Search PubMed⌕ Search

Biomedical subjects

M T Modic

Publications and source records attributed to M T Modic.

At least 145 records · Page 8Linked to original sources
PubMedDate not supplied

Postoperative cervical spine: MR assessment.

The purpose of this article is to describe the variety of magnetic resonance (MR) findings in the cervical spine following anterior diskectomy and fusion (ADF), corpectomy, and postoperative complications. Toward that end, we retrospectively reviewed MR in 73 postoperative cervical spine patients and correlated the MR with their initial operative reports. Patients imaged within 1 month of ADF showed bone grafts as discrete rectangular areas of altered signal intensity within the central portions of the disk spaces. A spectrum of graft and vertebral body signal changes are seen up to 2 years following ADF. Patients studied greater than 2 years following ADF generally showed solid bony fusions without evidence of the graft or the original disk space. Bony canal stenosis at the operative site (19 of 73 cases) and disk herniations above or below the fusion sites (21 of 73 cases) were the most common postoperative findings. Hypertrophic bone was visualized as anterior extradural defect that was isointense (nine cases), hyperintense (four cases), or hypointense (eight cases) to the vertebral body on T1-weighted images. Disk herniations were evenly distributed above and below the fusion levels.

Bone Transplantation↗
PubMedDate not supplied

MR imaging with Gd-DTPA in leptomeningeal spread of lymphoma.

We describe the magnetic resonance (MR) plus Gd-diethylenetriamine pentaacetic acid (DTPA) findings in a patient with leptomeningeal spread of lymphoma. Gadolinium-DTPA aided in the diagnosis by offering additional information after noncontrast MR. Magnetic resonance with Gd-DTPA may well prove to be an important adjunct in the work-up of patients suspected of leptomeningeal spread of neoplasm.

Aged↗
PubMedDate not supplied

Three-dimensional FLASH imaging: applications with gadolinium-DTPA.

Sixteen patients with a variety of brain and spine tumors were examined with T1-weighted spin echo and three-dimensional (3D) fast low-angle shot (FLASH) (60 degree flip angle) techniques before and after administration of Gd-diethylenetriamine pentaacetic acid (DTPA) to assess the utility of volume imaging in parenchymal and dural disease. Reconstructions were performed on a Kontron MIP magnetic resonance (MR) workstation and compared with the corresponding spin echo images. Good 3D FLASH examinations (n = 9) were seen with a variety of echo times (6-17 ms) and repetition times (40-100 ms). Fair (n = 4) and poor (n = 3) examinations were usually associated with motion artifact, especially the coronal acquisitions. Spin echo images were all considered of good quality. An increase in confidence of diagnosis was seen in nine cases following contrast medium administration, based on either enhancement of an abnormality (n = 7) or failure of enhancement (n = 2). Three-dimensional FLASH imaging combined with Gd-DTPA holds promise to develop into a clinically valuable sequence allowing good patient throughput and ability to reconstruct in any plane and sensitivity to abnormalities of the blood-brain barrier or vascularity. However, some problems remain, including motion and susceptibility artifacts, long reconstruction time, and loss of resolution in reconstruction due to anisotropic volume.

Brain Neoplasms↗
PubMedDate not supplied

The spinal vacuum phenomenon: evaluation by gradient echo MR imaging.

To evaluate the ability of gradient echo MR to define the vacuum phenomena, 14 cadaveric lumbar spines were imaged by spin echo and gradient echo MR, CT, and plain radiography following injection of varying amounts of air into the intervertebral disks. Gradient echo MR was more sensitive than spin echo MR or plain radiography in detecting the intradiskal gas collections as small as 0.1 cc. Computed tomography was a sensitive as gradient echo MR. Plain radiography was the least sensitive modality. Increasing the echo time of the gradient echo technique increased the conspicuity of the gas collections due to magnetic susceptibility effects.

Air↗
PubMedDate not supplied

3D MR myelography.

