Mathias Cohnen

Reliability and Validity of Noninvasive Imaging of Internal Carotid Artery Pseudo-Occlusion

BACKGROUND AND PURPOSE Our study evaluated noninvasive tests for the diagnosis of atheromatous internal carotid artery (ICA) pseudo-occlusion. METHODS Twenty patients (17 men, 3 women; mean age +/-SD, 64.3+/-11.6 years) with angiographically proven atheromatous ICA pseudo-occlusion (20 vessels) were prospectively examined with MR angiography (MRA; 2D and 3D time-of-flight techniques), color Doppler-assisted duplex imaging (CDDI) and power-flow imaging (PFI) with and without an intravenous ultrasonic contrast agent. As a control group, 13 patients (13 men; mean+/-SD age, 63.0+/-9.0 years) with angiographically proven ICA occlusion (13 vessels) were studied with the same techniques. For the determination of interobserver agreement (kappa statistics), the findings of each diagnostic technique were read by 2 blinded and independent observers who were not involved in patient recruitment and initial data acquisition. Specificity and sensitivity were calculated for all noninvasive techniques (observer consensus) in comparison to the standard of reference (intra-arterial angiography). RESULTS Interobserver reliabilities were kappa=0.86 for intra-arterial angiography, kappa=0.90 for unenhanced CDDI, kappa=0. 93 for enhanced CDDI, kappa=0.93 for unenhanced PFI, kappa=1.0 for enhanced PFI, kappa=0.93 for 2D MRA, and kappa=0.77 for 3D MRA, respectively (P<0.0001). Specificities and sensitivities were 0.92 and 0.70 for unenhanced CDDI, 0.92 and 0.83 for enhanced CDDI, 0.92 and 0.95 for unenhanced PFI, 1.0 and 0.94 for enhanced PFI, 1.0 and 0.65 for 2D MRA, and 0.89 and 0.47 for 3D MRA, respectively. CONCLUSIONS Advanced ultrasonographic techniques, especially PFI (with only 1 false-positive diagnosis of occlusion in the present series), can provide reliable and valid data to differentiate between ICA pseudo-occlusion and complete occlusion. In contrast, time-of-flight MRA at its present state is not capable of predicting minimal residual flow within a nearly occluded ICA.

Detection of changed regional cerebral blood flow in mild cognitive impairment and early Alzheimer's dementia by perfusion-weighted magnetic resonance imaging

The utility of perfusion-weighted magnetic resonance imaging (PW-MRI) for detecting changes in regional cerebral blood flow (rCBF) in patients with mild cognitive impairment (MCI) and early Alzheimers disease (AD) was evaluated. Thirteen cognitively normal (CN) elderly subjects, 35 mostly amnestic MCI subjects and 20 subjects with mild probable AD were enrolled. During i.v. injection of gadopentetate dimeglumine, a dynamic T2*-weighted single-shot EPI sequence was conducted using a 1.5-T scanner. Frontobasal (FROB), temporoparietal (TPAR), mesiotemporal (MTMP), anterior and posterior cingular (ACING, PCING), amygdala (AMYG), thalamus and cerebellar brain regions were studied. rCBF was computed from regional cerebral blood volume and arterial input function and normalised to white matter. Images were analysed by manually placed regions of interest using anatomical coregistration. Significant decreases of rCBF were detected in MCI vs. CN in MTMP (-23%), AMYG (-20%) and ACING (-15%) with no further decline in mild AD. In PCING hypoperfusion (-10%) was confined to AD. These hypoperfusional changes are a possible correlate of localised impairment of CNS function. In FROB no perfusion changes were observed between diagnostic groups, but hyperperfusion was observed in mild dementia stages, possibly reflecting functional compensatory mechanisms. These data suggest that PW-MRI detects specific changes in rCBF not only in AD, but also in amnestic MCI, a disorder suggested to largely represent a pre-dementia stage of AD. This method may thus be useful in both research and clinical applications to detect early functional brain changes in the pathogenesis of dementias.

CT-perfusion imaging of the human brain: Advanced deconvolution analysis using circulant singular value decomposition

According to indicator dilution theory tissue time-concentration curves have to be deconvolved with arterial input curves in order to get valid perfusion results. Our aim was to adapt and validate a deconvolution method originating from magnetic resonance techniques and apply it to the calculation of dynamic contrast enhanced computed tomography perfusion imaging. The application of a block-circulant matrix approach for singular value decomposition renders the analysis independent of tracer arrival time to improve the results.

