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Kwiatkowski G, Kozerke S. Quantitative myocardial first-pass perfusion imaging of CO 2 -induced vasodilation in rats. NMR IN BIOMEDICINE 2021; 34:e4593. [PMID: 34337796 DOI: 10.1002/nbm.4593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 07/02/2021] [Accepted: 07/08/2021] [Indexed: 06/13/2023]
Abstract
Inducible hypercapnia is an alternative for increasing the coronary blood flow necessary to facilitate the quantification of myocardial blood flow during hyperemia. The current study aimed to quantify the pharmacokinetic effect of a CO2 gas challenge on myocardial perfusion in rats using high-resolution, first-pass perfusion CMR and compared it with pharmacologically induced hyperemia using regadenoson. A dual-contrast, saturation-recovery, gradient-echo sequence with a Cartesian readout was used on a small-animal 9.4-T scanner; additional cine images during hyperemia/rest were recorded with an ultrashort echo time sequence. The mean myocardial blood flow value at rest was 6.1 ± 1.4 versus 13.9 ± 3.7 and 14.3 ± 4 mL/g/min during vasodilation with hypercapnia and regadenoson, respectively. Accordingly, the myocardial flow reserve value was 2.6 ± 1.1 for the gas challenge and 2.5 ± 1.4 for regadenoson. During hyperemia with both protocols, a significantly increased cardiac output was found. It was concluded that hypercapnia leads to significantly increased coronary flow and yields similar myocardial flow reserves in healthy rats as compared with pharmacological stimulation. Accordingly, inducible hypercapnia can be selected as an alternative stressor in CMR studies of myocardial blood flow in small animals.
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Affiliation(s)
- Grzegorz Kwiatkowski
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
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Kim SG, Harel N, Jin T, Kim T, Lee P, Zhao F. Cerebral blood volume MRI with intravascular superparamagnetic iron oxide nanoparticles. NMR IN BIOMEDICINE 2013; 26. [PMID: 23208650 PMCID: PMC3700592 DOI: 10.1002/nbm.2885] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The cerebral blood volume (CBV) is a crucial physiological indicator of tissue viability and vascular reactivity. Thus, noninvasive CBV mapping has been of great interest. For this, ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, including monocrystalline iron oxide nanoparticles, can be used as long-half-life, intravascular susceptibility agents of CBV MRI measurements. Moreover, CBV-weighted functional MRI (fMRI) with USPIO nanoparticles provides enhanced sensitivity, reduced large vessel contribution and improved spatial specificity relative to conventional blood oxygenation level-dependent fMRI, and measures a single physiological parameter that is easily interpretable. We review the physiochemical and magnetic properties, and pharmacokinetics, of USPIO nanoparticles in brief. We then extensively discuss quantifications of baseline CBV, vessel size index and functional CBV change. We also provide reviews of dose-dependent sensitivity, vascular filter function, specificity, characteristics and impulse response function of CBV fMRI. Examples of CBV fMRI specificity at the laminar and columnar resolution are provided. Finally, we briefly review the application of CBV measurements to functional and pharmacological studies in animals. Overall, the use of USPIO nanoparticles can determine baseline CBV and its changes induced by functional activity and pharmacological interventions.
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Affiliation(s)
- Seong-Gi Kim
- Neuroimaging Laboratory, Department of Radiology, University of Pittsburgh, PA, USA.
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How stereological analysis of vascular morphology can quantify the blood volume fraction as a marker for tumor vasculature: comparison with magnetic resonance imaging. J Cereb Blood Flow Metab 2012; 32:489-501. [PMID: 22068227 PMCID: PMC3293112 DOI: 10.1038/jcbfm.2011.151] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To assess angiogenesis noninvasively in a C6 rat brain tumor model, the rapid-steady-state-T(1) (RSST(1)) magnetic resonance imaging (MRI) method was used for microvascular blood volume fraction (BVf) quantification with a novel contrast agent gadolinium per (3,6 anhydro) α-cyclodextrin (Gd-ACX). In brain tissue contralateral to the tumor, equal BVfs were obtained with Gd-ACX and the clinically approved gadoterate meglumine (Gd-DOTA). Contrary to Gd-DOTA, which leaks out of the tumor vasculature, Gd-ACX was shown to remain vascular in the tumor tissue allowing quantification of the tumor BVf. We sought to confirm the obtained tumor BVf using an independent method: instead of using a 'standard' two-dimensional histologic method, we study here how vascular morphometry combined with a stereological technique can be used for three-dimensional assessment of the vascular volume fraction (V(V)). The V(V) is calculated from the vascular diameter and length density. First, the technique is evaluated on simulated data and the healthy rat brain vasculature and is then applied to the same C6 tumor vasculature previously quantified by RSST(1)-MRI with Gd-ACX. The mean perfused V(V) and the BVf obtained by MRI in tumor regions are practically equal and the technique confirms the spatial heterogeneity revealed by MRI.
