Biomedical subjects

D R Enzmann

Publications and source records attributed to D R Enzmann.

At least 73 records · Page 4Linked to original sources

PubMed1987

Cervical spine MR imaging: generating high-signal CSF in sagittal and axial images.

Three magnetic resonance (MR) imaging techniques were compared as to their ability to generate images with high-signal cerebrospinal fluid (CSF) to provide a high-contrast CSF-dura interface. The three techniques were CSF gating to the peripheral pulse, selective saturation recovery with gradient refocusing (SSRGR), and gradient recalled acquisition in the steady state (GRASS). In sagittal views of the cervical spine, CSF gating proved to be a reliable technique for producing images with uniform high-signal CSF in a single-section or multi-section mode. In axial views, SSRGR and GRASS techniques were more consistent than CSF gating in producing high-signal CSF images, especially in a multisection mode. Although axial image quality was nearly equivalent for SSRGR and GRASS techniques, the latter was clinically more efficient because of shorter imaging times. These methods of imaging in the cervical spine yield sufficient CSF-dura contrast and spatial resolution to be of use in the diagnosis of cervical disk disease.

Cerebrospinal Fluid↗

PubMed1987

Optimizing conventional MR imaging of the spine.

With the use of conventional spin-echo pulse sequences with a long repetition time (TR), the echo time (TE) and the number of echoes were varied to minimize cerebrospinal fluid (CSF) flow artifacts in a spine phantom and in cervical spines of three volunteers. The following echo trains were compared in both axial and sagittal planes with a TR of 2,000 msec: TE of 25, 80 msec ("asymmetric"); TE of 40, 80 msec ("symmetric long TE"); and TE of 20, 40, 60, and 80 msec ("symmetric short TE"). Variable degrees of even-echo rephasing of CSF flow artifacts were observed during sagittal but not axial imaging, depending on the echo train used. Even-echo rephasing was most complete with the symmetric short-TE echo train, less complete with the symmetric long-TE echo train, and absent with the asymmetric echo train. Switching the orientation of the phase and frequency encoding gradients and slightly modifying TR on the basis of the heart rate further improved image quality. The results suggest that a symmetric short-TE echo train may be used to provide velocity compensation (similar to that observed with rephasing gradients) on even echoes of conventional spin-echo pulse sequences during spine imaging.

Cerebrospinal Fluid↗

PubMed1987

CSF-gated MR imaging of the spine: theory and clinical implementation.

A spine phantom and cervical spines of seven volunteers were studied with cerebrospinal fluid (CSF)-gated magnetic resonance imaging to optimize acquisition factors reducing CSF flow artifacts. Peripheral gating was performed with either an infrared reflectance photoplethysmograph or peripheral arterial Doppler signal. The effects of effective repetition time, echo train, trigger delay, number of sections, and imaging plane on image quality were evaluated. Gated imaging of oscillatory CSF motion simulated constant-velocity flow and reduced CSF flow artifacts caused by cardiac-dependent temporal phase-shift effects. Velocity compensation on sagittal even-echo images with a symmetric short-echo time echo train reduced the remaining CSF flow artifacts caused by spatial phase-shift effects. Overall gated imaging time was not increased compared with nongated imaging and was reduced when improved image quality permitted the use of fewer excitations. These results suggest that the combination of CSF gating and flow compensation is clinically useful and efficient because it improves image quality without prolonging imaging time.

Cerebrospinal Fluid↗

PubMed1987

Potential false-negative MR images of the thoracic spine in disk disease with switching of phase- and frequency-encoding gradients.

Two patients with thoracic disk protrusion were evaluated with magnetic resonance imaging. A T1-weighted spin-echo sequence was used, with and without switching of the phase- and frequency-encoding gradients. Both disks were well delineated when the frequency-encoding gradient was parallel to the spinal axis. When the gradients were switched (with the phase-encoding gradient parallel to the spinal axis), both herniated disks were partially obscured by a posteriorly displaced fat signal from marrow, caused by a chemical shift artifact. In addition, the anterior subarachnoid space appeared falsely narrowed, and the cerebrospinal fluid (CSF) signal intensity was increased, which reduced the CSF-cord contrast. These findings suggest that switching the orientation of the frequency- and phase-encoding gradients may result in false-negative T1-weighted sagittal images of the thoracic spine.

