Canine Stroke Model Research Articles

Efficacy Assessment of Cerebral Perfusion Augmentation through Functional Connectivity in an Acute Canine Stroke Model.

Ischemic stroke disrupts functional connectivity within the brain's resting-state networks (RSNs), impacting recovery. This study evaluates the effects of norepinephrine and hydralazine (NEH), a cerebral perfusion augmentation therapy, on RSN integrity in a hyperacute canine stroke model. Fifteen adult purpose-bred mongrel canines, divided into treatment and control (natural history) groups, underwent endovascular induction of acute middle cerebral artery occlusion (MCAO). Postocclusion, the treatment group received intra-arterial norepinephrine (0.1-1.52 µg/kg/min, adjusted for 25-45 mm Hg above baseline mean arterial pressure) and hydralazine (20 mg). Resting-state fMRI (rs-fMRI) data were acquired with a 3T scanner by using a blood oxygen level dependent-EPI sequence (TR/TE = 1400 ms/20 ms, 2.5 mm slices, 300 temporal positions). Preprocessing included motion correction, spatial smoothing (2.5 mm full width at half maximum), and high-pass filtering (0.01 Hz cutoff). Functional connectivity within RSNs were analyzed through group-level independent component analysis and weighted whole-brain ROI-to-ROI connectome, pre- and post-MCAO. NEH therapy significantly maintained connectivity post-MCAO in the higher-order visual and parietal RSNs, as evidenced by thresholded statistical mapping (threshold-free cluster enhancement P corr > .95). However, this preservation was network-dependent, with no significant (P corr < .95) changes in the primary visual and sensorimotor networks. NEH demonstrates potential as a proof-of-concept therapy for maintaining RSN functional connectivity after ischemic stroke, emphasizing the therapeutic promise of perfusion augmentation. These insights reinforce the role of functional connectivity as a measurable end point for stroke intervention efficacy, suggesting clinical translatability for patients with insufficient collateral circulation.

Optimal technique for canine mesenchymal stem cells labeling with novel SPIO, MIRB™: for MRI detection of transplanted stem cells canine stroke model

ABSTRACT Background Cell-based therapy has emerged as a promising avenue for post-stroke recovery. A significant challenge lies in tracking the distribution and engraftment of transplanted cells within the target cerebral tissue. To address this, we turn to the potential of Brain MRI detection of mesenchymal stem cells (MSCs), achieved by labeling these cells with superparamagnetic iron oxide (SPIO). This is the first report of a technique to label canine MSCs using a commercially available SPIO, Molday ION Rhodamine B (MIRB), to optimize both viability and labeling efficacy for transplantation purposes.” Method Canine MSCs were incubated with addition of different MIRB concentration from 0, 10, 20, 30 μg Fe/ml. The cellular uptake of MIRB was confirmed through the analysis of fluorescent images and flow cytometry. The morphological characteristics of MSCs were assessed via microscopic visualization. Cellular viability was evaluated using both a cellometer and flow cytometry. Result Fluorescent microscopic images of all MIRB incubated MSCs groups show >70% labeled cells with homogenous signal intensity. Notably, the morphology of MSCs remained unaltered in the 10 μg Fe/ml group compared to the control group. Furthermore, among the labeled groups, the 10 μg Fe/ml concentration exhibited the highest viability when assessed using two different flow cytometry methods (95.3%, p < 0.05). Conclusion This study successfully labels canine MSCs with MIRB. The optimal concentration of 10 μg Fe/ml demonstrates optimal viability, labeling efficacy, and preserved cellular morphology.

