Abstract
Collagenous tissues, like tendon, are resistant to fractionation by focused ultrasound (fUS). Prior work has shown thermal pretreatments increase susceptibility to fractionation by fUS, suggesting the potential for successful fractionation by tuning boiling histotripsy parameters. Here, we investigate the roles of pulse length (PL) and duty cycle (DC) on fUS treatments of tendinopathic tendons. Ex vivo bovine tendons were injected with collagenase to induce tendinopathy. The following day, tendons were treated for 15– 20 min with 1–3 MHz fUS (p;+ ≤ 127 MPa/p;− ≤ 35 MPa). Three PLs were chosen below, slightly above, and well above the calculated time-to-boil. The pulse repetition frequency varied between 0.2–1 Hz, allowing for evaluation of DCs between 0.1% and 0.8%. Preliminary results show focal fiber separation at the PL slightly above the calculated time-to-boil; areas of tissue disruption are smaller and less frequent for the other PLs and accompanied by thermal damage at the highest PL. As frequency increases, the tissue disruption becomes smaller and infrequent for the lowest and highest PLs. When the PL was held constant, minimal change in tissue fractionation was found when changing DC. Thus, for the tested combinations, PL is more influential than DC for tuning the fractionation of tendinopathic tendons. [Work supported by NIH RO1EB032860.]
Published Version
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