Adult↗

PubMed1987

Dyke award. Imaging of spinal CSF pulsation by 2DFT MR: significance during clinical imaging.

Understanding the MR appearance of spinal CSF is important in interpreting clinical spine images because the diagnosis of spinal pathology requires an accurate delineation of spinal CSF from spinal cord and thecal sac. During conventional 2DFT MR imaging of the spine, CSF pulsation caused two interdependent flow phenomena, signal loss and phase-shift images. Signal loss was observed as decreased signal intensity arising from pulsatile spinal CSF. Phase-shift images were observed as signal intensity arising from and morphologically identical to the spinal subarachnoid space but symmetrically displaced from it along the phase-encoding axis of MR images, either added to or subtracted from stationary signal intensity. These phenomena were common, occurring in most cervical and thoracic long-TR images. Both phenomena were less apparent in the lumbar region in most cases. CSF pulsation flow phenomena decreased CSF-spinal cord and CSF-thecal sac conspicuity, thereby obscuring normal and pathologic anatomy and, at times, simulating pathology. The areas of signal loss showed variable but characteristic patterns in the cervical and thoracic spine corresponding to regions of greatest flow. Signal loss in the axial plane was more pronounced when thin slices were used. Phase-shift images degraded overall image quality secondary to spatial mismapping of spinal CSF signal intensity. With the use of CSF gating, both signal loss and phase-shift images were eliminated. Understanding these features will be important in the accurate interpretation of MR spine images because analysis of CSF pulsation flow phenomena provides physiologic and pathologic information, and awareness of their existence avoids diagnostic confusion.

Adolescent↗

PubMed1987

Dyke award. Harmonic modulation of proton MR precessional phase by pulsatile motion: origin of spinal CSF flow phenomena.

The effects of pulsatile motion on MR imaging of spinal CSF were quantitatively evaluated with a spine phantom that simulated spinal CSF pulsation. Two fundamental interdependent pulsation flow phenomena were observed: variable reductions in signal intensity of pulsatile CSF (signal loss) and spatial mismapping of this signal beyond the confines of the subarachnoid space (phase-shift images). Phase-shift images were observed as multiple regions of signal intensity conforming morphologically to the subarachnoid space but displaced symmetrically from it along the phase-encoding axis, either added to or subtracted from stationary signal intensity. Both CSF pulsation flow phenomena occurred secondary to harmonic modulation of proton precessional phase (temporal phase shift) by the unique pulsatile motion of spinal CSF when the repetition time was not an integral multiple of the pulsation period. Each flow phenomenon was analyzed with the spine phantom independently to control individual imaging and physiologic parameters including imaging plane, repetition time, echo time, slice thickness, number of echoes, number of excitations, CSF pulsation amplitude, and CSF pulsation period. In the axial plane, signal loss was present on both first- and second-echo images and was more pronounced with larger pulsation amplitudes and smaller slice thicknesses. A quantitative relationship between these two parameters allowed the prediction of CSF pulsation amplitude when the slice thickness was known and the CSF signal intensity was measured. In the sagittal plane, signal loss was present on first-echo images, was more pronounced with larger pulsation amplitudes, and underwent incomplete even-echo rephasing on second-echo images. Phase-shift images were influenced by the relationship between repetition time and CSF pulsation period. They were partly eliminated on sagittal but not on axial second-echo images because of incomplete even-echo rephasing. Both signal loss and phase-shift images were completely eliminated with CSF gating or pseudogating, indicating the rationale for gating during clinical spinal MR. The clinical significance of these findings is that awareness of the existence of spinal CSF pulsation flow phenomena avoids diagnostic confusion, whereas understanding their etiology provides a rational approach, such as CSF gating, to eliminate them.

