Victor Ho-Fung

MRI features of plexiform neurofibromas involving the liver and pancreas in children with neurofibromatosis type 1

AIM To describe magnetic resonance imaging (MRI) findings of plexiform neurofibromas (PNF) involving the liver and pancreas in paediatric patients with neurofibromatosis type 1 (NF1). MATERIALS AND METHODS A retrospective search of the hospital database was undertaken to find cases of PNF in the porta hepatis, hilar neurofibroma, and hepatic neurofibroma over a 12 year period. The images were analysed and a review of the charts was undertaken. RESULTS Five paediatric patients were identified with extensive PNFs involving the liver. In all cases, the PNFs involved the liver along the intrahepatic portal distribution. Additionally, the gallbladder fossa was affected in 2/5 patients, the pancreatic head in 4/5 patients, the pancreatic neck in 2/5 patients, and the pancreatic tail in 1/5 patients. All tumours showed low signal intensity (SI) on T1-weighted images and high SI with a central target sign on water-sensitive sequences. No patient showed any signs or symptoms, nor required treatment or surgery related to hepatic or pancreatic involvement. Intrahepatic PNFs were stable over a median follow-up time of 3.6 years (range 3 months to 8.8 years). CONCLUSIONS Intrahepatic and pancreatic involvement, although rare, does occur in paediatric NF1 patients. The MRI findings of the tumour are similar to the PNFs that occur more commonly elsewhere in this population. The hallmark of liver involvement is the periportal distribution.

Cartilage Imaging in Children: Current Indications, Magnetic Resonance Imaging Techniques, and Imaging Findings

Evaluation of hyaline cartilage in pediatric patients requires in-depth understanding of normal physiologic changes in the developing skeleton. Magnetic resonance (MR) imaging is a powerful tool for morphologic and functional imaging of the cartilage. In this review article, current imaging indications for cartilage evaluation pertinent to the pediatric population are described. In particular, novel surgical techniques for cartilage repair and MR classification of cartilage injuries are summarized. The authors also provide a review of the normal anatomy and a concise description of the advances in quantitative cartilage imaging (ie, T2 mapping, delayed gadolinium-enhanced MR imaging of cartilage, and T1rho).

The trochlear pre-ossification center: a normal developmental stage and potential pitfall on MR images

BackgroundThe hypertrophic changes that occur in the cartilage of an epiphysis prior to the onset of ossification are known as the pre-ossification center. Awareness of the appearance of the pre-ossification center on MR images is important to avoid confusing normal developmental changes with pathology.ObjectiveThe purpose of this study was to determine the characteristics of the trochlear pre-ossification center on MR imaging and examine age and gender differences.Materials and methodsWe retrospectively analyzed MR images from 61 children. The trochleas were categorized into three types on the basis of signal intensity (SI). Trochlear types were compared to age and gender.ResultsThere was no significant difference between the ages of boys and girls. Type 1 trochleas showed homogeneous SI on all pulse sequences. Type 2 trochleas demonstrated a focus of high SI in the epiphyseal cartilage on fat-suppressed water-sensitive sequences, with high or intermediate SI on gradient-echo images (pre-ossification center). Type 3 trochleas showed low SI on fat-suppressed water-sensitive sequences and gradient-echo images. Thirty-seven trochleas were described as type 1, sixteen as type 2 and eight as type 3. ANOVAs confirmed a statistically significant difference in the age of children with type 3 trochleas and those with types 1 and 2 (P < 0.001). Spearman rank correlations determined a positive relationship between trochlear type and age of the children (r = 0.53).ConclusionDevelopment-related changes in the trochlea follow a predictable pattern. The signal characteristics of the pre-ossification center likely reflect normal chondrocyte hypertrophy and an increase in free water in the matrix.

Common Patterns of Congenital Lower Extremity Shortening: Diagnosis, Classification, and Follow-up

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.

