Thirty-eighth annual meeting of the American Society of Neuroradiology.
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Georgia↗
Biomedical subjects
R D Zimmerman
Publications and source records attributed to R D Zimmerman.
Is there a role for diffusion-weighted imaging in patients with brain tumors or is the "bloom off the rose"?
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Brain↗
Disseminated intravascular coagulation and the neuroradiologist.
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Craniocerebral Trauma↗
MR imaging of acute intracranial hemorrhage: findings on sequential spin-echo and gradient-echo images in a dog model.
Seven intraparenchymal hematomas (four venous and three arterial) were placed in the brains of six dogs in order to study the MR appearance of acute hemorrhage and to evaluate the effects of several variables on the signal intensity of the hematoma. MR imaging at 0.6 and 1.5 T was performed by using standard short and long TR spin-echo and low-flip-angle gradient-echo sequences. Sequential examinations were performed during the first week following hematoma creation. MR findings were compared with CT and postmortem examinations. Three patterns of signal intensity were observed, which varied according to the size (small vs large) and location (parenchymal vs intraventricular) of the hematomas. The small parenchymal hematomas did not undergo evolutionary changes. On short TR scans they were isointense at both field strengths, and therefore not detectable; on long TR scans these hematomas were of variable intensity at 1.5 T and were hyperintense at 0.6 T. On gradient-echo scans, they were hypointense at all times at both field strengths. The large parenchymal hematomas underwent evolutionary changes typical of those seen in clinical imaging. On short TR scans they were initially isointense and became hyperintense 1-3 days later. Long TR scans demonstrated initial hyperintensity, followed by the development of hypointensity within 12 hr in the venous hematomas and within 60 hr in the arterial hematoma. The intensity changes on long TR scans were seen at both 0.6 and 1.5 T, but occurred sooner and to a greater degree at 1.5 T. Gradient-echo imaging of these large lesions demonstrated hypointensity at all times at both field strengths. The intraventricular hemorrhages demonstrated more rapid development of hyperintensity on short TR scans and slower and less pronounced development of hypointensity on long TR scans compared with the parenchymal clots in the same animal. Gradient-echo imaging of the intraventricular hemorrhages demonstrated hypointensity at all times at both field strengths. A multifactorial hypothesis is proposed to explain the differences in intensity between venous, arterial, and intraventricular blood. Gradient-echo sequences should prove to be highly useful in detecting and delineating hemorrhages and are recommended for the MR protocol of patients with acute neurologic ictus and suspected hemorrhage.
Acute Disease↗
Detection of acute intracerebral hemorrhage on MR imaging: ineffectiveness of prolonged interecho interval pulse sequences.
MR imaging at 0.6 T was performed in 22 patients with acute (less than 7 days) intracranial hemorrhage to determine the efficacy of prolongation of the interecho interval, which has been demonstrated to enhance T2 shortening in vitro, as a method to improve the detection of hemorrhage in clinical imaging. The protocol included 750/33 (TR/TE), 2150/60,120 (short interecho interval of 60 msec), and 2150/120 (long interecho interval of 120 msec) sequences. Visual comparisons of the 2150/120 images obtained with the short and long interecho intervals demonstrated no difference in the degree of hypointensity in 21 of 22 cases. Quantitative comparisons demonstrated no statistically significant difference in the degree of maximal hypointensity, in the ease of detectability of hypointensity, or in the overall image contrast in 16 of 22 cases. We conclude that prolongation of the interecho interval is not a clinically useful technique to improve the detection of acute hemorrhage.
Acute Disease↗
Computed tomography and magnetic resonance imaging comparisons in boxers.
The efficacy of computed tomography (CT) and magnetic resonance imaging (MRI) in identifying traumatic injuries of the brain was compared in a referred population of 21 amateur and professional boxers. Three boxers displayed CT scans with equivocal findings that were verified as artifacts by MRI. Eleven boxers had both CT and MRI scans with normal findings, and 7 boxers had both CT and MRI scans with abnormal findings. There were no instances where abnormalities demonstrated on CT scanning were not detected by MRI. However, some abnormalities detected on MRI were not detected on CT scans. These included a subdural hematoma, white-matter changes, and a focal contusion. Magnetic resonance imaging appears to be the neuroradiodiagnostic test of choice compared with CT.
