2026 ARRT Breast Sonography Study Guide
Practice Questions & Answer Rationale
Ultrasound Physics • Breast Pathology •
Imaging Techniques • Procedures • Clinical
Cases Review
Ultrasound Physics
1. What is the wavelength of a 1.5 MHz ultrasound wave in soft tissue?
A. 1.5 cm
B. 1.0 cm
C. 1.5 mm
D. 1.0 mm
Correct Answer: D
Rationale: The speed of sound in soft tissue is approximately 1540 m/s.
Wavelength = propagation speed / frequency. Therefore, 1540 m/s ÷ 1,500,000 Hz
= 0.001 m = 1.0 mm. Knowing wavelength is important because it determines
both spatial resolution and whether a reflection will be specular or diffuse .
2. How does the mechanical index (MI) depend on transducer frequency?
A. Proportional to the square of frequency
B. Inversely proportional to the square of frequency
C. Proportional to the square root of frequency
D. Inversely proportional to the square root of frequency
Correct Answer: D
, Rationale: The mechanical index estimates the likelihood of cavitation. It is
directly proportional to the peak rarefactional (negative) pressure and inversely
proportional to the square root of the ultrasound frequency. Higher frequencies
are associated with less chance for tissue cavitation. For example, increasing
frequency from 2 to 8 MHz reduces the MI by the square root of 4 .
3. What is a disadvantage of spatial compounding compared to normal scan
mode?
A. Reduced signal-to-noise ratio
B. Increased spatial blurring of moving objects
C. Increased prominence of speckle noise
D. Reduced depth of penetration
Correct Answer: B
Rationale: Spatial compounding acquires data from multiple beam angles and
averages them to reduce speckle noise and improve signal-to-noise ratio.
However, since scan lines are acquired sequentially, frame rate is reduced. The
frame averaging effect causes loss of temporal resolution and increased spatial
blurring of moving objects. This mode is not particularly useful with patient
motion .
4. Which transducer design is optimal for breast imaging?
A. Curvilinear array
B. Linear array
C. Phased array
D. Sector array
Correct Answer: B
Rationale: Linear array transducers are optimal for breast imaging because
they provide a rectangular field of view without beam divergence in the near field,
,superior resolution in the near field, and fixed elevation focusing. The rectangular
image format avoids the beam divergence artifact seen with sector and curvilinear
transducers. High-frequency linear transducers (7–15 MHz) provide superior axial
and lateral resolution while maintaining adequate penetration to the chest wall .
5. What is the primary cause of side lobe artifacts?
A. Multiple reflections between strong reflectors
B. Unwanted sound beams emitted at angles outside the main beam
C. Differences in propagation speed between tissues
D. Attenuation of the sound beam by dense tissue
Correct Answer: B
Rationale: Side lobe artifacts result from unwanted sound beams emitted at
angles outside the main beam. These off-axis beams can encounter structures and
return echoes that are displayed as if they originated from the main beam path,
potentially causing misleading echoes on the image .
6. What determines axial resolution in ultrasound imaging?
A. Beam width
B. Spatial pulse length
C. Transducer aperture
D. Dynamic range setting
Correct Answer: B
Rationale: Axial resolution is determined by spatial pulse length. The shorter
the spatial pulse length, the better the axial resolution. Axial resolution improves
with increasing transducer frequency, but penetration decreases. It represents the
minimum reflector spacing that can be distinguished along the beam axis .
, 7. Which artifact may cause structures to appear deeper than they actually
are?
A. Side lobe
B. Shadowing
C. Refraction
D. Propagation speed error
Correct Answer: D
Rationale: Propagation speed error occurs when the assumed speed of sound
(typically 1540 m/s) differs from the actual speed in the tissue being imaged. If the
actual speed is slower than assumed, echoes return later and structures appear
deeper than they truly are. If the actual speed is faster, structures appear
shallower .
8. What is the primary advantage of harmonic imaging?
A. Increased frame rate
B. Improved contrast resolution
C. Deeper penetration
D. Reduced scan time
Correct Answer: B
Rationale: Tissue harmonic imaging uses harmonic frequencies that are
integral multiples of the fundamental frequency. The returning harmonic echoes
are selectively received, which removes echo clutter from fundamental frequency
reflections. This produces enhanced sensitivity to tissue variations and improved
contrast relative to noise. Harmonic imaging is commonly used with microbubble
contrast agents .
