Cerebral blood flow and metabolism measurement using positron emission tomography before and during internal carotid artery test occlusions: feasibility of rapid quantitative measurement of CBF and OEF/CMRO(2)

Crossed cerebellar diaschisis-related supratentorial hemodynamic and metabolic status measured by PET/MR in assessing postoperative prognosis in chronic ischemic cerebrovascular disease patients with bypass surgery

Objective

Cerebral ischemic status is an indicator of bypass surgery. Both hemodynamics and glucose metabolism are significant factors for evaluating cerebral ischemic status. The occurrence of crossed cerebellar diaschisis (CCD) is influenced by the degree of supra-tentorial perfusion and glucose metabolism reduction. This study aimed to investigate the relationship between the CCD-related supra-tentorial blood flow and metabolic status before bypass surgery in patients with chronic and symptomatic ischemic cerebrovascular disease and the prognosis of surgery.

Methods

Twenty-four participants with chronic ischemic cerebrovascular disease who underwent hybrid positron emission tomography (PET)/magnetic resonance (MR) before bypass surgery were included. Arterial spin labeling (ASL)-MR and FDG-PET were used to measure blood flow and metabolism, respectively. The PET images were able to distinguish CCD. The supratentorial asymmetry index (AI) and volume in the decreased blood flow region, decreased metabolism region and co-decreased region on the affected side, except for the infarct area, were respectively obtained before bypass surgery. The neurological status was determined using the National Institutes of Health Stroke Scale (NIHSS) and modified Rankin Scale (mRS) scores. Differences between CCD-positive (CCD +) and CCD-negative (CCD−) groups were investigated.

Results

Fourteen (58%) of the 24 patients were diagnosed as CCD +. Before surgery, the NIHSS and mRS scores of the CCD + were significantly higher than those of the CCD− (1.0(1.0) vs. 0.0(1.0), P = 0.013; 1.0(1.5) vs. 0.0(1.5), P = 0.048). After the surgery, the NIHSS and mRS scores of the CCD + showed a significant decrease (0.0(1.0) to 0.0(0.0), P = 0.011; 0.0(0.5) to 0.0(0.0), P = 0.008). Significant differences were observed in the supra-tentorial decreased metabolism region (all Ps ≤ 0.05) between the CCD + and CCD− groups, but no differences were observed in the preprocedural decreased supratentorial blood flow region (P > 0.05). The preprocedural NIHSS score was strongly correlated with the metabolism AI value in the decreased metabolism region (r = 0.621, P = 0.001) and the co-decreased region (r = 0.571, P = 0.004).

Conclusions

Supratentorial blood flow and metabolism are important indicators of CCD. This study showed that CCD + patients benefited more from bypass surgery than CCD− patients. Staging based on CCD-related supra-tentorial blood flow and metabolic status by hybrid PET/MR may help to personalize treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12149-022-01766-0.

Carotid artery ultrasound image analysis: A review of the literature

Stroke is one of the prominent causes of death in the recent days. The existence of susceptible plaque in the carotid artery can be used in ascertaining the possibilities of cardiovascular diseases and long-term disabilities. The imaging modality used for early screening of the disease is B-mode ultrasound image of the person in the artery area. The objective of this article is to give a widespread review of the imaging modes and methods used for studying the carotid artery for identifying stroke, atherosclerosis and related cardiovascular diseases. We encompass the review in methods used for artery wall tracking, intima-media, and lumen segmentation which will help in finding the extent of the disease. Due to the characteristics of the imaging modality used, the images have speckle noise which worsens the image quality. Adaptive homomorphic filtering with wavelet and contourlet transforms, Levy Shrink, gamma distribution were used for image denoising. Learning-based neural network approaches for denoising give better edge preservation. Domain knowledge-based segmentation approaches have proved to provide more accurate intima-media thickness measurements. There is a requirement of useful fully automatic segmentation approaches, 3D, 4D systems, and plaque motion analysis. Taking into consideration the image priors like geometry, imaging physics, intensity and temporal data, image analysis has to be performed. Encouragingly more research has focused on content-specific segmentation and classification techniques. With the evaluation of machine learning algorithms, classifying the image as with or without a fat deposit has gained better accuracy and sensitivity. Machine learning-based approaches like self-organizing map, k-nearest neighborhood and support vector machine achieve promising accuracy and sensitivity in classification. The literature reveals that there is more scope in identifying a patient-specific model in a fully automatic manner.

Current understanding of chronic total occlusion of the internal carotid artery

At present, there is limited understanding of chronic total occlusion (CTO) of the internal carotid artery (ICA). Therefore, the present report collected related cases from PubMed and reviewed the literature. Cerebral vessels may form collateral circulation immediately or gradually following CTO of the ICA. The natural history of CTO of the ICA includes a variety of outcomes, all of which are biased toward a non-benign progressive process and are characterized by insufficient cerebral perfusion, embolus detachment and cognitive dysfunction. The majority of cases of CTO of the ICA require treatment. In early studies, the results of external-ICA bypass were unsatisfactory, while recanalization is now considered the only viable option. The current treatment indications mainly depend on the degree of injury to the cerebrovascular reserve and the extent to which the oxygen extraction fraction is increased. The length, height and duration of ICA occlusion are also relevant, though more frequently, the condition depends on multiple factors. Endovascular interventional recanalization, carotid endarterectomy (CEA) and hybrid surgery may be conducted in a select group of patients. As novel materials are developed, the success rate of simple recanalization may gradually increase; however, hybrid surgery may be more representative of the current trend, as advanced CEA can remove carotid atherosclerosis plaques, thus reducing the technological demands of the subsequent interventional recanalization. There are many complications that may result from recanalization following CTO of the ICA, including hyperperfusion and technical errors; therefore, the operation must be conducted carefully. If the recanalization is successful, it typically results in a stable improvement of patient condition in the long term. However, despite these conclusions, more studies are required in the future to further improve current understanding of CTO of the ICA.

