Magnetic resonance imaging apparatus

The fundamental limit for NMR imaging is set by an intrinsic signal-to-noise ratio (SNR) for a particular combination of rf antenna and imaging subjects. The intrinsic SNR is the signal from a small volume of material in the sample competing with electrical noise from thermally generated, random noise currents in the sample. The intrinsic SNR has been measured for a number of antenna-body section combinations at several different values of the static magnetic field and is proportional to B0. We have applied the intrinsic and system SNR to predict image SNR and have found satisfactory agreement with measurements on images. The relationship between SNR and pixel size is quite different in NMR than it is with imaging modalities using ionizing radiation, and indicates that the initial choice of pixel size is crucial in NMR. The analog of "contrast-detail-dose" plots for ionizing radiation imaging modalities is the "contrast-detail-time" plot in NMR, which should prove useful in choosing a suitable pixel array to visualize a particular anatomical detail for a given NMR receiving antenna.

The intrinsic signal-to-noise ratio in NMR imaging.

Methods for the high yield production of antibody Fv-containing polypeptides, especially Fab′ and F(ab′) 2 antibody fragments are provided. Expression of heavy and light chain Fv in a microbial secretory system is followed by recovery of Fv from the periplasm under conditions that maintain a cysteine residue as a free thiol. The free thiol is reacted with free thiol of an antibody fragment of the same or differing specificity, or with agents such as diagnostic labels or therapeutic moieties. The products offer advantages of homogeneity and purity not available through the use of known methods for preparing such derivatives.

Expression of functional antibody fragments

Adiabatic pulses for wideband inversion and broadband decoupling

This review summarizes recent progress in the design and applications of cadmium-free quantum dots (Cd-free QDs), with an emphasis on their role in biophotonics and nanomedicine. We first present the features of Cd-free QDs and describe the physics and emergent optical properties of various types of Cd-free QDs whose applications are discussed in subsequent sections. Selected specific QD systems are introduced, followed by the preparation of these Cd-free QDs in a form useful for biological applications, including recent advances in achieving high photoluminescence quantum yield (PL QY) and tunability of emission color. Next, we summarize biophotonic applications of Cd-free QDs in optical imaging, photoacoustic imaging, sensing, optical tracking, and photothermal therapy. Research advances in the use of Cd-free QDs for nanomedicine applications are discussed, including drug/gene delivery, protein/peptide delivery, image-guided surgery, diagnostics, and medical devices. The review then considers the pharma...

New Generation Cadmium-Free Quantum Dots for Biophotonics and Nanomedicine

The choice of the strength of the magnetic field for an imaging system based on the nuclear magnetic resonance of hydrogen is considered. It is shown by an analysis based on in vitro data that the quality, or contrast-to-noise ratio, of images based on T1 or T2 discrimination increases with field up to 1.5-2 T. After a brief discussion of potential high-field limitations, results are presented which show that images of the human head with excellent anatomic detail can be produced at 1.5 T or 64 MHz.

https://www.ajronline.org/doi/pdfplus/10.2214/ajr.141.6.1195

Nuclear magnetic resonance imaging: contrast-to-noise ratio as a function of strength of magnetic field

Radio-frequency spectrometer subsystem for a magnetic resonance imaging system

System for controlling operation of a plurality of gaseous discharge lamps for selectively turning on or off one or more of the lamps and producing desired lumen output of the lamps as needed, to provide for conservation of electrical energy. In the system, each of the discharge lamps is connected to a separate variable impedance ballast device, a control circuit for varying the impedance of each ballast device, and a signal processing circuit connected to each control circuit for operating the same, and a signal transmitting device for transmitting information to each of the signal processing circuits, whereby the latter circuits selectively operate the respective control circuits in response to the information received from the signal transmitting device. In a preferred embodiment, the signal transmitting device is a remote transmitter such as a radio frequency signal device for remote control of the lighting system.

Lighting control system

Pulse sequences which generate multiple-and zero-quantum coherence and suppress the detection of single-quantum coherence have ben used to greatly reduce the intensity of the water signal in NMR images. In the experiment, image signals having multiple-quantum behavior add constructively while single-quantum signals, such as the signal arising from water, are canceled. Since the generation of multiple-quantum coherence is only a function of spin-spin coupling, water suppression by this technique is independent of chemical shift. Consequently, suppression of the water resonance in a 1H NMR image can be accomplished in an inhomogeneous magnetic field provided that the excitation profile of the rf pulses is equal for all spins. Furthermore, variations in the T1 and T2 of coupled and uncoupled spins do not affect the efficiency of the multiple-quantum filter. © 1986 Academic Press, Inc.

Dimitrios Vatis

Papers

Nuclear magnetic resonance imaging: contrast-to-noise ratio as a function of strength of magnetic field

Radio-frequency spectrometer subsystem for a magnetic resonance imaging system

Lighting control system

Water suppression in 1H magnetic resonance images by the generation of multiple-quantum coherence.

Methods of, and apparatus for, proton decoupling in nuclear magnetic resonance spectroscopy