Diffusion Tensor Imaging of the Knee to Predict Childhood Growth.

Background Accurate and precise methods to predict growth remain lacking. Diffusion tensor imaging (DTI) depicts the columnar structure of the physis and metaphyseal spongiosa and provides measures of tract volume and length that may help predict growth. Purpose To validate physeal DTI metrics as predictors of height velocity (1-year height gain from time of MRI examination) and total height gain (height gain from time of MRI examination until growth stops) and compare the prediction accuracy with bone age-based models. Materials and Methods Femoral DTI studies (b values = 0 and 600 sec/mm2; directions = 20) of healthy children who underwent MRI of the knee between February 2012 and December 2016 were retrospectively analyzed. Children with height measured at MRI and either 1 year later (height velocity) or after growth cessation (total height gain, mean = 34 months from MRI) were included. Physeal DTI tract volume and length were correlated with height velocity and total height gain. Multilinear regression was used to assess the potential of DTI metrics in the prediction of both parameters. Bland-Altman plots were used to compare root mean square error (RMSE) and bias in height prediction using DTI versus bone age methods. Results Eighty-nine children (mean age, 13 years ± 3 [SD]; 47 boys) had height velocity measured, and 70 (mean age, 14 years ± 1; 36 girls) had total height gain measured. Tract volumes correlated with height velocity (r2 = 0.49) and total height gain (r2 = 0.46) (P < .001 for both) after controlling for age and sex. Tract volume was the strongest predictor for height velocity and total height gain. An optimal multilinear model including tract volume improved prediction of height velocity (R2 = 0.63, RMSE = 1.7 cm) and total height gain (R2 = 0.59, RMSE = 1.8 cm) compared with bone age-based methods (height velocity: R2 = 0.32, RMSE = 2.9 cm; total height gain: R2 = 0.42, RMSE = 5.0 cm). Conclusion Models using tract volume derived from diffusion tensor imaging may perform better than bone age-based models in children for the prediction of height velocity and total height gain. © RSNA, 2022.

Longitudinal assessment of vascular calcification in generalized arterial calcification of infancy.

BACKGROUND: Generalized arterial calcification of infancy (GACI), also known as idiopathic infantile arterial calcification, is a very uncommon genetic disorder characterized by calcifications and stenoses of large- and medium-size arteries that can lead to end-organ damage. OBJECTIVE: To describe changes in imaging findings in 10 children with GACI at a single institution from 2010 to 2021. MATERIALS AND METHODS: In this retrospective study we reviewed initial and follow-up body imaging in children with genetic confirmation of GACI at our hospital. All initial images were analyzed for the presence and distribution of arterial calcifications, stenoses and wall thickening/irregularity within the chest, abdomen and pelvis. We compared available follow-up studies to the initial imaging findings. We extracted clinical information including prenatal and postnatal treatment from the children's medical records. RESULTS: We evaluated 10 children (five boys) with a diagnosis of GACI. Median age at first body imaging was 8 days (range: 1 day to 5 years). Six children were identified prenatally and four postnatally. Postnatal presentation included cardiac failure, seizures and hypertension. Images in newborns (n = 8) most commonly showed diffuse arterial calcifications (6/8; 75%), while stenoses were less common (2/8; 25%) during this period. Two children were diagnosed after the neonatal period - one in infancy and one during childhood. In total, half the children (5/10; 50%) had arterial stenoses - three cases visualized at first imaging and two identified on follow-up images during infancy. Stenoses had completely resolved in one child (1/5; 20%) at last follow-up. Eight children received prenatal or postnatal treatment or both. All children who received both prenatal and postnatal treatment (n = 4) had completely resolved calcifications at last follow-up. CONCLUSION: Children with GACI might have characteristic vascular calcifications at birth that raise the suspicion of this disease. Arterial calcifications decrease or disappear spontaneously or after treatment, but arterial stenoses usually persist. Calcifications and arterial stenoses can be easily identified and followed with non-contrast CT and CT angiography.

Humeral lesser tuberosity avulsion fractures - magnetic resonance imaging characteristics in the pediatric population.

