in plane and out of plane needle approaches in Ultrasound guided interventions
“In plane” and “out of plane” are two basic approaches to freehand US-guided procedures, which refer to needle trajectory relative to the transducer and sound beam.
With an in plane approach, the needle is directed under the long axis or parallel to the footprint of the transducer and nearly perpendicular to the direction of the incoming sound beam.
This results in not only the needle tip but also the entire needle being visualized at all times throughout the duration of the procedure. This is the preferred method because it allows the operator to make real-time corrections for angle and depth. This approach also minimizes mistargeting complications and maximizes accuracy by enabling visualization of the entire needle path.
The out of plane approach refers to passing the needle perpendicular to the transducer, resulting in the needle passing through the plane of the sound beam. This technique is more difficult to master because the operator is only able to visualize a short segment of the needle at any one time, and the depth of the needle tip is not always immediately apparent to the operator. This technique is useful for small joints with a small surface area.