Variation in imaging outcomes associated with individual sonographers and radiologists in pediatric acute appendicitis: a retrospective cohort of 9271 examinations.

OBJECTIVE: To determine if individual sonographers and radiologists impact appendix visualization by ultrasound and utilization of computed tomography (CT) in children with suspected acute appendicitis. MATERIALS AND METHODS: Appendix ultrasound examinations performed at Cincinnati Children's Hospital Medical Center on Emergency Department patients ≤ 18 years old were retrospectively identified. Examinations performed/interpreted by sonographers/radiologists with fewer than 100 examinations were excluded. Multivariable logistic regression was used to assess the effect of sonographer, radiologist, clinical variables, and system factors on imaging outcomes, including appendix visualization and subsequent CT utilization. RESULTS: A total of 9271 ultrasound examinations (mean [SD] patient age, 9.9 [4.2] years; 5392 [58.2%] boys) performed by 31 sonographers (mean number examinations, 299 [139]; range, 115-610) and interpreted by 31 radiologists (mean number examinations, 299 [157]; range, 101-845) were included. The mean frequency of appendix visualization per sonographer was 57.8% [8.7%] (range, 40.9-76.0%) and per radiologist was 59.5% [4.1%] (range, 51.7-66.3%). The mean rate of CT utilization per sonographer was 9.2% [2.0%] (range, 5.9-14.0%) and per radiologist was 9.2% [1.8%] (range, 3.4-12.1%). Predictors of appendix visualization by ultrasound included patient weight (p < 0.0001), sex (p = 0.0003), white blood cell count (p < 0.0001), temperature (p = 0.002), abdominal tenderness (p = 0.004), presence of appendicitis (p < 0.0001), sonographer (p < 0.0001), and radiologist (p = 0.02). Predictors of CT utilization included patient weight (p < 0.0001), white blood cell count (p < 0.0001), abdominal tenderness (p < 0.0001), rebound tenderness (p = 0.0003), and presence of appendicitis (p < 0.0001), but not sonographer or radiologist. CONCLUSION: Individual sonographers and radiologists were associated with appendix visualization by ultrasound in children with suspected acute appendicitis; neither was associated with CT utilization. KEY POINTS: • Individual sonographers and radiologists are significantly and independently associated with appendix visualization by ultrasound in children with suspected acute appendicitis. • Frequency of appendix visualization per sonographer demonstrated significant and wide variability across 31 sonographers, ranging from 40.9 to 76.0%. • Fewer than 10% of patients with an ultrasound examination for suspected acute appendicitis underwent CT imaging within the following 24 h. Individual radiologists and sonographers were not predictive of CT utilization within 24 h.

Comparison of 0.3-mSv CT to Standard-Dose CT for Detection of Lung Nodules in Children and Young Adults With Cancer.

BACKGROUND. CT is the imaging modality of choice to identify lung metastasis. OBJECTIVE. The purpose of this study was to evaluate the performance of reduced-dose CT for the detection of lung nodules in children and young adults with cancer. METHODS. This prospective study enrolled patients 4-21 years old with known or suspected malignancy who were undergoing clinically indicated chest CT. Study participants underwent an additional investigational reduced-dose chest CT examination in the same imaging encounter. Separated deidentified CT examinations were reviewed in blinded fashion by three independent radiologists. One reviewer performed a subsequent secondary review to match nodules between the standard- and reduced-dose examinations. Diagnostic performance was computed for the reduced-dose examinations using the clinical examinations as the reference standard. Intraobserver agreement and interobserver agreement were calculated using Cohen kappa. RESULTS. A total of 78 patients (44 male patients and 34 female patients; mean age, 15.2 ± 3.8 [SD] years) were enrolled. The mean estimated effective dose was 1.8 ± 1.1 mSv for clinical CT and 0.3 ± 0.1 mSv for reduced-dose CT, which is an 83% dose reduction. Forty-five of the 78 (58%) patients had 162 total lung nodules (mean size, 3.4 ± 3.3 mm) detected on the clinical CT examinations. A total of 92% of nodules were visible on reduced-dose CT. The sensitivity and specificity of reduced-dose CT for nodules ranged from 63% to 77% and from 80% to 90%, respectively, across the three reviewers. Intraob-server agreement between clinical CT and reduced-dose CT was moderate to substantial for the presence of nodules (κ = 0.45-0.67) and was good to excellent for the number of nodules (κ = 0.68-0.84) and nodule size (κ = 0.69-0.86). Interobserver agreement for the presence of nodules was moderate for both reduced-dose (κ = 0.53) and clinical (κ = 0.54) CT. A median of one nodule was present on clinical CT in patients with a falsely negative reduced-dose CT examination. CONCLUSION. Reduced-dose CT depicts more than 90% of lung nodules in children and young adults with cancer. Reviewers identified the presence of nodules with moderate sensitivity and high specificity. CLINICAL IMPACT. CT performed at a 0.3-mSv mean effective dose has acceptable diagnostic performance for lung nodule detection in children and young adults and has the potential to reduce patient dose or expand CT utilization (e.g., to replace radiography in screening or monitoring protocols). TRIAL REGISTRATION. ClinicalTrials.gov NCT03681873.

