Multi-delay arterial spin labeling perfusion MRI in moyamoya disease–comparison with CT perfusion imaging

Objectives

To present a multi-delay pseudo-continuous ASL (pCASL) protocol that offers simultaneous measurements of cerebral blood flow (CBF) and arterial transit time (ATT), and to study correlations between multi-delay pCASL and CT perfusion in moyamoya disease.

Methods

A 4 post-labeling delay (PLD) pCASL protocol was applied on 17 patients with moyamoya disease who also underwent CT perfusion imaging. ATT was estimated using the multi-delay protocol and included in the calculation of CBF. ASL and CT perfusion images were rated for lesion severity/conspicuity. Pearson correlation coefficients were calculated across voxels between the two modalities in grey and white matter of each subject respectively and between normalized mean values of ASL and CT perfusion measures in major vascular territories.

Results

Significant associations between ASL and CT perfusion were detected using subjective ratings, voxel-wise analysis in grey and white matter and region of interest (ROI)-based analysis of normalized mean perfusion. The correlation between ASL CBF and CT perfusion was improved using the multi-delay pCASL protocol compared to CBF acquired at a single PLD of 2 s (P?<?0.05).

Conclusions

There is a correlation between perfusion data from ASL and CT perfusion imaging in patients with moyamoya disease. Multi-delay ASL can improve CBF quantification, which could be a prognostic imaging biomarker in patients with moyamoya disease.

Key Points

? Simultaneous measurements of CBF and ATT can be achieved using multi-delay pCASL. ? Multi-delay ASL was compared with CT perfusion in patients with moyamoya disease. ? Statistical analyses showed significant associations between multi-delay ASL and CT perfusion. ? Multi-delay ASL can improve CBF quantification in moyamoya disease.     

Arterial spin labelling MRI for assessment of cerebral perfusion in children with moyamoya disease: comparison with dynamic susceptibility contrast MRI

Introduction

This study seeks to evaluate the diagnostic accuracy of cerebral perfusion imaging with arterial spin labelling (ASL) MR imaging in children with moyamoya disease compared to dynamic susceptibility contrast (DSC) imaging.

Methods

Ten children (7 females; age, 9.2?±?5.4 years) with moyamoya disease underwent cerebral perfusion imaging with ASL and DSC on a 3-T MRI scanner in the same session. Cerebral perfusion images were acquired with ASL (pulsed continuous 3D ASL sequence, 32 axial slices, TR?=?5.5 s, TE?=?25 ms, FOV?=?24 cm, matrix?=?128?×?128) and DSC (gradient echo EPI sequence, 35 volumes of 28 axial slices, TR?=?2,000 ms, TE?=?36 ms, FOV?=?24 cm, matrix?=?96?×?96, 0.2 ml/kg Gd-DOTA). Cerebral blood flow maps were generated. ASL and DSC images were qualitatively assessed regarding perfusion of left and right ACA, MCA, and PCA territories by two independent readers using a 3-point-Likert scale and quantitative relative cerebral blood flow (rCBF) was calculated. Correlation between ASL and DSC for qualitative and quantitative assessment and the accuracy of ASL for the detection of reduced perfusion per territory with DSC serving as the standard of reference were calculated.

Results

With a good interreader agreement (κ?=?0.62) qualitative perfusion assessment with ASL and DSC showed a strong and significant correlation (ρ?=?0.77; p?<?0.001), as did quantitative rCBF (r?=?0.79; p?<?0.001). ASL showed a sensitivity, specificity and accuracy of 94 %, 93 %, and 93 % for the detection of reduced perfusion per territory.

Conclusion

In children with moyamoya disease, unenhanced ASL enables the detection of reduced perfusion per vascular territory with a good accuracy compared to contrast-enhanced DSC.     

Changes in cerebral hemodynamics after carotid stenting of symptomatic carotid artery

Purpose

To evaluate changes in cerebral hemodynamics after carotid stenting of symptomatic carotid artery in the patients who underwent ischemic stroke caused by carotid artery stenosis.

Methods

Twenty patients with unilateral symptomatic carotid artery stenosis received brain computer tomography perfusion (CTP) scan a week before and a week after carotid artery stenting. Three absolute values including mean transit time (MTT), cerebral blood volume (CBV), and cerebral blood flow (CBF) were acquired and analyzed by use of the post-processing software. Six vascular territories such as ACA territory, MCA territory, PCA territory, basal ganglia, watershed between ACA and MCA territory (frontal watershed), watershed between MCA and PCA territory (posterior watershed) were chosen for comparison. Relative parameter values were defined as rCBF (relative CBF), rCBV (relative CBV), rMTT (relative MTT) through comparing absolute values in symptomatic hemispheres to absolute values in asymptomatic hemispheres. The relative perfusion parameter values before treatment were compared with post-treatment values. These analyses were performed by using the paired t test.

