Physics Exam 4 (100%) QUESTIONS AND ANSWERS (2025 LATEST VERSION).

Physics Exam 4 (100%) QUESTIONS AND ANSWERS (2025 LATEST VERSION). What is a transducer? What are their two functions? any device that converts one form of energy into another 1. electrical energy is converted to sound 2. sound energy is converted into electricity Piezoelectric effect describes the property of certain materials to create a voltage when they are mechanically deformed or when pressure is applied to them have a cyclic voltage ( every half cycle, + and - switch from top to bottom) (ie. positive and negative points) Piezoelectric materials A material, such as lead zirconate titanate, that has piezoelectric properties (PZT) Why is the case important for a transducer? the case protects from shock and breaking of the crystal Why is the shield important for a transducer? cancels noise that has nothing to do with the patient (dont get RF noise) Why is the insulator important for a transducer? it isolates other noise Why is the matching layer important for a transducer? Controllable? Unit? What is it between? decreases reflections at the PZT/skin boundary which increases the amount of sound transmitted (PZTMLGelHuman soft tissue) nonadjustable and unit of measure =Rayl it is between the crystal and the patient Why is the backing material important for a transducer? Controllable? What is it between? enhances axial res by shortening the pulse and duration by putting a dampening material it is dynamic=no control because it is done by the machine between the sonographer and the crystal PZT mechanism expansion= - + which is attracted contraction= + - which is compelled at rest= Air gap =100 % reflection=not good images What is the matching layer cut into? cut into a quarter of the wavelength What is the transducer cut into? cut in half dynamic means no control over it Characteristics of the backing material? What are the additional consequences when using backing material? -High degree of sound absorption -Acoustic impedance similar to PZT decreased sensitivity, wide bandwidth, and low quality factor decreased sensitivity during reception, transducers with damping material are less able to convert low-level sound reflections into meaningful electrical signals (reduces vibration because of the backing layer) wide bandwidth low quality and short duration (containing many different frequencies above and below the transducer's main frequency) typically we use wide bandwidth for better axial res because of the shorter SPL (narrow pulse width) Bandwidth the range or difference between the highest and the lowest frequencies in the pulse ex. frequency is 2 to 6 MHz (6-2 =4) so you would have a 4 bandwidth high quality factor long pulse narrow bandwidth (no backing material) continuous and therapeutic wave doppler low quality factor QF= main frequency/bandwidth (unitless) (formula) Wide bandwidth,Short pulse=Low Q-factor Narrow bandwidth,Long pulse=High Q-factor usually less than 1 Frequency of sound in continuous wave? the frequency of sound emitted is equal to the frequency of the electric signal (just for continuous only) duty factor 1, no aliasing, and no image Pulsed wave transducers short duration electrical spike that travels down the wire and strikes the PZT crystal Operating frequency depends on the speed of sound in the PZT and the thickness of the PZT Speed of sound in PZT affect frequency? speed of sound and frequency are directly related higher speed of crystal the higher the amount of sound out of the crystal (faster PZT = shorter wavelength because sound moves out of the crystal faster) lower frequency=slower amount of sound vibrations (takes longer to travel) Do we have control over the speed of the material? Do we have control over the thickness of the crystal? no no How is crystal thickness related to fop? crystal thickness to fop is indirect fop (proportional sign) Cx/Xmm (op frequency (proportional sign) speed/thickness of crystal)) READ CHAPTERS IN EDELMAN ON 2D IMAGING AND REAL TIME IMAGING READ What determines the resonance frequency of a transducer? a. the thickness of the transducer element and the propagation speed of the transducer material b. media propagation speed multiplied by the propagation speed of the transducer material c. element spacing and transducer diameter d. frequency of the driving voltage and the media propagation speed the rate at which electric pulses are delivered to the element a. the thickness of the transducer element and the propagation speed of the transducer material resonance = operating You are preforming an ultrasound exam with a wide bandwidth transducer. The advantage you obtain with this transducer compared to narrow band transducer: a. decreased acoustic power