BACKGROUND: Avulsion fractures of the humeral lesser tuberosity are rare injuries in skeletally immature patients and can pose a diagnostic challenge that often leads to delayed identification. OBJECTIVE: To describe the demographics, mechanism of injury and magnetic resonance imaging (MRI) findings of lesser tuberosity avulsion fractures in children. MATERIALS AND METHODS: A retrospective search of children with lesser tuberosity avulsion fractures on MRI was done. Available radiographs were evaluated. Demographics, mechanism of injury, MRI characteristics and treatment were recorded. RESULTS: Thirteen children, all male, were included (median age: 13.8 years, range: 12.5-16.8 years). The most common mechanism was blunt, overhead or hyperextension traumatic injury related to sports. All patients were skeletally immature and 10/13 demonstrated isolated avulsion fractures at the footprint. Only one patient had associated osteochondral injury to the humeral head and labral tear. Two children demonstrated medial dislocation/subluxation of the biceps tendon. The median size of the avulsed fragment was 15 mm (range: 5-29 mm), median anteroposterior displacement was 3 mm (range: 0-6 mm) and medial displacement was 1 mm (range: 0-20 mm). There was no correlation between age and the size of the avulsed fragment (P=0.29). Common injury patterns were complete avulsion of the subscapularis footprint (6/13) and partial avulsion of inferior footprint (6/13). Two-thirds of the radiographs were initially reported as normal, but retrospectively showed two missed fractures. One of the initial radiographs raised concern for bone tumor. The best view for identifying an avulsion fragment was the axillary view. Seven patients of the 13 patients underwent internal fixation. CONCLUSION: Avulsion fractures of the lesser tuberosity are rare, challenging to diagnose and often radiographically occult. MRI can identify the injury at the subscapularis tendon footprint with variable size and displacement. The long head of the biceps tendon is usually normal in location. Although this entity is rare, radiologists should be aware of it to allow for correct and prompt diagnosis and prevent unnecessary biopsy or contrast administration.

Prognostic value of the nutmeg lung pattern/lymphangiectasia on fetal magnetic resonance imaging.

BACKGROUND: A nutmeg lung pattern on magnetic resonance imaging (MRI) is an imaging finding associated with pulmonary lymphangiectasia. However, the prognostic value of the nutmeg lung pattern is unknown. OBJECTIVE: To evaluate the clinical associations of nutmeg lung indicating lymphangiectasia on fetal lung MRI and its relationship with early mortality in fetuses with primary and secondary lymphangiectasia. MATERIALS AND METHODS: We retrospectively identified all pregnant patients with a fetal MRI performed for indication of evaluating for pulmonary lymphangiectasia from 2006 to 2019. Two readers evaluated the fetal MRIs and interobserver agreement was calculated. Multivariable logistic regression models were performed to estimate the association of the echocardiographic findings and the presence of nutmeg lung. Kaplan-Meier and Cox regression analyses were performed to evaluate association with mortality in the first 30 days of life. Survival analysis was defined as mortality or orthotopic heart transplant at 30 days of age. P<0.05 was considered significant. RESULTS: Our sample included 53 fetuses. Forty-seven (89%) had congenital heart disease (CHD) and 6 (11%) were diagnosed postnatally with primary lymphangiectasia. Interobserver agreement was 0.83. Pulmonary vein congestion on echocardiography was the strongest predictor of nutmeg lung (odds ratio [OR]=12.0, P=0.002). Ten fetuses reached the outcome of heart transplantation (n=1) or death (n=9) within the first 30 days of life. In fetuses with CHD, survival of those with nutmeg lung was significantly lower than in those without (P<0.001). Nutmeg lung was an independent risk factor for 30-day mortality (hazard ratio [HR]: 6.1, P=0.01). CONCLUSION: Nutmeg lung pattern on fetal MRI is an independent risk factor associated with 30-day mortality in fetuses with CHD.

Imaging of children with COVID-19: experience from a tertiary children's hospital in the United States.

BACKGROUND: Imaging of novel coronavirus disease 2019 (COVID-19) has been described in adults, but children have milder forms of disease. Pediatric imaging descriptions are of asymptomatic children, raising the question of whether imaging is needed in this patient group. OBJECTIVE: To describe the utilization and imaging findings in children with COVID-19 along with the comorbidities, treatment and short-term outcomes. MATERIALS AND METHODS: We retrospectively reviewed pediatric patients who had a confirmed positive test for COVID-19 during a 2-month period. We noted symptoms and presence of imaging at presentation. Comorbidities were recorded for children with imaging. Children were categorized as having multisystem inflammatory syndrome in children (MIS-C) if they met criteria for the disorder. For children who were admitted to the hospital, we documented length of hospital stay, need for intensive care unit care/ventilator support, and treatment regimen. We evaluated all imaging for acute/chronic abnormalities including chest radiographs for interstitial or alveolar opacities, distribution/symmetry of disease, zonal predominance, and pleural abnormalities. We performed descriptive statistics and compared children with MIS-C with the cohort using a Fisher exact test. RESULTS: During the study period, 5,969 children were tested for COVID-19, with 313 (5%) testing positive. Of these, 92/313 (29%) were asymptomatic and 55/313 (18%) had imaging and were admitted to the hospital for treatment. Forty-one of 55 patients (75%) with imaging had comorbidities. Chest radiographs were the most common examination (51/55 patients, or 93%) with most demonstrating no abnormality (34/51, or 67%). Children with MIS-C were more likely to have interstitial opacities and pleural effusions. US, CT or MRI was performed in 23/55 (42%) children, 9 of whom had MIS-C. Only one chest CT was performed. CONCLUSION: In our study, most pediatric patients with COVID-19 did not require hospital admission or imaging. Most children with imaging had comorbidities but children with MIS-C were more likely to have no comorbidities. Children with imaging mostly had normal chest radiography. Advanced imaging (US, CT, MRI) was less common for the care of these children, particularly CT examination of the chest and for children without MIS-C.