Primary thyroid dysfunction after single intravenous iodinated contrast exposure in young children: a propensity score matched analysis.

BACKGROUND: Data suggest an increased risk of thyroid dysfunction following iodine-based contrast material (IBCM) in children. OBJECTIVE: To estimate the prevalence of thyroid stimulating hormone (TSH) abnormalities following exposure to a single dose of intravenous IBCM during computed tomography (CT) in young children. MATERIALS AND METHODS: Inpatients ≤24 months of age who underwent a single CT with intravenous IBCM (exposed cohort) or abdominal ultrasound (US) (unexposed cohort) examination and had a TSH value obtained within 90 days after imaging between January 2009 to November 2018 were identified. Propensity score matching with 20 variables was performed. Primary thyroid dysfunction was defined by abnormally high or low TSH value. Multivariable logistic regression identified risk factors, including intravenous IBCM, for thyroid dysfunction. RESULTS: From the eligible 4,215 imaging examinations, 114 unique patients were included in the propensity matched population (n=57 per group). Thyroid dysfunction was identified in 14% (8/57) and 7% (4/57) of the IBCM-exposed and IBCM-unexposed cohorts, respectively. No patient in either cohort was started on thyroid hormone supplementation within the 3 months after imaging. Intravenous IBCM exposure was not a significant predictor of thyroid dysfunction on univariable (odds ratio [OR]=2.16, 95% confidence interval [CI]=0.61-7.64, P=0.23) or multivariable (OR=2.61, 95% CI=0.65-10.55, P=0.18) analyses. Significant independent predictors of post-imaging thyroid dysfunction included height (OR=1.25, P=0.0095) and trisomy 21 (OR=4.04, P=0.019). CONCLUSION: Hospitalized children ≤24 months of age who received a single dose of intravenous IBCM for CT examination had a similar prevalence of TSH abnormalities compared to a propensity score matched group who underwent abdominal US. One dose of intravenous IBCM likely does not cause prolonged TSH abnormalities; however, larger studies are needed.

Risk of Acute Kidney Injury Following Contrast-enhanced CT in Hospitalized Pediatric Patients: A Propensity Score Analysis.