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Walker-Samuel S, Orton M, McPhail LD, Boult JKR, Box G, Eccles SA, Robinson SP. Bayesian estimation of changes in transverse relaxation rates. Magn Reson Med 2011; 64:914-21. [PMID: 20806382 DOI: 10.1002/mrm.22478] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Although the biasing of R(2)* estimates by assuming magnitude MR data to be normally distributed has been described, the effect on changes in R(2)* (DeltaR(2)*), such as induced by a paramagnetic contrast agent, has not been reported. In this study, two versions of a novel Bayesian maximum a posteriori approach for estimating DeltaR(2)* are described and evaluated: one that assumes normally distributed data and the other, Rice-distributed data. The approach enables the robust, voxelwise determination of the uncertainty in DeltaR(2)* estimates and provides a useful statistical framework for quantifying the probability that a pixel has been significantly enhanced. This technique was evaluated in vivo, using ultrasmall superparamagnetic iron oxide particles in orthotopic murine prostate tumors. It is shown that assuming magnitude data to be normally distributed causes DeltaR(2)* to be underestimated when signal-to-noise ratio is modest. However, the biasing effect is less than is found in R(2)* estimates, implying that the simplifying assumption of normally distributed noise is more justifiable when evaluating DeltaR(2)* compared with when evaluating precontrast R(2)* values.
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Affiliation(s)
- Simon Walker-Samuel
- Cancer Research UK & EPSRC Cancer Imaging Centre, The Institute of Cancer Research, Sutton, Surrey, United Kingdom.
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Rioja E, McDonell WN, Kerr CL, Dobson H, Konyer NB, Poma R, Chalmers HJ, Noseworthy MD. Effects of hypercapnia, hypocapnia, and hyperoxemia on brain morphometrics determined by use of T1-weighted magnetic resonance imaging in isoflurane-anesthetized dogs. Am J Vet Res 2010; 71:1011-8. [PMID: 20807139 DOI: 10.2460/ajvr.71.9.1011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate the effects of various combinations of PaCO2 and PaO2 values on brain morphometrics. ANIMALS 6 healthy adult dogs. PROCEDURES A modified Latin square design for randomization was used. Dogs were anesthetized with propofol (6 to 8 mg/kg, IV), and anesthesia was maintained with isoflurane (1.7%) and atracurium (0.2 mg/kg, IV, q 30 min). Three targeted values of PaCO2 (20, 40, and 80 mm Hg) and 2 values of PaO2 (100 and 500 mm Hg) were achieved in each dog, yielding 6 combinations during a single magnetic resonance (MR) imaging session. When the endpoints were reached, dogs were given at least 5 minutes for physiologic variables to stabilize before T1-weighted MR images were obtained. Total brain volume (TBV) and lateral ventricular volume (LVV) were calculated from manually drawn contours of areas of interest by use of a software program, with each dog serving as its own control animal. Three blinded investigators subjectively evaluated the lateral ventricular size (LVS) and the cerebral sulci width (CSW). Brain morphometric values were compared among the target blood gas states. RESULTS No significant differences in TBV were found among target states. The LVV was significantly greater during hypocapnia, compared with hypercapnia at the same PaO2 value. With regard to the subjective evaluations, there were no significant differences among evaluators or among combinations of PaO2 and PaCO2 values. CONCLUSIONS AND CLINICAL RELEVANCE The changes observed in LVV during hypocapnia and hypercapnia may serve as a potential confounding factor when neuromorphometric evaluations are performed in anesthetized dogs.
