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Edelman Chapter 021 - Orange Coast College Flipbook PDF
3 AIUM 100mm Test Object • Dead Zoneis evaluated by imaging the pins located superficially in the phantom and determinin
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Quality Assurance Quality Assurance Chapter 21
Goals • Assure proper operation of the system and it components • detect gradual changes • reduce critical down time • decrease the number of equipment produced poor quality exams • minimize repeat imaging due to system problems
Types of devices used • Doppler Phantom
• Beam Profile/slice thickness Phantom
• The routine and periodic evaluation of ultrasound systems to assure optimal image quality • QA programs include • assessment of system components • system repairs • PM • and of course the hated paper work problem of record keeping
Types of devices used • AIUM 100 mm test object
• Tissue Equivalent Phantoms
AIUM 100mm Test Object • Fluid fill with strategically placed pins • the fluid should be that of normal soft tissue • there is not attenuation properties of the fluid • designed to evaluate the accuracy and performance characteristics of the system
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AIUM 100mm Test Object
A Dead Zone E vertical registration B Lateral resolution When
• Axial resolution evaluated when the pins are parallel to the sounds main beam axis
transducer is on oblique corner
B Axial resolution. If transducer is on top C Lateral resolution When transducer is on side C Axial resolution If transducer is on top D Horizontal Registration
• The smallest distance in which 2 pins parallel to the primary beam are displayed as separate objects
AIUM 100mm Test Object • Lateral resolution is evaluated by measuring the size of the pins located perpendicular to the sound beam • Minimum distance two side by side rods are displayed as separate entities (scan side B)
Registration accuracy
located parallel to the beam • If irregularities occur between scan and pin location causes may be system malfunction or sound speed in phantom is different than 1,450 m/s
AIUM 100mm Test Object • Electronic caliper accuracy of the system compares the system measurements against a phantom standard
AIUM 100mm Test Object • The ability of the system to echo’s in the correct position with differing orientations • Vertical depth calibration means the system places the pins at the correct depth when
AIUM 100mm Test Object
• Horizontal calibration is similar to vertical but the pins are located perpendicular to the beam
AIUM 100mm Test Object • Dead Zone is evaluated by imaging the pins located superficially in the phantom and determining the minimum depth a pin can be resolved creating a meaningful reflection
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AIUM 100mm Test Object • Dead Zone is evaluated by imaging the pins located superficially in the phantom and determining the minimum depth a pin can be resolved creating a meaningful reflection • With a tissue equivalent phantom this zone is the shallowest depth in which uniform tissue texture appears
AIUM 100mm Test Object • Focal Zone is a point where the beam is the narrowest and the beams intensity is the greatest. • Lateral resolution is very good and the beam is narrow • array transducers are user controlled and should be carefully evaluated • dynamic receive focusing should produce narrow reflections through a wide range of depths
Uniformity • The systems ability to display similar reflectors throughout the phantom with equal brightness and regardless of the depth • The same TGC and depth should be used from test to test
Tissue Equivalent Phantoms • Mimics the features of normal soft tissue • evaluates characteristics in modern systems – – – –
gray scale tissue texture multi-focus adjustable focus found in phased array transducers
Solid and cystic uniformity • With a tissue equivalent phantom solid masses should appear uniform • cystic masses should be anechoic
Tissue Equivalent Phantoms • Phantom has the following soft tissue associations – – – –
speed of sound attenuation scattering characteristics echogenicity
• evaluates gray scale by viewing hollow and solid cysts within the phantom
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Doppler Phantom • Used to assess characteristics of all Doppler systems including Pulsed , CW and Power • Uses motion from a string moving belt or fluid flow phantom
Sensitivity • Is the ability of the system to resolve low level echo’s and display them. • There are three types – minimum – normal – maximum
Normal Sensitivity • A setting at which all pins in the phantom can be displayed • Output power, TGC,and amplification are set to establish normals • normal sensitivity is at a higher gain than minimum. • All subsequent QA tests are then made at this normal setting • There should be no variance from test to test over time
Slice Thickness Phantoms • Used to determine the systems elevation resolution • measures the beam geometry perpendicular to the imaging plane • the phantom contains a diffuse scattering plane at an angle to the primary beam
• The imaging plane is thicker than the beam width or the pulse length so slice thickness is most likely to degrade image quality
Minimum Sensitivity • Assesses the weakest sonographic echo intensity that can be accurately displayed from the far field • Start by setting the TGC flat then increase the system gain from the minimal setting to just when the deep rods appear • There should be no variance from test to test over time
Maximum Sensitivity • A evaluation of power output and amplification with the system set to the maximum practical levels. • A tissue equivalent phantom is then imaged using these settings. • The depth of the tissue mimicking texture is determined . • The max. visualization depth is then assessed • There should be no variance from test to test over time
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