Developmental dysplasia of the hip: can contrast-enhanced MRI predict the development of avascular necrosis following surgery?

OBJECTIVE: To investigate the performance of contrast-enhanced MRI for predicting avascular necrosis (AVN) of the treated femoral head after surgical reduction for developmental dysplasia of the hip (DDH) using qualitative and quantitative methods. METHODS AND MATERIALS: This IRB-approved, HIPAA compliant retrospective study included 47 children who underwent same-day contrast-enhanced MRI following unilateral surgical hip reduction between April 2009 and June 2018. Blinded to the clinical outcome, 3 reviewers (2 pediatric radiologists and 1 pediatric orthopedist) independently categorized the enhancement pattern of the treated femoral head. Signal intensities, measured using regions of interest (ROI), were compared between treated and untreated hips and percent enhancements were compared between hips that developed and did not develop AVN. Post-reduction radiographs were evaluated using Salter's criteria for AVN and Kalmachi and MacEwen's classification for growth disturbance. Non-parametric tests and Fisher exact test were used to compare enhancement values between AVN and non-AVN hips. Bonferroni correction was used for multiple comparisons. RESULTS: Ten (21%) out of the 47 children (7 boys and 40 girls; mean age 9.0 ± 4.7 months) developed AVN. Age at surgical reduction was significantly higher (p = 0.03) for hips that developed AVN. No significant differences were found in gender (p = 0.61), laterality (p = 0.46), surgical approach (p = 0.08), history of pre-operative bracing (p = 0.72), abduction angle (p = 0.18-0.44), enhancement pattern (p = 0.66-0.76), or percent enhancement (p = 0.41-0.88) between AVN and non-AVN groups. CONCLUSION: Neither enhancement pattern nor percent enhancement predicted AVN, suggesting that post-reduction conventional MRI does not accurately distinguish between reversible and permanent vascular injury.

Specific Absorption Rate and Specific Energy Dose: Comparison of 1.5-T versus 3.0-T Fetal MRI.

Background MRI performed at 3.0 T offers greater signal-to-noise ratio and better spatial resolution than does MRI performed at 1.5 T; however, for fetal MRI, there are concerns about the potential for greater radiofrequency energy administered to the fetus at 3.0-T MRI. Purpose To compare the specific absorption rate (SAR) and specific energy dose (SED) of fetal MRI at 1.5 and 3.0 T. Materials and Methods In this retrospective study, all fetal MRI examinations performed with 1.5- and 3.0-T scanners at one institution between July 2012 and October 2016 were evaluated. Two-dimensional (2D) and three-dimensional (3D) steady-state free precession (SSFP), single-shot fast spin-echo, 2D and 3D T1-weighted spoiled gradient-echo (SPGR), and echo-planar imaging sequences were performed. SAR, SED, accumulated SED, and acquisition time were retrieved from the Digital Imaging and Communications in Medicine header. Data are presented as mean ± standard deviation. Two one-sided tests with equivalence bounds of 0.5 (Cohen d effect size) were performed, with statistical equivalence considered at P < .05. Results A total of 2952 pregnant women were evaluated. Mean maternal age was 30 years ± 6 (age range, 12-49 years), mean gestational age was 24 weeks ± 6 (range, 17-40 weeks). A total of 3247 fetal MRI scans were included, with 2784 (86%) obtained at 1.5 T and 463 (14%) obtained at 3.0 T. In total, 93 764 sequences were performed, with 81 535 (87%) performed at 1.5 T and 12 229 (13%) performed at 3.0 T. When comparing 1.5- with 3.0-T MRI sequences, mean SAR (1.09 W/kg ± 0.69 vs 1.14 W/kg ± 0.61), mean SED (33 J/kg ± 27 vs 38 J/kg ± 26), and mean accumulated SED (965 J/kg ± 408 vs 996 J/kg ± 366, P < .001) were equivalent. Conclusion Fetal 1.5- and 3.0-T MRI examinations were found to have equivalent energy metrics in most cases. The 3.0-T sequences, such as two-dimensional T1-weighted spoiled gradient-echo and three-dimensional steady-state free precession, may require modification to keep the energy delivered to the patient as low as possible. © RSNA, 2020 Online supplemental material is available for this article.

