Sublethal exposure to microwave radar.
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Adult↗
Biomedical subjects
R M Quencer
Publications and source records attributed to R M Quencer.
Percutaneous needle evaluation of intradural extramedullary lesions of the lumbar spine.
A total of eight patients in whom five intradural extramedullary lesions and three epidural lesions were present were evaluated by percutaneous needle biopsy. In four patients the level of aspiration biopsy was determined using the initial myelogram and in those patients fluoroscopic guided percutaneous needle biopsies were performed. Three of these patients had large intradural extramedullary masses (above 1 cm); one patient had an epidural lesion. Diagnostic material was obtained in all cases (medulloblastoma, astrocytoma, small cell carcinoma, adenocarcinoma). Immediate post procedure CT and clinical followup showed no complications. In three patients with small lesions (below 1 cm), post myelographic CT was used to determine the level of aspiration. Post myelographic CT showed an intradural extramedullary mass in one patient and epidural lesions in two cases. Plain CT showed a high attenuation lesion in one patient. CT guided percutaneous needle biopsies in these four patients yielded diagnostic specimens (neurofibroma, uroepithelial carcinoma, hematoma, Thorotrast deposit). Clinical follow up showed no complications. Our experience indicates that percutaneous needle biopsy of intradural extramedullary and epidural lesions of the lumbar spine is safe and efficacious. Depending upon the size of the lesions, myelography or CT can be utilized to determine the level of aspiration.
Adult↗
MR characterization of brain and brain tumor response to radiotherapy.
This paper describes our experience in using the T1 and T2 relaxation times for quantitative evaluation of brain and brain tumor response to radiation therapy. Twenty-two computed T1 and 22 computed T2 images were obtained from 66 routine inversion-recovery and spin-echo magnetic resonance (MR) brain scans. The relaxation times of the brain tissues, determined from the computed images, were examined as a function of the absorbed dose. Statistical evaluation of the results showed no significant difference between the relaxation times of irradiated and not irradiated tissues, including tumor and normal white matter. Influence of the magnetic field strength and imaging techniques on the computed T1 and T2 values was confirmed. We conclude that the relaxation time values, as obtained today using conventional MR scanner and standard software, are not specific enough to warrant a correct assessment of the acute radiation effect on the brain tissues.
Adolescent↗
Association of heterotopic gray matter with seizures: MR imaging. Work in progress.
Heterotopic gray matter, which previously had been associated with severe congenital malformations of the brain and developmental delay, was found without these associated conditions. The authors found ten cases of heterotopic gray matter on magnetic resonance (MR) images. The lesions had a signal intensity that was isointense compared with that of gray matter on T1, spin-density, and T2-weighted images. Nine of the ten cases were associated with a seizure disorder. The tenth case, discovered during a workup for metastatic lung disease, was confirmed with pathologic studies. Heterotopic gray matter is the presence of cortical neurons in an abnormal location, which may be periventricular (nodular) or within the white matter (laminar). A knowledge of heterotopic gray matter and its association with seizures may prevent the misinterpretation of findings on MR images.
Adolescent↗
Spinal infection: evaluation with MR imaging and intraoperative US.
Magnetic resonance (MR) images of the spine and/or intraoperative spinal ultrasound (US) in 24 patients with spinal infections were reviewed and correlated with clinical and pathologic data to determine their diagnostic value. In disk space infection with osteomyelitis and in retrospinal abscess, MR images showed characteristic findings, whereas in myelitis, MR images demonstrated nonspecific abnormalities. The appearance on MR images of epidural abscesses ranged from clearly identifiable extradural masses with high-intensity signal on spin-echo T2-weighted images to extensive inhomogeneous collections of mixed signal intensities, difficult to distinguish from adjacent meningitis. Myelography with high-resolution computed tomography (CT) and intraoperative spinal US was superior to MR imaging in demonstrating epidural abscesses when there was concomitant meningitis. With intraoperative spinal US, epidural abscesses could be located and their decompression monitored. MR imaging is recommended as the initial screening procedure in spinal infection; in those few patients with nondiagnostic MR images, myelography with high-resolution CT should be the supplementary study. If surgery is planned, intraoperative spinal US should be used.
Abscess↗
Neuroimaging and head injuries: where we've been--where we're going.
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Brain↗
Syringomyelia as a consequence of compressive extramedullary lesions: postoperative clinical and radiological manifestations.
