Magnetic resonance acoustography

#The field of the invention is nuclear magnetic resonance imaging methods and systems. More particularly, the invention relates to the enhancement of MR image contrast.

#The physician has many diagnostic tools at his or her disposal which enable detection and localization of diseased tissues. These include x-ray systems that measure and produce images indicative of the x-ray attenuation of the tissues and ultrasound systems that detect and produce images indicative of tissue echogenicity and the boundaries between structures of differing acoustic properties. Nuclear medicine produces images indicative of those tissues which absorb tracers injected into the patient, as do PET scanners and SPECT scanners. And finally, magnetic resonance imaging (“MRI”) systems produce images indicative of the magnetic properties of tissues. It is fortuitous that many diseased tissues are detected by the physical properties measured by these imaging modalities, but it should not be surprising that many diseases go undetected.

#Historically, one of the physician's most valuable diagnostic tools is palpation. By palpating the patient a physician can feel differences in the compliance or “stiffness”, of tissues and detect the presence of tumors and other tissue abnormalities. Unfortunately, this valuable diagnostic tool is limited to those tissues and organs which the physician can feel, and many diseased internal organs go undiagnosed unless the disease happens to be detectable by one of the above imaging modalities. Tumors (e.g. of the liver) that are undetected by existing imaging modalities and cannot be reached for palpation through the patient's skin and musculature, are often detected by surgeons by direct palpation of the exposed organs at the time of surgery. Palpation is the most common means of detecting tumors of the prostate gland and the breast, but unfortunately, deeper portions of these structures are not accessible for such evaluation. An imaging system that extends the physician's ability to detect differences in tissue compliance throughout a patient's body would extend this valuable diagnostic tool.

#FIG. 1 is a block diagram of an NMR system which employs the present invention;

#FIG. 2 is an electrical block diagram of the transceiver which forms part of the NMR system of FIG. 1;

#FIG. 3 is a first preferred embodiment of a 1D MRE pulse sequence performed by the MRI system of FIG. 1 to practice the present invention;

#Referring first to FIG. 1, there is shown the major components of a preferred NMR system which incorporates the present invention and which is sold by the General Electric Company under the trademark “SIGNA”. The operation of the system is controlled from an operator console 100 which includes a console processor 101 that scans a keyboard 102 and receives inputs from a human operator through a control panel 103 and a plasma display/touch screen 104. The console processor 101 communicates through a communications link 116 with an applications interface module 117 in a separate computer system 107. Through the keyboard 102 and controls 103, an operator controls the production and display of images by an image processor 106 in the computer system 107, which connects directly to a video display 118 on the console 100 through a video cable 105.

#The computer system 107 includes a number of modules which communicate with each other through a backplane. In addition to the application interface 117 and the image processor 106, these include a CPU module 108 that controls the backplane, and an SCSI interface module 109 that connects the computer system 107 through a bus 110 to a set of peripheral devices, including disk storage 111 and tape drive 112. The computer system 107 also includes a memory module 113, known in the art as a frame buffer for storing image data arrays, and a serial interface module 114 that links the computer system 107 through a high speed serial link 115 to a system interface module 120 located in a separate system control cabinet 122.

#The system control 122 includes a series of modules which are connected together by a common backplane 118. The backplane 118 is comprised of a number of bus structures, including a bus structure which is controlled by a CPU module 119. The serial interface module 120 connects this backplane 118 to the high speed serial link 115, and pulse generator module 121 connects the backplane 118 to the operator console 100 through a serial link 125. It is through this link 125 that the system control 122 receives commands from the operator which indicate the scan sequence that is to be performed.