QA Flashcards
A longitudinal view of the right lobe of the liver was obtained using a portable scanner.
a) What is the cause of the band-like pattern in the bottom half of the image?
b) Is it possible to reduce or eliminate the appearance?
The pattern is due to electrical interference. b) If the problem is particularly offensive, the operator should check for the presence of nearly electrical appliances. Switching off tissue harmonic imaging can also help because fundamental signal is generally of greater amplitude which will improve the signal to noise ratio. Electrical interference may also be a sign of malfunctioning internal components of the system. The operator could restart the system and check for the presence of interference in a variety of locations. If persistent, the system will need servicing.
An image and internal schematic of a typical tissue equivalent phantom is shown below. Describe how this device could be used to test the axial and lateral resolution of an ultrasound system.
Axial and lateral resolution pins are provided on the phantom. The spacing of these pins is known and is provided in the phantom. If the pins can be resolved as separate, spatial resolution is better than this value. If the pins cannot be resolved as separate, spatial resolution is worse than this value. Another method is to measure the dimensions of certain pins in the axial and lateral direction. Calibration pertains to the accuracy of distance measurements on the screen. It is advantageous to test calibration over large distances. The reason for this is simple. Placement of a caliper is always associated with some degree of operator error. This error is relatively large (as a percentage) if the distance measurement is small. Uniformity can be tested as equal echogenicity across the image visually. Another uniformity test is also known as a “dead element test” and this involves applying a small amount of gel to the surface of the transducer and then running a finger over the transducer. This test easily demonstrates malfunctioning elements as hypoechoic vertical stripes originating from the transducer surface. No matter what quality control test is being performed, it is very important to always reproduce the test using the same machine, same transducer with the same preset on the same phantom.
For routine uniformity assessment (in-air reverberations), it is important to:
Turn off all advanced processsing
Regarding QA checks, what recommendation can be made when transducers are moved between departments?
Return the transducers to their original machine for testing.
