Section 3--selected biological properties of tissues: potential determinants of susceptibility to ultrasound-induced bioeffects. American Institute of Ultrasound in Medicine.

Abstract

Although harmful side effects have not been reported in humans associated with the clinical application of continuous wave (CW) ultrasound (typical of therapeutic applications) or pulsed ultrasound (typical of diagnostic applications), bioeffects have been reported in nonhuman mammalian species with both waveforms. Bioeffects have been reported in organ systems that have tissues associated with well-defined gas bodies, such as lung and intestine, and in tissues not associated with well-defined gas bodies, such as nervous tissue, liver, kidney, and reproductive tissues. Lesions in tissues with well-defined gas bodies include hemorrhage in lung and intestine; lesions in tissues without well-defined gas bodies include cell and tissue destruction and necrosis with tissue-specific hemorrhage in nervous tissue, liver, kidney, and reproductive tissues. Studies suggest that there are unique differences in the responses of tissues to CW and pulsed ultrasound among animal species and within a species based on age or stage of development. Data from reference materials covering the anatomy and histology of animal tissues indicate that important structural differences exist among species and within a species based on age or stage of development. These structural differences and how they influence the responses of tissues and organs to ultrasound appear to be focused on the serosal surfaces (protective coverings) of these organs. Such surfaces include, but are not limited to, the visceral pleura of the lung and the visceral peritoneum of all abdominal organs. The thickness and composition (e.g., structural fiber type, collagen, or elastic fibers) of these surfaces and their contiguous internal structural units, such as septa and trabecula, also appear to be important in determining the susceptibility of a tissue or organ to ultrasound-induced damage. Although data exist that support the hypothesis that there are species differences in susceptibility to CW ultrasound-induced lung hemorrhage, data from studies using pulsed ultrasound are less abundant but suggest that species differences in susceptibility to pulsed ultrasound-induced lung hemorrhage may also possibly exist. Species differences in susceptibility to ultrasound-induced lung hemorrhage appear inversely related to the thickness of the visceral pleura of the lung. Although pulsed ultrasound can induce hemorrhage in the intestine of mice, there are no data from intestinal studies currently available suggesting there are species differences in susceptibility to pulsed ultrasound. There exists, for the intestine, information similar to that reported in the lung, which documents innate tissue and organ differences among mammalian species that could influence susceptibility to pulsed ultrasound. The analysis, interpretation, and speculation regarding bioeffects and tissue properties documented in this section and the conclusions presented likely will mature and evolve as new information becomes available through additional in vivo bioeffects research.