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Biomedical subjects

D R Enzmann

Publications and source records attributed to D R Enzmann.

At least 55 records · Page 3Linked to original sources
PubMed1990

Benign versus pathologic compression fractures of vertebral bodies: assessment with conventional spin-echo, chemical-shift, and STIR MR imaging.

Differentiation of benign from pathologic compression fractures of vertebral bodies was evaluated with magnetic resonance imaging in a prospective study of 53 patients. Twenty-six patients had 34 benign posttraumatic compression fractures. Twenty-seven patients had metastatic disease to the vertebral column and seven pathologic fractures. T1- and T2-weighted spin-echo (SE) sequences (1.5 T) were performed in all patients. A presaturation technique was used to obtain "fat" and "water" images to better assess the degree of normal fatty marrow replacement in fractured vertebrae. Short inversion-time inversion-recovery (STIR) images were also obtained. Discrimination between benign and pathologic compression fractures was generally possible with the SE sequences. Chronic benign fractures demonstrated isointense marrow signal intensity (SI), compared with that of normal vertebrae with all sequences. Pathologic fractures showed low SI on T1-weighted images and high SI on T2-weighted images. Fat images revealed complete replacement of normal fatty marrow, shown as absent SI in the involved vertebral body. Water and STIR images showed diffuse high SI in pathologic fractures, with STIR images having the highest contrast between abnormal and normal marrow. Acute benign compression fractures also demonstrated high SI on T2-weighted, water, and STIR images, but the SI was less pronounced and the pattern was generally more inhomogeneous than that of pathologic compressions. In general, fat images showed only partial replacement of normal fatty marrow by low SI, in contrast to the complete absence of marrow SI typical of pathologic fractures.

Adolescent↗
PubMed1990

Defining the normal temporomandibular joint: closed-, partially open-, and open-mouth MR imaging of asymptomatic subjects.

Fifty temporomandibular joints (TMJs) in 30 asymptomatic volunteers were imaged with a 1.5-T magnetic resonance (MR) imaging system to determine (a) the normal range of meniscus position, (b) the best definition of a normal TMJ and criteria to distinguish it from a TMJ with significant internal derangements, (c) the significance of certain findings such as joint effusion and disk distortion, and (d) the optimum mouth position(s) to be used for imaging. A method was devised to quantify meniscus displacement in terms of the number of degrees from a 12 o'clock or vertical position (relative to the condyle). The distribution of meniscus positions defined two groups in this asymptomatic study group. A strong correlation between abnormal joints and a history of orthodontics led to the exclusion of subjects with a history of orthodontics, and those with mouth trauma were also excluded, leaving a better "normal control" group. The junction of the posterior band of the meniscus and the bilaminar zone should fall within 10 degrees of vertical to be within the 95th percentile of normal.

Cartilage, Articular↗
PubMed1990

TMJ meniscus and bilaminar zone: MR imaging of the substructure--diagnostic landmarks and pitfalls of interpretation.

Identification of the junction of the posterior band with the bilaminar zone is important to detect anterior displacements of the temporomandibular joint (TMJ) meniscus on magnetic resonance (MR) images. However, significant differences in tissue characteristics within the meniscus itself may cause a confusing appearance that is not easily reconciled with available anatomic references. Six cadaveric TMJ specimens were imaged sagittally at 1.5 T with various combinations of repetition time and echo time and with use of both standard surface coils and a specially developed solenoidal specimen coil. Corresponding histologic sections were correlated with the in vitro MR images to identify the anatomic structure and tissue characteristics. Comparison of these in vitro images with in vivo images of 100 joints identified a vertical, linear, low-signal-intensity band as an important landmark of the junction of the posterior band and bilaminar zone. Recognition of the signal-intensity characteristics of the center and the surfaces of the posterior band as well as the appearance of the insertion of the bilaminar zone also increased confidence of visualization and helped avoid possible false-positive diagnoses.

Diagnostic Errors↗
PubMed1990

Occult vascular malformations of the optic chiasm: magnetic resonance imaging diagnosis and surgical laser resection.