Background Acute kidney injury (AKI) remains a concern in hospitalized children undergoing CT with intravenous iodinated contrast material (ICM). Adult studies have shown frequencies of AKI after CT with intravenous ICM to be similar to propensity score-matched ICM-unexposed patient groups; similar data in pediatric patients are lacking. Purpose To evaluate the association between intravenous ICM exposure and AKI in hospitalized pediatric patients with stable kidney function undergoing contrast material-enhanced CT by comparing with a propensity score-matched ICM-unexposed patient sample undergoing abdominal US. Materials and Methods In this retrospective observational study, hospitalized patients aged 18 years or younger with stable kidney function and available serum creatinine (SCr) measurement before and after imaging who underwent CT with intravenous ICM or abdominal US (control group) between January 2009 and November 2018 were identified. The 1:1 propensity score matching was performed by using 23 covariates, stratified by estimated glomerular filtration rate (eGFR) before imaging (≥60 mL/min/1.73 m2 or <60 mL/min/1.73 m2). AKI was defined by using Acute Kidney Injury Network SCr-related criteria. Multivariable logistic regression was performed to identify risk factors for AKI after imaging, including the effects of eGFR and intravenous ICM exposure before imaging. Results A total of 1850 unique patients were included in the propensity score-matched sample (925 exposed to ICM [mean age ± standard deviation, 8 years ± 6; 484 female patients]; 925 unexposed to ICM [mean age, 7 years ± 6; 484 female patients]). Frequency of AKI with eGFR greater than or equal to 60 mL/min/1.73 m2 was 2.2% (20 of 889) for CT and US (odds ratio [OR]: 0.98; 95% confidence interval [CI]: 0.52, 1.86; adjusted P = .95) and with eGFR less than 60 mL/min/1.73 m2 was 5.6% (two of 36) and 11.1% (four of 36) for CT and US, respectively (OR: 0.75; 95% CI: 0.11, 5.00; adjusted P = .76). Significant multivariable predictors of AKI included eGFR before imaging (OR: 0.99; 95% CI: 0.98, 0.995; P = .001), body mass index (OR: 1.06; 95% CI: 1.02, 1.10; P = .003), acquired kidney disease (OR: 1.95; 95% CI: 1.004, 3.78; P = .049), and nephrotoxic antibiotic exposure (OR: 2.86; 95% CI: 1.55, 5.25; P < .001). Intravenous ICM exposure was not predictive (OR: 0.91; 95% CI: 0.51, 1.64; P > .05). Conclusion Hospitalized children with stable kidney function who underwent CT with intravenous iodinated contrast material (ICM) had a similar frequency of acute kidney injury (AKI) compared with a propensity score-matched ICM-unexposed patient group. In pediatric inpatients with estimated glomerular filtration rate greater than or equal to 60 mL/min/1.73 m2, ICM was not independently associated with AKI. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Paltiel in this issue.

Fetal magnetic resonance imaging of skeletal dysplasias.

BACKGROUND: Fetal magnetic resonance imaging (MRI) is obtained for prenatal diagnosis and prognostication of skeletal dysplasias; however, related literature is limited. OBJECTIVE: The purpose of this study was to define the utility of fetal MRI for skeletal dysplasias and to report MRI findings associated with specific diagnoses. MATERIALS AND METHODS: This retrospective study was approved by the institutional review board; informed consent was waived. Women referred for suspected fetal skeletal dysplasia who underwent MRI between January 2003 and December 2018 were included. Definitive diagnoses were determined by genetic testing, autopsy, physical examination and/or postnatal/postmortem imaging. Fetal MRI examinations and reports were reviewed. Descriptive statistics were used to summarize imaging findings. RESULTS: Eighty-nine women were referred for fetal MRI for possible skeletal dysplasia. Forty-three (48%) were determined to have a diagnosis other than skeletal dysplasia and nine were excluded for lack of specific skeletal dysplasia diagnosis. Thirty-seven cases of skeletal dysplasia with available fetal MRI and specific diagnosis were included for analysis. Diagnoses included achondrogenesis (n=2), achondroplasia (n=5), Boomerang dysplasia (n=1), campomelic dysplasia (n=2), Jeune syndrome (n=1), Kniest dysplasia (n=1), osteogenesis imperfecta (n=15) and thanatophoric dysplasia (n=10). A specific skeletal dysplasia diagnosis was mentioned in 17/37 (46%) of MRI imaging reports and correct for 14/17 (82%). MRI findings were reported for each specific skeletal dysplasia diagnosis. CONCLUSION: Fetal MRI is a useful diagnostic tool for skeletal dyplasias and excluded the diagnosis in nearly half of referred pregnancies. In addition to providing fetal lung volumes, fetal MRI demonstrates findings of the brain in achondroplasia and thanatophoric dysplasia, of the spine in achondroplasia and achondrogenesis, of the calvarium in osteogenesis imperfecta and thanatophoric dysplasia, and of the cartilage in Kniest dysplasia.

Quantification of skeletal muscle mass: sarcopenia as a marker of overall health in children and adults.

Sarcopenia is defined as the loss of muscle mass or function and has been associated with increased morbidity and mortality in a variety of diseased populations. Sarcopenia results from a higher rate of muscle protein degradation compared to protein synthesis and is an important marker of metabolic status related to nutrition and physical activity. The diagnosis of sarcopenia is accomplished by clinical assessment demonstrating decreased muscle function and radiographic confirmation of decreased muscle mass, via dual X-ray absorptiometry, bioelectric impedance or cross-sectional imaging with CT or MRI. However, normative data for skeletal muscle mass are lacking, especially for children and young adults. Additionally, studies of skeletal muscle mass by cross-sectional imaging in children are scarce. Here, we review the concept of sarcopenia with an emphasis on its relevance in the pediatric population.

