Arterial Blood Water Research Articles

NEED OF THE HOUR TO USE MR PERFUSION TO DIFFERENTIATE BETWEEN RADIATION NECROSIS AND TUMOUR RECURRENCE IN KNOWN GLIOMA PATIENTS

Conventional MR imaging may be non-specific in diagnosing low-grade gliomas. Better modalities are used nowadays including MRS (spectroscopy), perfusion, and diffusion-weighted imaging (1).
 MR perfusion is better than CT perfusion in various aspects. MR perfusion does not expose the patient to ionizing radiation. CT perfusion, on the other hand, can be harmful if the patient receives repeated doses. However, CT perfusion may be more readily available in emergency settings and can be quicker to perform than MR perfusion, which requires a longer acquisition time. CT perfusion can also provide more precise measurements of blood flow in small vessels than MR perfusion. Ultimately, the choice between MR perfusion and CT perfusion depends on the specific clinical situation and the preferences of the medical team.
 Perfusion MRI studies have become an increasingly important tool in the management of high-grade gliomas as well. Perfusion MRI allows clinicians to assess the vascularity of these tumors, providing information on tumor grade, response to treatment, and prognosis. Perfusion imaging can be performed using various techniques, including dynamic susceptibility contrast (DSC) MRI and arterial spin labeling (ASL) MRI. DSC-MRI is the most commonly used technique, and it provides information on cerebral blood volume (CBV) and cerebral blood flow (CBF) in the tumor and surrounding tissue. ASL-MRI, on the other hand, measures blood flow by magnetically labeling arterial blood water protons and can provide information on tumor perfusion without the use of contrast agents. Overall, perfusion MRI studies have demonstrated significant potential for improving the diagnosis, management, and prognosis of high-grade gliomas. MR brain perfusion is a type of imaging technique that can be used to differentiate between radiation-related changes and tumor recurrence in patients who have undergone radiation therapy for brain tumors. (2).
 
 Tumor resection followed by chemoradiation remains the current criterion standard treatment for high-grade gliomas. Radiation therapy can cause changes in the brain that may appear similar to tumor recurrence on conventional MRI scans. However, MR brain perfusion can detect differences in blood flow patterns between tumor tissue and normal brain tissue, which can help to differentiate between radiation-related changes/necrosis and tumor recurrence (3).
 Every institute should start using MR perfusion studies to differentiate these. This will eventually help in patient correct diagnosis and reduction in morbidity and mortality.
 Key-words:
 Gliomas, MR Perfusion, CT Perfusion, Tumour Recurrence, Radiation Necrosis.
 
 Conflict of Interest: All authors declare no conflict of interest.
 
 Funding Role: None to declare.
 
 Author Contributions: All authors contributed equally to the drafting of study.
 
 Ethical Statement: Written as per the ethical guidelines of hospital board.
 

Physiologic Effects of Housing Rats in Metabolic Cages.

Currently, metabolic cages (MC) are the only way to achieve serial sampling of urine and feces in rodents. However, the use of this caging creates a dramatic change from an animal's usual microenvironment. Here we sought to examine the effect of MC on physiologic parameters that are stress-responsive in rats. We surgically implanted 8 male Wistar rats (weight, 150 to 175 g) with telemetric transmitters and allowed them to recover for at least 2 wk. At the beginning of the study, the rats were moved to conventional open-top cages, and telemetry recording was initiated. After 24 h, the rats were moved to MC or to another conventional cage and the recording continued for another 24 h. Finally, the rats were returned to their home cages, and telemetry recording was performed for a final 24 h. After 10 days, this process was then repeated, with MC and conventional assignments switched. During the 78-h monitoring period, we recorded heart rate, arterial blood pressure, locomotor activity, body weight, and food and water consumption. Heart rate and arterial blood pressure showed transient but significant changes. Locomotor activity during the dark phase was greatly decreased in MC compared with conventional cages, perhaps due to space constraints. In addition, when the rats were housed in MC, they showed a small but significant weight loss. Food consumption did not differ between housing environments, but water consumption was lower when rats were in MC. In conclusion, the housing of rats in MC for 24 h can elicit mild and reversible cardiovascular changes. This finding is consistent with European Directive 2010/63/EU, which considers short-term (less than 24 h) restraint in MC a procedure of mild severity.