Whole-body MRI in the diagnosis of paediatric CNO/CRMO.

Chronic recurrent multifocal osteomyelitis (CRMO) is an auto-inflammatory disorder affecting the skeleton of children and adolescents. Whole-body MRI (WBMRI) is key in the diagnosis and follow-up of CRMO. Imaging protocols should include sagittal short Tau inversion recovery of the spine, imaging of the hands and feet, and T1 images for distinguishing normal bone marrow. CRMO lesions can be metaphyseal, epiphyseal and physeal-potentially causing growth disturbance and deformity. Spinal lesions are common, important and can cause vertebral collapse. Lesion patterns include multifocal tibial and pauci-focal patterns that follow a predictable presentation and course of disease. Common pitfalls of WBMRI include haematopoietic marrow signal, metaphyseal signal early on in bisphosphonate therapy and normal high T2 signal in the hands and feet. Pictorial reporting assists in recording lesions and follow-up over time. The purpose of this paper is to review the different WBMRI protocols, imaging findings, lesion patterns and common pitfalls in children with CRMO.

Quantitative CT analysis for bronchiolitis obliterans in perinatally HIV-infected adolescents-comparison with controls and lung function data.

OBJECTIVE: To compare quantitative chest CT parameters in perinatally HIV-infected adolescents with and without bronchiolitis obliterans compared with HIV-uninfected controls and their association with lung function measurements. MATERIALS AND METHODS: Seventy-eight (41 girls) HIV-infected adolescents with a mean age of 13.8 ± 1.65 years and abnormal pulmonary function tests in the prospective Cape Town Adolescent Antiretroviral Cohort underwent contrast-enhanced chest CT on inspiration and expiration. Sixteen age-, sex-, and height-matched non-infected controls were identified retrospectively. Fifty-one HIV-infected adolescents (28 girls) displayed mosaic attenuation on expiration suggesting bronchiolitis obliterans. Pulmonary function tests were collected. The following parameters were obtained: low- and high-attenuation areas, mean lung density, kurtosis, skewness, ventilation heterogeneity, lung mass, and volume. RESULTS: HIV-infected adolescents showed a significantly higher mean lung density, ventilation heterogeneity, mass, and high- and low-attenuation areas compared with non-infected individuals. Kurtosis and skewness were significantly lower as well. HIV-infected adolescents with bronchiolitis obliterans had a significantly lower kurtosis and skewness compared with those without bronchiolitis obliterans. Lung mass and volume showed the strongest correlations with forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and alveolar volume. Low-attenuation areas below - 950 HU and ventilation heterogeneity showed the strongest correlation with FEV1/FVC (range, - 0.51 to - 0.34) and forced expiratory flow between 25 and 75% of FVC (range, - 0.50 to - 0.35). CONCLUSION: Quantitative chest CT on inspiration is a feasible technique to differentiate perinatally HIV-infected adolescents with and without bronchiolitis obliterans. Quantitative CT parameters correlate with spirometric measurements of small-airway disease. KEY POINTS: • Perinatally HIV-infected adolescents showed a more heterogeneous attenuation of the lung parenchyma with a higher percentage of low- and high-attenuation areas compared with non-infected patients. • Kurtosis and skewness are able to differentiate between HIV-infected adolescents with and without bronchiolitis obliterans using an inspiratory chest CT. • Quantitative CT parameters of the chest correlate significantly with pulmonary function test. Low-attenuation areas and ventilation heterogeneity are particularly associated with spirometric parameters related to airway obstruction.

MRI Findings of Infectious Sacroiliitis in Children: Are There Age-Dependent Differences?

