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M D Schnall

Publications and source records attributed to M D Schnall.

At least 109 records · Page 6Linked to original sources
PubMed1988

Triple nuclear NMR studies of cerebral metabolism during generalized seizure.

Noninvasive NMR spectroscopy of 1H, 31P, and 23Na is performed simultaneously to study brain metabolism during grand mal seizures. Decreases in PCr and increases in lactate associated with seizure as well as an intracellular shift of the Na+ ion pool are demonstrated. A close correlation between the phosphate potential and the intensity of the seizure, as well as the intra/extracellular ionic gradient, is shown.

Adenosine Diphosphate↗
PubMed1988

Concurrent measurements of cerebral blood flow, sodium, lactate, and high-energy phosphate metabolism using 19F, 23Na, 1H, and 31P nuclear magnetic resonance spectroscopy.

A new NMR technique for nondestructive, noninvasive, nonradioactive concurrent measurements of blood flow and several energy-dependent metabolites were applied to in situ cat brain during high cerebral blood flow states (seizures) and low flow states (carotid occlusion plus hemorrhagic shock). An inductively coupled, quadruple-tuned surface coil with a 50-ohm match at all relevant frequencies was used for both excitation and receiving. A broadband spectometer was used to measure the 31P spectrum (PCr, ATP, Pi, and pH), a water-suppressed 1H spectrum (lactate), 23Na, and 19F (blood flow via CHF3 washout). Each nucleus was excited at an independently determined rate. Sodium, with a short T1, was excited more frequently than phosphorus. The results qualitatively agreed with other techniques. Blood flow greatly increased during seizures with a 10% decrease in the Na signal, minimal lactate accumulation, no pH shift, and a change in the PCr-to-Pi ratio from 3.4 to 1.7. During carotid occlusion plus hypotension blood flow, PCr and ATP decreased to less than 10% of baseline values. Changes in PCr and Pi preceded parallel changes in Na and ATP. These experiments demonstrated the feasibility of concurrent measurements of physiologically induced changes in high-energy phosphates, lactate, sodium, and blood flow from the same volume of brain, in a nondestructive manner using NMR spectroscopy.

Adenosine Triphosphate↗
PubMed1988

Intracellular sodium flux and high-energy phosphorus metabolites in ischemic skeletal muscle.

We have employed concurrent 31P- and 23Na-nuclear magnetic resonance (NMR) spectroscopy in conjunction with the paramagnetic shift reagents dysprosium-chelated tripolyphosphate and triethylenetetramine-hexa-acetic acid to observe the intracellular sodium and phosphorus signals in rat leg muscle. With induced ischemia in the leg, we find slowly falling phosphorylation potential. At a critical value of, associated with energetic failure of the Na+-K+ antiport, the intracellular sodium signal begins to increase. We find the following critical values: log, 3.12 +/- 0.32; pH, 6.86 +/- 0.13; Na+ influx with and without ouabain, 5.1 +/- 4.3 and 4.0 +/- 1.3 mol.l-1.h-1, respectively.

Adenine Nucleotides↗
PubMed1988

Metabolic and ionic changes in muscle during hemorrhagic shock.

We have employed concurrent noninvasive 31P and 23Na NMR spectroscopy in conjunction with the paramagnetic shift reagent dysprosium triethylenetetramine hexaacetic acid to observe the intracellular sodium and phosphorus signals in rat leg muscle. Male Wistar rats were bled to a mean arterial blood pressure of 40 mm Hg and were maintained at that pressure. Until decompensatory shock was reached, no increase in intracellular sodium (Nai) was found. Although the high energy storage metabolite phosphocreatine fell with time during shock, ATP did not decrease until decompensation. When the phosphorylation ratio, PR = [ATP]/[ADP][Pi], fell below log(PR) = 3.21 +/- .42, Nai increase commenced at a rate of 7.97 +/- 0.60 meq/l/hr. This corresponds to a two-fold increase in Na permeability compared to normal muscle. A calculation of the free energy available from hydrolysis of ATP at the above value of PR yields -11.7 kcal/mol which is essentially equal to the value of 11.8 kcal/mol which we calculate is needed to run the Na+-K+ antiport through one cycle under normal physiologic conditions.

