Faculty Bibliography

The ability to detect acute hemorrhage by magnetic resonance (MR) is related to the oxygen saturation of hemoglobin. This experiment measured the relaxation times of solutions of cerebrospinal fluid containing a 5 per cent hematocrit at various pO2's on a 1.4 tesla (T) MR imaging system. The results demonstrate that the state of oxygen saturation of hemoglobin determines the extent of T2 relaxation at this field strength. The T2 relaxation rate varies quadratically with the concentration of deoxyhemoglobin. There were no significant changes in the T1 relaxation rate with variations in pO2. These findings may, in part, explain the inability of MR to detect subarachnoid hemorrhage, and the MR appearance of blood in intratumoral hemorrhage, hemorrhagic cortical infarction and neonatal hemorrhage

There is a stereotyped progression in the appearance of hemorrhage or thrombosis in magnetic resonance imaging performed at 1.5 tesla (T). This progression begins with low intensity on T2 weighted images (WI), and progresses to high intensity on T1 and T2 WI associated eventually, in some cases, with peripheral low intensity on T2 WI. Depending upon the etiology and location of hemorrhage or thrombosis the latter hypointensity on T2 WI may or may not be present. Hemorrhages occurring in regions of the brain not having an intact blood-brain barrier do not usually display persistence of low intensity. Regardless of etiology, consistent patterns in the evolution of hemorrhage may be observed on MR

Magnetic resonance imaging (MRI) characterized intrasinus hemorrhage in 8 out of 10 patients with computed tomography (CT) evidence of post-traumatic sinus opacification. Fractures of sinus walls were demonstrated as disruptions in the hypointense line of the bony wall, as displacement of this line, or by increased signal from blood or sinus effusion within the fracture. Seven patients with fractures of the temporal bone were more difficult to evaluate because of the hypointensity of air trapped within the fracture line mimicing the bony wall and that within the middle ear mimicing the ossicles; 1.5 tesla MR proved superior to CT in demonstrating associated extra- and intracerebral hemorrhage

Eight acoustic neurinomas were studied with magnetic resonance imaging (MRI) at 1.5 tesla utilizing spin-echo T1 and T2 weighted images (WI). T1 WI identified the tumors best and provided more exacting anatomic relationships particularly for small lesions than did T2 WI. Intracanalicular tumors are well defined. All tumors were hypointense on T1 WI but were usually heterogeneous and had variable intensity on T2 WI. Several lesions became obscured on T2 WI because of isointensity with the adjacent cerebellum or CSF. High signal to noise ratio at 1.5 tesla permits thin section imaging (3 mm) at relatively short imaging times. T1 MRI was considerably superior to CT for the detection and anatomic definition of acoustic neurinomas

Seventeen patients were found to have involvement of the dural venous sinuses on magnetic resonance imaging (MRI). In 7, there was tumor invasion through the dural coverings and in 10 thrombosis occurred as a result of various causes. MRI shows tumor in the sinus as a signal producing mass replacing the normal hypointensity of rapidly flowing blood. Disruption of the hypointense leaves of the enveloping dura is also well shown by MRI. Intravascular clotting, whether in the chemical state of deoxyhemoglobin or intra- or extracellular methemoglobin can be characterized by MRI operating at high field (1.5 tesla). MRI is now the non-invasive diagnostic modality of choice in evaluation of the dural venous sinuses

Twenty patients with congenital cerebral aneurysms, studied on a 1.5 tesla MR unit, were also evaluated by angiography and/or computed tomography (CT) in order to establish the relative sensitivity of magnetic resonance imaging (MRI) in the demonstration of such aneurysms. Of the 27 aneurysms found on MRI, all but 4 were seen without the aid of the angiographic study. The four seen in retrospect included 3 out of 4 in the smallest size category (less than 5 x 5 mm) and one in next larger (5 x 5 mm to 10 x 10 mm). When more than one aneurysm was present or when an aneurysm and an arteriovenous malformation was present, MRI proved to be useful in demonstrating which bled. The presence of both subacute and acute clot identified the lesions that had bled

A case report of clear cell sarcoma of the tendinous portion of the quadriceps in the knee joint of a 33-year-old female is presented. This insidious, usually painless malignant tumor is often misdiagnosed and may be referred to the sports medicine specialist as a sport-related injury. The duration of symptoms and the size of the lesion are important prognostic factors. Wide excision or radical surgery is necessary to cure such tumors. With improved reconstructive techniques, including free vascularized myocutaneous flaps, limb-sparing surgery is now possible.

Twenty intracranial hematomas between 1 day and over 1 year old were imaged using magnetic resonance at 1.5 T, with T1- and T2-weighted spin-echo pulse sequences. Characteristic intensity patterns were observed in the evolution of the hematomas, which could be staged as acute (less than 1 week old), subacute (greater than 1 week and less than 1 month old), or chronic (greater than 1 month old). Acute hematomas were characterized by central hypointensity on T2-weighted images (WIs). Subacute hematomas had peripheral hyperintensity on T1-WIs and then on T2-WIs. This hyperintensity proceeded to fill in the hematoma in the chronic stage. In subacute and chronic hematomas, there was hypointensity on T2-WIs in the immediately adjacent part of the brain. On T2-WIs of acute and subacute hematomas, the nearby white matter was characterized by hyperintensity, consistent with edema. A different mechanism is proposed for each of the three characteristic intensity patterns. Two of these mechanisms increase in proportion to the square of the magnetic field magnitude

Nine lesions, four ocular (three melanomas, one hemangioma) and five orbital (two perioptic meningiomas, one hemangioma, one pseudotumor, one mucocele), were evaluated by magnetic resonance surface coil imaging at 1.5 T. Small ocular lesions with 3.9-4.5-mm-elevation were demonstrated. The use of two different pulse sequences resulted in separation of melanoma from adjacent retinal detachment. Contrast obtained between orbital lesions and the adjacent normal structures was better than that demonstrated with high-resolution computed tomography

A case of superficial siderosis of the central nervous system secondary to bleeding from an ependymoma is presented. High-field magnetic resonance imaging showed marginal hypointensity of the cervical cord, medulla oblongata, pons, mesencephalon, anterior cerebellar and basal cerebral surfaces, and cranial nerves (II, V, VIII). These findings were evident in the T2 weighted images