Medical Ultrasound Physics, Doppler Modalities, and Artifacts — WACS Viva & Clinical Scenarios (Radiological Physics, Equipment, and Radiation Safety)

Exam-style medical ultrasound physics, doppler modalities, and artifacts viva scenarios with examiner probes and model answers for Radiology candidates.

Scenarios covered

• SCENARIO 1: Explain the fundamental physical principles of acoustic wave propagation in biological soft tissue, detailing the factors that govern acoustic impedance, reflection, refraction, and overall beam attenuation, and evaluate their direct impact on axial, lateral, and elevational spatial resolution.
• SCENARIO 2: Describe the construction, physical components, and operational mechanics of diagnostic ultrasound transducers, analyzing the roles of piezoelectric materials, backing blocks, quarter-wavelength matching layers, and electronic array beamforming in beam steering and dynamic focusing.
• SCENARIO 3: State the Doppler shift equation, compare the technical mechanics and clinical utilities of Continuous Wave (CW), Pulsed Wave (PW), Color Flow, and Power Doppler modalities, and explain the physical genesis of spectral aliasing alongside systematic methods for its correction.
• SCENARIO 4: Detail the physical mechanisms of Tissue Harmonic Imaging (THI), comparing native harmonic generation with pulse inversion techniques, and define the ultrasound bioeffects safety metrics including Mechanical Index (MI) and Thermal Indices (TIS, TIB, TIC) under the ALARA framework.
• SCENARIO 5: Analyze the acoustic etiology, imaging manifestations, clinical significance, and corrective maneuvers for common ultrasound artifacts, specifically posterior acoustic shadowing, posterior acoustic enhancement, reverberation, comet-tail, ring-down, mirror image, side lobe, and speed-error artifacts.