Leon Kaufman

Method and apparatus for selective adjustment of rf coil size for magnetic resonance imaging

A bridge conductors for the turns of an MRI RF coil may be connected serially within a connector joint area of an inductive coil so as to selectively increase its physical size (e.g., so as to accommodate larger patient volumes to imaged therewithin). Serial capacitance may be included in at least one of the bridging conductors so as to substantially reduce the net inductive impedance of the added bridge conductors such that the standard coil RF tuning and impedance matching circuits may still operate within their normal predetermined adjustable ranges.

MRI compensated for spurious NMR frequency/phase shifts caused by spurious changes in magnetic fields during NMR data measurement processes

At least one extra NMR measurement cycle is performed without any imposed magnetic gradients during readout and recordation of the NMR RF response. Calibration data derived from this extra measurement cycle or cycles can be used for resetting the RF transmitter frequency and/or for phase shifting other conventionally acquired NMR RF response data to compensate for spurious changes in magnetic fields experienced during the NMR data measuring processes. Some such spurious fields may be due to drifting of the nominally static magnetic field. Another source of spurious fields are due to remnant eddy currents induced in surrounding conductive structures by magnetic gradient pulses employed prior to the occurrence of the NMR RF response signal. Special procedures can be employed to permit the compensation data itself to be substantially unaffected by relatively static inhomogeneities in the magnetic field and/or by differences in NMR spectra of fat and water types of nuclei in imaged volumes containing both.

Switchable MRI RF coil array with individual coils having different and overlapping fields of view

An array of plural magnetic resonance imaging (MRI) RF coils is provided having different and overlapping fields of view. Controllable switches are connected with each individual coil of the array and are capable of selectively conditioning any one of the coils for individual usage in an MRI procedure. Either mechanical or electrical (e.g., PIN diode) switching control may be utilized. Preferably, controllable electrical switches are located at points having approximately zero RF potential. Distributed capacitance is also preferably employed for reducing terminal inductance, preventing the establishment of spurious magnetic fields and facilitating the use of electrical switching diodes and/or varactor capacitance elements. Such distributed capacitances are also dimensioned so as to cause the terminal inductance of each coil to be within the tuning/matching range of a common tuning/matching RF circuit.

MULTIWIRE PROPORTIONAL CHAMBERS FOR BIOMEDICAL APPLICATION

Abstract Multiwire proportional chambers with delay-line readouts, currently used for particle trajectory measurements in high-energy physics, are being adapted for a variety of biomedical applications including X-radiography, neutron radiography, and radioisotope imaging. This paper describes chamber-design features and gives calculated and measured efficiency and resolution data. Sample radiographic images taken with prototype chambers are shown.

Switched field magnetic resonance imaging

We describe the implementation of a field—cycling electromagnet in a whole—body clinical MRI system. A pulsed magnet is driven on during dead times of the NMR sequence and serves to increase the equilibrium magnetization induced in the patient Signal transmission and reception occurs only during the period when the electromagnet is turned off and does not otherwise influence the data collection. Applications of the technology include image quality enhancement for low field MRI and for in vivo localized relaxation rate measurements.

Method and apparatus for MRI using selectively shaped image volume of homogeneous NMR polarizing field

An electromagnet shim coil is utilized for temporarily altering the shape of a volume in which there is provided a substantially homogeneous NMR polarizing field. By temporarily energizing the electromagnet shim coil and thus altering the shape of the volume, magnetic resonance imaging can take place in other than a substantially spherical volume (e.g., in an elongated ellipsoidal-like volume extending axially along a patient so as to encompass a longer section of the spinal column). In the exemplary embodiment, the electromagnet shim coil takes the form of a pancake-like coil with windings positioned so as to create fourth power spherical harmonic in a transverse magnet-type of MRI system.

A GAS MIXTURE FOR MULTI-WIRE CHAMBERS WITH HIGH PROPORTIONAL GAIN

Abstract We describe a gas mixture for multiwire proportional chambers which increases the maximum gain that can be reached with full proportional operation.

Apparatus and method for initially capturing most significant low spatial frequency nmr imaging data

NMR imaging apparatus and method is arranged so as elicit NMR image response data in a predetermined order which provides the more significant lower spatial frequency image data during an initial portion of a relatively long complete image data acquisition cycle. The remaining higher spatial frequency image data is captured during subsequent portions of the overall image data acquisition cycle. In this manner, apparent motion artifact in the resulting image is reduced. Furthermore, such a special data acquisition sequence permits image reconstruction processes to produce a recognizable image at an earlier time in the complete data gathering cycle thus permitting a more timely image display for the apparatus operator to use in monitoring and or controlling the NMR imaging procedure.

Tomography Of Hydrogen With Nuclear Magnetic Resonance (NMR), And The Potential For Imaging Other Body Constituents

Nuclear magnetic resonance (NMR) imaging has already attracted a great deal of attention because it is non-hazardous and because the intrinsic NMR contrast appears to be considerably higher than x-ray contrast. On the other hand, the in-vivo NMR characteristics of normal tissues are not well understood, and no reliable data exist on the potential for differentiating normal from abnormal tissues, or benign from malignant lesions.

Localization of human breast tumors grafted in nude mice with a monoclonal antibody directed against a defined cell surface antigen of human mammary epithelial cells

SummaryA mouse monoclonal antibody (BLMRL-HMFG-Mc5) prepared against a defined cell surface antigen of human mammary epithelial cells, non-penetrating glycoprotein (NPGP), was used in imaging and distribution studies in athymic nude mice grafted with human breast tumors. Forin vivo tissue distribution studies,125I-labeled monoclonal antibody was injected into nude mice carrying simulated metastases of human tumors (breast and colon carcinomas). After 22–24 hr the amount of radioactivity per gram of tissue was 3–4 times higher in the breast tumor than in liver, brain, lung, muscle, or spleen. In contrast, colon carcinoma tissue, grafted and treated likewise, did not show higher accumulation of radioactivity relative to other tissues. At 4 days, the incorporation in breast tumors remained almost as high, while the circulating radioactive tracer and the incorporation in tissues other than breast had fallen significantly.In tumor imaging studies, breast tumor masses as small as 4 mm in diameter were clearly localized on a whole body scan using131I-labeled BLMRL-HMFG-Mc5 antibodies with a High-Purity germanium gamma camera. Normalization of131I-distribution to that of99mTc-pertechnetate increased the specificity of this imaging methodology. The quantitative density of131I-label was 2–3 fold higher over the breast tumor than over comparable areas of the mouse. No positive localization images were obtained for similar implants of colon and lung carcinomas or melanomas after injections of131I-labeled BLMRL-HMFG-Mc5. Localization of human breast tumors in this model can be achieved with131I-labeled anti-breast epithelial monoclonal antibodies.