Potential benefits of photon counting detector computed tomography in pediatric imaging.

Photon counting detector (PCD) CT represents the newest advance in CT technology, with improved radiation dose efficiency, increased spatial resolution, inherent spectral imaging capabilities, and the ability to eliminate electronic noise. Its design fundamentally differs from conventional energy integrating detector CT because photons are directly converted to electrical signal in a single step. Rather than converting X-rays to visible light and having an output signal that is a summation of energies, PCD directly counts each photon and records its individual energy information. The current commercially available PCD-CT utilizes a dual-source CT geometry, which allows 66 ms cardiac temporal resolution and high-pitch (up to 3.2) scanning. This can greatly benefit pediatric patients by facilitating high quality fast scanning to allow sedation-free imaging. The energy-resolving nature of the utilized PCDs allows "always-on" dual-energy imaging capabilities, such as the creation of virtual monoenergetic, virtual non-contrast, virtual non-calcium, and other material-specific images. These features may be combined with high-resolution imaging, made possible by the decreased size of individual detector elements and the absence of interelement septa. This work reviews the foundational concepts associated with PCD-CT and presents examples to highlight the benefits of PCD-CT in the pediatric population.

Adamantinoma-Like Ewing Sarcoma of the Mandible Evaluated on 18F-FDG PET/CT.

ABSTRACT: Ewing sarcoma is the second most common primary bone tumor in children. Typical Ewing sarcoma most frequently occurs in long bones and within the pelvis. ALES (adamantinoma-like Ewing sarcoma) is a rare subtype of Ewing sarcoma that is characterized by epithelial differentiation in addition to small round blue cells. Unlike typical Ewing sarcoma, ALES has been described in several cases in the head and neck. Herein, we describe a case of a 9-year-old boy with ALES of the mandible evaluated on 18F-FDG PET/CT with correlative MRI scans.

Imaging pediatric acute appendicitis during the coronavirus disease 2019 (COVID-19) pandemic: collateral damage is variable.

BACKGROUND: Since coronavirus disease 2019 (COVID-19) was declared a worldwide pandemic in March 2020, many authors have noted the collateral damage on non-COVID-19-related illnesses. These indirect effects of the pandemic have resulted in people presenting later and with more severe stages of disease, even if their diagnoses are not directly related to SARS-CoV-2, the virus that causes COVID-19. OBJECTIVE: We studied these indirect effects of COVID-19 on the imaging workup and outcomes for pediatric patients at our center who had acute appendicitis during the pandemic. MATERIALS AND METHODS: We performed a retrospective review of cases in children ≤18 years who were evaluated for acute appendicitis during the same period, March 1 to May 31, in both 2019 and 2020. We compared demographic and clinical data as well as surgical and pathological findings, and we graded imaging findings according to severity. Differences in patient outcomes were assessed using the Wilcoxon rank sum test and the Pearson chi-square test. RESULTS: The total number of pediatric patients evaluated with imaging for acute appendicitis dropped by 43% between 2019 and 2020 (298 vs. 169), but the total number of children treated remained similar (59 vs. 51). There was proportionate use of US and CT in each timeframe but a higher percentage of positive imaging findings in 2020 (50/169, 29.6% vs. 56/298, 18.7% in 2019, P=0.04). There were more imaging examinations with features of complicated appendicitis among positive cases (9/51, 18% vs. 5/59, 8% in 2019, P=0.08) and more pathologically proven perforated cases during the pandemic (14/51, 27% vs. 6/59, 10% in 2019, P=0.11), although these results did not reach statistical significance. There were no changes in surgical management, vital signs, laboratory values, length of stay or complication rates. CONCLUSION: There was a large drop in the number of pediatric patients imaged for acute appendicitis during the acute phase of the COVID-19 pandemic despite similar numbers of patients treated. The utilization trends of US vs. CT remained stable between time periods. The differences in imaging findings and perforation rates were less pronounced compared to other published studies.

Asymptomatic macrocephaly: to scan or not to scan.

