摘要:

AbstractSingle voxel1HH double spin‐echo MR spectroscopy was used to examine 15 cases of brain metastasis of mammary carcinoma (18 lesions) in relation to Gd‐DTPA enhanced MR imaging. For lesions larger than 50% of MRS voxel size, there was significant correlation between Gd‐DTPA‐enhanced MRI signal and MRS‐detected signal of choline (Cho) containing compounds (r= 0.86,P<0.01;n= 8). The observed loss of correlation when including the smaller lesions was overcome by correcting for partial volume effects (r= 0.69,P<0.002;n= 18). Metastasis spectra showed increased Cho compared with control spectra, except for those lesions showing detectable lactate (Lact) signal. The detection of Lact in four of the larger lesions coincided with comparatively low levels of creatine (Cr) and Cho and heterogeneous Gd‐DTPA enhancement (ring‐enhancement). It was concluded that in brain metastases of mammary carcinoma Lact represents a product of ischemia preceding/during tissue decay resulting in central necrosis, rather than tumor specific metabolism resulting in increas

ISSN:0740-3194    

DOI:10.1002/mrm.1910320502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe triple quantum filtered23Na NMR method is applied here to measure the effects of EIPA, a specific inhibitor of the Na+/H+antiporter, on relative intracellular sodium concentrations in isolated working hearts at baseline, during ischemia, and at subsequent reperfusion. In analogy to the spectrophotometric isosbestic point, an approach is developed that defines a value of τ at which the effect of the relaxation times on the TQF signal intensities is minimized, and the signals are proportional to the sodium concentration for both ischemic and working hearts. EIPA at 1.5 μ significantly inhibited (P<0.01) the influx of intracellular Na+during 20 min of ischemia at 36.2°C in this rat heart model. In parallel31P NMR studies, EIPA had no effect on either the development of acidosis during ischemia or on the recovery of pH, during reperfusion despite its profound effect on intracellular Na+influx. Thus, under our conditions the Na+/H+antiporter did not play a critical role in the maintenance of intracellular pH. EIPA treatment resulted in improved recovery (P<0.005) of mechanical function after 20 min of ischemia. [ATP] was higher in treated hearts during ischemia and reperfusi

ISSN:0740-3194    

DOI:10.1002/mrm.1910320503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractUsing a 4.1 T whole body system, we have acquired1H spectroscopic imaging (SI) data of N‐acetyl (NA) compounds, creatine (CR), and choline (CH) with nominal voxel sizes of 0.5 cc (1.15 cc after filtering). We have used the SI data to estimate differences in cerebral metabolites of human gray and white matter. To evaluate the origin of an increased CWNA and CWNA ratios in gray matter relative to white matter, we measured theT1andT2of CR, NA, and CH in gray and white matter using moderate resolution SI imaging. In white matter theT2s of NA, CR, and CH were 233 ± 27,141 ± 18, and 167 ± 20 ms, respectively, and 227 ± 27,140 ± 16, and 189 ± 25 ms in gray matter. The T, values for NA, CR, and CH were 1267 ±141, 1487 ± 146, and 1111 ± 136 ms in gray matter and 1260 ± 154, 1429&233, and 1074 ± 146 ms in white matter. After correcting forT1andT2losses, creatine content was significantly lower in white matter than gray (P

ISSN:0740-3194    

DOI:10.1002/mrm.1910320504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have used a rectangular surface coil and chemical shift imaging to conduct in vivo localized31P NMR metabolic studies in a rat dorsal skin flap model. This approach permits regional comparisons without manipulation of either coil position or subject within the magnet bore. Both the PCr:P1ratio (reflecting ischemia insult) and the PCr:ATP ratio (reflecting phosphagen reserves) decreased as functions of time and distance from the vascular pedicle. The maximum change was nearly 6‐fold for the PCr:P, ratio, and 3‐fold for the PCr:ATP ratio. Signal contamination from subjacent muscle is constant and does not interfere with the metabolic evaluations of skin flaps. This technique may facilitate a better understanding of cutaneous metabolic derangements, such as burns and skin flaps used in reconstructive surgery, as well as studies of pharmacologic regimens developed for their treatment. It also holds potential for application in the study of congenital and neoplastic metabolic disorders of s

ISSN:0740-3194    

DOI:10.1002/mrm.1910320505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTo clarify the result that marked diffusional anisotropy had been found in nonmyelinated nerve, and in completion of an evaluation of the role of all longitudinal axonal structures, we report NMR measurements of water diffusion in the giant axon of the squid, where diffusional anisotropy is determined by the neurofilamentary structure. The diffusion coefficients of water parallel and perpendicular to the long axis of the squid giant axon at 20°C are (1.61 ± 0.06) × 10−5cm2s−1and (1.33 ± 0.09) × 10−5cm2s−1, respectively, which yield an anisotropic diffusion ratio of 1.2 2 0.1. Water diffusion in the squid giant axon is therefore quite rapid and nearly isotropic, thus eliminating the possibility of a significant role for the longitudinally oriented neurofilaments in producing diffusional anisotropy within the axoplasm. In conjunction with our work on garfish nerves therefore, only membranes, either as numerous axonal membranes or as myelin (if present), remain to fulfill the role of the primary determinant of anisotropic water diffusion in nerve and in