MR imaging was performed to determine the cause of the onset of new neurologic symptoms in five patients who had previously undergone surgical excision of extramedullary masses. Syringomyelia and the absence of recurrent or residual lesions were documented in all cases. Three patients showed long cysts (multiseptated in two and smooth in one) with low signal intensity on both T1- and T2-weighted images. The flow-void phenomenon related to fluid motion in these three cysts, which were enlarging clinically, was responsible for the hypointensity on the T2-weighted images. In two patients the fluid within the lesions behaved similarly to normal nonpulsatile CSF and may have represented syrinx cavities in a state of "arrested growth." Three patients had surgical decompression under real-time intraoperative sonographic control, which showed the presence of intramedullary cyst-fluid pulsations in two cases and the absence of cyst-fluid pulsations in one case. These sonographic observations correlated with the MR findings. We postulate that these syrinx cavities form as a result both of the effect that the original extramedullary lesion had upon the underlying spinal cord and the subsequent postoperative alterations in the CSF dynamics at the level of prior surgery. Syringomyelia should be considered in patients with recurrent or new symptoms who previously had surgery for extramedullary lesions.
Adult↗
Improved MR imaging of the brain by using compensating gradients to suppress motion-induced artifacts.
Sixty patients were examined with and without extra gradient pulses, which compensate for motion-induced phase errors, in order to determine the effect those gradients had in suppressing the motion artifacts frequently present in the brainstem, temporal lobes, and basal ganglionic regions on routine T2-weighted brain MR imaging. Two comparative studies were performed: (1) in 50 patients the motion-artifact suppression technique (MAST) was compared with a single-echo MR examination, and (2) in 10 patients the MAST technique was compared with the second echo of a symmetric dual-echo sequence. In the first study 39 patients were examined at 1.5 T and 11 patients were examined at 0.5 T with the same pulse sequences. We found that MAST resulted in a significant improvement of image quality in 24 of 39 patients on the high-field-strength system and in two of 11 patients on the mid-field-strength system. In the second study, we found that in four of the 10 patients, MAST resulted in a suppression of artifacts greater than that achieved by even-echo rephasing alone. With MAST, artifacts were eliminated that not only obscured normal structures but that could have left doubt about the presence of a true signal abnormality. There was, however, marked suppression of the CSF flow-void phenomenon and increased signal from flowing blood, particularly in the cortical veins and dural sinuses. Because of this, the use of additional pulse sequences in which these motion-compensating gradients were not used was necessary under certain clinical circumstances. We conclude that, with these motion-compensating gradients, artifacts are reduced or eliminated, and a marked improvement in image quality can be obtained without the need for cardiac gating.
Adolescent↗
CT, MR, and pathology in HIV encephalitis and meningitis.
The value and limitations of CT and MR in human immunodeficiency virus (HIV) infection of the brain was determined by a retrospective analysis of the CT scans (22) and MR images (7) in 22 patients with pathologically proved HIV encephalitis (21) or meningitis (1). Our clinical-radiologic-pathologic correlation suggested that, especially in the early stages of the disease, CT and MR were relatively insensitive in detecting the primary changes of HIV encephalitis. The multiple bilateral diffuse microscopic glial nodules with multinucleated giant cells of HIV found at autopsy in both gray and white matter were usually not directly visualized by either CT or MR. Secondary, nonspecific changes, however, were seen. These included cortical atrophy, found in virtually all patients with HIV encephalitis, and HIV-induced foci of demyelination found in the minority of cases. On CT the latter were seen in the white matter as nonenhancing, nonmass-producing areas of low density; on MR they were seen as frequently progressive high-intensity signal abnormalities on T2-weighted images, usually in the periventricular white matter and centrum semiovale. MR was more sensitive in detecting these demyelinative lesions than was CT. The clinical diagnosis of HIV encephalitis usually antedated the radiographic diagnosis. In HIV meningitis, contrast CT was more definitive than MR, showing striking enhancement of the subarachnoid spaces, although MR was more sensitive in detecting the secondary parenchymal changes.
Acquired Immunodeficiency Syndrome↗
Congenital glaucoma and buphthalmos in a child with neurofibromatosis.
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Exophthalmos↗
The injured spinal cord. Evaluation with magnetic resonance and intraoperative sonography.