Results

The mean rMTT decreased significantly in ACA territory, MCA territory and two watershed after treatment, while the mean rCBF increased significantly in those areas after treatment. But the mean rCBV had no significant changes in all six vascular territories. In PCA territory, all the parameters had no significant changes.

Conclusion

Carotid artery stenting yields satisfactory cerebral perfusion in ACA territory, MCA territory, basal ganglia and two watersheds.     

The effects of propofol on cerebral perfusion MRI in children

Introduction

The effects of anesthesia are infrequently considered when interpreting pediatric perfusion magnetic resonance imaging (MRI). The objectives of this study were to test for measurable differences in MR measures of cerebral blood flow (CBF) and cerebral blood volume (CBV) between non-sedated and propofol-sedated children, and to identify influential factors.

Methods

Supratentorial cortical CBF and CBV measured by dynamic susceptibility contrast perfusion MRI in 37 children (1.8–18 years) treated for infratentorial brain tumors receiving propofol (IV, n?=?19) or no sedation (NS, n?=?18) were compared between groups and correlated with age, hematocrit (Hct), end-tidal CO₂ (ETCO₂), dose, weight, and history of radiation therapy (RT). The model most predictive of CBF and CBV was identified by multiple linear regression.

Results

Anterior cerebral artery (ACA) and middle cerebral artery (MCA) territory CBF were significantly lower, and MCA territory CBV greater (p?=?0.03), in IV than NS patients (p?=?0.01, 0.04). The usual trend of decreasing CBF with age was reversed with propofol in ACA and MCA territories (r?=?0.53, r?=?0.47; p?<?0.05). ACA and MCA CBF (r?=?0.59, 0.49; p?<?0.05) and CBV in ACA, MCA, and posterior cerebral artery territories (r?=?0.73, 0.80, 0.52; p?<?0.05) increased with weight in propofol-sedated children, with no significant additional influence from age, ETCO₂, hematocrit, or RT.

Conclusion

In propofol-sedated children, usual age-related decreases in CBF were reversed, and increases in CBF and CBV were weight-dependent, not previously described. Weight-dependent increases in propofol clearance may diminish suppression of CBF and CBV. Prospective study is required to establish anesthetic-specific models of CBF and CBV in children.     

Optimisation of vascular input and output functions in CT-perfusion imaging using 256(or more)-slice multidetector CT

Objectives

To evaluate the accuracy and reproducibility of CT-perfusion (CTP) by finding the optimal artery for the arterial input function (AIF) and re-evaluating the necessity of the venous output function (VOF).

Methods

Forty-four acute ischaemic stroke patients who underwent non-enhanced CT, CTP and CT-angiography using 256-slice multidetector computed tomography (MDCT) were evaluated. The anterior cerebral artery (ACA), middle cerebral artery (MCA), internal carotid artery (ICA) and basilar artery were selected as the AIF. Subsequently the resulting area under the time–enhancement curve of the AIF (AUC_AIF) and quantitative perfusion measurements were analysed by repeated measures ANOVA and subsequently the paired t test. To evaluate reproducibility we examined if the VOF could be deleted by comparing the perfusion measurements using versus not using the VOF (paired t test).

Results

The AUC_AIF and perfusion measurements resulting from the different AIFs showed significant group differences (all P?<?0.0001). The ICA had the largest AUC_AIF and resulted in the highest mean transient time (MTT) and lowest cerebral blood flow (CBF), whereas the basilar artery showed the lowest cerebral blood volume (CBV). Not using the VOF showed significantly higher CBV and CBF in 66 % of patients on the ipsilateral (P?<?0.0001 and P?=?0.007, respectively) and contralateral hemisphere (P?<?0.0001 and P?=?0.019, respectively).

Conclusion

Selecting the ICA as the AIF and continuing the use of the VOF would improve the accuracy of CTP.

Key Points

? Perfusion imaging is an increasingly important aspect of multidetector computed tomography (MDCT). ? Vascular input functions were evaluated for CT-perfusion using 256-slice MDCT. ? Selecting different arterial input functions (AIFs) leads to variation in quantitative values. ? Using the internal carotid artery for AIF provides optimal perfusion values. ? Deleting the venous output function would be detrimental for validity.     

