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Dual-energy CT enables the simultaneous acquisition of CT images at two different x-ray energy spectra. By acquiring high- and low-energy spectral data, dual-energy CT can provide unique qualitative and quantitative information about tissue composition, allowing differentiation of multiple materials including iodinated contrast agents. The two dual-energy CT postprocessing techniques that best exploit the advantages of dual-energy CT in children are the material-decomposition images (which include virtual nonenhanced, iodine, perfused lung blood volume, lung vessel, automated bone removal, and renal stone characterization images) and virtual monoenergetic images. Clinical applications include assessment of the arterial system, lung perfusion, neoplasm, bowel diseases, renal calculi, tumor response to treatment, and metal implants. Of importance, the radiation exposure level of dual-energy CT is equivalent to or less than that of conventional single-energy CT. In this review, the authors discuss the basic principles of the dual-energy CT technologies and postprocessing techniques and review current clinical applications in the pediatric chest and abdomen.

Technical advances in CT have enabled implementation of dual-energy CT into routine clinical practice. By acquiring images at two different energy spectra, dual-energy CT enables material decomposition, allowing generation of material- and energy-specific images. Material-specific images include virtual nonenhanced images and iodine-specific images (iodine maps). Energy-specific images include virtual monoenergetic images. The reconstructed images can provide unique qualitative and quantitative information about tissue composition and contrast media distribution. In thoracic oncologic imaging, dual-energy CT provides advantages in characterization of thoracic malignancies and lung nodules, determination of extent of disease, and assessment of response to therapy. An especially important feature in children is that dual-energy CT does not come at a higher radiation exposure. Keywords: CT, CT-Quantitative, Lung, Mediastinum, Neoplasms-Primary, Pediatrics, Thorax, Treatment Effects © RSNA, 2021

To compare whole-body magnetic resonance (MR) imaging with conventional imaging for detection of distant metastases in pediatric patients with common malignant tumors.This institutional review board-approved, HIPAA-compliant, multicenter prospective cohort study included 188 patients (109 male, 79 female; mean age, 10.2 years; range,1 to 21 years) with newly diagnosed lymphoma, neuroblastoma, or soft-tissue sarcoma. Informed consent was obtained and all patients underwent noncontrast material-enhanced whole-body MR imaging and standard-practice conventional imaging. All images were reviewed centrally by 10 pairs of readers. An independent panel verified the presence or absence of distant metastases. Detection of metastasis with whole-body MR and conventional imaging was quantified by using the area under the receiver operating characteristic curve (AUC). The effects of tumor subtype, patient age, and distant skeletal and pulmonary disease on diagnostic accuracy were also analyzed.Of the 134 eligible patients, 66 (33 positive and 33 negative for metastasis) were selected for image review and analysis. Whole-body MR imaging did not meet the noninferiority criterion for accuracy when compared with conventional imaging for detection of metastasis (difference between average AUCs was -0.03 [95% confidence interval: -0.10, 0.04]); however, the average AUC for solid tumors was significantly higher than that for lymphomas (P = .006). More skeletal metastases were detected by using whole-body MR imaging than by using conventional imaging (P = .03), but fewer lung metastases were detected (P.001). Patient age did not affect accuracy.The noninferior accuracy for diagnosis of distant metastasis in patients with common pediatric tumors was not established for the use of whole-body MR imaging compared with conventional methods. However, improved accuracy was seen with whole-body MR imaging in patients with nonlymphomatous tumors.

The National Lung Screening Trial (NLST) is a randomized multicenter study comparing low-dose helical computed tomography (CT) with chest radiography in the screening of older current and former heavy smokers for early detection of lung cancer, which is the leading cause of cancer-related death in the United States. Five-year survival rates approach 70% with surgical resection of stage IA disease; however, more than 75% of individuals have incurable locally advanced or metastatic disease, the latter having a 5-year survival of less than 5%. It is plausible that treatment should be more effective and the likelihood of death decreased if asymptomatic lung cancer is detected through screening early enough in its preclinical phase. For these reasons, there is intense interest and intuitive appeal in lung cancer screening with low-dose CT. The use of survival as the determinant of screening effectiveness is, however, confounded by the well-described biases of lead time, length, and overdiagnosis. Despite previous attempts, no test has been shown to reduce lung cancer mortality, an endpoint that circumvents screening biases and provides a definitive measure of benefit when assessed in a randomized controlled trial that enables comparison of mortality rates between screened individuals and a control group that does not undergo the screening intervention of interest. The NLST is such a trial. The rationale for and design of the NLST are presented.

