Image-guided 31P magnetic resonance spectroscopy of normal and transplanted human kidneys. Image-guided 31-phosphorus magnetic resonance spectroscopy (MRS) was used to obtain spatially localized 31P ...spectra of good quality from healthy normal human kidneys and from well-functioning renal allografts. A surface coil of 14cm diameter was used for acquiring phosphorus signals solely from a volume-of-interest located within the kidney. To determine the effects of kidney transplantation on renal metabolism, patients with well functioning allografts were studied. Little or no phosphocreatine in all spectra verifies the absence of muscle contamination, and is consistent with proper volume localization. The intensity ratio of phosphomonoesters (PME) to adenosine triphosphate (ATP) resonances in transplanted kidneys (PME/ATP = 1.1 ± 0.4) was slightly elevated (P = 0.2) compared to that of healthy normal kidneys (PME/ATP = 0.8 ± 0.3). The inorganic phosphate (Pi) to ATP ratio was similar in the two groups (Pi/ATP = 1.1 ± 0.1 in transplanted kidneys vs. 1.2 ± 0.6 in normal kidneys). Acid/base status, as evidenced from the chemical shift of Pi, was the same in both normal controls and transplanted kidneys. Despite the practical problems produced by organ depth, respiratory movement, and tissue heterogeneity, these results demonstrate that image-guided 31P MR spectra can reliably be obtained from human kidneys.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Organic cavity polaritons are bosonic quasi-particles that arise from the strong interaction between organic molecular excitons and photons within microcavities. The spectral dispersion of third ...harmonic generation near resonance with the cavity polariton states is studied experimentally via angle-resolved reflected third harmonic generation measurements with several pump wavelengths. In addition, a three-step nonlinear optical transfer matrix model is used to simulate the third harmonic generation using the sum-over-states dispersive nonlinear coefficients, which include hybrid exciton-photon polariton states. The angle-dependent experiment and modeling agree, revealing that the output of third harmonic generation is resonantly enhanced when the third harmonic wavelength is near the upper polariton state. The degree of enhancement is higher on the exciton-like branch of the polariton dispersion. Lower polariton enhanced third harmonic generation is not experimentally observed due to inadequate coupling at the longer wavelength, which is also consistent with the nonlinear transfer matrix modeling. These results indicate that the sum-over-states nonlinear dispersion is descriptive of the process implying that the polariton states are terms in a complete set of states forming the basis for the perturbative calculation of the nonlinear optical response. The results also indicate the possibility of wavelength agile nonlinear optical response by angle-of-incidence tuning.
The goals of this study were to evaluate 31P MR spectroscopic imaging (MRSI) for clinical studies and to survey potentially significant spatial variations of 31P metabolite signals in normal and ...pathological human brains. In normal brains, chemical shifts and metabolite ratios corrected for saturation were similar to previous studies using single-volume localization techniques (n = 10; pH = 7.01 +/- 0.02; PCr/Pi = 2.0 +/- 0.4; PCr/ATP = 1.4 +/- 0.2; ATP/Pi = 1.6 +/- 0.2; PCr/PDE = 0.52 +/- 0.06; PCr/PME = 1.3 +/- 0.2; Mg2+free = 0.26 +/- 0.02 mM.) In 17 pathological case studies, ratios of 31P metabolite signals between the pathological regions and normal-appearing (usually homologous contralateral) regions were obtained. First, in subacute and chronic infarctions (n = 9) decreased Pi (65 +/- 12%), PCr (38 +/- 6%), ATP (55 +/- 6%), PDE (47 +/- 9%), and total 31P metabolite signals (50 +/- 8%) were observed. Second, regions of decreased total 31P metabolite signals were observed in normal pressure hydrocephalus (NPH, n = 2), glioblastoma (n = 2), temporal lobe epilepsy (n = 2), and transient ischemic attacks (TIAs, n = 2). Third, alkalosis was detected in the NPH periventricular tissue, glioblastoma, epilepsy ipsilateral ictal foci, and chronic infarction regions; acidosis was detected in subacute infarction regions. Fourth, in TIAs with no MRI-detected infarction, regions consistent with transient neurological deficits were detected with decreased Pi, ATP, and total 31P metabolite signals. These results demonstrate an advantage of 31P MRSI over single-volume 31P MRS techniques in that metabolite information is derived simultaneously from multiple regions of brain, including those outside the primary pathological region of interest. These preliminary findings also suggest that abnormal metabolite distributions may be detected in regions that appear normal on MR images.
