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Biomedical subjects

J Mattiello

Publications and source records attributed to J Mattiello.

14 recordsLinked to original sources
PubMed2001

Diffusion-perfusion MRI characterization of post-recanalization hyperperfusion in humans.

BACKGROUND: Animal and human studies have demonstrated that postischemic hyperperfusion may occur both early and late timepoints following acute cerebral ischemia. OBJECTIVE: To use diffusion-perfusion MRI to characterize hyperperfusion in humans following intra-arterial thrombolysis. METHODS: MRI were performed before treatment, several hours following vessel recanalization, and at day 7 in patients successfully recanalized with intra-arterial thrombolytics. RESULTS: Hyperperfusion was visualized in 5 of 12 patients within several hours after recanalization (mean volume, 18 mL; range, 7 to 40 mL), and in 6 of 11 patients at day 7 (mean volume, 28 mL; range, 4 to 45 mL). Within the core region of hyperperfusion, mean cerebral blood flow was 2.1 times greater than in the contralateral homologous region at the early time point, and 3.1 times greater at day 7. Seventy-nine percent of voxels with hyperperfusion at day 7 demonstrated infarction at day 7, whereas only 36% of voxels (within the initial hypoperfusion region) not showing hyperperfusion at day 7 demonstrated infarction at day 7. Mean pretreatment apparent diffusion coefficient (ADC) and perfusion values were more impaired in voxels that subsequently developed hyperperfusion compared with other at-risk voxels (all p values < 0.0001). There were no significant differences in the degree of clinical improvement in patients with regions of hyperperfusion versus those without, although sample size limited power to detect group differences. CONCLUSIONS: Postischemic hyperperfusion, visualized with perfusion MRI in humans following recanalization by intra-arterial thrombolytic therapy, occurred in about 40% of patients within hours and in about 50% of patients at day 7. Hyperperfusion developed mainly in regions that went on to infarction. Compared with other abnormal regions, tissues that developed postischemic hyperperfusion had greater bioenergetic compromise in pretreatment apparent diffusion coefficient values and greater impairment in pretreatment blood flow measures.

Adult↗
PubMed2001

Diffusion-perfusion MR evaluation of perihematomal injury in hyperacute intracerebral hemorrhage.

BACKGROUND: It has been suggested that a zone of perihematomal ischemia analogous to an ischemic penumbra exists in patients with primary intracerebral hemorrhage (ICH). Diffusion-perfusion MRI provides a novel means of assessing injury in perihematomal regions in patients with ICH. OBJECTIVE: To characterize diffusion-perfusion MRI changes in the perihematomal region in patients with hyperacute intracerebral hemorrhage. METHOD: Twelve patients presenting with hyperacute, primary ICH undergoing CT scanning and diffusion-perfusion MRI within 6 hours of symptom onset were reviewed. An automated thresholding technique was used to identify decreased apparent diffusion coefficient (ADC) values in the perihematomal regions. Perfusion maps were examined for regions of relative hypo- or hyperperfusion. RESULTS: Median baseline NIH Stroke Scale score was 17 (range, 6 to 28). Median hematoma volume was 13.3 mL (range, 3.0 to 74.8 mL). MRI detected the hematoma in all patients on echo-planar susceptibility-weighted imaging and in all seven patients imaged with gradient echo sequences. In six patients who underwent perfusion imaging, no focal defects were visualized on perfusion maps in tissues adjacent to the hematoma; however, five of six patients demonstrated diffuse ipsilateral hemispheric hypoperfusion. On diffusion imaging, perihematomal regions of decreased ADC values were identified in three of 12 patients. All three subsequently showed clinical and radiologic deterioration. CONCLUSIONS: A rim of perihematomal decreased ADC values was visualized in the hyperacute period in a subset of patients with ICH. The presence of a rim of decreased ADC outside the hematoma correlated with poor clinical outcome. Although perfusion maps did not demonstrate a focal zone of perihematomal decreased blood flow in any patient, most patients had ipsilateral hemispheric hypoperfusion.