MR is now the study of choice in evaluating both the acutely and previously injured spinal cord. A number of crucial diagnoses can be made with MR that are difficult to obtain otherwise. The discovery of acute disk herniation in association with a fracture/dislocation may indicate the need to remove the disk and stabilize the patient on a relatively urgent basis, and the approach to the stabilization procedure (either anterior or posterior) can be determined by the MR findings. Hemorrhage outside the cord may require immediate surgical attention, and identification of abnormal signals from the cord itself consistent with hemorrhage or edema may help to explain the patient's clinical status. Our experience indicates that obtaining an MR in acutely injured patients who have incomplete injuries is particularly helpful in their surgical management. The presence of intramedullary or extramedullary cysts in the previously injured spine can explain a worsening clinical picture and direct the surgeon to the proper area (or areas) for decompression. Flow-sensitive studies currently under evaluation are giving a greater insight into the dynamics of these cysts. Late decompression of cord tissue and roots requires accurate preoperative MR evaluation of possible bone or disk impingement on neural tissue. In surgery of both the acute and chronically injured spine, intraoperative sonography plays a crucial role. The adequate shunting of intramedullary and subarachnoid cysts, the confirmation of the efficaciously placed Harrington rods, the demonstration of removal of compressive bone or disk fragments, and the uncovering of important but unanticipated abnormalities such as subligamentous hematoma or an incidentally herniated disk all attest to sonography's value in the operating room. MR preoperatively and sonography intraoperatively are important tools utilized in the care of spine-injured patients.
Acute Disease↗
Motion artifacts in brain and spine MR.
As a result of the effects of cerebrospinal fluid and blood motion, motion artifacts are common in brain and spine MR imaging. These artifacts, which are most common on T2-weighted spin-echo sequences, show up as streaking and ghosting in the phase-encoding (PE) direction (PE artifacts) and as loss of signal from flowing material (flow void). A review of the physical and physiologic causes of these artifacts and a review and explanation of several techniques that are useful in reducing or eliminating them are presented in this article.
Blood Circulation↗
Case report 415: Osteochondroma of the cervical spine.
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Adult↗
Intraoperative sonography in spinal dysraphism and syringohydromyelia.
The use of intraoperative sonography was analyzed in 24 patients with spinal dysraphism and syringohydromyelia in order to determine the role of real-time sonography in the surgical management of these patients. Specific diagnoses included tethered cord (nine), syringohydromyelia (seven), congenital tumor unassociated with a tethered cord (four), diastematomyelia (three), and occult sacral meningocele (one). Intraoperative sonography determined the exact relationship of congenital tumors to the cord before opening the dura, which allowed a more precise approach to the mass. Intraoperative sonography identified the lower end of the syrinx cavities, which allowed optimal catheter placement. Fibroglial scar tissue, which may compartmentalize these syrinx cavities, was clearly shown, and the efficacy of shunt catheter placement was immediately determined. In diastematomyelia, intraoperative sonography identified the relationship of the hemicords to bony, cartilaginous, and/or fibrous septa and demonstrated the effect on the tethered hemicords of removing these septa and constructing a single dural sac from the two dural sacs that had enclosed the hemicords. Since significant surgical decisions are based on these sonographic observations, the authors urge widespread use of intraoperative sonography in patients with spinal dysraphism and syringohydromyelia.
Humans↗
Intramedullary spinal cord metastases, mainly of nonneurogenic origin.
The clinical data and imaging studies of 12 patients with intramedullary metastases were reviewed retrospectively to see if these lesions had a typical radiographic appearance and to determine the sensitivity of the various radiologic examinations. The lesions were identified antemortem by either myelography, CT, MR, and/or intraoperative spinal sonography (IOSS). Final diagnosis was based on biopsy material from either the spinal cord lesion, another metastatic site, and/or the primary tumor. Ten patients had primary tumors located outside the central nervous system, while only two patients had primary brain tumors. Metrizamide myelography and CT demonstrated a definite intramedullary mass in nine of 11 patients. In five patients the mass was relatively small, well-defined, single, and resembled a primary spinal cord neoplasm. In the other four patients, longer and sometimes several segments of the cord were involved. These appeared irregular and nodular and were often associated with intradural lesions at separate sites. MR detected not only enlargement and abnormal signal in the cord but also clinically unsuspected brain lesions. IOSS localized lesions for biopsy and monitored tumor resection. These various imaging procedures showed that cord metastases were often more extensive than anticipated clinically. Spread of tumor into the spinal and intracranial subarachnoid space was common. Imaging of the entire spinal canal and brain, preferably with MR, is therefore recommended to aid in diagnosis, prognosis, and treatment.
Adult↗
Intraoperative cranial sonography.
The use of real time ultrasound in the neurosurgical operating room can enhance the ability to localize intracerebral masses, allow accurate needle biopsies, diminish the amount of potential damage to normal brain tissue, show the results of tumor resection, and help in the placement of ventricular and cyst shunts. The end result makes the surgical procedure faster, safer, and more accurate.
Adult↗
Intraoperative sonography in spinal surgery: current state of the art.
Intraoperative spinal sonography (IOSS) has significant impact on the surgical management of spinal lesions. This paper describes the techniques involved, illustrates the sonographic anatomy of the spinal canal and its contents and discusses the role of IOSS in the surgical management of spinal trauma, spinal tumors, spinal stenosis and congenital anomalies.
Adult↗