Adenosine Triphosphate↗
PubMed1987

In vivo 31P NMR spectroscopy of agonist-stimulated phosphatidylinositol metabolism in cat brain.

As a result of the agonist stimulation of muscarinic receptors, myo-inositol-1-phosphate accumulates in the presence of millimolar lithium concentrations. This accumulation of myo-inositol-1-phosphate can be detected by in vivo 31P NMR spectroscopy. Since myo-inositol-1-phosphate is a breakdown product of phosphatidylinositol, this may provide a means of noninvasively monitoring phosphatidylinositol metabolism in vivo.

Animals↗
PubMed1987

Multinuclear MR imaging: a technique for combined anatomic and physiologic studies.

With the use of specially designed multiple-tuned probes for magnetic resonance (MR) imaging, data collection schemes can be developed for obtaining images of different nuclei simultaneously. Both phantom and in vivo MR images of two nuclei (either hydrogen-1, phosphorus-31, lithium-7, or fluorine-19) were obtained in the time span necessary to collect the image of the less sensitive nuclei. This technique offers a means by which physiologic and anatomic information can be gathered in a highly efficient fashion.

Animals↗
PubMed1987

Effects of increased ICP on brain phosphocreatine and lactate determined by simultaneous 1H and 31P NMR spectroscopy.

In order to study the metabolic events surrounding ischemia induced by the graded increase of cerebrospinal fluid (CSF) pressure, the technique of simultaneous phosphorus-31- and hydrogen-1-enhanced nuclear magnetic resonance spectroscopy was applied to five cats as intracranial pressure (ICP) was gradually raised by the instillation of mock CSF. Threshold lactate rose at an average cerebral perfusion pressure (CPP) of 49 torr, and, in general, preceded a threshold decrease in phosphocreatine, which was observed at an average CPP of 29 torr. There was considerable variation among cats in the CPP at which failure of brain energy metabolism occurred, however, suggesting differences in the autoregulatory curves. It is concluded that, with elevated ICP, there is no universally "safe" CPP at which brain energy metabolism may be assumed to be uncompromised.

Animals↗
PubMed1986

Electrical stimulation of human muscle studied using 31P-nuclear magnetic resonance spectroscopy.

This study used phosphorous nuclear magnetic resonance (31P-NMR) spectroscopy to examine the metabolic demand resulting from electrical muscle stimulation (EMS) applied to human skeletal muscle. For each of six subjects, the forearm flexor muscle group was monitored with 31P-NMR during both maximum voluntary and 6-s EMS-induced contractions. A simple protocol using a tourniquet was added in one subject to assess the role of blood flow in this model. Eight hertz (nontetanic) EMS showed less (p less than 0.025) depletion of phosphocreatine (36%) than did tetanic 70-Hz EMS (60%), voluntary isometric (66%), and voluntary isokinetic (68%). The results of the tourniquet studies suggested that the nontetanic EMS allowed relatively increased muscle blood flow and oxygen supply during contraction. Tetanic EMS provided a similar metabolic demand to that of conventional resistive exercise, as measured by 31P-NMR spectroscopy.

Adult↗
PubMed1986

Acute intestinal ischemia studies by phosphorus nuclear magnetic resonance spectroscopy.

31P nuclear magnetic resonance (NMR) spectroscopy has been used to follow the metabolism of acutely ischemic rat small intestine and its recovery after reversal of ischemia. Loops of small intestine were subjected to occlusive external pressure for up to 60 minutes, followed by a recovery period. The depletion of PCr and ATP is rapid and complete within 20 minutes. Recovery from ischemia is also rapid but with recovery ATP levels lower than initial values after prolonged ischemic periods. Intestinal shock was avoided. Clinical recovery correlated with shorter ischemic periods. 31P NMR spectroscopy thus appears to be a suitable technique for studying the effects of pharmacological agents and other treatments for amelioration of ischemic effects on the bowel.