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Affiliation(s)
- Eva Rioja
- Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
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Human Cerebral Blood Volume (CBV) Measured by Dynamic Susceptibility Contrast MRI and 99mTc-RBC SPECT. J Neurosurg Anesthesiol 2008; 20:41-4. [DOI: 10.1097/ana.0b013e31815d4c70] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Perles-Barbacaru AT, Lahrech H. A new Magnetic Resonance Imaging method for mapping the cerebral blood volume fraction: the rapid steady-state T1 method. J Cereb Blood Flow Metab 2007; 27:618-31. [PMID: 16850031 DOI: 10.1038/sj.jcbfm.9600366] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This paper describes a new rapid steady-state T(1) (RSST(1)) method for mapping the cerebral blood volume fraction (CBVf) by magnetic resonance imaging (MRI). The principle is based on a two-compartment model of the brain (intra- and extravascular), and the effects of paramagnetic contrast agents on the intravascular longitudinal relaxation time T(1). Using appropriate parameters, an Inversion-Recovery-Fast-Low-Angle-Shot sequence acts like a low pass T(1) filter, suppressing signals from tissues with T(1)>>TR (TR=repetition time). It was shown in vivo that, exceeding a particular contrast agent dose, the signal reaches its maximum (corresponding to the intravascular equilibrium magnetization), and is maintained for a duration related to the dose. Acquisitions during this steady state divided by an additional measure of the overall (intra- and extravascular) magnetization at thermal equilibrium provides the CBVf. Experiments were performed on healthy rats at 2.35 T using P760 (Gd(3+)-compound from Guerbet Laboratories) and Gd-DOTA. Because of its high longitudinal relaxivity, P760 is more convenient, and was used to show the feasibility of the method. The CBVf in different structures of the rat brain was compared. The average CBVf for the whole brain slice is 3.29%+/-0.69% (n=15). The influence of transendothelial water exchange was quantified and transversal relaxation effects were found negligible in microvasculature. Finally, the sensitivity of the method to CBVf increases under hypercapnia was evaluated (1%/mm Hg PaCO(2)), demonstrating its potential for longitudinal studies and functional MRI. Clinical applications are feasible since equivalent results were obtained with Gd-DOTA.
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Wu EX, Tang H, Jensen JH. Applications of ultrasmall superparamagnetic iron oxide contrast agents in the MR study of animal models. NMR IN BIOMEDICINE 2004; 17:478-483. [PMID: 15526349 DOI: 10.1002/nbm.923] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Ultrasmall superparamagnetic iron oxide nanoparticles have been widely used during the past decade as MR intravascular contrast agents in the study of animal models. Such agents enhance both T1 and T2/T2* relaxation, although for animal studies it is the later type of enhancement that is most commonly exploited. Their strong microscopic intravascular susceptibility effect enables the local blood volume distribution to be mapped in various organs. High spatial resolution and sensitivity can be achieved, because the long half-life of these agents in blood, combined with anesthetization, permits steady-state measurements over extended periods. This capability has been utilized to study the cerebrovascular blood volume distributions and their changes in normal, activated, pathologic and pharmacologically or genetically modified states, particularly in rodent animal models. It has also been applied to study blood volume changes in other tissues, such as the myocardium. The relaxation rate shifts Delta R2 and Delta R2* induced by iron oxide agents may differ depending on certain morphological characteristics of the microvascular network, and sensitive Delta R2 and Delta R2* mapping can potentially provide, in addition to blood volume, measurement of other important microvascular parameters such as blood vessel density and size. This work aims to review the applications of ultrasmall superparamagnetic iron oxide contrast agents in MR animal studies, with an emphasis on the investigation of microvascular parameters.
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Affiliation(s)
- Ed X Wu
- Jockey Club MRI Engineering Center and Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China.
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Adam JF, Elleaume H, Le Duc G, Corde S, Charvet AM, Troprès I, Le Bas JF, Estève F. Absolute cerebral blood volume and blood flow measurements based on synchrotron radiation quantitative computed tomography. J Cereb Blood Flow Metab 2003; 23:499-512. [PMID: 12679727 DOI: 10.1097/01.wcb.0000050063.57184.3c] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Synchrotron radiation computed tomography opens new fields by using monochromatic x-ray beams. This technique allows one to measure in vivo absolute contrast-agent concentrations with high accuracy and precision, and absolute cerebral blood volume or flow can be derived from these measurements using tracer kinetic methods. The authors injected an intravenous bolus of an iodinated contrast agent in healthy rats, and acquired computed tomography images to follow the temporal evolution of the contrast material in the blood circulation. The first image acquired before iodine infusion was subtracted from the others to obtain computed tomography slices expressed in absolute iodine concentrations. Cerebral blood volume and cerebral blood flow maps were obtained after correction for partial volume effects. Mean cerebral blood volume and flow values (n = 7) were 2.1 +/- 0.38 mL/100 g and 129 +/- 18 mL. 100 g-1. min-1 in the parietal cortex; and 1.92 +/- 0.32 mL/100 g and 125 +/- 17 mL. 100 g-1. min-1 in the caudate putamen, respectively. Synchrotron radiation computed tomography has the potential to assess these two brain-perfusion parameters.
