Twenty patients with surgically proved neoplasms of the parotid gland were evaluated in order to compare contrast material-enhanced computed tomography (CT) and magnetic resonance (MR) imaging. In 14 patients both CT and MR imaging examinations were performed, while in six only MR imaging was performed. Because contrast resolution is better with MR imaging, it appears to be superior to CT in distinguishing the parotid gland from surrounding structures. Four intraparotid lesions were more conspicuous on T2-weighted MR images than on CT scans. MR imaging appears to be superior to CT for evaluating parotid masses and for distinguishing neoplasms of the parotid gland from those originating within the parapharyngeal space.
Seven patients with central nervous system neoplasia and leptomeningeal metastases, proved either at initial diagnosis or on follow-up with contrast material-enhanced computed tomography (CT), were evaluated with magnetic resonance (MR) imaging. In two patients, diffuse sulcal enhancement on CT scans was inapparent on T1- or T2-weighted MR images. Likewise, in four patients diffuse cisternal enhancement on CT scans was not identifiable with MR. Nodular or focal cisternal masses were identified with both CT and MR imaging in three patients; in two, however, MR imaging provided less information. Ependymal and subependymal metastases identified with CT (two patients) were indistinguishable on MR images from periventricular abnormalities of radiation therapy and/or hydrocephalus. These findings suggest that leptomeningeal metastasis may be so subtle or inapparent as to be overlooked with MR imaging alone. Thus, CT and MR imaging should be considered complementary techniques for initial diagnosis and follow-up of tumors with a propensity for leptomeningeal metastasis.
The differential diagnosis to consider in a patient presenting with a buccomasseteric region mass is rather lengthy. Precise preoperative localization of the mass and a determination of its extent and, it is hoped, histology will provide a most useful guide to the head and neck surgeon operating in this anatomically complex region. Part 1 of this article describes the computed tomographic anatomy of this region, while part 2 discusses pathologic changes. The clinical value of computed tomography as an imaging method for this region is emphasized.
MR images of three patients with Leigh9s disease (subacute necrotizing encephalomyelopathy) were compared with CT findings. In all patients typical lesions in the basal ganglia were identified with both MR and CT. In two patients MR permitted identification of additional lesions not detected with CT. In one patient progression of MR abnormalities over a 4-month period correlated well with clinical deterioration in neurologic status. T2-weighted images with a repetition time (TR) greater than 1950 msec and an echo time (TE) greater than or equal to 60 msec or inversion-recovery images with a 50-msec TE, 1213-msec inversion time, and 3000-msec TR were advantageous in identifying multiple necrotic lesions in the brainstem, deep gray matter, periventricular white matter, and cerebral cortex. In this series MR was more sensitive in detecting and localizing multifocal necrotic lesions of Leigh9s disease than CT was, and thus may be a useful diagnostic tool for patients with the appropriate clinical and laboratory abnormalities.
MR imaging of pituitary adenoma: CT, clinical, and surgical correlationPC Davis, JC Hoffman, Jr, T Spencer, GT Tindall and IF BraunAudio Available | Share
The myelographic evaluation of patients presenting with persistent or recurrent symptoms following surgery for an intrinsic spinal cord mass is difficult. Possible symptom-causing processes include tumor recurrence, intramedullary cyst formation, postirradiation effects, arachnoiditis, and spinal cord atrophy. Since tumor recurrence and syrinx formation may require further surgery, while the other entities generally do not, the distinction between these processes is clinically important. The authors have successfully employed commercially available high-resolution real-time ultrasound imaging systems to investigate a group of patients with these persistent or recurrent symptoms after surgery. The bony laminectomy defect provides an acoustic window for viewing intraspinal contents. Ultrasound can accurately differentiate between cystic and solid lesions and can clearly demonstrate whether a spinal cord is enlarged or atrophic.
The interpretation of conventional spin-echo and gradient-echo MR images of intracranial vascular lesions can be complex and ambiguous owing to variable effects on image intensity caused by flowing blood or thrombus. MR phase images, obtained simultaneously with conventional-magnitude images, are useful for evaluating proton motion (i.e., blood flow), and therefore can simplify the diagnosis of the presence or absence of thrombosis within a vascular structure or lesion. Fourteen patients with a variety of intracranial vascular abnormalities (aneurysms, superior sagittal sinus thrombosis, neoplasms adjacent to venous sinuses, and vascular malformations) were evaluated with conventional MR and phase imaging for the presence of blood flow. The phase images correlated with angiography in all cases. Phase imaging was not necessarily better than conventional spin-echo imaging in all cases, but it simplified the evaluation of thrombus vs blood flow in many. In three of five aneurysms, the phase images were diagnostic for evaluating lumen patency whereas the conventional images were ambiguous. Phase imaging was advantageous for detecting tumor invasion of the venous sinus when venous blood was enhanced by gadopentetate dimeglumine. A laminar flow phantom experiment determined the lower limits of sensitivity of phase imaging to be 0.5 cm/sec in the slice-select and 2.5 cm/sec in the read gradient directions. Phase imaging is a simple, reliable technique that can distinguish thrombosis from flowing blood within intracranial lesions. It is easily performed and adds no additional time to the MR examination.
