Which of the following modalities uses the principle of piezoelectric effect?
Correct Answer: Ultrasound
Description: Ans: c (Ultrasound) Ref: Bhaduri, Ist ed, p. 5; Grainger, 5th ed, p.Ultrasound is based on piezoelectric effect of crystals made up of lead zirconate titanate.UltrasoundBasic principle is very high frequency sound is directed into the body from a transducer placed in contact with the skin. Transducer contains piezoelectric crystals which converts electrical energy to mechanical energy. Ultrasound is often used to determine whether a structure is solid or cystic. Transducer frequencies used for diagnostic applications range from 2 to 15 MHz.* Abdominal, obstetrical and gynecological ultrasound examination should be performed by 3.5 - 5 MHz frequency transducers.* Transvaginal and transrectal examinations are performed by 5 - 7.5 MHz frequency transducers.* Breast, thyroid and scrotal ultrasound examinations should be performed with 7.5 to 10 Hz. Normal thickness of stomach in USG is 5mm.USG is the method of demonstrating placenta.CT scanIt was invented by G.Hounsfield. CT image is a display of anatomy of a thin slice of the body, developed from multiple X-ray absorption measurements. Radiopaque structure appears white and radiolucent tissue appear black in CT. Bone will appear white whereas fat and gas will appear as black.The CT number (Hounsfield unit)* Value of water (Zero)* Air (-1000)* Dense bone (+1000)* Fat (-100)Magnetic Resonance Imaging (MRI)Imaging principle is based on gyro magnetic property of proton and magnetic moment of nucleus.Magnetic field strength used in MRI is 0.15 to 1.5 Tesla.It is non ionizing and no risk of irradiation.
Category:
Radiology
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