Equipment Testing
The TO is composed of a series of:
0.75 mm diameter stainless steel rods arranges in a pattern between 2 transparent plastic sides
What can be calculated if you know the above:
1. Frequency 2. PRF 3. Duty factor
A good equipment QA program must include 3 componenets
1. Making regular measurements of parameters (sensitivity, range accuracy, dead zone, det res) 2. Record keeping 3. Scheduling of service calls
From a hydrophone what things can be determined:
1. Period 2. PRP 3. Pulse Duration
Devices used for measuring equipment performances can be divided into 2 classes:
1. Test object 2. Tissue equivalent phantom (TEP)
If Prop Speed is known, what can be calculated:
1. Wavelength 2. SPL
The following parameters can be tested using TO:
1. relative system sensitivity 2. axial resolution 3. lateral resolution 4. dead zone 5. range accuracy 6. TGC operation 7. dynamic range
TEPs must have a prop speed of, and an attenuation of:
1540 m/s 1/2 dB/cm/MHz
What % error in measurement in acceptable:
2%
Rods are positioned
2, 4, 6, 8, 10 mm at the TOP surface
Along one side of the TO is a vertical group of rods spaced:
25, 20, 15, 10, 5, 3 mm apart
The rods in the TO are arranged into :
5 groups- each testing a different parameter
Relative system sensitivity:
A measure of how weak a reflection an instrument can display with thte power and overall gain set to the lowest setting w/o using TGC
Range accuracy:
A measure of the machines time base and how linear this time base remains over the whole image
What does a hydrophone measure:
Acoustic pressures which are then used to calculate relative intensities
AIUM:
American Institute of US Medicine
Lateral resolution is dependent upon:
Beam width
TO decreases in what temp:
COLD
Axial resolution is used to check for:
Consistency rather than accuracy
Lateral resolution varies with:
DEPTH
Metal pins or nylon threads are positioned to test:
Detail resolution and range accuracy
Pulse length is related to:
Frequency and Bandwidth
TEP's are made of:
Graphite filled aqueous gel or urethane rubber materials - graphite is used to produce scattering which stimulates soft tissue
TEP:
Has the same measurement elements of a test object but the elements are set inside a material that provides attenuation and scattering as in soft tissue
Acceptance Testing:
INITIAL testing of equipment prior to acceptance of the manufacturer
If impedance is known, what can be calculated:
Intensity
Since the power and overall gain setting is at the lowest, reverberation should be at its:
Minimum - leaving pulse length as the determining factor
A hydrophone is displayed on an:
Oscilloscope
Axial resolution depends upon:
Pulse Length
The dead zone is determined by the:
Pulse length and reverberation artifact
Quality Assurance Testing:
ROUTINE testing of equipment to ensure proper functioning - monitors performance with the use of TO and TEP
What may have an affect on the velocity of sound:
TEMPERATURE
What rods are used for axial resolution and how are they space apart:
The 6 middle rods 5, 4, 3, 2, 1, mm apart
Hydrophone is used to measure:
The acoustic output power of US instruments
Minimum sensitivity:
The amount of overall gain necessary to BARELY see one rod
Normal sensitivity:
The amount of overall gain necessary to CLEARLY see all pins in the TO
Dynamic Range:
The difference btwn gain settings that produce barely seen and max. brightness displays for the same reflection
Dead Zone:
The distance closest to the XDCR in which imaging cannot be performed - NO INFO AREA
Lateral Resolution:
The minimum reflector separation perpendicular to the sound path required for separate reflections to be produced
Axial Resolution defined:
The smallest distance between any two rods in the group that can be seen separately
TO is filled with a mixture of:
Water, alcohol, and algae inhibitor that has a prop seep of 1.54 mm/us at ROOM TEMP
Test object:
composed of material in which the veolicty of the US is the same as tissue (1.54 mm/us) but uses no materials that attempt to imitate tissue characteristics
A wide BW is used to produce a:
short pulse
A hydrophone consists of:
small XDCR elements mounted on the end of a narrow tube or hollow needle
Axial Resolution:
the minimum reflector separation along the sound path required for separate reflections to be produced
Lateral resolution defined:
the spacing of the two closest rods in the group that are seen separately on the display