Correlation of regional cerebral blood flow measured by stable xenon CT and perfusion MRI.

PURPOSE: The purpose of this work was to investigate the validity of perfusion MRI in comparison with stable xenon CT for evaluating regional cerebral blood flow (rCBF). METHOD: The rCBF was measured by xenon CT and perfusion MRI within a 24 h interval in 10 patients (mean +/- SD age 63 +/- 10 years). For perfusion MRI, absolute values of rCBF were calculated based on the indicator dilution theory after injection of 0.1 mmol/kg of Gd-DTPA. Eight to 10 regions of interest (37 mm2) were located in the white and gray matter on the rCBF images for each of the 10 patients. RESULTS: The mean +/- SD values of rCBF in gray matter were 48.5 +/- 14.1 ml/100 g/min measured by xenon CT and 52.2 +/- 16.4 ml/100 g/min measured by perfusion MRI. In the white matter, the rCBF was 22.6 +/- 9.1 ml/100 g/min by xenon CT and 27.4 +/- 6.8 ml/100 g/min by perfusion MRI. There was a good correlation of rCBF values between perfusion MRI and xenon CT (Pearson correlation coefficient 0.83; p < 0.0001). CONCLUSION: Comparable to xenon CT, perfusion MRI provides relatively high resolution, quantitative local rCBF information coupled to MR anatomy.

[Contribution of nuclear medicine to the diagnosis of recurrent brain tumors and cerebral radionecrosis]. / Beitrag der Nuklearmedizin zur Diagnostik des Hirntumorrezidivs und der zerebralen Radionekrose.

The evaluation of brain tumor recurrence and therapy-induced benign changes following surgery and/or irradiation is a diagnostic challenge for imaging methods based on either morphology (cCT/MRI) or function (SPECT/PET). Current literature and the present data of our own patients demonstrate the diagnostic efficiency of IMT-SPECT and FDG-PET in the detection of recurrence and in-vivo grading. Thirty-nine patients suspected of brain tumor recurrence at follow-up were studied by FDG-PET and IMT-SPECT. Thirty-four of 39 patients showed recurrences; in 12 cases even a change in the grade of malignancy was observed. All high-grade recurrences could be confirmed by either methods. IMT-SPECT showed a higher sensitivity in detecting low-grade tumors at recurrence. In contrast to IMT-SPECT, FDG-PET supports sufficient in-vivo grading. Both methods can be used to differentiate between tumor recurrence and radionecrosis. In conclusion the results of our study demonstrate the efficiency of IMT-SPECT and FDG-PET in confirming recurrences and determining the actual tumor grade.

Influence of the angiographic internal carotid artery stenosis assessment method on indicating carotid surgery.

BACKGROUND: To estimate the influence of different kinds of angiographic internal carotid artery (ICA) stenosis assessment methods on clinical decision making on carotid surgery. METHOD: One hundred angiographically proven ICA lesions in 65 patients (54 men, 11 women, mean age +/- SD, 64 +/- 8 years) were evaluated by simultaneous biplane angiography. The angiograms were analyzed using three kinds of linear diameter reduction methods [North American (NASCET), and European (ECST) carotid surgery trial method, common carotid artery method (CC)], and five area reduction methods reflecting more accurately the anatomical degree of stenosis [squared NASCET, ECST and CC (N2, E2, CC2), combined stenosis estimation of two projections (NASCET-bi, ECST-bi)]. All lesions were additionally evaluated by continuous wave (cw-)Doppler ultrasound prior to angiography. Between method agreement on classifying the lesions into stenosis < 70% and into stenosis > or = 70% was calculated by means of kappa statistic. RESULTS: The degree of stenosis (median and inter-quartile range) ranged between 65% (38-82) by means of NASCET and 91% (87-93) by means of CC2. Thirty-seven ICA stenoses would have been operated on using NASCET, but 82 using CC2. Between method agreement on assessing high grade ICA stenosis ranged from poor (kappa value 0.17 for the pair NASCET/CC2) to excellent (kappa value 0.92 for the pair N2/NASCET-bi). Cw-Doppler ultrasound showed a good agreement (kappa value 0.72-0.80) with all angiographic methods using an area reduction formula apart from CC2. The agreement was moderate between cw-Doppler and NASCET and ECST, respectively. CONCLUSION: The clinical decision to operate on an ICA stenosis will strongly be influenced by the angiographic method used. Because reliable clinical data exist only for the NASCET and ECST method these two angiographic stenosis assessment method should be used for clinical decision making.