output b. improved axial resolution c. improved lateral resolution d. improved focusing e. wideband transducers can be autoclaved b. improved axial resolution better SPL and usually 1 cycle per pulse You have been asked to perform an ultrasound examination of the thyroid which unfocused transducer would provide the longest near zone length for this superficial study? a. 10 MHz, 6 mm diameter b. 7.5 MHz, 6 mm diameter c. 10 MHz, 4mm diameter d. 7.5 MHz, 4 mm diameter e. 3.5 MHz, 3 mm diameter a. 10 MHz, 6 mm diameter fop and D^2 Which of the following can best improve lateral resolution? a. increased damping b. decreased frequency c. increased bandwidth d. use of a curved crystal e. decreased aperture d. use of a curved crystal curvature gives more focus The location where the sound beam reaches its narrowest diameter is known as the: A: Fraunhofer zone B: Beam area C: Fresnel zone D: Curie point E: Focal zone E: Focal zone ie. focal point You are using a type of focusing that varies the number of crystals being fired in a segment. This is called a. transmit focusing b. dynamic receive focusing c. aperture focusing d. mechanical focusing e. lens focusing c. aperture focusing is the def of aperture The term for a transducer that has an array of rectangular elements arranged in a straight line is: A: Annular array B: Linear array C: Curved array D: Oscillating mechanical transducer E: Convex sequenced array B: Linear array For a linear array transducer consisting of a single row of elements, what method is most used to focus the beam in the elevational direction? A: Transmit focusing B: Dynamic receive focusing C: Aperture focusing D: Mechanical focusing E: None of the above D: Mechanical focusing internal and external of the crystal and is what you always have for elevational What transducer produces a beam that is symmetrical about the beam axis? a. annular array b. linear sequenced array c. phased array d. curved array e. tightly curved array a. annular array circular and mechanically steered around crystals in each other The ultrasound system in your lab has a transducer with a small footprint. This kind of transducer has the following disadvantages: A: it is too large to use for intercostal scanning B: The field of view in the far field is only 1/4 the diameter of the transducer C: The near-field lateral resolution is poor D: The Q value is very high E: Focusing degrades at a depth of twice the transducer aperture E: Focusing degrades at a depth of twice the transducer aperture Which of the following will NOT improve axial resolution? a. increased damping b. increased transducer frequency c. increased bandwidth d. decreased pulse length e. increased focusing e. increased focusing lateral resolution You are reviewing an ultrasound image that has a sector display format that has a sector display format with a pointed top. What kind of transducer was most likely used to acquire this image? A: Linear array B: Phased array C: Curved array D: Annular array E: Mechanical sector .. Where is the point of maximum intensity in a sound beam? a. curie point b. fresnel zone c. focal point d. fraunhofer zone e. f number c. focal point most concentrated (smallest area=highest intensity) Constructive and deconstructive interference of sound waves from each individual sound source of a transducer is known as: a. snell's law b. Huygens principle c. attenuation d. refraction e. Rayleigh scattering b. Huygens principle Increasing the transducer diameter has which of the following effects? a. increases the near zone length b. increases the frequency c. increases the beam diameter in the far field d. a and c e. all of the above d. a and c higher diameter = higher near zone if it starts bigger, it ends bigger A linear array transducer with 4 transmit focal zones selected requires how many pulses on each vector to create the image? a. one b. two c. four d. six e. eight c. four good for lateral resolution but bad for frame rate If you wish to adjust the focusing characteristics while scanning with a curved linear array you are manipulating what type of focusing are you manipulating? a. dynamic receive b. dynamic aperture c. multizone transmit d. mechanical internal e. mechanical external c. multizone transmit only we can adjust dynamic because of the nature of the array Which of the following transducers is electronically focused but mechanically steered? a. segmental liner array b. switched linear array c. phased linear array d. single element mechanical sector e. annular array e. annular array What type of transducer has the same measurement for elevational and lateral resolution? a. convex linear array b. phased linear array c. annular array d. sequential linear array e. mechanical sector c. annular array