This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ultrasonography, CT, and MRI, Subject name: Radiology
Which of the following techniques use piezoelectric crystals - 
Select and explain. 
A. Ultrasonography, B. X-ray diffraction, C. NMR imaging, D. Xeroradiography
A: Ultrasonography
Answer: A: Ultrasonography 
Explanation: Ans. is 'a' i.e., Ultrasonography o Ultrasonography is based on piezoelectric effect.o MRI is based on gyeromagneticproperty of proton (H+).Ultrasonography (USG) / Ultrasoundo USG is performed with the pulse-echo technique. By the virtue of piezoelectric effect in the ultrasound probe (or transducer), electric energy is converted to sound energy that is transmitted into patient's tissues. The US transducer (probe) then becomes a receiver, detecting echo of sound energy reflected from tissue.o The US transducer (probe) then becomes a receiver, detecting echo of sound energy reflected from tissue.o The ultrasound transducer uses the principle or property of piezoelectricity.o Quartz is a naturally occuring peizoelectric material.o Currently, Lead Zirconate titanate (PZT) is the most widely used material in the ultrasound tranducer/probes