Sung Hwan Hong

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.

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.

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 Findings of Giant Cell Tumors of the Spine

OBJECTIVE The purpose of this article is to describe the MRI features of giant cell tumors of the spine in 10 patients. CONCLUSION One of the tumors was located in C7. The other nine tumors were located in the thoracic spine, lumbar spine, and sacrum, three in each site. The characteristic findings included an expansile mass with heterogeneous low to intermediate signal intensity on the T2-weighted images (10/10), a curvilinear area of signal void on T1- and T2-weighted images (9/10), and cystic changes within the mass (4/10). Although no imaging feature was pathognomonic, MRI was found to be valuable in identifying the tumor, revealing its extent, and defining its relationship with the intraspinal structures.

Dysplastic nodules of the liver: imaging findings

AbstractBackground: To verify characteristic features of hepatic dysplastic nodules at different imaging modalities. Methods: Twenty-eight patients with 37 dysplastic nodules of the liver (0.8–3.0 cm) underwent sonography (28 patients), computed tomography (CT; 24 patients), magnetic resonance (MR; 11 patients), and angiography (12 patients). Each nodule was analyzed for echogenicity, attenuation, signal intensity, and vascularity. Results: Echogenicity of nodules was high in 16 (43%), homogeneous in two (6%), and low in 19 (51%) of 37 nodules. Attenuation of nodules was high in one (7%), homogeneous in four (26%), and low in 10 (67%) of 15 nodules on the arterial-phase CT images; homogeneous in five (33%) and low in 10 (67%) of 15 nodules on the portal-phase CT images; and high in four (17%), homogeneous in six (26%), and low in 13 (57%) of 23 nodules on the delayed-phase CT images. Signal intensity of nodules was high in 15 (94%) and homogeneous in one (6%) of 16 nodules on T1-weighted MR images and was homogeneous in seven (44%) and low in nine (56%) of 16 nodules on T2-weighted MR images. Vascularity of nodules was avascular in 14 (88%) and slightly vascular in two (12%) of 16 nodules. Conclusions: Hepatic dysplastic nodules show diverse imaging characteristics with different imaging techniques; however, common imaging findings of hepatic dysplastic nodules are low echo, low attenuation, and high, low, or homogeneous intensity on T1- and T2-weighted MR, and avascularity.

High resolution CT findings of miliary tuberculosis

PURPOSE The purpose of this study was to analyze high resolution CT (HRCT) findings of miliary tuberculosis and to assess the clinical utility of HRCT in the management of patients with miliary tuberculosis. METHOD We reviewed retrospectively HRCT scans of 25 patients with histopathologically (n = 16) and/or microbiologically (n = 9) proven miliary tuberculosis. RESULTS HRCT scans showed miliary nodules in 24 patients, which varied in size from 1 to 5 mm, with either sharply (n = 21) or poorly (n = 3) defined margins. The nodules had diffuse random distribution throughout both lungs and within the secondary pulmonary lobules. In 23 patients, areas of ground-glass opacities (GGOs) were observed with variable extent and distribution. The patients who had dyspnea showed large areas of GGOs, and two patients with impending adult respiratory distress syndrome revealed extensive GGOs. Both intralobular reticulation and interlobular septal thickening were seen in 10 patients. CONCLUSION Miliary nodules and GGOs are the predominant HRCT findings in patients with miliary tuberculosis, and HRCT scans are helpful in the early diagnosis and proper management of patients with miliary tuberculosis.

Metal artifact reduction by the alteration of technical factors in multidetector computed tomography: a 3-dimensional quantitative assessment.

Objective: The purpose of this study was to examine the effects of computed tomographic (CT) parameters on metal artifact reduction in multidetector CT (MDCT) using a quantitative 3-dimensional (3D) measurement of the metal artifact volume. Methods: A steel-based plate and screw were implanted in the femora of 3 porcine thigh specimens. The specimens were examined using 16-slice MDCT with 7 different combinations of acquisition parameters that consisted of kilovolt (peak) (kV[p]) and effective milliampere-seconds (mAs): 120 and 100; 120 and 300; 120 and 500; 120 and 1000; 140 and 100; 140 and 300; and 140 and 500 under a detector collimation of 0.75 mm and a beam pitch of 0.45. The axial image reconstructions were performed with 4 different settings: 0.75-, 1-, 2-, and 2-mm slice thickness reconstruction under an extended CT scale. At the levels of all 14 screws in the 3 femora, the metal artifact volumes in various combinations of acquisition and reconstruction settings were measured using personal computer-based 3D imaging software and were compared with each other. Results: The presence of a metal artifact was significantly reduced by increasing the kilovoltage and by decreasing the reconstruction thickness (P < 0.05; 2-way analysis of variance test). Neither increasing the effective mAs nor applying extended CT scale reduced the presence of the metal artifact significantly (P = 0.599 and P = 0.474, respectively). Compared with the metal artifact volume at 120 kV(p) and 100 mAs and a 2-mm slice thickness as a reference setting, the metal artifact reduction rate was 22% by increasing kilovoltage to 140, whereas only 11% by increasing mAs to 1000. Conclusions: We could quantitatively measure the metal artifact volume in MDCT by using 3D imaging software. In practice, the results of our study indicate that increasing kilovoltage is more effective for metal artifact reduction than increasing the effective mAs.

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.