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Objective: This study aimed to determine a contrast medium injection rate that ensures both accuracy for data and safety for operation by comparing hemodynamic parameters of brain CT perfusion imaging with varied injection rates., Methods: Twenty-four healthy volunteers were divided into three groups based on contrast medium injection rates (4.5, 6.0, and 7.5 ml/s). For all subjects, CT perfusion scanning was started at 4 s after antecubital venous bolus of contrast media injection. A perfusion-analyzing software package was used to produce a time-density curve in the anterior cerebral artery and the superior sagittal sinus and calculate the regional cerebral blood flow (rCBF) in the gray matter and the white matter. The hemodynamic indices were compared among the three groups, and statistical analysis was carried out using the F test., Results: The time for the arterial rise to reach the peak value for the 7.5-ml/s group was only 0.2 s ahead of the initiation time for the rise of the superior sagittal sinus. The differences of rCBF in the gray matter and the white matter among the three groups were statistically significant. rCBF in the gray matter and the white matter for the 7.5-ml/s group was 52.8 ml x min(-1) 100 g(-1) . (+/-3.1) and 21.9 ml x min(-1) . 100 g(-1) (+/-2.4), respectively., Conclusions: The use of the 7.5-ml/s injection rate can meet the prerequisite of the maximum slope model, and the resulting rCBF can be very close to that measured by positron emission tomography. Therefore, 7.5 ml/s was an ideal contrast medium injection rate.

Abstract: Objective: To explore the mismatched manifestation between regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) of astrocytomas. Methods: Both conventional and perfusion CT were performed on 29 patients with pathologically confirmed astrocytomas (15 cases in Grades I–II, 14 cases in Grades III–IV). Time-density curves were plotted, cerebral blood flow and volume maps were generated, and the values between rCBF and rCBV in the same region of interest (ROI) were compared. Results: Twelve low-grade astrocytomas showed low or medium values of both rCBF (46.95±22.92 ml ⋅ 100 g−1 ⋅ mm−1) and rCBV (5.74±3.61 ml ⋅ 100 g−1); 12 high-grade astrocytomas showed high values of both rCBF (95.44±42.58 ml ⋅ 100 g−1 ⋅ min−1) and rCBV (9.24±5.32 ml ⋅ 100g−1). These cases exhibited agreement between the values of rCBF and rCBV. However, the remaining five astrocytomas were mismatched, showing reduced rCBF value and increased rCBV value in the same ROI. The discrepancy may mislead to an inaccuracy of perfusion CT in grading gliomas. Conclusions: The mismatched manifestation between rCBF and rCBV occasionally exists in some areas of astrocytomas. Hence, attention should be paid to assessments in preoperative grading of astrocytomas and in monitoring therapeutic effects. [Copyright &y& Elsevier]

An electromagnetic actuator was designed for magnetic resonance elastography (MRE). The actuator is unique in that it is simple, portable, and capable of brain, abdomen, and phantom imagings. A custom-built control unit was used for controlling the vibration frequency and synchronizing the trigger signals. An actuation unit was built and mounted on the specifically designed clamp and holders for different imaging applications. MRE experiments with respect to gel phantoms, brain, and liver showed that the actuator could produce stable and consistent mechanical waves. Estimated shear modulus using local frequency estimate method demonstrated that the measurement results were in line with that from MRE studies using different actuation systems. The relatively easy setup procedure and simple design indicated that the actuator system had the potential to be applied in many different clinical studies. [ABSTRACT FROM AUTHOR]