Dynamic CT brain scanning in the haemodynamic evaluation of cerebral arterial occlusive disease

Relation of serum uric acid to asymptomatic proximal extracranial artery stenosis in a middle-aged Chinese population: a community-based cross-sectional study

OBJECTIVE

Serum uric acid (SUA) has been associated with cardiovascular diseases, including atherosclerosis and carotid artery stenosis. However, data on the relationship between SUA level and proximal extracranial artery stenosis (PEAS) are limited. Therefore, this study investigates the association between SUA levels and the risk of PEAS in asymptomatic Chinese population.

SETTING

This community-based cross-sectional study was conducted in Jidong Community Hospital, Tangshan, Hebei, China between July 2013 and August 2014.

PARTICIPANTS

The study examined 3325 asymptomatic participants (40-60 years) to evaluate the risk of PEAS.

RESULTS

For the participants stratified into quartiles based on gender-specific SUA levels, the prevalence of PEAS increased from Q1 to Q4 from 12.3% to 29.8% in the vertebral artery (VA), and from 2.8% to 5.8% in the common carotid artery. The proportion of PEAS relative to the detected number of arterial stenosis was lower in Q1 than in Q2-Q4. The multivariable ORs and 95% CI of PEAS in the second through fourth compared with the lowest quartiles for arterial stenosis were 1.278 (0.980 to 1.665), 1.117 (0.851 to 1.468) and 1.375 (1.033 to 1.830) (p_trend=0.0399); and for VA stenosis, 1.285 (0.966 to 1.709), 1.085 (0.808 to 1.457) and 1.439 (1.061 to 1.952) (p_trend=0.0235).

CONCLUSION

Elevated SUA concentration is significantly associated with PEAS in an asymptomatic middle-aged Chinese population, and vertebral arteries appeared to be the most vulnerable vessels.

Delayed Transcranial Echo-Contrast Bolus Arrival in Unilateral Internal Carotid Artery Stenosis and Occlusion

Some patients with internal carotid artery (ICA) occlusion or stenosis are at risk of developing a hemodynamic stroke. Transcranial ultrasonography using an echo-contrast bolus technique might be able to assess the extent of hemodynamic compromise. We describe a transcranial Doppler sonographic method that analyzes the differences in echo-contrast bolus arrival between both middle cerebral arteries after intravenous echo-contrast application. Ten patients with 50%-79% ICA stenosis, 10 patients with 80%-99% ICA stenosis and 22 patients with ICA occlusion were studied and compared with 15 age-matched controls. There were significant increases in delayed filling of the middle cerebral artery in both 80%-99% stenoses and occlusions compared with controls. The extent of the observed delays did not correlate with vasomotor reactivity. Echo-contrast bolus arrival time can be used to gain additional information on the intracranial hemodynamic effects of extracranial carotid artery disease that seems to be independent of the established ultrasound indices.

Symptomatic carotid artery occlusion. A reappraisal of hemodynamic factors

BACKGROUND

Over the last several years evidence has accumulated that in addition to embolism, a compromised cerebral blood flow may play an important role in causing transient ischemic attacks and ischemic stroke in patients with occlusion of the internal carotid artery. This evidence is found in both clinical features and ancillary investigations, particularly measurements of cerebral blood flow.

SUMMARY OF REVIEW

On the basis of 20 follow-up studies in patients with transient ischemic attacks or minor ischemic stroke associated with an occluded carotid artery, the annual risk of stroke was 5.5% (95% confidence interval [CI], 5.0% to 6.0%), and that of ipsilateral stroke (distinguished in 11 of the 20 studies) was 2.1% (95% CI, 1.6% to 2.8%). Patients with a compromised cerebral blood flow as measured by positron emission tomography, single-photon emission CT, transcranial Doppler, or stable xenon CT (six studies) have an even higher annual risk of stroke (all strokes: 12.5%; 95% CI, 8.9% to 17.6%; ipsilateral stroke: 9.5%; 95% CI, 6.4% to 14.0%).

CONCLUSIONS

Because a compromised cerebral blood flow may be an important causal factor in patients with symptomatic carotid artery occlusion, medical and surgical options for treatment are reviewed in this light.

Evaluation of hydrocephalic periventricular radiolucency by dynamic computed tomography and xenon-computed tomography

OBJECTIVE

A common finding of computed tomography in a case of normal-pressure hydrocephalus (NPH) is periventricular radiolucency (PVL). We analyzed PVL for patients with hydrocephalus, using dynamic computed tomographic and xenon-computed tomographic techniques to differentiate NPH from similar diseases.