Tumors of the renal medulla cover a wide spectrum, with characteristic histomorphology and variable biologic profiles. Renal medullary tumors can be categorized into benign and malignant neoplasms based on histologic features and clinico-biologic behavior. They can be further classified into pediatric and adult tumors based on the patient age group. When small, renal medullary tumors may be differentiated from the more common renal adenocarcinomas by their central location and certain demographic characteristics. Although most large malignant medullary tumors demonstrate imaging findings that are indistinguishable from those of other renal malignancies, some tumors demonstrate imaging findings that may suggest a specific diagnosis.

To evaluate effects of varying tube current and voltage on radiation dose, image noise, and image contrast with different phantom sizes and shapes.Four round lucite phantoms with 8-32-cm diameters were scanned with multi-detector row computed tomography (CT) and 80-120 kVp. Radiation dose was based on CT dose index, image noise, and iodine contrast and measured with constant and variable tube currents that were age appropriate for each tube voltage. Radiation dose and image noise and contrast were compared in round and oval 24-cm phantoms. For various combinations of technical factors and phantom sizes and shapes, percentage differences were calculated for radiation dose and image noise and contrast. Associations between tube voltage and radiation dose, image noise, and image contrast in round and oval phantoms were determined by fitting second-degree polynomials to data. Differences in radiation dose and image noise and contrast, which were attributable to differences in tube voltage, were tested with paired t tests.With 165-mAs tube current, radiation doses with 140- and 80-kVp tube voltages were 103% ([41.9 mGy - 20.6 mGy]/20.6 mGy) and 58% ([10.2 mGy - 4.2 mGy]/10.1 mGy) higher in the 8-cm phantom than in the 32-cm phantom. When tube current was adapted for phantom size, radiation dose at 80 kVp in the 8-cm phantom was reduced by 82% ([10.1 mGy - 1.8 mGy]/10.1 mGy). In the 8-cm phantom, tube voltage was decreased from 120 to 80 kVp and tube current remained at 165 mAs, resulting in a 68% noise increase ([3.1 HU - 1.8 HU]/1.8 HU). With variable tube current, 80-kVp tube voltage in the 8-cm phantom led to a 138% noise increase ([7.3 HU - 3.1 HU]/3.1 HU). With reduced tube voltage, image contrast increased. In the 8-cm phantom, with a constant 165-mAs tube current and a decrease in tube voltage from 120 to 80 kVp, there was a 35% ([333 HU - 217 HU]/333 HU) increase in contrast. No difference was noted in radiation dose or noise between round and oval phantoms (P = .604 and P = .06, respectively), but a small statistically significant difference (1%) in contrast attenuation was demonstrated (P = .025).Reduced tube voltage for pediatric contrast material-enhanced CT reduces radiation dose and maintains image contrast. Image noise increases, but the effect is minimal in smaller phantoms. An additional reduction in tube current further reduces radiation dose.

To describe the chest radiographic appearance of the Amplatzer septal occluder (ASO) (AGA Medical Corporation, Golden Valley, Minn) for atrial septal defects (ASDs) in pediatric patients.Two radiologists independently reviewed frontal and lateral chest radiographs obtained in young patients 24 hours after transcatheter ASD closure with the ASO. The appearance (flat disks or dots) and location of the ASO were recorded. The location was related to that of a thoracic vertebral body on frontal and lateral chest radiographs and to a line drawn between the anterior margin of the right hilum and the posterior margin of the inferior vena cava (hilar-caval line) on lateral radiographs; this line corresponded to the expected position of the interatrial septum. The relationship between ASO appearance and patient age was assessed with logistic regression and cumulative probability plots.Sixty-eight pediatric patients (age range, 1 month to 18 years; mean age, 4.2 years; 24 boys and 44 girls) were included. On frontal radiographs, the ASO center projected between T7 and T9, either to the right of or over the spinous processes of the vertebral body. On lateral radiographs, the ASO projected over (n = 66) or anterior to (n = 2) the hilar-caval line. On frontal radiographs, it appeared as one or two flat disks (n = 61) or as two metallic dots (n = 7). On lateral radiographs, it appeared as two flat disks (n = 54) or as two metallic dots (n = 14). The relationship between increasing patient age and the metallic dot appearance on frontal and lateral radiographs and on the combination of frontal and lateral radiographs was highly significant in each case (P.001, likelihood ratio chi(2) test), with r(2) values of 0.35, 0.20, and 0.28, respectively. ASDs were successfully occluded with the ASO in all patients except one, in whom trivial shunting was seen at 12-month follow-up.The ASO in pediatric patients has a characteristic radiographic appearance when properly positioned.

