MCQs (1) – Questions Ultrasound propagates through the medium as a transverse wave Ultrasound velocity is equal to the product of frequency and wavelength Ultrasound velocity is lower in a stiff medium Acoustic impedance is the product of ultrasound velocity and the density of the medium Acoustic impedance of air is almost zero

MCQs (1) - Answers Ultrasound propagates through the medium as a transverse wave Ultrasound velocity is equal to the product of frequency and wavelength Ultrasound velocity is lower in a stiff medium Acoustic impedance is the product of ultrasound velocity and the density of the medium Acoustic impedance of air is almost zero

MCQs (1) - Corrections Ultrasound propagates through tissue as a longitudinal wave, therefore, the local movement of the tissue particles is in the same direction as the wave propagation Ultrasound travels faster in stiff, non-compressible media

MCQs (2) – Questions Ultrasound is attenuated by energy loss from the main beam caused by absorption, reflection and scattering The attenuation is proportional to frequency Specular reflection occurs when the size of the reflector is much smaller than the ultrasound wavelength The degree of ultrasound reflection at an interface between different soft tissue is up to 25% (Fat-muscle interface) The angle of refraction is governed by Snell’s law

MCQs (2) - Answers Ultrasound is attenuated by energy loss from the main beam caused by absorption, reflection and scattering The attenuation coefficient is proportional to frequency Specular reflection occurs when the size of the reflector is much smaller than the ultrasound wavelength The degree of ultrasound reflection at an interface between different soft tissues is up to 25% (Fat-Muscle interface) The angle of refraction is governed by Snell’s law

MCQs (2) - Corrections c) Specular reflection occurs when the size of the reflector is much larger than the ultrasound wavelength d) Up to 1-2% is reflected.

MCQs (3) - Questions An ultrasound transducer contains a piezoelectric crystal At the resonant frequency the transducer produces ultrasound of a wavelength equal to twice the thickness of the crystal For a single crystal transducer the length of the near field is proportional to the squared radius of the transducer and inversely proportional to wavelength For a single crystal transducer the area where beam starts to diverge is termed Fresnel region For a single crystal transducer the angle of divergence is proportional to ultrasound wavelength

MCQs (3) - Answers An ultrasound transducer contains a piezoelectric crystal At the resonant frequency the transducer produces ultrasound of a wavelength equal to twice the thickness of the crystal For a single crystal transducer the length of the near field is proportional to the squared radius of the transducer and inversely proportional to wavelength For a single crystal transducer the area where beam starts to diverge is termed Fresnel region For a single crystal transducer the angle of divergence is proportional to ultrasound wavelength

MCQs (3) - Corrections d) The Fresnel region is another name for the near field, the Fraunhofer region is another name for region where the beam starts to diverge in far field.

MCQs (4) - Questions Focusing on array probe is achieved by transmitting from the innermost elements of the active group first The longer the time delay between transmitting from the elements of the array, the longer the focal distance A low Q transducer has a wide bandwidth Lateral resolution is the ability to resolve two objects lying side by side at the same depth In the focal area, axial and lateral resolutions are equal

MCQs (4) - Answers Focusing on array probe is achieved by transmitting from the innermost elements of the active group first The longer the time delay between transmitting from the elements of the array, the longer the focal distance A low Q transducer has a wide bandwidth Lateral resolution is the ability to resolve two objects lying side by side at the same depth In the focal area, axial and lateral resolutions are equal

MCQs (4) - Corrections Focusing in a linear array is achieved by first energising the outermost elements of the active group A long focal distance is obtained by using a short delay between energising the outer and innermost elements of the active group Axial resolution is a component of pulse length and lateral resolution is a component of beam width. Beam width is larger than the pulse length, so the lateral resolution is worse

MCQs (5) - Questions In B-Mode to avoid flicker the frame rate should be at least 50 fps The maximum achievable frame rate in B-mode with a line density of 100 and a depth of view of 15 cm is approximately 100 fps THI uses second harmonic frequencies of the fundamental frequency THI requires a wide bandwidth transducer One of the main advantages with THI is that it reduces reverberation and side lobe artefacts

MCQs (5) - Answers In B-Mode to avoid flicker the frame rate should be at least 50 fps The maximum achievable frame rate in B-mode with a line density of 100 and a depth of view of 15 cm is approximately 100 fps THI uses second harmonic frequencies of the fundamental frequency THI requires a wide bandwidth transducer One of the main advantages with THI is that it reduces reverberation and side lobe artefacts

MCQ (5) - Corrections The limit of temporal resolution of a human eye is about 40 ms, so ideally the frame rate should be above 25 fps In one second ultrasound needs to travel double the distance ‘d’ (from the probe to the depth of view and then back) as many times as the number of scan lines multiplied by frame rate. Therefore, it travels a total distance of 2 x d x frame rate x number of scan lines with average velocity of 1540 m/s. Therefore, the max frame rate can be calculated as FR= 1540 / (2 x d x n)= 1540/(2 x 0.15 x 100)= 50f/s

