the lowest dose level. Craniosynostosis CT with model-based iterative reconstruction could be performed with a 20-μSv effective dose, corresponding to the radiation exposure of plain skull radiography, without compromising required image quality.

A Phase I–II, Open-Label, Multicenter Trial to Determine the Dosimetry and Safety of 99mTc-Sestamibi in Pediatric Subjects

Myocardial perfusion imaging has long been used off label by practitioners attending for children with cardiac aliments. To provide clinicians with evidence-based dosage recommendation, a phase I-II, open-label, nonrandomized, multicenter trial was therefore designed using (99m)Tc-sestamibi in pediatric subjects (registered under www.clinicaltrials.gov identifier no. NCT00162045). Safety and pharmacokinetic data were collected from 78 subjects using either a 1-d imaging protocol (3.7-7.4 MBq/kg, followed by 11.1 MBq/kg) or a 2-d protocol (7.4 MBq/kg for both rest and stress). Anterior and posterior planar images were collected at 15 min, 1.5 h, 4 h, and 8 h. Blood and urine samples were collected at predetermined times. Subjects included 39 children (mean age ± SD, 8.5 ± 2.04 y) and 39 adolescents (mean age ± SD, 13.6 ± 1.39 y). Mean estimated organ-absorbed doses to the upper large intestine, small intestine, gallbladder wall, and lower large intestines were 0.082, 0.043, 0.042, and 0.035 mSv/MBq, respectively. All patients tolerated the radiotracer without serious adverse effects. Significant differences were observed in the liver, upper large intestine contents, and small intestine contents between rest and stress imaging. The effective dose equivalent and effective dose averages were lower in adolescents than younger children (0.011 and 0.019 mSv/MBq, respectively; P < 0.0001). Percentage injected doses (%IDs) corrected for radioactive decay in all dosimetry-evaluable subjects at 15 min and 4 h were 1.9% and 1.2% in the myocardium. Similarly in the lungs, the %ID for all dosimetry-evaluable subjects was 4.9% at 15 min after injection. At rest, the %ID in the liver decreased from a maximum of about 26% at 15 min to less than 9% at 90 min. With stress, values decreased from 15% to 7%, respectively. The estimates of radiation dosimetry, pharmacokinetic parameters, and safety profile in this study population are similar to published studies based on body-mass extrapolations from studies in adults. As such, applying current (99m)Tc-sestamibi dosing regimens for 1- and 2-d protocols based on those extrapolations will result in the expected radiation dose in children and adolescents.

Effects of Siemens Artis Q.zen on radiation dose on patent ductus arteriosus closure: A single centre experience

Objectives: To assess the impact of the Siemens Artis Q.zen on radiation dosage during patent ductus arteriosus (PDA) device closure. Theoretical dose reduction is purported to be delivered by the use of crystalline silicon detectors in combination with the Gigalix x-ray tube that uses flat emitter technology instead of filaments. Both of these allow good image quality at low dose. Methods: Case-control comparison of patients undergoing PDA device closure in two eras – July to October of 2014 in a Siemens Artis zee laboratory (group 1) versus February of 2015 (group 2) in the Siemens Artis Q.zen laboratory. All patients undergoing PDA closure by three operators were included for analysis. Results: Group 1 comprised 11 patients compared to 9 in group 2. Group 1 median age 1.3 years (range 0.6-7 years) and weight 11kg (range 4.8-26.7kg) versus group 2 age 2.6 years (range 0.7-13.3 years) and weight 14.7kg (range 7.6-49kg). Fluoroscopy time was similar in both groups: 6.75min vs 5.73min (ranges 4.2-20min vs 1.4-13.4min). DAP in group 1 was 142uGym2 (range 42-287) versus 64uGym2 (range 32-124) in group 2. Entry dose was 32mGy (range 8-67) in group 1 vs 9 (range 6-25) in group 2. Conclusion: Conversion to the Artis Q.zen laboratory has more than halved radiation dose in children undergoing PDA closure, without any other changes in operators or procedural practice.

