Accession Number : AD0657255

Title :   CONSIDERATIONS UNDERLYING THE USE OF ULTRASOUND TO DETECT GALLSTONES AND FOREIGN BODIES IN TISSUE,

Corporate Author : NAVAL MEDICAL RESEARCH INST BETHESDA MD

Personal Author(s) : Ludwig,George D. ; Struthers,Francis W.

Report Date : 16 JUN 1949

Pagination or Media Count : 30

Abstract : The densities of a number of gallstones have been determined and found to vary between 0.82 and 1.10 gm/cc. The velocity of ultrasound through gallstone slabs, beef tissue, and living human muscles has been measured. The velocity through the gallstones varied between 1400 and 2200 m/sec. The velocity through the calf, thigh, and arm muscles of five subjects was found to vary between 1490 and 1610 m/sec with a mean value of 1540 m/sec. The mean velocity through beef tissue at 20-21C was 1540 m/sec. From these data the characteristic acoustic impedance of gallstones and of tissue was determined. Values between 130,000 and 230,000 gm/sq cm/sec were found for the gallstones measured. The acoustic impedance of tissue consisting mostly of muscle is 160,000 to 170,000 gm/sq cm/sec. The energy reflection coefficient for a gallstone in tissue was calculated, and the theoretical feasibility of detecting gallstones by the use of ultrasonic echo-ranging was established. Large signals were obtained from gallstones implanted in the back muscles and in the gallbladders of dogs. A frequency range of 1.0 and 2.5 megacycles has been found to be optimum for an ultrasonic instrument for diagnostic purposes. Penetration of soft tissues for 15 cm or more is afforded, without reaching damaging intensity levels. The wave length in tissue 0.6 to 1.5 mm. provides adequate resolution for the detection of gallstones and most foreign bodies. The possibility of detecting foreign bodies and tumors by use of the echo-ranging principle is discussed. (Author)

Descriptors :   (*ULTRASONIC RADIATION, *DIAGNOSIS(MEDICINE)), (*CALCULI, *BILIARY SYSTEM), TISSUES(BIOLOGY), ACOUSTIC IMPEDANCE, ECHO RANGING, MEDICAL EXAMINATION

Subject Categories : Medicine and Medical Research

Distribution Statement : APPROVED FOR PUBLIC RELEASE