9. What is the optimal Doppler angle for accurate velocity measurements?
Practice Questions & Answer Rationale
Ultrasound Physics • Breast Pathology •
Imaging Techniques • Procedures • Clinical
Cases Review
Ultrasound Physics
1. What is the wavelength of a 1.5 MHz ultrasound wave in soft tissue?
A. 1.5 cm
B. 1.0 cm
C. 1.5 mm
D. 1.0 mm
Correct Answer: D
Rationale: The speed of sound in soft tissue is approximately 1540 m/s.
Wavelength = propagation speed / frequency. Therefore, 1540 m/s ÷ 1,500,000 Hz
= 0.001 m = 1.0 mm. Knowing wavelength is important because it determines
both spatial resolution and whether a reflection will be specular or diffuse .
2. How does the mechanical index (MI) depend on transducer frequency?
A. Proportional to the square of frequency
B. Inversely proportional to the square of frequency
C. Proportional to the square root of frequency
D. Inversely proportional to the square root of frequency
Correct Answer: D
, Rationale: The mechanical index estimates the likelihood of cavitation. It is
directly proportional to the peak rarefactional (negative) pressure and inversely
proportional to the square root of the ultrasound frequency. Higher frequencies
are associated with less chance for tissue cavitation. For example, increasing
frequency from 2 to 8 MHz reduces the MI by the square root of 4 .
3. What is a disadvantage of spatial compounding compared to normal scan
mode?
A. Reduced signal-to-noise ratio
B. Increased spatial blurring of moving objects
C. Increased prominence of speckle noise
D. Reduced depth of penetration
Correct Answer: B
Rationale: Spatial compounding acquires data from multiple beam angles and
averages them to reduce speckle noise and improve signal-to-noise ratio.
However, since scan lines are acquired sequentially, frame rate is reduced. The
frame averaging effect causes loss of temporal resolution and increased spatial
blurring of moving objects. This mode is not particularly useful with patient
motion .
4. Which transducer design is optimal for breast imaging?
A. Curvilinear array
B. Linear array
C. Phased array
D. Sector array
Correct Answer: B
Rationale: Linear array transducers are optimal for breast imaging because
they provide a rectangular field of view without beam divergence in the near field,
,superior resolution in the near field, and fixed elevation focusing. The rectangular
image format avoids the beam divergence artifact seen with sector and curvilinear
transducers. High-frequency linear transducers (7–15 MHz) provide superior axial
and lateral resolution while maintaining adequate penetration to the chest wall .
5. What is the primary cause of side lobe artifacts?
A. Multiple reflections between strong reflectors
B. Unwanted sound beams emitted at angles outside the main beam
C. Differences in propagation speed between tissues
D. Attenuation of the sound beam by dense tissue
Correct Answer: B
Rationale: Side lobe artifacts result from unwanted sound beams emitted at
angles outside the main beam. These off-axis beams can encounter structures and
return echoes that are displayed as if they originated from the main beam path,
potentially causing misleading echoes on the image .
6. What determines axial resolution in ultrasound imaging?
A. Beam width
B. Spatial pulse length
C. Transducer aperture
D. Dynamic range setting
Correct Answer: B
Rationale: Axial resolution is determined by spatial pulse length. The shorter
the spatial pulse length, the better the axial resolution. Axial resolution improves
with increasing transducer frequency, but penetration decreases. It represents the
minimum reflector spacing that can be distinguished along the beam axis .
, 7. Which artifact may cause structures to appear deeper than they actually
are?
A. Side lobe
B. Shadowing
C. Refraction
D. Propagation speed error
Correct Answer: D
Rationale: Propagation speed error occurs when the assumed speed of sound
(typically 1540 m/s) differs from the actual speed in the tissue being imaged. If the
actual speed is slower than assumed, echoes return later and structures appear
deeper than they truly are. If the actual speed is faster, structures appear
shallower .
8. What is the primary advantage of harmonic imaging?
A. Increased frame rate
B. Improved contrast resolution
C. Deeper penetration
D. Reduced scan time
Correct Answer: B
Rationale: Tissue harmonic imaging uses harmonic frequencies that are
integral multiples of the fundamental frequency. The returning harmonic echoes
are selectively received, which removes echo clutter from fundamental frequency
reflections. This produces enhanced sensitivity to tissue variations and improved
contrast relative to noise. Harmonic imaging is commonly used with microbubble
contrast agents .
9. What is the optimal Doppler angle for accurate velocity measurements?
