Fig. 2

Phantom. Feature demonstration (a–d); construction steps (j–l). a Acrylic box with scribed lines (arrow) for scanner laser alignment. b Black blind to prevent observation during biopsy. c Plate with hemispheres for well impressions. d Plate in position, with flanges (arrow) to keep stamp 5 cm from base. e 1:10 gelatin:water, heated to 50 °C in a water bath. f Stamp in position, making wells in the half-filled gelatin as the gelatin cools. g Stamp removed, leaving wells (arrow) in the set gelatin in which the targets rest. h Two hemispherical domes form each sphere, with a 2-mm hole (arrow) in the apex of one of the domes which accommodates an 18-G needle for injection filling of target material. i Formed target spheres, filled with coloured gelatin/agar mix. Red, blue, and black food colouring for 3-, 2-, and 1-cm targets, respectively. j Spheres resting in wells. k Complete phantom, with gelatin filled to the top and surface stickers on the side of the phantom for orientation (arrow). l Phantom with biopsy needle in situ, with surface markers for confirmation of orientation (arrow)