Evaluation of the reproducibility and confounders of fair ASL placenta perfusion measurement in normal pregnancies

Arterial spin labeling (ASL) is a very promising non-invasive MRI technique that quantifies placental perfusion using arterial blood water as an endogenous tracer, but lacks reproducibility and standardization, which limits its use in clinical practice. The objective was to standardize and identify confounders of FAIR ASL in placental perfusion estimation. This was a prospective study at Necker Hospital ( NCT04142606 ). Fetal weight estimation and Doppler measurements were performed, followed by MRI on a 1.5 T scanner. A T2-weighted axial FIESTA placenta-centered slice was performed as a reference. Perfusion data were acquired with a 10 mm axial single slice FAIR-SSFSE, repeated 3 times with variable selective inversion thickness (3, 5 and 7 cm). To assess reproducibility, the sequences were performed twice and perfusion was measured on the whole placenta and in 4 regions of interest (ROI) by two operators. We also studied the impact of maternal age, gestational age at examination or placental location on blood flow measurements. Sixty-two patients with normal pregnancy were included. The respective mean blood flow for the 3, 5 and 7-cm-thick inversion was 238.3 ± 68.0 mL/100 g/min, 156.4 ± 46.5 mL/100 g/min and 121.6 ± 39.7 mL/100 g/min respectively (ANOVA, P < 0.01) this demonstrates the importance of the methodology in this evaluation. The thicker section appeared to be more representative of placental perfusion in agreement with data in the literature. However we did not observe a significant difference when averaging the perfusion of the 4 ROI or the whole placenta ( P = 0.21, P = 0.56 and P = 0.85 respectively). The sequences were repeated twice in 10 patients and were reproducible. There was no significant difference according to maternal age, gestational age at examination and placental location (anterior or posterior). This study evaluated the reproducibility of FAIR ASL for measuring placental perfusion and showed that the selective slab inversion thickness has a significant impact on blood flow measurements. Other potential confounders need to be investigated to enable the application of FAIR ASL in clinical practice. A potential future application of ASL would be to detect placental insufficiency.

Qualitative Assessment of Cerebral Perfusion in Post Stroke Seizure Patients using Arterial Spin Labeling: A Case-control Study

Introduction: Arterial Spin Labeling-Perfusion Weighted Imaging (ASL-PWI) assesses cerebral blood flow using magnetically labeled inflowing arterial blood water protons as freely diffusible tracer without exogenous contrast agent. Seizures are one of the sequelae of stroke with its mechanism not well studied. Aim: Qualitative assessment of cerebral perfusion in post stroke seizure patients using ASL-PWI and comparison of perfusion patterns in post stroke seizure patients and stroke patients. Materials and Methods: This was a case-control study among 100 stroke patients who underwent Magnetic Resonance Imaging (MRI) of brain in Department of Radiodiagnosis, from Outpatient and Inpatient Department of Neurology, Christian Medical College, Ludhiana, Punjab, India, from 1st January 2018 till 1st January 2020. Total 50 post stroke seizure patients included as cases and 50 age matched post stroke patients without seizure included as controls. Perfusion pattern was compared qualitatively using ASL-PWI. Qualitative variables were associated using Chi-square test/Fisher’s-exact test. Results: The mean age of the study subjects were 56.38±16.98 years (age range from 19-87 years) and that of controls were 59.66±11.86 years (age range from 19-89 years) (p-value=0.265). Cerebral hypoperfusion was noted in 39 (78%) of total 50 post stroke seizure patients irrespective of type of stroke. Cortical and subcortical area of frontal and parietal lobes was predominantly involved in post stroke seizure patients. Out of 39, 23 (71.88%) early onset seizure and 16 (88.89%) late onset seizure patients had hypoperfusion. There was no significant association of perfusion abnormality with onset of seizure (p-value=0.241). Hypoperfusion was noted in cases and controls without any statistical difference. Conclusion: Cortical and subcortical area of involvement was noted in post stroke seizure patients. Post stroke seizure patients showed hypoperfusion irrespective of stroke type and onset of seizure. There was no difference seen in perfusion abnormality between post stroke seizure patients and stroke patients without seizure.

