MR quantification of cerebral ventricular volume using a semiautomated algorithm.

PURPOSE: A semiautomated border identification algorithm, insensitive to user bias, is evaluated for accuracy and speed in the measurement of ventricular volumes from three-dimensional MR images. METHODS: A three-dimensional gradient-echo technique was implemented on a Signa clinical imaging system. Data from phantoms and patients were analyzed for volume using a segmentation algorithm designed with: 1) correction for partial volume averaging; 2) insensitivity to user bias; and 3) speed. Accuracy, precision, and intra- and interobserver variability were determined. RESULTS: Average error for phantom studies was 4% to 6%, or 1 to 2 cc across the volumes, which ranged from normal to mild hydrocephalus (< 60 cc). Patient studies showed intra- and interobserver error of 2.3% and 7.8%, respectively. The correction for partial volume averaging resulted in a threefold decrease in error. Data were acquired and reconstructed within 7 minutes. Experienced radiologists required less than 15 minutes to perform each analysis. CONCLUSIONS: This algorithm allows accurate measurement of ventricular volumes in an efficient, minimally supervised manner.

Anterior communicating artery collateral flow protection against ischemic change during carotid endarterectomy.

The purpose of this study was to determine whether preoperative angiographic patterns of collateral cerebral blood flow correlate with protection against intraoperative electroencephalographic (EEG) evidence of cerebral ischemia caused by carotid artery cross-clamping during carotid endarterectomy. Previous studies have shown that contralateral carotid artery occlusion and intracranial stenoses are associated with cerebral ischemia during carotid endarterectomy; however, the angiographic collateral flow patterns associated with cerebral ischemia have not been identified. This paper reports a retrospective study of 67 patients who underwent two- to four-vessel cerebral angiography followed by carotid endarterectomy with 16-channel EEG monitoring. The angiograms were reviewed for extracranial occlusive disease and collateral flow patterns, and the EEG recordings were analyzed for ischemic changes during carotid artery cross-clamping. Statistical analysis was by Fisher's exact test. Cross-filling of the anterior and middle cerebral arteries from the contralateral carotid artery through the anterior communicating artery correlated with a decreased incidence of EEG ischemic changes. Only 21% of patients with this collateral flow pattern showed ischemic changes compared to 50% of patients without this pattern (p < 0.03). Three angiographic findings occurring in combination on the side contralateral to surgery correlated with EEG ischemia: 1) occlusion of the contralateral internal carotid artery (five of seven or 71%, p < 0.03); 2) collateral flow from the external carotid circulation to the internal carotid circulation via the ophthalmic artery; and 3) collateral flow from the posterior circulation to the contralateral anterior circulation via the posterior communicating artery. The data presented here corroborate the correlation between contralateral carotid artery occlusion and cerebral ischemia during carotid endarterectomy. They also demonstrate that cross-filling of the anterior and middle cerebral arteries by the contralateral carotid artery protects against such ischemia. This collateral flow may serve as an indicator of tolerance to carotid artery cross-clamping.

DNA adducts and related biomarkers in populations exposed to environmental carcinogens.

Prevention of environmentally related cancer will be enhanced by the availability of sensitive early warning systems and by improvements in quantitative assessment of human risks. Accordingly, we have carried out a series of molecular epidemiologic studies aimed at validating a panel of biologic markers, including carcinogen-DNA and -protein adducts, sister chromatid exchange, micronucleus formation, DNA strand breaks, and DNA repair capacity. Results from three such studies illustrate the usefulness of these biomarkers in elucidating low-dose-response relationships, correlations between biomarkers, and the range of variation in biomarkers between individuals exposed to similar concentrations of carcinogens. Low-level workplace or ambient exposures to styrene, ethylene oxide, and polycyclic aromatic hydrocarbons (PAH) were associated with significant increases in both molecular dose of carcinogens (adducts) and various markers of preclinical effects. Correlations between biomarkers varied by exposure. For example, in the styrene study, sister chromatid exchange frequency was not correlated with any of the markers, in contrast to the studies of ethylene oxide and PAH. Significant molecular effects were observed not only in occupationally exposed people but also in residents of an area in Poland characterized by high levels of air pollution. For example, the mean PAH-DNA level in exposed residents (winter sample) was 30.4 adducts per 10(8) nucleotides. This level was significantly higher than that of adducts seen in summer samples from the same area (4.2/10(8), or in winter samples from residents of a rural area (11.01/10(8). Significant seasonal variation in PAH-DNA adduct formation in this group was consistent with recorded fluctuations in air pollution levels. Striking interindividual variation was observed in all three exposed populations.