Acute Disease↗
PubMed2000

Functional properties of failing human ventricular myocytes.

Reduced peak systolic Ca2+ and slow decay of the Ca2+ transient are common features of the end-stage failing human ventricular myocyte and are thought to underlie abnormal ventricular contractility in congestive heart failure (CHF). Individual changes in the expression or activity of Ca2+ transport proteins of the sarcoplasmic reticulum (SR Ca2+ ATPase, SERCa) or the sarcolemmal (sodium-calcium exchanger, NCX) have not always been observed in CHF and cannot per se consistently explain these Ca2+ transient defects. We review recent data that suggests that the normal balance of transport activities of SERCa and NCX is deranged in failing human myocytes. We hypothesize that an increase in the NCX/SERCa transport capacity in failing myocytes can explain the abnormal Ca2+ homeostasis of the failing human ventricular myocyte.

Action Potentials↗
PubMed2000

Thrombolytic reversal of acute human cerebral ischemic injury shown by diffusion/perfusion magnetic resonance imaging.

Diffusion magnetic resonance imaging provides an early marker of acute cerebral ischemic injury. Thrombolytic reversal of diffusion abnormalities has not previously been demonstrated in humans. Serial diffusion and perfusion imaging studies were acquired in patients experiencing acute hemispheric cerebral ischemia treated with intra-arterial thrombolytic therapy within 6 hours of symptom onset. Seven patients met inclusion criteria of prethrombolysis and postthrombolysis magnetic resonance studies, presence of large artery anterior circulation occlusion at angiography, and achievement of vessel recanalization. Mean diffusion-weighted imaging lesion volume at baseline was 23 cm3 (95% confidence interval [95% CI], 8-38 cm3) and decreased to 10 cm3 (95% CI, 3-17 cm3) 2.5 to 9.5 hours after thrombolysis. Mean apparent diffusion coefficient lesion volume decreased from 9 cm3 (95% CI, 2-16 cm3) at baseline to 1 cm3 (95% CI, 0.4-2 cm3) early after thrombolysis. A secondary increase in diffusion volumes was seen in 3 of 6 patients at day 7. In all 4 patients in whom perfusion imaging was obtained before and after treatment, complete resolution of the perfusion deficit was shown. Diffusion magnetic resonance signatures of early tissue ischemic injury can be reversed in humans by prompt thrombolytic vessel recanalization. The ischemic penumbra includes not only the region of diffusion/perfusion mismatch, but also portions of the region of initial diffusion abnormality.

Acute Disease↗
PubMed1997

The b matrix in diffusion tensor echo-planar imaging.

In diffusion tensor imaging (DTI) an effective diffusion tensor in each voxel is measured by using a set of diffusion-weighted images (DWIs) in which diffusion gradients are applied in a multiplicity of oblique directions. However, to estimate the diffusion tensor accurately, one must account for the effects of all imaging and diffusion gradient pulses on each signal echo, which are embodied in the b matrix. For DTI to be practical clinically, one must also acquire DWIs rapidly and free of motion artifacts, which is now possible with diffusion-weighted echo-planar imaging (DW-EPI). An analytical expression for the b matrix of a general DW-EPI pulse sequence is presented and then validated experimentally by measuring the diffusion tensor in an isotropic phantom whose diffusivity is already known. The b matrix is written in a convenient tabular form as a sum of individual pair-wise contributions arising from gradient pulses applied along parallel and perpendicular directions. While the contributions from readout and phase-encode gradient pulse trains are predicted to have a negligible effect on the echo, the contributions from other imaging and diffusion gradient pulses applied in both parallel and orthogonal directions are shown to be significant in our sequence. In general, one must understand and account for the multiplicity of interactions between gradient pulses and the echo signal to ensure that diffusion tensor imaging is quantitative.

Algorithms↗
PubMed1996

High temporal resolution diffusion MRI of global cerebral ischemia and reperfusion.

