Monitor Perfusion Changes Research Articles

Monitoring Muscle Perfusion in Rodents During Short-Term Ischemia Using Power Doppler Ultrasound.

The aim of this work was to evaluate the reliability of power Doppler ultrasound (PD-US) measurements made without contrast enhancement to monitor temporal changes in peripheral blood perfusion. On the basis of pre-clinical rodent studies, we found that combinations of spatial registration and clutter filtering techniques applied to PD-US signals reproducibly tracked blood perfusion in skeletal muscle. Perfusion is monitored while modulating hindlimb blood flow. First, in invasive studies, PD-US measurements in deep muscle with laser speckle contrast imaging (LSCI) of superficial tissues made before, during and after short-term arterial clamping were compared. Then, in non-invasive studies, a pressure cuff was employed to generate longer-duration hindlimb ischemia. Here, B-mode imaging was also applied to measure flow-mediated dilation of the femoral artery while, simultaneously, PD-US was used to monitor downstream muscle perfusion to quantify reactive hyperemia. Measurements in adult male and female mice and rats, some with exercise conditioning, were included to explore biological variables. PD-US methods are validated through comparisons with LSCI measurements. As expected, no significant differences were found between sexes or fitness levels in flow-mediated dilation or reactive hyperemia estimates, although post-ischemic perfusion was enhanced with exercise conditioning, suggesting there could be differences between the hyperemic responses of conduit and resistive vessels. Overall, we found non-contrast PD-US imaging can reliably monitor relative spatiotemporal changes in muscle perfusion. This study supports the development of PD-US methods for monitoring perfusion changes in patients at risk for peripheral artery disease.

Quantification of Cerebral Perfusion using Laser Speckle Imaging and Infarct Volume using MRI in a Pre-clinical Model of Posterior Circulation Stroke.

Basilar artery occlusion (BAO) is a subset of posterior circulation stroke that carries a mortality as high as 90%. The current clinical standard to diagnose ischemic stroke include computerized tomography (CT), CT angiography and perfusion and magnetic resonance imaging (MRI). Large animal pre-clinical models to accurately reflect the clinical disease as well as methods to assess stroke burden and evaluate treatments are lacking. We describe a canine model of large vessel occlusion (LVO) stroke in the posterior circulation, and developed a laser speckle imaging (LSI) protocol to monitor perfusion changes in real time. We then utilized high b-value DWI (b=1800s/mm2) MRI to increase detection sensitivity. We also evaluated the ability of magnetic resonance angiography (MRA) to assess arterial occlusion and correlate with DSA. Finally, we verified infarct size from apparent diffusion coefficient (ADC) mapping with histology. Results: Administration of thromboembolism occluded the basilar artery as tracked by DSA (n=7). LSI correlated with DSA, demonstrating a reduction in perfusion after stroke onset that persisted throughout the experiment, allowing us to monitor perfusion in real time. DWI with an optimized b-value for dogs illustrated the stroke volume and allowed us to derive ADC and magnetic resonance angiography (MRA) images. The MRA performed at the end of the experiment correlated with DSA performed after occlusion. Finally, stroke burden on MRI correlated with histology. Our studies demonstrate real time perfusion imaging using LSI of a canine thromboembolic LVO model of posterior circulation stroke, which utilizes multimodal imaging important in the diagnosis and treatment of ischemic stroke.

Intraoperative contrast-enhanced ultrasonography for microcirculatory evaluation in rhesus monkey with spinal cord injury.

This study tried to quantify spinal cord perfusion by using contrast-enhanced ultrasound (CEUS) in rhesus monkey models with acute spinal cord injury. Acute spinal cord perfusion after injury was detected by CEUS, coupling with conventional ultrasound (US) and Color Doppler US (CDFI). Time-intensity curves and perfusion parameters were obtained by autotracking contrast quantification (ACQ) software in the epicenter and adjacent regions of injury, respectively. Neurological and histological examinations were performed to confirm the severity of injury. US revealed spinal cords were hypoechoic and homogeneous, whereas dura maters, pia maters, and cerebral aqueducts were hyperechoic. After spinal cord contusion, the injured spinal cord was hyperechoic on US, and intramedullary vessels of adjacent region of injury were increased and dilated on CDFI. On CEUS hypoperfusion were found in the epicenter of injury, while hyperperfusion in its adjacent region. Quantitative analysis showed that peak intensity (PI) decreased in epicenters of injury but significantly increased in adjacent regions at all time points (p < 0.05). Functional evaluation demonstrated significant deterioration compared to pre-contusion (p < 0.05). Quantitative analysis with CEUS is a promising method for monitoring perfusion changes of spinal cord injury in overall views and real-time.

