Chapter 69 - Ultrasound Flashcards
What is the function of piezoelectric crystals in ultrasound transducers?
they generate sound waves when stimulated by electricity and produce an electrical current when interacted with sound.
What frequency range do ultrasound transducers typically operate within?
From 1 to 18 MHz.
What is the relationship between frequency and image resolution in ultrasound?
Lower frequencies penetrate deeper but provide poorer resolution; higher frequencies offer better resolution but with less depth.
What type of transducer is best suited for imaging tendons and ligaments?
Linear transducers, due to their high resolution.
How does a curvilinear transducer differ from a linear transducer?
Curvilinear transducers have a convex shape for a larger field of view, sacrificing some resolution.
Why can’t ultrasound waves penetrate air and bone effectively?
Due to differences in acoustic impedance, which affects sound wave transmission.
What are phased-array transducers used for?
Imaging rapidly moving structures, like the heart, due to their ability to send sound waves simultaneously.
What is anisotropism in ultrasound imaging?
The appearance of darker areas on an image due to the ultrasound beam being off-angle to the structure being imaged.
What is acoustic impedance?
The product of a tissue’s density and the velocity of sound within that tissue.
What does the gray scale on an ultrasound image represent?
It indicates the strength of reflected sound, with black showing no reflection and white showing strong reflection.
How can lateral resolution be optimized in ultrasound imaging?
By positioning the focal point at the desired depth to narrow the beam.
What distinguishes axial spatial resolution from lateral spatial resolution?
Axial resolution measures the ability to differentiate structures parallel to the beam, while lateral resolution does so perpendicularly.
What affects the axial resolution of an ultrasound image?
t is determined by the sound wavelength and frequency; higher frequencies yield better axial resolution.
What is the standard velocity of sound used for calculating depth in ultrasound images?
1540 m/s, which corresponds to the speed of sound in soft tissue.
How is the depth of a structure calculated in ultrasound?
Based on the time taken for the sound to travel to the structure and back to the probe.
What are wireless transducers currently being developed for?
Point-of-care ultrasound (POCUS) in human medicine, with potential applications in equine imaging.
What is the primary limitation of wireless ultrasound transducers?
Uncertainty regarding battery life and resolution in clinical settings.
What role does the angle of incidence play in ultrasound imaging?
The angle affects the amount of reflected sound returning to the transducer, influencing image quality and accuracy.
What do the terms hyperechoic, hypoechoic, isoechoic, and anechoic indicate in ultrasound imaging?
Hyperechoic means brighter, hypoechoic means darker, isoechoic means the same echogenicity, and anechoic means no echoes.
How does harmonic imaging enhance ultrasound image quality?
It reduces artifacts by using resonance frequencies, resulting in clearer images with better resolution.
What is the principle behind strain elastography?
It measures tissue compressibility through physical compression and relaxation.
How does shear elastography differ from strain elastography?
Shear elastography measures sound wave propagation through tissue to assess stiffness without needing physical compression.
What is the purpose of contrast medium-enhanced ultrasound?
To predict subclinical tears and monitor healing in equine tendons.
What is the typical preparation process for musculoskeletal ultrasound examinations?
Clipping hair, applying alcohol and acoustic coupling gel, and using a high-frequency linear probe.
Why are stand-off pads used in ultrasound imaging?
They increase the distance between the probe and skin to reduce near-field artifacts.
What is the significance of acoustic coupling gel in ultrasound?
It improves contact between the transducer and the skin, enhancing image quality.
What common issue can arise during ultrasound imaging due to air between the transducer and skin?
Contact artifacts, which appear as black streaks in the image.
How can ultrasound assist in evaluating cervical degenerative joint disease in horses?
It assesses osseous proliferation of cervical joints and guides therapeutic injections.
What structures can be evaluated using ultrasound in the equine cervical region?
The larynx, hyoid apparatus, vocal folds, arytenoid cartilages, and cervical vertebral bodies.
What role does ultrasound play in cervical centesis for cerebrospinal fluid collection?
It guides the needle into the subarachnoid space with minimal blood contamination.
What structures are typically examined when performing an ultrasound of the shoulder?
Biceps brachii tendon, bicipital bursa, humeral tubercles, infraspinatus muscle, and supraspinatus muscle.
Why is a high-frequency transducer (>7 MHz) preferred for shoulder examinations?
It provides good resolution for imaging structures located 4 to 6 cm deep.
Figure 69-5. The zone method for localizing a lesion on the thoracic limb using ultrasound. 1, Superficial digital flexor tendon; 2, deep digital flexor tendon; 3, distal check ligament; 4, suspensory ligament; 5, third metacarpal bone; 6, branches of the suspensory ligament; 7, proximal sesamoid bones; 8, palmar annular ligament.
Figure 69-5. The zone method for localizing a lesion on the thoracic limb using ultrasound. 1, Superficial digital flexor tendon; 2, deep digital flexor tendon; 3, distal check ligament; 4, suspensory ligament; 5, third metacarpal bone; 6, branches of the suspensory ligament; 7, proximal sesamoid bones; 8, palmar annular ligament.
Figure 69-6. Ultrasonographic image of the palmar proximal interphalangeal (pastern) region with the straight sesamoidean ligament and deep and superficial digital flexor tendons identified. In the medial lobe of the deep digital flexor tendon, a focal lesion appears hypoechoic (circle). An edge shadow is also identified (arrow).
Figure 69-5. The zone method for localizing a lesion on the thoracic limb using ultrasound. 1, Superficial digital flexor tendon; 2, deep digital flexor tendon; 3, distal check ligament; 4, suspensory ligament; 5, third metacarpal bone; 6, branches of the suspensory ligament; 7, proximal sesamoid bones; 8, palmar annular ligament.
Figure 69-7. A transverse image of the left coxofemoral joint of an adult horse with pain localized to the hip. The large anechoic region (arrows) is a distended joint capsule and the irregular margin of the femoral head is secondary to osteophyte formation. Ultrasound-guided centesis of the joint space was performed and synovial fluid was obtained that indicated degenerative change rather than infection.
