Search PubMed⌕ Search

Biomedical subjects

W Froncisz

Publications and source records attributed to W Froncisz.

At least 37 records · Page 2Linked to original sources
PubMed1987

Enlarged parathyroid glands: high-resolution local coil MR imaging.

Twenty-two patients with primary hyperparathyroidism underwent high-resolution magnetic resonance (MR) imaging with local (surface) coils for preoperative localization of enlarged parathyroid glands. The MR studies were interpreted prospectively and the results compared with findings at surgery and the results of computed tomography (CT), ultrasonography (US), and thallium-technetium scintigraphy (TTS). The sensitivity and specificity of MR imaging were .74 and .88, respectively. The sensitivity/specificity for the other modalities were as follows: 74/.95 for CT, .59/.82 for US, and .82/.98 for TTS. Enlarged parathyroid glands displayed a medium-intensity signal on T1-weighted images and a marked increase in intensity on T2-weighted images, but the degree of increase varied considerably.

Adenoma↗
PubMed1987

Failed temporomandibular joint prostheses: MR imaging.

Magnetic resonance (MR) imaging with surface coils was performed on 43 temporomandibular joints with disk prostheses in 28 patients who had pain, dysfunction, or both after implantation of the prostheses. Fracture was diagnosed prospectively as a discontinuity of the prosthesis on the MR examination; the sensitivity and specificity of MR imaging for this diagnosis was determined on the basis of these studies. All patients underwent surgery, after which the final diagnosis was made. MR imaging was found to have a sensitivity of 0.81 and a specificity of 0.91. Other MR findings included an abnormal amount of soft tissue surrounding the disk, thinning of the disk, osteophytes, and erosion of the condyle. An as yet unexplained artifact was frequently seen and obscured the prostheses in four of the six false-negative studies. The one false-positive case resulted from the interpretation of a markedly thinned but intact region of the prosthesis as a fracture.

Female↗
PubMed1987

MR imaging of the carpal tunnel: normal anatomy and preliminary findings in the carpal tunnel syndrome.

MR imaging was performed through the carpal tunnel in 18 wrists of nine normal volunteers and compared with cryomicrotome sections from cadaver wrists. MR reliably imaged the flexor retinaculum and carpal bones and thus defined the borders of the carpal tunnel. In all cases the median nerve was seen as an ovoid structure of moderate signal intensity and was easily distinguished from the flexor tendons of the hands running in the carpal tunnel. The tendons were separated from each other by their tendon sheaths, and this allowed for identification of the various tendons. Anatomic variations encountered in the normal volunteers included anomalous positioning of the origin of the lumbrical muscles within the carpal tunnel in two, persistent median arteries in two, and interposition of the median nerve between the flexor pollicis longus and the superficial flexor tendon to the index finger in one. Preliminary observations in 10 wrists of patients with carpal tunnel syndrome include segmental and diffuse swelling of the median nerve in six, distortion of the nerve in one, and thickening of the tendon sheaths in one. We conclude that MR imaging accurately and reliably displays the normal anatomy of the carpal tunnel and can detect morphologic changes in patients with carpal tunnel syndrome.

Adult↗
PubMed1987

High-resolution MR imaging of the normal rotator cuff.

The shoulders of six normal volunteers were imaged with high-resolution MR in the axial, sagittal, and coronal planes. An angled pair of counter-rotating current loop-gap resonators designed specifically for the shoulder was used as a local coil. All images were compared with corresponding cryomicrotome sections from cadaver shoulders. The rotator cuff was analyzed in detail. It appeared as a complex, heterogeneous band to tissue superficial to the humeral head. The areas of low signal intensity corresponded to the central tendons of the four rotator cuff muscles. These tendons could be distinguished from each other as well as from the intervening components of the cuff, which have a moderate intensity. We concluded that MR is capable of imaging the normal rotator cuff and of separating the various components. This may allow for improved precision in the diagnosis of rotator cuff disorders.

Adult↗
PubMed1987

MR imaging of the shoulder: diagnosis of rotator cuff tears.

Twenty-five patients with known or suspected tears of the rotator cuff in 26 shoulders underwent MR imaging. All patients also underwent arthrography or surgery. MR visualized abnormalities consistent with a tear in 20 of the 22 tears diagnosed by arthrography or surgery. In most cases, tears were seen as regions of increased signal intensity within the cuff on long-TR pulse sequences, although two cases simply showed an almost complete absence of normal cuff. The MR appearance of the two cases with partial tears was similar to that of full-thickness tears. Of the four cases with normal arthrograms, one case had MR findings consistent with a tear. We conclude that MR has good potential for the noninvasive diagnosis of rotator cuff tears. Its ultimate role in this diagnosis must await prospective studies comparing its accuracy with that of sonography, CT, and arthrography.

Adult↗
PubMed1987

Comparison of high-resolution MRI and SPECT bone scintigraphy for noninvasive imaging of the temporomandibular joint.

