Feature
Breaking down histotripsy
Inside a new ablation modality with cancer applications By Fred T. Lee, MD, Timothy J. Ziemlewicz, MD, Zhen Xu, PhD, and Paul Laeseke MD, PhD
W
ith ever-evolving technologies, cancer treatments will almost certainly become more
effective and less invasive in the future. A new procedure that will likely play an important role in the future of interventional oncology is histotripsy. Histotripsy (Greek for “tissue” and “breakdown”) is a noninvasive focused ultrasound method that mechanically breaks down soft tissue.1 Since first being used to create atrial septal defects in a canine model, the technology has been applied to a variety of tissues in animal models, including liver, kidney, thyroid, prostate,
12 IRQ | FALL 2021 vessels, brain, fat and the heart.2,3 In
addition, histotripsy has been used to treat the prostate and liver in humans.3,4
Though the initial applications for histotripsy were focused on the mechanical destruction of normal or benign tissues, promising early local and systemic effects after treatment indicate that the greatest application will likely be in the treatment of cancer. What ties histotripsy to interventional oncology is the critical role that imaging plays at every step of the process, from planning to treatment monitoring and posttreatment assessment. While the procedure could be adopted by a
variety of specialties, we believe that interventional oncologists are well- positioned and best equipped to lead the introduction and clinical translation of this new technology.
What is histotripsy? Histotripsy was invented at the University of Michigan department of biomedical engineering more than a decade ago by Charles Cain, PhD, Timothy Hall, PhD, J. Brian Fowlkes, PhD, William Roberts, MD, and Zhen Xu, PhD. Histotripsy is the first nonthermal, nonionizing and noninvasive ablation modality guided by real-time imaging of the treatment effect. Histotripsy works by focusing ultrasound energy from an external treatment transducer to a point in the body to create cavitation. A robot then translates the ultrasound beam throughout the selected treatment volume to create an ablation zone of any size and shape. While bearing superficial similarities to high-intensity focused ultrasound (HIFU), histotripsy uses different pulse sequences (high amplitude, much shorter pulses, low ultrasound on-time)
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