Radiation doses for pediatric nuclear medicine studies: comparing the North American consensus guidelines and the pediatric dosage card of the European Association of Nuclear Medicine

Estimated radiation dose is important for assessing and communicating the risks and benefits of pediatric nuclear medicine studies. Radiation dose depends on the radiopharmaceutical, the administered activity, and patient factors such as age and size. Most radiation dose estimates for pediatric nuclear medicine have not been based on administered activities of radiopharmaceuticals recommended by established practice guidelines. The dosage card of the European Association of Nuclear Medicine (EANM) and the North American consensus guidelines each provide recommendations of administered activities of radiopharmaceuticals in children, but there are substantial differences between these two guidelines. For 12 commonly performed pediatric nuclear medicine studies, two established pediatric radiopharmaceutical administration guidelines were used to calculate updated radiation dose estimates and to compare the radiation exposure resulting from the recommendations of each of the guidelines. Estimated radiation doses were calculated for 12 common procedures in pediatric nuclear medicine using administered activities recommended by the dosage card of the EANM (version 1.5.2008) and the 2010 North American consensus guidelines for radiopharmaceutical administered activities in pediatrics. Based on standard models and nominal age-based weights, radiation dose was estimated for typical patients at ages 1, 5, 10 and 15 years and adult. The resulting effective doses were compared, with differences greater than 20% considered significant. Following either the EANM dosage card or the 2010 North American guidelines, the highest effective doses occur with radiopharmaceuticals labeled with fluorine-18 and iodine-123. In 24% of cases, following the North American consensus guidelines would result in a substantially higher radiation dose. The guidelines of the EANM dosage card would lead to a substantially higher radiation dose in 39% of all cases, and in 62% of cases in which patients were age 5 years or younger. For 12 commonly performed pediatric nuclear medicine studies, updated radiation dose estimates can guide efforts to reduce radiation exposure and provide current information for discussing radiation exposure and risk with referring physicians, patients and families. There can be substantial differences in radiation exposure for the same procedure, depending upon which of these two guidelines is followed. This discordance identifies opportunities for harmonization of the guidelines, which may lead to further reduction in nuclear medicine radiation doses in children.

CTSim: An Interactive Computer Simulation to Learn the Fundamentals of CT Dose Optimization

Approximately 80 million CT examinations are performed annually in the United States, contributing over 50% of the population's exposure to ionizing radiation. The doses from these examinations are highly variable across institutions and higher than necessary for medical diagnosis [ 1 Miglioretti D.L. Johnson E. Williams A. et al. The use of computed tomography in pediatrics and the associated radiation exposure and estimated cancer risk. JAMA Pediatr. 2013; 167: 700-707 Crossref PubMed Scopus (900) Google Scholar ]. Because radiation is a known carcinogen, there are many efforts to reduce doses, as manifested by the Image Gently® campaign. A relatively modest CT dose reduction could result in a substantial improvement in radiation exposure and patient safety. Miglioretti et al estimated that if the highest quartile of radiation doses in children were reduced to the average level, the expected number of cancers could be reduced by over 44% [ 1 Miglioretti D.L. Johnson E. Williams A. et al. The use of computed tomography in pediatrics and the associated radiation exposure and estimated cancer risk. JAMA Pediatr. 2013; 167: 700-707 Crossref PubMed Scopus (900) Google Scholar ].

Practical Strategies to Reduce Pediatric CT Radiation Dose

The objective of this article is to provide a brief review of CT scanning radiation sensitivity in children and explain CT scan parameters that affect radiation dose. We discuss key factors influencing radiation dose and study quality and how these factors can be used to optimize scan protocols with the goal of reducing pediatric CT radiation dose without compromising diagnostic quality. Finally, we provide some practical tips for reducing radiation doses to children.

CT radiation dose in children: a survey to establish age-based diagnostic reference levels in MITERA hospital (a private Mediterranean hospital)

CT radiation dose in children: a survey to establish age-based diagnostic reference levels in MITERA hospital (a private Mediterranean hospital)

Preoperative evaluation of pediatric kidney stone prior to percutaneous nephrolithotomy: is computed tomography really necessary?

