Abstract

OBJECTIVE
We assess the usefulness of an animal model, the axolotl (Ambystoma mexicanum) in comparing 3D ultrasound (US) and plain film x-ray images.

METHODS
Hindlimbs were amputated from five animals, at either the zeugpodial or stylopodial level and each regenerating limb was imaged 16 times with 3D, US and 14 times with plain film x-ray over 315 days. For 3D US, a 10 MHz linear array probe was translated via motor-driven stage whilst images were digitised. The 3D images were reviewed using MacCubeView.

RESULTS
3D US visualised the regenerating tibias and fibula bones an average of 70 days earlier than x-ray, while regenerating phalangeal bones were detected by 3D US an average of 25 days earlier. After 120 days, both imaging modalities consistently showed the bones. The average bone growth rates for the tibia and fibula were 0.019*0.003 and
0.019*0.003 mm/day respectively. Regenerating blood vessels were more easily visualised on real-time B-mode than on colour Doppler.

CONCLUSIONS
Regenerating axolotl limbs are easily imaged by US and provide the opportunity to image bone and cartilage from their initial points oforigin, thus serving as an ideal model for future studies of cartilage and bone formation.

Presented: AIUM (American Institute of Ultrasound in Medicine) annual convention in San Antonio, Texas - March 14-17, 1999.