**2. Computed tomography perfusion**

CT perfusion is a new technique which enables to evaluate both rapid qualitative and quan‐ titative cerebral perfusion by means of generating cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) [4]. Thus far, several modalities such as magnetic resonance (MR) perfusion [5], xenon computed tomography (xenon CT) [6], positron emission tomography (PET) [7], and single photon emission computed tomography (SPECT) [8] have been used to evaluate cerebral perfusion. Compared to these modalities, CT perfusion can be performed easily and quickly by the use of any standard spiral CT scanner in patients where unenhanced CT is planned to exclude acute intracranial hemorrhage. The fundamental theory of this technique is the central volume principle [4]. It correlates cerebral blood flow (CBF) with cerebral blood volume (CBV) and mean transit time (MTT) in the following equation: CBF = CBV/MTT. In brief, by monitoring the first pass of an iodinated contrast agent by the bolus injection through the cerebral vasculature, the linear relationship between contrast agent concentration and attenuation can be obtained in a given region of interest. After an acquisition of the raw results, data are analyzed at an imaging workstation (Advantage Windows; GE Medical Systems) equipped with commercially available software (CT perfusion; GE Medical Systems). By the use of CT perfusion, it becomes easy and quick to identify and quantify the presence and extent of a perfusion deficit in an acute stroke setting in whom an emergent thrombolytic therapy is going to be considered [9]. In addition, it is also suitable for the evaluation of cerebrovascular reserve in patients with stenotic lesions who would be the potential candidates for neuroendovascular treatment and bypass surgery.

an overall frequency of 2.8%, and an incidence rate of 0.9% in patients younger than 65 years, 3.6% aged between 65 and 74 years, and 8.9% older than 75 years [2]. Additionally, the patient with a neurological complication has a ninefold increase in mortality [2]. Carotid arterial disease accounts for approximately 10% of perioperative cerebral complications [3]. Although ultrasound imaging is an excellent modality for evaluating the morphology of the carotid arteries with its excellent spatial resolution [3], intracranial cerebral blood flow dynamics cannot be assessed by the use of ultrasound. Here, we report that computed tomography perfusion (CTP) imaging is an efficacious modality for evaluating the intracranial cerebral

In our facility, CTP imaging has been introduced in 2012, and 58 cases underwent its evaluation by the end of 2014. After obtaining an IRB (Institutional Review Board) approval, we have analyzed all the 58 cases, and identified 11 individuals who have been diagnosed as having carotid arterial stenosis/occlusion. We have measured cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) at the ipsilateral as well as at the contrala‐ teral hemisphere, and their correlation to the subsequent development of neurological events

Of 11 patients, the decreased CBF at the ipsilateral hemisphere was noted in four individuals, and the other seven showed intact CTP findings. All the four patients who showed decreased CBF pattern and the one who showed normal CTP finding developed cerebrovascular diseases during the 2‐year follow‐up period. The rest of six individuals who showed normal CTP findings have remained otherwise healthy. We suggest that the decreased CBF at the ipsilateral side may predict the possible neurological complications in the patients with carotid arterial stenosis/occlusion. In patients with carotid arterial stenosis whose cerebral blood flow (CBF) has remained intact, the patients' outcome has remained favorable, and they have remained otherwise healthy. By contrast, in patients whose CBF is decreased, they have developed severe cerebrovascular complications. The findings described here potentially indicate the possibility that CT perfusion findings may predict the perioperative outcomes in patients with carotid

CT perfusion is a new technique which enables to evaluate both rapid qualitative and quan‐ titative cerebral perfusion by means of generating cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) [4]. Thus far, several modalities such as magnetic resonance (MR) perfusion [5], xenon computed tomography (xenon CT) [6], positron emission tomography (PET) [7], and single photon emission computed tomography (SPECT) [8] have been used to evaluate cerebral perfusion. Compared to these modalities, CT perfusion can be performed easily and quickly by the use of any standard spiral CT scanner in patients where unenhanced CT is planned to exclude acute intracranial hemorrhage. The fundamental theory of this technique is the central volume principle [4]. It correlates cerebral blood flow (CBF) with cerebral blood volume (CBV) and mean transit time (MTT) in the following equation: CBF =

during the 2‐year follow‐up period was evaluated.

arterial stenosis/occlusion.

**2. Computed tomography perfusion**

flow.

120 Current Topics in Anesthesiology

Although other multi‐modalities such as SPECT/CT and PET/CT system also provide good comprehensive information with respect to the combination of anatomical and functional data, they usually require the specific equipment which sometimes makes it difficult to their global diffusion into the clinical practice [7, 8]. For instance, for SPECT/CT, a dual‐detector gamma camera and a low‐dose four‐slice CT mounted on the same rotate platform are required (Infinia Hawkeye 4, GE Medical Systems). By contrast, CT perfusion can be performed easily and quickly using a standard spiral CT scanner and does not require specific equipment except for an imaging workstation, which makes it suitable for the global use in the evaluation of cerebral blood flow.