Angiographically occult vascular malformations of the optic nerve and chiasm are extremely rare. Before the advent of magnetic resonance imaging (MRI), it was difficult to diagnose these lesions preoperatively. We report MRI scan findings of optic chiasm cavernous angiomas in two patients with chiasmal syndrome. MRI was useful in localizing the vascular malformation and delineating its characteristics, especially chronic hemorrhage. One patient underwent biopsy of the lesion. The other patient underwent complete microsurgical resection of the malformation with the carbon dioxide laser with preservation of vision. Occult vascular malformations of the optic nerve and chiasm may be a more common cause of visual deterioration than previously recognized. The MRI scan is the imaging modality of choice for diagnosing and following these lesions. In certain patients, these vascular malformations may be amenable to complete surgical removal with stabilization or improvement of visual function.

Adult↗
PubMed1988

Cervical spine: MR imaging with a partial flip angle, gradient-refocused pulse sequence. Part I. General considerations and disk disease.

A magnetic resonance imaging pulse sequence with a short repetition time (TR), short echo time (TE), partial flip angle, and gradient refocused echo was evaluated for the detection of cervical disk disease in a prospective study of 90 patients. These parameters were manipulated to adjust signal-to-noise ratio (S/N) and contrast: flip angle (3 degrees-18 degrees), TR (22-60 msec), and TE (12.5-25 msec). Flip angle had the greatest effect on S/N and contrast; its effect differed between axial and sagittal imaging. Cerebrospinal fluid S/N reached a peak at a smaller flip angle in sagittal imaging than in axial imaging. The useful range of flip angles depended on TR. Increasing TR had minimal direct effect on S/N or contrast, but because a longer TR allowed the use of larger flip angles for both axial and sagittal imaging, higher S/N could be achieved with similar contrast. This effect of increasing TR had to be balanced against increased imaging time and increased probability of motion artifact. Increasing TE decreased S/N, increased contrast, and increased magnetic susceptibility artifacts. For the diagnosis of cervical disk disease, the best sequence appears to be one with a very short TR, short TE, and small flip angles within a narrow range.

Cervical Vertebrae↗
PubMed1988

Cervical spine: MR imaging with a partial flip angle, gradient-refocused pulse sequence. Part II. Spinal cord disease.

A magnetic resonance imaging pulse sequence (GRASS) with a short repetition time (TR), short echo time (TE), partial flip angle, and gradient refocused echo was prospectively evaluated for the detection of cervical cord disease that caused minimal or no cord enlargement in eight patients. Sagittal T2-weighted, cerebrospinal fluid (CSF)-gated images and sagittal and axial GRASS images were obtained in all patients. The following GRASS parameters were manipulated to determine their effect on signal-to-noise ratio (S/N) and contrast: flip angle (4 degrees-18 degrees), TR (22-50 msec), and TE (12.5-25 msec). Flip angle had the greatest effect on S/N and contrast. There were no differences between axial and sagittal imaging for the spinal cord or lesion. However, because the signal intensity of CSF did differ on sagittal and axial images and because this influenced the conspicuity of lesions, there was a difference in the useful flip angle range for axial and sagittal imaging. No one set of imaging parameters was clearly superior, and in all patients, the gated image was superior to the sagittal GRASS image in lesion detection. GRASS images should be used in the axial plane primarily to confirm spinal cord disease detected on sagittal CSF-gated images. For this, a balanced approach is suggested (TR = 40 msec, TE = 20 msec, with flip angles of 4 degrees-6 degrees for sagittal and 6 degrees-8 degrees for axial imaging).

Humans↗
PubMed1988

Lumbar spine: motion compensation for cerebrospinal fluid on MR imaging.