The goals of this study were to determine whether abnormalities in phosphorus metabolism could be noninvasively detected using phosphorus-31 nuclear magnetic resonance spectroscopy in patients with ...dilated cardiomyopathy and left ventricular hypertrophy, and whether these patient groups could be distinguished from each other based on parameters obtained using this technique. Seventeen patients and 14 control subjects were studied using nuclear magnetic resonance spectroscopy. Spectra were obtained from the human heart at rest using 3-dimensional spectroscopic imaging as a localization technique. Data were acquired over an average volume of 48 cc in 26.3 minutes using a 2 tesla imaging and spectroscopy unit. The ratio of phosphocreatine to adenosine triphosphate was 0.89 +/- 0.88 (mean +/- standard error) in normal subjects and did not differ significantly in patients with dilated cardiomyopathy or left ventricular hypertrophy. A prominent peak in the phosphodiester region was seen much more frequently in patients with dilated cardiomyopathy, resulting in significantly higher ratios of phosphodiester to phosphocreatine (1.28 +/- 0.35) and phosphodiester to adenosine triphosphate (0.79 +/- 0.18) in this group compared to normal subjects (0.33 +/- 0.08 and 0.29 +/- 0.08, respectively). However, the various patient groups could not be reliably distinguished from each other based on spectral patterns. These studies demonstrate the feasibility of performing phosphorus-31 nuclear magnetic resonance spectroscopic imaging in patients with myocardial disease. The initial results indicate that, under resting conditions, the ratio of phosphocreatine to adenosine triphosphate is not consistently altered in patients with severe global cardiomyopathies or hypertrophy. Phosphodiesters are elevated in some patients with dilated cardiomyopathy, a finding that may signify abnormal phospholipid metabolism in this condition.
Metabolic differences in the content of N‐acetylaspartate (NAA), creatine (CR), and choline (CH) in cerebral gray and white matter can complicate the interpretation of 1H spectroscopic images. To ...account for these variations, the gray‐and white‐matter content of each voxel must be known. To provide these data, a T1‐based image segmentation scheme was implemented at 4.1 T. The tissue composition of each voxel was determined using the point‐spread function of the spectroscopic imaging acquisition and the segmented anatomical image. Pure gray‐ and white‐matter values for CR/NAA and CH/NAA, and the content of CR, CH, and NAA, were determined using a linear‐regression analysis of 984 voxels acquired from 10 subjects using white‐matter CR as an internal standard. This information was used to establish means and confidence intervals for CR/NAA and CH/NAA from a voxel of arbitrary tissue composition. Using a single‐tailed t test, the extent and locations of the metabolic abnormalities (P < 0.05) in a patient with multiple sclerosis were identified.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This study assesses the utility of a scintigraphic, nongeometric technique for the determination of left ventricular volumes. Accordingly, gated blood pool scintigraphy and cineangiography were ...performed within a 24 hour period in 22 patients. Scintigraphic volume measurements were calculated from individual frames of a modified 35 degrees left anterior oblique projection using an algorithm designed to consider (1) the background-corrected left ventricular activity normalized for activity per milliliter of peripheral venous blood; (2) total study time; (3) number of frames acquired per cardiac cycle; and (4) percent of the cardiac cycle acquired. Angiographic volumes were calculated by the area-length method and the Kennedy regression equation. There was an excellent correlation between scintigraphic and angiographic methods for all volume measurements grouped together (r = 0.985, standard error of the estimate SEE = 14.6 ml) as well as for segregated end-diastolic volumes (r = 0.985, SEE = 16.2 ml) and end-systolic volumes (r = 0.988, SEE = 14.7 ml). Prospective testing of the independent ability of scintigraphy to estimate ventricular volumes was provided for by studying an additional 13 patients, and good agreement was found between scintigraphic and angiographic determinations of left ventricular end-systolic and end-diastolic volumes. Thus, radionuclide techniques, which are independent of geometric assumptions, may be utilized for the quantitation of left ventricular volumes.
Clinical studies using 31P and 1H MRS with a whole body 2.0 T MRI/MRS system are described. In most cases, techniques to quantitate absolute molar concentrations of metabolites in various organs were ...used. In the brain, AIDS, chronic stroke, and white matter lesions were associated with alterations of brain 31P metabolites. Epilepsy was associated with increased pH in the seizure focus. In the heart, dilated cardiomyopathy was associated with increased PDE/ATP while PCr/ATP was unchanged. In the liver, alcoholic hepatitis and cirrhosis were associated with diminished hepatic ATP while alcoholic hepatitis had increased pH and cirrhosis had decreased pH. This allowed differentiation of normal liver, alcoholic hepatitis, and alcoholic cirrhosis without biopsy. In the prostate, malignancy was associated with increased PME/ATP and decreased PCr/ATP. The PME/PCr was greatly increased in malignant prostate with no overlap in normals. Other cancers outside the brain had increased PME and effective treatment was often associated with diminished PME. 1H MRS of the brain was performed using ISIS and outer volume suppression pulses for volume localization. Excellent high resolution 1H water-suppressed spectra were obtained at echo times as short as 30 ms, showing well resolved peaks for lactate, N-acetylaspartate, glutamate, choline, creatinine, and inositol. 1H MRS demonstrated that the uptake of ethanol by the brain was slower than the rise of ethanol in blood. 31P spectroscopic imaging of the brain with resolution of 2.25 x 2.25 x 2.5 cm produced metabolic images and high resolution spectra from desired regions of interest.
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