OBJECTIVE. The purpose of this study was to investigate the prevalence of various MRI findings of infectious sacroiliitis in children and with respect to age. MATERIALS AND METHODS. This institutional review board-approved, HIPAA-compliant retrospective study included children with infectious sacroiliitis who underwent MRI examination between December 1, 2002, and September 30, 2018. Two radiologists blinded to the clinical outcome reviewed each MRI examination to determine the presence or absence of periarticular marrow edema, erosions, capsular bulge, extracapsular edema, and soft-tissue abscess. If available, pelvic radiographs were retrospectively reviewed by a third radiologist. Mann-Whitney U, chi-square, and Fisher exact tests were used to compare MRI findings between younger and older children. RESULTS. The study included 40 children (19 boys and 21 girls; mean age, 8.6 ± 6.2 [SD] years). Sixteen children presented at or below 5 years of age (mean age, 1.7 ± 1.4 years) and 24 children presented at or above 8 years of age (mean age, 13.3 + 2.6 years). Periarticular marrow edema and anterior extracapsular edema were present in all children. Posterior extracapsular edema (p = 0.01) was statistically significantly more common in younger children when compared with older children. There was no significant difference in the presence of erosions (p = 0.60), capsule bulge (p = 0.63), or abscess (p = 0.34) between younger and older children. Pelvic radiographs (n = 28; obtained 1.6 days ± 1.7 from MRI) allowed the correct identification of the abnormal joint in only 50% of the studies. CONCLUSION. MRI findings of infectious sacroiliitis are common in children of all ages with posterior extracapsular edema statistically significantly more prevalent in younger children.

Imaging of fetal lymphangiectasias: prenatal and postnatal imaging findings.

Lymphangiectasias are lymphatic malformations characterized by the abnormal dilation and morphology of the lymphatic channels. The classification and treatment of these disorders can be challenging given the limited amount of literature available in children. Various imaging modalities are used to confirm suspected diagnosis, plan the most appropriate treatment, and estimate a prognosis. Prenatal evaluation is performed using both prenatal US imaging and fetal MRI. These modalities are paramount for appropriate parental counseling and planning of perinatal care. During the neonatal period, chest US imaging is a useful modality to evaluate pulmonary lymphangiectasia because other modalities such as conventional radiography and CT display nonspecific findings. Finally, the recent breakthroughs in lymphatic imaging with MRI have allowed us to better classify lymphatic disorders. Dynamic contrast-enhanced lymphangiography, conventional lymphangiography and percutaneous lymphatic procedures offer static and dynamic evaluation of the central conducting lymphatics in children, with excellent spatial resolution and the possibility to provide treatment. The purpose of this review is to discuss the normal and abnormal development of the fetal lymphatic system and how to best depict it by imaging during the prenatal and postnatal life.

Osteochondral lesion of the talus in children: Are there MRI findings of instability?

PURPOSE: The purpose of our study was to investigate the performance of MRI findings to predict instability of osteochondral lesion of the talus (OLT) in children and the association between skeletal maturity and lesion stability. MATERIALS AND METHOD: This retrospective IRB-approved and HIPPA-compliant study included children with OLT, who underwent an ankle MRI examination between March 1, 2011, and May 31, 2018. Blinded to the clinical outcome, 2 radiologists retrospectively assessed each MRI study for the presence or absence of various features on the articular side, along the interface, and on the subchondral side of each lesion. Regional skeletal maturity was recorded. Lesion stability was classified using clinical and surgical findings. Mann-Whitney U, Chi-square, Fisher's exact, and Cochran-Armitage tests were used to compare demographic and MRI findings between children with stable and unstable lesions. RESULTS: Of the 48 ankles identified, 36 were stable (12.7 + 3.9 years) and 12 were unstable (14.2 + 1.6 years) lesions. None of the lesions presented as a detached fragment. Skeletal immaturity (p = 0.01) was significantly more common in stable than unstable lesions. No other MRI features were found to be significantly different between stable and unstable lesions, which included the presence of an effusion (p = 0.27), intra-articular body (p = 0.25), cartilage changes (p = 0.19), subchondral disruption (p = 0.51), T2-weighted signal intensity rim (p = 0.16), cysts (p = 0.48), marginal sclerosis (p = 0.70), and perilesional marrow edema (p = 0.17). CONCLUSION: Results from our study suggest that previously published OCD criteria using conventional MRI are not sufficient for predicting stability of OLT in children. Regional skeletal maturity and older age were more predictive of unstable lesions.

Biexponential R2* relaxometry for estimation of liver iron concentration in children: A better fit for high liver iron states.

