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In-vitro visualization of biopsy needles with ultrasound: a comparative study of standard and echogenic needles using
1Department of Clinical Radiology, North Bristol NHS Trust, Southmead Hospital, Bristol, U.K.
Aim:
To demonstrate the circumstances where echogenically enhanced biopsy needles confer an increase in visualization during ultrasound-guided biopsy using an in-vitro experiment.
Materials And Methods:
An experiment using both standard and echogenically enhanced needles was conducted in a purpose built interventional phantom. The needle tip echogenicity and shaft visualization was recorded at different angles (20 and 60 degrees ) between the ultrasound probe and needle. The needle tip echogenicity was also recorded in four different angles of bevel rotation. The experiment was performed using a total of 18 different needles of 18 and 20 gauge.
Results:
The experiment confirmed some previous findings. The needle was better visualised at an angle of approximately 60 degrees to the probe. The needle tip was optimally visualized with the bevel facing the transducer or 180 degrees to it. Needle tip movement improved conspicuity. Using an optimal angle of approach (60 degrees ) the use of an echogenic needle did not confer any increase in conspicuity. If the transducer to needle angle was suboptimal (20 degrees ) then there was increased visualization of some echogenically enhanced needles.
Conclusion:
Optimisation of the conditions prior to ultrasound-guided needle biopsy will increase the visualization of the chosen device thus aiding the interventionalist. Needle gauge, bevel position, movement of the needle and the probe to needle angle all affect conspicuity. Needle coating or roughening does not improve tip visualization if the angle between the needle and probe can be optimized (60 degrees ). In unfavourable situations when the angle is suboptimal (20 degrees ), we have shown that echogenic enhancement of the needle tip can make it more visible.