Fluid-attenuated inversion recovery vascular hyperintensities in predicting cerebral hyperperfusion after intracranial arterial stenting

Purpose

No reliable imaging sign predicting cerebral hyperperfusion after intracranial arterial stenting (IAS) had been described in the literature. This study evaluated the effect of fluid-attenuated inversion recovery vascular hyperintensities (FVHs), also called hyperintense vessel sign on T2-weighted fluid-attenuated inversion recovery (T2-FLAIR) MR images, in predicting significant increase in cerebral blood flow (CBF) defined by arterial spin labeling (ASL) after IAS.

Methods

We reviewed ASL CBF images and T2-FLAIR MR images before (D0), 1 day after (D1), and 3 days after (D3) IAS of 16 patients. T1-weighted MR images were used as cerebral maps for calculating CBF. The changes in CBF values after IAS were calculated in and compared among stenting and nonstenting vascular territories. An increase more than 50% of CBF was considered as hyperperfusion. The effect of FVHs in predicting hyperperfusion was calculated.

Results

The D1 CBF value was significantly higher than the D0 CBF value in stenting vascular, contralateral anterior cerebral artery, contralateral middle cerebral artery, and contralateral posterior cerebral artery (PCA) territories (all P < .05). The D1 and D3 CBF values were significantly higher than the D0 CBF value in overall vascular (P < .001), overall nonstenting vascular (P < .001), and ipsilateral PCA (P < .05) territories. The rate of more than 50% increases in CBF was significantly higher in patients who exhibited asymmetric FVHs than in those who did not exhibit these findings.

Conclusion

FVHs could be a critical predictor of a significant increase in CBF after IAS.

     

Detection of symptomatic vasospasm after subarachnoid haemorrhage: initial findings from single time-point and serial measurements with arterial spin labelling

Objectives

To detect symptomatic hemispheres during the postoperative course of subarachnoid haemorrhage (SAH) using arterial spin labelling (ASL).

Methods

Eighteen patients with aneurysmal SAH were included; four exhibited symptomatic vasospasm postoperatively. All patients underwent ASL on days 9–10 (single time-point ASL). Nine patients underwent serial measurements of ASL (serial ASL) on days 1–2, 9–10 and 13–21, and seven patients also underwent imaging on days 4–7. CBF in the posterior part of the MCA territory was measured, and the ipsilateral/contralateral ratio of CBF was calculated. Differences between symptomatic hemispheres and others underwent ROC analysis.

Results

Single time-point ASL revealed that CBF_day9-10 and CBF_{i/c_day9-10} were significantly lower in symptomatic hemispheres than in asymptomatic hemispheres (P?<?0.001). Serial ASL was significantly decreased on CBF_day4-7 compared with CBF_day1-2 and on CBF_day9-10 compared with CBF_day4-7, and significantly increased on CBF_day13-21 compared with CBF_day9-10. ROC analysis of single time-point ASL revealed that AUC for CBF_day9-10 was 0.95, significantly higher than CBF_{i/c_day9-10} (P?<?0.001). ROC analysis of serial ASL showed that AUC for CBF_day9-10 was 0.93 and significantly higher than CBF_{day9-10/day1-2} and CBF_{i/c_day9-10} (P?<?0.001).

Conclusions

Single time-point ASL revealed significant CBF reduction in symptomatic hemispheres compared with asymptomatic hemispheres. Serial ASL showed time-dependent CBF changes after SAH.

Key Points

? MR arterial spin labelling (ASL) can non-invasively assess cerebral blood flow (CBF) ? ASL revealed significant CBF reduction in symptomatic hemispheres compared with asymptomatic hemispheres ? Serial ASL measurements enable observation of time-dependent CBF changes after SAH ? ASL is non- invasive and suitable for serial repeated examinations     

Influence of carotid artery stenting on cognitive function

Introduction

There have only been a few studies on cognitive changes in patients with carotid occlusive disease, and the results of these show major discrepancies in the extent to which treatment affects neuropsychological function. We sought to clarify these discrepancies by evaluating the effects of carotid artery stenting (CAS) on the cognitive function.

Methods

Forty-one asymptomatic CAS patients were administered a test battery of neuropsychological tests measuring cognitive speed and memory function before and 3 months after the procedure. A control group was also evaluated. To test for thromboembolic lesions, diffusion-weighted imaging was used.

Results

CAS led to a significant increase in cognitive speed (p?<?0.001) but did not afford any change in memory function. This was regardless of the degree or side of stenosis or patient age or gender.

Conclusion

CAS significantly improved functions that involve cognitive speed. Earlier studies did not differentiate between speed and memory tests and thus might have missed these changes. Further studies correlating changes in brain perfusion with increase in cognitive speed are needed.     

