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Neuro Review
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CT Abd Epiploic Appendagitis
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Signs in Uroradiology
Male breast
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Biopsies
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Mammo Pearls
ACR Appropriateness Criteria Breast Cancer Screen
AVM types
CT Orbits
CT Abd NL
Chiari Malformations
Vesicoureteral Reflux (VUR)
Elbow
XRAY Abdominal Series

Abdomen
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MSK
neuro
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Physics
Ultrasound
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Ultrasound Principles

Velocity of sound in soft tissues: 1540 m/s, lowest in gases, faster in fluid, faster in ST and fastest in bones. Reflection = backscatter

Harmonic imaging: filtering fundamental echoes
Real time compounding: averaging signals from multiple angles, improving signal-to-noise ratio
Power output: strength of the pulse in dB, has thermal index, mechanical index
Gain: amplification of signal from deeper tissue to compensate for more attenuation when compared with superficial structures; TGC (Time Gain Compensation)
Focal zone: focusing the beam at different depth improves resolution at this level
Doppler effect: sound that reflects off a moving object changes frequency: object moving toward the transducer reflect sound at a higher frequency and vice versa. The difference in transmitted and received frequency is Doppler frequency shift and depends on Doppler angle (axis of probe and axis of moving object)
Resistive index = (peak systolic velocity - peak diastolic velocity) / peak systolic velocity, nl 0.5 - 0.7; RI goes up when resistance to flow goes up (thrombosis)
Duplex Doppler sonography: Gray-scale sono + Pulsed Doppler (waveform)
Shadowing: due to sound absorption (stones, calcs; anechoic, clean shadow) or reflection (gas; dirty shadow); fat produce partial shadowing (AML)
Posterior enhancement/Increased through transmission: less attenuation in fluid so pulse is stronger after passing through
Mirroring: gas is the best acoustic mirror, interface between lung and adjacent ST (liver, liver lesion, diaphragm, Doppler)
Ring Down artifact: gas, series of bright echoes
Aliasing: Wrap around from the positive extreme of the scale to the negative extreme; identifies areas of high flow velocities; Increase Pulse Reptition Frequency to decrease aliasing
Tissue vibration: turbulent blood flow - AV fistulas, stenosis, aneurysms