THE EFFECT OF STORAGE TIME AND REPEATED MEASUREMENTS ON THE ELASTIC PROPERTIES OF ISOLATED PORCINE AORTAS USING HIGH-RESOLUTION X-RAY CT

A Laboratory CT scanner with a resolution of (0.1 mm)(3) was used to d etermine if storage up to 7 days in saline at 4 degrees C and (or) rep eated measurements would alter the compliance, C, and incremental elas tic modulus, E-inc, of isolated porcine aortas. All specimens were obt ained fresh, made pressure-tight, and then mounted in the scanner, wit h humidified air used to produce adequate x-ray contrast. The specimen s were imaged at pressures of 4, 8, 12, 16, 20, and 24 kPa, and vessel measurements were then obtained with a computerized technique and ana lyzed. Seven thoracic aortas were studied on days 0, 3, 5, and 7, with a significant change (p < 0.05) in compliance first occurring after t hree imaging studies (i.e., day 5). Compliance of the fresh thoracic a ortas (mean +/- SD) was 0.90 +/- 0.28 mm/kPa at 14.4 kPa and 0.85 +/- 0.31 mm/kPa at 22.5 kPa. Six thoracic aortas were studied only on days 0 and 6 with no intermediate measurements. They showed no change in e ither compliance (0.88 +/- 0.07 mm/kPa at 14.4 kPa and 0.64 +/- 0.09 m m/kPa at 22.5 kPa) or E-inc (0.46 +/- 0.05 MPa at 14.4 kPa and 0.88 +/ - 0.15 MPa at 22.5 kPa) from day 0 to day 6. Thus, number of measureme nts rather than time appears to be the important factor. Six abdominal aortas were studied similarly but on days 0, 3, and 6. No significant change occurred in compliance (0.15 +/- 0.06 mm/kPa at 14.4 kPa and 0 .032 +/- 0.026 mm/kPa at 22.5 kPa) but E-inc showed a change, possibly due to their viscoelastic properties. We conclude that this nondestru ctive CT measurement method is suitable for repeated studies on porcin e thoracic aortas, but not abdominal aortas, if the measurement involv es two consecutive imaging sessions separated by no more than 6 days.