Differentiation of malignant and benign pulmonary nodules with first-pass dual-input perfusion CT

Objective

To assess diagnostic performance of dual-input CT perfusion for distinguishing malignant from benign solitary pulmonary nodules (SPNs).

Methods

Fifty-six consecutive subjects with SPNs underwent contrast-enhanced 320-row multidetector dynamic volume CT. The dual-input maximum slope CT perfusion analysis was employed to calculate the pulmonary flow (PF), bronchial flow (BF), and perfusion index $ \left( {\mathrm{PI},={{\mathrm{PF}} \left/ {{\left( {\mathrm{PF} + \mathrm{BF}} \right)}} \right.}} \right) $ . Differences in perfusion parameters between malignant and benign tumours were assessed with histopathological diagnosis as the gold standard. Diagnostic value of the perfusion parameters was calculated using the receiver-operating characteristic (ROC) curve analysis.

Results

Amongst 56 SPNs, statistically significant differences in all three perfusion parameters were revealed between malignant and benign tumours. The PI demonstrated the biggest difference between malignancy and benignancy: 0.30?±?0.07 vs. 0.51?±?0.13 , P?<?0.001. The area under the PI ROC curve was 0.92, the largest of the three perfusion parameters, producing a sensitivity of 0.95, specificity of 0.83, positive likelihood ratio (+LR) of 5.59, and negative likelihood ratio (?LR) of 0.06 in identifying malignancy.

Conclusions

The PI derived from the dual-input maximum slope CT perfusion analysis is a valuable biomarker for identifying malignancy in SPNs. PI may be potentially useful for lung cancer treatment planning and forecasting the therapeutic effect of radiotherapy treatment.

Key Points

? Modern CT equipment offers assessment of vascular parameters of solitary pulmonary nodules (SPNs) ? Dual vascular supply was investigated to differentiate malignant from benign SPNs. ? Different dual vascular supply patterns were found in malignant and benign SPNs. ? The perfusion index is a useful biomarker for differentiate malignancy from benignancy.     

Improvement of image quality and radiation dose of CT perfusion of the brain by means of low-tube voltage (70 KV)

Objectives

To investigate the feasibility of 70 kV cerebral CT perfusion by comparing image quality and radiation exposure to 80 kV.

Methods

Thirty patients with suspected cerebral ischemia who underwent dual-source CT perfusion were divided into group A (80 kV, 150 mAs) and group B (70 kV, 150 mAs). Quantitative comparisons were used for maximum enhancement, signal-to-noise index (SNI), and values of cerebral blood flow (CBF), cerebral blood flow (CBV), mean transit time (MTT) on CBF, CBV, and MTT images, and radiation dose from these two groups. Qualitative perfusion images were assessed by two readers.

Results

Maximum enhancement for group B was higher than group A (P?<?0.05). There were no significant differences between the two groups for SNI on CBF and CBV maps (P?=?0.06 – 0.576), but significant differences for MTT when SNI was measured on frontal white matter and temporo-occipital white matter (P?<?0.05). There were no differences among values of CBF, CBV, and MTT for both groups (P?=?0.251–0.917). Mean image quality score in group B was higher than group A for CBF (P?<?0.05), but no differences for CBV (P?=?0.542) and MTT (P?=?0.962). Radiation dose for group B decreased compared with group A.

Conclusions

70 kV cerebral CT perfusion reduces radiation dose without compromising image quality.

Key Points

? Radiation dose is a key concern with the increased using cerebral CT perfusion. Cerebral CT perfusion of 70 kV reduces radiation dose without compromising image quality. ? A 70-kV protocol could be used for cerebral CT perfusion.     

Calcium at the carotid siphon as an indicator of internal carotid artery stenosis

Objectives

Carotid siphon calcification is often visible on unenhanced head CT (UCT), but the relation to proximal carotid artery stenosis (CAS) is unclear. We investigated the association of carotid siphon calcification with the presence of CAS.

Methods

This IRB-waived retrospective study included 160 consecutive patients suspected of stroke (age 64?±?14 years, 63 female) who underwent head UCT and CTA of the head and neck. CAS was rated on CTA as not present or present with non-significant (<50 %), moderate (50–69 %) or significant (≥70 %) stenosis. Presence, shape (on UCT) and volume (on CTA) of carotid siphon calcifications were related to CAS.

Results

Carotid siphon calcification was absent in 41 % of patients and bilateral in 94 % of those with calcifications. Presence, shape and volume of calcification resulted in odds ratios for having significant CAS of 10.1, 3.9 and 8.4, with 95 % CIs of 1.3–79.6, 1.1–14.1 and 2.6–26.8, respectively. Corresponding NPVs were 0.98, 0.98 and 0.96, while PPVs were 0.14, 0.07 and 0.29, respectively.