A three-dimensional (3D) fast imaging with steady state precession sequence structured to maintain constant phase at the radiofrequency pulse, in the presence of motion, was employed to produce high signal intensity of the CSF relative to the extradural and neural structures in 170 consecutive spine MR examinations. In addition to displaying the resulting partitions as two-dimensional (2D) images, the acquisition was subjected to a maximum intensity projection postprocessing algorithm for viewing at multiple angles. The projected images demonstrated a global view of the thecal sac and the dural root sleeves. The global depiction of the thecal sac and root sleeves was equivalent to contrast myelography in 15 patients where comparisons were available. These projection myelographic images, used in conjunction with 2D and reformatted 3D cross-sectional images, may provide clinical services with enough information (in a format with which they are comfortable) to eventually eliminate the need for contrast myelography in the evaluation of extradural disease.

Humans↗
PubMedDate not supplied

Volume T1-weighted gradient echo MRI in multiple sclerosis patients.

Three-dimensional (3D) volume turbo fast low angle shot (FLASH) techniques have become available which produce heavily T1-weighted images, similar to inversion recovery scans, utilizing the appropriate flip angle and inversion time. The purpose of this study was to compare the sensitivity of a rapid volume gradient echo technique [3D magnetization prepared rapid acquisition gradient echo (MP RAGE)] in identifying multiple sclerosis (MS) plaques with a conventional T2-weighted spin echo (SE) sequence. Ten patients with clinical MS were evaluated. Patients underwent a routine examination consisting of an axial T2-weighted SE sequence (2,500,22/90) and a coronal 3D MP RAGE, 10/4/10, acquired as 128 two mm partitions. In six patients, area measurements of 22 plaques were determined on both the axial T2-weighted SE examinations and the axial reformatted MP RAGE examinations. The overall number of plaques utilizing each technique was approximately the same. One hundred twenty-two plaques were visualized for the 3D MP RAGE sequence, and 128 plaques for the T2-weighted SE sequence. There were differences in detection of plaques in different regions, with plaques in gray matter better demonstrated utilizing the conventional T2-weighted SE sequence. Plaques in the corpus callosum, pons, and brachia pontis were better demonstrated utilizing 3D MP RAGE. No significant difference was found between the areas measured on the MP RAGE sequence and on the T2-weighted SE sequence. Three-dimensional MP RAGE provides a sensitive and complementary method to conventional T2-weighted SE sequences in the evaluation of patients with MS.

Adult↗
PubMedDate not supplied

3D MPRAGE evaluation of the internal auditory canals.

A heavily T1-weighted three-dimensional (3D) gradient echo sequence utilizing a 180 degrees inversion pulse has become available for clinical use, called magnetization prepared rapid acquisition gradient echo (MPRAGE). With the appropriate choice of repetition time, echo time, flip angle, and inversion time (TI), T1-weighted imaging can be performed with excellent anatomic detail and a good signal-to-noise ratio. We performed an initial evaluation of this sequence for detection of abnormalities of the internal auditory canals compared with conventional spin echo (SE) imaging. Fifteen men and 15 women were evaluated. Diagnoses included normal (n = 15 patients), acoustic neuromas (n = 7 tumors in 4 patients), cerebellopontine angle meningiomas (n = 3), postoperative for acoustic neuroma without residual tumor (n = 2), postoperative with evidence of residual tumor (n = 3), glomus jugulare (n = 1), Bell palsy (n = 1), and vestibular enhancement of probable viral etiology (n = 1). The 3D MPRAGE study consisted of 128 coronal partitions, (10/4/1), 10 degrees flip angle, 130 x 256 matrix, 2 mm slice thickness. TI time of 350 ms, 1 s recovery time, and 5.43 min examination time. All enhancing lesions identified on the conventional SE T1-weighted imaging were also identified on the MPRAGE imaging. No diagnostic difference existed between the MPRAGE and conventional SE sequences when pathology was present, but the MPRAGE sequence did have poorer resolution in the axial reformats related to the 130 x 256 in-plane matrix. While not currently able to replace conventional two-dimensional SE imaging, 3D MPRAGE may provide a valuable adjunct to the routine imaging protocol. This technique could replace the coronal T1-weighted SE sequence and provide excellent gray-white differentiation and many contiguous thin sections without a great increase in overall examination time.

