Akbar Bonakdarpour

Primary and Secondary Aneurysmal Bone Cyst: A Radiological Study of 75 Cases

Radiological findings in 75 cases of aneurysmal bone cyst were analyzed. Sixty-five per cent were primary or simple and 35% were secondary, the aneurysmal bone cyst being combined with other osseous lesions. A primary aneurysmal bone cyst can be diagnosed with a high degree of certainty, but only 20% of secondary forms had the radiological appearance of aneurysmal bone cyst; in the other 80% the associated lesion dominated the radiological picture, particularly when it was malignant. In the secondary form a small biopsy specimen may show the features of aneurysmal bone cyst only; without radiological assistance a concomitant malignant lesion may be missed. Therefore, there must be close collaboration between the radiologist and and the pathologist.

Accuracy of MRI patterns in evaluating anterior cruciate ligament tears

Abstract The purpose of this study was to determine the different patterns of anterior cruciate ligament (ACL) tears on MRI and the prevalence and accuracy of these patterns. Images were obtained on high-tesla and low-tesla units and the results compared to determine whether field strength affects the interpretation using the grading system. In 172 patients who underwent knee MRI (109 knees with high-tesla units and 63 knees with low-tesla units) and arthroscopy, there was a total of 91 arthroscopically proven ACL tears. Five patterns of ACL tears were observed and designated as type 1 (diffuse increase in signal on T2-weighted images and enlargement of the ligament, 48%); type 2 (horizontally oriented ACL, 21%); type 3 (nonvisualization of the ACL, 18%); type 4 (discontinuity of the ACL, 11%); and type 5 (vertically oriented ACL, 2%). The positive predictive value (PPV) for type 2, 4, and 5 patterns was 100% for both field strengths; for type 3 PPV was just above 80% for both field strengths. The PPV value for type 1 was 90% for the high-tesla unit and 79% for the low-tesla, unit, which was not statistically significant. Combining the results of both field strengths, the overall sensitivity and specificity were 93% and 89%, respectively. Arthroscopic results were also used to determine the association between meniscal and ACL tears. Only 13% of ACL tears were isolated, the rest being associated with meniscal tears. Forty-five percent of medial meniscal and 50% of lateral meniscal tears were associated with an ACL tear, and 94% of ACLs were torn when both menisci were torn.

The role of magnetic resonance imaging in giant cell tumor of bone.

In six cases of giant cell tumor the magnetic resonance (MR) images obtained with various pulse sequences and field strengths were compared to the corresponding computed tomography (CT) scans and plain roentgenograms. MRI was superior to CT and plain films in demonstrating areas of tissue inhomogeneity within the tumor as well as soft tissue extension. CT was superior in demonstrating cortical thinning. Multiplanar imaging capability and visualization of articular cartilage may demonstrate intra-articular tumor spread. The characteristic MRI findings with short TR/TE (T1-weighting) and long TR/TE (T2-weighting) are described. We also describe one case where serial MR scans were used to assess response to therapy.

Femoral neck torsion angle measurement by computed tomography.

To establish the accuracy and reproducibility of measuring femoral neck torsion angles (FNTA) on CT images, this angle was measured on 12 dry femora directly on the gross specimens, on plain radiographs, and on CT images. The selection of the CT level, both at the femoral neck and the condyles, that may affect the measurement of FNTA was analyzed. The CT measurements of FNTA were found to have a reproducibility of 2.5 and 0° mean offset error when compared with readings on plain radiographs. A new CT method was developed to measure this angle particularly in patients with coxa valga in whom this measurement is difficult if not impossible to accomplish by current methods. For this purpose composite CT images were made of the femoral head and the femoral shaft, immediately below the lesser trochanter. On these images the line connecting the centers of the femoral head and shaft were inferred to represent the cervical plane. In comparison with the standard CT method, this new method had the same reproducibility, although it slightly overestimated this angle by 2°. This degree of error is negligible when compared with the normal variations of this angle, which ranges from −20 to + 38°. Furthermore, it compares favorably with the limited accuracy of derotational osteotomy surgery.

Magnetic resonance imaging appearance of metastatic Merkel cell carcinoma to the sacrum and epidural space

Merkel cell carcinoma (MCC) is a rare malignant tumor of the skin and often is diagnosed histologically as lymphoma, melanoma and even metastatic small cell carcinoma of the lung (SCCL). Classified as a neuroendocrine tumor, clinically it originates in the head and neck region and may present with metastatic disease at the time of presentation [1]. Osseous involvement in the past has been described to involve regional facial bones only. We present the first reported MRI findings of distant osseous metastasis from a Merkel cell carcinoma to the lumbosacral spine with associated soft tissue and epidural involvement. Appropriate treatment and patient survival depend on prompt diagnostic imaging for establishment of metastatic disease. Previous reports have advocated CT for diagnosis and staging of distant metastases [2,3]. When spinal involvement is suspected, MRI may be a more suitable modality for assessment of the epidural space and appropriate staging and follow-up in such cases.

MRI appearance of clear cell hidradenoma.

Abstract We present the first reported MR imaging findings of a histologically proven clear cell hidradenoma. A fluid level was noted on all pulse sequences in this lesion, which demonstrated a prominent hemorrhagic component on sectioning. The presence of an enhancing nodule was also noted, differentiating this lesion from a post-traumatic hematoma. Fluid levels in a well-defined subcutaneous soft tissue mass should suggest the possibility of a hidradenoma.

Elastofibroma of the neck

Abstract Elastofibromas are benign lesions of the chest wall. We describe the first reported case of elastofibroma in the neck. Imaging features as well as location of the lesion were atypical. On computed tomography and magnetic resonance imaging the lesion contained a marked preponderance of fat, because the lesion arose within fat.

The effect on medical metal implants by magnetic fields of magnetic resonance imaging

Forces and torques, due to a 0.3 Tesla magnetic field were evaluated on ten hip prostheses and ten hemostat clips. Measurements were performed with an instrument utilizing the movement of a laser beam caused by the deflection of a canti-lever. The results indicate effects, if any, to be smaller than the instruments sensitivity which, at its highest, was 7 mg of force and 125 mg·cm of torque.

Spontaneous Osteonecrosis of the Knee

Abstract Six cases of spontaneous osteonecrosis of the medial femoral condyle were found during a 40-month period. While each patient presented with pain in the affected joint, it required two or more months for the characteristic flattening of the condyle and a condylar radiolucency with a surrounding sclerotic border to appear. 87mSr scintigrams showed increased uptake over the lesion. The patients ranged in age from 58 to 73 years. The condition may result in either complete resolution or considerable degenerative disease.

The effect of magnetic resonance imaging on metal spine implants.

In Part 1 of this study, the forces and torques exerted on metallic spine implants by a 0.3-T magnetic field were evaluated using a cantilever system sensitive to forces as low as 250 mg and torques as low as 4 g/cm. Results Indicated that the 0.3-T magnification field did not cause forces or torques that could be measured within this range. It is concluded that patients with spine implants may safely undergo magnetic resonance scanning. In Part 2, the magnetic resonance scans from 33 patients (61 studies) then were reviewed to determine which, if any, parameters could be adjusted to minimize artifact. Magnetic power, slice thickness, plane of scan, and pulse sequence were considered. Plane of scan was found to be the most significant parameter in achieving useful studies, with the sagittal plane being the preferred orientation. Scans of patients who had posterior wiring were more likely to be useful, while scans of patients with spinal rods usually showed a large amount of artifact.