David A. Molyneaux

Temperature sensing and control system for cardiac monitoring electrodes

A cardiac electrode (40) has a plug (48) which is frictionally received in a socket (50) of an electrical lead (56). An impedance (54) is connected in series between the electrical lead and the socket to pass ECG signals substantially unattenuated and for blocking radio frequency signals induced in the lead from reaching the socket and the electrode and heating the electrode to a sufficient temperature to burn the patient. The impedance includes an LC circuit (66, 68) which freely passes low frequency signals, such as cardiac signals, but which is tuned to resonance at radio frequencies, particularly at the frequency of resonance excitation and manipulation pulses of a magnetic resonance imager (A). Alternately, the impedance may include a resistive element for blocking the induced currents. A temperature sensor (60) is mounted in intimate contact with an electrically and thermally conductive socket portion (52) to sense the temperature of the electrode, indirectly. A temperature sensor lead (62), the cardiac lead (56), and a respiratory or other anatomical condition sensor are connected with a multiplexing means (140) which cyclically connects the output signals thereof with an analog to digital converter (142). The digital signals are converted to digital optical signals (102) to be conveyed along a light path (104) out of the examination region. The bits of the received digital signal are sorted (144) between an R-wave detector (120), a temperature limit check (122) which checks whether the temperature of the electrode exceeds preselected limits, and a respiratory detector (132).

Multiple quadrature surface coil system for simultaneous imaging in magnetic resonance systems

A quadrature multiple coil array (30) includes a plurality of quadrature coil pairs (501, 502, . . . , 50n). Each coil pair includes a loop coil (50) or other coil which is sensitive to radio frequency signal components that are perpendicular to the coil and a flat Helmholtz coil (54) or other coil which is sensitive to radio frequency components parallel to the plane of the coil. The coils of each of the quadrature coil pairs are overlapped (56) by an amount which minimizes coupling between the coils. This enables resonance signals to be picked-up concurrently in quadrature by each of the quadrature pairs and be demodulated by a corresponding series of receivers (321, 322, . . . , 32n). The data from the overlapping regions to which each quadrature pair is sensitive are reconstructed (36) into image representations (38). The image representations are aligned either automatically (40) or by the operator and displayed on a video monitor (44). The overlapping quadrature pairs can be arranged along a planar substrate or along curved substrates which conform to contours of the anatomy of the subject.

Digital combination and correction of quadrature magnetic resonance receiver coils

Magnetic resonance is excited in selected portions of a subject disposed within a temporally uniform magnetic field of a magnetic resonance imaging system. A quadrature coil assembly (30) receives radio frequency magnetic resonance signals from the subject. Commonly, the quadrature coil fails to receive signals in true quadrature over the entire examination region. Resonance signals from a first coil (32) and a second, orthogonal coil (34) are received (40, 42), digitized (44, 46), and Fourier transformed (50, 52) into complex images. Each complex image includes an array or grid of vector data values having a magnitude and a direction or phase angle. If the quadrature coil was truly quadrature over the entire region of interest, the data values of both complex images would be a unit vectors. The vector of one image would be offset by 90° from the vectors of the other. A phase correction board (54) sets the phase angle of the corresponding data values of the first and second complex images to a common vector direction or phase angle. A magnitude correction board (56) adjusts the magnitude of each corresponding data value of the first and second complex images. The phase angle and magnitude corrected complex data images are summed (58) and the real or magnitude image is stored in an image memory (62).