The influence of carotid endarterectomy on cerebral blood flow in significant carotid stenosis-perfusion computed tomography study.

AIM: Carotid endarterectomy (CEA) is well recognized procedure in the treatment of patients with significant symptomatic internal carotid artery (ICA) stenosis. Operation reconstitutes physiologic blood flow in the ICA. The influence of CEA on cerebral perfusion (CP) is not well established. Some data suggest increased CP after stenosis correction however evidence in post-endarterectomy patients is scarce. Our aim was to investigate the influence of CEA in patients with symptomatic carotid stenosis on CP parameters by means of perfusion computed tomography (PCT). METHODS: Thirty-four patients with symptomatic severe carotid stenosis qualified for CEA were included. The baseline PCT of the brain according to standardized protocol was performed within 3 weeks prior to surgical procedure. The follow-up PCT was performed between 30-60th day postop. The following perfusion parameters were analyzed: cerebral blood flow (CBF), cerebral blood volume (CBV), peak enhancement intensity (PEI) and time to peak (TTP). Pre- and postoperative average values of these parameters were compared. RESULTS: No death/stroke occurred in the investigated group. Mean preoperative total CBF was 66.2 mL/100 g/min and was not dependent on the degree of the carotid stenosis or the presence of contralateral carotid artery stenosis. Mean postoperative total CBF was significantly lower (61.8 mL/100g/min, P<0.05). No significant changes in PEI, TTP and CBV were observed CONCLUSION: PCT of the brain reveals that CEA in patients with symptomatic carotid stenosis decreased total CBF especially in the contralateral hemisphere.

Coronary artery calcium distribution and interscan measurement variability in end-stage renal and coronary heart disease patients.

BACKGROUND: Coronary heart disease patients and end-stage renal disease patients have been documented to have an increased amount of coronary artery calcifications (CAC). PURPOSE: To evaluate the distribution of CAC and its influence on interscan variability of measurement in end-stage renal disease and coronary heart disease patients, proven to have calcifications. MATERIAL AND METHODS: 69 patients having CAC, including 34 with coronary heart disease and 35 with end-stage renal disease, were scanned twice with multidetector-row computed tomography (MDCT). Amount of CAC was determined as the number of calcified lesions (CN), total calcium score (CS), calcium volume (CV), and calcium mass (CM). Distribution of CAC was evaluated on a per-patient basis as the median CS and CM of a single lesion. Density of the calcifications was calculated as the patient's CM divided by CV. RESULTS: The overall median CS was 457.2, and the median CM was 75.6 mg. There were no significant differences in the number of calcified lesions, CS, or CM between the two groups. Both CS and CM of a single lesion, as well as the mean calcium density were lower in renal disease patients (P<0.05) than in coronary heart disease subjects. The relative interscan variability of coronary calcium measurement was higher in the renal disease group (P<0.05). There was a negative correlation between the calcium concentration and the relative interscan variability. CONCLUSION: The results indicate that the coronary calcium distribution influences the measurement interscan reproducibility, and the distribution may differ between end-stage renal disease patients and coronary heart disease patients, reflecting the dissimilar nature of coronary calcifications in those groups.

Reproducibility of dynamic computed tomography brain perfusion measurements in patients with significant carotid artery stenosis.

BACKGROUND: Perfusion computed tomography (PCT) determination is a minimally invasive and widely available technique for brain blood flow assessment, but its application may be restricted by large variation of results. PURPOSE: To determine the intraobserver, interobserver, and interexamination variability of brain PCT absolute measurements in patients with significant carotid artery stenosis (CAS), and to evaluate the effect of the use of relative perfusion values on PCT reproducibility. MATERIAL AND METHODS: PCT imaging was completed in 61 patients before endarterectomy, and in 38 of these within 4 weeks after treatment. Cerebral blood flow (CBF), cerebral blood volume (CBV), time to peak (TTP), and peak enhancement intensity (PEI) were calculated with the maximum slope method. Interexamination variability was evaluated based on perfusion of hemisphere contralateral to the treated CAS, from repeated examinations. Interobserver and intraobserver variability were established for the untreated side, based on pretreatment examination. RESULTS: Interobserver and intraobserver variability were highest for CBF measurement (28.8% and 32.5%, respectively), and interexamination variability was the highest for CBV (24.1%). Intraobserver and interobserver variability were higher for absolute perfusion values compared with their respective ratios for CBF and TTP. The only statistically significant difference between perfusion values measured by two observers was for CBF (mean 78.3 vs. 67.5 ml/100 g/min). The interexamination variability of TTP (12.1%) was significantly lower than the variability of other absolute perfusion measures, and the interexamination variability of ratios was significantly lower than absolute values for all the parameters. CONCLUSION: In longitudinal studies of patients with chronic cerebral ischemia, PCT ratios and either TTP or CBV are more suitable measures than absolute CBF values, because of their considerably lower inter- and intraobserver variability. Differences in CBF between two examinations as high as 30% may be considered as significant in such patients.

Phantom-calibrated versus automatic coronary artery mass quantification with multidetector-row computed tomography: in vitro and in vivo study.

BACKGROUND: Coronary artery calcium scoring is used as a method for cardiovascular risk stratification and monitoring of coronary heart disease. Automatic software-based calcium mass calculation has been proposed to improve the performance of the procedure. PURPOSE: To compare two algorithms of calcium mass measurement, automatic and phantom calibrated, with respect to correlation, measurement error, and accuracy in vitro and in vivo. MATERIAL AND METHODS: A cardiac phantom with calcium cylinder inserts was scanned with sequential non-overlapping collimation 4 x 2.5 mm, at 120 kV and 165 mAs. Fifty adults (37 men; mean age 46.2 years) were examined with the same settings using prospective electrocardiographic triggering to detect and quantify coronary artery calcifications. Calculations were performed with two methods: software-based automatic calcium mass measurement (ACM) and phantom-calibrated calcium mass measurement (CCM). RESULTS: The total phantom calcium masses measured with ACM and CCM were 175.0+/-13.8 mg and 163.0+/-4.4 mg, respectively (P<0.0001), and ACM produced a higher mean error (4.5 vs. 3.2; P<0.05). Results of ACM and CCM were strongly correlated to each other (R=0.73-0.96; P<0.0001). Mean image noise in the patient study was 8.72+/-1.68 HU. Results of patient calcium scoring with ACM and CCM were significantly different (median 70.3 mg and 59.7 mg, respectively; P<0.0001), with a mean systematic error of 17.5% (limit of agreement between 14.6% and 20.4%). The use of ACM resulted in an altered quartile classification for 14% of patients, as compared to CCM; all of these patients were classified into a higher category. CONCLUSION: Our data indicate that multidetector-row computed tomography coronary calcium mass determination based on dedicated phantom calibration shows lower measurement error than an automatic software-based calculation method. The tested automatic software does not yet seem to be a reliable option for calcium mass measurement.