Nuclear magnetic resonance diagnostic apparatus

• US 4,545,384 A
• Filed: 02/23/1984
• Issued: 10/08/1985
• Est. Priority Date: 02/23/1983
• Status: Expired due to Term

• Current Assignee: Tokyo Shibaura Denki Kabushiki Kaisha 72 Horikawa-Cho Saiwai-Ku Kawasaki-Shi Japan
• Original Assignee: Tokyo Shibaura Denki Kabushiki Kaisha
• Inventors: Kawachi, Tatsuhiko
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Smith, Ruth S.
• Application Number:
  US06/582,701
• Time in Patent Office: 593 Days
• Field of Search: 128/653, 128/722, 128/727, 128/721, 128/660-661
• US Class Current: 600/413
• CPC Class Codes: G01R 33/5673 Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker

Abstract

Nuclear magnetic resonance diagnostic apparatus which forms an image of a slice of an object, including an apparatus for detecting NMR signals induced from an object with a condenser and a resonance circuit being provided with a receiving coil which surrounds the object, peakhold means for receiving the NMR signals generated from the resonance circuit to retain the maximum value in the NMR signals in the predetermined order which are picked up in every excitation cycle of the spins, and means for controlling the selection of the NMR signals when the retained value by the peak-hold means is in the synchronous level set previously, utilizing the variation of the NMR signal level in accordance with the variation of floating capacitance of the resonance circuit, which is altered according to the living motion of the object, to detect the state of the living motion, while thereby selecting the NMR signals in the predetermined state to utilize them into image reconstruction.

Claims

1. A nuclear magnetic resonance (NMR) diagnostic apparatus for forming an image of a slice of an object, said apparatus including means for inducing NMR signals in the object, comprising:

receiving means including resonant circuit means responsive to NMR signals for producing output signals;

data processor means coupled to said receiving means for (1) digitizing the output signals to digital data, (2) Fourier transforming the digital data into projecting data, (3) storing said projection data, (4) generating signals indicative of time periods, and (5) generating control signals in response to the receipt of a synchronous signal;

peak-hold means coupled to said receiving means and responsive to said time period signals for holding a maximum value from a set of output signals received during each of said time period;

synchronous means coupled to said peak-hold means for comparing said maximum value outputted from said peak-hold means with a reference level, and outputting a synchronous signal to said data processor in response to said maximum value being greater than said reference level to produce a control signal;

automatic tuning means coupled to said data processor means and to said resonant circuit means responsive to the receipt of a control signal from the data processor means, for adjusting the resonance of said resonant circuit means, to keep said resonant circuit means at a predetermined setting for collecting NMR signals; and

a monitor coupled to said data processor means for displaying said image from said projection data.

2. The NMR apparatus as set forth in claim 1 wherein said resonant circuit includes a variable capacitor means responsive to said automatic adjusting means for adjusting the resonance of said resonant circuit means.

3. The NMR apparatus as set forth in claim 1 wherein the NMR signals are generated by hydrogen nuclei in the object and said resonant circuit means includes a receiver coil and a variable capacitor means responsive to said automatic adjusting means for adjusting the resonance of said resonant circuit means to the same frequency as the NMR signal frequency of hydrogen nuclei within the object.

4. The NMR apparatus as set forth in claim 1 wherein said synchronous means further includes an electrocardiogram input for an electrocardiogram signal for synchronizing said synchronous signal with said electrocardiogram signal.

5. A nuclear magnetic response (NMR) diagnostic apparatus for monitoring the NMR of atomic nuclei substances of a body which is subjected to magnetic forces at a predetermined frequency, which comprises:

a resonant circuit having a coil and an adjustable capacitor connected in parallel, said coil shaped to surround a portion of the body to form a floating capacitor between said coil and the body wherein the capacitance of the floating capacitor varies in accordance with movements of the body;

means for tuning said adjustable capacitor to control said resonant circuit to operate at various resonant frequencies;

means responsive to said coil detecting an NMR signal from the body being subjected to the magnetic forces for producing output frequency signals having amplitudes indicative of a characteristic of the body;

processor means for receiving said output frequency signals, for generating control signals to operate said tuning means, and for generating successive period setting signals;

peak hold circuit means responsive to said output frequency signals during generation of successive period setting signals for producing signals representing the level of the NMR signals;

means for comparing said NMR level signals with a predetermined reference level and accordingly generating a synchronous signal;

upon said NMR level changing by a predetermined amount; and

monitor means coupled to said processor means and responsive to said synchronous signal for displaying an image.