Adult↗
Differentiation between meningeal fibrosis and chronic subdural hematoma after ventricular shunting: value of enhanced CT and MR scans.
Unenhanced CT in four patients with long-standing ventricular shunts demonstrated bilateral low-density extraaxial collections that were indistinguishable from chronic subdural hematomas. After administration of contrast material, however, there was marked enhancement of the collections as well as prominent paratentorial and parafalcial enhancement. MR imaging, performed in three patients, demonstrated the extent and paradural location of the collections better than CT did, but, as with unenhanced CT, the collections could not be distinguished from chronic subdural hematomas. On follow-up CT and MR, there was no change in the size, enhancement, or intensity of the collections. Histologic examination of biopsies from two patients demonstrated fibrosis of the meninges characterized by granulation tissue and collagen deposition. Meningeal fibrosis is a rare postshunt phenomenon that may mimic chronic subdural hematoma on unenhanced CT and MR. Recognition of this entity is important, particularly if therapeutic intervention is being considered. Therefore, an enhanced CT or enhanced MR scan should be obtained in chronically shunted patients to differentiate between a drainable chronic subdural hematoma and meningeal fibrosis.
Adult↗
Large Virchow-Robin spaces: MR-clinical correlation.
High-field MR scans frequently show Virchow-Robin spaces, which conform to the path of the penetrating arteries as they enter either the basal ganglia or the cortical gray matter over the high convexities. A retrospective review of 816 MR scans was undertaken to determine the clinical significance and associations (if any) of this finding. The Virchow-Robin spaces were graded, as were the nonspecific white-matter lesions. The presence of atrophy, infarction, hydrocephalus, and miscellaneous disease was noted. Large Virchow-Robin spaces were identified in 314 cases. A study sample was created consisting of a positive group containing all the larger grade 2 and 3 Virchow-Robin spaces (67 patients) and a negative or control group of 109 randomly selected patients from the original 502 who did not have large Virchow-Robin spaces. The charts of this study sample were reviewed and the following patient variables were noted: age, gender, incidental white-matter lesions, infarction, dementia, hypertension, and atrophy. For each variable, the proportion of patients who were positive for that variable was calculated for each of the two groups and compared across groups by using a Fisher exact test. Multiple logistic regression analysis was used to determine whether any of these variables were jointly associated with being "positive" or "negative" for large Virchow-Robin spaces. Some variables were strongly associated with being positive for large Virchow-Robin spaces: age, hypertension, dementia, and incidental white-matter lesions. Logistic regression analysis revealed that when all of these variables are considered jointly, only age remains significant.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Dural sinus thrombosis: verification with spin-echo techniques.
Although MR imaging is being used increasingly to detect dural sinus thrombosis, accurate evaluation of images has often been hindered by the presence of artifacts, especially flow-related enhancement, that may simulate intraluminal clot. We tried an approach with spin-echo techniques to eliminate flow-induced artifacts and, thus, facilitate the diagnosis of dural sinus thrombosis. In this investigation, a nonselective single-section spin-echo verification method was used as a prototype of this approach. Both patients and an experimental flow phantom were used to test the validity of this concept. Clinically, thrombosis was seen to persist as isointense or highly intense signal in the vascular lumina with the specialized sequence, while flow-related artifacts were replaced by hypointense signal, but not by signal void. These same changes were examined both quantitatively and qualitatively in the flow phantom by using varying velocities of flow. Although our clinical investigation concerns suspected dural sinus thrombosis, the principles of these specialized spin-echo techniques can be applied successfully throughout the head to eliminate certain flow-related artifacts.
Adolescent↗
Head trauma: comparison of MR and CT--experience in 100 patients.
