To evaluate if pericardium is a suitable calibration reference in the integrated backscatter (IBS) analysis, the grossly normal pericardial specimens from 23 patients without a history of pericarditis were mounted on a steel platform and immersed in a 0.9% saline bath. The 2-D IBS images acquired at the uniform time gain compensation settings of 50 and 70 dB were analyzed. For the pericardial IBS, the limits of agreement for intraobserver and interobserver measurements were -1.2 to 1.4 dB and -1.6 to 2.2 dB, respectively. However, the calibrated IBS intensity of the pericardium presented a rather wide range of variation and was -13 +/- 5 (-5 to -29) and -10 +/- 4 (-4 to -22) dB at the overall gain settings of 50 and 70 dB, respectively. Conclusively, pericardium may not be an ideal IBS calibration reference in a population study of cardiac tissue characterization.