Multi-detector row computed tomography (CT) has changed the approach to imaging of thoracic anatomy and disease in the pediatric population. At the author's institution, multi-detector row CT with multiplanar and three-dimensional reconstruction has become an important examination in the evaluation of systemic and pulmonary vasculature and the tracheobronchial tree. In some clinical situations, multi-detector row CT with reformatted images is obviating conventional angiography, which is associated with higher radiation doses and longer sedation times. Although multi-detector row CT with multiplanar and three-dimensional reconstruction is expanding the applications of CT of the thorax, its role as a diagnostic tool still needs to be better defined. The purposes of this article are to describe how to perform multi-detector row CT with multiplanar and three-dimensional reconstruction in young patients, to discuss various reconstruction techniques available, and to discuss applications in the evaluation of vascular and airways diseases.

To compare the accuracies of computed tomography (CT), magnetic resonance (MR) imaging, and bone scintigraphy in staging disease in patients with neuroblastoma.Ninety-six children with newly diagnosed neuroblastoma were enrolled in a multicenter prospective cohort study. CT, MR, and bone scintigraphy were used to evaluate tumor stage. Sensitivity and specificity values and receiver operating characteristic (ROC) curve analyses were used to compare the accuracy of CT, MR, and scintigraphy for tumor staging.Eighty-eight patients were eligible for staging analysis, and 45 patients who underwent surgery at initial diagnosis were eligible for analysis of local tumor extent. CT and MR had sensitivities of 43% and 83%, respectively (P.01), and specificities of 97% and 88%, respectively (P.05), for detection of stage 4 disease. Areas under the ROC curves for CT and MR were 0.81 and 0.85, respectively (P =.06); that for scintigraphy was 0.83. Addition of scintigraphy to both CT and MR increased the areas under the ROC curves to 0.90 and 0.88, respectively. Accuracy of CT and MR for staging disease confined to the chest or abdomen (stages 1, 2, and 3) was poor.MR alone and CT and MR combined with bone scintigraphy enable the accurate detection of stage 4 disease. Both CT and MR perform poorly for local tumor staging.

Posttransplantation lymphoproliferative disorder (PTLD) is a condition in patients who receive transplants in which chronic immunosuppression leads to an unregulated expansion of lymphoid cells; the condition ranges from hyperplasia to malignant lymphoid proliferation. Risk factors affecting the incidence of PTLD include allograft type, Epstein-Barr virus infection, and immunosuppression. In this article, we review the clinical, histopathologic, and imaging features of PTLD in children. Because PTLD can affect nearly any organ system, a wide variety of clinical manifestations is possible. The heterogeneous nature of the disease is also reflected on imaging studies. The goals of imaging in patients with PTLD are to detect disease, guide biopsy, and direct appropriate follow-up imaging rather than to establish a specific diagnosis. Because the clinical and imaging manifestations of PTLD are nonspecific and are not reliably predictive of histopathologic subtype, tissue biopsy is necessary for final diagnosis.

To study the appearance and distribution of posttransplantation lymphoproliferative disorder (PTLD) at abdominal computed tomography (CT).The authors retrospectively analyzed pretreatment abdominal CT scans in 51 patients (mean age, 36 years) with PTLD after solid organ transplantation. All diagnoses were proved at either abdominal (n = 26) or extraabdominal (n = 25) pathologic examination. Presence or absence of abdominal involvement, appearance and distribution of disease, and association with abdominal symptoms were all analyzed.CT scans were abnormal in 36 of the 51 patients (71%). Fifteen patients (29%) had no CT, clinical, or pathologic evidence of abdominal involvement. Of the 36 patients with abdominal PTLD at CT, 22% had lymph node enlargement, 28% splenic involvement, and 81% extranodal or extrasplenic involvement. Extranodal abdominal sites included liver (53%), small bowel (25%), kidney (17%), mesentery (14%), adrenal gland (8%), abdominal wall (8%), colon (6%), stomach (3%), and gallbladder (3%). Frequency of abdominal involvement was greater for heart and liver transplant recipients (94%) than for lung and kidney transplant recipients (58%) (P.01). Seventeen of 36 patients (47%) with abdominal PTLD had no evidence of extraabdominal disease.Extranodal involvement is more common than splenic or nodal involvement in patients with abdominal PTLD. The presence of such findings in a patient after transplantation strongly suggests the diagnosis of PTLD and warrants aggressive evaluation.