Pharmacological MRI with Simultaneous Measurement of Cerebral Perfusion and Blood-Cerebrospinal Fluid Barrier Function using Interleaved Echo-Time Arterial Spin Labelling

Pharmacological MRI (phMRI) studies seek to capture changes in brain haemodynamics in response to a drug. This provides a methodological platform for the evaluation of novel therapeutics, and when applied to disease states, may provide diagnostic or mechanistic information pertaining to common brain disorders such as dementia. Changes to brain perfusion and blood-cerebrospinal fluid barrier (BCSFB) function can be probed, non-invasively, by arterial spin labelling (ASL) and blood-cerebrospinal fluid barrier arterial spin labelling (BCSFB-ASL) MRI respectively. Here, we introduce a method for simultaneous recording of pharmacological perturbation of brain perfusion and BCSFB function using interleaved echo-time ASL, applied to the anesthetized mouse brain. Using this approach, we capture an exclusive decrease in BCSFB-mediated delivery of arterial blood water to ventricular CSF, following anti-diuretic hormone, vasopressin, administration. The commonly used vasodilatory agent, CO2, induced similar increases (~21%) in both cortical perfusion and the BCSFB-ASL signal. Furthermore, we present evidence that caffeine administration triggers a marked decrease in BCSFB-mediated labelled water delivery (41%), with no significant changes in cortical perfusion. Finally, we demonstrate a marked decrease in the functional response of the BCSFB to, vasopressin, in the aged vs adult brain. Together these data, the first of such kind, highlight the value of this translational approach to capture simultaneous and differential pharmacological modulation of vessel tone at the blood brain barrier and BCSFB and how this relationship may be modified in the ageing brain.

Hydrogen Sulfide and the Kidney.

Hydrogen sulfide (H2S) is constitutively synthesized in the kidney. Recent investigations suggest a role for H2S in the regulation of fundamental kidney physiological events including arterial blood flow, glomerular filtration, and electrolyte and water transport. Deficiency of H2S generation has been implicated in acute kidney injury brought on by ischemia, administration of nephrotoxic medications, and obstruction. A role for impaired H2S expression has been shown in chronic kidney injury seen with chronic heart failure, obesity, and diabetes. Deficient H2S generation by the kidney could contribute to blood pressure dysregulation in models of hypertension and preeclampsia. Aging induced chronic kidney impairment is associated with inadequate H2S generation in the kidney. The mechanistic pathways regulated by H2S include but not limited to transcription, mRNA translation, signaling, inflammation, and oxidative stress demonstrating the versatility of the gasotransmitter. In the aforementioned conditions amelioration of kidney injury has been reported by the administration of agents that provide H2S. In renal cancer H2S may participate as an injurious agent. Overall, research on H2S in the kidney is in its early stages, and it is becoming evident that it has a context-dependent nuanced role in various kidney pathologies. There is an urgent need for exploration of H2S in physiology and pathology of the kidney including its role in oxygen sensing and glomerulonephritis. H2S may prove to be a novel therapeutic agent in some kidney disease states.

Reduced oxygen extraction efficiency in sickle cell anemia patients with evidence of cerebral capillary shunting

Arterial spin labeling (ASL) magnetic resonance imaging (MRI) utilizes arterial blood water as an endogenous contrast agent to provide a quantitative measure of cerebral blood flow (CBF). Recently, hyperintense signal within dural venous sinuses in ASL images of sickle cell anemia (SCA) patients has been shown to be consistent with elevated flow velocities and may indicate capillary shunting and reduced oxygen extraction. Here, we performed oxygen extraction fraction (OEF) and CBF measurements in adults (cumulative n = 114) with (n = 69) and without (n = 45) SCA to test the hypothesis that hyperintense venous ASL signal is associated with reduced OEF. Higher categorical scores of shunting on ASL MRI were associated with lower OEF in participants with silent cerebral infarcts or white matter hyperintensities (p = 0.003), but not in those without lesions (p = 0.551). These findings indicate that venous hyperintense signal in ASL images in SCA patients may represent a marker of capillary-level disturbances in oxygen exchange efficiency and small vessel pathology.

