Using Flat-Panel Perfusion Imaging to Measure Cerebral Hemodynamics: A Pilot Feasibility Study in Patients With Carotid Stenosis

Clinical Applications of Conebeam CTP Imaging in Cerebral Disease: A Systematic Review

BACKGROUND

Perfusion imaging with multidetector CT is integral to the evaluation of patients presenting with ischemic stroke due to large-vessel occlusion. Using conebeam CT perfusion in a direct-to-angio approach could reduce workflow times and improve functional outcome.

PURPOSE

Our aim was to provide an overview of conebeam CT techniques for quantifying cerebral perfusion, their clinical applications, and validation.

DATA SOURCES

A systematic search was performed for articles published between January 2000 and October 2022 in which a conebeam CT imaging technique for quantifying cerebral perfusion in human subjects was compared against a reference technique.

STUDY SELECTION

Eleven articles were retrieved describing 2 techniques: dual-phase (n = 6) and multiphase (n = 5) conebeam CTP.

DATA ANALYSIS

Descriptions of the conebeam CT techniques and the correlations between them and the reference techniques were retrieved.

DATA SYNTHESIS

Appraisal of the quality and risk of bias of the included studies revealed little concern about bias and applicability. Good correlations were reported for dual-phase conebeam CTP; however, the comprehensiveness of its parameter is unclear. Multiphase conebeam CTP demonstrated the potential for clinical implementation due to its ability to produce conventional stroke protocols. However, it did not consistently correlate with the reference techniques.

LIMITATIONS

The heterogeneity within the available literature made it impossible to apply meta-analysis to the data.

CONCLUSIONS

The reviewed techniques show promise for clinical use. Beyond evaluating their diagnostic accuracy, future studies should address the practical challenges associated with implementing these techniques and the potential benefits for different ischemic diseases.

Choice of imaging to evaluate carotid stenosis and guide management

Carotid artery disease is a cause of ischemic stroke and is associated with cognitive decline. Besides the evaluation of the degree of stenosis, it is also crucial to assess the morphology of the atherosclerotic plaque, for a prompt and accurate diagnosis, and to make the best decision for the patient. On top of noninvasive duplex ultrasound (DUS) and invasive digital subtraction angiography (DSA), compute tomography angiography (CTA) and magnetic resonance angiography (MRA) are often used effectively as noninvasive imaging tools to study carotid stenoses. This review describes the fundamental characteristics of carotid artery plaques, and how they can be best evaluated with currently available imaging methods.

Postoperative neovascularization, cerebral hemodynamics, and clinical prognosis between combined and indirect bypass revascularization procedures in hemorrhagic moyamoya disease

OBJECTIVE

We evaluated what few studies emphasized the postoperative collateral formation and cerebral hemodynamics of hemorrhagic moyamoya disease (MMD).

METHODS

Hemorrhagic MMD patients treated surgically were retrospectively collected and dichotomized into combined bypass (CB) and indirect bypass (IB) groups. CB used superficial temporal artery-to-middle cerebral artery anastomosis combined with encephaloduroarteriomyosynangiosis (STA-MCA+EDAMS), and IB used encephaloduroarteriomyosynangiosis (EDAMS) for revascularization. Postoperative complications and clinical prognosis, as well as pre- and post-operative Modified Rankin Scale (mRS), collateral circulation status, and cerebral hemodynamics were observed and compared between the CB and IB groups.

RESULTS

A total of 37 patients with hemorrhagic MMD were identified. Of the 68 cerebral hemispheres, 47(69.1%) were combined revascularization, and the rest were indirect. During an average follow-up of 16.5 ± 8.7 months, the recurrent stroke events were significantly lower, as well as having a postoperative mRS scores≤ 2. A satisfactory postoperative collateral formation, and an improved dilation or extension of the anterior choroidal/posterior communication artery (AchA/PcoA) were significantly higher in the CB group than in the IB group (all P < .05). Compared with preoperative cerebral hemodynamics, relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), mean transit time (MTT), and relative time to peak (rTTP) in the CB group; rCBF, rCBV, and MTT in the IB group were significantly improved (all P < .001). The CB group's postoperative rCBF was significantly improved compared with the IB group (P < .001).

CONCLUSIONS

STA-MCA bypass combined with EDAMS can obtain better postoperative collateral formation, cerebral hemodynamics, and clinical prognosis than EDAMS alone.

Diagnostic accuracy of flat-panel computed tomography in assessing cerebral perfusion in comparison with perfusion computed tomography and perfusion magnetic resonance: a systematic review

Purpose

Flat-panel computed tomography (FP-CT) is increasingly available in angiographic rooms and hybrid OR’s. Considering its easy access, cerebral imaging using FP-CT is an appealing modality for intra-procedural applications. The purpose of this systematic review is to assess the diagnostic accuracy of FP-CT compared with perfusion computed tomography (CTP) and perfusion magnetic resonance (MRP) in cerebral perfusion imaging.