BACKGROUND: Macrocephaly is a common finding in infants and is often idiopathic or familial. In the absence of clinical signs and symptoms, it can be difficult to determine when concern for underlying pathology is justified. OBJECTIVES: The objectives of this study were to determine the utility of screening head ultrasound (US) in asymptomatic infants with macrocephaly and to identify clinical factors associated with significant US findings. MATERIALS AND METHODS: A 20-year retrospective review was performed of infants undergoing head US for macrocephaly or rapidly increasing head circumference. Data collected included age, gender, head circumference at birth and at the time of US, specialty of the ordering physician, US findings, computed tomography (CT) or magnetic resonance imaging (MRI) findings, and clinical course including interventions. RESULTS: Four hundred and forty infants met inclusion criteria. Two hundred and eighty studies (64%) were found to be normal, 137 (31%) had incidental findings, 17 (3.8%) had indeterminate but potentially significant findings, and 6 (1.4%) had significant findings. Twenty of the 23 infants with indeterminate or significant findings had subsequent CT or MRI. This confirmed significant findings in eight infants (1.8%): three subdural hematomas, two intracranial tumors, two aqueductal stenoses, and one middle fossa cyst. Five of the eight infants required surgical procedures. The only statistically significant association found with having a significant finding on head US was head circumference at birth. CONCLUSION: Ultrasound is a useful initial study to evaluate infantile macrocephaly, identifying several treatable causes in our study and, when negative, effectively excluding significant pathology.

Pediatric appendiceal ultrasound: maintaining accuracy, increasing determinacy and improving clinical outcomes following the introduction of a standardized reporting template.

BACKGROUND: Pediatric patients who underwent appendiceal US and received an equivocal interpretation had poorer clinical outcomes and higher medical costs compared to those to whom a definitive interpretation was given, either positive or negative. In an effort to reduce equivocal interpretations, we educated our group on the importance of increasing determinacy and encouraged the use of a reporting template with a definitive impression. OBJECTIVE: We hypothesized that educational sessions and implementation of an optional reporting template with only a definitive impression would reduce equivocal reporting and improve clinical outcomes without negatively impacting US diagnostic performance. MATERIALS AND METHODS: We retrospectively reviewed the charts of all patients <18 years old at Mayo Clinic Rochester whose initial evaluation for acute appendicitis was a US in the 3-year period following educational sessions and template implementation. All studies were interpreted by board-certified fellowship-trained pediatric radiologists. We performed statistical analysis to compare the pre- and post-implementation cohorts. RESULTS: Following intervention, the rate of equivocal US interpretations was reduced from 23.7% to 9.3% (P<0.001). For studies with a definitive interpretation, measures of diagnostic performance of appendiceal US were similar for the pre- and post-implementation groups. US performance parameters were independent of appendiceal visualization. Follow-up CT utilization decreased from 18.7% to 8.9% (P<0.001). The negative laparotomy rate resulting from false-positive US interpretations remained low (6.8% vs. 5.0%, P=0.31). CONCLUSION: Following education sessions and implementation of an appendiceal US reporting template encouraging definitive reporting, equivocation was reduced, excellent diagnostic performance was maintained, follow-up CT utilization was reduced, and a low negative laparotomy rate was preserved.

Dual-energy X-ray absorptiometry bone densitometry in pediatrics: a practical review and update.

The assessment of pediatric bone mineral content and density is an evolving field. In this manuscript we provide a practical review and update on the interpretation of dual-energy X-ray absorptiometry (DXA) in pediatrics including historical perspectives as well as a discussion of the recently published 2019 Official Position Statements of the International Society of Clinical Densitometry (ISCD) that apply to children.

PET Imaging of a Unique Case of Multiple Myeloma in an Adolescent.

Pediatric solitary plasmacytomas are extremely rare, with only 14 cases previously reported. None of these reports included PET imaging findings. We present PET/CT and PET/MRI imaging findings in a 15-year-old boy with what was initially thought to be a solitary plasmacytoma, which later developed into multiple myeloma. The initial PET/CT of solitary plasmacytoma, as well as postradiotherapy PET/MRI findings with the new lesions suggestive of multiple myeloma, are presented.

Pediatric applications of Dotatate: early diagnostic and therapeutic experience.