Cerebellopontine Angle↗
PubMedDate not supplied

Tissue segmentation for three-dimensional display of human spines.

This paper presents a morphological tissue segmentation technique for the three-dimensional visualization of the human spine. Magnetic resonance images of the human spine were obtained using motion-compensated fast imaging with steady-state free precession (FISP) pulse sequences. The images acquired with these sequences exhibit very high contrast between the bright cerebrospinal fluid (CSF) and the dark spinal cord and nerve roots. This phenomenon has enabled us to apply mathematical morphological processing techniques to extract the spinal nerve roots within the CSF space. The nerve roots were extracted from a set of slices and displayed in a three-dimensional format.

Cerebrospinal Fluid↗
PubMedDate not supplied

Intravenous digital subtraction angiography: an index of collateral cerebral blood flow in internal carotid artery occlusion.

The objective of this investigation was to correlate Xenon-133 inhalation rCBF measurements with the pattern of cortical arterial filling on intravenous DSA in 18 patients with unilateral internal carotid artery occlusion. Of 9 patients showing symmetrical filling of hemispheric cortical arteries, none showed an inter-hemispheric difference in rCBF ( delta Fg) greater than 10ml/100gm/min. Of 9 patients showing delayed cortical opacification ipsilateral to the internal artery occlusion, 3 showed a delta Fg greater than 10ml/100gm/min, 3 showed a delta Fg in the 7-10ml/100gm/min range, and 3 had a delta Fg less than 7ml/100gm/min. All patients with asymmetric abnormalities in the rCBF profile had the delayed pattern of cortical filling on DSA. The presence of symmetrical hemispheric opacification of cortical arteries on DSA indicates adequate interhemispheric redistribution of rCBF and patent inter-hemispheric collateral channels, but not necessarily normal cerebral blood flow. The presence of delayed cortical arterial opacification on the side of internal carotid artery occlusion does not necessarily imply significant inter-hemispheric rCBF differences, nor does it rule out a normal rCBF. The presence of bilateral reduction of rCBF and symmetrical cortical artery filling on DSA may represent an "interhemispheric steal".

Arterial Occlusive Diseases↗
PubMedDate not supplied

Intracranial internal carotid artery stenosis: longterm prognosis.

Sixty-six patients with greater than or equal to 50% stenosis of an intracranial internal carotid artery (IICA) were followed-up for an average of 3.9 years. Eighteen patients (27.3%) experienced ischemic events; 8 (12.1%) had isolated TIA and 10 (15.2%) a stroke. The observed stroke rate for patients 35 years and older are 13 times the expected infarction rate for a normal population. Patients with tandem extracranial stenosis had a greater risk of stroke than patients with isolated IICA stenosis. Thirty-three patients (50%) died during follow-up and 55% of all deaths were cardiac related. The observed 5 year survival rate was 60% compared to an expected rate of 87%. Patients with IICA stenosis had a higher risk of stroke and death compared to a previously reported referral population with ICA occlusion. IICA stenosis is a marker of extensive cerebrovascular and systemic atherosclerotic disease, especially coronary artery disease.

Adult↗
PubMedDate not supplied

Sector computerized tomography of temporal bone and base of skull.

The field of computerized tomography (CT) scanning has been one of the great medical advances of the 20th century. The field is developing rapidly with new hardware and software becoming available on a monthly basis. At the Cleveland Clinic Foundation, patients have been studied by using a sector computerized tomography scanner that has the capability of not only improved spatial resolution but also software programs, with the ability to reconstruct data using different algorithms. This versatility in reconstructing the raw data has resulted in a remarkable improvement in the ability to study the temporal bone and the base of the skull. This paper will present technical data in reference to this new generation of scanner and also show examples of the type data that are becoming available to the otolaryngologist studying lesions of the base skull and temporal bone.

