Cerebral blood flow mapping using stable Xenon-enhanced CT in sickle cell cerebrovascular disease

Summary The cerebral blood flow (CBF) of 25 patients with sickle cell cerebrovascular disease (SCCVD) was examined using a Xenon-CT flow mapping method. Brain CT and MR findings were correlated with those of the Xenon-CT flow studies. CBF defects on Xenon-CT correlated reasonably well with the areas of cortical infarctions on the MR images, but in 27% of the cases, flow defects were slightly larger than the areas of infarctions on the MR images. In deep watershed or basal ganglia infarctions, abnormal CBF was noted about the cerebral cortex near infarctions in 72% of the patients, regardless of infarction sizes on the MR images. However, decreased CBF was recognized in 4 of the 9 children whose MR images were virtually normal. Thus, the extent of flow depletion cannot be predicted accurately by MR imaging alone. Xenon-CT flow mapping proved a safe and reliable procedure for evaluation of the CBF of patients with SCCVD. Although this study is preliminary, it may have a potential in selecting patients for hypertransfusion therapy, as a noninvasive test and for following children with SCCVD during their therapy. Careful correlation of results of CBF with those of MR imaging or of CT is important for objective interpretations of flow mapping images.     

Comparison of cerebral perfusion reserve and collateral circulation in patients with internal carotid artery disease

Summary The cerebral hemodynamics in patients with carotid disease is influenced by a network of extra- and intracranial collaterals. The purpose of this study was to compare the findings of regional cerebral perfusion reserve (rCPR) with angiographically proven collateral circulation. In 41 patients (28 men, 13 women, age 63 ± 10 years) with angiographically proven carotid stenoses or occlusions (30 stenoses, 11 occlusions) 24 ^{99 m}Tc-HMPAO-SPECT and 25 dynamic Xe-CT investigations were conducted, both before and after acetazolamide stimulation. rCPR was quantified as the ratio (1) of the absolute rCBF values obtained by Xe-CT and (2) of the count density measured by HMPAO-SPECT of the acetazolamide administration. A rCPR of less than 95 % in a vascular territory was classified as compromised rCPR. A recent CT examination was available in all cases. According to the angiographic findings the patients could be classified into (1) group A (n = 9) with residual carotid perfusion, (2) Group B (n = 8) with collateralization via the circle of Willis, and (3) group C (n = 24) with leptomeningeal or ophthalmic artery collateral circulation. The rCPR values were significantly different in groups B and C with both methods, Xe-CT (P = 0.0035) and HMPAO-SPECT (P = 0.0014). rCPR was decreased in 13/14 group C patients investigated with Xe-CT and in 11/14 examined with HMPAO-SPECT. All patients in group B showed normal rCPR according to Xe-CT and HMPAO-SPECT. In group A, six of seven revealed decreased rCPR on Xe-CT, while rCPR values were normal in all four group A-patients examined with HMPAO-SPECT. The cerebral hemodynamics depend on a collateralization network and not only on the degree of internal carotid artery (ICA) stenosis. A decreased CPR in a vascular territory ipsilateral to an ICA stenosis or occlusion correlates strongly with the angiographic finding of leptomeningeal or ophthalmic artery collateral circulation.      

氙CT指导脑血运重建术治疗症状性前循环动脉狭窄及闭塞

目的 探讨氙CT脑血流灌注成像技术在脑血运重建术前及疗效评估中的作用。方法 回顾性分析15例症状性前循环供血动脉粥样硬化性狭窄或闭塞患者的临床资料,其中行血管内支架置入术8例、颈内动脉内膜切除术1例和颞浅动脉-大脑中动脉旁路移植术6例,对比术前与术后2周内氙CT检测的局部脑血流量(r CBF)及术后6个月改良Rankin量表(mRS)评分。结果 (1)12例术前靶血管远端血流灌注异常患者平均r CBF值为(30±10)ml/(100 g·min),术后为(32±14)ml/(100 g·min),与术前比较差异有统计学意义(P=0.044);3例术前靶血管远端血流灌注正常患者平均r CBF值为(48±6)ml/(100 g·min),术后平均r CBF值为(50±7)ml/(100 g·min),与术前比较差异无统计学意义(P0.05)。(2)术后mRS评分改善8例,稳定7例。15例患者术后mRS评分为[1(0,3)]分,与术前[3(1,3)]分比较,差异有统计学意义(P0.05)。随访期间无一例新发神经功能障碍。结论 血运重建术可改善术前存在血流动力学障碍的症状性前循环供血动脉狭窄或闭塞患者的靶血管远端局部脑血流灌注及神经功能缺损症状,而术前氙CT脑血流灌注成像灌注异常可能较灌注正常患者获益更多。     