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Affiliation(s)
- Jean-François Adam
- Equipe d'Accueil Rayonnement Synchrotron et Recherche Médicale, MRI Department, Centre Hospitalier Universitaire de Grenoble, France
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Broux C, Tropres I, Montigon O, Julien C, Decorps M, Payen JF. The effects of sustained hyperventilation on regional cerebral blood volume in thiopental-anesthetized rats. Anesth Analg 2002; 95:1746-51, table of contents. [PMID: 12456451 DOI: 10.1097/00000539-200212000-00051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
UNLABELLED Sustained hyperventilation has a time-limited effect on cerebrovascular dynamics. We investigated whether this effect was similar among brain regions by measuring regional cerebral blood volume (CBV) with steady-state susceptibility contrast magnetic resonance imaging during 3 h of hyperventilation. Regional CBV was determined in nine thiopental-anesthetized, mechanically-ventilated rats every 30 min in the dorsoparietal neocortex, the corpus striatum, and the cerebellum. The corpus striatum was the only brain region showing a stable reduction in CBV during the hypocapnic episode (PaCO(2), 24 +/- 3 mm Hg). In contrast, neocortex and, to a lesser extent, cerebellum exhibited a progressive return toward normal values despite continued hypocapnia. No evidence of a rebound in CBV was found on return to normal ventilation in the three brain regions. We conclude that sustained hyperventilation can lead to an uneven change in the reduction of CBV, possibly because of differences of brain vessels in their sensitivity to extracellular pH. Our results in neocortex confirm the transient effect of sustained hyperventilation on cerebral hemodynamics. IMPLICATIONS Sustained hyperventilation has a transient effect in decreasing cerebral blood volume (CBV). Using susceptibility contrast magnetic resonance imaging in thiopental-anesthetized rats, we found differences between brain regions in their transient CBV response to sustained hyperventilation.
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Affiliation(s)
- Christophe Broux
- Department of Anesthesiology, The University of Grenoble School of Medicine, France
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Julien-Dolbec C, Tropres I, Montigon O, Reutenauer H, Ziegler A, Decorps M, Payen JF. Regional response of cerebral blood volume to graded hypoxic hypoxia in rat brain. Br J Anaesth 2002; 89:287-93. [PMID: 12378669 DOI: 10.1093/bja/aef182] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The response of cerebral blood flow to hypoxic hypoxia is usually effected by dilation of cerebral arterioles. However, the resulting changes in cerebral blood volume (CBV) have received little attention. We have determined, using susceptibility contrast magnetic resonance imaging (MRI), changes in regional CBV induced by graded hypoxic hypoxia. METHODS Six anaesthetized rats were subjected to incremental reduction in the fraction of inspired oxygen: 0.35, 0.25, 0.15, and 0.12. At each episode, CBV was determined in five regions of each hemisphere after injection of a contrast agent: superficial and deep neocortex, striatum, corpus callosum and cerebellum. A control group (n = 6 rats) was studied with the same protocol without contrast agent, to determine blood oxygenation level dependent (BOLD) contribution to the MRI changes. RESULTS Each brain region exhibited a significant graded increase in CBV during the two hypoxic episodes: 10-27% of control values at 70% SaO2, and 26-38% at 55% SaO2. There was no difference between regions in their response to hypoxia. The mean CBV of all regions increased from 3.6 (SD 0.6) to 4.1 (0.6) ml (100 g)-1 and to 4.7 (0.7) ml (100 g)-1 during the two hypoxic episodes, respectively (Scheffé F-test; P < 0.01). Over this range, CBV was inversely proportional to SaO2 (r2 = 0.80). In the absence of the contrast agent, changes due to the BOLD effect were negligible. CONCLUSIONS These findings imply that hypoxic hypoxia significantly raises CBV in different brain areas, in proportion to the severity of the insult. These results support the notion that the vasodilatory effect of hypoxia is deleterious in patients with reduced intracranial compliance.
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Affiliation(s)
- C Julien-Dolbec
- INSERM 438 Unit, University of Grenoble School of Medicine, Grenoble, France
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Abstract
Numerous techniques have been proposed in the last 15 years to measure various perfusion-related parameters in the brain. In particular, two approaches have proven extremely successful: injection of paramagnetic contrast agents for measuring cerebral blood volumes (CBV) and arterial spin labeling (ASL) for measuring cerebral blood flows (CBF). This review presents the methodology of the different magnetic resonance imaging (MRI) techniques in use for CBV and CBF measurements and briefly discusses their limitations and potentials.
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Affiliation(s)
- E L Barbier
- Laboratoire mixte INSERM U438, Université Joseph Fourier: RMN Bioclinique, LRC-CEA, Hôpital Albert Michallon, Grenoble, France
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