Conclusion

Absence of calcification in the carotid artery siphon on UCT has high negative predictive value for carotid artery stenosis in patients with suspected stroke. However, siphon calcification is not a reliable indicator of significant carotid artery stenosis.

Key Points

? Many stroke patients do not have calcification in the carotid artery siphon. ? Carotid stenosis ≥50?% is unlikely in stroke patients without siphon calcification. ? Carotid siphon calcium is a poor indicator of significant carotid artery stenosis.     

Real-time ultrasound elastography: an assessment of enlarged cervical lymph nodes

Objectives

To determine the efficacy of real-time elastography (RTE), compared with our previously proposed prediction model, in the detection of malignancy in cervical lymph nodes (LNs).

Methods

One hundred and thirty-one patients underwent ultrasound-guided fine needle aspiration biopsy (ultrasound FNAB) after ultrasound and RTE evaluation. The formula of the RTE scoring system was a four-point visual scale, based on a previously determined model. The formula of the prediction model was: $ 0.06\times \left( {\mathrm{age}} \right)+4.76\times \left( {{{{\mathrm{short}-\mathrm{axis}}} \left/ {{\mathrm{long}-\mathrm{axis}\;\mathrm{ratio}}} \right.}} \right)+2.15\times \left( {\mathrm{internal}\;\mathrm{echo}} \right)+1.80\times \left( {\mathrm{vascular}\;\mathrm{pattern}} \right) $ . An extended model was constructed with four previous predictors and elasticity scores, using a logistic regression model.

Results

Final histology revealed 77 benign and 54 malignant LNs. In the elasticity score system, sensitivity was 66.7 %, specificity was 57.1 %, the positive predictive value (PPV) was 52.2 % and the negative predictive value (NPV) was 71.0 %. In the prediction model system, sensitivity was 79.6 %, specificity was 92.2 %, the PPV was 87.8 % and the NPV was 86.6 %. When the extended and the original model were compared, the areas under the receiver operating characteristic curve (c-statistic) was 0.94 and 0.95, respectively (P?>?0.05).

Conclusions

Qualitative RTE offers no additional value over conventional ultrasound in predicting malignancy in cervical LNs.

Key Points

? An ultrasound system can help in the assessment of cervical lymph nodes. ? Grey-scale and power Doppler ultrasound remain fundamental for neck nodal evaluation. ? Qualitative real-time elastography provided no additional value compared with current prediction models.     

Assesment of perfusion in glial tumors with arterial spin labeling; comparison with dynamic susceptibility contrast method

Purpose

Arterial spin labeling perfusion imaging (ASL-PI) is a non-invasive perfusion imaging method that can be used for evaluation and quantification of cerebral blood flow (CBF). Aim of our study was to evaluating the efficiency of ASL in histopathological grade estimation of glial tumors and comparing findings with dynamic susceptibility contrast perfusion imaging (DSC-PI) method.

Methods

This study involved 33 patients (20 high-grade and 13 low-grade gliomas). Multiphase multislice pulsed ASL MRI sequence and a first-passage gadopentetate dimeglumine T2*-weighted gradient-echo single-shot echo-planar sequence were acquired for all the patients. For each patient, perfusion relative signal intensity (rSI), CBF and relative CBF (rCBF) on ASL-PI and relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) values on DSC-PI were determined. The relative signal intensity of each tumor was determined as the maximal SI within the tumor divided by SI within symetric region in the contralateral hemisphere on ASL-PI. rCBV and rCBF were calculated by deconvolution of an arterial input function. Relative values of the lesions were obtained by dividing the values to the normal appearing symmetric region on the contralateral hemisphere. For statistical analysis, Mann–Whitney ranksum test was carried out. Receiver operating characteristic curve (ROC) analysis was performed to assess the relationship between the rCBF-ASL, rSI-ASL, rCBV and rCBF ratios and grade of gliomas. Their cut-off values permitting best discrimination was calculated. The correlation between rCBV, rCBF, rSI-ASL and rCBF-ASL and glioma grade was assessed using Spearman correlation analysis.

Results

There was a statistically significant difference between low and high-grade tumors for all parameters. Correlation analyses revealed significant positive correlations between rCBV and rCBF-ASL (r = 0.81, p < 0.001). However correlation between rCBF and rCBF-ASL was weaker (r = 0.64, p < 0.001).

