Figure 3: (a-b) In vitro acoustic testing of magnetic microbubbles under B-mode imaging. A region of interest (ROI) within the sample holder is shown by the red dotted box. B-mode images for the sample holder containing (a) water, (b) 10 % by volume magnetic microbubbles (MMB). (c-d) In vitro acoustic testing of magnetic microbubbles under focused ultrasound excitation. B-mode images with passive acoustic mapping (PAM) overlay showing maps of source power for (c) water, (d) 10 % by volume MMB.