Cerebrospinal Fluid↗

PubMed1987

CSF pulsations within nonneoplastic spinal cord cysts.

Because of its sensitivity to fluid motion, MR imaging was used to investigate fluid dynamics in syringomyelia. Three major findings characterized syringomyelia: pulsatile fluid in cysts, nonpulsatile fluid in cysts, and damaged cord tissue. The fluid in preoperative syrinx cavities pulsated in a fashion similar to subarachnoid CSF. Pulsation was more prominent in large cysts but was also seen in small cysts. Nonpulsatile cysts were generally of smaller diameter, were shorter in length, and often were single; they could, however, coexist with pulsatile cysts. Nonpulsatile cysts had etiologies similar to those of pulsatile cysts: Chiari malformation, trauma, and unknown. Damaged cord, characterized by abnormal high signal on T2-weighted sequences, was seen in 15 of 16 patients and could be either focal or diffuse but was always adjacent to syrinx cavities. Postsurgical MR scans had a lower incidence of pulsatile cysts. In five patients with both pre- and postoperative MR scans, shunting of the cyst reduced the size of the pulsating cyst (two patients) or reduced the size of the cyst and eliminated pulsation altogether (three patients). Axial, T2-weighted images are recommended in the investigation of spinal cord cysts to determine the presence or absence of pulsatile fluid. The presence of pulsation indicates a nonneoplastic cyst. The absence or reduction of CSF pulsation may prove to be a valuable indicator of the success of a shunting procedure.

Cerebrospinal Fluid↗

PubMed1986

Carotid bifurcation: results of spliced hybrid subtraction angiography compared with standard temporal and hybrid images.

Hybrid subtraction angiography can provide a higher percentage of two-view examinations of the carotid bifurcation. Unfortunately, hybrid images are lower in signal-to-noise ratio (S/N) than temporal subtraction angiographic images and are often described as "noisy." The present study was designed to determine if the lower S/N of hybrid subtraction angiography could be restricted to the contralateral carotid bifurcation by "splicing" a small hybrid region of interest into a larger temporal image. Twenty-two selected images were examined on four image quality scales by seven readers. Similarity of reader scoring was characterized by cluster analysis and was good. Ipsilateral carotid arteries were preferred as temporal images, and contralateral carotid arteries were preferred as hybrid images. The splice image was preferred over both. The splice image retained the superiority of temporal subtraction angiography in the region of the ipsilateral carotid artery and incorporated the superiority of hybrid subtraction angiography in the region of the contralateral carotid artery. The splice image incorporated the best features of both image modalities.

Aged↗

PubMed1986

Cerebrospinal fluid pulsation: benefits and pitfalls in MR imaging.

Physiologic cerebrospinal fluid (CSF) pulsation causes a harmonic modulation of proton precessional phase with two-dimensional Fourier transform (2DFT) imaging, which results in predictable regions of signal loss and the presence of phase-shift images ("ghost images"). CSF that is not pulsating exhibits a higher signal than does pulsatile CSF. This phenomenon can be diagnostically useful in disease entities associated with decreased CSF pulsation amplitude, such as arachnoid cyst, intraventricular cyst, spinal stenosis, and spinal block caused by extramedullary or epidural tumor. Unfortunately, this increased signal can also mimic disease such as epidural tumor in the spine or acoustic neuroma in the internal auditory canal. An abnormal pattern of CSF pulsation, as occurs in patients with arachnoiditis, can cause unusual areas of signal loss, which complicate image interpretation and can mimic pathologic conditions. Recognition of CSF pulsation effects will increase in importance as thin-section magnetic resonance imaging becomes more common, because thin sections enhance these effects with 2DFT.

Central Nervous System Diseases↗

PubMed1986

Quantitative analysis of intracranial circulation using rapid-sequence DSA.

