Which statement is NOT a consequence of using backing material in ultrasound transducers?

Which statement is NOT a consequence of using backing material in ultrasound transducers?

• A. Decreased sensitivity
• B. Narrow bandwidth
• C. Low quality factor
• D. Wide bandwidth

Answer: (B)

Backing material dampens the piezoelectric element, absorbing energy from the rear and reducing how strongly the crystal rings after excitation. This damping shortens the acoustic pulse and broadens its frequency content, so the transducer gains a wide bandwidth. At the same time, energy loss to the backing lowers the overall signal strength that goes into the tissue, reducing sensitivity, and it lowers the quality factor because the system is more heavily damped. Therefore, decreased sensitivity, a lower Q factor, and wide bandwidth are expected consequences. The statement that is not a consequence is narrowing bandwidth, since backing actually broadens the bandwidth rather than narrowing it.

Backing material dampens the piezoelectric element, absorbing energy from the rear and reducing how strongly the crystal rings after excitation. This damping shortens the acoustic pulse and broadens its frequency content, so the transducer gains a wide bandwidth. At the same time, energy loss to the backing lowers the overall signal strength that goes into the tissue, reducing sensitivity, and it lowers the quality factor because the system is more heavily damped. Therefore, decreased sensitivity, a lower Q factor, and wide bandwidth are expected consequences. The statement that is not a consequence is narrowing bandwidth, since backing actually broadens the bandwidth rather than narrowing it.