A novel approach of detecting corticospinal tract recovery using DTI/DTT analysis, after intra-arterial mesenchymal stem cell infusion in a canine stroke model

Developing valid imaging biomarkers of stroke recovery are critical for translational-stroke research. Diffusion-Tensor-Imaging (DTI) assesses white matter microstructure in the brain and Diffusion-Tensor-tractography (DTT) for visual mapping of CST. Our data suggests a possible correlation between neurological recovery and the improvement in DTI/DTT. The purpose of this pilot-study was to implement/compare MRI stroke vol and DTI/DTT biomarkers of neurological-recovery in a canine stroke model over one month after ipsilateral intra-arterial (IA) Mesenchymal Stem Cell (MSC) infusion vs control. five Female Mongrel-Hound(n:3 MSCs, n:2 control saline only, aged 12-36-months). Reversible MCA-stroke was induced using a detachable-coil(2x8mm) over 60 min, permanent ACA occlusion(2 × 4 mm-coil). MSC (40-80 million/240 cc) or saline/240 cc were infused IA, 48 h post-stroke. Brain-MRIs were performed prior to IA infusion/post stroke, and 15th-30th-days post-stroke. DTT of the CST was generated. Weekly neurological score-evaluations were performed. We observed a significant decreased of stroke vol and qualitative increase in CST-caliber on the treated group, not seen in controls. Also, a faster neuro-recovery was seen in the treated group at the 1st week not seen in the control group. It is important to mentioned that all dogs achieved recovery by 30 days close to baseline, but the difference was noticed at the speed of recovery seen on the treated-group. DTT imaging post IA-MSC therapy showed an increase of CST-caliber correlating with motor-recovery. These findings could support further development of DTI-DTT biomarkers to measure neurological-recovery in experimental models as well as in clinical-trials of stroke-therapies.

Novel canine stroke models using reversible MCA-occlusion alone vs RMCAO plus permanent ACA-occlusion to determine reproducibility and its potential use for translation stroke therapies

The Stroke Treatment Academic Industry Roundtable (STAIR) is in the need of translation stroke models to test novel stroke therapies. Our pilot study established a novel endovascular MCAo/ACAo model, that can mimic a stroke in humans. A total of nine mongrel-hound (n=5 rMCAo, n=4 rMCAo + pACAo, age 12-36 months; BW 22±5 kg), underwent trans-femoral endovascular-catheterization of the MCA-alone or MCA+ACA with a single soft platinum-detachable coil embolization (2x8 mm for MCA, 2x4 mm for ACA). Total occlusion-time MCA: 60 min. MCA-recanalization established by coil-retraction. The dogs were survived for 30 days. Weekly neurological-scoring were performed. Brain-MR-MRA at 2nd, 15th, 30th-days for stroke-volumes and Diffusion Tensor imaging analysis of the CST. Successful MCAo-recanalization was achieved in 8/9, 1-dog from the rMCAo/ACA-group died. We achieved reproducible stroke volume and significant neuro deficits at rMCAo+pACAo group, not the case for rMCAo alone. Avg-stroke vol for group rMCAo/pACAo:15.2 cc(+/-2.9 cc) and rMCAo: 4.5cc (+/-5.5 cc), We observed 88,8% feasibility on achieving rMCAo/ACAo. DTT/CST correlated with the stroke vol and neuro/deficits. In our prior rMCAo model we were not able to achieved significant reproducibility in the stroke vol, also the time of rMCAo needed to achieved a neuro-deficit avg120 min. With this new occlusion model, a 60 min is enough to achieved a stroke vol size that reproduce a neuro-deficit that can be correlated with the one seen in humans. We report a successful reproducible stroke model by anterior circulation approach for future stroke translational research.

Development of a Novel Canine Model of Ischemic Stroke: Skull Base Approach with Transient Middle Cerebral Artery Occlusion