BACKGROUND: R2* relaxometry's capacity to calculate liver iron concentration (LIC) is limited in patients with severe overload. Hemosiderin increases in these patients, which exhibits a non-monoexponential decay that renders a failed R2* analysis. PURPOSE/HYPOTHESIS: To evaluate a biexponential R2* relaxometry model in children with different ranges of iron overload. STUDY TYPE: Retrospective. POPULATION: In all, 181 children with different conditions associated with iron overload. FIELD STRENGTH/SEQUENCE: 1.5T, T2 *-weighted gradient echo sequence. ASSESSMENT: Bi- and monoexponential R2* relaxometry were measured in the liver using two regions of interest (ROIs) using a nonproprietary software: one encompassing the whole liver parenchyma (ROI-1) and the other only the periphery (ROI-2). These were drawn by a single trained observer. The residuals for each fitting model were estimated. A ratio between the residuals of the mono- and biexponential models was calculated to identify the best fitting model. Patients with 1) residual ratio ≥1.5 and 2) R2*fast ≥R2*slow were considered as having a predominant biexponential behavior. STATISTICAL TESTS: Nonparametric tests, Bland-Altman plots, linear correlation, intraclass correlation coefficient. Patients were divided according to their LIC into stable (n = 23), mild (n = 58), moderate (n = 61), and severe (n = 39). RESULTS: The biexponential model was more suitable for patients with severe iron overload when compared with the other three LIC categories (P < 0.001) for both ROIs. For ROI-1, 37 subjects met criteria for a predominant biexponential behavior. The slow component (5.7%) had a lower fraction than the fast component (94.2%). For ROI-2, 22 subjects met criteria for a predominant biexponential behavior. The slow component (4.7%) had a lower fraction than the fast component (95.2%). The intraobserver variability between both ROIs was excellent. DATA CONCLUSION: The biexponential R2* relaxometry model is more suitable in children with severe iron overload. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1191-1198.

Osteochondritis Dissecans of the Elbow in Children: MRI Findings of Instability.

OBJECTIVE. The purpose of this study was to investigate the performance of MRI criteria for predicting instability of osteochondritis dissecans (OCD) lesions of the elbow in children. MATERIALS AND METHODS. This retrospective study included 41 children with 43 OCD lesions of the elbow who underwent an MRI examination between April 1, 2010, and May 31, 2018. Two radiologists blinded to clinical outcomes reviewed MRI studies to determine the presence or absence of joint effusion, osteochondral defect, intraarticular body, overlying cartilage changes, subchondral bone disruption, rim of high signal intensity on T2-weighted images, cysts, marginal sclerosis, and perilesional bone marrow edema. The stability of OCD lesions was determined with clinical follow-up and surgical findings as reference standards. Mann-Whitney U, chi-square, Fisher exact, and Cochran-Armitage tests were used to compare MRI findings between stable and unstable OCD lesions. RESULTS. There were 20 stable and 23 unstable OCD lesions. An osteochondral defect (p = 0.01), intraarticular body (p < 0.001), overlying cartilage changes (p = 0.001), subchondral bone plate disruption (p = 0.02), and hyperintense rim (p = 0.01) were significantly more common in unstable than stable OCD lesions. However, only osteochondral defect and intraarticular body were 100% specific for OCD instability. There was no significant difference between stable and unstable OCD lesions in the presence of joint effusion (p = 0.10), cysts (p = 0.45), marginal sclerosis (p = 0.70), or perilesional bone marrow edema (p = 1.00). CONCLUSION. MRI findings of OCD instability of the elbow include an osteochondral defect, intraarticular body, overlying cartilage changes, subchondral bone disruption, and rim of high signal intensity on T2-weighted MR images.

Novel Computerized Analytic Technique for Quantification of Amniotic Fluid Volume in Fetal MRI.

OBJECTIVE. Fetal MRI is increasingly used in the evaluation of suspected congenital anomalies. Assessment of amniotic fluid volume (AFV) is crucial, but no automated quantitative technique is currently available for MRI. The purpose of this study was to develop and evaluate an analytic technique for quantifying AFV in fetal MRI. MATERIALS AND METHODS. Two MRI phantoms containing known quantities of synthetic amniotic fluid were created. A 3D steady-state free precession sequence was used for 1.5-T MRI of the phantoms and as part of a standard clinical fetal MRI protocol. Software was developed and used to retrospectively calculate AFV for the phantom and 20 clinical MRI examinations. Times to completion were recorded. AFV was also calculated by a manual hand-tracing method. To evaluate performance, paired t tests were used to compare computer-generated measurements with known phantom volumes. Intraclass correlation coefficients were calculated to assess agreement between computer-generated and manual measurements. RESULTS. There was no significant difference between computer-generated measurements of known AFV in the MRI phantoms (p > 0.11). When the software program was applied to the clinical MRI examinations, the mean time to complete AFV measurement was 110 seconds. There was excellent reliability between total AFV calculated by the two software users and by means of manual measurements (intraclass correlation coefficient, 0.995; p < 0.01). CONCLUSION. The computerized analysis evaluated in this study rapidly and accurately quantifies AFV in fetal MRI. The results are concordant with known phantom volumes and manual measurements. The technique is promising for objective MRI evaluation of AFV and has the potential to improve prenatal diagnosis and management.