By using a high-frame-rate technique, intravenous digital subtraction angiography (IVDSA) of the intracranial circulation was performed in patients with transient ischemic attacks and asymptomatic bruits. Twenty patients with normal carotid arteries or mild stenosis of no hemodynamic significance were selected as a control group to evaluate the effect of carotid stenosis on the difference between hemispheres in the peak arrival time (delta TMAX) of the contrast bolus. Data were obtained for the anterior (ACA), middle (MCA), and posterior (PCA) cerebral artery distributions. Raw data of the time-density curve in a region of interest were analyzed by polynomial curve-fitting techniques to obtain the peak arrival time (TMAX). The delta TMAXs for normal middle, anterior, and posterior distributions were 0.140 +/- 0.119 sec, 0.152 +/- 0.146 sec, and 0.189 +/- 0.187 sec, respectively. Eleven patients with tight carotid stenosis or occlusion whose delta TMAX fell outside the normal range as established from the 20 control patients were analyzed with regard to ischemic symptoms. The delta TMAXs of the MCA, ACA distributions in the asymptomatic patients with tight carotid stenosis or occlusion were 0.653 +/- 0.379 sec and 0.118 +/- 0.159 sec, respectively; p less than 0.001 in the MCA when compared with controls. The delta TMAXs of the MCA, ACA distribution in the symptomatic patients with tight carotid stenosis or occlusion were 1.31 +/- 0.13 sec and 0.525 +/- 0.079 sec, respectively; p less than 0.001 in the MCA and ACA distributions when compared with controls. Quantitative analysis of this type of physiologic data may enable the detection of patients with carotid stenosis who are well compensated by collateral flow from those who are poorly compensated and at risk for possible infarction on a hemodynamic basis. Serial followup DSA studies in patients with asymptomatic bruits may help to correlate the progression of extracranial carotid stenosis and the status of intracranial collateral reserves.

Adult↗

PubMed1986

Experimental brain abscess development in the chronically immunosuppressed host. Computerized tomographic and neuropathological correlations.

The neuropathological progression of brain abscess formation was studied experimentally in paired immunosuppressed and control dogs. The immunosuppressed animals received azathioprine and prednisone beginning 7 days prior to intracerebral inoculation with alpha streptococcus. Histological findings were correlated with computerized tomography (CT) brain scans. The evolution of brain abscess in the immunosuppressed animals could be divided into three stages based on histological evaluation: cerebritis stage (1 to 11 days), early-capsule stage (12 to 17 days), and late-capsule stage (18 days and later). There was a significant delay in the evolution of alpha streptococcus brain abscess compared to the authors' previous studies. Histologically, abscesses in immunosuppressed dogs were characterized by a decrease and delay in collagen formation, a reduction in polymorphonuclear leukocytes and macrophages, longer persistence of bacterial organisms, and an increase in gliosis. During the cerebritis stage, abscesses in control animals were consistently larger and more edematous than those in immunosuppressed animals and reached their maximum size by Day 8, whereas abscesses in immunocompromised animals reached their maximum size around Day 12. In the late-capsule stage, abscesses in immunosuppressed animals remained larger than those of control animals and continued to show signs of delayed development. This was evidenced by diffusion of contrast medium into the lucent center of ring-enhancing lesions on delayed CT scans. The results suggest that the decreased inflammatory response and edema formation in the immunosuppressed host resulted in less initial mass effect from brain abscess, but that the eventual size and area of the abscess may have become larger due to the less effective host response.

Animals↗

PubMed1986

Contrast media tonicity. Part II. Isotonic ioxaglate vs. standard renografin for IV-DSA evaluation of the carotid bifurcation, a double-blind prospective clinical trial.

