Ultrasound coupling media: their relative transmissivity.

The relative transmissivities of several commonly used ultrasonic coupling agents were measured to determine if there were significant differences in their effectiveness. Coupling media were evaluated in thin films to simulate clinical use. In order to minimize experimental error in this determination, transmitted energy was measured in the far field of the sonating transducer; the receiving transducer was angled slightly to minimize standing waves; and the sonating chamber was made as anechoic as possible. It was found that there is no practical difference in the transmissivities of the common coupling agents, except that hydrocortisone ointments and creams had lower transmissivities, probably due to microscopically entrapped air. When used as a thin film, absorption of ultrasound in the media was insignificant, and variation in transducer pressure was found to cause differences in energy transmitted greater than those found between the common coupling media. Consequently, it was concluded that coupling media can be chosen primarily on the basis of cost and convenience.

Heat and stretch procedures: an evaluation using rat tail tendon.

This study evaluated various methods of applying force to collagenous tissue at various temperatures to produce permanent elongation, using rat tail tendon as the tissue model. A materials testing machine was used to measure the forces applied and the resulting elongation produced by differing procedures. Short-term vigorous stretching and prolonged moderate stretching were compared at 37 C. The effect of heating tissue prior to applying force was evaluated, and the effect of using a prolonged application of low force was demonstrated. The data showed that the low force, long duration procedure was very effective at producing residual elongation. Elevating tissue temperature and maintaining it prior to applying force was found to cause significantly less damage; and finally, the lower loads applied at elevated temperatures for prolonged periods were found to produce significantly greater residual elongation.