METHODS

Dynamic computed tomography was evaluated as a method of diagnosing NPH in 14 patients with computed tomographic findings of both PVL and ventricular dilatation. Of the 14 patients, varying degrees of clinical improvement after shunt surgery were observed in 10 (shunt-effective group) but not in the remaining 4 (shunt-ineffective group). The difference in arrival time between PVL and thalamus, the difference in peak time between PVL and anterior cerebral artery, and cerebral blood flow in PVL by xenon-computed tomographic study were analyzed.

RESULTS

The difference in arrival time between PVL and thalamus was significantly longer in the effective group than among the remaining patients. There was no significant difference in PVL/cerebral blood flow and the difference in peak time between PVL and the anterior cerebral artery between the two groups.

CONCLUSION

Dynamic computed tomographic analysis of the difference in arrival time between PVL and thalamus is useful for diagnosing NPH and predicting response to shunting.

Functional perfusion and blood-brain barrier permeability images in the diagnosis of cerebral tumors by Angio CT

We performed rapid sequential CT scanning following iv injection of a bolus of contrast medium and generated three functional images relating to intravascular circulation time (rABCT), vascular volume (Vv) density and blood-brain barrier (BBB) unidirectional constant uptake rate (Ki), respectively. This was accomplished by calculating the first mathematical moment of the monitored time-density curves about the injection time and from the multiple time graph analysis described by Patlack and co-workers. A satisfactory resolution was achieved, allowing separate appreciation of changes in rABCT both in large vessels and in tissue small vessels. Combined evaluation of rABCT and Vv images allowed us to differentiate between tumors.

Functional circulation and blood-brain permeability images by Angio CT in the assessment of cerebral ischemia

We performed rapid sequential computerized tomography (CT) scanning following i.v. injection of a bolus of contrast medium, and generated three functional images related, respectively, to intravascular circulation time (rABCT), vascular volume density (Vv) and blood-brain barrier (BBB) unidirectional constant uptake rate (Ki). This was accomplished by calculating the first mathematical moment of the monitored time-density curves about the injection time, and by the multiple time graph analysis described by Patlack and coworkers. A satisfactory resolution was achieved, allowing separate appreciation of changes in rABCT both at large vessels and at tissue small vessels. Combined evaluation of rABCT and Vv images allowed us to draw qualitative conclusions about blood flow and perfusion reserve.

Functional vascular volume and blood-brain barrier permeability images by angio-CT in the diagnosis of cerebral lesions

We performed angio-CT following i.v. administration of an iodinated contrast medium and analyzed the pixel contrast time-density curves from 4 to 10 min postinjection to derive vascular and volume BBB permeability images. This was performed by applying multiple regression analysis of pixel contrast curves versus blood contrast and integrated blood contrast curves. The two regression coefficients, mapped pixel by pixel, correspond respectively to vascular volume and BBB unidirectional transport rate. Initial application in a small number of normal subjects and patients allowed us to characterize areas of steady-state contrast enhancement according to changes of vascular volume and BBB permeability.

Hemodynamic assessment of vascular malformations by angio CT with generation of functional transit time images

We performed a CT dynamic study during the first pass of an intravenously injected bolus of a iodinated contrast medium, followed by generation of the regional arm-brain circulation time (rABCT) image, in 11 patients with vascular malformations. All lesions could be detected as changes of rABCT, and the comparison with values of normal arteries and veins allowed the deduction of the hemodynamic conditions of the lesions. Seven cases showed evidence of altered distribution of rABCT in the corresponding brain hemisphere, suggesting a perfusion reserve impairment.

Functional circulation time images in the diagnosis of cerebral lesions by angio CT

An application of angio CT as an adjunct to contrast enhancement evaluation of cerebral lesions is presented. We performed rapid sequential scanning following intravenous bolus injection of an iodinated contrast medium, analyzed the time contrast curves and generated a functional circulation time image. This was accomplished by calculating on a pixel-by-pixel basis the first mathematical moment of the monitored time-density curves about injection time which corresponds to regional arm brain circulation time (rABCT). This method increased the rate of detection of cerebral lesions by contrast enhancement from 30 to 90%.

Dynamic computed tomography and functional imaging in cerebral arterial occlusive disease: analysis in the chronic phase

Dynamic CT was conducted on 10 patients with internal carotid artery (ICA) or middle cerebral artery (MCA) occlusion or stenosis and 14 controls. All the patients were chronic phase and they only presented small infarctions on CT. Those with ICA or MCA occlusions and insufficient collateral circulations showed delayed mean transit time and peak time of the affected side on functional image and in parameter analysis (P less than 0.01) compared with those of controls. A statistically significant positive coefficient of correlation was noted between the degree of the anterior horn dilatation of lateral ventricle and delay in mean transit time of the affected MCA area (r = 0.62, P less than 0.01).