Multiple cerebral aneurysms in identical twins.

We report the finding of multiple cerebral aneurysms in a pair of identical twins. One twin had subarachnoid hemorrhage and intracerebral hematoma; her sister had subarachnoid hemorrhage and intraventricular bleeding. Angiography in both cases showed multiple cerebral aneurysms. It is appropriate to recommend a cerebral angiographic examination of an asymptomatic twin after the other twin has suffered an aneurysmal subarachnoid hemorrhage.

[Perfusion-MRI in cerebral infarct]. / MR-Perfusionsuntersuchung beim Hirninfarkt.

PURPOSE: To investigate the hemodynamic changes in patients with acute cerebral stroke by perfusion MRI. MATERIAL AND METHODS: In 12 patients with acute stroke in the territory of the middle cerebral artery, perfusion MRI was performed. Peak time, mean transit time, regional cerebral blood volume and regional cerebral blood flow were calculated in the infarction, the peri-infarction area and the contralateral hemisphere. RESULTS: In the infarction the mean blood flow was 29 ml/100 g/min, compared to about 40 ml/100 g/min in the peri-infarction area and the contralateral hemisphere. In two patients increased cortical blood flow was found in the infarction due to luxury perfusion. The cerebral blood volume was reduced in the infarction, but significantly increased, to 7.3 ml/100 g, in the peri-infarction tissue. CONCLUSION: Perfusion MRI allows one to differentiate various patterns of perfusion disorders in patients with acute cerebral stroke. The resulting data may be helpful in describing the pathophysiologic mechanisms of compensation.

Patient doses from standard and spiral CT of the head using a fast twin-beam system.

Investigations were carried out on a novel type of CT scanner, the Elscint CT-Twin, for comparison and optimization of the patient dose caused by standard and spiral CT of the head. For selected CT parameters, organ doses of the Alderson head phantom were measured with thermoluminescent dosemeters. Organ doses were also calculated using the normalized computed tomography dose index (CTDIn) combined with organ dose conversion factors. Then effective doses were deduced. For standard and spiral head CT examinations brain, red bone marrow and bone surface receive the main contributions to effective dose. This amounts to 0.9 and 0.8 mSv for routine standard and spiral CT, respectively, if the combination "dual-slice" mode, 250 mAs per rotation, 5 mm nominal slice width and a packing factor of 1.0, is applied. In clinical practice, for spiral CT head examinations the effective dose has been reduced to 0.7 mSv while guaranteeing adequate image quality, as assessed by determination of low and high contrast resolution. The effective dose values obtained are in the lower part of the range of values published in the literature. The dose determinations showed that, from the aspect of radiation protection of the patient, CT examinations with nominal slice widths between 0.5 and 1 mm as well as packing factors greater than 1.0 should be restricted to really necessary cases.

[Value of CT-angiography in diagnosis of cerebral sinus and venous thromboses]. / Stellenwert der CT-Angiographie in der Diagnostik von zerebralen Sinus-und Venenthrombosen.