Cranial Fossa, Posterior↗
PubMedDate not supplied

Gd-DTPA-enhanced 3D MR imaging of cervical degenerative disk disease: initial experience.

PURPOSE: To assess whether a single enhanced T1-weighted gradient echo volume sequence, with the appropriate reformatted images, could be equivalent to a more conventional 2D set of MR sequences for the evaluation of cervical extradural degenerative disk disease (bony canal and foraminal stenosis; disk herniation). MATERIALS AND METHODS: Sixty-one patients evaluated for extradural degenerative disease by MR were imaged with a "standard" MR examination (Sagittal T1-weighted spin echo, axial low flip angle gradient echo), were then given 0.1 mmol/kg Gd-DTPA intravenously, and reimaged with either a 3D FLASH (fast low angle shot), TR 40/TE 7/1 excitation), 40 degree flip angle, acquired as 64, 2-mm sagittal partitions, or a 3D turbo FLASH (MP RAGE-magnetization prepared rapid acquisition gradient echo) (10/4/1), 10 degree flip angle acquired as 128, 2-mm coronal partitions. The volume sequences were reconstructed in the axial plane, and right and left 45 degree oblique coronal planes. The two sets of examinations (standard vs volume) were prospectively interpreted by two neuroradiologists for quality of examination, and location, type, and severity of extradural degenerative disease in a random, blinded, independent fashion. RESULTS: There was no significant difference between the standard examination and the 3D MP RAGE for central extradural disease. The 3D FLASH examination was significantly worse than the standard examination in identification of central extradural disease, with an average of 21 herniations not identified, or underestimated in size. Neither the 3D FLASH, nor the 3D MP RAGE examinations showed any significant improvement compared to the routine 2D examination for the location and severity of foraminal disease. CONCLUSION: If extradural degenerative disk disease is being evaluated, then a single enhanced 3D T1-weighted imaging sequence taking 6 minutes can be equivalent to a routine set of mixed 2D spin echo and low flip angle gradient echo sequences.

Cervical Vertebrae↗
PubMedDate not supplied

MR imaging of metastatic GI adenocarcinoma in brain.

PURPOSE: To investigate an observed preferential T2-shortening effect seen in patients with intracerebral metastases from adenocarcinoma of the GI tract. METHODS: Ten patients with intracerebral metastases from adenocarcinoma of the GI tract were evaluated with MR imaging with CT and histopathologic correlation. RESULTS: Nine of 10 patients demonstrated intracranial masses with decreased signal intensity on T2-weighted images. T1-weighted images showed decreased or isointense signal in all cases. Special histologic staining was performed in four of 10 cases, all of which were positive for increased protein (mucin) with no evidence of blood products or calcium. CONCLUSION: We propose that the observed preferential T2-shortening effect is secondary to slowing of rotational and translational proton motion caused by increased protein concentration in the form of mucin.

Adenocarcinoma↗
PubMedDate not supplied

The value of fast gradient-echo MR sequences in the evaluation of brain disease.

One-hundred-fifteen patients thought to have intracranial disease were studied with various two-dimensional short repetition time, partial-flip-angle gradient-echo techniques: at 1.0 T, fast low-angle short (FLASH) at 10 degrees and 30 degrees and fast imaging with steady-state precession (FISP) at 60 degrees; at 1.5 T, FLASH 10 degrees, 30 degrees, and 60 degrees, FISP 60 degrees, and contrast-enhanced fast steady state at 60 degrees. These sequences were compared with a T2-weighted spin-echo sequence to determine the relative sensitivities of these techniques in detecting parenchymal lesions. Except for hemorrhagic lesions a substantial number of abnormalities were either not visible or poorly seen on the partial-flip-angle gradient-echo sequences. Minimizing echo time (6-9 msec) to decrease magnetic susceptibility effects did not improve lesion detection. Current usage of two-dimensional gradient-echo techniques for lesion detection is limited, except when calcification or hemorrhage is involved. Their utility may be expanded via the incorporation of three-dimensional techniques and IV contrast agents.