To determine whether the motion of cerebrospinal fluid (CSF) in the lumbar spine degrades T2-weighted magnetic resonance (MR) images, a spine phantom, three healthy volunteers, and a prospective series of 20 patients suspected of having lumbar spine disease underwent MR imaging with and without motion-compensation techniques. In the phantom, pulsation amplitudes as low as 3 mm (within the physiologic range of human lumbar CSF motion) reduced image quality on conventional images but not on motion-compensated images. Similar findings were observed in two volunteers and 11 patients. The magnitude of the artifacts was variable; they could impair visualization of the conus, decrease contrast or reduce the sharpness of the CSF-thecal sac interface, and cause focal regions of reduced CSF signal intensity adjacent to bulging disks. Image quality was most improved when peripheral gating was combined with even-echo rephasing. In the patient group, the use of motion-compensation techniques increased the CSF signal-to-noise ratio by an average of 29% (P less than .01); this resulted in improved contrast between the conus and extradural structures. The data suggest that CSF motion compensation is clinically useful during T2-weighted MR imaging of the lumbar spine.

Adult↗
PubMed1988

Intracranial vascular malformations: imaging of charged-particle radiosurgery. Part I. Results of therapy.

Twenty-four patients with intracranial vascular malformations were examined before and after helium ion radiosurgical treatment with angiography, computed tomography (CT), and magnetic resonance (MR) imaging. Twenty patients had high-flow arteriovenous malformations (AVMs). After treatment 18 of 20 AVMs (90%) showed a significant reduction in size on angiograms or MR images. Eleven of 20 (55%) had complete resolution on angiograms or MR images, 35% had partial resolution, and 10% showed no size change. Before treatment, the size range of the AVMs was 0.86-383 cm3 (median, 21.7 cm3). Smaller AVMs (less than 8 cm3) were more likely to resolve completely than medium-sized AVMs (8-64 cm3) or larger AVMs (greater than 64 cm3). Four additional patients had slow-flow vascular malformations: One had a venous angioma; one, a probable cavernous hemangioma; and two, malformations that were not seen on angiograms. CT proved inaccurate in demonstrating the boundaries of the AVM after treatment because it showed persistent contrast enhancement even when the AVM was completely obliterated on angiograms. MR imaging and angiography were complementary in the evaluation of therapeutic results and should be the primary modalities in the examination of patients with AVMs.

Adult↗
PubMed1988

Intracranial vascular malformations: imaging of charged-particle radiosurgery. Part II. Complications.

Seven of 24 patients with intracranial vascular malformations who were treated with helium-ion Bragg-peak radiosurgery had complications of therapy. New symptoms and corresponding radiologic abnormalities developed 4-28 months after therapy. Five patients had similar patterns of white matter changes and mass effect on computed tomographic scans and magnetic resonance images. The abnormalities were centered in the radiation field. Gray matter changes and abnormal enhancement in the thalamus and hypothalamus outside the radiation field developed in one patient. This patient also had vasculopathic changes on angiograms. Rapidly progressive large vessel vasculopathy developed in another patient and caused occlusion of major vessels. Thus, different mechanisms may be involved in the complications of heavy-ion radiosurgery.

Adult↗
PubMed1988

End-stage periventricular leukomalacia: MR evaluation.

A prospective study was performed to assess the capabilities of magnetic resonance (MR) imaging in evaluation of end-stage periventricular leukomalacia (PVL) in six children, aged 31-54 months, in whom PVL had been documented by neurologic ultrasonography during the neonatal period. Eight children of similar age (four premature infants and four full-term infants) with normal neurologic development served as controls. A characteristic triad of PVL abnormalities was seen on MR images: (a) abnormally increased periventricular white-matter signal intensity on the first and second echo images of a T2-weighted sequence (repetition time = 2,000-2,400 msec, echo times = 20 or 30 and 80 msec), most commonly observed in the trigone regions of the lateral ventricles bilaterally; (b) marked loss of periventricular white matter in these regions of abnormal signal intensity, predominantly in the periatrial regions; and (c) compensatory focal ventricular enlargement adjacent to regions of abnormal signal intensity. In patients with the classic periatrial distribution of PVL lesions, general correlation between the degree of neurologic impairment and the severity of MR abnormalities was demonstrated. MR imaging was useful in detecting subtle forms of PVL in cases in which neurologic damage was subclinical.

Encephalomalacia↗
PubMed1988

Neurologic complications of cardiac transplantation.