Magnetic resonance imaging T1 relaxation times for the liver, pancreas and spleen in healthy children at 1.5 and 3 tesla.

BACKGROUND: T1 relaxation time is a potential magnetic resonance imaging (MRI) biomarker for fibrosis and inflammation of the solid abdominal organs. However, normal T1 relaxation times of the solid abdominal organs have not been defined for children. OBJECTIVE: The purpose of this study was to measure T1 relaxation times of the liver, pancreas and spleen in healthy children. MATERIALS AND METHODS: This was an institutional review board-approved study of a convenience sample of prospectively recruited, healthy children ages 7 to 17 years undergoing research abdominal MRI (1.5 or 3 T) as part of a larger research study between February 2018 and October 2018. For the current study, T1 mapping was performed with a Modified Look-Locker sequence covering the upper abdomen. A single reviewer placed freehand regions of interest on the T1 parametric maps in the liver, pancreas and spleen, inclusive of as much parenchyma as possible. Student's t-tests and linear regression were used to compare T1 values by age and gender. RESULTS: Thirty-two participants were included (16 female:16 male; mean age: 12.2±3.1 years; n=16 at 1.5 T). Median T1 relaxation times (ms) per organ were liver: 581±64 (1.5 T), 783±88 (3 T); pancreas: 576±55 (1.5 T), 730±30 (3 T), and spleen: 1,172±71 (1.5 T), 1,356±87 (3 T). T1 values were not statistically significantly different between males and females. At both 1.5 and 3 T field strengths, linear regression showed no significant association between age and T1 values for the liver, pancreas and spleen. CONCLUSION: We report normal T1 relaxation times for the liver, pancreas and spleen at 1.5 and 3 T in a cohort of healthy children.

Normative values for ultrasound measurements of the female pelvic organs throughout childhood and adolescence.

BACKGROUND: Normative data from pelvic ultrasonography (US) of the pediatric female reproductive organs are outdated and limited by sample size. OBJECTIVE: The purpose of this study was to report normal uterine and ovarian volumes and endometrial stripe thickness in children and young adults and throughout the menstrual cycle in post-menarchal adolescents. MATERIALS AND METHODS: Females ages 0 through 20 years who underwent pelvic US between January 2010 and May 2014 were identified. After excluding patients with pelvic and/or endocrine pathology, nomograms of uterine and ovarian volumes and endometrial thickness by age year were created. Data for patients ages 12 years and older with a recorded day of last menstrual period were used to create additional nomograms of volumes/thickness throughout the menstrual cycle. Student's t-tests and linear regression were performed to assess differences in measurements between groups and association of volumes/thickness with age. RESULTS: During our study period, 5,647 patients underwent 6,953 pelvic US examinations. After further review, 907 examinations from 889 patients were included (mean age: 11.3±6.0 years). Mean pelvic US volumes (cm3) per organ were 25.5±27.0 (uterus), 4.5±4.7 (right ovary) and 4.0±4.1 (left ovary). Mean endometrial thickness was 4.5±3.7 mm. Right ovarian volume was significantly larger than the left (P=0.0126). Uterine volume, ovarian volume and endometrial thickness were significantly associated with age (P-values<0.0001). Plots of mean organ measurements with respect to week of menses are provided. CONCLUSION: We report normal volumes of the uterus and ovaries and endometrial stripe thickness measured by pelvic US throughout childhood and adolescence with reference to the menstrual cycle. These values are significantly associated with age and vary visually by menstrual cycle week.

Respiratory motion in children and young adults undergoing liver magnetic resonance imaging with intravenous gadoxetate disodium contrast material.

BACKGROUND: Gadoxetate disodium, utilized in hepatobiliary magnetic resonance (MR) imaging, has been associated with transient respiratory motion during the arterial phase in adults. OBJECTIVE: The purpose of this study was to determine the presence and severity of this phenomenon in children imaged awake versus under general anesthesia. MATERIALS AND METHODS: This retrospective cohort study was approved by the institutional review board; informed consent was waived. One hundred thirty exams of children ≤18 years old who underwent dynamic liver MR imaging with gadoxetate disodium between October 2010 and January 2018 were reviewed. Three pediatric radiologists scored respiratory motion artifacts on all imaging phases using a 5-point Likert scale. Differences in mean motion scores were assessed with analysis of variance and Tukey's multiple comparisons test, and multivariable regression was used to identify predictors of arterial phase motion in awake patients. RESULTS: One hundred thirty patients (50% [n=65] female; mean age: 9.8±3.7 years, 48.5% [n=63] awake) were included. There were significant differences in mean motion scores between phases in the awake cohort (P<0.0001) but not in the general anesthesia cohort (P=0.051). In the awake cohort, arterial phase motion score (mean: 3.52±0.83) was significantly higher than mean motion score in all other phases (P≤0.0003). There were no significant patient-specific predictors of arterial phase motion score in the awake cohort. CONCLUSION: Significantly increased arterial phase respiratory motion artifact in awake children undergoing dynamic liver MR imaging with gadoxetate disodium suggests that transient respiratory motion occurs in children. General anesthesia may suppress this phenomenon.

