S. Bruce Greenberg

Pediatric Chest MDCT Using Tube Current Modulation: Effect on Radiation Dose with Breast Shielding

OBJECTIVE The purpose of our study was to assess the effect on radiation dose and image noise during pediatric chest 16-MDCT using automatic tube current modulation and bismuth breast shields. MATERIALS AND METHODS Age-based chest 16-MDCT was performed on an anthropomorphic phantom representing a 5-year-old child. Two scans were obtained in each of four sequences: first, without a shield; second, with a 2-ply bismuth shield; third, using automatic tube current modulation with a scout image obtained after placement of the shield; and fourth, using automatic tube current modulation with a scout image obtained before placement of the shield. Metal oxide semiconductor field effect transistor technology was used to measure the radiation dose in 20 organ locations. Effective dose was estimated using the console dose-length product. Noise was measured by recording the SD of Hounsfield units in identical regions of interest. RESULTS The bismuth breast shield reduced the dose to the breast by 26%. Shielding and automatic tube current modulation reduced the breast dose by 52%. Multiple organ doses were lowest when the shield was placed after the scout radiograph had been obtained. When the shield was placed after the scout image was obtained, the mean noise in the range of shielding increased from 11.4 to 13.1 H (superior mediastinum) and from 10.0 to 12.8 H (heart) (p < 0.01). Increased noise, however, was near the target noise index (measured in SD of Hounsfield units) of 12.0 H (SD). Using automatic tube current modulation, the effective dose was reduced by 35% when the shield was placed after the scout and by 20% when the shield was present in the scout. CONCLUSION The greatest dose reduction is achieved by placing the shield after obtaining the scout image to avoid Auto mA compensation due to density of shield. With this technique, image noise increased but remained close to the target noise index.

All-terrain vehicle injuries in children: injury patterns and prognostic implications

BackgroundAll-terrain vehicle (ATV) accidents are common in children. Our purpose was to identify imaging patterns associated with ATV injuries in children.Patients and methodsThe study group comprised 141 consecutive children admitted to a tertiary pediatric hospital following ATV accidents. Medical records were evaluated for demographics and patient outcome. All imaging studies were reviewed and abnormalities cataloged.ResultsExtremity fractures were the most common injuries in our study, occurring in 38% of patients. Lower extremity fractures were more common than upper extremity fractures. Partial foot amputation, an unusual injury, was present in three children. Torso injuries were present in 22% of the children. Pulmonary contusions, but not abdominal injuries, were significantly associated with long-term disability or death (p=0.01). Brain injuries occurred in 19% of the children and were significantly associated with death or long-term disability (p=<0.001). No association of brain injury and skull fracture was present.ConclusionsA wide variety of injuries were identified in children with ATV accidents. Partial foot amputation, an unusual injury, was identified in three children. Brain injuries and lung contusions detected by computed tomography were associated with long-term disability and death. Radiologists need to be aware of injuries associated with ATV accidents.

MR imaging and CT evaluation of congenital pulmonary vein abnormalities in neonates and infants.

Magnetic resonance (MR) imaging and computed tomography (CT) are increasingly being used in diagnosis and follow-up of congenital pulmonary vein anomalies in neonates and infants. Such anomalies include total or partial anomalous pulmonary venous return, sinus venosus defect, malposition of the septum primum, cor triatriatum, pulmonary vein atresia or stenosis, and abnormal number or course of the pulmonary veins. MR imaging provides a wealth of anatomic and functional data that are valuable in case management and planning intervention. Gadolinium-enhanced MR angiography is the mainstay of anatomic evaluation. Ventricular volumetry with two-dimensional steady-state free-precession sequences and flow analysis with cine phase-contrast imaging provide physiologic information that may be used to calculate the degree of right heart enlargement and the shunt fraction, allowing the cardiologist to determine the functional importance of the lesion. CT provides superior spatial resolution and short imaging times but at the expense of exposure to ionizing radiation.

Limitations of Standard Echocardiographic Methods for Quantification of Right Ventricular Size and Function in Children and Young Adults

The aim of this study was to evaluate correlation of 2‐dimensional (2D) echocardiographic assessment of right ventricular (RV) and left ventricular (LV) size and function with magnetic resonance imaging (MRI) in children and young adults.

Multidetector computed tomography of pediatric large airway diseases: state-of-the-art.

Advances in multidetector computed tomography (MDCT) technology have given rise to improvements in the noninvasive and comprehensive assessment of the large airways in pediatric patients. Superb two-dimensional and three-dimensional reconstruction MDCT images have revolutionized the display of large airways and enhanced the ability to diagnose large airway diseases in children. The 320-MDCT scanner, which provides combined detailed anatomic and dynamic functional information assessment of the large airways, is promising for the assessment of dynamic large airway disease such as tracheobronchomalacia. This article discusses imaging techniques and clinical applications of MDCT for assessing large airway diseases in pediatric patients.

ACR Appropriateness Criteria® Acute Nonspecific Chest Pain—Low Probability of Coronary Artery Disease

Primary imaging options in patients at low risk for coronary artery disease (CAD) who present with undifferentiated chest pain and without signs of ischemia are functional testing with exercise or pharmacologic stress-based electrocardiography, echocardiography, or myocardial perfusion imaging to exclude myocardial ischemia after rule-out of myocardial infarction and early cardiac CT because of its high negative predictive value to exclude CAD. Although possible, is not conclusive whether triple-rule-out CT (CAD, pulmonary embolism, and aortic dissection) might improve the efficiency of patient management. More advanced noninvasive tests such as cardiac MRI and invasive imaging with transesophageal echocardiography or coronary angiography are rarely indicated. With increased likelihood of noncardiac causes, a number of diagnostic tests, among them ultrasound of the abdomen, MR angiography of the aorta with or without contrast, x-ray rib views, x-ray barium swallow, and upper gastrointestinal series, can also be appropriate. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment. This recommendation is based on excellent evidence, including several randomized comparative effectiveness trials and blinded observational cohort studies.