symmetric You are using a linear array transducer to image a thyroid mass and would like to use a transducer in which the thinnest slice thickness is close to the depth of the mass. Where is the thinnest width of the sound beam in the out-of-plane dimension? a. it is at the point of mechanical focusing b. it is at the point of electronic focusing c. the beam is the same width throughout the image d. it is in the far field a. it is at the point of mechanical focusing out of plane dimension=elevational (into out of the screen) and is mechanical Another name for axial resolution is: a. transverse resolution b. azimuthal resolution c. angular resolution d. range resolution e. a and c d. range resolution LARRD If you measure the beam width on a standard one dimensional linear array transducer, which measure of resolution would be the worst? a. axial b. lateral c. elevational d. contrast e. temporal c. elevational because of the mechanical focusing what should you do to obtain the best lateral resolution for a given transducer? a. use the maximum acoustic power b. use the lowest frequency in the bandwidth c. use the maximum number of transmit focal zones d. use the maximum scanning depth c. use the maximum number of transmit focal zones focal zones greatly impacts lateral resolution You have detected a small hyperechoic focus within the gallbladder. There is no distal acoustic shadow. What can you do to aid visualization of the shadow? a. move the focal zone well below the hyperechoic focus b. increase the transducer frequency c. increase the acoustic power output d. increase the dynamic range e. decrease the scan line density b. increase the transducer frequency more likely to have shadows because of more attenuation When an electrical signal is applied to a piezoelectric element, what happens to the element? a. it undergoes temperature fluctuation b. it expands and contracts c. it produces an electrical signal of the opposite polarity d. it emits electromagnetic radiation e. it loses its piezoelectric properties b. it expands and contracts You are scanning a phantom containing many small, spherical cystic structures imbedded in a tissue-mimicking material. What type of resolution is best evaluated with this phantom? a. axial b. lateral c. contrast d. elevational e. temporal c. contrast not spatial (not axial lateral or elevational) not temporal because it is not moving what statement is NOT true regarding lateral resolution? a. it is equal to beam width b. it is improved by focusing c. it is defined as the minimum separation required to resolve two structures perpendicular to the beam axis d. it is also known as azimuthal resolution e. it remains constant throughout scanning depth e. it remains constant throughout scanning depth hour glass shape The algebraic summation of waves is called a. scattering b. interference c. absorption d. refraction e. diffusion b. interference The matching layer between the piezoelectric element and the tissue is designed to: A: Insulate the patient from the hot crystal B: Reduce the vibration of the transducer C: Reduce the acoustic impedance mismatch between the element and tissue D: Increase the reflection coefficient at the transducer-skin interface E: Decrease spatial pulse length C: Reduce the acoustic impedance mismatch between the element and tissue What transducer factor characterizes the frequency bandwidth of the transmitted ultrasound wave? a. acoustic impedance b. aperture c. electromechanical coupling coefficient d. duty factor e. Q-value e. Q-value The resolution of two structures parallel to the path of the sound beam is termed: a. contrast resolution b. temporal resolution c. axial resolution d. lateral resolution e. azimuthal resolution c. axial resolution parallel/along The sound beam can be focused by all of the following EXCEPT: a. acoustic mirror b. acoustic lens c. curved crystal d. matching layer e. electronic phasing d. matching layer for AIM matching What type of focusing decreases the frame rate? A: Mechanical focusing B: Dynamic receive focusing C: Dynamic aperture focusing D: Multiple transmit focusing E: Curved crystal focusing D: Multiple transmit focusing more pulses For a single transducer to offer multiple frequency selections for scanning, it must have: A: Large dynamic range B: Wide bandwidth C: Multiple rows of elements in the elevational plane D: Dynamic aperture E: Electronic steering capability B: Wide bandwidth The ability to distinguish between adjacent structures that produce echoes of similar amplitude is termed: a. spatial resolution b. axial resolution c. lateral resolution d. temporal resolution e. contrast resolution e. contrast resolution how closes can echoes be in 2 shades of gray that we can tell apart