The objective of the study was to investigate the precise role of computed tomography (CT) in preoperative radiologic evaluation and surgical planning of kidney stone in children prior to percutaneous nephrolithotomy (PNL). A total of 113 pediatric patients (aged ≤18years) undergoing PNL for renal stone(s) in three referral hospitals between March 2010 and August 2012 were retrospectively evaluated. Depending on the preoperative radiologic evaluation, patients were divided into two groups. Those evaluated with CT were classified as group-1 (n=50) and the remaining cases undergoing intravenous urography (IVU) examination were classified as group-2 (n=63). Patient- and procedure-related variables and perioperative measures were compared between the groups. The mean age, stone size and localization were similar in both groups (p=0.07, p=0.57, p=0.6, respectively). Although the postoperative hemoglobin drop was found to be significantly higher in group-2 (1.5±1.3 vs. 0.9±0.6g/dL, p=0.005), the mean operation time, fluoroscopic screening time, access number, overall success and complication rates were comparable (p=0.06, p=0.94, p=0.75, p=041, and p=0.41, respectively). However, the mean hospitalization time was significantly prolonged in group-2 than in group-1 (p=0.03). Our findings clearly demonstrate that, despite the key role of preoperative CT in particular patients with anatomically abnormal kidneys, IVU is a valuable alternative imaging modality with comparable radiation doses in children.

Survey of pediatric MDCT radiation dose from university hospitals in Thailand: a preliminary for national dose survey

Increasing pediatric CT usage worldwide needs the optimization of CT protocol examination. Although there are previous published dose reference level (DRL) values, the local DRLs should be established to guide for clinical practice and monitor the CT radiation. To determine the multidetector CT (MDCT) radiation dose in children in three university hospitals in Thailand in four age groups using the CT dose index (CTDI) and dose length product (DLP). A retrospective review of CT dosimetry in pediatric patients (<15 years of age) who had undergone head, chest, and abdominal MDCT in three major university hospitals in Thailand was performed. Volume CTDI (CTDI(vol)) and DLP were recorded, categorized into four age groups: <1 year, 1-< 5 years, 5-<10 years, and 10-<15 years in each scanner. Range, mean, and third quartile values were compared with the national reference dose levels for CT in pediatric patients from the UK and Switzerland according to International Commission on Radiological Protection (ICRP) recommendation. Results Per age group, the third quartile values for brain, chest, and abdominal CTs were, respectively, in terms of CTDI(vol): 25, 30, 40, and 45 mGy; 4.5, 5.7, 10, and 15.6 mGy; 8.5, 9, 14, and 17 mGy; and in terms of DLP: 400, 570, 610, and 800 mGy cm; 80, 140, 305, and 470 mGy cm; and 190, 275, 560,765 mGy cm. This preliminary national dose survey for pediatric CT in Thailand found that the majority of CTDI(vol) and DLP values in brain, chest, and abdominal CTs were still below the diagnostic reference levels (DRLs) from the UK and Switzerland regarding to ICRP recommendation.

Falling prey to the sunk cost bias: a potential harm of patient radiation dose histories.

Although patient dose histories will make valuable contributions to quality improvement and research initiatives, care must be taken to avoid misuse by physicians when making imaging decisions for individual patients.

Getting it right: are regulation and registries for CT radiation dose in children the answer?

Recently, the state of California enacted a law requiring radiologists to record the radiation dose that each patient receives for a CT scan. Failure to do so is penalized by law. This law becomes effective in July 2012. By July 2013, every facility that performs CT scans must become accredited by one of three professional groups. This report discusses the role that legislation is playing in the practice of medicine in regard to CT practice. Inherent in this discussion is the assumption that pediatric radiologists know the right dose that a child should receive for a specific clinical indication. But do we really know the answer to this? Compared to the European radiology community, the United States radiology community lags in this regard. This paper defines diagnostic reference levels (DRL) and reviews the history of DRL in the United States compared to that in the European community and the progress by the American College of Radiology's National Radiology Data Registry (NRDR) to establish national registries. The establishment of the first pediatric Quality Improvement Registry in CT Scans in Children (QuIRCC) and its progress to date will be discussed.

