Jung-Ah Choi

Radiologic Diagnosis of Osteoid Osteoma: From Simple to Challenging Findings

Osteoid osteoma is characterized by an intracortical nidus with a variable amount of calcification, as well as cortical thickening, sclerosis, and bone marrow edema. When these findings are present, a diagnosis of osteoid osteoma is easily made. However, osteoid osteoma may display imaging findings that can be misleading, and it can be difficult to differentiate osteoid osteoma from other conditions such as infection, inflammatory and noninflammatory arthritis, and other tumors. In addition, stress fracture, intracortical abscess, intracortical hemangioma, chondroblastoma, osteoblastoma, and compensatory hypertrophy of the pedicle may mimic osteoid osteoma. To make the correct diagnosis, it is necessary to identify the nidus, and it is important to be familiar with the radiologic findings of osteoid osteoma and its mimics.

Single shot fast spin echo diffusion-weighted MR imaging of the spine: Is it useful in differentiating malignant metastatic tumor infiltration from benign fracture edema?

PURPOSE This study aims to evaluate the usefulness of single shot fast spin echo diffusion-weighted MR imaging (DWSSFSE) in differentiating malignant metastatic tumor infiltration of vertebral bone marrow from benign vertebral fracture edema. MATERIALS AND METHODS Forty-six consecutive patients with 59 acute osteoporotic or traumatic vertebral fractures (mean age = 59) and 31 patients with 98 vertebral metastasis including 20 pathologic fractures (mean age = 53) were included in this study. Diffusion-weighted MR images were obtained by single-shot fast spin echo technique with diffusion gradient (b = 500 s/mm2, TR/TE: 5002/99) by using a 1.5 T MR scanner (Signa MR/i; GE Medical Systems, Milwaukee, WI, USA). T1- and T2-weighted images and short inversion time inversion-recovery (STIR) images were available in all 157 lesions, while contrast-enhanced images were available in 98 metastatic lesions. We evaluated signal intensity patterns on DWSSFSE in 157 lesions, which showed low signal intensity on T1-weighted images in both benign fractures and metastasis. The lesions on DWSSFSE were categorized as low, intermediate, and high signal intensity relative to presumed normal vertebra by concordant inspection of two experienced musculoskeletal radiologists. RESULTS In benign fractures, DWSSFSE images showed low signal intensity in 56 vertebrae (95%) in 43 patients (93%) and intermediate signal intensity in only 3 vertebrae (5%) in 3 patients (7%). On the other hand, metastases most commonly had low signal intensity in 57 vertebrae (58%) in 25 patients (80%), intermediate signal intensity in 35 vertebrae (36%) in 16 patients (52%), and high signal intensity in 6 vertebrae (6%) in 3 patients (10%). Thus, intermediate and high signal intensities are far more common than benign fractures. Such differences in signal intensity were statistically significant (chi-square test, P < .05). High or intermediate signal intensity on DWSSFSE was highly specific for the diagnosis of metastatic tumor infiltration of the spine (sensitivity: 42%; specificity: 95%; true positive rate: 93%; false negative rate: 52%). CONCLUSIONS DWSSFSE of the spine may be useful in differentiating metastatic tumor infiltration of vertebral bone marrow from benign fracture edema.

MR Imaging Assessment of the Spine: Infection or an Imitation?

Magnetic resonance (MR) imaging is a powerful diagnostic tool that can be used to help evaluate spinal infection and to help distinguish between an infection and other clinical conditions. In most cases of spinal infection, MR images show typical findings such as vertebral endplate destruction, bone marrow and disk signal abnormalities, and paravertebral or epidural abscesses. However, it is not always easy to diagnose a spinal infection, particularly when some of the classic MR imaging features are absent or when there are unusual patterns of infectious spondylitis. Furthermore, noninfectious inflammatory diseases and degenerative disease may simulate spinal infection. It is necessary to be familiar with atypical MR imaging findings of spinal infection and features that may mimic spinal infection to avoid misdiagnosis and inappropriate treatment.

MRI Findings of Subcutaneous Epidermal Cysts: Emphasis on the Presence of Rupture

OBJECTIVE Our aim was to describe the MRI findings of subcutaneous epidermal cysts with an emphasis on determining the presence of rupture. CONCLUSION Epidermal cysts show a fluidlike signal with variable low-signal components on T2-weighted images and peripheral rim enhancement on gadolinium-enhanced images. Most ruptured cysts have septa, show thick and irregular rim enhancement, and are accompanied by a fuzzy enhancement in surrounding subcutaneous tissues. These imaging features of a ruptured epidermal cyst simulate a mass of infectious or neoplastic origin.

Grading of anterior cruciate ligament injury: Diagnostic efficacy of oblique coronal magnetic resonance imaging of the knee

Objective This study was undertaken to evaluate the diagnostic efficacy of additional oblique coronal magnetic resonance (MR) imaging of the knee for the grading of anterior cruciate ligament (ACL) injury. Methods We retrospectively reviewed MR images of the knee in 169 patients. The MR examinations included routine sequences and oblique coronal T2-weighted images, which oriented in parallel to the course of the femoral intercondylar roof. Two independent readers evaluated the status of the ACL by routine knee MR imaging and then by additional oblique coronal imaging. The severity of the ACL injury was graded using a 4-point system from MR images, namely, intact, low-grade partial tear, high-grade partial tear, and complete tear, and results were compared with arthroscopic findings. Weighted &kgr; statistics were used to analyze the diagnostic accuracy of routine knee MR imaging with and without additional oblique coronal imaging. Results The weighted &kgr; scores (&kgr;ws) were 0.752 (reader 1) and 0.784 (reader 2) by routine knee MR imaging only; with additional oblique coronal imaging, the &kgr;ws increased to 0.809 (reader 1) and 0.843 (reader 2). Interobserver agreements for routine knee MR imaging and additional coronal imaging were considered to be “very good” (&kgr;w = 0.851, 0.868, respectively). Conclusion Additional use of oblique coronal MR imaging of the knee improves diagnostic accuracy in the grading of ACL injury.

