Search PubMed⌕ Search

Biomedical subjects

A Jesmanowicz

Publications and source records attributed to A Jesmanowicz.

At least 55 records · Page 3Linked to original sources
PubMed1987

Evulsion of the retina associated with optic nerve evulsion.

We examined two patients with optic nerve evulsion as well as nasal peripapillary retinal and retinal pigment epithelial evulsion after ocular trauma. Fluorescein angiography demonstrated an intact peripapillary choriocapillaris, loss of peripapillary retina and retinal pigment epithelium, and complete disruption of retinal perfusion. We have postulated a mechanism for traumatic peripapillary retinal evulsion involving severe anterior displacement and abduction of the globe that may explain how the disruptive force was transmitted to the nasal retinal nerve fiber layer. We have provided a clinical correlation with magnetic resonance imaging of the optic nerve and globe of a normal individual.

Adult↗
PubMed1987

Quadrature detection surface coil.

A surface coil assembly consisting of two interleaved coplanar resonators that are intrinsically decoupled from each other is described for imaging at 1.5 T. Vector reception fields on-axis at 3 cm depth are orthogonal and of equal magnitude. Both components of magnetization were received and combined resulting in a 2 1/2 improvement in signal-to-noise for temporomandibular joint images.

Humans↗
PubMed1987

A complication in prescan strategy when using surface coils.

The "prescan" process for setting the gain of an MRI scanner can be confounded by an effect arising from the spatial variation of the angle between the vector reception field of a local or surface coil and the excitation field of a whole-body coil. It is most pronounced when the phase-encoding direction is parallel to the plane of the coil but not along the magnetic field. The largest signal is shown to reside in a data row that is shifted from the one that corresponds to zero phase-encoding gradient. The effect depends on the field-of-view and the dimensions of the receiving coil. Strategies are suggested by which manufacturers of scanners can cope with this intrinsic problem. In the meantime, users of surface coils should be aware of the difficulty.

Magnetic Resonance Imaging↗
PubMed1987

Surface coil for MR imaging of the skin.

A strategy for the design of surface coils for the imaging of extended superficial planar anatomic structures including skin and subcutaneous fat is presented. The central concept is to create an array of closely spaced coplanar radiofrequency current filaments parallel to BO, the polarizing field, with opposite current directions in adjacent filaments. A specific coil design with four such filaments for imaging at 1.5 T is presented. It consists of two pairs of counterrotating current (CRC) coils. Phantom images as well as representative images of normal skin are shown.

Adult↗
PubMed1987

High resolution surface coil magnetic resonance imaging of the joints: anatomic correlation.

Magnetic resonance imaging appears to be a particularly promising approach to the evaluation of articular and periarticular abnormalities. Its ability to produce images in multiple planes directly (without reconstruction) provides a unique advantage over CT for the radiologist when he attempts to interpret the complex three dimensional anatomy of most joints. The inherent contrast resolution of MR is excellent, and with the use of surface coils, spatial resolution is sufficient to permit the identification of the small soft tissue structures in and around joints. Artifacts generated by respiratory and cardiac motion are not a problem in MRI of the joints as they are in MR scanning of the body. Based on all these qualities, we believe that MRI will play an important role in the diagnosis of joint abnormalities.

Ankle Joint↗
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↗
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

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↗