The neurologic evaluation of an individual cardiac transplant recipient often does not lead to a succinct bedside diagnosis. There are few consistent clinical observations. The onset of seizures in the early postoperative period is associated with embolic cerebral infarction. Seizures occur most commonly, however, as a neurotoxic manifestation of cyclosporine. The onset of an acute delirium or psychosis in the first week after cardiac transplantation usually has multiple causative factors and is reversible. A postoperative brachial plexopathy or mononeuropathy can be identified with a neurologic examination, confirmed by appropriate electrophysiologic testing and is usually reversible. The onset of periorbital inflammation, ophthalmoplegia, and nasal turbinate or sinus invasion and necrosis is consistent with phycomycosis. Most patients, however, present with nonspecific findings of impaired mentation with or without focal neurologic signs. These patients require a fairly systematic search for potentially treatable neurologic complications (see Table 3). In a medically stable patient an aggressive diagnostic approach, at times including stereotaxic brain aspirate or biopsy, is indicated. In the severely ill patient with multiple organ failure, empirical therapy for the most probable treatable disorder is justified.

Brain Abscess↗
PubMed1987

Correlation of neuropathologic findings, computerized tomographic and high-resolution ultrasound scans of canine avian sarcoma virus-induced brain tumors.

The location, size, geometry and neuropathological findings of anaplastic astrocytomas (AA), gliosarcomas and sarcomas induced by the avian sarcoma virus (ASV) in dogs were compared with images generated using computerized tomography (CT) and real time high-resolution ultrasound (HRUS). Seven AA showed a wide range of findings on CT. Pre-contrast CT scans showed that the tumors could be hyper, hypo, or isodense. Three of seven AA had no contrast enhancement; two of these tumors were also isodense which resulted in a false-negative CT exam. Partial enhancement was seen in one tumor. This resulted in a sensitivity of detection of 72%. Real time HRUS was able to define tumor location, size and geometry of the AA missed or incompletely imaged by CT. All tumors were hyperechoic. Inhomogeneity of the echo pattern was due to hemorrhage, cyst formation, and necrosis within the tumors. Such secondary tumor characteristics were more accurately defined by HRUS compared to CT. Vasogenic edema in the brain surrounding tumors was of low density on CT and hypoechoic or indistinguishable from normal brain on US. Similar findings were seen in six gliosarcomas, two of which were not visualized by either pre- or post-contrast enhanced CT scans (sensitivity of 66%). Sarcomas differed in that they were either hyper or isodense; none were hypodense. The area of increased density matched the tumor geometry and correlated with dense cellularity and reticulin deposition. All 13 sarcomas showed contrast enhancement (100% sensitivity), but in two tumors, contrast enhanced CT underestimated the size of the tumor. Because of the large size and multiplicity of the sarcomas, HRUS imaging was not able to resolve the entire tumor volume because of limited imaging access. Intravenously injected horseradish peroxidase (HRP) crossed the tumor blood-brain barrier (BBB) only in those tumors in which contrast enhancement was seen. These studies suggest that intraoperative HRUS imaging may be useful in detecting and delineating human AA incompletely visualized by CT.

Animals↗
PubMed1987

Size determination of supratentorial arteriovenous malformations by MR, CT and angio.

Twenty patients with high-flow supratentorial arteriovenous malformations (AVMs) were studied by magnetic resonance imaging (MR), computed tomography (CT), and selective cerebral angiography. The size of the malformation measured on MR was found, in general, to be smaller than the size determined from angiographic films. This discrepancy increased as the size of the AVM increased. AVM size on CT and angiography was found to be essentially equivalent. The reason for these differences between MR and CT or angiography was the ability to separate out the draining veins by MR, whereas this was difficult on projection films and contrast enhanced CT. Calcification was more easily detected by CT than by MR. MR better detected hemorrhage, which could be mistaken for old infarction on CT. Foci of cystic change within the nidus of the AVM were equally evident on MR and CT. Due to its sensitivity in discriminating between AVM nidus and adjacent draining veins and MR's ability to show the AVM in three planes, MR appeared to be more accurate in defining the AVM nidus than either CT or cerebral angiography. Such accurate delineation is crucial in patients prior to stereotactic radiosurgery.