The results of CT and MR imaging were reviewed retrospectively and compared in 100 patients who experienced clinically significant head trauma. The findings were analyzed on the basis of several parameters in an attempt to establish objective clinical guidelines for the use of each diagnostic technique. CT remains the screening method of choice in evaluating acute severe head trauma; however, MR revealed additional clinically relevant findings in all four cases in which the patient's clinical symptoms were disproportionate to the CT findings. MR was equal or superior to CT in the evaluation of all patients with acute minor head trauma and in 94 of 95 patients examined in the subacute, chronic, or remote phase of injury, irrespective of the severity or pathologic nature of their injuries. All subacute contusions (21 lesions) and white-matter shearing lesions (18 cases) were demonstrated to particular advantage on MR compared with CT, as were all subdural hematomas (of 52 small subdural collections, 58% were detected only by MR). Although surgical management was not altered by the additional information provided by MR, the implications regarding the medical management and disposition of the patients with head trauma were significant.
Brain Concussion↗
Magnetic resonance imaging of meningiomas.
Twenty-eight patients with 32 meningiomas were studied on a 0.5-T superconductive magnetic resonance (MR) imager. This common, benign treatable tumor was more clearly seen on computed tomography (CT) than MRI in 53% of cases. This is a result of poor contrast between the tumor and the adjacent brain on all spin-echo and inversion-recovery pulse sequences. Those sequences that provide the greatest anatomic detail were best for identifying this low-contrast lesion. Inversion-recovery scans in particular demonstrated the tumor as a discrete hypointense mass (relative to nearby white matter) with excellent visualization of the dural base and white matter buckling indicative of extracerebral mass effect. Other characteristic features include: a hypointense rim because of the venous capsule (66%); mottling due to hypervascularity; a well defined edema collar that demarcates the tumor from adjacent brain; and hyperostosis with thickening of the calvaria and obliteration of its normal landmarks. MRI did not demonstrate tumor calcification but did demonstrate vascular encasement, displacement, and occlusion better than CT and as well as digital venous angiography.
Adult↗
Computed tomographic changes of hypertensive encephalopathy.
Computed tomographic (CT) scans were evaluated in 11 patients with acute hypertensive encephalopathy. Hypertensive encephalopathy is characterized by an acute, severe rise in blood pressure associated with headache, nausea, vomiting, altered mental status, and focal neurologic deficits, and rapid improvement after control of blood pressure. The systolic blood pressure range is 200-280 mm Hg; diastolic is 130-170 mm Hg. The most common CT finding was white-matter edema, diffuse or focal, affecting the supratentorial compartment in all cases and the infratentorial compartment in eight. These changes resolved after the blood pressure was lowered in all six patients studied by follow-up CT. Permanent areas of infarction were demonstrated in three patients. These abnormalities are correlated with the neuropathologic findings in hypertensive encephalopathy.
Adolescent↗
MR imaging of cerebral vascular malformations.
Fifteen vascular malformations, including six supratentorial arteriovenous malformations (AVMs), three venous malformations, and six brainstem vascular malformations, were examined on 0.5 T magnetic resonance (MR) and GE 9800 and 8800 computed tomographic (CT) scanners. All the malformations were shown by MR, and the arterial and venous drainage of AVMs was precisely delineated. Hematoma was always differentiated from calcification by MR signal characteristics. Increased signal in the brain parenchyma was often seen adjacent to AVMs. The signal of blood within venous malformations altered with spin-echo techniques using various repetition times and was distinguished from rapidly flowing blood in AVMs that lacked signal in all imaging sequences. Brainstem malformations were seldom demonstrated by angiography. Hemorrhage was common and was invariably associated with multiple areas of absent signal that may have represented abnormal vessels. These appearances are distinct from those of intrinsic tumors and are probably pathognomonic of brainstem vascular malformations.
Brain↗
Aortic arch digital arteriography: an alternative technique to digital venous angiography and routine arteriography in the evaluation of cerebrovascular insufficiency.