Although canine stroke models have several intrinsic advantages, establishing consistent and reproducible territorial stroke in these models has been challenging because of the abundance of collateral circulation. We have described a skull-base surgical approach that yields reproducible stroke volumes. Ten male beagles were studied. In all 10 dogs, a craniectomy was performed to expose the circle of Willis. Cerebral aneurysm clips were temporarily applied to the middle cerebral artery (MCA), anterior cerebral artery (ACA), posterior cerebral artery, and/or ophthalmic artery (OA) for 1 hour, followed by cauterization of the distal MCA pial collateral vessels. Indocyanine green angiography was performed to assess the local blood flow to the intended area of infarction. The dogs' neurologic examination was evaluated, and the stroke burden was quantified using magnetic resonance imaging. High mortality was observed after 1-hour clip occlusion of the posterior cerebral artery, MCA, ACA, and OA (n= 4). Without coagulation of the MCA collateral vessels, 1-hour occlusion of the MCA and/or ACA and OA yielded inconsistent stroke volumes (n= 2). In contrast, after coagulation of the distal MCA pial collateral vessels, 1-hour occlusion of the MCA, ACA, and OA yielded consistent territorial stroke volumes (n= 4; average stroke volume, 9.13 ± 0.90 cm3; no surgical mortalities), with reproducible neurologic deficits. Consistent stroke volumes can be achieved in male beagles using a skull base surgical approach with temporary occlusion of the MCA, ACA, and OA when combined with cauterization of the distal MCA pial collateral vessels.

Magnetic resonance imaging characteristics of ischemic brain infarction over time in a canine stroke model.

This study describes magnetic resonance imaging (MRI) results and changes in lateral ventricular size over time in a canine ischemic stroke model. T1- and T2-weighted (T1W, T2W) imaging and fluid-attenuated inversion recovery (FLAIR) sequence MRI were performed at 3 h and 3, 8, and 35 days after brain infarct induction. Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping were performed at 8 and 35 days. A total of 29 brain lesions were induced successfully in 12 of 14 beagle dogs. At 3 h, T2W and FLAIR detected hyperintense lesions in three randomly selected dogs. On T1W, all lesions appeared hypointense to isointense at 3 h, isointense (18/29) or hypointense (11/29) at 3 days, hypointense to isointense with peripheral hyperintensity (24/26) at 8 days, and hypointense (18/26) at 35 days. Infarcts on DWI/ADC were hypointense to isointense centrally, with the periphery hyperintense/hyperintense (17/26) at 8 days and hypointense/hyperintense (19/26) at 35 days. A marked increase in lateral ventricular size was observed in dogs with cerebral infarcts. In conclusion, T2W and FLAIR were useful for detecting early stage (3 h to 3 days) brain infarction. T1W and DWI were useful for detecting neuronal necrosis and providing supplemental information for phase evaluation.

DTI findings of corticospinal tract recovery after an intra-arterial mesenchymal stem cell infusion in a canine stroke model

DTI findings of corticospinal tract recovery after an intra-arterial mesenchymal stem cell infusion in a canine stroke model

Temporal evolution of the signal intensity of hyper-acute ischemic lesions in a canine stroke model: influence of hyperintense acute reperfusion marker.

To assess the influence of the hyperintense acute reperfusion marker (HARM) on the relative signal intensity (rSI) and apparent diffusion coefficient (ADC) of hyper-acute ischemic lesions in a canine stroke model. Middle cerebral artery occlusion models were established using autologous clot embolization. Diffusion-weighted (DW) and fluid-attenuated inversion recovery (FLAIR) imaging was performed at 1, 2, 3, 4.5 and 6h after embolization. HARM was defined as the delayed enhancement of cerebrospinal fluid on the subsequent FLAIR images after contrast media used. Twenty-four stroke models were successfully established and divided into the HARM (n=16) and No-HARM group (n=8). No significant differences were found in the rSI on DWI (b0 and b1000 map) and relative ADC between the two groups at each time point after embolization (all P>0.05). There were no significant differences in the rSI on FLAIR at 1 and 2h after embolization between the two groups (P>0.05), while the HARM group showed significantly higher rSI on FLAIR than the No-HARM group at 3, 4.5 and 6h after embolization (P=0.044, 0.036 and 0.001, respectively). HARM should be noted during the quantitative analysis of FLAIR images in future clinical practice.

Correlation between Intravoxel Incoherent Motion Magnetic Resonance Imaging Derived Metrics and Serum Soluble CD40 Ligand Level in an Embolic Canine Stroke Model.