Applicability of emission-based attenuation map for rapid CBF, OEF, and CMRO2 measurements using gaseous (15)O-labeled compounds

Background

Cerebral blood flow (CBF), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO₂) images have facilitated understanding of the pathophysiological basis of cerebrovascular disorders. Such parametric images can be rapidly, measured within around 15 min, using positron emission tomography (PET) with sequentially administered ¹⁵O-labeled oxygen and water. For further shortening, one option is to eliminate the transmission scan by applying an emission-based attenuation correction.

Methods

The validity of the present method was tested by comparing parametric values with emission-based attenuation correction to those with transmission-based correction. This was applied to 27 subjects who were diagnosed with or without cerebrovascular disorders. All subjects received the rapid CBF/OEF/CMRO₂ PET measurements. An emission-based attenuation map was generated by estimating the edge of the brain tissue contour on an obtained sinogram and by assuming the uniform tissue coefficient to be 0.1 cm⁻¹. Then images were reconstructed, and parametric images were computed.

Results

No difference was apparent between the emission- and transmission-based methods. Paired t-test showed no significant differences in CBF, OEF, or CMRO₂ values between the emission- and transmission-based methods, except in the parietal and occipital and cerebellum and occipital regions, and the differences were less than 10%. The regression analysis showed a close correlation of r = 0.89 to 0.99.

Conclusions

The present study revealed that the attenuation correction can be performed by the emission-based estimation method and clinical PET duration can be shortened for the CBF, OEF, and CMRO₂ gas study.

X-ray Angiography Perfusion Analysis for the Balloon Occlusion Test of the Internal Carotid Artery

BACKGROUND

A perfusion study should be performed during the balloon occlusion test (BOT) to prevent ischemic events after therapeutic carotid occlusion. We evaluated the efficacy of X-ray angiography perfusion analysis during the BOT.

METHODS

Twenty-one consecutive patients who underwent the BOT of the internal carotid artery were included. Patients who had a venous phase delay of less than .5 seconds and a mean stump pressure of more than 50 mm Hg without any neurologic symptoms were considered tolerant, and other patients were considered intolerant. A time-density curve was constructed for each hemisphere using X-ray angiography perfusion software (2D-Perfusion). The mean transit time and area under the curve, which correspond to cerebral blood volume, were calculated from the curve. Differences in these parameters between the occluded and nonoccluded hemispheres and the perfusion index were compared between the tolerant and intolerant groups.

RESULTS

In the intolerant group, the mean transit time was significantly longer (1.31 ± .72 seconds versus .44 ± .21 seconds, P = .001) and the perfusion index was significantly lower (.72 ± .16 versus .94 ± .08, P = .001) compared with those in the tolerant group. The area under the curve was not different between the groups.

CONCLUSIONS

Parameters obtained by X-ray angiography perfusion analysis were significantly different between the tolerant and intolerant groups. The X-ray angiography perfusion analysis could be a safe and effective method for assessing ischemic tolerance before therapeutic carotid occlusion.

Revascularization and Aneurysm Surgery

BACKGROUND:

Given advances in endovascular technique, the indications for revascularization in aneurysm surgery have declined.

OBJECTIVE:

We sought to define indications, outline technical strategies, and evaluate the outcomes of patients treated with bypass in the endovascular era.

METHODS:

We retrospectively reviewed all aneurysms treated between September 2006 and February 2013.

RESULTS:

We identified 54 consecutive patients (16 males and 39 females) with 56 aneurysms. Aneurysms were located along the cervical internal carotid artery (ICA) (n = 1), petrous/cavernous ICA (n = 1), cavernous ICA (n = 16), supraclinoid ICA (n = 7), posterior communicating artery (n = 2), anterior cerebral artery (n = 4), middle cerebral artery (MCA) (n = 13), posterior cerebral artery (PCA) (n = 3), posterior inferior cerebellar artery (n = 4), and vertebrobasilar arteries (n = 5). Revascularization was performed with superficial temporal artery (STA) to MCA bypass (n = 25), STA to superior cerebellar artery (SCA) (n = 3), STA to PCA (n = 1), STA-SCA/STA-PCA (n = 1), occipital artery (OA) to PCA (n = 2), external carotid artery/ICA to MCA (n = 15), OA to MCA (n = 1), OA to posterior inferior cerebellar artery (n = 1), and in situ bypasses (n = 8). At a mean clinical follow-up of 18.5 months, 45 patients (81.8%) had a good outcome (Glasgow Outcome Scale 4 or 5). There were 7 cases of mortality (12.7%) and an additional 9 cases of morbidity (15.8%). At a mean angiographic follow-up of 17.8 months, 14 bypasses were occluded. Excluding the 7 cases of mortality, the majority of aneurysms (n = 42) were obliterated. We identified 7 cases of residual aneurysm and recurrence in 6 patients at follow-up.

CONCLUSION:

Given current limitations with existing treatments, cerebral revascularization remains an essential technique for aneurysm surgery.