On the physics of ultrasound transmission for in-plane needle tracking in guided interventions

Abstract

Objective. In ultrasound (US) guided interventions, the accurate
visualization and tracking of needles is a critical challenge, particularly during in-
plane insertions. An inaccurate identification and localization of needles lead to
severe inadvertent complications and increased procedure times. This is due to
the inherent specular reflections from the needle with directivity depending on the
angle of incidence of the US beam, and the needle inclination. Approach. Though
several methods have been proposed for improved needle visualization, a detailed
study emphasizing the physics of specular reflections resulting from the interaction of
transmitted US beam with the needle remains to be explored. In this work, we discuss
the properties of specular reflections from planar and spherical wave US transmissions
respectively through multi-angle plane wave (PW) and synthetic transmit aperture
(STA) techniques for in-plane needle insertion angles between 15-50°. Main Results.
The qualitative and quantitative results from simulations and experiments reveal that
the spherical waves enable better visualization and characterization of needles than
planar wavefronts. The needle visibility in PW transmissions is severely degraded
by the receive aperture weighting during image reconstruction than STA due to
greater deviation in reflection directivity. It is also observed that the spherical wave
characteristics starts to alter to planar characteristics due to wave divergence at large
needle insertion depths. Significance. The study highlights that synergistic transmit-
receive imaging schemes addressing the physical properties of reflections from the
transmit wavefronts are imperative for the precise imaging of needle interfaces and
hence have strong potential in elevating the quality of outcomes from US guided
interventional practices.

Tips and tricks in ultrasound-guided musculoskeletal interventional procedures

“…Fortuitously, needles are excellent specular reflectors (20,21) , making them conspicuous on US images, but the more acute the angle of insonation from the transducer upon the needle, the less signal is detected and rendered on the image. Therefore, the best visualization is afforded by in-plane views, where the sound beam reflects off the needle at a ninety-degree angle (Fig.…”

“…Heel-toe maneuvering of the transducer or use of sonographic systems with beam steering capabilities may be useful to maximize the reflected signal from the needle. Specialized reflective needles with surface alterations or echogenic tip coatings designed to accentuate the reflection of the needle may be useful but are generally not necessary for most USguided interventions (20)(21)(22) .…”