To evaluate flow velocity measurements in the middle cerebral artery (MCA) and/or neurologic examination for detection of cerebral infarction in sickle cell disease (SCD).Twenty-four pediatric patients aged 6 1/2-17 years with SCD underwent magnetic resonance (MR) imaging, MR angiography, neurologic examination, and transcranial Doppler ultrasonography (US). Transcranial Doppler studies were evaluated for maximum flow velocity in the right and left MCAs. Combinations of cut-off values were used to determine the sensitivity and specificity of transcranial Doppler US for detection of infarction.Neurologic examination had 58% sensitivity and 92% specificity for cerebral infarction. Maximal flow velocity200 cm/sec or100 cm/sec (including no flow) helped identify nine of 12 patients with infarcts proved at MR imaging, with only one false-positive result (sensitivity, 75%; specificity 92%). The combination of neurologic examination and transcranial Doppler US produced 92% sensitivity and 83% specificity for cerebral infarction.The combination of transcranial Doppler US and neurologic examination has potential as a screening technique for infarction in SCD.

Screening, defined as the testing of asymptomatic individuals for subclinical disease, has become a major strategy in improving patient outcome through the early detection of cancer. The purpose of screening is to differentiate among those individuals who likely have cancer from those who do not. The premise of screening is that early diagnosis will yield positive health benefits by permitting early initiation of treatment and thus a reduction in morbidity and mortality (1‐3). Screening tests differ from diagnostic tests. Diagnostic tests are generally used in patients who come to medical evaluation for symptoms. Results of diagnostic tests are often accurate enough to establish a definite diagnosis, and they can be used as a basis for initiating treatment. By comparison, screening tests are generally offered to asymptomatic populations as a means of determining whether it is probable that they have a target disease. During the past few years, many institutions have established targeted screening programs for pulmonary cancer and colorectal adenomatous polyps and also whole-body screening programs that use both single-detector and multidetector computed tomography (CT). The Radiological Society of North America recognized the importance of screening tests for cancer and dedicated an afternoon session to this topic at the 2001 annual meeting. The following two articles by Yee and Brant-Zawadzki discuss the role for virtual colonography and whole-body CT in the detection of cancer. Because screening programs for cancer detection are increasing in the United States, we believe that publication of these presentations is appropriate. Radiologists will be asked to make decisions about offering screening tests in their own practices, and thus, they must be aware of the risk/benefit and cost/benefit ratios of screening imaging procedures. These introductory comments, which emphasize the general criteria for a good screening program and the clinical and financial implications of offering CT screening directly to the consumer, provide a foundation for the articles that follow.

Upholding a long-standing tradition of the annual meeting of the Radiological Society of North America, we have assembled a group of five experts and provided each with two interesting unknown cases for review and discussion. The radiologists represent the major subspecialty areas of pediatric, thoracic, neurologic, abdominal, and musculoskeletal imaging. The unknown cases were chosen from recent clinical cases seen at the Mount Sinai Medical Center and were kindly provided, analyzed, and assembled by some of the Sinai faculty: Karen I. Norton, David S. Mendelson, Bradley N. Delman, Robert S. Shapiro, and Thomas P. Naidich. This session has traditionally provided an opportunity for the audience to test its diagnostic acumen in a light-hearted atmosphere conducive to relaxed learning. The panelists were chosen not only for their exceptional knowledge but also because they are “good sports,” willing to expose their analytic skills to a “standing room only” crowd of radiologists in the Arie Crown Theater at ...

Circular esophageal myotomy of the upper pouch in infants with esophageal atresia is an effective means of reducing anastomotic tension. This report describes two patients who developed marked postoperative dilatation of the proximal esophagus at the myotomy site. On radiographs, the dilated, air-filled esophagus simulated a pneumomediastinum or intrathoracic cyst-like structure.

Three cases of premature infants with obstruction of the ileum and proximal colon in the absence of cystic fibrosis are presented. Meconium inspissation complicated low-grade bowel obstruction in 2 infants. In the third, the bowel was anatomically normal, with the tenacious meconium the apparent primary cause of obstruction. Distinguishing features of this unusual type of blockage and other meconium syndromes are also discussed. This condition may simulate necrotizing enterocolitis, requiring surgery for differentiation. It should be considered in the differential diagnosis of low small bowel or colonic obstruction in the premature infant who is several days of age.

