CT perfusion in acute ischemic stroke: a comparison of 2-second and 1-second temporal resolution.

BACKGROUND AND PURPOSE: CT perfusion data sets are commonly acquired using a temporal resolution of 1 image per second. To limit radiation dose and allow for increased spatial coverage, the reduction of temporal resolution is a possible strategy. The aim of this study was to evaluate the effect of reduced temporal resolution in CT perfusion scans with regard to color map quality, quantitative perfusion parameters, ischemic lesion extent, and clinical decision-making when using DC and MS algorithms. MATERIALS AND METHODS: CTP datasets from 50 patients with acute stroke were acquired with a TR of 1 second. Two-second TR datasets were created by removing every second image. Various perfusion parameters (CBF, CBV, MTT, TTP, TTD) and color maps were calculated by using identical data-processing settings for 2-second and 1-second TR. Color map quality, quantitative region-of-interest-based perfusion measurements, and TAR/NVT lesions (indicated by CBF/CBV mismatch) derived from the 2-second and 1-second processed data were statistically compared. RESULTS: Color map quality was similar for 2-second versus 1-second TR when using DC and was reduced when using MS. Regarding quantitative values, differences between 2-second and 1-second TR datasets were statistically significant by using both algorithms. Using DC, corresponding tissue-at-risk lesions were slightly smaller at 2-second versus 1-second TR (P < .05), whereas corresponding NVT lesions showed excellent agreement. With MS, corresponding tissue-at-risk lesions showed excellent agreement but more artifacts, whereas NVT lesions were larger (P < .001) compared with 1-second TR. Therapeutic decisions would have remained the same in all patients. CONCLUSIONS: CTP studies obtained with 2-second TR are typically still diagnostic, and the same therapy would have been provided. However, with regard to perfusion quantitation and image-quality-based confidence, our study indicates that 1-second TR is preferable to 2-second TR.

Accuracy of perfusion-CT in predicting malignant middle cerebral artery brain infarction.

BACKGROUND: We performed a prospective study on patients with middle cerebral artery(MCA) ischemic stroke to evaluate the accuracy of perfusion-CT imaging(PCT) to predict the development of malignant brain infarction (MBI). METHODS: 106 patients(women 37 %, mean age 65 years)underwent native cranial computed tomography (CCT), CT angiography(CTA) and PCT after a median of 2 h after stroke onset. We assessed the patency of the MCA and the area of tissue ischemia (AIT)according to cerebral blood flow(CBF), cerebral blood volume (CBV) and time-to-peak (TTP)maps. Optimum sensitivity, specificity,positive (PPV) and negative predictive values (NPV) were calculated for the end-point MBI (= midline shift > 5 mm or decompressive surgery) by means of receiver operating characteristics(ROC). RESULTS: 20 patients (19 %)developed a MBI. In these patients,a larger AIT was found in all perfusion maps as compared to the remaining patients (p < 0.001). All perfusion maps had a very high NPV (95.4-98.4 %), a high sensitivity (85-95 %) and specificity (71.6-77.9 %) and only a moderate PPV (44-47.4 %). Best prediction was found for CBF maps with AIT of > 27.9 % of the hemisphere. CONCLUSION: PCT allows the discrimination of patients without a relevant risk for MBI from those having a 50 % risk of MBI development. Due to the high sensitivity and specificity, PCT is a reliable tool in detecting MBI. Because of PCT's better availability, it is the method of choice at present for an early risk stratification of acute stroke patients.

[Magnetic resonance imaging findings of the brain in adult HIV and AIDS patients]. / Magnetresonanztomografische Befunde des Gehirns bei adulten Patienten mit HIV und AIDS.