Regional cerebral blood flow levels as measured by xenon-CT in vascular territorial low-density areas after subarachnoid hemorrhage are not always ischemic

Introduction The aim of this study was to assess regional cerebral blood flow (rCBV) in areas of CT hypoattenuation appearing in the postoperative period in patients treated for aneurysmal subarachnoid hemorrhage (SAH) using xenon-enhanced CT scanning (Xe-CT).Methods We analyzed 15 patients (5 male and 10 female; mean age 49.7±12.1 years) with SAH on CT performed on admission to hospital and who showed a low-density area within a well-defined vascular territory on CT scans after clipping or coiling of a saccular aneurysm. All zones of hypoattenuation were larger than 1 cm² and showed signs of a mass effect suggesting a subacute phase of evolution. Two aneurysms were detected in two patients. Aneurysms were located in the middle cerebral artery (n=7), in the anterior communicating artery (n=6), in the internal carotid artery (n=3), and in the posterior communicating artery (n=1). Treatments were surgical (n=8), endovascular (n=2) or both (n=1). A total of 36 Xe-CT studies were performed and rCBF values were measured in two different regions of interest (ROI): the low-density area, and an area of normal-appearing brain tissue located symmetrically in the contralateral hemisphere.Results rCBF levels were significantly lower in the low-density area than in the contralateral normal-appearing area (P<0.01). In the low-density areas, irreversible ischemia (CBF <10 ml/100 g per minute) was present in 11/36 lesions (30.6%), ischemic penumbra (CBF 10–20 ml/100 g per minute) and oligemia (CBF 20–34 ml/100 g per minute) in 8/36 lesions (22.2%), relative hyperemia (CBF 34–55 ml/100 g per minute) in 7/36 lesions (19.4%), and absolute hyperemia (CBF >55 ml/100 g per minute) in 2/36 lesions (5.6%).Conclusion Our study confirmed that rCBF is reduced in new low-density lesions related to specific vascular territories. However, only about one-third of the lesions showed rCBF levels consistent with irreversible ischemia and in a relatively high proportion of lesions, rCBF levels indicated penumbral, oligemic and hyperemic areas.     

Treatment of hemodynamic insufficiency in chronic CCA occlusion using a short saphenous vein interposition graft: diagnostic and technical considerations

Extracranial–intracranial bypass surgery has been shown to reverse hemodynamic insufficiency on the basis of steno-occlusive disease of the internal carotid artery (ICA) or middle cerebral artery. In contrast, chronic occlusion of the common carotid artery (CCA) without extracranial donor vessels affords alternative revascularization procedures as well as a more elaborate preoperative workup. This case is intended to illustrate the specific diagnostic approach and considerations as well as a beneficial treatment modality in the setting of pronounced hemodynamic insufficiency as a consequence of a CCA occlusion, in conjunction with contralateral CCA and ICA stenoses. A 61-year-old man complaining of new onset aphasia underwent vascular imaging that revealed a proximal occlusion of the left CCA with a concomitant patent proximal ICA on ultrasound. Functional cerebral blood flow measurement including Xenon-enhanced computer tomography showed corresponding chronic hemodynamic insufficiency of the left hemisphere. The patient received a modified revascularization procedure, where a saphenous vein was used as interposition graft between the subclavian artery and the left proximal ICA. Postoperatively, both clinical and morphological improvement were noted. Successful treatment of hemodynamic insufficiency because of chronic CCA occlusion necessitates a thorough preoperative workup and application of alternative revascularization strategies.