Calyceal diverticulum is a relatively rare lesion that is usually asymptomatic but can assume clinical significance if drainage is impaired. Three patients are presented with unusual complications directly referable to a calyceal diverticulum. One child had a mobile calculus. In 2 others, intrarenal inflammatory masses developed in the area previously occupied by a calyceal diverticulum. One of these children had proved xanthogranulomatous pyelonephritis, and the other had an infected diverticulum.

The results of cranial ultrasonography in 32 term infants who had hypoxic-ischemic encephalopathy (HIE) and in 26 control infants were reviewed. Small or nonvisualized ventricles were present in 94% of the patients with HIE and in 62% of the control subjects. In 20 of the 32 patients (63%) with HIE, ultrasound demonstrated parenchymal abnormalities; the most common finding was periventricular hyperechogenicity (12/32 patients). There was a single false positive result in the control group. Fifty per cent of patients with HIE who had abnormalities demonstrated on ultrasonograms died (within 15 days of birth), whereas none of the infants who had normal ultrasound findings died. Moreover, 80% of surviving patients who had abnormal ultrasound findings had residual neurological deficits versus only 11% of those with normal ultrasound findings. Our results indicate that ultrasound is effective in detecting parenchymal changes in patients with HIE, parenchymal echoes are a more reliable sign of HIE than ventricular size, and the finding of parenchymal lesions on ultrasound scans appears to be predictive of abnormal motor development.

The clinical and radiographic features of paranasal sinus mucoceles in 6 pediatric patients are discussed. These lesions may be associated with clinical signs of a periorbital or intracranial mass. Characteristic radiographic findings can suggest the preoperative diagnosis, although a sphenoid sinus mucocele may simulate more serious conditions.

Magnetic resonance (MR) imaging was compared with computed tomography (CT) in 13 children with mediastinal abnormalities. CT and MR provided comparable information regarding the presence and size of the mediastinal lesions. The MR imaging technique that was most reliable in detecting a mass was a T1-weighted spin-echo pulse sequence. MR better discriminated mediastinal masses and enlarged nodes from vascular structures and was more sensitive than CT in detecting intraspinal extension. However, CT demonstrated calcification and bronchial abnormalities not seen on MR images. It is concluded that MR may be more helpful than CT in evaluating posterior mediastinal tumors, since there is a likelihood of intraspinal extension. In other cases, however, CT continues to be the procedure of choice to supplement plain radiography in children with suspected mediastinal neoplasms.

The authors reviewed 49 double-contrast and 27 single-contrast barium-enema examinations (BE) in 71 children with suspected inflammatory bowel disease. The diagnosis was proved in 41 patients, of whom 36 underwent proctoscopy and 5 had advanced disease which was treated surgically within 3 to 30 days after BE; the other 30 children served as controls. BE and proctoscopy were compared with regard to sensitivity (detection of disease) and accuracy (categorization as ulcerative or granulomatous colitis). Sensitivity was 93% for double-contrast and 82% for single-contrast BE. Both detected all cases of advanced disease; in early disease, double-contrast BE detected 91% of cases and single-contrast BE 70%. Colitis was correctly categorized as ulcerative or granulomatous in 93% with double-contrast BE and 86% with single-contrast BE. Specificity within the control group was 100% with both techniques. The authors conclude that both types of BE exhibit similar sensitivity in advanced disease, but the double-contrast technique is more accurate in detecting early disease.

Case material was reviewed to determine the value of the rectosigmoid index in the diagnosis of both segmental and total-colon aganglionosis in infants less than one month old. Data indicate that a rectosigmoid index higher than 0.9 may rule out a diagnosis of rectosigmoid aganglionosis but may be a misleading indicator of longer segment or total-colon aganglionosis.

Pleural disease is an unusual manifestation of childhood leukemia. Three cases are presented which illustrate a definite association between leukemia and pleural thickening. In two patients, there was bilateral diffuse pleural thickening and, in the other, there were unilateral pleural-based masses. Pleural disease may be the initial or only thoracic manifestation of leukemia, or it may occur in combination with other intrathoracic evidence of leukemia.

Congenital mesoblastic nephromas are infiltrating tumors that can contain cystic spaces lined with epithelium similar to that of dysplastic tubules and glomeruli. Urographic contrast material may enter these cystic spaces and suggest the diagnosis.