Unenhanced whole-body MRI is safe and produces excellent images. The high sensitivity, specificity, and NPV make whole-body MRI a valuable cancer screening tool in children with a genetic predisposition for cancer.

A growing number of magnetic resonance (MR) imaging studies of the shoulder are being performed as a result of greater and earlier participation of children and adolescents in competitive sports such as softball and baseball. However, scant information is available regarding the MR imaging features of the normal sequential development of the shoulder. The authors discuss the radiographic and MR imaging appearances of the normal musculoskeletal maturation patterns of the shoulder, with emphasis on (a) development of secondary ossification centers of the glenoid (including the subcoracoid and peripheral glenoid ossification centers); (b) development of preossification and secondary ossification centers of the humeral head and the variable appearance and number of the secondary ossification centers of the distal acromion, with emphasis on the formation of the os acromiale; (c) development of the growth plates, glenoid bone plates, glenoid bare area, and proximal humeral metaphyseal stripe; and (d) marrow signal alterations in the distal humerus, acromion, and clavicle. In addition, the authors discuss various imaging interpretation pitfalls inherent to the normal skeletal maturation of the shoulder, examining clues that may help distinguish normal development from true disease (eg, osteochondral lesions, labral tears, abscesses, fractures, infection, tendon disease, acromioclavicular widening, and os acromiale). Familiarity with the timing, location, and appearance of maturation patterns in the pediatric shoulder is crucial for correct image interpretation.

Congenital lower limb shortening is a group of relatively rare, heterogeneous disorders. Proximal focal femoral deficiency (PFFD) and fibular hemimelia (FH) are the most common pathologic entities in this disease spectrum. PFFD is characterized by variable degrees of shortening or absence of the femoral head, with associated dysplasia of the acetabulum and femoral shaft. FH ranges from mild hypoplasia to complete absence of the fibula with variable shortening of the tibia. The development of the lower limb requires complex and precise gene interactions. Although the etiologies of PFFD and FH remain unknown, there is a strong association between the two disorders. Associated congenital defects in the lower extremity are found in more than 50% of patients with PFFD, ipsilateral FH being the most common. FH also has a strong association with shortening and bowing of the tibia and with foot deformities such as absence of the lateral rays of the foot. Early diagnosis and radiologic classification of these abnormalities are imperative for appropriate management and surgical planning. Plain radiography remains the main diagnostic imaging modality for both PFFD and FH, and appropriate description of the osseous abnormalities seen on radiographs allows accurate classification, prognostic evaluation, and surgical planning. Minor malformations may commonly be misdiagnosed.

Overall diagnostic accuracy of MRI and pre-surgical evaluation was quite high. The traumatic intra-articular knee lesions that still pose a diagnostic challenge for MRI and pre-surgical evaluation are lateral discoid meniscus, lateral meniscal tears, intra-articular loose bodies and osteochondral injuries. Special attention should be given to those diagnoses when evaluating a pediatric knee MRI. In children with multiple intra-articular injuries, there is significantly more inaccuracy in pre-arthroscopic diagnosis of lateral meniscal tears on both MRI and pre-surgical evaluation.

Purpose To determine the changes of diffusion-tensor imaging (DTI) and tractography in the distal femur and proximal tibia related to age, sex, and height. Materials and Methods Following institutional review board approval, with waiver of consent and with HIPAA compliance, the authors retrospectively analyzed DTI images of the knee in 151 children, 73 girls (median age, 14.1 years; range, 6.5-17.8 years) and 78 boys (median age, 16.6 years; range, 6.9-17.9 years), studied from January 2013 to October 2014. At sagittal echo-planar DTI (20 directions, b values of 0 and 600 sec/mm), regions of interest were placed in the tibial and femoral physes. Using a fractional anisotropy threshold of 0.15 and an angle threshold of 40°, the authors performed tractography and measured apparent diffusion coefficient (ADC) and tract length and volume. Changes related to age, sex, and height were evaluated by using fitted nonlinear polynomial functions on bootstrapped samples. Results Femoral tract volume and length increased and then decreased with age (P < .001); the peaks of femoral tract volume are consistent with the growth spurt, occurring earlier in girls (10.8 years) than in boys (13.0 years) (P < .001). Girls had smaller tract volumes in comparison to boys (P = .013). ADC peaks 2 years earlier than tract volume (girls at 9.3 years, boys at 11.0 years). Girls with greater than 50th percentile of height had longer tracts and greater tract volumes compared with girls with less than 50th percentile (P < .020). DTI parameters of boys do not correlate with percentile of height (P > .300). Conclusion DTI of the physis and metaphysis shows greater tract length and volumes in subjects who are at ages when the growth is fastest. ADC and tract length and volume have an earlier and smaller peak in girls than in boys. Femoral tract length and volume are larger in taller girls. RSNA, 2017.