Ultrasound: Probe orientation
Transducers:'
Increasing frequency improves resolution but decreases penetration
Low-frequency transducers: deep structures
High-frequency transducers': superficial structures
o Transducer types:
Curvilinear: large “footprint”, best resolution centralized
Use for abdominal, FAST exam
Phased array: all waves originate from a single point. used to view deep structures.
Use for smaller spaces (between ribs, to look at lungs, heart, etc.)
Use if available for Cardiac
Linear: no array of waves, waves are spread out evenly. used to view superficial structures
Use for soft tissue, vascular access, musculoskeletal, lungs
o Frequency
Each transducer has a range of frequencies. You can select higher or lower frequency for each probe
on the ultrasound machine.
RES = Resolution = Highest end of the probe’s frequency range
Better Picture, lower penetration
PEN = Penetration = Lowest end of the probe’s frequency range
Higher penetration, worse picture
GEN = General = Middle of the probe’s frequency range
o Transducer indicator and orientation:
Sagittal: indicator to patient’s head. Probe placed vertically along body to create a sagittal view with probe marker pointing to patient's head
Transverse: indicator to patient’s right. Probe placed across body right to left to create an axial view with probe marker pointing to patient's right
Coronal: indicator to patient’s head, but probe on lateral side of body. Top of screen is lateral, bottom is medial
o Artifacts: images on ultrasound that ARE NOT REAL.
High-attenuation: Objects decrease the sound wave A shadow results behind a high-attenuating object.This makes the objects behind less visible
Low-attenuation: sound passes through object very easily. Low-attenuating tissue causes everything behind it to appear HYPERechoic or more visible
Mirror image: sound bounces off diaphragm, returning to trasnducer with a longer time of flight. Machine interprets this as more liver tissue across the diaphragm. A mirror image of the liver or spleen across the diaphragm is normal