Arterial Spin Labeling in Pediatric Neuroimaging

Perfusion imaging using arterial spin labeling noninvasively evaluates cerebral blood flow utilizing arterial blood water as endogenous tracer. It does not require the need of radiotracer or intravenous contrast and offers unique complimentary information in the imaging of pediatric brain. Common clinical applications include neonatal hypoxic ischemic encephalopathy, pediatric stroke and vascular malformations, epilepsy and brain tumors. Future applications may include evaluation of silent ischemia in sickle cell patients, monitor changes in intracranial pressure in hydrocephalus, provide additional insights in nonaccidental trauma and chronic traumatic brain injury (TBI) and in functional Magnetic resonance imaging (MRI). The purpose of this review article is to evaluate the technical considerations including pitfalls, physiological variations, clinical applications and future directions of arterial spin labeling imaging.

On the Validation of a Multiple-Network Poroelastic Model Using Arterial Spin Labeling MRI Data.

The Multiple-Network Poroelastic Theory (MPET) is a numerical model to characterize the transport of multiple fluid networks in the brain, which overcomes the problem of conducting separate analyses on individual fluid compartments and losing the interactions between tissue and fluids, in addition to the interaction between the different fluids themselves. In this paper, the blood perfusion results from MPET modeling are partially validated using cerebral blood flow (CBF) data obtained from arterial spin labeling (ASL) magnetic resonance imaging (MRI), which uses arterial blood water as an endogenous tracer to measure CBF. Two subjects—one healthy control and one patient with unilateral middle cerebral artery (MCA) stenosis are included in the validation test. The comparison shows several similarities between CBF data from ASL and blood perfusion results from MPET modeling, such as higher blood perfusion in the gray matter than in the white matter, higher perfusion in the periventricular region for both the healthy control and the patient, and asymmetric distribution of blood perfusion for the patient. Although the partial validation is mainly conducted in a qualitative way, it is one important step toward the full validation of the MPET model, which has the potential to be used as a testing bed for hypotheses and new theories in neuroscience research.

Preclinical Arterial Spin Labeling Measurement of Cerebral Blood Flow.

Magnetic resonance imaging has been utilized as a quantitative and noninvasive method to image blood flow. Arterial spin labeling (ASL) is an MRI technique that images blood flow using arterial blood water as an endogenous tracer. Herein we describe the use of ASL to measure cerebral blood flow completely noninvasively in rodents, including methods, analysis, and important considerations when utilizing this technique.

Abstract 109: Non-invasive Detection of Capillary Arteriovenous Shunting in Patients With Sickle Cell Anemia

Introduction: High blood velocity can cause rapid erythrocyte transit through capillaries, reducing efficiency of oxygen delivery to tissue (capillary arteriovenous shunting). Arterial spin labeling (ASL) is an MRI technique that utilizes magnetic labeling of arterial blood water for CBF quantitation. Labeled water that traverses capillaries without exchanging with tissue leads to hyperintense venous signal indicative of arteriovenous shunting. We hypothesized that venous hyperintensity is present in sickle cell anemia (SCA) adults, correlates with flow velocity, and corresponds with clinical impairment and oxygen extraction fraction (OEF). Methods: ASL for shunting determination, TRUST for OEF measurement, phase contrast angiography for velocity assessment, and FLAIR / MRA for infarct / vasculopathy evaluation were performed at 3T in adults with SCA (n=36) and age- and race-matched controls (n=11). Three reviewers assessed for hyperintensity in the superior sagittal sinus on ASL images (Fig) and assigned scores of 0 (none), 1 (mild, focal), 2 (significant, focal), or 3 (significant, diffuse). Shunting scores were compared with the presence of clinical impairment (prior infarcts, stenosis&gt;50%, or severe disease requiring transfusions) and OEF. Results: Interobserver agreement was excellent (Fleiss’ κ=0.91). Consensus shunting score in SCA adults (1.2±1.1) was higher (p&lt;0.01) than controls (0.1±0.3), Median age 27.6 y, 57% F. Elevated shunting scores were observed in SCA adults with (1.23±1.07) vs. without (1.07±1.16) clinical impairment. A trend (p=0.068) for elevated OEF was observed in those with shunting scores ≥2 (0.44±0.07) vs. those with shunting scores ≤1 (0.40±0.07). Cervical flow velocity was elevated in subjects with shunting scores ≥2 (30.2±4.8 cm/s) vs. ≤1 (25.3±4.8 cm/s). Conclusion: Venous hyperintensity in ASL images may indicate capillary arteriovenous shunting and may reflect higher clinical impairment and elevated OEF.