Dural sinus thrombosis is not uncommon. Due to the nonspecific symptomatology, as well as the manifold etiology, clinical diagnosis may be difficult. In these cases imaging procedures are frequently crucial in deciding how to proceed and how to treat. The aim of our study was to evaluate the diagnostic utility of helical CT in the detection of dural sinus thrombosis. In 20 patients with clinically suspected thrombosis CT angiography was performed. In 6 patients dural sinus thrombosis was diagnosed. In order to acquire also arterial vessels, a short delay of about 22 s after the onset of the application of contrast medium was selected. By this method we found an occlusion of the MCA in two patients with clinically suspected sinus thrombosis. In all patients the transverse slices and the multiplanar reconstructions showed filling defects or an "empty delta" sign. With irregular outlines the thrombus could be depicted over the complete course of the sinus. The MIP reconstructions were particularly helpful in the evaluation of the vessel anatomy and the pathological collateral venous drainage. In three patients MR angiograms were available for comparison. The smaller veins, such as the v. vermis inferior, were less clearly depicted than in CT angiography. CT angiography is a fast and reliable method to exclude or verify a sinus thrombosis. It can be performed immediately after non-enhanced CT. According to our present experience CT angiography is sufficient for the diagnosis of a sinus thrombosis.

Regional association of developmental venous anomalies with angiographically occult vascular malformations.

This study reviews the neuroradiological findings of 43 patients with a developmental venous anomaly in order to discuss the clinical significance of this entity. All patients underwent unenhanced and contrast-enhanced computer tomography and magnetic resonance tomography, as well as selective angiography, and were followed for at least 2 years. In 40% (17 of 43) of patients a cryptic vascular malformation was found in the proximity to the developmental venous anomaly. Neurological symptoms were present in 8 of 17 patients (47%) in this group. Patients with an isolated developmental venous anomaly had symptoms in 19% (5 of 26), but none of them had experienced a hemorrhage. Magnetic resonance was the most sensitive method for the diagnosis of both types of lesions and alterations of the adjacent parenchyma. These results further support that developmental venous anomalies represent a clinically benign entity. However, patients with an association of a developmental venous anomaly and a cryptic vascular malformation are at risk for hemorrhage from their angiographically occult vascular malformation. Magnetic resonance proved to be the imaging modality of choice for both entities and is appropriate for diagnosis and follow-up.

[Adolf Bengel--the second inventory of lumbar pneumoencephalography]. / Adolf Bingel--Der zweite Erfinder der lumbalen Pneumenzephalographie.

In 1918, Walter Dandy reported contrasting liquor-filled spaces by air for the first time. He published the results in eight pneumencephalographies after lumbar air application in 1919. Without knowing about Dandy's papers Adolf Bingel performed his first lumbar encephalography in 1919. In contrast to Dandy, based on this experience Bingel developed ventricular imaging, improved the technique of lumbar puncture and did a scientific evaluation of the results.

Assessment of cerebral vasomotor reactivity by transcranial Doppler ultrasound and breath-holding. A comparison with acetazolamide as vasodilatory stimulus.

BACKGROUND AND PURPOSE: Evaluating cerebrovascular vasomotor reactivity seems to be of prognostic relevance for patients with occlusive internal carotid artery disease. To evaluate its clinical usefulness, the recently introduced breath-holding maneuver as a carbon dioxide-dependent vasodilatory stimulus was compared with the acetazolamide challenge by means of transcranial Doppler ultrasound and stable xenon-enhanced computed tomography. METHODS: In a total of 134 middle cerebral arteries of 74 patients (mean +/- SD age, 62 +/- 9 years) with unilateral or bilateral occlusive carotid artery disease, vasomotor reactivity was estimated by the increase of middle cerebral artery mean blood velocity by transcranial Doppler ultrasound, comparing the breath-holding maneuver and 1 g IV acetazolamide as vasodilatory stimuli. The carotid artery findings were classified as normal, stenosis of 50% to < 70%, 70% to < 90%, 90% to 99%, and occlusion. Eighteen of the 74 patients additionally underwent stable xenon-enhanced computed tomography to calculate the increase of mean cortical regional cerebral blood flow in the middle cerebral artery territory after acetazolamide stimulation. RESULTS: The percentage of mean regional cerebral blood flow changes (n = 36 hemispheres) correlated best with the absolute mean blood velocity changes while breath-holding (P = .007, r = .4332). The absolute mean regional cerebral blood flow changes correlated best with the percentage of mean blood velocity changes after acetazolamide stimulation (P = .004, r = .4580). On all 134 middle cerebral arteries, both vasodilatory stimuli correlated highly significantly (P < .0001) when comparing increases in absolute (r = .5448) or relative (r = .3516) mean blood velocity. Both stimulation techniques similarly indicated significantly reduced vasomotor reactivity with increasing degree of internal carotid artery lesions (P < or = .01). However, the acetazolamide challenge differentiated more accurately between the various groups of internal carotid artery findings. CONCLUSIONS: The assessment of vasomotor reactivity by transcranial Doppler ultrasound correlates with cerebral blood flow changes even when different vasodilatory stimuli are used. In cooperative patients the breath-holding maneuver as vasodilatory stimulus seems clinically useful for a first estimation of cerebral vasomotor reactivity.

