3) Never do sideways movements inside the patient (the angle of the needle can only be changed in the very subcutaneous tissues). Doing a sideway movement with the needle runs the risk of the bevel of the needle cutting an umbilical artery. This is the only emergency C-section that this radiologist ever ordered while guiding a young resident !The phantom makes it easy to recognize when the student pulls the needle sideways, as the bevel will cut in the gelatine and leave a clear mark! Same marking happens if the student pulls back the needle with the stylet not properly locked on the needle. Bubbles are drawn in the needle path and leave a clear mark.
4) Aim for a large (2-3 cm) target and get the student to insert the needle into the target. The student as to learn to 1) image the target, 2) rotate the transducer until the safest path to the target is imaged, and 3) insert the needle in the exact plane the transducer has defined. The needle should be visible after the first 2-3 cm in the phantom and remain constantly visible after. Note that since the phantom is fairly stiff, a lot of gel is needed to couple the edge of transducer to the phantom.
If the needle goes “below” the target, pull back (but not out) and oblique the needle more horizontally, it if goes “above” the target, pull back (but not out) and angle the needle more vertically. Be careful to NOT bend the needle!5) The finale step is to practice aiming for smaller and smaller structures and practice until very familiar.
A few more tips:
When all these steps are mastered, teach the student that when inserting a needle they should neither go too fast (loose the tip of the needle) or too slow (as this could cause tenting of the membranes-red arrows in the picture-).