Methods

We performed a systematic literature search in the Cochrane Library, MEDLINE, Embase, and Web of Science up to June 2019 for studies directly comparing FP-CT with either CTP or MRP in vivo. Methodological quality was assessed using the QUADAS-2 tool. Data on diagnostic accuracy was extracted and pooled if possible.

Results

We found 11 studies comparing FP-CT with CTP and 5 studies comparing FP-CT with MRP. Most articles were pilot or feasibility studies, focusing on scanning and contrast protocols. All patients studied showed signs of cerebrovascular disease. Half of the studies were animal trials. Quality assessment showed unclear to high risks of bias and low concerns regarding applicability. Five studies reported on diagnostic accuracy; FP-CT shows good sensitivity (range 0.84–1.00) and moderate specificity (range 0.63–0.88) in detecting cerebral blood volume (CBV) lesions.

Conclusions

Even though FP-CT provides similar CBV values and reconstructed blood volume maps as CTP in cerebrovascular disease, additional studies are required in order to reliably compare its diagnostic accuracy with cerebral perfusion imaging.

Electronic supplementary material

The online version of this article (10.1007/s00234-019-02285-y) contains supplementary material, which is available to authorized users.

X-ray angiography perfusion imaging with an intra-arterial injection: comparative study with 15O-gas/water positron emission tomography

Background

X-ray angiography perfusion (XAP) is a perfusion imaging technique based on conventional DSA.

Objective

In this study, we aimed to validate parameters derived from XAP by comparing them with 15O-gas/water positron emission tomography (PET), using data from patients with chronic ischemic cerebrovascular disease.

Methods

18 consecutive patients were included. XAP was performed with intra-arterial infusion of contrast media, and a time–density curve was constructed for each cerebral hemisphere. From the curves, the relative values of mean transit time (rMTT) and wash-in rate (rWiR) were obtained by dividing the values of the right hemisphere by those of the left hemisphere. These were then compared with the relative values of cerebral blood flow (rCBF) and rMTT calculated from the PET data.

Results

XAP rWiR correlated strongly with PET rCBF (r=0.86, P<0.0001). rMTT measurements from the two modalities were also strongly correlated (r=0.85, P<0.0001). Bland–Altman analysis revealed a bias of 0.14±0.18 (95% limits of agreement −0.22 to 0.51) for PET rCBF versus XAP rWiR, and 0.016±0.093 (95% limits of agreement −0.17 to 0.20) for rMTT between the two modalities.

Conclusions

The relative values obtained from XAP were validated across a population of patients with chronic ischemic cerebrovascular disease.

Automatic flow analysis of digital subtraction angiography using independent component analysis in patients with carotid stenosis

PURPOSE

Current time-density curve analysis of digital subtraction angiography (DSA) provides intravascular flow information but requires manual vasculature selection. We developed an angiographic marker that represents cerebral perfusion by using automatic independent component analysis.

MATERIALS AND METHODS

We retrospectively analyzed the data of 44 patients with unilateral carotid stenosis higher than 70% according to North American Symptomatic Carotid Endarterectomy Trial criteria. For all patients, magnetic resonance perfusion (MRP) was performed one day before DSA. Fixed contrast injection protocols and DSA acquisition parameters were used before stenting. The cerebral circulation time (CCT) was defined as the difference in the time to peak between the parietal vein and cavernous internal carotid artery in a lateral angiogram. Both anterior-posterior and lateral DSA views were processed using independent component analysis, and the capillary angiogram was extracted automatically. The full width at half maximum of the time-density curve in the capillary phase in the anterior-posterior and lateral DSA views was defined as the angiographic mean transient time (aMTT; i.e., aMTTAP and aMTTLat). The correlations between the degree of stenosis, CCT, aMTTAP and aMTTLat, and MRP parameters were evaluated.

RESULTS

The degree of stenosis showed no correlation with CCT, aMTTAP, aMTTLat, or any MRP parameter. CCT showed a strong correlation with aMTTAP (r = 0.67) and aMTTLat (r = 0.72). Among the MRP parameters, CCT showed only a moderate correlation with MTT (r = 0.67) and Tmax (r = 0.40). aMTTAP showed a moderate correlation with Tmax (r = 0.42) and a strong correlation with MTT (r = 0.77). aMTTLat also showed similar correlations with Tmax (r = 0.59) and MTT (r = 0.73).

CONCLUSION

Apart from vascular anatomy, aMTT estimates brain parenchyma hemodynamics from DSA and is concordant with MRP. This process is completely automatic and provides immediate measurement of quantitative peritherapeutic brain parenchyma changes during stenting.