The spectrum of pathology affecting the central nervous system (CNS) in patients suffering from acquired immunodeficiency syndrome (AIDS) includes not only the human immunodeficiency virus (HIV) infection itself but also opportunistic infections and tumors secondary to AIDS. Despite progress in antiretroviral therapy and the subsequent decrease in the incidence of associated diseases, opportunistic infections and tumors secondary to the HIV infection continue to be the limiting factor in terms of survival with AIDS. Therefore, the therapeutic aim is permanent antiretroviral therapy as well as early diagnosis and treatment of opportunistic infections. Magnetic resonance imaging is often the diagnostic method of choice in suspected CNS pathology of HIV patients. In the following, the typical clinical and radiological features of several AIDS-related pathologies are presented and discussed.

Low rate of contrast-induced Nephropathy after CT perfusion and CT angiography in acute stroke patients.

BACKGROUND: The aim of the study was to assess (i) the rate of contrast-induced nephropathy (CIN), (ii) the amount and time course of renal dysfunction, (iii) the identification of risk factors and calculation of a risk score for CIN in acute stroke patients after CT perfusion (CTP) and CT angiography (CTA). METHODS: 162 patients were investigated,who had received 140 ml of non-ionic low osmolar contrast agent (300 mg iodine per ml, Ultravist 300, Schering AG) for CTA and CTP. We assessed electrolytes, creatinine, and creatinine clearance before and up to 7 days after administration of contrast agent. In addition, the risk factors for CIN were recorded and a previously validated risk score for CIN was calculated. We also assessed the amount of crystalloid fluid substitution and newly prescribed drugs. CIN was defined as an increase of the serum creatinine-level of > 0.5 mg/dl or > 25% above baseline within 48 hours after contrast agent administration. RESULTS: 154 patients (94 %) received crystalloid fluid substitution (mean 6.1 l) within 48 h after contrast agent administration. During follow-up the creatinine values and the creatinine clearance remained stable while sodium and potassium increased significantly (p < 0.0001) after contrast agent administration. In patients with a pathological creatinine value on admission (n = 40), the creatinine clearance did not decrease significantly (p = 0.18). The risk score for developing a CIN was low in the majority of stroke patients. A manifest CIN occurred in 3 patients (2 %). No patient had to be hemodialysed. CONCLUSION: CIN is a rare complication in acute stroke patients examined by multimodal contrast-based CT due to the low prevalence of risk factors associated with CIN. In conjunction with appropriate fluid substitution, low osmolar nonionic contrast agents seem to be safe in clinical routine.

[Chemoembolization of hepatocellular carcinomas: which factors determine therapeutic response and survival?]. / Chemoembolisation des hepatozellulären Karzinoms: Welche Faktoren bestimmen Therapieansprechen und Uberleben?

PURPOSE: To determine independent prognostic factors influencing the survival of patients with hepatocellular carcinoma (HCC) treated with transcatheter arterial chemoembolization (TACE). MATERIALS AND METHODS: Ninety-one patients with unresectable HCC were treated with 269 repetitive TACE. The dosages of epirubicin (40-60 mg) and ethiodized oil (8-20 ml) were adjusted to tumor size and liver function. The impact of tumor size, macroscopic tumor type, tumor location, portal vein infiltration, capsular infiltration, tumor vascularization, uptake of ethiodized oil within the tumors, Child-Pugh-Class and Okuda-Stage on patient survival were evaluated by means of univariate and multivariate regression analysis. RESULTS: The following independent prognostic factors were found: tumor type (nodular vs. infiltrating, p = 0 008), tumor size (p = 0.01), Child-Pugh-Class (A vs. B; p = 0.02) and grade of tumor vascularization (p = 0.04). In 57 patients with HCC of the nodular type, the median survival time was significant longer than in 32 patients with HCC of the infiltrating type (17.0 months vs. 7.9 months; p < 0.003; 2 tumors could not be classified). The 1-, 2- and 3-year-survival rates were significantly higher in 57 patients with Okuda-Stage I disease, compared to 34 patients with Okuda-Stage II and III disease (73%, 31% and 8% vs. 23%, 6% and 4% p < 0.0001). CONCLUSIONS: Tumor type, tumor size and grade of liver cirrhosis have an independent impact on prognosis of patients with HCC treated by TACE. An appropriate selection of patients is necessary to improve patients survival.