Automated Segmentation of Abdominal Skeletal Muscle on Pediatric CT Scans Using Deep Learning.

PURPOSE: To automate skeletal muscle segmentation in a pediatric population using convolutional neural networks that identify and segment the L3 level at CT. MATERIALS AND METHODS: In this retrospective study, two sets of U-Net-based models were developed to identify the L3 level in the sagittal plane and segment the skeletal muscle from the corresponding axial image. For model development, 370 patients (sampled uniformly across age group from 0 to 18 years and including both sexes) were selected between January 2009 and January 2019, and ground truth L3 location and skeletal muscle segmentation were manually defined. Twenty percent (74 of 370) of the examinations were reserved for testing the L3 locator and muscle segmentation, while the remaining were used for training. For the L3 locator models, maximum intensity projections (MIPs) from a fixed number of central sections of sagittal reformats (either 12 or 18 sections) were used as input with or without transfer learning using an L3 localizer trained on an external dataset (four models total). For the skeletal muscle segmentation models, two loss functions (weighted Dice similarity coefficient [DSC] and binary cross-entropy) were used on models trained with or without data augmentation (four models total). Outputs from each model were compared with ground truth, and the mean relative error and DSC from each of the models were compared with one another. RESULTS: L3 section detection trained with an 18-section MIP model with transfer learning had a mean error of 3.23 mm ± 2.61 standard deviation, which was within the reconstructed image thickness (3 or 5 mm). Skeletal muscle segmentation trained with the weighted DSC loss model without data augmentation had a mean DSC of 0.93 ± 0.03 and mean relative error of 0.04 ± 0.04. CONCLUSION: Convolutional neural network models accurately identified the L3 level and segmented the skeletal muscle on pediatric CT scans.Supplemental material is available for this article.See also the commentary by Cadrin-Chênevert in this issue.© RSNA, 2021.

Predictors of Clinical Outcomes in Pediatric Appendicitis: Role of the Individual Sonographer and Radiologist When Using a First-Line Ultrasound Approach.

OBJECTIVE: To determine if differences between individual sonographers and radiologists performing and interpreting appendix ultrasound affect clinically important outcomes in children with suspected acute appendicitis. METHODS: Patients <18 years of age who presented to our emergency department (ED) with suspected acute appendicitis and underwent an appendix ultrasound were identified. Sonographers who performed fewer than 100 examinations and radiologists who interpreted fewer than 100 examinations during the study period were excluded. Multivariable logistic regression was performed to assess the effect of sonographer, radiologist, clinical variables, and system factors on key clinical outcomes, including hospital admission and appendectomy. RESULTS: In all, 9,283 appendix ultrasounds (mean age, 9.9 ± 4.2 years; 5,400 [58.2%] boys) performed by 31 sonographers (mean number of examinations, 299 ± 140 [range, 115-610]) and interpreted by 31 radiologists (mean number of examinations, 299 ± 157 [range, 101-845]) were included. Mean admission frequency per sonographer was 34.0% ± 3.3% (range, 27.8%-42.6%) and per radiologist was 33.5% ± 3.9% (range, 23.7%-41.6%). Mean appendectomy frequency per sonographer was 20.3% ± 2.6% (range, 14.9%-27.0%) and per radiologist was 20.3% ± 3.1% (range, 15.2%-28.7%). Significant multivariable predictors of hospital admission included temperature (P < .0001), white blood cell count (P < .0001), male sex (P = .002), imaging performed at the main hospital (versus satellite hospital) (P = .001), abdominal tenderness with ultrasound transducer compression (P < .0001), presence of rebound tenderness (P = .001), and presence of acute appendicitis by ultrasound (P < .0001), but not sonographer or radiologist. Predictors of appendectomy included weight (P < .0001), white blood cell count (P < .0001), male sex (P = .0004), abdominal tenderness with ultrasound transducer compression (P < .0001), and the presence of acute appendicitis by ultrasound (P < .0001), but not sonographer or radiologist. CONCLUSION: Differences in individual sonographers and radiologists did not predict clinically important outcomes in children undergoing ultrasound in the ED for suspected acute appendicitis.