Adenine Nucleotides↗
PubMedDate not supplied

MR imaging of the pelvis with an endorectal-external multicoil array.

Magnetic resonance (MR) images of the pelvis obtained with an endorectal coil have improved resolution relative to that of body coil images; however, they have limited spatial coverage. The sensitivity profile can be improved by using the endorectal coil combined with an external anterior coil as part of a multicoil array. If each coil is connected to a separate receiver, the individual images can be combined to provide an optimal signal-to-noise ratio (S/N). The authors have investigated a 5-inch (12.7-cm) surface coil or a two-coil array as the anterior coil. In both of these configurations, the S/N is improved relative to that of the endorectal coil alone at distances greater than 3 cm from the endorectal coil. The anterior two-coil array provides more lateral coverage. The improved spatial coverage available with this technique expands potential clinical applications of endorectal MR imaging.

Female↗
PubMedDate not supplied

Mucinous carcinomas involving the prostate: atypical findings at MR imaging.

The magnetic resonance (MR) imaging findings in four patients with mucinous tumors involving the prostate are presented. The MR appearance of these tumors differed from that of typical prostatic adenocarcinomas in that the signal intensity on T2-weighted images approximated or exceeded that of the uninvolved peripheral zone. The unusual appearance of mucinous prostate tumors may present problems in diagnosis and staging with MR imaging.

Adenocarcinoma, Mucinous↗
PubMedDate not supplied

Conventional and fast spin-echo MR imaging: minimizing echo time.

Magnetic resonance imaging is frequently complicated by the presence of motion and susceptibility gradients. Also, some biologic tissues have short T2s. These problems are particularly troublesome in fast spin-echo (FSE) imaging, in which T2 decay and motion between echoes result in image blurring and ghost artifacts. The authors reduced TE in conventional spin-echo (SE) imaging to 5 msec and echo spacing (E-space) in FSE imaging to 6 msec. All magnetic gradients (except readout) were kept at a maximum, with data sampling as fast as 125 kHz and only ramp waveforms used. Truncated sinc radio-frequency pulses and asymmetric echo sampling were also used in SE imaging. Short TE (5.8 msec) SE images of the upper abdomen were compared with conventional SE images (TE = 11 msec). Also, FSE images with short E-space were compared with conventional FSE images in multiple body sites. Short TE significantly improved the liver-spleen contrast-to-total noise ratio (C/N) (7.9 vs 4.1, n = 9, P < .01) on T1-weighted SE images, reduced the intensity of ghost artifacts (by 34%, P < .02), and increased the number of available imaging planes by 30%. It also improved delineation of cranial nerves and reduced susceptibility artifacts. On short E-space FSE images, spine, lung, upper abdomen, and musculoskeletal tissues appeared crisper and measured spleen-liver C/N increased significantly (6.9 vs 4.0, n = 12, P < .01). The delineation of tissues with short T2 (eg, cartilage) and motion artifact suppression were also improved. Short TE methods can improve image quality in both SE and FSE imaging and merit further clinical evaluation.

Abdomen↗
PubMedDate not supplied

Magnetization transfer imaging with pulsed off-resonance saturation: variation in contrast with saturation duty cycle.

Magnetization transfer contrast (MTC) can be generated in magnetic resonance images of water-containing macromolecular structures. Results obtained with the pulsed off-resonance saturation technique for achieving MTC are presented, allowing comparison of this technique with others. The magnetization transfer effect is demonstrated in newborn piglet brain and bovine muscle tissue, as well as in human subjects. MTC increases nonlinearly with the duty cycle of the off-resonance irradiation, approaching a maximum value corresponding to continuous irradiation. However, approximately half of the available contrast can be obtained at a given saturation offset frequency, with 16% irradiation duty cycle. Examples of MTC in various human tissues demonstrate the specificity of this technique at power levels within U.S. Food and Drug Administration guidelines. Plots of MTC versus the irradiation offset frequency demonstrate the effects of magnetization transfer and are compared with the curve generated by a control phantom that does not show magnetization transfer. Magnetization transfer imaging with pulsed off-resonance saturation is effective and easily implemented and may be useful in the investigation of saturation transfer phenomena in tissue.

