Classification of carotid stenosis by millimeter CT angiography measures: effects of prevalence and gender.

BACKGROUND AND PURPOSE: Previous studies quantifying moderate and severe carotid stenosis by direct millimeter measures on CT angiography (CTA) did not consider how prevalence and gender may influence classification cutoff values. MATERIALS AND METHODS: Three hundred nineteen carotid arteries were evaluated in consecutive patients with known or suspected carotid artery disease. Millimeter measures were obtained of the stenotic carotid bulb lumen and distal internal carotid artery (ICA). Interclass correlation coefficients (ICC) defined interobserver and intraobserver agreement. North American Symptomatic Carotid Endarterectomy Trial (NASCET)-style percent stenosis ratios were calculated per carotid artery and used in linear regression and receiver operating characteristic (ROC) curve analysis to define equivalent millimeter quantification and classification values. Likelihood ratios and prevalence-specific positive/negative predictive values (PPV/NPV) were calculated to determine the most appropriate millimeter cutoff values to classify stenosis. RESULTS: Interobserver agreement was excellent for stenosis measures (0.90) and good for distal ICA measures (0.79). Gender-specific regression curves and ROC curves indicated that millimeter stenosis is an excellent tool to quantify and classify carotid stenosis. Assuming a 10% prevalence of severe stenosis, we found that the cutoff value maximizing NPV and PPV was 1.1 mm for both genders (female: PPV = 86.2, NPV = 97.7; male: PPV = 83.2, NPV = 95.9). Assuming a 40% prevalence of moderate stenosis, we found that the cutoff values differed between genders: female = 2.0 mm (PPV = 91.3, NPV = 91.5), male = 2.1 mm (PPV = 91.6, NPV = 92.4). Specific millimeter cutoffs will vary depending upon the clinical scenario, prevalence, and gender. CONCLUSIONS: Direct millimeter stenosis measures are an excellent tool to classify moderate and severe carotid artery stenosis. Millimeter classification cutoff values that best approximate NASCET classifications vary depending on prevalence and gender.

Diagnosing carotid stenosis near-occlusion by using CT angiography.

BACKGROUND/PURPOSE: Identification of carotid near-occlusion is essential before calculation of percent stenosis because stroke risk is lower than other severe stenosis and the treatment benefit is less. Calculations with reduced distal diameters are fallacious. CT angiography (CTA) is convenient and accurately quantifies internal carotid artery (ICA) stenosis. METHODS: In a blinded protocol, 268 carotid artery CTAs for known or suspected carotid disease were independently evaluated by 2 neuroradiologists. All carotid arteries were measured in millimeters at the narrowest diameter of the stenotic bulb, distal ICA well beyond the tapering bulb, and distal external carotid artery (ECA). Near-occlusions were independently identified, with disagreements settled by consensus meeting. Receiver operating characteristic (ROC) curve analysis defined the threshold values that best predicted near-occlusion according to (1) ICA stenosis, (2) distal ICA, (3) distal ICA: contralateral distal ICA, and (4) distal ICA: ECA. Paired permutations of variables were evaluated. RESULTS: Forty-two near-occlusion distal ICAs were identified. The ROC-derived threshold values determined near-occlusion carotid stenosis with a sensitivity range, 90.2-97.3; specificity, 84.1-89.9; positive predictive value (PPV), 61.3-66.7; and negative predictive value (NPV), 96.7-99.4. Ranges for paired permutations were also determined: sensitivity, 82.9-91.9; specificity, 95.4-96.8; PPV, 78.6-85.7; and NPV, 96.3-98.4. CONCLUSIONS: Threshold values provide guidelines for CTA interpretation when assessing carotid artery disease and the presence of near-occlusion. Ultimate identification of near-occlusion requires the interpreter's judgment, with attention to the following criteria: (1) notable stenosis of the ICA bulb and (2) distal ICA caliber reduction compared with (A) expected size, (B) contralateral ICA, and (C) ipsilateral ECA. Near-occlusion distal ICAs can be reliably identified on CTA.

Correlation of carotid stenosis diameter and cross-sectional areas with CT angiography.