ObjectiveTo determine the relationship between intravoxel incoherent motion (IVIM) imaging derived quantitative metrics and serum soluble CD40 ligand (sCD40L) level in an embolic canine stroke model.Materials and MethodsA middle cerebral artery occlusion model was established in 24 beagle dogs. Experimental dogs were divided into low- and high-sCD40L group according to serum sCD40L level at 4.5 hours after establishing the model. IVIM imaging was scanned at 4.5 hours after model establishment using 10 b values ranging from 0 to 900 s/mm2. Quantitative metrics diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f) of ischemic lesions were calculated. Quantitative metrics of ischemic lesions were normalized by contralateral hemisphere using the following formula: normalized D = Dstroke / Dcontralateral. Differences in IVIM metrics between the low- and high-sCD40L groups were compared using t test. Pearson's correlation analyses were performed to determine the relationship between IVIM metrics and serum sCD40L level.ResultsThe high-sCD40L group showed significantly lower f and normalized f values than the low-sCD40L group (f, p < 0.001; normalized f, p < 0.001). There was no significant difference in D*, normalized D*, D, or normalized D value between the two groups (All p > 0.05). Both f and normalized f values were negatively correlated with serum sCD40L level (f, r = −0.789, p < 0.001; normalized f, r = −0.823, p < 0.001). However, serum sCD40L level had no significant correlation with D*, normalized D*, D, or normalized D (All p > 0.05).ConclusionThe f value derived from IVIM imaging was negatively correlated with serum sCD40L level. f value might serve as a potential imaging biomarker to assess the formation of microvascular thrombosis in hyperacute period of ischemic stroke.

Quantitative assessment of hyperacute cerebral infarction with intravoxel incoherent motion MR imaging: Initial experience in a canine stroke model.

To evaluate the feasibility of intravoxel incoherent motion (IVIM) for the measurement of diffusion and perfusion parameters in hyperacute strokes. An embolic ischemic model was established with an autologous thrombus in 20 beagles. IVIM imaging was performed on a 3.0 Tesla platform at 4.5 h and 6 h after embolization. Ten b values from 0 to 900 s/mm2 were fitted with a bi-exponential model to extract perfusion fraction f, diffusion coefficient D, and pseudo-diffusion coefficient D*. Additionally, the apparent diffusion coefficient (ADC) was calculated using the mono-exponential model with all the b values. Statistical analysis was performed using the pairwise Student's t test and Pearson's correlation test. A significant decrease in f and D was observed in the ischemic area when compared with those in the contralateral side at 4.5 h and 6 h after embolization (P < 0.01 for all). No significant difference was observed in D* between the two sides at either time point (P = 0.086 and 0.336, respectively). In the stroke area, f at 6 h was significantly lower than that at 4.5 h (P = 0.016). A significantly positive correlation was detected between ADC and D in both stroke and contralateral sides at 4.5 h and 6 h (P < 0.001 for both). Significant correlation between ADC and f was only observed in the contralateral side at 4.5 h and 6 h (P = 0.019 and 0.021, respectively). IVIM imaging could simultaneously evaluate the diffusion and microvascular perfusion characteristics in hyperacute strokes. 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:550-556.

Large animal canine endovascular ischemic stroke models: A review.

Stroke is one of the leading causes of death and long-term disability worldwide. Recent exciting developments in the field with endovascular treatments have shown excellent outcomes in acute ischemic stroke. Prior to translating these treatments to human populations, a large-animal ischemic stroke model is needed. With the advent of new technologies in digital subtraction angiography, less invasive endovascular stroke models have been developed. Canines have gyrencephalic brain similar to human brain and accessible neurovascular anatomy for stroke model creation. Canine stroke model can be widely utilized to understand the disease process of stroke and to develop novel treatment. Less invasive endovascular internal carotid emboli injection and coil embolization methods can be used to simulate transient or permanent middle cerebral artery occlusion. Major restriction includes the extensive collateral circulation of canine cerebral arteries that can limit the stroke size. Transient internal carotid artery occlusion can decrease collateral circulation and increase stroke size to some degree. Additional method of manipulating the extent of collateral circulation needs to be studied. Other types of canine stroke models, including vertebral artery occlusion and basilar artery occlusion, can also be accomplished by endovascular thrombi injection. We extensively review the literature on endovascular technique of creating canine ischemic stroke models and their application in finding new therapies for ischemic stroke.