Animals↗
PubMedDate not supplied

MR imaging of pelvic lymph nodes in primary pelvic carcinoma with ultrasmall superparamagnetic iron oxide (Combidex): preliminary observations.

The potential of ultrasmall superparamagnetic iron oxide (Combidex)-enhanced MRI of pelvic lymph nodes in patients with primary pelvic carcinoma is evaluated. Fifteen histologically classified lymph nodes in six patients with known primary pelvic cancer (four prostate; one rectum; one uterus) were evaluated with T2-weighted fast spin-echo (FSE) and T2*-weighted gradient-echo (GRE) MRI at 1.5T 12 to 48 hours after intravenous administration of Combidex at a dose of 1.7 mg Fe/kg. Quantitative image evaluation was performed by comparing signal intensity of individual nodes on pre- and postcontrast images. All patients proceeded to pelvic lymph-node biopsy or surgical dissection, where six were found to be benign and nine were malignant. Of the 15 lymph nodes, four nodes showed a decrease in signal intensity. Of these, three, in which signal loss was homogenous were benign, and one, in which the signal-intensity decrease was heterogeneous, was malignant (micrometastases). No signal change was noted in 11 of 15 lymph nodes of which three were benign (inflammatory) and eight were malignant. Combidex is a promising MR contrast agent for evaluating pelvic lymph nodes. Our preliminary observations suggest that the agent is most useful for classifying normal lymph nodes.

Adult↗
PubMedDate not supplied

Proton T1rho-dispersion imaging of rodent brain at 1.9 T.

Detection of H2(17)O with proton T1rho-dispersion imaging holds promise as a means of quantifying metabolism and blood flow with MRI. However, this technique requires a priori knowledge of the intrinsic T1rho dispersion of tissue. To investigate these properties, we implemented a T1rho imaging sequence on a 1.9-T Signa GE scanner. A series of T1rho images for different locking frequencies and locking durations were obtained from rat brain in vivo and compared with 5% (wt/vol) gelatin phantoms containing different concentrations of (17)O ranging from .037% (natural abundance) to 2.0 atom%. Results revealed that, although there is considerable T1rho-dispersion in phantoms doped with H2(17)O, the T1rho of rat brain undergoes minimal dispersion for spin-locking frequencies between .2 and 1.5 kHz. A small degree of T1rho dispersion is present below .2 kHz, which we postulate arises from natural-abundance H2(17)O. Moreover, the signal-to-noise ratios of T1rho-weighted images are significantly better than comparable T2-weighted images, allowing for improved visualization of tissue contrast. We have also demonstrated the feasibility of proton T1rho-dispersion imaging for detecting intravenous H2(17)O on a live mouse brain. The potential application of this technique to study brain perfusion is discussed.

Animals↗
PubMedDate not supplied

Metastatic thyroid carcinoma presenting as an expansile intraluminal esophageal mass.

We report a patient with metastatic thyroid carcinoma invading the esophagus in whom barium and MR examinations revealed an expansile intraluminal mass indistinguishable from that of a primary esophageal malignancy. Metastatic thyroid carcinoma should therefore be included in the differential diagnosis of an expansile esophageal mass. As in our patient, MR imaging may be useful for showing that the mass originates in the thyroid gland.

Aged↗
PubMedDate not supplied

MR examination for spinal cord compression: impact of a multicoil system on length of study.

Twenty spinal studies to rule out cord compression using a multicoil array system were compared with the 20 consecutive previous studies in which a 5 x 11 inch flat plate coil (5 x 11 FPC) was used on the same 1.5 T MR scanner. The multicoil studies averaged 53 min shorter overall (105 min with the 5 x 11 FPC versus 52 min with multicoil). The reduction in scan time was maximal in studies when Gd-DTPA was administered (76 min reduction) or when the results showed noncompressive epidural disease or intramedullary disease (78 min). Scan quality was diagnostic in all examinations, and lesion localization was superior with the multicoil. The multicoil system substantially reduces scan times when whole spine studies are performed.

Adult↗