Prospective evaluation by magnetic resonance imaging (MRI) and both single photon emission computed tomography (SPECT) and planar bone scintigraphy was undertaken in 31 temporomandibular joints (TMJs) of 21 symptomatic patients. When compared with the results of subsequent arthrography, MRI (0.88) was more sensitive than SPECT (0.76) or planar (0.56) scintigraphy for detection of internal derangement of the TMJ. A diagnostic sensitivity of 0.96 was achieved when the results of either MRI or SPECT was considered evidence of internal joint derangement. Five symptomatic TMJs, clinically thought to be abnormal, were positive on SPECT but showed no evidence of anterior disk displacement at the time of arthrography. In such instances, SPECT may be detecting functionally significant altered joint mechanics that are not evident on anatomic imaging of the TMJ.

Adolescent↗
PubMed1986

The sectorial loop-gap resonator for 31P NMR of the adult human liver at 1.5 T with surface tissue suppression.

A new type of loop-gap resonator, which because of its topology is called a "sectorial resonator," is described in considerable analytical detail. It was used for 31P NMR of the livers of two human adult normal volunteers. An effective strategy for suppression of signals from surface tissue was developed. Depth selection was achieved using a separate excitation coil, permitting a reasonable degree of control of the shape of the sensitive region by adjustment of the dimensions of the excitation coil and of the type of pulse delivered. In addition a new principle for cancellation is described: the topology of the sectorial resonator leads to cancellation signals from tissue masses at the two openings of the structure. Using a phase-alternated repeated 90 degrees FID pulse sequence, good spectra were achieved in 2.5 min that are free from contamination by the phosphocreatine peak.

Adult↗
PubMed1986

1.5 T in vivo 31P NMR spectroscopy of the human liver using a sectorial resonator.

A novel resonator for receiving 31P NMR signals at 1.5 T, which because of its topology has been named a "sectorial resonator," exhibits good radio frequency coupling to the adult human liver. Minimal contamination from nonliver tissue (i.e., muscle) was achieved by the use of depth selective pulses and also because the geometry results in cancellation of signals arising from tissues that are close to the two openings of the structure.

Humans↗
PubMed1986

Counter rotating current local coils for high-resolution magnetic resonance imaging.

A type of local coil (or surface coil) for magnetic resonance imaging and spectroscopy is described in which two circular loops of the same diameter are disposed axially with respect to each other and in which counter rotating currents (CRC) are supported in the two loops. This type of coil has been used for localized reception in a uniform circularly polarized excitation field produced by a whole-body coil of an imager functioning at 1.5 T. The CRC coil is decoupled from the transmitter coil by a combination of intrinsic (or geometrical) isolation (which functions during both excitation and reception) plus passive decoupling (which functions only during excitation). CRC coils of 7.5, 10, 12.5, and 15 cm diameter have been compared on a bench test setup with conventional surface coils of these diameters. Sensitivities are very similar. Q's have been measured as a function of coil diameter and both Q's and frequency shifts have been measured as a function of distance from a saline tank. The CRC coil appears to have advantages with respect to tuning and matching. A high-resolution image of the rotator cuff is shown as an illustration of coil performance.

Biophysical Phenomena↗
PubMed1986

Lateral diffusion of lipid probes in the surface membrane of human platelets. An electron-electron double resonance (ELDOR) study.

Electron-electron double resonance (ELDOR) techniques employing [14N], [15N] 16-Doxylstearate spin-label pairs have been used to measure the lateral diffusion constant, D, of lipids in the surface membrane of intact human blood platelets. For freshly prepared platelets, D is 1.0 X 10(-8) cm2/s at 37 degrees C and for platelets stored for 3 d at room temperature under accepted routine blood bank conditions, D is 2.6 X 10(-8) cm2/s at 37 degrees C. This is the first time that D in the surface membrane of platelets is reported. The marked increase in D for stored platelets may be attributed at least partly to loss of cholesterol during storage, suggesting a correlation between lipid lateral diffusion and cholesterol levels in cell membranes.

Blood Platelets↗
PubMed1986

High-resolution MR imaging using loop-gap resonators. Work in progress.

Representative results using loop-gap resonator (LGR) configurations for local high-resolution MR imaging (0.6 mm X 0.6 mm pixel size with 3-mm section thickness) are presented. Four geometries were employed: flat single loops, coplanar (planar pair) loops, coaxial (axial pair) loops, and symmetrically angled (butterfly pair) loops. The LGRs were used as receiver coils with the body coil as transmitter. Butterfly pairs and planar pairs are intrinsically decoupled from a transmitted field of arbitrary orientation, whereas the single loops and axial pairs are decoupled from a field that is linearly polarized and orthogonal to its axis. The coils were evaluated using computer-generated and experimentally determined field distributions and by the imaging of human subjects on a 1.5-T MR system. Matching the region of sensitivity of the coil to the region of anatomic interest is emphasized.