Diagnostic performance of magnetic resonance arthrography of the shoulder in children

BackgroundNo reported data demonstrate the usefulness of magnetic resonance arthrography of the shoulder in children.ObjectiveTo evaluate the sensitivity, specificity and accuracy of MR arthrography in the assessment of superior labral anteroposterior (SLAP) tears of the shoulder, Bankart-type injuries and Hill-Sachs lesions in children as compared to arthroscopy.Materials and methodsWe retrospectively interpreted 66 MR arthrograms of the shoulder and compared them with surgical findings. Assessment included evaluation of the osseous structures, labral-ligamentous complex and determination of skeletal maturity. We calculated sensitivity, specificity and accuracy and compared sensitivity and specificity between skeletally mature and immature children.ResultsMR arthrography demonstrated a sensitivity, specificity and accuracy of 88%, 98% and 94%, respectively, for depiction of SLAP tears; 94%, 92% and 94% for detection of Bankart-type injuries; and 100%, 94% and 97% for diagnosing Hill-Sachs lesions. There was no statistical difference between the skeletally immature and skeletally mature groups.ConclusionThere is no significant difference in the diagnostic accuracy of MR arthrography in skeletally immature versus skeletally mature children. MR shoulder arthrography is an effective method for the detection of labral and bone pathology.

MRI evaluation of the knee in children with infantile Blount disease: tibial and extra-tibial findings.

BackgroundInfantile Blount disease is a developmental condition characterized by disorganized endochondral ossification in the medial aspect of the proximal tibial physis.ObjectiveTo describe the MR imaging abnormalities in the proximal tibia, distal femur, menisci and ligaments of children with infantile Blount disease.Materials and methodsWe retrospectively evaluated 11 children (18 total knee MR examinations) with infantile Blount disease and compared them with an age-matched control group with normal MR examinations. Morphological and morphometric measurements were performed.ResultsThe medial menisci were enlarged with increased T2 signal intensity in all MR examinations. The medial femoral epiphyseal cartilage showed abnormal foci of increased signal intensity in nine (50%). The mid-coronal thickness of the medial tibial epiphyseal cartilage was decreased with concomitant increase in the mid-coronal joint space distance. Angular measurements of the proximal tibia demonstrated posteromedial down-sloping configuration.ConclusionsMost severe abnormalities of infantile Blount disease occur in the medial compartment of the knee, especially at the medial tibial physis and epiphysis. However, other important structures of the knee and the lateral compartment are often affected. MR imaging helps to delineate the extent of multiple tibial and extra-tibial abnormalities, including meniscal abnormalities, perichondrial membrane changes and premature physeal closure.

Quantification of Bone Marrow Involvement in Treated Gaucher Disease With Proton MR Spectroscopy: Correlation With Bone Marrow MRI Scores and Clinical Status

OBJECTIVE The objective of our study was to use proton MR spectroscopy (MRS) to quantitatively evaluate bone marrow infiltration by measuring the fat fraction (FF) and to compare the FF with semiquantitative bone marrow MRI scores and clinical status in children treated for type 1 Gaucher disease (GD). SUBJECTS AND METHODS Over a 2-year period, we prospectively evaluated 10 treated GD patients (six males, four females; median age, 15.1 years) and 10 healthy age-matched control subjects (five males, five females; median age, 15.3 years) using 3-T proton MRS of L5 and the femoral neck. Water and lipid AUCs were measured to calculate the FF. Two blinded pediatric musculoskeletal radiologists performed a semiquantitative analysis of the conventional MR images using the bone marrow burden score and modified Spanish MRI score. We evaluated symptoms, spleen and liver volumes, platelet levels, hemoglobin levels, and bone complications. RESULTS In the femur, the FF was higher in the control subjects (median, 0.71) than the GD patients (0.54) (p = 0.02). In L5, the difference in FF--higher FF in control subjects (0.37) than in GD patients (0.26)--was not significant (p = 0.16). In both groups and both regions, the FF increased with patient age (p < 0.02). Semiquantitative scores showed no differences between control subjects and treated GD patients (p > 0.11). Eight of 10 GD patients were asymptomatic and two had chronic bone pain. The median age of patients at symptom onset was 4.0 years, the median age of patients at the initiation of enzyme replacement therapy was 4.3 years, and the median treatment duration was 10.2 years. Hemoglobin level, platelet count, and liver volume at MRI were normal. Mean pretreatment spleen volume (15.4-fold above normal) decreased to 2.8-fold above normal at the time of MRI (p = 0.01). CONCLUSION Proton MRS detected FF differences that were undetectable using conventional MRI; for that reason, proton MRS can be used to optimize treatment of GD patients.