Laboratory research has suggested that isotonic contrast media may be optimal for intravenous digital subtraction angiography (IV-DSA) by generating taller, narrower time-concentration curves. Clinical investigation of low osmolality contrast media has suggested that less patient discomfort is encountered with low-osmolality contrast media than with standard, high-osmolality agents. In order to directly compare isotonic contrast media with a standard hypertonic contrast media, isotonic ioxaglate (Hexabrix-20) was compared with Renografin-76 in a double-blind prospective clinical trial for IV-DSA examination of the carotid artery bifurcation. Isotonic ioxaglate produced superior contrast medium time-opacification curves and produced superior images across four scales of image quality: anatomic "openness" of the carotid bifurcation, contrast level within the carotid vessels, bone misregistration artifact over the bifurcation, and air (soft tissue) misregistration. The bilateral overall score for isotonic ioxaglate was 1.68 vs. 1.37 for Renografin-76, a 23% superiority. The bulk of the superiority occurred in the contralateral carotid artery. Over the four scales, isotonic ioxaglate was 37% better in image quality of the contralateral carotid artery bifurcation. Since the contralateral carotid artery is very often difficult to visualize during IV-DSA, isotonic ioxaglate represents a significant improvement for this imaging modality.

Angiography↗

PubMed1985

Brain abscess.

Explore the source record for details and available documents.

Adrenal Cortex Hormones↗

PubMed1985

Tumors of the central nervous system studied by computed tomography and ultrasound.

Intraoperative ultrasound (US) was compared to computed tomography (CT) in 41 intracranial and 6 spinal cord tumors. The studies correlated closely except for primary gliomas. Eight of the 22 primary intracranial gliomas (37%), including 1 low-grade and 7 anaplastic tumors, were larger and more extensive on US than on CT. Margins of non-enhanced primary astrocytomas were shown by US but not CT. Four anaplastic tumors (19%) exhibited echogenicity extending beyond the enhanced area. In 4 patients an enhanced lesion contained a lucent center which proved to be echogenic. Low-grade astrocytomas were relatively homogeneous on US, while anaplastic astrocytomas were more inhomogeneous. Cysts could be found in both types of astrocytomas and were often small and multiple. The echo pattern was not helpful in differentiating metastases from primary tumors, although all of them had sharp margins. Sonography of the central nervous system can provide valuable information about tumor morphology and margins.

Astrocytoma↗

PubMed1985

Assessment of laryngeal function by digital subtraction laryngography.

The evaluation of vocal cord function can be problematic in the presence of oropharyngeal tumors, hypopharyngeal tumors, and supraglottic lesions and in noncompliant adult and pediatric patients. The use of computer image subtraction techniques coupled with digital fluoroscopy has inherent high-quality resolution that can provide an excellent image of vocal cord symmetry and movement. The use of air as the contrast medium provides the ability to measure the extent of vocal cord excursion as well as the extent of piriform sinus lesions. In addition, it is a noninvasive procedure that requires a minimal imaging exposure time, with the result that the patient undergoes minimal radiation exposure.

Air↗

PubMed1984

Intraoperative and outpatient echoencephalography through a burr hole.

Ultrasound images of the brain were obtained intraoperatively and on an outpatient basis through a burr hole. The patient's tumor was well visualized, prior to biopsy, after biopsy, and during radiation therapy treatment. The ultrasound images correlated closely to the CT scan findings.

Ambulatory Care↗

PubMed1984

Computed tomographic findings in septo-optic dysplasia: discordance between clinical and radiological findings.

The clinical and radiological findings in four children with septo-optic dysplasia are reported. All four had growth retardation associated with growth hormone deficiency, as well as varying degrees of ophthalmologic dysfunction. The CT scan findings spanned a spectrum from normal to the expected abnormalities involving the ventricular system and orbits. Only two of the four had an absent septum pellucidum. A third patient had normal CT scans except for optic nerve hypoplasia, while the fourth had entirely normal CT scans of both the brain and orbits. Because the anatomic defects of septo-optic dysplasia may be subtle, an apparently normal CT scan does not invalidate the clinical diagnosis of septo-optic dysplasia.

Brain↗

PubMed1984

Dynamic computed tomographic scans in experimental brain abscess.

Dynamic computed tomographic scans were performed in an experimental brain abscess model to establish criteria that could be utilized in abscess staging. The vascular phase of the time-density curves did not differentiate cerebritis and capsule stages. The amount of residual enhancement after the first pass of an intra-arterial contrast bolus differed between major abscess stages, the greater residual enhancement being noted in the capsule stage.

Animals↗