Rebalancing the risks of Computed Tomography and Magnetic Resonance imaging

The concern for fatal cancers caused by ionizing radiation exposure associated with the increased use of CT in children is well documented. Inappropriate adult CT techniques applied to children can result in excessive radiation exposure [1], exposures similar to the dose received by a group of nuclear bomb survivors who later developed an increased cancer rate [2, 3]. CT examinations are projected by some to eventually account for up to 1.5–2.0% of future cancers in the United States [4]. Although only 7% of CT scans are in children, they are expected to account for up to 15% of the additional cancers because of increased life expectancy and sensitivity of children to radiation. Risk estimates for excess cancer mortality from radiation exposure of 1 death per 2,000 scans assume an effective dose of 10 mSv per scan and a risk of 5% per sievert [4]. MRI by contrast is perceived as a panacea for many applications performed by CT because it uses no ionizing radiation. General anesthesia risks associated with performing MRI in children need to be compared to the risk of ionizing radiation associated with CT. General anesthesia presents both acute and long-term risks to children undergoing MRI. The death rate for patients undergoing general anesthesia for MRI is cited to be 5.3 deaths per million [5]. Greater anesthesia risk for children undergoing an MRI examination is recognized [6, 7]. One study found that the mortality rate for general

Primary Translocation of Aberrant Left Subclavian Artery for Children With Symptomatic Vascular Ring

BACKGROUND The standard operation for vascular ring with right aortic arch and aberrant left subclavian artery is ligamentum arteriosum division. A new surgical approach with primary translocation of the aberrant left subclavian artery to the left carotid artery, removal of the Kommerell diverticulum, and division of the ligamentum through left thoracotomy was recently applied. This study assessed the early outcomes of this approach. METHODS This is a retrospective review of all patients having an operation for right aortic arch with aberrant left subclavian artery and the Kommerell diverticulum between January 2001 and April 2011 at a single institution. RESULTS Eight patients had a division of the ligamentum and 10 had a primary translocation of an aberrant left subclavian artery with diverticulum removal and ligamentum division. The median operative age and weight for each surgical technique group were, respectively, 2.2 and 1.8 years (p = 0.56) and 10.7 and 12.6 kg (p = 0.30). All patients were symptomatic preoperatively. No deaths occurred. One patient from each group had chylous effusion that was medically treated. The median hospital stay for each group was 4 and 5 days (p = 0.45). During the median follow-up of 47 months, 3 patients in the division of ligamentum group required albuterol aerosol or oral antiinflammatory medication for respiratory symptoms. All patients in the primary translocation group remained asymptomatic and required no medication (p = 0.069). CONCLUSIONS Primary translocation of aberrant left subclavian artery with removal of the diverticulum and division of the ligamentum had excellent early outcomes and can potentially eliminate residual symptoms and late complications.

Radiation Safety in Children with Congenital and Acquired Heart Disease: A Scientific Position Statement on Multimodality Dose Optimization from the Image Gently Alliance

There is a need for consensus recommendations for ionizing radiation dose optimization during multimodality medical imaging in children with congenital and acquired heart disease (CAHD). These children often have complex diseases and may be exposed to a relatively high cumulative burden of ionizing radiation from medical imaging procedures, including cardiac computed tomography, nuclear cardiology studies, and fluoroscopically guided diagnostic and interventional catheterization and electrophysiology procedures. Although these imaging procedures are all essential to the care of children with CAHD and have contributed to meaningfully improved outcomes in these patients, exposure to ionizing radiation is associated with potential risks, including an increased lifetime attributable risk of cancer. The goal of these recommendations is to encourage informed imaging to achieve appropriate study quality at the lowest achievable dose. Other strategies to improve care include a patient-centered approach to imaging, emphasizing education and informed decision making and programmatic approaches to ensure appropriate dose monitoring. Looking ahead, there is a need for standardization of dose metrics across imaging modalities, so as to encourage comparative effectiveness studies across the spectrum of CAHD in children.

Dynamic Pulmonary CT of Children

OBJECTIVE Wide-detector CT allows simultaneous imaging of the entire airway and lungs in small children. Images acquired in multiple phases by continuous scanning during respiration are viewed dynamically, allowing more complete airway and pulmonary evaluation than possible with static protocols. The purpose of this study was to evaluate whether low-dose techniques can be applied to dynamic pulmonary CT of small children. MATERIALS AND METHODS The study included 24 infants and small children with persistent respiratory difficulty who underwent dynamic pulmonary CT (11 with IV contrast administration, 13 without contrast administration). No significant difference in patient age was present in the two groups. Continuous-mode wide-detector scans were obtained at 350-millisecond gantry rotation for a total of 1.4 seconds at 80 kVp. Some contrast-enhanced studies for simultaneous vascular and airway evaluation were performed at slightly greater tube current. The effective dose for each patient was calculated, and the Student t test was performed to compare effective dose measurements. RESULTS All studies were of diagnostic quality, frequently yielding critical information not available with other diagnostic tests. The mean effective dose for all patients was 1.7 (SD, 1.1) mSv. In the group who received contrast material, the mean effective dose was greater (1.9 [SD, 1.4] mSv) than in the group who did not receive contrast material (1.5 [SD, 0.7] mSv), but the difference was not significant (p = 0.4). CONCLUSION Wide-detector dynamic CT is ideal for evaluation of the airway and lungs in infants and small children with persistent respiratory distress. Effective doses are low, typically less than 2 mSv.