[Information improving secondary evaluation procedures in neuroradiology]. / Informationsverbessernde sekundäre Auswerteverfahren in der Neuroradiologie.

The development of special computer and software systems has exerted great influence on computer-assisted image processing in neuroradiology. In this article we try to give an overview of the present and future applications. The applications can be subdivided into segmentation, image analysis, three-dimensional imaging and image fusion. Segmentation plays an important role, because it is frequently the basis for the other methods. Image analysis, like planimetry, volumetry or the calculation of angles, is already used in clinical applications. In this way the course of diseases can be checked objectively. Three-dimensional imaging is especially useful in the planning of surgical and stereotactic approaches. The results and value of three-dimensional imaging depend on the segmentation technique. Therefore, they are evaluated differently. Image fusion allows the simultaneous presentation of image data of different modalities. In particular, the image fusion of morphological findings and functional parameters is applied in clinical neuroradiology. Our experience with these methods suggests that computer-assisted image processing will be of considerable help in neuroradiology.

[Neuroradiologic diagnosis of intracranial epidermoid tumors]. / Zur neuroradiologischen Diagnostik der intrakraniellen Epidermoide.

Intracranial epidermoids are primarily extracerebral congenital cysts. Intra- and extradural types are differentiated: intradural lesions originate in the intracranial CSF spaces, and extradural lesions in the bony skull. Epidermoids increase in size passively as the result of an increase in the cyst volume and not because of active growth. Clinically epidermoids behave like benign, slow-growing cerebral tumours. Differential diagnosis includes other cysts and cystic tumours. Neuroradiologically epidermoids present as polycystic lesions showing extensive growth in the extracerebral CSF spaces and secondary invagination of the brain. On CT and MR, despite the high cholesterol content, epidermoids show the characteristics of liquor and not those of fat. It can be shown that the typical CT and MR appearance of an epidermoid is due to the different proportions of CSF in the cyst content, which results from diffusion or dehiscence of the cyst capsule. The present study was based on analysis of 6 cases selected from a total of 29 patients with CNS epidermoids.

[Magnetic resonance tomography in epidural and subdural spinal hematoma]. / Magnetresonanztomographie bei epiduralen und subduralen spinalen Hämatomen.

Epidural and subdural spinal hematomas were previously diagnosed by myelography and computed tomography (CT). Recent reports indicate that noninvasive detection is possible with magnetic resonance imaging. We report on nine patients who were investigated by magnetic resonance imaging (MRI) prior to surgery for epidural and subdural spinal hematoma. The MR examinations were performed on 1.5-T and 1-T units. We used surface coils and employed T1-, PD- and T2-weighted spin echo sequences and a T2*-weighted gradient echo sequence. CT was available in four patients and myelography in two patients. Surgical correlation was available in all patients. The hematomas were located in the cervical spine (n = 2), thoracic spine (n = 6) and lumbar spine (n = 2). They were epidural in five patients and subdural in four. Blinded reading correctly identified all five epidural hematomas and three of the subdural hematomas; one subdural hematoma was misjudged as epidural. Peracute hematomas (< 24 h) in three patients appeared isointense or slightly hyperintense on T1-weighted images and had mixed signal intensity on T2- and T2*-weighted images. Acute hematomas (1-3 days) in four patients were also isointense on T1-weighted images but were more hypointense on T2- and T2*-weighted images. Chronic hematomas in two patients (7 days and 14 days) were hyperintense on all sequences. Differentiation between epi- and subdural hematomas required transverse T2*-weighted gradient echo sequences. Our results underline that MRI at 1 and 1.5 T is capable of identifying epidural and subdural spinal hematoma in the acute and peracute stage.(ABSTRACT TRUNCATED AT 250 WORDS)