High b value DWI in evaluation of the hyperacute cerebral ischemia at 3T: A comparative study in an embolic canine stroke model.

Previous studies have indicated that the temporal change of relative diffusion weighted imaging (rDWI) signal intensity may help to determine the onset time of a stroke. Furthermore, several studies have indicated that high b value DWI offered improved detection rates for hyper-acute ischemic lesions compared with standard b value DWI. However, the temporal changes of the rDWI on high b value DWI remain unclear. Therefore, based on our embolic canine stroke model, we evaluated the temporal evolution of rDWI on high b value DWI, and further compared its diagnostic value in predicting the onset time of ischemic stroke with rDWI on standard b value DWI. Twelve canine MCAO models were established, and DWI was performed at 1, 2, 3, 4, 5 and 6 h after MCAO, with 3 b values of 1,000, 2,000 and 3,000. High b value DWI detected all ischemic lesions after 1 h, while standard b value did not detect the ischemic lesions in one dog at 1 h. With all three of the tested b values, rDWIs increased continuously within 6 h, while relative apparent diffusion coefficient (rADC) values rapidly decreased in 1 h, then became relatively stable. The area under the curve values for rDWI with b value of 1,000, 2,000 and 3,000, in predicting ischemic lesions within 3 h were 0.897, 0.929 and 0.938, while for rADC were 0.645, 0.583 and 0.599, respectively. Therefore, the results indicated that the rDWI was helpful in aging hyper-acute ischemic stroke, while rADC appeared not to be. High b value DWI had a higher detection rate for ischemic lesions and better predictive efficacy in determining the onset time of hyper-acute stroke.

Simple quantitative measurement based on DWI to objectively judge DWI-FLAIR mismatch in a canine stroke model.

Diffusion-weighted imaging (DWI) - fluid attenuated inversion recovery (FLAIR) mismatch was proven useful to time the onset of wake-up stroke; however, identifying the status of FLAIR imaging has been mostly subjective. We aimed to evaluate the value of relative DWI signal intensity (rDWI), and relative apparent diffusion coefficient (rADC) in identifying the FLAIR status in the acute period. Autologous clot was used to embolize left middle cerebral artery in 20 dogs. Magnetic resonance imaging was performed 3-6 hours and 24 hours after embolization. DWI-FLAIR mismatch was defined as hyperintense signal detected on DWI, but not on FLAIR. The mean values of rDWI or rADC of FLAIR- and FLAIR+ lesions were compared and the critical cutoff values of rDWI and rADC for identifying the FLAIR status were determined. Stroke models were successfully established in all animals. DWI+ lesions were found in all 20 dogs from three hours, while FLAIR+ lesions were found in three, 11, 16, 19, and 20 dogs at five time points after embolization, respectively. The mean rDWI values were significantly different between FLAIR- and FLAIR+ lesions (P < 0.001), but rADC values were not (P = 0.73). Using rDWI=1.90 as the threshold value, excellent diagnostic efficacy was achieved (AUC, 0.88; sensitivity, 0.77; specificity, 0.88). However, rADC appeared not useful (AUC, 0.48; sensitivity, 0.52; specificity, 0.58) in identifying the FLAIR status. In our embolic canine stroke model, rDWI was useful to identify FLAIR imaging status in the acute period, while rADC was not.