In vivo quantification of hyperoxic arterial blood water T1.

Normocapnic hyperoxic and hypercapnic hyperoxic gas challenges are increasingly being used in cerebrovascular reactivity (CVR) and calibrated functional MRI experiments. The longitudinal arterial blood water relaxation time (T1a) change with hyperoxia will influence signal quantification through mechanisms relating to elevated partial pressure of plasma-dissolved O2 (pO2) and increased oxygen bound to hemoglobin in arteries (Ya) and veins (Yv). The dependence of T1a on Ya and Yv has been elegantly characterized ex vivo; however, the combined influence of pO2, Ya and Yv on T1a in vivo under normal ventilation has not been reported. Here, T1a is calculated during hyperoxia in vivo by a heuristic approach that evaluates T1 -dependent arterial spin labeling (ASL) signal changes to varying gas stimuli. Healthy volunteers (n = 14; age, 31.5 ± 7.2 years) were scanned using pseudo-continuous ASL in combination with room air (RA; 21% O2/79% N2), hypercapnic normoxic (HN; 5% CO2/21% O2/74% N2) and hypercapnic hyperoxic (HH; 5% CO2/95% O2) gas administration. HH T1a was calculated by requiring that the HN and HH cerebral blood flow (CBF) change be identical. The HH protocol was then repeated in patients (n = 10; age, 61.4 ± 13.3 years) with intracranial stenosis to assess whether an HH T1a decrease prohibited ASL from being performed in subjects with known delayed blood arrival times. Arterial blood T1a decreased from 1.65 s at baseline to 1.49 ± 0.07 s during HH. In patients, CBF values in the affected flow territory for the HH condition were increased relative to baseline CBF values and were within the physiological range (RA CBF = 36.6 ± 8.2 mL/100 g/min; HH CBF = 45.2 ± 13.9 mL/100 g/min). It can be concluded that hyperoxic (95% O2) 3-T arterial blood T1aHH = 1.49 ± 0.07 s relative to a normoxic T1a of 1.65 s.

A Short Introduction to Arterial Spin Labeling and its Application to Flow Territory Mapping.

Arterial spin labeling (ASL) is an emerging method for the assessment of perfusion in various diseases of the brain. In ASL, the magnetization of arterial blood water spins is manipulated in a complete non-invasive way before flowing into the tissue of interest. This allows absolute quantification of cerebral blood flow, thereby, presenting an alternative to contrast-enhanced methods based on computed tomography or magnetic resonance imaging. Furthermore, its potential application for flow territory mapping can provide additional information of the individual configuration of intracerebral blood flow. This article gives a brief overview of the basic ASL methodology and its approaches to image individual perfusion territories. Additionally, the utilization of ASL in a variety of cerebrovascular diseases is presented to provide examples of potential applications of (territorial) ASL in clinical routine.

How far is arterial spin labeling MRI from a clinical reality? Insights from arterial spin labeling comparative studies in Alzheimer's disease and other neurological disorders.

How far is arterial spin labeling MRI from a clinical reality? Insights from arterial spin labeling comparative studies in Alzheimer's disease and other neurological disorders.