MRI of congenital and developmental abnormalities of the knee

The knee joint is the one of the most common locations for congenital and developmental musculoskeletal abnormalities. Initial imaging of the knee joint should always begin with conventional radiographs. However, evaluation of the bone marrow, cartilaginous, ligamentous, and other soft-tissue components of the knee joint are better characterized with magnetic resonance imaging (MRI). We present the MRI findings of prevalent congenital and developmental abnormalities in the paediatric knee with particular emphasis on the components of the growing skeleton.

Early experience with X-ray magnetic resonance fusion for low-flow vascular malformations in the pediatric interventional radiology suite

This technical innovation describes our experience using an X-ray magnetic resonance fusion (XMRF) software program to overlay 3-D MR images on real-time fluoroscopic images during sclerotherapy procedures for vascular malformations at a large pediatric institution. Five cases have been selected to illustrate the application and various clinical utilities of XMRF during sclerotherapy procedures as well as the technical limitations of this technique. The cases demonstrate how to use XMRF in the interventional suite to derive additional information to improve therapeutic confidence with regards to the extent of lesion filling and to guide clinical management in terms of intraprocedural interventional measures.

Diffusion-Tensor Imaging of the Growing Ends of Long Bones: Pilot Demonstration of Columnar Structure in the Physes and Metaphyses of the Knee

PURPOSE To determine the feasibility of using in vivo diffusion-tensor imaging and tractography of the physis to examine changes related to rate of growth, location, and age. MATERIALS AND METHODS This retrospective study was institutional review board approved and HIPAA compliant and the requirement for informed consent was waived. Diffusion-tensor imaging of the knee was performed at 3.0 T in 31 subjects (nine boys and 22 girls) with a median age of 13.6 years. The mean ages of boys and girls were 14.7 years (range, 12.0-18.3 years) and 13.2 years (range, 7.0-18.6 years), respectively. Regions of interest were placed in the physis of the tibia and femur, and in the epiphyseal and articular cartilage of these bones. Tractography was performed by using a fractional anisotropic threshold of 0.15 and an angle threshold of 40°. The tractographic patterns were qualitatively evaluated and changes related to age were described. The tract-based apparent diffusion coefficient, fractional anistropy, tensor eigenvalues, and tract length were measured. Diffusion parameters were compared between the center and periphery of the physis, and between the distal femur and proximal tibia. RESULTS Tractography resulted in parallel tracts in the physis and the adjacent metaphysis. Tractographic pattern changed with age, with individuals approaching physeal closure having shorter tracts in a random arrangement. Patterns of tractography varied with age in the femur (P < .001) and tibia (P < .001). Femoral tracts (median length, 6.5 mm) were longer than tibial tracts (median length, 4.3 mm) (P < .001). Tracts in the periphery of the physes were longer than those in the center (femur, P = .005; tibia, P = .004). In the physis of the femur and tibia, a significant age-related decrease was observed in apparent diffusion coefficient (P < .001 for both), axial diffusion (femur, P = .001; tibia, P < .001), and transverse diffusion [P < .001 for both]), and an age-related increase was seen in fractional anistropy (P < .001, for both). CONCLUSION Diffusion-tensor imaging shows the columnar microstructure of the physis and adjacent metaphysis, and provides further insight into normal growth.