Detection of colorectal polyps by multislice CT colonography with ultra-low-dose technique: comparison with high-resolution videocolonoscopy

BACKGROUND This prospective study compared multislice CT colonography with ultra-low-dose technique to high-resolution videocolonoscopy as the standard for detection of colorectal cancer and polyps. METHODS After standard bowel preparation, 115 patients underwent multislice CT colonography with an ultra-low-dose multislice CT colonography protocol immediately before videocolonoscopy. After noise reduction by using a mathematical algorithm, ultra-low-dose multislice CT colonographic images were analyzed in blinded fashion, and the results were compared with the results of high-resolution videocolonoscopy. RESULTS A total of 150 lesions were detected by high-resolution videocolonoscopy in 115 patients. For ultra-low-dose multislice CT colonography, sensitivities for detection of polyps less than 5 mm in size, 5 to 10 mm, and greater than 10 mm in diameter were 76%, 91%, and 100%, respectively. Although the sensitivity for detection of flat lesions was only 50%, the sensitivity and the specificity for detection of polyps 5 mm or greater in size were 94% and 84%, respectively. For adenomatous lesions greater than 5 mm in size, sensitivity was 94% and specificity was 92%. The overall specificity was 79%. The calculated effective radiation dose ranged between 0.75 and 1.25 mSv. CONCLUSIONS Compared with high-resolution videocolonoscopy, ultra-low-dose multislice CT colonography has excellent sensitivity and specificity for detection of colorectal lesions 5 mm or greater in size, and the radiation exposure is relatively low. However, before this technique can be generally recommended for colorectal screening, further improvement in the detection of flat and extremely small lesions must be achieved.

Wilson's Disease Tremor Is Associated with Magnetic Resonance Imaging Lesions in Basal Ganglia Structures

Wilsons disease (WD) is an inherited disorder of copper metabolism yielding marked motor deficits, including a severely disabling tremor. As a structural correlate of the disease, a variety of cerebral abnormalities has been revealed. However, the relationship between motor deficits and cerebral lesions has remained largely unknown. Here, we investigated correlation between WD tremor and cerebral magnetic resonance imaging (MRI) findings. Cerebral MRI abnormalities in 6 symptomatic WD patients were compared to findings in 6 asymptomatic WD patients and 10 healthy controls. All patients were treated with long‐term copper chelating therapy. Motor symptoms including tremor were determined by Unified Parkinsons Disease Rating Scale Part III (UPDRS‐III). MRI findings in symptomatic WD patients revealed significant symmetric T2*‐weighted hypointense signal alterations of globus pallidus, head of the caudate nucleus, and substantia nigra. In contrast, MRI of asymptomatic WD patients did not differ from healthy controls. Correlation analysis revealed a significant positive correlation between MRI basal ganglia lesions and UPDRS action tremor score. Our results demonstrate for the first time that Wilsons disease tremor is associated with lesions of the globus pallidus, the head of the caudate nucleus, and the substantia nigra.

Myocardial delayed contrast enhancement in patients with arterial hypertension: initial results of cardiac MRI

Purpose: In arterial hypertension left ventricular hypertrophy comprises myocyte hypertrophy, interstitial fibrosis and structural alterations of the coronary microcirculation. MRI enables the detection of myocardial fibrosis, infarction and scar tissue by delayed enhancement (DE) after contrast media application. Aim of this study was to investigate patients with arterial hypertension but without known coronary disease or previous myocardial infarction to detect areas of DE. Methods and material: Twenty patients with arterial hypertension with clinical symptoms of myocardial ischemia, but without history of myocardial infarction and normal coronary arteries during coronary angiography were investigated on a 1.0 T superconducting magnet (Gyroscan T10-NT, Intera Release 8.0, Philips). Fast gradient-echo cine sequences and T2-weighted STIR-sequences were acquired. Fifteen minutes after injection of Gadobenate dimeglumine inversion recovery gradient-echo sequences were performed for detection of myocardial DE. Presence or absence of DE on MRI was correlated with clinical data and the results of echocardiography and electrocardiography, respectively. Results: Nine of 20 patients showed DE in the interventricular septum and the anteroseptal left ventricular wall. In 6 patients, DE was localized intramurally and in 3 patients subendocardially. There was a significant correlation between myocardial DE and ST-segment depressions during exercise and between DE and left-ventricular enddiastolic pressure. Patients with intermittent atrial fibrillation showed a myocardial DE more often than patients without atrial fibrillation. Conclusion: In our series, 45% of patients with arterial hypertension showed DE on cardiac MRI. In this clinical setting, delayed enhancement may be due to coronary microangiopathy. The more intramurally localization of DE, however, rather indicates myocardial interstitial fibrosis.

The relation of regional cerebral perfusion and atrophy in mild cognitive impairment (MCI) and early Alzheimer's dementia

The spatial and temporal relations between regional cerebral blood flow (rCBF) and brain volume (rVOL) changes in incipient and early Alzheimers dementia (AD) are not fully understood. The participants comprised 30 subjects with mild cognitive impairment (MCI) and 15 with mild AD who were examined using structural and perfusion-weighted magnetic resonance imaging (MRI) at 1.5 Tesla. Hippocampus and amygdala volumes were measured by manual volumetry. A region-of-interest co-localisation method was used to calculate rCBF values. DNA samples were genotyped for apolipoprotein E (APO E). In comparisons of AD with MCI, rCBF was reduced in the posterior cingulum only, while profound rVOL reductions occurred in both right and left amygdala and in the right hippocampus, and as a trend, in the left hippocampus. Brain volumes of the hippocampus and the amygdala were uncorrelated with the respective rCBF variables in both MCI and AD. Hippocampal but not amygdalar volumes were associated with presence of one or two APOE epsilon4 alleles in MCI and mild AD, while there was no association of APOE epsilon4 allele with rCBF. These data support earlier indications that rCBF and rVOL changes are at least partly dissociated in the early pathogenesis of AD and heterogeneously associated with the APOE risk allele. The data also support the concept of functional compensatory brain activation and the diaschisis hypothesis as relevant in incipient and early AD.