Morel-Lavellée lesions: MRI characteristics in the pediatric patient.

BACKGROUND: A closed degloving injury is often referred to as a Morel-Lavellée lesion regardless of location despite traditionally being associated with the hip in adults. It results from a shearing injury that separates the subcutaneous layers from the fascia with fluid filling a potential space. OBJECTIVE: While the most common location and cause have been described in adults, there is limited literature in pediatric patients. We have seen pediatric Morel-Lavellée lesions commonly occurring at the knee after sports. We set out to describe the magnetic resonance imaging (MRI) characteristics. MATERIALS AND METHODS: A retrospective analysis was performed. All patients with trauma to the pelvis and lower extremities with a subcutaneous fluid collection seen on MRI were evaluated. Age, gender, mechanism of injury, time interval to imaging, and treatment were recorded. The collections were evaluated for location, size, shape and signal characteristics including the presence of fat, blood and septations. RESULTS: Twenty-one patients ages 7 to 17 years old had findings of degloving injury on MRI. The most common etiology was sports related (18/21, 85.7%). The anterior knee was most often affected (18/21, 85.7%). Lesions were ovoid and centered over the medial retinaculum (8/18, 44.4%) or lateral retinaculum (7/18, 38.9%). A capsule was weakly associated with later presentation (P=0.12). CONCLUSION: Pediatric Morel-Lavellée lesions commonly occur in a location not classically described, the anterior knee, and often after sports injury. Commonly, the collections are ovoid and always located at the subcutaneous fat/fascial interface. Recognition of specific imaging characteristics in a common location after sports injury allows for early identification. While most patients recover with conservative management, some need additional intervention with aspiration or debridement.

Imaging of developmental dysplasia of the hip: ultrasound, radiography and magnetic resonance imaging.

Developmental dysplasia of the hip (DDH) describes a broad spectrum of developmental abnormalities of the hip joint that are traditionally diagnosed during infancy. Because the development of the hip joint is a dynamic process, optimal treatment depends not only on the severity of the dysplasia, but also on the age of the child. Various imaging modalities are routinely used to confirm suspected diagnosis, to assess severity, and to monitor treatment response. For infants younger than 4 months, screening hip ultrasound (US) is recommended only for those with risk factors, equivocal or positive exam findings, whereas for infants older than 4-6 months, pelvis radiography is preferred. Following surgical hip reduction, magnetic resonance (MR) imaging is preferred over computed tomography (CT) because MR can not only confirm concentric hip joint reduction, but also identify the presence of soft-tissue barriers to reduction and any unexpected postoperative complications. The routine use of contrast-enhanced MR remains controversial because of the relative paucity of well-powered and validated literature. The main objectives of this article are to review the normal and abnormal developmental anatomy of the hip joint, to discuss the rationale behind the current recommendations on the most appropriate selection of imaging modalities for screening and diagnosis, and to review routine and uncommon findings that can be identified on post-reduction MR, using an evidence-based approach. A basic understanding of the physiology and the pathophysiology can help ensure the selection of optimal imaging modality and reduce equivocal diagnoses that can lead to unnecessary treatment.

Three-dimensional printed models of the rib cage in children with non-accidental injury as an effective visual-aid tool.

Three-dimensional (3-D) printing is gaining terrain in medical education, presurgical evaluation and recently as forensic evidence in court. Physicians, including radiologists, often provide expert testimony in court cases involving children with rib fractures and other injuries concerning for child physical abuse. Effectively communicating the complexities of fractures and other skeletal findings to nonmedical personnel using standard radiology studies can be challenging, especially during medical courtroom testimony. For this reason, we printed two 3-D models of the rib cage from the chest computed tomography (CT) scans of two patients with suspected non-accidental injury. The patients also had available chest radiographs. The DICOM (Digital Imaging and Communications in Medicine) data were 3-D reconstructed and segmented using two attenuation thresholds. We removed unwanted structures and printed them on a commercially available scanner. A pediatric radiologist, blinded to clinical data, reviewed both 3-D models, identified all rib lesions and classified them according to their healing stage. We compared the 3-D models and the chest radiograph against the chest CT as the standard of care. We convened a meeting with the Child Protection Team at out institution to get their feedback and opinions about the models. From our observations of our experts, three spontaneous interactions were observed. Instinctively, the experts picked up and grasped the models, rotating them, feeling them and angling them to better visualize the fractures from multiple angles. The experts expressed a willingness to consider using the models in court.