Although brain ischemia has been extensively studied using diffusion-weighted magnetic resonance imaging, most studies performed so far have not had adequate time resolution to follow the temporal changes in the water apparent diffusion coefficient (ADC) in hyperacute ischemia. Using diffusion echo planar imaging, we obtained ADC maps (calculated from measurements made with 8 b-values) with a time resolution of 43 s in a feline model of global brain ischemia and reperfusion. Different protocols were performed: 10-min hypoperfusion, 10- and 22-min ischemia followed by reperfusion, and cardiac arrest. ADC values were obtained from white matter of the internal capsule and from the thalamus. Cortical gray matter measurements were not deemed reliable due to the close proximity of CSF in the cortical sulci. Following occlusion, the ADC declined in the thalamus to < 2 SD of its normal baseline value within 1.5-2.5 min. This decay was exponential with a time constant (tau +/- SD) of 6.0 +/- 2.6 min; no further decrease in the ADC was observed 10 min following ischemia. Following reperfusion, in animals that showed ADC recovery, the ADC began increasing immediately, returning to its preischemic value in approximately 15 min. No significant ADC changes were observed during hypoperfusion. Following cardiac arrest, the decay of ADC was more rapid in the thalamus (tau = 2.6 +/- 0.6 min) than in white matter (tau = 6.6 +/- 1.8 min). We observed that the ADC at 40 min after cardiac arrest was similar to the ADC at 10 min after ischemia. Given that all animals subjected to 10-min ischemic episodes showed ADC recovery with reperfusion, doubt is cast on whether it is possible to define a threshold value of the ADC below which brain tissue is irreversibly damaged. Finally, despite variability in the time constants of the ADC decay induced by ischemia, the ADC values at 10 min were very similar in all the animals. This suggests that when blood flow is diminished sufficiently to induce an ADC reduction, differences in perfusion affect the rapidity of the decrease but not the final asymptotic value reached.

Animals↗
PubMed1994

Estimation of the effective self-diffusion tensor from the NMR spin echo.

The diagonal and off-diagonal elements of the effective self-diffusion tensor, Deff, are related to the echo intensity in an NMR spin-echo experiment. This relationship is used to design experiments from which Deff is estimated. This estimate is validated using isotropic and anisotropic media, i.e., water and skeletal muscle. It is shown that significant errors are made in diffusion NMR spectroscopy and imaging of anisotropic skeletal muscle when off-diagonal elements of Deff are ignored, most notably the loss of information needed to determine fiber orientation. Estimation of Deff provides the theoretical basis for a new MRI modality, diffusion tensor imaging, which provides information about tissue microstructure and its physiologic state not contained in scalar quantities such as T1, T2, proton density, or the scalar apparent diffusion constant.

Animals↗
PubMed1994

MR diffusion tensor spectroscopy and imaging.

This paper describes a new NMR imaging modality--MR diffusion tensor imaging. It consists of estimating an effective diffusion tensor, Deff, within a voxel, and then displaying useful quantities derived from it. We show how the phenomenon of anisotropic diffusion of water (or metabolites) in anisotropic tissues, measured noninvasively by these NMR methods, is exploited to determine fiber tract orientation and mean particle displacements. Once Deff is estimated from a series of NMR pulsed-gradient, spin-echo experiments, a tissue's three orthotropic axes can be determined. They coincide with the eigenvectors of Deff, while the effective diffusivities along these orthotropic directions are the eigenvalues of Deff. Diffusion ellipsoids, constructed in each voxel from Deff, depict both these orthotropic axes and the mean diffusion distances in these directions. Moreover, the three scalar invariants of Deff, which are independent of the tissue's orientation in the laboratory frame of reference, reveal useful information about molecular mobility reflective of local microstructure and anatomy. Inherently tensors (like Deff) describing transport processes in anisotropic media contain new information within a macroscopic voxel that scalars (such as the apparent diffusivity, proton density, T1, and T2) do not.

