Background

Focused ultrasound (FUS) is a minimally invasive method for tissue ablation, particularly for cerebral functional procedures. FUS was FDA approved in July 2016. Medicare approved nation-wide use as of July 12, 2020. Bone infarcts are an underrecognized adverse effect of ultrasound-guided tissue ablation; to our knowledge, not discussed in radiology literature. How does FUS Work? Focused sound waves from ultrasound transducer which generates heat at a single point within the body to destroy target tissue. MRI is frequently used to plan treatment and monitor degree of heating during the procedure. Benefits of FUS: Minimally invasive, reduced risk of infection, no use of ionizing radiation. Known Side Effects of FUS: Sensory disturbance, gait disturbance, headache, pain, dizziness.

Objective

Teaching Points: Focused ultrasound (FUS) offers a minimally invasive method for tissue ablation, first reported in the 1940s. Multifocal calvarial bone infarcts are an underrecognized side effect of ultrasound-guided cerebral tissue ablation, and commonly an incidental finding following ablation.

Methods

Several patients have been identified at our institution who have undergone FUS and consequently developed bone infarcts.

Results

We collected pre- and post-procedural imaging to illustrate the effects following FUS.

Conclusions

Very characteristic appearance on MRI: “Leopard skull appearance”: centrally T1-hyperintense lesions with serpiginous T1-hypointense margins, typical of bone infarcts.