Evaluation of regional cerebral perfusion after subarachnoid hemorrhage by multi spiral CT perfusion

Objective To explore the chiaical value of cerebral perfusion reduction after subarachnoid hemorrhage(SAH)by multi spiral CT perfusion in rabbits.Methods 32 male Japanese big-ear rabbits of clean level were randomly divided into 2 groups:Group A(n =8),the normal group,were to obtain normal MS-CTP values of rabbit cerebrums;Group B(n =24),the SAH group was made into two-hemorrhage animal models,checked on seven day by multi spiral CT perfusion.The source data was transmitted to the post-processing workstation ADW 4.2.Perfusion parameters maps(CBF)of both sides of frontal,parietal and basal ganglia were got by computing.Each rabbit was killed immediately after scanning,and the spider blood was observed.Results The average CBF value of the two groups:The difference was not statistically significant at the frontal(t =1.740,P =0.092)and parietal(t =1.868,P =0.072); The average values of CBF were significantly decreased at the basal ganglia(t =2.481,P =0.019).Group B showed the distribution of blood clot in the basal cistern,but there was no blood clot at the frontal and parietal.Conclusion The monitor perfusion changes of rabbit brain after SAH could be detected by MS-CTP,and the lower of regional cerebral perfusion had a relationship with the distribution with the blood clot,and it could instruct the early diagnosis of cerebral perfusion,and the clinical benefit to early intervention treatment. Key words: Subarachnoid hemorrhage; Tomograpby, X-ray computed; Perfusion; Cerebrum

Effect of transmyocardial laser revascularization on myocardial perfusion and left ventricular remodeling after myocardial infarction in rats.

To monitor perfusion changes in remote myocardium caused by transmyocardial laser revascularization (TMLR) and to investigate the influence of TMLR on left ventricular morphology and function. The coronary arteries were ligated in 32 Wistar rats. Eight weeks later, cine magnetic resonance (MR) imaging was performed in both the treatment (n = 12) and control group (n = 8). TMLR was then performed in the remote myocardium in the treated group. Twelve weeks after myocardial infarction, cine MR imaging, including dobutamine-induced (10 micro g per kilogram of body weight per minute via the tail vein) stress, was repeated and followed with hemodynamic measurements in both groups and with perfusion MR imaging (in-plane resolution, 140 x 140 micro m) of the isolated heart at rest and during nitroglycerin-induced stress in the TMLR group (n = 10). Left ventricular dilatation and hypertrophy were enhanced in the TMLR group (change in end-diastolic volume at 8-12 weeks: control group, 24.6 micro L +/- 16.7 and TMLR group, 81.7 micro L +/- 15.7; change in left ventricular mass: control group, 54.5 mg +/- 19.2 and TMLR group, 124.1 mg +/- 30.7; P <.03 for both). Ejection fractions at rest were approximately equal (control group, 40% +/- 2; TMLR group, 38% +/- 2; P value not significant), but during dobutamine-induced stress, the ejection fraction was higher in the TMLR group (54.4% +/- 4.9; control group, 47.4% +/- 4.8; P <.05). TMLR-treated areas were better perfused than was untreated myocardium (difference in perfusion: TMLR-treated vs control region, 3.89 mL/min/g +/- 0.83 at rest vs 2.29 mL/min/g +/- 1.06 during nitroglycerin-induced stress; P <.05 for both). Hemodynamic measurements revealed no differences between groups. High-spatial-resolution perfusion MR imaging depicted a significant perfusion improvement after TMLR. Post-myocardial infarction remodeling of the left ventricle was found to be enhanced.

Unilateral kidney blood flow measurement using the 81Rb/81mKr ratio.

A new method has been developed for the continuous quantification of kidney blood flow, utilizing the unique physical and biological properties of the radioactive tracer couple: rubidium-81/krypton-81m. After intravenous injection, 81Rb concentrates primarily in the kidneys, where it continuously generates the radioactive inert gas 81mKr. This ultrashort-lived isotope is continuously washed out from the tissue at a rate proportional to the blood flow. The radiation emitted from within the kidney is externally detected and analyzed to yield the 81Rb/81mKr ratio. 21 animal experiments have confirmed that this ratio is at any time an accurate measure of the kidney perfusion. The 81Rb/81mKr ratio method has proved to provide a non-invasive way to selectively quantify the blood flow in each kidney, to monitor perfusion changes and to image the distribution of blood flow in a functional scintigram.