PURPOSE: Carotid stenosis quantification traditionally uses measurements of narrowest stenosis diameter. The stenotic carotid lumen, however, is often irregularly shaped. New PACS workstation tools allow for more precise calculation of carotid geometry. We compare the narrowest stenosis diameter with 2D area stenosis measurements, with the hypothesis that the narrowest diameter is a good predictor of the more precise area measurement. METHODS: Two neuroradiologists evaluated 178 stenosed carotids in a blinded protocol. Carotid artery bulb stenosis was identified on axial CT angiography and measured in millimeters at its narrowest diameter. An AGFA Impax 4.5 Volume Tool (VT) using Hounsfield units was used to estimate the cross-sectional area of the contrast luminogram. Pearson correlation coefficients were calculated between the millimeter stenosis and the VT area, as well as between the VT area and the calculated area (radius based on narrowest diameter). Regression analysis was performed with the VT area and narrowest diameter datasets. RESULTS: Excellent interobserver correlation (correlation coefficients, 0.71-0.85; 2-tailed significance = .01) permitted averaging of measurement data. There is excellent correlation between the VT area and the narrowest diameter (correlation coefficient, 0.88; n = 176). The VT area was generally greater than the calculated area by an average of 2.77 mm2. There was excellent correlation between the VT area and the calculated area (correlation coefficient, 0.87; n = 176). Regression analysis shows the ability of the diameter measurements to predict corresponding area stenosis. CONCLUSION: Although some carotid stenoses are irregularly shaped and noncircular, measurement of the narrowest stenosis is a reasonably reliable predictor of the cross-sectional area.

Quantification of carotid stenosis on CT angiography.

PURPOSE: Carotid artery stenosis quantification uses percent diameter ratios from conventional angiography. Multidetector high-speed CT angiography (CTA) allows direct millimeter measurement of carotid stenosis. We hypothesize a linear relationship between millimeter stenosis measurements and derived percent, alleviating cumbersome ratio calculations. METHODS: Two neuroradiologists separately reviewed CTAs of 268 carotid arteries, blinded to other information. The narrowest portion of each carotid stenosis was measured in millimeters from axial source images. Distal internal carotid arteries (ICAs) were measured beyond the bulb, where walls are parallel. North American Symptomatic Carotid Endarterectomy Trial (NASCET)-style ratios were calculated for each ICA, except for suspected near-occlusions. Interobserver agreement was calculated for all measurements. Correlation coefficients were calculated comparing millimeter and derived percent stenosis, followed by regression analysis. Sensitivity and specificity values tested validity. RESULTS: Interobserver agreement correlations were excellent, from 0.78 to 0.89 (2-tailed P

Studying non-Hodgkin's lymphoma in two Oklahoma counties: a call for centralized cancer data management.

Anecdotal evidence for an increased incidence of non-Hodgkin's lymphoma (NHL) had been informally discussed within several clinical practices in north central Oklahoma. This study was conducted to determine the incidence rates of NHL in Garfield and Kingfisher counties and to evaluate whether these counties represented unique cancer clusters. Data were collected from medical records and tumor registries in 22 area hospitals between 1990-1994. The annual incidence rate per 100,000 persons for Garfield county was 15.51 (95% CI: 10.9-20.1), and for Kingfisher county, 24.22 (95% CI: 12.4-36.1). Both of these rates are increased from the national incidence rate of 13.7 cases of NHL per 100,000 persons, suggesting a significant clinical impact. However, a statistical significance was not detected given the conservative methodology and the small populations involved. The difficulties of performing community-based research, the need for epidemiological studies to reduce clinical experience bias, and the need for centralized cancer data management are discussed.

Penile erection: a reflection of sexual arousal and arousability in male chimpanzees.

A study was conducted to determine if sexual motivation in male chimpanzees, defined by the two components, sexual arousal and arousability, could be quantified by measuring penile erection during laboratory pair-tests of sexual behavior. Sexual arousal, the momentary level of sexual excitation, was quantified by single measurements on a scale of penile erection. Sexual arousability, the propensity for arousal, was quantified by the rate of approach to full erection and by mean erection scores. Sexual arousability, as defined, was related to the frequency of male courtship displays, copulations, and ejaculations, which were highest at midcycle and positively correlated with a quantitative measure of female anogenital swelling. Sexual arousal was negatively correlated with continued exposure to the female and least variable during midcycle. These operational definitions of sexual motivation in the male chimpanzee facilitate comparative research in which analogous indexes of sexual motivation are required such as when extrapolating from animal to human.