ISSN:0740-3194    

DOI:10.1002/mrm.1910320506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe MMQ cell line is a unique prolactin‐secreting rat pituitary cell line. MMQ cells entrapped in agarose gel threads are metabolically active, as determined by the uptake and phosphorylation of creatine and the maintenance of high energy phosphates for over 15 h. Forskolin activates the catalytic subunit of adenylyl cyclase and, in MMQ cells, elevates the level of cAMP and stimulates prolactin secretion.31P NMR spectroscopy was used to investigate the energy metabolism of the MMQ cells during stimulation by forskolin. The ability to measure small changes in the energy status of these cells was enhanced by increasing the PCr levels in the cells. Administration of forskolin to the perifused MMQ cells resulted in acute, reversible, and dose‐dependent changes in the31P NMR spectra of the cells within 12 to 24 min of the beginning of forskolin exposure. Several lines of evidence indicate that the changes observed in the MMQ cells are the composite result of the interaction of forskolin with adenylyl cyclase and the plasma membrane glucose transporter. Also, preincubation of the MMQ cells with the dopamine agonist, bromocriptine, attenuates the forskolin‐stimulated decrease in the PCr resonance by approximately 50%. This attenuation indicates that the forskolin‐stimulated changes in energy metabolism are probably related to the prolactin secretion

ISSN:0740-3194    

DOI:10.1002/mrm.1910320507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractOrientational anisotropy ofT2andT1relaxation times, diffusion, and magnetization transfer has been investigated for six different tissues: tendon, cartilage, kidney, muscle, white matter, and optic nerve. Relaxation anisotropy was observed for tendon and cartilage, and diffusional anisotropy was measured in kidney, muscle, white matter, and optic nerve. All other NMR measurements of these tissues showed no orientational dependence. This pattern of NMR anisotropies can be interpreted from the underlying geometrical structures of the tissues.

ISSN:0740-3194    

DOI:10.1002/mrm.1910320508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper describes a technique for estimation of total (right + left) coronary artery flow using MRI flow measurements in the ascending aorta. The technique is based on the principle that the flow in a vessel branch is equal to the difference of the net flow measured above and below the branch ostia. Aortic net flow is measured at four or more axial oblique slices from below the aortic valve to above the highest location of the coronary vessel ostia in late diastole. A flow model properly interprets the flow measurements in slices that contain the coronary ostia. Results in five normal subjects show that total coronary artery flow can be measured with a standard error of about 90 cc/min, 30% of total coronary artery flow. Potential clinical uses include noninvasive measurement of coronary flow reserve. Pulse sequence improvements are necessary to reduce examination time and improve accuracy and precision.

ISSN:0740-3194    

DOI:10.1002/mrm.1910320509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of gradient system performance on segmentedk‐space gradient echo imaging is presented. Three cases were investigated. First, an ideal system that has infinite slew rates and unlimited maximum gradient strengths was considered. Second, a “high speed” imaging system (2.3 (G/cm), 23 (G/cm)/ms) was considered. These two cases were compared with a “conventional” imaging system (1(G/cm), 1.67 (G/cm)/ms). It was found that substantial increases in SNR can be achieved (≈︁ 45%) by using high speed versus a conventional gradient system, for a TR of 6 ms. For trapezoidal gradient waveforms, there exists an optimum maximum gradient strength for a given slew rate, and any increase in gradient strength above this optimum will not be utilized by an optimized sequence. These studies have shown that increasingTRwithout decreasing the bandwidth is not a good way to increase SNR for const

ISSN:0740-3194    

DOI:10.1002/mrm.1910320510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe enhancement properties of gadobutrol (40 and 80 μmol/kg body weight, 550 daltons), gadolinium‐DTPA‐polylysine (20 μmol/kg body weight, 53,000 daltons) and gadolinium‐DTPA‐cascade‐polymer (20 μmol/kg body weight,<30,000 Daltons) were investigated in abdominal MR imaging using a pig model (n= 24). Signal intensities before and after contrast media application were assessed using a fast single slice FLASH sequence. Measurements were made every 4 s within the first 116 s, every minute between 4 and 10 min and after 15,20,30,40, 50,60,90, and 120 min after contrast media injection. Injection of gadobutrol resulted in typical signal intensity curves characterizing it as an extracellular agent similar to gadopentetate dimeglumine. Significant enhancement was found in all tissues except the trunk muscles when the lower dose was administered. Gadolinium‐DTPA‐polylysine injection resulted also in significant enhancement of the liver, the pancreas, and the renal cortex, but not of the trunk muscle, reflecting its blood pool properties known also from other macromolecular contrast agents. The signal intensity curves obtained after gadolinium‐DTPA‐cascade‐polymer injection were similar to those obtained after polylysine injection, stressing the blood pool character of this new ty

ISSN:0740-3194    

DOI:10.1002/mrm.1910320511

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY