Attenuation coefficient estimates of mouse and rat chest wail

Attenuation coefficients of intercostal tissues were estimated from chest w alls removed postmortem (pm) from 41 6-to-7-week-old female ICR mice and 27 10-to-11-week-old female Sprague-Dawley rats. These values were determined from measurements through the intercostal tissues, from the surface of the skin to the parietal pleura. Mouse chest walls were sealed in plastic wrap and stored at 4 degreesC until evaluated, and rat chest walls were sealed in Glad-Lock(R) Zipper(TM) sandwich bags, and stored at -15 degreesC. When evaluated, chest wall storage time ranged between 1 and 2 days pm for mice and between 41 and 110 days pm for rats. All chest walls were allowed to eq uilibrate to 22 degreesC in a water bath prior to evaluation. For both mous e and rat intercostal tissues, the estimated frequency normalized attenuati on coefficient was 1.1 dB/cm-MHz. In order to determine if there was an eff ect of storage time on estimates of attenuation coefficient, an independent experiment was conducted. The intercostal tissues front six mouse chest wa lls were evaluated at three time points (1, 22, and 144 days pm), and from six rat chest walls were evaluated at four time points (1, 22, 50, and 125 days pm). There was no difference in the estimated intercostal tissue atten uation coefficient as a function of time postmortem.