Question 1: Define ultrasound and explain how it differs from audible sound.

Answer: Ultrasound refers to sound waves with a frequency above 20,000 Hz, which is higher than the upper limit of human hearing. Unlike audible sound, ultrasound cannot be heard by humans.

Question 2: Describe the mechanism by which ultrasound waves are produced and detected in medical imaging.

Answer: Ultrasound waves are produced by a piezoelectric crystal that vibrates when an electric current is applied. The waves travel into the body, reflect off structures, and are detected by the same or a different crystal to produce images.

Question 3: What is the typical range of frequencies used in medical ultrasound imaging?

Answer: Between approximately 2 MHz and 15 MHz.

Question 1: An ultrasound wave has a frequency of 5 MHz and travels through soft tissue at a speed of 1540 m/s. Calculate its wavelength.

Answer: Wavelength = Speed / Frequency = 1540 m/s / 5,000,000 Hz = 0.000308 m or 0.308 mm

Question 2: A certain ultrasound device operates at a frequency of 3 MHz. If the wavelength in a medium is measured to be 0.52 mm, what is the speed of sound in that medium?

Answer: Speed = Wavelength × Frequency = 0.00052 m × 3,000,000 Hz = 1560 m/s

Question 1: Outline the safety precautions that should be taken when using ultrasound equipment in medical or industrial settings.

Answer: Ensure the ultrasound intensity is within safe limits, avoid prolonged exposure, and follow guidelines to prevent tissue heating or cavitation. Proper training and protective measures should be used.

Question 2: Explain how ultrasound is used in industry to detect flaws in materials such as aluminium or sulphur.

Answer: Ultrasound testing involves sending high-frequency sound waves into a material. When a wave encounters a flaw, such as a crack or inclusion, part of the wave is reflected back to a receiver. By analysing the reflected signals, technicians can locate and size flaws within the material without damaging it.

Question 3: Describe how the properties of ultrasound waves facilitate medical imaging, including the role of reflection and absorption.

Answer: Ultrasound waves are emitted into the body where they reflect off tissues and organs based on differences in acoustic impedance. The reflected waves are received and processed to create images. The high frequency ensures good resolution, and the minimal absorption allows deep penetration with minimal damage.

Question 1: An ultrasound device measures the time it takes for a wave to reflect from a boundary within tissue as 13 microseconds. If the speed of sound in tissue is 1540 m/s, estimate the depth of the boundary.

Answer: Distance to boundary = (Speed × Time) / 2 = (1540 m/s × 13 × 10⁻6 s) / 2 = 0.01 m or 10 mm

Question 2: Discuss the advantages of using ultrasound over X-ray imaging in medical diagnostics.

Answer: Ultrasound is non-ionising, making it safer for patients, especially for repeated use. It provides real-time imaging, is less invasive, and does not involve exposure to harmful radiation. It is also effective in imaging soft tissues and blood flow, which X-rays are less capable of visualising.