| Part One Image quality,radiation dose and diagnostic accuracy of 70 kVp whole brain volumetric CT perfusion imaging:a preliminary studyPurpose:To evaluate image quality and diagnostic accuracy for acute infarct detection and radiation dose of 70 kVp whole brain CT perfusion(CTP)and CT angiography(CTA)reconstructed from CTP source dataMethods:Patients were divided into three Groups(n=50 each):Group A,80 kVp,21 scanning time points;Groups B,70 kVp,21 scanning time points;Group C,70 kVp,17 scanning time points.Objective and subjective image quality of CTP and CTA were compared.Diagnostic accuracy for detecting acute infarct and cerebral artery stenosis>50%was calculated for CTP and CTA with diffusion weighted imaging and digital subtraction angiography as reference standards.Effective radiation dose was compared.Results:The perfusion parameters of cerebral blood flow(CBF)in group A was 66.6±7.1 29.0±3.8 and 29.6±3.9 ml/(100ml.min),cerebral blood volume(CBV)was 4.0±0.5 1.8±0.3 and 1.9±0.3 ml/100ml,mean traismit time was 3.5±0.5 4.6±0.8 and 4.9±1.2 s.The perfusion parameters of cerebral blood flow(CBF)in group B was 67.4±8.2 30.3±4.1 and 29.8±3.3ml/(100ml.min),cerebral blood volume(CBV)was 4.1±0.4 1.9±0.2 and 1.9±0.2 ml/100ml,mean traismit time was 3.7±0.6 4.7±1.0 and 5.4±1.3 s.The perfusion parameters of cerebral blood flow(CBF)in group C was 67.6±7.8 30.2±4.4 and 29.7±4.1 ml/(100ml.min),cerebral blood volume(CBV)was 4.0±0.5 1.9±0.3 and 1.9 ±0.3 ml/100ml,mean traismit time was 3.6±0.7 4.7±1.0 and 5.3±1.1 s.There were no differences in any perfusion parameter value between three Groups(P>0.05).No difference was found in subjective image quality of CTP between three Groups(P>0.05).Diagnostic accuracy for detecting acute infarct and vascular stenosis showed no difference between three Groups(P>0.05).Except for the different of gray and white matter in CBF and CBV,No difference was found in subjective image quality of CTA between three Groups(P>0.05)Compared with Group A,radiation doses of Groups B and C were decreased by 28%and 37%(both P<0.001),respectively.Conclusion:Compared with 80 kVp protocol,70 kVp brain CTP allows comparable vascular and perfusion assessment and lower radiation dose while maintaining high diagnostic accuracy in detecting acute infarct.Part Two Time-shift functional connectivity MRI on acute ischemic brain strokePurpose:To evaluate feasibility of time-shifting functional connectivity(TSFC)maps(obtained using two different approaches)for mapping acute ischemic stroke,as well to evaluate the ability for TSFC maps to detect infarct core from penumbra.Methods:Thirteen patients were scanned at 3 Tesla using a gradient-echo echo planar imaging sequence for TSFC imaging.Cross correlation analysis was performed between TSFC maps(reference signal comprised of either the superior sagittal sinus(SSS)or whole brain(WB)average time course)and dynamic susceptibility contrast Tmax maps.Mean time course devided from TSFC maps,both in infarct core and penumbra were computed.Results:Good agreement were found in the perfusion deficit between time-shift functional connectivity maps maps and Tmax maps using the SSS as reference or WB.The mean time course of TSFC maps using the SSS and WB as seed in infarct core was found delayed than in penumbra.Conclusion:These preliminary results suggested that resting-state fMRI,both with SSS as seed,had the ablilty to detect perfusion deficts.This noninvasive neuroimaging approach coule be used to detect the infarct core from penumbra in stroke furthermore. |
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