TU‐EF‐204‐02: Hiigh Quality and Sub‐MSv Cerebral CT Perfusion Imaging

Purpose:CT Perfusion (CTP) imaging is of great importance in acute ischemic stroke management due to its potential to detect hypoperfused yet salvageable tissue and distinguish it from definitely unsalvageable tissue. However, current CTP imaging suffers from poor image quality and high radiation dose (up to 5 mSv). The purpose of this work was to demonstrate that technical innovations such as Prior Image Constrained Compressed Sensing (PICCS) have the potential to address these challenges and achieve high quality and sub‐mSv CTP imaging.Methods:(1) A spatial‐temporal 4D cascaded system model was developed to indentify the bottlenecks in the current CTP technology; (2) A task‐based framework was developed to optimize the CTP system parameters; (3) Guided by (1) and (2), PICCS was customized for the reconstruction of CTP source images. Digital anthropomorphic perfusion phantoms, animal studies, and preliminary human subject studies were used to validate and evaluate the potentials of using these innovations to advance the CTP technology.Results:The 4D cascaded model was validated in both phantom and canine stroke models. Based upon this cascaded model, it has been discovered that, as long as the spatial resolution and noise properties of the 4D source CT images are given, the 3D MTF and NPS of the final CTP maps can be analytically derived for a given set of processing methods and parameters. The cascaded model analysis also identified that the most critical technical factor in CTP is how to acquire and reconstruct high quality source images; it has very little to do with the denoising techniques often used after parametric perfusion calculations. This explained why PICCS resulted in a five‐fold dose reduction or substantial improvement in image quality.Conclusion:Technical innovations generated promising results towards achieving high quality and sub‐mSv CTP imaging for reliable and safe assessment of acute ischemic strokes.K. Li, K. Niu, Y. Wu: Nothing to disclose. G.‐H. Chen: Research funded, GE Healthcare; Research funded, Siemens AX.

Canine model of ischemic stroke with autologous thrombus in three dogs; Magnetic resonance imaging features and histopathological findings

Ischemic stroke is the most common type of stroke in humans. The purpose of this study was to evaluate the diagnostic value of magnetic resonance imaging (MRI) in a canine model of stroke. Ischemic stroke was induced by using prepared autologous thrombus. The dogs were placed in lateral recumbency on the operation table and the cervical area of each dog was sterilized by using alcohol. After making a cervical incision, the common carotid artery and internal carotid artery (a branch of the common carotid artery that supplies an anterior part of the brain) were exposed. A 200 μL injection of the autologous thrombus prepared 24 hr prior to surgery was delivered with a 20 gauge venous catheter through an internal carotid artery. After successful delivery of the autologous thrombus, the venous catheter was removed, and the cervical incision was sutured. Neurologic signs including generalized seizures, tetraparesis, and altered mental status, were observed in all 3 dogs after induction of ischemic stroke and the signs manifested immediately after awakening from anesthesia. T1- and T2-weighted images and fluid-attenuated inversion recovery (FLAIR) images of the brain were acquired 1 day before and 1 day after surgery. On the day following ischemic stroke induction, MRI revealed multifocal lesions in the cerebral cortex and subcortex such as T1 hypointensity, T2 hyperintensity, FLAIR hyperintensity, and diffusion-weighted hyperintensity in all 3 dogs. Upon postmortem examination, ischemic lesions were found to be consistent with the MRI findings and they were unstained with 2% triphenyltetrazolium chloride. Histologic features of the earliest neuronal changes such as cytoplasmic eosinophilia with pyknotic nuclei were identified. Neuropil spongiosis and perivascular cuffing were also prominently observed at the infarcted area. The present study demonstrated the features of MRI and histopathologic findings in canine ischemic stroke models.

An endovascular canine stroke model: middle cerebral artery occlusion with autologous clots followed by ipsilateral internal carotid artery blockade

