Figure 3c. In vivo US images of a forearm dialysis fistula. (a) Representative directly scanned US image from the 3D data set shows a transverse cross-section of the fistula (f), with scanning performed perpendicular to the top of the image. A refractile artifact (r) is seen to arise from the edges of the fistula. The white line at top indicates the plane of the reconstructed image in b, and the white line denoted with the curved arrow indicates the plane of the reconstructed image in c. (b) Coronal US image of the fistula (arrowheads), reconstructed as if scanned perpendicular to the right side of the image in a at the level of the white line, demonstrates the curved course of the fistula through the forearm. (c) Coronal US image reconstructed at the level of the white line denoted with the curved arrow in a, but deeper into the soft tissues than in b, so that the reconstructed image includes only the refractile artifacts (r) (the two concentric hypoechoic rings) and does not contain any portion of the fistula. These concentric hypoechoic rings would not be present on a directly scanned coronal image (not obtained in this case because of the difficulties imposed on direct scanning by the geometry of the forearm).