Global Quality Imaging: Improvement Actions

Workforce shortage, workload increase, workplace changes, and budget challenges are emerging issues around the world, which could place quality imaging at risk. It is important for imaging stakeholders to collaborate, ensure patient safety, improve the quality of care, and address these issues. There is no single panacea. A range of improvement measures, strategies, and actions are required. Examples of improvement actions supporting the 3 quality measures are described under 5 strategies: conducting research, promoting awareness, providing education and training, strengthening infrastructure, and implementing policies. The challenge is to develop long-term, cost-effective, system-based improvement actions that will bring better outcomes and underpin a sustainable future for quality imaging. In an imaging practice, these actions will result in selecting the right procedure (justification), using the right dose (optimization), and preventing errors along the patient journey. To realize this vision and implement these improvement actions, a range of expertise and adequate resources are required. Stakeholders should collaborate and work together. In today's globalized environment, collaboration is strength and provides synergy to achieve better outcomes and greater success.

Follow-up skeletal surveys for nonaccidental trauma: can a more limited survey be performed?

Studies have demonstrated the value of the follow-up skeletal survey in identifying additional fractures, clarifying indeterminate findings, and improving dating of skeletal injuries in victims of physical abuse. To determine whether a more limited follow-up survey could yield the same radiologic data as a full follow-up survey. The study cohort comprised 101 children who had follow-up surveys that met our inclusion criteria. Consensus readings of both original and follow-up surveys were performed by two pediatric radiologists. These results were compared to determine additional findings from the follow-up surveys. Limited skeletal survey protocols were evaluated to determine whether they would detect the same fractures seen with a complete osseous survey. In the 101 children 244 fractures were identified on the initial osseous survey. Follow-up surveys demonstrated new information in 38 children (37.6%). A 15-view limited follow-up survey identified all additional information seen on the complete follow-up survey. Our data demonstrate that a 15-view limited follow-up skeletal survey could be performed without missing clinically significant new fractures and still allow proper identification of confirmed fractures or normal findings. A limited survey would decrease radiation dose in children.

CT radiation dose in children: a survey to establish age-based diagnostic reference levels in Switzerland

This work aimed at assessing the doses delivered in Switzerland to paediatric patients during computed tomography (CT) examinations of the brain, chest and abdomen, and at establishing diagnostic reference levels (DRLs) for various age groups. Forms were sent to the ten centres performing CT on children, addressing the demographics, the indication and the scanning parameters: number of series, kilovoltage, tube current, rotation time, reconstruction slice thickness and pitch, volume CT dose index (CTDI(vol)) and dose length product (DLP). Per age group, the proposed DRLs for brain, chest and abdomen are, respectively, in terms of CTDI(vol): 20, 30, 40, 60 mGy; 5, 8, 10, 12 mGy; 7, 9, 13, 16 mGy; and in terms of DLP: 270, 420, 560, 1,000 mGy cm; 110, 200, 220, 460 mGy cm; 130, 300, 380, 500 mGy cm. An optimisation process should be initiated to reduce the spread in dose recorded in this study. A major element of this process should be the use of DRLs.

Paediatric CT: the effects of increasing image noise on pulmonary nodule detection

A radiation dose of any magnitude can produce a detrimental effect manifesting as an increased risk of cancer. Cancer development may be delayed for many years following radiation exposure. Minimizing radiation dose in children is particularly important. However, reducing the dose can reduce image quality and may, therefore, hinder lesion detection. We investigated the effects of reducing the image signal-to-noise ratio (SNR) on CT lung nodule detection for a range of nodule sizes. A simulated nodule was placed at the periphery of the lung on an axial CT slice using image editing software. Multiple copies of the manipulated image were saved with various levels of superimposed noise. The image creation process was repeated for a range of nodule sizes. For a given nodule size, output images were read independently by four Fellows of The Royal College of Radiologists. The overall sensitivities in detecting nodules for the SNR ranges 0.8-0.99, 1-1.49, and 1.5-2.35 were 40.5%, 77.3% and 90.3%, respectively, and the specificities were 47.9%, 73.3% and 75%, respectively. The sensitivity for detecting lung nodules increased with nodule size and increasing SNR. There was 100% sensitivity for the detection of nodules of 4-10 mm in diameter at SNRs greater than 1.5. Reducing medical radiation doses in children is of paramount importance. For chest CT examinations this may be counterbalanced by reduced sensitivity and specificity combined with an increased uncertainty of pulmonary nodule detection. This study demonstrates that pulmonary nodules of 4 mm and greater in diameter can be detected with 100% sensitivity provided that the perceived image SNR is greater than 1.5.