MR Imaging Mapping of Skeletal Muscle Denervation in Entrapment and Compressive Neuropathies

The diagnoses of entrapment and compressive neuropathies have been based on the findings from clinical examinations and electrophysiologic tests, such as electromyography and nerve conduction studies. The use of magnetic resonance (MR) imaging for the diagnosis of entrapment or compressive neuropathies is increasing because MR imaging is particularly useful for discerning potential causes and for identifying associated muscle denervation. However, it is sometimes difficult to localize nerve entrapment or demonstrate nerve compression lesions with MR imaging. Nevertheless, even in these cases, MR imaging may show denervation-associated changes in specific muscles innervated by the affected nerves. The analysis of denervated muscle distributions by using MR imaging, with a knowledge of nerve innervation patterns, would be helpful for determining the nerves involved and the levels of nerve entrapment or compression. In this context, the mapping of skeletal muscle denervation with MR imaging has a supplementary or even a primary role in the diagnosis of entrapment and compressive neuropathies.

MRI of Gorham's disease: findings in two cases

Gorhams disease is a rare condition characterized by non-malignant proliferation of vascular or lymphatic structures of bone resulting in progressive bony destruction and often extending into surrounding soft tissues. We present two cases of MR imaging findings of Gorhams disease involving the axial and appendicular skeleton with a 10-year follow-up in one patient. MR imaging findings in this entity are reviewed.

Imaging findings of extrapulmonary metastases of osteosarcoma.

PURPOSE To review imaging findings of extrapulmonary metastasis from osteosarcoma and to evaluate them for any consistent pattern and correlation between imaging findings. MATERIALS AND METHODS This study was retrospectively conducted in 13 patients with extrapulmonary metastasis of pathologically confirmed osteosarcoma. We evaluated the radioisotope (RI) scans (n=16), ultrasonography (USG) (n=4), computed tomography (CT) scans (n=10), MRIs (n=6), clinical records, and pathological reports for assessment of imaging findings and correlation between radiologic findings and RI uptake of the lesions. Points evaluated were the following: uptake on RI scans, presence of mineralization on CT, and MRI, size, enhancement pattern, attenuation on CT, signal intensity (SI) on MRI, and echogenicity on USG. RESULTS Extrapulmonary metastatic sites were diverse, including another bone other than the primary site (n=6), lymph node (n=4), pleura (n=2), liver (n=2), pancreas (n=1), kidney (n=1), peritoneum (n=1), muscle (n=1), and subcutaneous fat layer (n=1). One patient had tumor growth within the pulmonary artery and jejunum. Among 21 metastatic sites in 13 patients, bone scan was performed in 16 cases and RI uptake was detected in 10 lesions. Calcification was detected in eight lesions on radiologic imaging, including plain radiography, USG, CT, and MRI. Two lesions showed RI uptake without definite calcification or ossification on MRI and plain radiography, respectively. We analyzed the enhancement pattern and mass size in 18 metastatic sites and these factors had poor correlation with uptake on RI scans. CONCLUSION The sites and imaging findings of extrapulmonary metastasis of osteosarcoma were variable. All the lesions with mineralization were detectable on RI scans prior to radiologic imaging. RI scan has a limited role in the evaluation of metastatic lesions without mineralization.

Angioleiomyoma in Soft Tissue of Extremities: MRI Findings

OBJECTIVE The purpose of our study was to describe the MRI findings of angioleiomyoma in the soft tissue of the extremities. CONCLUSION Angioleiomyoma should be considered a possible diagnosis when a well-demarcated subcutaneous mass of isointense signal on T1-weighted images, heterogeneous high signal intensity on T2-weighted images with homogeneous strong enhancement, and an adjacent tortuous vascular structure is seen in the extremities.

Superior Labral Anteroposterior Tears: Accuracy and Interobserver Reliability of Multidetector CT Arthrography for Diagnosis

PURPOSE To evaluate the accuracy and interobserver reliability of multidetector computed tomographic (CT) arthrography for the diagnosis and classification of superior labral anteroposterior (SLAP) lesions. MATERIALS AND METHODS Institutional review board approval and informed consent were obtained. Retrospective review of images from 161 multidetector CT arthrographic examinations was performed by two radiologists independently for detection and classification of SLAP lesions (type I-X), and sensitivity, specificity, accuracy, and interobserver agreement were evaluated. RESULTS The SLAP group included 94 patients, and the no-SLAP group included 67 patients with normal labrum. At arthroscopy, a total of 88 SLAP lesions (excluding type I) were found. For detection of SLAP lesions excluding SLAP type I lesions, sensitivity, specificity, and accuracy were 94.3%, 76.7%, and 86.3% for reader 1 and 97%, 72.6%, and 86.3% for reader 2, respectively, and the interobserver agreement was very good (κ = 0.87). The distribution of SLAP lesions was as follows: six type I, 58 type II, one type III, one type IV, 16 type V, one type VI, five type VII, three type VIII, one type IX, one type V and VI, and one type V and VII. Percentages of correct classification of SLAP lesions were variable according to the types, but the overall percentage was noted to be 69.2% for reader 1 and 68.1% for reader 2. The interobserver agreement of classification of SLAP lesions was good (κ = 0.72). CONCLUSION Multidetector CT arthrography shows high accuracy and good interobserver reliability for diagnosis of SLAP lesions in spite of its limitations in specific classification.