MCQs (6) - Questions The Doppler shift frequency only depends on the original frequency of the ultrasound the velocity of the ultrasound through the medium and the velocity of the reflector Continuous wave Doppler allows you to monitor the depth of a target Continuous wave Doppler is an audible sound To detect slow flow it may be necessary to decrease the Doppler frequency or increase PRF The signal to noise ratio can be improved by using a low pass frequency filter

MCQs (6) - Answers The Doppler shift frequency only depends on the original frequency of the ultrasound the velocity of the ultrasound through the medium and the velocity of the reflector Continuous wave Doppler allows you to monitor the depth of a target Continuous wave Doppler is an audible sound To detect slow flow it may be necessary to decrease the Doppler frequency or increase PRF The signal to noise ratio can be improved by using a low pass frequency filter

MCQs (6) - Corrections The Doppler shift also depends on the angle of isonation There is no depth discrimination An increase in Doppler frequency results in a larger frequency shift which is easier to detect. Decreasing the PRF increases sensitivity to small frequency shifts

MCQs (7) - Questions The sampling volume in Colour Doppler is used to determine depth information The maximum depth depends on changes in the velocity of the medium Aliasing is governed by the Nyquist criterion Colour Doppler is not susceptible to aliasing Colour Doppler is based on a continuous wave

MCQs (7) - Answers The sampling volume in Colour Doppler is used to determine depth information The maximum depth depends on changes in the velocity of the medium Aliasing is governed by the Nyquist criterion Colour Doppler is not susceptible to aliasing Colour Doppler is based on a continuous wave

MCQs (7) - Corrections The maximum depth depends on the PRF. d=c/2PRF Nyquist criterion applies as with spectral Doppler Colour Doppler uses a pulsed Doppler to give depth dependant information

MCQs (8) - Questions TI is the ratio of the power emitted to the power required to increase the temperature by 1• C B-Mode imaging poses greater heating risks than Doppler Heating is only caused by transducer surface warming up There are three TI equations used for tissue, bone an cranial ultrasound The ICE Standard (2007) specifies that the surface temperature rise must not exceed 43• C when in contact with the patient

MCQs (8) - Answers TI is the ratio of the power emitted to the power required to increase the temperature by 1• C B-Mode imaging poses greater heating risks than Doppler Heating is only caused by transducer surface warming up There are three TI equations used for tissue, bone an cranial ultrasound The IEC Standard (2007) specifies that the surface temperature rise must not exceed 43• C when in contact with the patient

MCQs (8) - Corrections b) Doppler techniques pose greatest thermal risk c) Heating is caused by the combination of apsorption of the ultrasound waves and the heat produced at the transducer surface

MCQs (9) - Questions MI equals the peak rarefactional pressure divided by the ultrasound frequency Non-inertial cavitation causes acoustic streaming and shock For MI < 0.7, conditions for inertial cavitation probably do not exist The presence of microbubbles decreases the risk of cavitation The risk of cavitation is increased in a prenatal lung

MCQs (9)- Answers MI equals the peak rarefactional pressure divided by the ultrasound frequency Non-inertial cavitation causes acoustic streaming and shock For MI < 0.7, conditions for inertial cavitation probably do not exist The presence of microbubbles decreases the risk of cavitation The risk of cavitation is increased in a prenatal lung

MCQs (9) - Corrections a) MI equals the peak rarefactional pressure divided by the square root of the ultrasound frequency d) The use of contrast agents (microbubbles) will increase the likely hood of cavitation e) The fetal lung is not aerated, therefore, no increase to the risk of cavitation

MCQs (10) – Questions BMUS Guidelines Up to 10 weeks fetal gestation the operator should monitor TIS There are no scan time restrictions when scanning with TI<0.7 Scanning of embryo or fetus is not recommended, however briefly, with TI>2.0 Consent is required from the patient when the scan is performed by a trainee There are no time restrictions when an ultrasound examination is performed by a trainee

MCQs (10) - Answers Up to 10 weeks fetal gestation the operator should monitor TIS There are no scan time restrictions when scanning with TI<0.7 Scanning of embryo or fetus is not recommended, however briefly, with TI>2.0 Consent is required from the patient when the scan is performed by a trainee There are no time restrictions when an ultrasound examination is performed by a trainee

MCQs (10) - Corrections Scanning of embryo or fetus is not recommended however briefly, with TI>3.0 e) The time should not exceed double that needed for a diagnostic examination

MCQs (11) - Questions An imaging phantom is made using a tissue mimicking material (TMM) RCR guidance states electrical safety testing of the ultrasound scanner should be performed bi-annually RCR guidance states QA testing of the ultrasound scanner should be performed bi-annually Doppler ultrasound could be tested using a flow phantom A radiometer can be used to measure the heat pattern from a transducer

MCQs (11) - Answers An imaging phantom is made using a tissue mimicking material (TMM) RCR guidance states electrical safety testing of the ultrasound scanner should be performed bi-annually RCR guidance states QA testing of the ultrasound scanner should be performed bi-annually Doppler ultrasound could be tested using a flow phantom A radiometer can be used to measure the heat pattern from a transducer

MCQs (11) - Corrections b) RCR guidance states electrical safety testing of the ultrasound scanner should be performed annually c) RCR guidance states QA testing of the ultrasound scanner should be performed annually or bi-annually