Needle tip echogenicity. A study with real time ultrasound.
During ultrasound-controlled biopsy, the visualization of the needle tip is essential for its exact guidance. We constructed a testing device to simultaneously measure the needle tip echo (NTE) intensity of several needles. The following needle parameters were studied: the angle of incidence, the needle diameter, the needle tip bevel angle, and the orientation of the needle tip opening to the transducer. Measurements were made in A-mode using the highest amplitude peak of the NTE and in B-mode using the gray level histogram map from a fixed area around the NTE. There was a positive linear correlation between the intensity of the NTE and the angle of incidence in A-mode as well as B-mode. In A-mode a similar linearity was found between the NTE and the needle diameter, which in B-mode was exponential. However, the needle tip bevel angle did not affect the NTE. Rotating the needle around its longitudinal axis rendered the highest echo at an orientation of 180 degrees from the transducer in A-mode as well as B-mode.