Animals↗
PubMed1992

Measurement of relative regional tumor blood flow in mice by deuterium NMR imaging.

A noninvasive method to measure relative regional tumor blood flow (rTBF) throughout murine tumors which uses deuterium NMR imaging to observe regional uptake of HOD after bolus iv injection of D2O is introduced. HOD uptake images are formed by subtraction of a background (preinjection) image from 94-s gradient-refocused deuterium NMR images acquired starting 30 s and 10 min after D2O injection. The pixel intensity in the HOD uptake image acquired starting 30 s after injection is directly related to rTBF with a limit of detection estimated at 7 ml/(100 g-min). The image acquired 10 min after D2O injection extends the estimated limit of detection for rTBF to 3 ml/(100 g-min). Heterogeneity in rTBF and regional effects of photodynamic therapy within RIF-1 tumors are readily perceived. This method may provide a valuable tool to further our understanding of the relationship between blood flow and therapeutic response in tumors.

Animals↗
PubMed1991

Relative volume-average murine tumor blood flow measurement via deuterium nuclear magnetic resonance spectroscopy.

A deuterium NMR spectroscopic method to determine relative tumor blood flow (TBF) by measuring the increase in tumor HOD concentration after intravenous injection of 100 microliters D2O (0.9% NaCl) is presented. An integration approach analogous to that validated for positron emission tomographic measurement of cerebral blood flow was implemented. Computer simulations indicated that integration from 30 to 120 s minimizes the sensitivity of the uptake integral to the shape of the arterial input function, which cannot be assessed in each mouse, while maintaining both a nearly linear relationship between TBF and the integral and high NMR signal-to-noise. A strong positive linear correlation was observed between the uptake integral and TBF measured by D2O clearance in both untreated tumors (n = 19; P less than 0.001) and tumors after hyperthermia (n = 16; P less than 0.001). This method can measure relative TBF in tumors with heterogeneous blood flow and is ideally suited to concurrent or interleaved measurement of TBF and metabolism via multinuclear NMR spectroscopy.

Animals↗
PubMed1990

Effect of photodynamic therapy on RIF-1 tumor metabolism and blood flow examined by 31P and 2H NMR spectroscopy.

Photodynamic therapy utilizes the tumor localizing drug dihematoporphyrin ether and red laser light to produce both direct tumor cell destruction via damage to mitochondrial membranes, and also indirect cell kill via destruction of the tumor vasculature. As a first step towards examining the mechanistic relationship between metabolic and vascular effects of photodynamic therapy, murine RIF-1 tumors were treated with a subcurative treatment (500 J/cm2). Tumor metabolic status was monitored using in vivo 31P NMR before, during and after the treatment. The tumor blood flow immediately before and after treatment was measured by direct intratumor injection of D2O saline and observation of the tracer signal clearance from the tumor via 2H NMR. During the photodynamic therapy treatment, significant decreases were observed for the nucleoside triphosphate concentrations, tumor pH and tumor blood flow, while inorganic phosphate concentrations increased. Animals treated with laser light alone and those not given any treatment, demonstrated no significant changes in tumor metabolic status, tumor pH or tumor blood flow. Further studies are required to determine whether tumor blood flow or metabolic status is affected first.

Animals↗
PubMedDate not supplied

On the accuracy of noninvasive thermometry using molecular diffusion magnetic resonance imaging.

Temperature measurement using magnetic resonance imaging (MRI) of water self-diffusion is investigated. Diffusion images and derived temperatures are obtained in polyacrylamide gel phantom. The temperatures measured from MRI are compared with those from temperature probes to verify their accuracy. In general, the difference between temperatures determined from MRI diffusion images over 0.3 cm3 regions of interest and from temperature probes were 0.2 degrees C. It is concluded that current MRI technology allows noninvasive temperature tomography that is comparable with invasive thermometry with respect to temperature accuracy, has spatial and time resolutions that would be useful in hyperthermic oncology.

Body Temperature↗