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Abstract:
many ferromagnetic materials, especially nickel and certain ferrites, demonstrate magnetostrictive properties, i.e., they undergo a change in length along the direction of an applied magnetic field. this phenomenon is used to form an imaging system, using both electromagnetic and ultrasonic waves, with many characteristics different from the normal pulse-echo ultrasonic system. magnetostrictive particles are placed in the region of the body to be imaged, for example, a colloidal suspension in the g.i. tract. instead of transmitting an ultrasonic wave into the body, an electromagnetic wave is used at low ultrasonic frequencies to propagate a magnetic field. this magnetic field passes through the body at the speed of light with interactions at the administered particles. the magnetostrictive particles vibrate with the magnetic field, generating an ultrasonic wave. this ultrasonic wave can be received as any pulse-echo signal by any ultrasonic receiving system. several advantages of this technique are apparent. first, since the electromagnetic waves travel to the magnetostrictive sites at the speed of light, round trip transit time is cut in half versus pulse-echo systems. second, the higher energy electromagnetic transmitted wave does not interact appreciably with body tissues, only with the magnetostrictive particles. finally, and most important, this type of imaging system is an emissive one, only those regions having the administered material produce an ultrasonic return wave. (author)
| Pages: |
15 |
| Report Date: |
JUN 78 |
| Report Number: |
D158213 |
Report Unavailable |
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