[Internal carotid artery aneurysm in the petrous canal]. / Carotis-Interna-Aneurysma im Felsenbeinkanal.

Internal carotid aneurysm in the petrous canal are rarely observed. According to our knowledge there are only 24 reported cases. We present the case of a 47-year old woman. The clinical, radiological and histological findings are discussed.

[Clinical value of the ultrafast gradient echo sequence "Quickflash"]. / Klinische Wertigkeit der ultraschnellen Gradienten-Echo-Sequenz "Quickflash".

It is possible to develop faster sequences with 6 mT/m gradient field strength. However, the short gradient switch times which are advantageous for a better image contrast cannot be achieved. Using longer measurement times the influence of the preparation pulses is less dominant. The image quality of the quickflash is poorer than that of conventional SE and GE sequences. In some cases, especially for outline views and in the evaluation of Gd inflow into pathologic tissue or in restless patients, we use the quickflash in clinical routine.

[Radionuclide cisternography: SPECT- and 3D-technique]. / Radionuklidzisternographie: SPECT- und 3D-Technik.

Radionuclide cisternography is indicated in the clinical work-up for hydrocephalus, when searching for CSF leaks, and when testing whether or not intracranial cystic lesions are communicating with the adjacent subarachnoid space. This paper demonstrates the feasibility and diagnostic value of SPECT and subsequent 3D surface rendering in addition to conventional rectilinear CSF imaging in eight patients. Planar images allowed the evaluation of CSF circulation and the detection of CSF fistula. They were advantageous in examinations 48 h after application of 111In-DTPA. SPECT scans, generated 4-24 h after tracer application, were superior in the delineation of basal cisterns, especially in early scans; this was helpful in patients with pooling due to CSF fistula and in cystic lesions near the skull base. A major drawback was the limited image quality of delayed scans, when the SPECT data were degraded by a low count rate. 3D surface rendering was easily feasible from SPECT data and yielded high quality images. The presentation of the spatial distribution of nuclide-contaminated CSF proved especially helpful in the area of the basal cisterns.

[Venous anomalies of the brain. The clinical significance of the so-called venous angioma]. / Venenanomalien des Gehirns. Zur klinischen Bedeutung des sogenannten venösen Angioms.

In contrast to angiography, MRI not only allows the diagnosis of DVA (developmental venous anomaly, so-called venous angioma), but also shows up cavernomas and other angiographically occult vascular malformations. It also differentiates between DVAs and occult true malformations. This has completely changed the pathological assessment of DVAs. In a retrospective study on 31 patients with angiographically proven DVAs neighbouring cavernoma was a frequent finding (15 patients, 48% group I). Symptoms caused by cavernoma were present in 6 (40%) of these 15 patients. The following associations were also found: cerebral arterial aneurysm (2), spinal arterio-venous dural fistula (1), dermal haemangioma (1), Klippel-Trénauny syndrome (1). Only 16 (52%) of the 31 cases with DVA were free of associated cavernoma (group II). Only 3 (19%) of these patients with a solitary DVA were symptomatic. In our series we have seen no case of bleeding from a DVA. A DVA is a vascular anomaly characterized, like other anomalies, by reduced resistance and limited capacity for regulation and adaptation. In rare cases this can result in haemodynamic disturbances, thrombosis and ischaemia. Wall rupture with bleeding does not occur in DVA. It must be assumed that bleeding reported in patients with DVAs before the availability of MRI resulted from an associated true vascular malformation in most cases.