Conclusion

Arterial spin labeling is an employable imaging technique for evaluating tumor perfusion non-invasively and may be useful in differentiating high and low grade gliomas.     

Carotid artery stenting in difficult aortic arch anatomy with or without a new dedicated guiding catheter: preliminary experience

Objectives

To evaluate carotid artery stenting (CAS) procedures with or without a new dedicated guiding catheter in anatomically challenging aortic arches in our experience.

Methods

We retrospectively reviewed 172 procedures of CAS performed from December 2006 to October 2011 in 159 consecutive patients (100 men, mean age 78 years): 15 patients had type III aortic arch, 13 had a bovine aortic arch, 6 had an acute angle at the origin of the left common carotid artery from the aortic arch, 2 had type III aortic arch with bovine aortic arch, and 1 had a bicarotid trunk with an aberrant right subclavian artery. In this group of difficult anatomy (37 cases), CAS was performed with (13 cases) or without (24 cases) a new dedicated guiding catheter.

Results

Mean time of fluoroscopy (16 min vs. 18 min, P?<?0.01), mean total procedural time (68 min vs. 83 min, P?<?0.001), technical failure (0/13 vs. 3/24 cases, P?=?0.01), clinical failure (0/13 vs. 4/21 cases, P?=?0.02) and local complications (0/13 vs. 2/24 cases, P?<?0.0001) were significantly lesser in the dedicated guiding catheter group.

Conclusions

The new dedicated guiding catheter may be more effective and less risky for CAS in anatomically challenging aortic arches.

Key Points

? Complex anatomy of the aortic arch is not rare ? Endovascular carotid artery stenting (CAS) is more difficult when the anatomy is complex ? A new dedicated guiding catheter may help CAS when the arch anatomy is complex ? The new dedicated guiding catheter may be less risky in complex arches     

Sixty-four-section CT cerebral perfusion evaluation in patients with carotid artery stenosis before and after stenting with a cerebral protection device

BACKGROUND AND PURPOSE: Brain tissue viability depends on cerebral blood flow (CBF) that has to be kept within a narrow range to avoid the risk of developing ischemia. The aim of the study was to evaluate by 64-section CT (VCT) the cerebral perfusion modifications in patients with severe carotid stenosis before and after undergoing carotid artery stent placement (CAS) with a cerebral protection system.MATERIALS AND METHODS: Fifteen patients with unilateral internal carotid stenosis (≥70%) underwent brain perfusional VCT (PVCT) 5 days before and 1 week after the stent-placement procedure. CBF and mean transit time (MTT) values were measured.RESULTS: Decreased CBF and increased MTT values were observed in the cerebral areas supplied by the stenotic artery as compared with the areas supplied by the contralateral patent artery (P < .001). A significant normalization of the perfusion parameters was observed after the stent-placement procedure (mean pretreatment MTT value, 5.3 ± 0.2; mean posttreatment MTT value, 4.3 ± 0.18, P < .001; mean pretreatment CBF value, 41.2 mL/s ± 2.1; mean posttreatment CBF value, 47.9 mL/s ± 2.9, P < .001).CONCLUSIONS: PVCT is a useful technique for the assessment of the hemodynamic modifications in patients with severe carotid stenosis. The quantitative evaluation of cerebral perfusion makes it a reliable tool for the follow-up of patients who undergo CAS.

Carotid artery stenosis, with its thromboembolic complications causing cerebral ischemia,^1,2 can be successfully treated by carotid endarterectomy (CEA), which significantly reduces the risk of stroke in both symptomatic and asymptomatic patients, as compared with medical therapy alone.^3,4 Alternatively, carotid artery stent placement (CAS) is increasingly used thanks to the development of safe and effective protection systems that help reduce the periprocedural neurologic complications.^5,6 Two recent registry studies (ARCHeR, Caress) have demonstrated that CEA and CAS are comparable in terms of periprocedural complications in symptomatic or asymptomatic patients not presenting comorbidities.^7,8 The overlapping percentage of complications between these 2 techniques at 30 days is 2%.Cerebral perfusion changes, such as an asymmetry in the hemisphere corresponding to the affected carotid artery, have been observed in patients with unilateral severe carotid stenosis, however without a direct correlation to the degree of stenosis.^9,10 A measure of perfusion disturbance as provided by cerebral blood flow (CBF) and mean transit time (MTT) appears to be helpful in evaluating brain with a risk of developing a stroke and eventually in guiding the therapeutic decisions especially in acute ischemic events.¹¹Positron-emission tomography (PET), single-photon emission CT (SPECT), xenon-enhanced CT (Xe-CT), perfusion CT (PCT), and MR imaging have all been applied in the study of brain hemodynamics. However, the scarce availability of PET and SPECT in most radiology departments or the difficulty in obtaining a quantitative measurement by MR imaging has drawn attention for >20 years toward Xe-CT,¹² whose demonstrated accurate measurement of perfusion¹³ has permitted the differentiation of patients with normal CBF¹⁴ from those with reversible neurologic deficits (CBF, 10–20 mL/100 g per minute) or those with infarction (CBF < 10 mL/100 g per minute).¹³ PCT, validated by comparison with Xe-CT^13,14 and widely available in most radiology departments, can be easily performed at the end of a CT scanning and has, therefore, further simplified the approach to brain perfusion evaluation,^15,16 adding further information about hemodynamic parameters such as MTT and cerebral blood volume. More recently, the perfusion study by 64-section CT (VCT), allowing the assessment of a brain volume ≤4 cm, has offered an improved tool of investigation.The aim of our study was to measure by brain perfusional VCT (PVCT) the hemodynamic parameters in the cerebral hemisphere supplied by the severely stenotic internal carotid artery (ICA), in a group of patients undergoing an endovascular treatment with a protection device. The hypothesis is that CBF and MTT values in the hemisphere on the side of the carotid stenosis will be abnormal before the procedure and will approach the values on the contralateral side after the procedure.     