Calcinosis↗
PubMed1987

Correlation of echoencephalographic findings and neurodevelopmental outcome: intracranial hemorrhage and ventriculomegaly in infants of birth weight 1,000 grams or less.

Echoencephalograms were obtained for 118 of 121 successive infants who were admitted to the Stanford intensive care nursery, weighed 1,000 g or less at birth, and survived long enough for at least one study to be performed. Eighty-eight of these infants survived and were followed up for 1 to 3 years; psychometric testing (Bayley Scales of Infant Development, Stanford-Binet Intelligence Scale, or both) was performed on 81% of these infants. Subependymal-intraventricular hemorrhages or intraparenchymal hemorrhages were associated with impaired development, but ventriculomegaly was not. The absence of echoencephalographic abnormalities did not exclude the possibility of impaired development in many infants. Periventricular leukomalacia was not observed. These data support independent scoring of subependymal-intraventricular hemorrhages, intraparenchymal hemorrhages, and ventriculomegaly, rather than use of combined scales for prognostic purposes.

Brain Damage, Chronic↗
PubMed1987

Use of cerebrospinal fluid gating to improve T2-weighted images. Part I. The spinal cord.

Ungated and gated magnetic resonance images of the spinal cord acquired with the use of long repetition times (TRs) and long echo-delay times (TEs) were compared in 21 studies performed on a 1.5-T system. Both normal and abnormal spinal cord conditions were compared. All images were acquired in an identical fashion except that ungated studies had TRs of 2,000 or 2,500 msec, whereas in gated studies, TR was determined by the patient's heart rate. The effective TR of images gated to the cerebrospinal fluid (CSF) fell primarily in the range of 1,500-1,800 msec. Gating was accomplished using a peripheral pulse. Three image parameters were assessed: signal-to-noise ratio, object contrast, and resolving power. For each parameter, in both normal and abnormal spinal cords, the CSF-gated studies proved superior by eliminating spatially mismapped signal intensity from pulsatile CSF.

Cerebrospinal Fluid↗
PubMed1987

Use of cerebrospinal fluid gating to improve T2-weighted images. Part II. Temporal lobes, basal ganglia, and brain stem.

Ungated and gated magnetic resonance images of the temporal lobes, basal ganglia, and brain stem acquired with the use of long repetition times (TRs) and long echo-delay times (TEs), were compared quantitatively. Twenty-five pairs of images obtained on a 1.5-T system were evaluated. Ungated images (TR = 2,000 msec, TE = 80 msec) were acquired in the same manner as gated images except for TR, which, for gated studies, was determined by a patient's heart rate and generally fell into the 1,500-1,800-msec range. Three image parameters were assessed: signal-to-noise ratio (S/N), object contrast, and resolving power. In both normal and abnormal brain tissue, gated images were superior to ungated images in object contrast and resolving power and equivalent in S/N. More so than in comparable studies of the spinal cord, ungated studies were susceptible to both false-positive and false-negative interpretations. As in spinal cord studies, the major benefit of gating was the elimination of phase shift images arising from basal cisterns and the third ventricle.

Basal Ganglia↗
PubMed1987

Neonatal herpes simplex encephalitis: correlation of clinical and CT findings.

Review of 31 computed tomographic (CT) scans in 15 neonates with herpes simplex encephalitis (HSE) type 2 revealed the most characteristic early findings to be patchy and widespread areas of low attenuation, primarily in white matter, with minimal contrast material enhancement in a meningeal pattern. The low-attenuation lesions increased rapidly in size and prominence during the course of the disease. This was usually accompanied by increased attenuation of cortical gray matter that persisted for weeks to months. Atrophic changes appeared rapidly, being evident in the 3d week. Late findings consisted of very extensive, diffuse, low attenuation of white matter with cortical atrophy. Calcification assumed a variety of distributions, from punctate to an extensive gyral pattern. The cerebellum was involved in nine patients. Early CT findings were not good predictors of outcome, but later serial CT scans showing progression or stability of findings were more accurate in prognosis. CT serves primarily to confirm the diagnosis of neonatal HSE.

Encephalitis↗