Repeatability and Agreement of Shear Wave Speed Measurements in Phantoms and Human Livers Across 6 Ultrasound 2-Dimensional Shear Wave Elastography Systems.

OBJECTIVES: Ultrasound shear wave elastography (SWE) is an imaging technique that quantifies liver stiffness. However, comparison data across newest ultrasound systems are sparse. The purpose of this study was to assess repeatability and agreement of shear wave speeds (SWSs) across 6 ultrasound 2-dimensional (2D) SWE systems. MATERIALS AND METHODS: This cross-sectional, Health Insurance Portability and Accountability Act-compliant study received institutional review board approval. Written informed consent was obtained. Serial 2D SWE examinations were performed with 6 ultrasound systems (Aplio i800, Canon Medical Systems; LOGIQ E10, GE Healthcare; Resona 7, Mindray North America; EPIQ Elite, Philips Healthcare; ACUSON Sequoia, Siemens Medical Solutions; and Aixplorer MACH 30, SuperSonic Imagine) on 4 elastic phantoms (SWS range, 0.82-3.51 m/s) and on livers of 24 adults (healthy volunteers and patients with known liver stiffening). Participants were imaged 2 times per ultrasound system, with 90 to 120 minutes between examinations. Median SWS was calculated from separately acquired SWS measurements per examination (40 phantom measurements and 10 liver measurements per examination). RESULTS: Overall intraclass correlation coefficient (ICC) for intersystem agreement of median SWS across systems was 0.99 (95% confidence interval, 0.96-1.0) in phantoms and 0.66 to 0.69 (95% confidence interval, 0.47-0.84) in humans across systems. Means of median SWS measurements in humans ranged from 1.24 to 1.56 m/s. Average individual subject-level variance (interquartile range/median SWS) across all examinations was 0.07, with an average coefficient of variation of 6.0%. Pairwise ICCs for intersystem agreement in subjects across systems ranged from 0.41 to 0.91; test-retest repeatability in subjects was excellent for all systems, with ICCs ranging from 0.87 to 0.97. CONCLUSIONS: There is good to excellent intersystem agreement of measured SWS in elastic phantoms and in vivo livers across 6 ultrasound 2D SWE systems. Test-retest repeatability was excellent for all systems.

mTOR Inhibitor Therapy for Tuberous Sclerosis Complex: Longitudinal Study of Muscle Mass Determined by Abdominal Cross-sectional Imaging with CT and MRI.

Purpose: To determine the effect of chronic mammalian target of rapamycin (mTOR) inhibition on skeletal muscle mass in patients with tuberous sclerosis complex (TSC). Materials and Methods: In this retrospective study, patients with TSC who were taking mTOR inhibitors and who underwent at least two abdominal CT or MRI examinations between 2005 and 2017 were included (n = 24; 14 males; mean age, 14.5 years ± 7.8 [standard deviation] at first examination). One reviewer drew regions of interest around psoas muscles at L3 to measure cross-sectional area. Multiple linear mixed-effect modeling was performed to evaluate the association between muscle mass and the covariates over time. Results: The 24 patients underwent a total of 129 abdominal CT or MRI examinations. Median duration of mTOR inhibition at last examination was 106 months (range, 1310-3717 days). There was no significant association between the duration of mTOR inhibitor therapy and psoas muscle area on multiple linear mixed-effect modeling (P = .055); however, patient height and height squared were significant predictors of psoas area (P = .014 and P < .0001, respectively). Conclusion: Duration of mTOR inhibition in TSC was not significantly associated with a decrease in psoas muscle area, suggesting that chronic mTOR inhibition is not associated with sarcopenia.Keywords: CT, MR-Imaging, Pediatrics© RSNA, 2020.

Differentiating pediatric autoimmune liver diseases by quantitative magnetic resonance cholangiopancreatography.