Amygdala on the Lookout.

results present an explanatory challenge: why would the amygdala be hypoactive in paranoid individuals who exhibit heightened threat perception and elevated physiological arousal? To explain this paradoxical finding, some investigators hypothesized that reduced frontal control over the amygdala due to dysconnectivity of frontolimbic circuitry could lead to hypervigilanceand misattribution of fear to incoming signals (3). AnotherpossibilityisthatmethodologicallimitationsofBOLD fMRI have obstructed a more accurate quantification of amygdala activity. In this issue of the Journal, a new study conducted by Pinkham and colleagues (5) offers a methodological explanation for discrepant findings concerning aberrant amygdala activity in paranoid schizophrenia. The authors definitively demonstrate higher baseline amygdala activity in paranoid compared with nonparanoid patients with schizophrenia, by employing arterial spin labeling perfusion MRI. Arterial spin labeling allows for a noninvasive and quantitative measurement of regional cerebral blood flow (CBF) by using magneticallylabeledarterialbloodwaterasanendogenoustracer (asopposedtoexogenousradioactivetracersusedinpositron emission tomography) (6). There are both important methodological and conceptual advances here worthy of note. In addition to arterial spin labeling, the authors acquired BOLD fMRI data while participants rated photographs of faces for trustworthiness. By measuring resting state regional CBF and task-related BOLD activity in the same participants, the authors were able to examine group differences in baseline amygdala activity alongside differences in task-related fluctuations of amygdalaactivity.Suchcomparisonsareparticularlyrelevant to schizophrenia, as prior evidence of amygdala hypoactivation relied on BOLD contrasts blind to potential group differences in baseline activity. Indeed, Pinkham and colleagues found that acutely paranoid patients exhibited higher resting CBF in the bilateral amygdala compared with nonparanoid patients and healthy comparison subjects, who did not differ from each other. On the other hand, the BOLD fMRI task analysis revealed a general trend of amygdala hypoactivation in paranoid compared with nonparanoid participants. Thus, observed taskrelated amygdala hypoactivity likely reflects higher baseline amygdala activity that mitigates the stimulus-driven signal change detected by the BOLD contrast. Additional wholebrain group comparisons found greater CBF in the internal capsule, the corpus callosum, and portions of the inferior temporal and fusiform gyri in paranoid compared with nonparanoid patients. Overall, these results suggest that paranoia

An introduction to ASL labeling techniques

Arterial spin labeling (ASL) methods allow for quantitative mapping of tissue perfusion in absolute units, without the use of contrast agents. In this technique, the magnetization of arterial blood water is labeled by magnetic inversion or saturation, and the delivery of labeled blood water to tissues is observed. In this review three classes of labeling methods for ASL are described and compared: continuous, pulsed, and velocity-selective. The quantification of perfusion from ASL data is discussed, and methods for the extraction of new types of information using ASL and related techniques, such as mapping of vascular territories or venous oxygenation, are described.

Role of renal nerves in the treatment of renovascular hypertensive rats with L-arginine.

The purpose was to determine the role of renal nerves in mediating the effects of antihypertensive treatment with L-arginine in a renovascular hypertension model. The 2K1C (two-kidney one-clip model) hypertensive rats were submitted to bilateral surgical-pharmacological renal denervation. The animals were subdivided into six experimental groups: normotensive control rats (SHAM), 2K1C rats, 2K1C rats treated with L-arginine (2K1C + L-arg), denervated normotensive (DN) rats, denervated 2K1C (2K1C + DN) rats, and denervated 2K1C + L-arg (2K1C + DN + L-arg) rats. Arterial blood pressure, water intake, urine volume, and sodium excretion were measured. The 2K1C rats exhibited an increase in the mean arterial pressure (MAP) (from 106 ± 3 to 183 ± 5.8 mmHg, P < 0.01), whereas L-arg treatment induced a reduction in the MAP (143 ± 3.4 mmHg) without lowering it to the control level. Renal nerve denervation reduced the MAP to normotensive levels in 2K1C rats with or without chronic L-arg treatment. L-arg and denervation induced increases in water intake and urine volume, and L-arg caused a significant natriuretic effect. Our results suggest that renal sympathetic activity participates in the genesis and the maintenance of the hypertension and also demonstrate that treatment with L-arg alone is incapable of normalizing the MAP and that the effect of such treatment is not additive with the effect of kidney denervation.