Ferromagnetism and MR imaging: safety of carotid vascular clamps.

Metallic extracranial carotid vascular clamps of the Selverstone, Crutchfield, Poppen-Blaylock, Salibi, Kindt, and tantalum varieties have been placed for treatment of large, giant, or inoperable intracranial aneurysms. To ascertain what adverse effect, if any, MR imaging would have on these clamps, magnetic deflection at 1.5 T was measured for various carotid clamps. Marked magnetic deflection (and torque) was displayed by stainless steel Poppen-Blaylock clamps. Relatively mild magnetic deflection was displayed by the stainless steel Selverstone, Salibi, Crutchfield, and Kindt clamps. Three patients with previously placed carotid clamps (two Selverstone, one Salibi) and one patient with a nonferromagnetic tantalum carotid clip had cranial or cervical MR studies at field strengths ranging from 0.35 to 0.60 T. No patient experienced any discomfort or neurologic sequelae as a result of MR imaging. Although the ferromagnetic clamps created severe "black-hole" artifacts and image distortion within the cervical and facial regions, no significant image degradation was apparent during spin-echo imaging of the brain. The tantalum clip created a far smaller MR artifact than did ferromagnetic clamps and allowed effective spin-echo and gradient-echo imaging in the cervical region. Our findings indicate that most patients with carotid vascular clamps (and nonferromagnetic clips) can probably be imaged safely with MR.

Modified schema for classifying positive-pressure tympanograms.

Tympanograms with peaks located in the high-positive air pressure range (greater than or equal to 50 mm H2O) are infrequently recorded in clinical practice and have been little discussed in the literature. Such tympanograms accounted for 1.2% of a series of 8,011 tympanograms recorded at various times from 1,556 subjects ranging in age from 7 months through 12 years. Correlations between otoscopic diagnoses and tympanometric findings in the case of 65 of the high-positive air pressure tympanograms form the basis of the present report. Of the 65 high-positive air pressure tympanograms, 51 showed relatively high compliance (less than or equal to 5.5 Madsen units), and of these 46 (90%) were associated with ears considered normal otoscopically. Fourteen of the high-positive air pressure tympanograms showed low compliance (greater than 5.5 Madsen units), and of these, six (43%) were associated with ears considered normal, six (43%) with ears showing signs of acute infection, and two (14%) with ears in which the presence of effusion seemed probable. A previously presented zonal schema for classifying tympanograms has been modified on the basis of these findings.

Malignant melanoma in renal-transplant recipients.

14 patients who developed cutaneous malignant melanoma (CMM) after renal transplantation were studied. Histological review of the primary melanomas revealed that all 10 evaluable patients had a precursor naevus from which the CMM arose, 7 of which were dysplastic, and that 13 of the 14 patients had an abnormal host response to the tumour, characterised by absence of the usual lymphocyte/ macrophage infiltrate. These observations suggest that CMM in renal-transplant recipients evolves from precursor naevi in immunosuppressed patients who are unable to mount an appropriate cellular immune response to neoplastic cells. The clinical detection of dysplastic naevi offers an opportunity to identify in advance those immunosuppressed patients who are prone to melanoma and to modify their medical management accordingly.