Whole-brain CT perfusion: reliability and reproducibility of volumetric perfusion deficit assessment in patients with acute ischemic stroke

Introduction

The aim of this study was to examine reliability and reproducibility of volumetric perfusion deficit assessment in patients with acute ischemic stroke who underwent recently introduced whole-brain CT perfusion (WB-CTP).

Methods

Twenty-five consecutive patients underwent 128-row WB-CTP with extended scan coverage of 100 mm in the z-axis using adaptive spiral scanning technique. Volumetric analysis of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), time to peak (TTP), and time to drain (TTD) was performed twice by two blinded and experienced readers using OsiriX V.4.0 imaging software. Interreader agreement and intrareader agreement were assessed by intraclass correlation coefficients (ICCs) and Bland–Altman Analysis.

Results

Interreader agreement was highest for TTD (ICC 0.982), followed by MTT (0.976), CBF (0.955), CBV (0.933), and TTP (0.865). Intrareader agreement was also highest for TTD (ICC 0.993), followed by MTT (0.988), CBF (0.981), CBV (9.953), and TTP (0.927). The perfusion deficits showed the highest absolute volumes in the time-related parametric maps TTD (mean volume 121.4 ml), TTP (120.0 ml), and MTT (112.6 ml) and did not differ significantly within this group (each with p?>?0.05). In comparison to time-related maps, the mean CBF perfusion deficit volume was significantly smaller (92.1 ml, each with p?<?0.05). The mean CBV lesion size was 23.4 ml.

Conclusions

Volumetric assessment in WB-CTP is reliable and reproducible. It might serve for a more accurate assessment of stroke outcome prognosis and definition of flow-volume mismatch. Time to drain showed the highest agreement and therefore might be an interesting parameter to define tissue at risk.     

Novel 3D-CT evaluation of carotid stent volume: greater chronological expansion of stents in patients with vulnerable plaques

Introduction

Although self-expanding carotid stents may dilate gradually, the degrees of residual stenosis have been quantified by the NASCET criteria, which is too simple to reflect the configuration of the stented artery. We measured the volumes of the stent lumens chronologically by 3D-CT in patients after carotid artery stenting (CAS), and analyzed the correlations between the volume change and medical factors.

Methods

Fourteen patients with carotid artery stenosis were treated using self-expanding, open-cell stents. All patients underwent preoperative plaque MRI (magnetization-prepared rapid acquisition gradient-echo, MPRAGE) and chronological 3D-CT examinations of their stents immediately after their placement and 1 day, 1 week, and 1 month after the procedure. The volume of the stent lumen was measured using a 3D workstation. The correlations between stent volume and various factors including the presence of underlying diseases, plaque characteristics, and the results of the CAS procedure were analyzed.

Results

Stent volume gradually increased in each case and had increased by 1.04–1.55 (mean, 1.25)-fold at 1 postoperative month. The presence of underlying medical diseases, plaque length, the degree of residual stenosis immediately after CAS, and plaque calcification did not have an impact on the change in stent volume. On the other hand, the stent volume increase was significantly larger in the patients with vulnerable plaques that demonstrated high MPRAGE signal intensity (P?<?0.05).

Conclusions

A 3D-CT examination is useful for precisely measuring stent volume. Self-expanding stents in carotid arteries containing vulnerable plaques expand significantly more than those without such plaques in a follow-up period.     