FMRI: Clinical and Research Applications

Functional Magnetic Resonance Imaging (fMRI) has become the most popular method for assessing major facts of functional brain topography for both research and clinical purposes. fMRI is a powerful non-invasive tool in the study of the function of the brain, used, for example, by psychologists, psychiatrists, neurologists and neuroscientists [2]. fMRI is a technique that uses magnetic resonance imaging to measure brain activity by measuring changes in the local oxygenation of blood, which in turn reflects the amount of local brain activities. While this technique has the advantages of high spatial resolution and non-invasive nature, it has a low temporal resolution respect to other brain imaging techniques. This is because it is not a direct measure; it only measures the secondary physiological correlates of neural activity. fMRI uses the contrast mechanisms which are correlated to physiological changes in local regions of the brain. The first mechanism used for fMRI is Blood Oxygenation Level-Dependent (BOLD) contrast [3] and the second contrast mechanism is the perfusion contrast obtained using Arterial Spin Labeling (ASL). The ASL uses magnetically labeled arterial blood water as a flow tracer [4]. As compared to the BOLD contrast, that is most useful for detecting dynamic changes in brain activity over short time periods (seconds to minutes), ASL is most useful for characterizing resting states, particularly in pathological conditions that affect C erebral Blood Flow (CBF), such as cerebrovascular disease, or for measuring slow variations in CBF or neural activity that occur over long periods. fMRI can give high quality visualization of the location of activity in the brain resulting from motor or sensory stimulation or cognitive functions [5]. It therefore allows the study of how the healthy brain functions is affected by different diseases, how it attempts to recover after damage and how drugs can modulate activity or post-damage recovery and how cognitive states are encoded by the brain activities.

Resting quantitative cerebral blood flow in schizophrenia measured by pulsed arterial spin labeling perfusion MRI

Arterial spin labeling (ASL) perfusion MRI is a relatively novel technique that can allow for quantitative measurement of cerebral blood flow (CBF) by using magnetically labeled arterial blood water as an endogenous tracer. Available data on resting CBF in schizophrenia primarily come from invasive and expensive nuclear medicine techniques that are often limited to small samples and yield mixed results. The noninvasive nature of ASL offers promise for larger-scale studies. The utility of this approach was examined in 24 healthy controls and 30 patients with schizophrenia. Differences between groups in quantitative CBF were assessed, as were relationships between CBF and psychiatric symptoms. Group comparisons demonstrated greater CBF for controls in several regions including bilateral precuneus and middle frontal gyrus. Patients showed increased CBF in left putamen/superior corona radiata and right middle temporal gyrus. For patients, greater severity of negative symptoms was associated with reduced CBF in bilateral superior temporal gyrus, cingulate gyrus, and left middle frontal gyrus. Increased severity of positive symptoms was related to both higher CBF in cingulate gyrus and superior frontal gyrus and decreased CBF in precentral gyrus/middle frontal gyrus. These findings support the feasibility and utility of implementing ASL in schizophrenia research and expand upon previous results.

Effect of chronic central alpha-hANP administration on blood pressure, water and electrolyte balance in rats.

Relatively few studies have evaluated the chronic effects of atrial natriuretic polypeptide (ANP) administration into the central nervous system on peripheral cardiovascular and renal function under conditions of expanded extracellular fluid volume. The present investigation examined the effects of synthetic alpha-human atrial natriuretic polypeptide (alpha-hANP) chronically infused into the cerebroventriculum of rats loaded with 0.9% saline. Measurements of the arterial blood pressure, water and electrolyte balances were carried out during a 4-day central ventricular infusion of alpha-hANP. Significant increases in daily urine volume and urinary sodium and chloride excretion were observed, but no changes of arterial blood pressure occurred. These results indicate that elevated levels of ANP in the CSF can influence sodium and water excretion, but do not appear to influence arterial pressure.