Stroke is one of the leading causes of death worldwide and the main reason for long-term disability. An appropriate animal model of stroke is urgently required for understanding the exact pathophysiological mechanism of stroke and testing any new therapeutic regimen. Our work aimed to establish a canine stroke model occluding the middle cerebral artery (MCA) and blocking the ipsilateral internal carotid artery (ICA), and to assess the infarct lesions by magnetic resonance imaging. The stroke model was generated by injecting two autologous clots into each MCA, followed by 2-h ipsilateral ICA blockade (ilICAB) using a catheter in 15 healthy adult beagles. Outcome measurements included 24-h and 7-day postocclusion T2-weighted imaging (T2WI)-based infarct volume calculation. In addition, pial collateral score, canine neurobehavioral score and histopathologic results were documented. Out of 15 dogs, 12 with successful MCA occlusion (MCAO) and ilICAB survived 7 days without complications or casualties and MCA were reperfused at 7 days after occlusion. High signal intensity in the basal ganglia and cerebral cortex on T2WI was initially observed in each dog at 6 h after the procedure. The mean percentage hemispherical infarct volume corrected for edema in all dogs on T2WI at 24 h after occlusion was 12.99±1.57%, and the degree of variability was 12.08%. The infarct volumes at 24 h after occlusion correlated with pial collateral scores and canine neurobehavioral scores well. This canine stroke model with combined MCAO and ilICAB reported here were proven to be highly feasible and reproducible.

Dynamic Iterative Reconstruction for Interventional 4-D C-Arm CT Perfusion Imaging

Tissue perfusion measurement using C-arm angiography systems capable of CT-like imaging (C-arm CT) is a novel technique with potentially high benefit for catheter guided treatment of stroke in the interventional suite. However, perfusion C-arm CT (PCCT) is challenging: the slow C-arm rotation speed only allows measuring samples of contrast time attenuation curves (TACs) every 5-6 s if reconstruction algorithms for static data are used. Furthermore, the peak values of the TACs in brain tissue typically lie in a range of 5-30 HU, thus perfusion imaging is very sensitive to noise. We present a dynamic, iterative reconstruction (DIR) approach to reconstruct TACs described by a weighted sum of basis functions. To reduce noise, a regularization technique based on joint bilateral filtering (JBF) is introduced. We evaluated the algorithm with a digital dynamic brain phantom and with data from six canine stroke models. With our dynamic approach, we achieve an average Pearson correlation (PC) of the PCCT canine blood flow maps to co-registered perfusion CT maps of 0.73. This PC is just as high as the PC achieved in a recent PCCT study, which required repeated injections and acquisitions.

In Vivo MR Imaging of Intraarterially Delivered Magnetically Labeled Mesenchymal Stem Cells in a Canine Stroke Model

BackgroundThis study aimed to evaluate the feasibility of intraarterial (IA) delivery and in vivo MR imaging of superparamagnetic iron oxide (SPIO)-labeled mesenchymal stem cells (MSCs) in a canine stroke model.MethodologyMSCs harvested from beagles’ bone marrow were labeled with home-synthesized SPIO. Adult beagle dogs (n = 12) were subjected to left proximal middle cerebral artery (MCA) occlusion by autologous thrombus, followed by two-hour left internal carotid artery (ICA) occlusion with 5 French vertebral catheter. One week later, dogs were classified as three groups before transplantation: group A: complete MCA recanalization, group B: incomplete MCA recanalization, group C: no MCA recanalization. 3×106 labeled-MSCs were delivered through left ICA. Series in vivo MRI images were obtained before cell grafting, one and 24 hours after transplantation and weekly thereafter until four weeks. MRI findings were compared with histological studies at the time point of 24 hours and four weeks.Principal FindingsHome-synthesized SPIO was useful to label MSCs without cell viability compromise. MSCs scattered widely in the left cerebral hemisphere in group A, while fewer grafted cells were observed in group B and no cell was detected in group C at one hour after transplantation. A larger infarction on the day of cell transplantation was associated with more grafted cells in the brain. Grafted MSCs could be tracked effectively by MRI within four weeks and were found in peri-infarction area by Prussian blue staining.ConclusionIt is feasible of IA MSCs transplantation in a canine stroke model. Both the ipsilateral MCA condition and infarction volume before transplantation may affect the amount of grafted cells in target brain. In vivo MR imaging is useful for tracking IA delivered MSCs after SPIO labeling.