Magnetic resonance plaque imaging to predict the occurrence of the slow-flow phenomenon in carotid artery stenting procedures

Introduction

The purpose is to investigate the feasibility of magnetic resonance (MR) plaque imaging in predicting the arterial flow impairment (slow-flow phenomenon) during carotid artery stenting (CAS) using a filter-type protection device.

Methods

Thirty-one carotid artery stenotic lesions in 30 patients (28 men and two women; mean age, 71.8 years) were evaluated by MR plaque imaging with black blood T1- and T2-weighted and time-of-flight sequences before CAS. Main plaque components were classified as vulnerable (intraplaque hemorrhage and lipid-rich/necrotic core) or stable (fibrous tissue and dense calcification) from the signal pattern. The plaque classification was statistically compared with the occurrence of slow-flow phenomenon.

Results

The slow-flow phenomenon was observed in ten CAS procedures (five flow arrests and five flow reductions). Flow arrests consisted of four vulnerable and one stable plaque, and flow reductions consisted of four vulnerable and one stable plaque. The slow-flow phenomenon occurred significantly (P?<?0.01) more frequently in patients with vulnerable plaque.

Conclusions

Vulnerable carotid plaques have a significantly higher risk of slow-flow phenomenon than stable plaques. The occurrence of the slow-flow phenomenon can be predicted by MR plaque imaging before CAS.     

Validation and absolute quantification of MR perfusion compared with CT perfusion in patients with unilateral cerebral arterial stenosis

Objective

The aim of the study was to assess absolute quantification of dynamic susceptibility contrast-enhanced magnetic resonance perfusion (MRP) comparing with computed tomography perfusion (CTP) in patients with unilateral stenosis.

Materials and methods

We retrospectively post-processed MRP in 20 patients with unilateral occlusion or stenosis of >79% at the internal carotid artery or the middle cerebral artery (MCA). Absolute quantification of MRP was performed after applying the following techniques: cerebrospinal fluid removal, vessel removal, and automatic segmentation of brain to calculate the scaling factors to convert relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) values to absolute values. For comparison between MRP and CTP, we manually deposited regions of interest in bilateral MCA territories at the level containing the body of the lateral ventricle.

Results

The correlation between MRP and CTP was best for mean transit time (MTT) (r = 0.83), followed by cerebral blood flow (CBF) (r = 0.52) and cerebral blood volume (CBV) (r = 0.43). There was no significant difference between CTP and MRP for CBV, CBF, and MTT on the lesion side, the contralateral side, the lesion-contralateral differences, or the lesion-to-contralateral ratios (P > 0.05). The mean differences between MRP and CTP were as follows: CBV −0.57 mL/100 g, CBF 2.50 mL/100 g/min, and MTT −0.90 s.

Conclusion

Absolute quantification of MRP is possible. Using the proposed method, measured values of MRP and CTP had acceptable linear correlation and quantitative agreement.     

Regional cerebral perfusion in patients with Alzheimer’s disease and mild cognitive impairment: effect of APOE Epsilon4 allele

Introduction

The objective of this study was to evaluate the effect of apolipoprotein E (APOE) epsilon 4 allele on regional cerebral perfusion (rCBF) changes using arterial spin labeling (ASL) magnetic resonance imaging (MRI) in subjects who are carriers or noncarriers of this risk factor for Alzheimer disease (AD).

Methods

Twenty-five subjects with AD, 25 with amnestic mild cognitive impairment (MCI) and 25 cognitively normal (CN) subjects underwent isotropic volumetric T1-weighted imaging and pulsed ASL MRI. All subjects were divided into carrier or noncarriers of the epsilon4 allele. Voxel-based statistical analyses were performed among groups on rCBF by ANOVA tests. In each subject group, we also evaluated the rCBF change between carrier and noncarrier groups.

Results

rCBF was significantly reduced in AD subjects compared to other subjects. In CN and AD subjects, rCBF in the carrier group was significantly reduced in several areas of the brain compared with that of the noncarrier group. In the carrier group, rCBF was significantly increased in the right parahippocampal gyrus, the bilateral cingulate gyri and the right posterior cingulate on the MCI group in addition to the right superior frontal gyrus in the AD group.

Conclusion

rCBF in the CN and AD groups were significantly reduced in the subjects with the carriers of the epsilon4 allele, which is a risk factor for Alzheimer’s disease. In addition, rCBF in the MCI group was significantly increased in subjects who were carriers. Therefore, rCBF can be used as a biomarker to show disease progression in areas of the brain of MCI subjects.