Brain Diseases↗
PubMedDate not supplied

MR imaging of the postoperative lumbar spine: assessment with gadopentetate dimeglumine.

This study defines the accuracy of gadopentetate-dimeglumine-enhanced MR imaging in patients with failed back surgery syndrome by comparing the imaging studies with surgical findings in a large patient population. From June 1988 to March 1989, 193 postoperative patients had MR imaging of the lumbar spine both with and without contrast administration. Of this group, 27 had repeat surgery at 31 levels: these patients comprise the study group. Postcontrast MR diagnoses were as follows: scar only (n = 4), disk only (n = 13), scar and disk (n = 9), and no aberrant epidural tissue (n = 5). Surgical diagnoses differed from the MR diagnoses in two patients at two levels. In one patient, disk was diagnosed on MR while osteophyte was present at surgery. In the other patient, scar only was diagnosed by MR but disk and scar were present at surgery. These data, when combined with the authors' previous experience, give pre- and postcontrast MR a 96% accuracy in differentiating scar from disk in 44 patients at 50 reoperated levels. For patients 6 or more weeks past surgery, sagittal and axial T1-weighted MR imaging before and after administration of gadopentetate dimeglumine is an effective method of evaluating the postoperative lumbar spine.

Adult↗
PubMedDate not supplied

Gd-DTPA enhancement of posterior epidural scar: an experimental model.

Because of the tremendous clinical and physiological importance of anterior epidural scar, an easily produced and reproducible model to assess potential pathways for lessening its formation is a necessity. We speculated whether posterior epidural scar (produced by the less complex surgery of laminectomy alone) could be considered equivalent to anterior scar from an imaging standpoint; that is, enhancement following Gd-DTPA irrespective of scar age. Posterior epidural scar in dogs showed the highest degree of enhancement 1 month after surgery, with a rapid decline thereafter out to 4 months postsurgery to a level equivalent to that of paraspinal muscle. Gd-153-DTPA time/activity curves paralleled the Gd-DTPA findings. Light microscopy showed granulation tissue after 1 month, and mature scar with large amounts of collagen 4 months after surgery. Electron microscopy showed tight capillary endothelial junctions. An appropriate model for epidural scar, which has imaging characteristics similar to human anterior scar, necessitates an extensive lumbar laminectomy with anterior epidural dissection. A simple laminectomy, while easily performed, does not provide a physiologically correct time course of enhancement.

Animals↗
PubMedDate not supplied

Assessment of extradural degenerative disease with Gd-DTPA-enhanced MR imaging: correlation with surgical and pathologic findings.

To test whether gadolinium-DTPA-enhanced MR would increase the conspicuity of extradural degenerative disease in the previously unoperated patient, we prospectively studied a group of 30 patients with symptoms suggestive of disk disease. Surgical findings and pathologic correlations were used as an objective measure of accuracy. Gadolinium-DTPA increased the confidence of diagnosis at one of eight operated cervical levels (six patients) and changed the diagnosis from extradural degenerative disease to tumor in one patient. The mechanism of enhancement of the epidural space and peridiskal region appears to be related to accumulation of contrast material within the epidural venous plexus, as well as to epidural fibrosis associated with disk disruption and herniation. While the immediate clinical utility of gadolinium-DTPA for morphologic analysis seems limited to difficult cervical spine cases, the presence of enhancement as a marker of epidural fibrosis and attempted healing may prove to be of great importance in studying the natural history and basic pathophysiology of degenerative disk disease.

Adult↗