Ultrasound B-mode 360° tomography in mice

Cross sectional B-mode images were acquired from dead mice at projections through 360°. The image set was rotated about the isocentre and a set of aligned images produced. These were averaged to form a compound image. The compound images show a dramatic improvement in image quality over individual B-mode images; with much reduced speckle (2% compared with 18% in the B-mode image), and reduction in artefacts. Organs such as kidney and stomach are visible, along with skeletal anatomy. This demonstrates that the mouse skeleton does not have the same deleterious effect on the ultrasound beam as that of the human skeleton. This is probably due to the closer matching to soft tissue of acoustic properties of the cartilaginous skeleton of mice, as opposed to the high mismatch of the heavily calcified human skeleton. B-mode 360° compound imaging may he of interest as the basis for a new 3D technique providing high quality ultrasound images which are much less dependent on operator skill than is the case for real time B-mode ultrasound. A further development worth pursuing is tomographic reconstruction from projections.