Abstract 2818: Safety, Feasibility and Signal of Activity of Intra-carotid Allogenic Mesenchymal Stem Cell therapy in a Large Animal Stoke Model

INTRODUCTION: Promising pre-clinical data shows benefits of intra-carotid allogenic mesenchymal stem cell (MSCs) therapy in ischemic stroke (IS) in small animal stroke models. Intra-carotid (IC) delivery of MSCs may be superior to intravenous (IV) delivery. However, due to the large size (15-50 microns) of MSCs, there is a concern that they may cause microvascular occlusion during IC administration. There is a need for large animal experiments to confirm positive results in small animal models as has been recommended by STAIR and STEPS consortia. HYPOTHESIS: We tested the hypothesis that IC administration of allogeneic mesenchymal stem cells (MSCs) is feasible and safe in a large animal (canine) stroke model.. METHODS: We performed 1-3 hrs of reversible middle cerebral artery occlusion (rMCAo), in10 female mongrel dogs weighing 40-60 lbs, using an endovascular retrievable coil occlusion of the MCA with a transfemoral arterial approach. At 1 - 72 hrs after rMCAo, animals were assigned to the following treatment groups: A. IC saline placebo (saline) or B. IC allogeneic MSCs or C. IV allogeneic MSCs. Primary outcome measures were: development of angiographic occlusion post-IC MSC or saline infusion, change in MRI infarct volume or new ischemic lesions, and neurological deficit score (NDS) at 4 weeks. Dosing of MSCs was based on extrapolated maximum tolerated dose calculated in a rat study of IC MSCs in our laboratory. RESULTS: Successful IC administration of MSCs was possible in all animals assigned to the treatment group. Animals receiving IC MSCs at 1× 10^6 or 10 × 10^6 (n=6) there were no clinical adverse events or neurological worsening during or 4 weeks post treatment. There were no angiographic decreases in flow or occlusions during or after IC MSC delivery. In the two animals with additional TCD monitoring during IC MSC delivery there were no changes in flow velocity or HITS signals indicating emboli. There was no worsening in MRI infarct volume ( Fig 1 .) amongst the IC MSC groups. A dramatic decrease in infarct volume was noted, in 2 animals in the IC MSC group with minimal infarct related atrophy at one month. None of the animals in the IV MSC or IC saline groups (n=2 in each group) showed a significant change in MRI infarct volume, and major infarct related atrophy was noted. CONCLUSION: IC MSC administration in a large animal rMCAo model is feasible &amp; safe. Fig1 : In vivo coronal MRI FLAIR sequences in IC delivery of MSCs in canine stroke model. There is a signal of biologic activity seen with IC MSC delivery. A. Baseline infarct at 48 hours after rMCAo. B. Infarct evolution at 29 days after IC administration of 10×10^6 MSCs.

C-Arm CT Measurement of Cerebral Blood Volume in Ischemic Stroke: An Experimental Study in Canines

CBV is a key parameter in distinguishing penumbra from ischemic core. The purpose of this study was to compare CBV measurements acquired with standard PCT with ones obtained with C-arm CT in a canine stroke model. Under an institutionally approved protocol, unilateral MCA strokes were created in 10 canines. Four hours later, DWI was used to confirm the presence of an infarct. CBV maps acquired with PCT were compared with ones acquired by using C-arm CT. Three experienced observers, blinded to the technique used for acquisition, evaluated the CBV maps. An ischemic stroke was achieved in 9 of the 10 animals. Areas of reduced CBV were detected in 70%-75% of the PCT studies and in 83%-87% of the C-arm CT examinations, with false-positives in 1.7% and 3.3%, respectively. False-negatives were found in 25% of the PCT and 12.2% of the C-arm CT studies. In all studies, there was a significant difference between the absolute CBV values in normal and abnormal tissue (P < .005) and no significant difference between PCT and C-arm CT CBV values in either the normal or the abnormal parenchyma (P > .05). CBV measurements made with C-arm CT compare well with ones made with PCT. While further work is required both to fully validate the technique and to define its ultimate clinical value, it appears that it offers a feasible method for assessing CBV in the angiography suite.