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54 Cards in this Set
- Front
- Back
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Quality Assurance |
•Routine tests of parameters •Identify problems early •Assure accuracy |
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Parameters Tested |
•AR, LR, beam profile, uniformity, BW, Power, Intensity, Freq, Sensitivity |
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When to Perform QA |
•New unit/xdcr •Yearly or when trauma occurs •More frequently with portable |
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Types of QA Phantoms |
•AIUM 100mm^2, TE, Doppler flow, SUAR, hydrophone •Feedback microbalance system |
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AIUM 100mm^2 Test |
•For A, B, and M Modes •Vel = 1540m/s at 37°, ~3° •Will not mimic soft tissue |
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AIUM 100mm^2 Characteristics |
•No attenuation, not for CR test •For standardized tests |
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Standard Tests |
•Dead zone, detail res, depth/measurement accuracy, sensi, uni |
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Tissue Equivalent Phantoms |
•Mimics soft tissue, for all systems •Plastic case with scanning surface •Standard TGC and exam settings |
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TE Filled With |
•Agar gel, graphite, nylon rods •Various cyst sizes, echogenicities |
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Types of TE Tests |
•DZ, DR, measurement/depth accuracy, CR, penetration, sensi/uni |
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Record XDCR Characteristics |
•Serial number, frequency, crystal size |
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Record Machine Settings |
•Overall power and gain |
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Focus |
•Set at consistent depth with previous studies |
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Dead Zone |
•Region from xdcr to useful echoes •No useful info, reverb artifact •Due to pulse length |
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Pulse Length |
•Long pulse length, large dead zone |
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DZ Measurement |
•Top of image to depth of recognizable tissue/first pin |
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Axial Resolution |
•Dependent on wavelength •Resolve 2 objects along beam path |
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Axial Resolution Test |
•Count number of definite pins •6 = 1mm resolution |
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Lateral Resolution |
•Determined by crystal thickness •See objects perpendicular to beam •Smallest distance between pins |
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LR Beam Profile |
•Pins appear as wide as beam width •Vertically placed pins •Width of smallest pin = LR |
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Vertical Measurement Accuracy |
•Beam profile checks accuracy •Measure near/far pins |
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Accuracy of Vert Measurement |
•Should be within 1mm or 1.5% |
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Horizontal Measurement Accuracy |
•Check near and far distances •Edge to edge |
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Accuracy of Hor Measurement |
•Within 3 mm or 3% |
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Sensitivity |
•Weakest echo detected/displayed •Checks need to increase power •Done over time |
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Sensitivity Comparisons |
•Record gain/output power to compare past/future tests |
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Max Sensitivity |
•Gain and power highest setting •Limited by electrical noise |
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Noise From External Sources |
•Electronic communication networks •Computer terminals |
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Preamplifier |
•Most common source of noise |
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Decreased Sensitivity |
•Damaged xdcr or cables •Electronic drift in pulser/reciever |
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Power/Gain Over Months |
•Increasing settings shows decreasing sensitivity |
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TE Phantom Sensitivity |
•Any change in penetration compared over months •Less depth= less sensitive |
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Uniformity |
•Evenness of gray scale image •Variation = decreased uniformity |
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Causes of Nonuniformity |
•Bad elements •Loose connections in beam former •Poor side to side compensation •Poor pixel blending |
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Loose Connections in Beam Former |
•Vertical non uniformities •Moving unit for portables |
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Poor Pixel Blending |
•Between trans/rec focal zones •Horizontal streaks parallel to xdcr |
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Dynamic Range |
•Varying echogencities of tissues |
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Cyst Resolution |
•Size, number seen, echogencities, posterior enhancement |
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Other QA Tests |
•Clean filters •Loose/damaged cables •Loose handles/wheel locks |
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Slice Thickness |
•Thickness in non imaging plane •Worst measure of spatial res |
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Slice Thickness on TE |
•Scan length of cylinders •Fill in occurs when slice is larger |
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SUAR |
•Sensitivity, uniformity, AR •Stepwedge shaped |
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Hydrophone |
•Mini xdcrs, measure pressure •Determine intensities within beam |
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Feedback Microbalance System |
•Absorber in beam forced by pressure wave, measures power •Average force measured on balance |
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Doppler String Test |
•Thin string around pulley/motor •Moves at specific velocities |
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Doppler String Test Evaluates |
•Velocity measurement accuracy •LR and AR in Doppler •Gate accuracy in Duplex Doppler |
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Doppler String Advantage |
•Small moving target at specific velocity |
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Doppler String Disadvantages |
•String echoes not like blood •Does not mimic velocity distribution in a vessel |
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Doppler Flow Phantom |
•Hollow tube on TE phantom •Fluid pumped through tube |
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Doppler Flow Tests |
•Doppler sensitivity •Alignment of PD sample volume |
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Doppler Sensitivity |
•Max depth that flow waves are detected |
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Doppler Flow Tests |
•Volume flow accuracy •Velocity accuracy of Doppler shift •Color flow penetration •Image congruency |
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Color Flow Penetration |
•Max depth that color data detected •Decreased if varied more than 1 cm |
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Image Congruency Test |
•Alignment of color with B mode •Color should be within vessel on B |