In recent years, new somatostatin receptor agents (SSTRs) have become available for diagnostic imaging and therapy in neuroendocrine tumors. The novel SSTR ligand DOTA-DPhel-Tyr3-octreotate (Dotatate) in particular can be linked with 68Gallium for diagnostic imaging purposes, and with the ß-emitter 177Lutetium for radiotherapy in the setting of neuroendocrine tumors. Dotatate imaging offers distinct advantages in the evaluation of neuroendocrine tumors compared to standard techniques, including greater target-to-background ratio and lesion conspicuity, high sensitivity/specificity, improved spatial resolution with positron emission tomography (PET)/CT or PET/MR, and decreased radiation exposure. Although currently off-label in pediatrics, Dotatate theranostics in children are being explored, most notably in the setting of neuroblastoma and hereditary neuroendocrine syndromes. This article provides a multicenter case series of Dotatate imaging and therapy in pediatric patients in order to highlight the spectrum of potential clinical applications.

Mesenchymal Hamartoma in Children: A Diagnostic Challenge.

Mesenchymal hamartoma is a benign tumor of the liver with a poorly understood pathogenesis. It is uncommon in older children, especially after 2 years of age. The signs and symptoms may be nonspecific; therefore, a high index of suspicion is required for diagnosis and treatment. We report a 5-year-old previously healthy male who presented with acute abdominal pain, fatigue, and fever. He was diagnosed with pneumonia initially and treated with antibiotics. A computed tomography (CT) scan done for evaluation of his persistent abdominal pain demonstrated a hepatic mass. Follow-up magnetic resonance imaging (MRI) of the liver demonstrated multiple serpiginous tubular-type structures, read as possible Caroli syndrome. He had a normal abdominal examination and normal biochemistries including alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, and alpha-fetoprotein. He was referred to our institution for second opinion. On further review of his imaging studies, the lesion was thought to be a mesenchymal hamartoma. He subsequently underwent resection of the mass. Pathology confirmed the diagnosis of mesenchymal hamartoma.

Correction to: Pediatric ileocolic intussusception: new observations and unexpected implications.

In this article, the fourth author's name is misspelled. The correct spelling, as shown above, should be "Nadia F. Mahmood."

Pediatric ileocolic intussusception: new observations and unexpected implications.

BACKGROUND: Ileocolic intussusception occurs when the terminal ileum "telescopes" into the colon. We observed that ileocolic intussusception lengths are similar regardless of location in the colon. OBJECTIVE: To examine the uniformity of ileocolic intussusception length and its relationship to colon location, symptom duration and reducibility. MATERIALS AND METHODS: We retrospectively reviewed ultrasound-diagnosed pediatric ileocolic intussusceptions initially treated with pneumatic reduction at the Mayo Clinic or Texas Children's Hospital. We recorded demographic, imaging and surgical findings including age, gender, symptom duration, location of the ileocolic intussusception, reducibility with air enema and, if fluoroscopically irreducible, surgical findings. RESULTS: We identified 119 ileocolic intussusceptions (64% boys), with 81% in the right colon. There was no significant relationship between ileocolic intussusception length and colon location (P=0.15), nor ileocolic intussusception length and symptom duration (P=0.36). Ileocolic intussusceptions were more distal with increasing symptom duration (P=0.016). Successful reductions were unrelated to symptom duration (P=0.84) but were more likely with proximal versus distal locations (P=0.02). CONCLUSION: Ileocolic intussusception lengths are relatively uniform regardless of location along the course of the colon where they present. Our findings suggest that most of the apparent distal propagation of ileocolic intussusceptions is not caused by increasing telescoping of small bowel across the ileocecal valve but rather by foreshortening of the right colon. This implies poor cecal fixation and confirms fluoroscopic and surgical observations of cecal displacement from the right lower quadrant with ileocolic intussusceptions. The movement of the leading edge of the ileocolic intussusception during reduction is first due to "relocating" the cecum into the right lower quadrant after which the reduction of small bowel back across the ileocecal valve then occurs.

18F-FDG PET/CT Equivalent of the Hepatic Hot Spot Sign With CT Correlation.