Myocardial delayed contrast enhancement in patients with arterial hypertension: initial results of cardiac MRI.

PURPOSE In arterial hypertension left ventricular hypertrophy comprises myocyte hypertrophy, interstitial fibrosis and structural alterations of the coronary microcirculation. MRI enables the detection of myocardial fibrosis, infarction and scar tissue by delayed enhancement (DE) after contrast media application. Aim of this study was to investigate patients with arterial hypertension but without known coronary disease or previous myocardial infarction to detect areas of DE. METHODS AND MATERIAL Twenty patients with arterial hypertension with clinical symptoms of myocardial ischemia, but without history of myocardial infarction and normal coronary arteries during coronary angiography were investigated on a 1.0 T superconducting magnet (Gyroscan T10-NT, Intera Release 8.0, Philips). Fast gradient-echo cine sequences and T2-weighted STIR-sequences were acquired. Fifteen minutes after injection of Gadobenate dimeglumine inversion recovery gradient-echo sequences were performed for detection of myocardial DE. Presence or absence of DE on MRI was correlated with clinical data and the results of echocardiography and electrocardiography, respectively. RESULTS Nine of 20 patients showed DE in the interventricular septum and the anteroseptal left ventricular wall. In 6 patients, DE was localized intramurally and in 3 patients subendocardially. There was a significant correlation between myocardial DE and ST-segment depressions during exercise and between DE and left-ventricular enddiastolic pressure. Patients with intermittent atrial fibrillation showed a myocardial DE more often than patients without atrial fibrillation. CONCLUSION In our series, 45% of patients with arterial hypertension showed DE on cardiac MRI. In this clinical setting, delayed enhancement may be due to coronary microangiopathy. The more intramurally localization of DE, however, rather indicates myocardial interstitial fibrosis.

A rapid and reliable semiautomated method for measurement of total abdominal fat volumes using magnetic resonance imaging

The aim of this study was the development of a reliable and fast method to estimate total abdominal fat volumes (TAF) in diabetic subjects on the basis of T1-weighted MR images. Thirty-seven patients with diabetes were examined (age 48 +/- 13 y mean +/- SD). A semiautomated computer assisted software program was developed to quantify intraabdominal (IAF), subcutaneous (SCF), and total abdominal fat volumes (TAF). The variability of image analysis for fat measurements between two observers and within observers was assessed. Mean volumes (+/- SD) for IAF, SCF and TAF were 10.5 1 (+/- 5.0 1), 15.1 1 (+/-7.3 1) and 25.7 1 (+/-11.5 1), respectively. Inter- and intraobserver reliability was excellent (r = 0.999 to r = 1.0). Per patient, the analysis required nine minutes in addition to a scan duration of seven minutes. As this analytic method using T1-weighted MR images allows a fast and reliable quantification of TAF, IAF and SCF, it may serve as a valuable tool for respective studies in diabetic subjects.

Venous incompetence in erectile dysfunction: evaluation with color-coded duplex sonography and cavernosometry/-graphy

Abstract. The purpose of this study was to assess the accuracy of multi-parameter measurements with color-coded duplex sonography (CCDS) for the diagnosis of venous leakage in patients with erectile dysfunction. Sixty patients with repeated unsatisfactory reactions after intracavernous injection of vasoactive substances underwent CCDS. Following intracavernous injection of prostaglandin E1, peak systolic velocity (PSV), enddiastolic velocity (EDV), time averaged velocity (TAV), resistance index (RI), and pulsatility index (PI) were measured in the cavernous arteries over 30 min (one measurement per minute). The results were compared with independent measurements based on dynamic pharmaco-cavernosometry/cavernosography (DPCC). Dynamic pharmaco-cavernosometry/cavernosography revealed venous leakage in 33 patients. Of 48 patients with normal PSV ( > 25 cm/s), 25 had veno-occlusive dysfunction and the remainder presented normal venous function. No statistically significant differences between these groups were found in EDV, RI, and PI measurements. In contrast, differences in TAV were significant between patients with (mean 9.4 ± 4.6 cm/s) and without venous leakage (mean 5.5 ± 2.2 cm/s; p = 0.001). Analysis of relative frequencies revealed a broad overlap of EDV, TAV, RI, and PI measurements between both groups. Sensitivities and specificities determined from receiver-operating-characteristic curves were > 80 % and > 50 % for a TAV threshold of 5 cm/s, and an RI threshold of 1.0. Measurements of EDV, TAV, RI, and PI in patients with repeated unsatisfactory reactions on intracavernous prostaglandin injection are poor predictors of venous leakage and should not replace DPCC in the investigation of vasculogenic impotence.