PURPOSE: Autoimmune liver diseases (AILD), including primary sclerosing cholangitis (PSC), autoimmune sclerosing cholangitis (ASC), and autoimmune hepatitis (AIH), have overlapping clinical features but distinct management strategies and outcomes. The purpose of this study was to assess the diagnostic performance of quantitative magnetic resonance cholangiopancreatography (MRCP) parameters for distinguishing PSC/ASC from AIH in children and young adults. MATERIALS AND METHODS: This IRB-approved, cross-sectional study included participants from an institutional AILD registry that underwent baseline serum liver biochemistry testing and 3D fast spin-echo MRCP. The biliary tree was extracted and modeled from MRCP images using novel proprietary software (MRCP+ ™; Perspectum Diagnostics; Oxford, United Kingdom), and quantitative parameters were generated (e.g., biliary tree volume; number and length of bile ducts, strictures, and dilations; bile duct median/maximum diameters). Mann-Whitney U tests were performed to compare laboratory values and MRCP metrics between patient cohorts (clinical diagnosis of PSC/ASC versus AIH). Receiver operating characteristic (ROC) curves and multivariable logistic regression were used to assess diagnostic performance of serum biochemistry values and MRCP parameters for discriminating PSC/ASC from AIH. RESULTS: Thirty percent (14/47) of MRCP exams failed post-processing due to motion artifact. The remaining 33 patients included 20 males and 13 females, with a mean age of 15.1 ± 3.9 years. Eighteen patients were assigned the clinical diagnosis of PSC or ASC and 15 of AIH. All but one quantitative MRCP parameter were significantly different between cohorts (p < 0.05) and predictive of diagnosis (ROC p < 0.05), including numbers of bile duct strictures (area under curve [AUC] = 0.86, p < 0.0001) and dilations (AUC = 0.87, p < 0.0001) and total length of dilated ducts (AUC = 0.89, p < 0.0001). Laboratory values were not significantly different between cohorts (p > 0.05). The best multivariable model for distinguishing PSC/ASC from AIH included total length of dilated ducts (odds ratio [OR], 1.08; 95% CI 1.02-1.14) and maximum left hepatic duct diameter (OR, 1.21; 95% CI 0.57-2.56) [AUC = 0.92]. CONCLUSION: Quantitative MRCP parameters provide good discrimination of PSC/ASC from AIH.

Comparison of navigator-gated and breath-held image acquisition techniques for multi-echo quantitative dixon imaging of the liver in children and young adults.

PURPOSE: Acquired over a breath hold, multi-echo Dixon (mDixon) magnetic resonance imaging (MRI) of the liver can be used to quantify proton density fat fraction (PDFF) and iron-related signal decay. However, young, obese, and co-morbid patients may have limited breath holding capacity and could benefit from a motion-robust mDixon acquisition. The purpose of this study was to compare hepatic PDFF and R2* values between navigator-gated and breath-held mDixon MRI acquisition techniques in children and young adults with suspected liver disease. MATERIALS AND METHODS: This retrospective study was institutional review board-approved with a waiver of informed consent. Patients who underwent liver MRI with breath-held and navigator-gated mDixon sequences between January 2017 and July 2018 were included. One reviewer, blinded to sequence, measured PDFF and R2* on four images from each sequence. Another blinded reviewer graded respiratory motion (5-point Likert scale). Pearson correlation (r), Lin's concordance coefficients (rc), and Bland-Altman analyses were used to assess agreement between techniques. Frequency of clinically limiting motion (score ≥ 3) was compared with Fisher's exact test. RESULTS: Forty-two patients were included (15 female, 27 male; mean age: 15.7 ± 4.6 years). Mean PDFF and R2* were 16.6 ± 13.1% and 29.3 ± 4.7 s-1 (breath-held) versus 17.0 ± 13.2% and 29.6 ± 5.2 s-1 (navigator-gated). PDFF agreed almost perfectly between sequences (rc = 0.997, 95% CI 0.994-0.998; mean bias: 0.3%; 95% limits of agreement: - 2.4 to +1.7%), while R2* values correlated very strongly but with poor agreement (r = 0.837, rc = 0.832, 95% CI 0.716-0.910). Navigator-gated images exhibited significantly higher frequency of clinically limiting respiratory motion (88% vs. 48%, p = 0.0001). CONCLUSION: Despite greater respiratory motion artifact, a free-breathing navigator-gated mDixon sequence produces PDFF values with almost perfect agreement to a breath-held sequence.