Digital arch arteriography is a technique in which the cervicocerebral vasculature is studied by injecting small amounts of contrast material (20 ml or less of diatrizoate meglumine 60%) into the aortic arch. It was used as the initial phase of arteriography in 100 patients with cerebrovascular disease. Five to ten series were obtained in various projections to evaluate the cerebrovascular system. Because suboptimal studies may be repeated, only 3% of carotid bifurcations were suboptimally visualized by digital arch arteriography as compared with 17% by film arch angiography. Intracranial vascular pathology was identified less reliably than with selective angiography. Digital arch arteriography yielded excellent studies in cases when digital venous angiography was suboptimal (20%). Digital arch arteriography may be preferable to digital venous angiography as a screening test in patients with significant cardiac or renal dysfunction because of the lower contrast load.
Aorta, Thoracic↗
Axial CT recognition of anteroposterior displacement of fourth ventricle.
The recognition of anterior or posterior displacement of the fourth ventricle on axial computed tomography (CT) has proven to be difficult because the apparent position of this structure is variable and dependent on scanning angle. In most cases direct visualization of a lesion and its relationship to normal anatomic structures allows for the correct assessment. However, in some instances it would be advantageous for lesion localization to be able to identify relatively subtle displacements of the fourth ventricle. This is possible on CT by determining the position of this structure relative to Twining's line (the line between the tuberculum sellae and torcula). The position of the fourth ventricle, tuberculum sellae, and torcula relative to an arbitrary fixed point can be established in virtually all cases, and thus the position of the fourth ventricle relative to Twining's line can be determined. In a control group of 100 patients with normal CT examinations, the ratio of the distance from the tuberculum sellae to the center of the fourth ventricle and the distance from the tuberculum sellae to torcula (Twining's line) was between 0.47 and 0.53. In 66% of the cases the ratio was 0.49-0.51. THere were 54 posterior fossa masses evaluated by this technique. Determination of fourth ventricular position by this method proved to be of particular value in recognizing brainstem glioma, and in determining the site of origin of laterally placed posterior fossa masses.
Adult↗
Falx and interhemispheric fissure on axial CT: II. Recognition and differentiation of interhemispheric subarachnoid and subdural hemorrhage.
Interhemispheric hyperdensity or unenhanced computed tomography was originally considered a sign of subarachnoid hemorrhage, the "falx sign." It has since been identified as a normal feature and has also been seen with interhemispheric subdural hemorrhage. To determine the differential features of interhemispheric hemorrhage, 50 patients with subarachnoid hemorrhage and 32 patients with interhemispheric subdural hematomas were reviewed. Subarachnoid hemorrhage produced anterior interhemispheric hyperdensity only, with a zigzag contour and extension from the calvarium to the rostrum of the corpus callosum. Interhemispheric subdural hematomas produce unilateral crescentic hyperdensities that are largest in the posterior superior part of the fissure, behind and above the splenium of the corpus callosum. Interhemispheric hyperdensity in children is more complex. Because the anterior part of the fissure is narrow in younger patients, subarachnoid hemorrhage may go undetected. Likewise, interhemispheric subdural hematomas in children are smaller and more difficult to recognize. They produce asymmetric thickening of the falx shadow with extension over the tentorium. They are, however, of great significance since they are generally seen in abused patients and carry a poor prognosis.
Adolescent↗
The value of unenhanced scans in differentiating lesions producing ring enhancement.
Ring enhancement with contrast material is a nonspecific computed tomographic finding seen in a variety of lesions, including benign and malignant neoplasms, inflammation, infarction, and hematoma. This lack of specificity is especially troublesome in the differentiation of self-limiting disorders (infarction and hematoma) from progressive processes (tumor or abscess) potentially requiring surgical treatment. To determine whether more specific diagnoses were possible, 115 cases with ring lesions were retrospectively evaluated for the usefulness of precontrast scan features. The presence or absence of a complete ring proved useful. A complete ring on unenhanced scans effectively excluded self-limiting processes; it was seen in none of 18 infarcts or 11 hematomas. A complete ring on unenhanced scans occurred in 37 of 65 neoplasms, and was more common in metastatic disease (2:1) than in gliomas. A complete ring on unenhanced computed tomography was also seen in four of 15 pyogenic abscesses.
Brain Abscess↗