Image Enhancement↗
PubMed1986

Rotator cuff tears: preliminary application of high-resolution MR imaging with counter rotating current loop-gap resonators.

A new class of radio frequency (RF) coils for magnetic resonance (MR) imaging and spectroscopy is introduced. The coils consist of two loop-gap resonators of equal diameters positioned along a common axis. They are tuned to the mode in which the current in the two loops flows in opposite directions. These coils are "decoupled" from a uniform excitation field of arbitrary orientation (including circularly polarized fields) by intrinsic decoupling and by means of back-to-back fast recovery diodes. Measurements made with the coils and a phantom saline tank indicate that the signal-to-noise ratio obtainable with these coils is almost identical to that obtained with single loops. Imaging of several anatomic areas, including knee, wrist, and shoulder, has been performed with a 1.5-T MR system that uses circularly polarized RF. A small series of patients with torn rotator cuffs underwent imaging. Difficulties in establishing the diagnosis with MR imaging because of anatomic complexity are illustrated. The value of pulse sequences with long repetition times to increase the signal intensity of fluid in the joint is shown.

Humans↗
PubMed1985

Direct evidence of nitrogen coupling in the copper(II) complex of bovine serum albumin by S-band electron spin resonance technique.

ESR spectra of the tight binding Cu(II) complex of bovine serum albumin (BSA) has been studied using S-band. At physiological pH, only one form of copper binding to BSA was detected from the ESR spectra. From previous X-band ESR spectra, nitrogen superhyperfine splittings were observable in the g perpendicular region; however, the resolution of the g parallel region was not sufficient to confirm the exact donor atoms of the complex. Using low-frequency ESR (2-4 GHz) at 77 K, we have resolved the nitrogen superhyperfine structure in the g parallel region. A computer simulation method has been developed for distinguishing between three and four nitrogen donor atoms. The Hyde-Froncisz theory of g and A strain broadening has been modified to use a field-swept calculation for the line shape. The observed intensity pattern and the computer simulation of such spectra positively confirm the structure of Cu(II) ion coordinated to four in-plane nitrogen atoms in frozen aqueous solutions of Cu(II)-BSA complexes at physiological pH. This is the first time that this binding site has been confirmed on the protein instead of a protein fragment or model compound. This work is another example of the usefulness of the S-band ESR technique for characterizing the metal-protein interactions when random variation in g factors cause line broadening in conventional X-band ESR spectra.

Animals↗
PubMed1985

Spin-label oximetry: kinetic study of cell respiration using a rapid-passage T1-sensitive electron spin resonance display.

An unusual ESR display has been developed that exhibits sensitivity to bimolecular collisions of dissolved oxygen in water with nitroxide radical spin probes at oxygen concentrations as low as 0.1 microM, requiring only 1 microliter of sample. The method involves observation of the ESR rapid-passage signal when tuned to the dispersion using a loop-gap resonator. The bimolecular collision rate determines the phase of the signal. The method has been used in a closed-chamber geometry to study respiration of asynchronous populations of Chinese hamster ovary (CHO) cells. An integral of the Michaelis-Menten equation permits direct comparison with experiment and is shown to be incompatible with the data. The theory of diffusion limitation also is developed and shown to be inconsistent with experiment. The average oxygen concentration is found to decrease as Vmaxt, where t is the time after sealing the chamber, to a critical oxygen concentration of 5.2 microM. Below 5.2 microM, the concentration can be fitted to an exponential form, exp(-t/tau), where tau = 15 sec for 4000 cells per microliter. It is believed that this experimental behavior is determined by complex enzyme kinetics.

Animals↗
PubMed1983

Analysis of powder and single crystal electron paramagnetic resonance spectra of deoxy myoglobins containing cobalt (II) proto-and mesoporphyrins IX at various microwave frequencies.

Artificial myoglobins (Mbs) substituted for protoheme with Co(II) proto-and mesoporphyrins IX (proto-and meso-CoMbs, respectively) were prepared. The principal values and eigenvectors of g tensors and the hyperfine coupling tensors of the paramagnetic Co(II) centers of their deoxy forms have been determined by single crystal EPR spectroscopy at 77 K in order to elucidate orientation and electronic structure of the prosthetic group in myoglobin. The orientation of the porphyrin plane of deoxy meso-CoMb were found to be identical to that of deoxy proto-CoMb. However, the in-plane hyperfine coupling constants of deoxy meso-CoMb were more anisotropic and larger than those of deoxy proto-CoMb, suggesting an increase in the electron spin density on the Co(II) ion upon the exchange of protoporphyrin IX with mesoprophyrin IX. Powder EPR spectra of these CoMbs, which were measured at S- and L-band microwave frequencies, exhibited well resolved 59Co hyperfine splittings and can be clearly interpreted by the use of the EPR parameters obtained from single crystal EPR measurements.

Animals↗