Relationship of renal apparent diffusion coefficient and functional MR urography in children with pelvicalyceal dilation.

OBJECTIVE: The aim is to evaluate the age-related changes and relationship of renal apparent diffusion coefficient (ADC) against the morphological and functional changes detected by functional magnetic resonance urography (fMRU) in children with pelvicalyceal dilation, with suspected or known ureteropelvic junction obstruction. MATERIALS AND METHODS: We retrospectively analyzed fMRUs with diffusion-weighted imaging (DWI) of the kidney in 35 subjects (25 males; median age: 7.1 years, range: 0.3-22.7 years) with 70 kidneys (40 with pelvicalyceal dilation and 30 with no pelvicalyceal dilation). Inclusion criteria were pelvicalyceal dilation, the absence of duplex kidneys and no ureteric dilation. DWI was performed with 3 diffusion gradient directions (b values = 0, 200, 500, 800 and 1,000 s/mm2). Metrics for fMRU included calyceal and renal transit times (CTT, RTT), time-to-peak (TTP), differential renal function based on volume (vDRF), Patlak number (pDRF) and combined volume and Patlak number (vpDRF). The grades of pelvicalyceal dilation, cortical thinning and corticomedullary differentiation were evaluated. The relationship between ADC values and the fMRU parameters was analyzed. RESULTS: ADC increases with age in kidneys without pelvicalyceal dilation (R2=0.37, P<0.001). Renal ADC does not correlate with any of the morphological or fMRU parameters (P>0.07). The median ADC of kidneys without pelvicalyceal dilation was 3.73×10-3 mm2/s (range: 2.78-5.37×0-3 mm2/s) and the median ADC of kidneys with pelvicalyceal dilation was 3.82×10-3 mm2/s (range: 2.70-5.70×10-3 mm2/s). There was no correlation between ADC and the absolute differences of vDRF or pDRF (P>0.33). CONCLUSION: Renal ADC does not correlate with morphological and functional results of fMRU changes in children with pelvicalyceal dilation due to suspected or known ureteropelvic junction obstruction.

Evaluating growth failure with diffusion tensor imaging in pediatric survivors of high-risk neuroblastoma treated with high-dose cis-retinoic acid.

BACKGROUND: The survival of patients with high-risk neuroblastoma has increased with multimodal therapy, but most survivors demonstrate growth failure. OBJECTIVE: To assess physeal abnormalities in children with high-risk neuroblastoma in comparison to normal controls by using diffusion tensor imaging (DTI) of the distal femoral physis and adjacent metaphysis. MATERIALS AND METHODS: We prospectively obtained physeal DTI at 3.0 T in 20 subjects (mean age: 12.4 years, 7 females) with high-risk neuroblastoma treated with high-dose cis-retinoic acid, and 20 age- and gender-matched controls. We compared fractional anisotropy (FA), normalized tract volume (cm3/cm2) and tract concentration (tracts/cm2) between the groups, in relation to height Z-score and response to growth hormone therapy. Tractography images were evaluated qualitatively. RESULTS: DTI parameters were significantly lower in high-risk neuroblastoma survivors compared to controls (P<0.01), particularly if the patients were exposed to both cis-retinoic acid and total body irradiation (P<0.05). For survivors and controls, DTI values were respectively [mean ± standard deviation]: tract concentration (tracts/cm2), 23.2±14.7 and 36.7±10.5; normalized tract volume (cm3/cm2), 0.44±0.27 and 0.70±0.21, and FA, 0.22±0.05 and 0.26±0.02. High-risk neuroblastoma survivors responding to growth hormone compared to non-responders had higher FA (0.25±0.04 and 0.18±0.03, respectively, P=0.02), and tract concentration (tracts/cm2) (31.4±13.7 and 14.8±7.9, respectively, P<0.05). FA, normalized tract volume and tract concentration were linearly related to height Z-score (R2>0.31; P<0.001). Qualitatively, tracts were nearly absent in all non-responders to growth hormone and abundant in all responders (P=0.02). CONCLUSION: DTI shows physeal abnormalities that correlate with short stature in high-risk neuroblastoma survivors and demonstrates response to growth hormone treatment.