A 43-year-old woman presented with an FDG-avid mediastinal Ewing sarcoma invading and nearly occluding the superior vena cava. Geographic increased FDG uptake in hepatic segment IVA was the only other site of nonphysiologic FDG activity. This focal activity was without an underlying mass, had atypical morphology for a hepatic metastasis, and correlated well with prior CT findings of abnormal segment IVA enhancement resulting from the recruitment of portocaval collaterals. In the correct setting, the F-FDG hepatic hot spot should be considered in the differential of a focal FDG-avid hepatic lesion in segment IVA.

Correction to: Chest computed tomography angiography in children on extracorporeal membrane oxygenation (ECMO).

The published version of this article incorrectly lists the authors' affiliations. The correct affiliations are given below. The Publisher regrets this mistake.

Chest computed tomography angiography in children on extracorporeal membrane oxygenation (ECMO).

Performing chest CT angiography on pediatric patients on extracorporeal membrane oxygenation (ECMO) can be challenging. Successfully performing CT angiography in these children requires substantial communication and coordination between the radiologists and clinical care providers. Additionally, the radiologist must understand the child's anatomy and disease pathophysiology, flow dynamics of the ECMO circuit, image acquisition timing, contrast injection site, and volume, rate and duration of contrast administration. In this article we highlight the vital factors the radiologist needs to consider to optimize the chest CT angiography in pediatric patients on ECMO.

Nuss bar migrations: occurrence and classification.

BACKGROUND: Pectus excavatum results from dorsal deviation of the sternum causing narrowing of the anterior-posterior diameter of the chest. It can result in significant cosmetic deformities and cardiopulmonary compromise if severe. The Nuss procedure is a minimally invasive technique that involves placing a thin horizontally oriented metal bar below the dorsal sternal apex for correction of the pectus deformity. OBJECTIVE: To identify the frequency and types of Nuss bar migrations, to present a new categorization of bar migrations, and to present examples of true migrations and pseudomigrations. MATERIALS AND METHODS: We retrospectively reviewed the electronic medical records and all pertinent radiologic studies of 311 pediatric patients who underwent a Nuss procedure. We evaluated the frequency and type of bar migrations. RESULTS: Bar migration was demonstrated in 23 of 311 patients (7%) and occurred within a mean period of 26 days after surgery. Bar migrations were subjectively defined as deviation of the bar from the position demonstrated on the immediate postoperative radiographs and categorized as superior, inferior, rotation, lateral or flipped using a new classification system. Sixteen of the 23 migrations required re-operation. CONCLUSION: Nuss bar migration can be diagnosed with careful evaluation of serial radiographs. Nuss bar migration has a wide variety of appearances and requires exclusion of pseudomigration resulting from changes in patient positioning between radiologic examinations.

¹¹C-Choline PET/CT in Recurrent Prostate Cancer and Nonprostatic Neoplastic Processes.

Choline positron emission tomography (PET)/computed tomography (CT), with both carbon 11 ((11)C) choline and fluorine 18 ((18)F) choline, is an increasingly used tool in the evaluation of patients with biochemically recurrent prostate cancer. It has allowed detection and localization of locally recurrent and metastatic lesions that were difficult or impossible to identify using more conventional modalities. Many of the patients followed for their prostate cancer are elderly and have a higher rate of nonprostate cancer lesions or malignancies. As our experience with choline PET/CT has grown, it has become apparent that many of these nonprostate cancer processes, both benign and malignant, can be detected. Invasive thymoma, renal cell carcinoma, papillary thyroid carcinoma, and parathyroid adenoma are a few of the processes that have been incidentally detected with (11)C-choline PET/CT at our institution and have significantly altered subsequent clinical management of the patient. Although most of the secondary lesions are detected due to their increased (11)C-choline avidity, several have been detected due to their decreased or lack of avidity in the background of a highly avid organ. For instance, large liver masses that are relatively non-choline-avid create large activity defects in the otherwise highly active liver. Familiarity with normal (11)C-choline physiologic activity, the most common prostate metastatic patterns, and imaging characteristics of secondary lesions is essential for the detection and correct diagnosis of such lesions so that proper follow-up and management can be recommended.