Key Points
- A preclinical study helped researchers understand how cellular-level changes from brain histotripsy appear on MRI.
- The team used the data to create a library of MRI images correlating with histological findings.
- The library can be used to monitor histotripsy treatment response and detect any potential damage.
Zhen Xu, PhD, and her research team at the University of Michigan recently published a preclinical study designed to help understand how cellular-level changes from histotripsy applied to brain tissue and brain tumor tissue appear on MRI images. The data, which the team used to create a library of MRI radiological features correlating images with histology, can then be used to monitor treatment response to histotripsy and detect any potential damage from treatments.
“This study revealed that histotripsy produces unique radiological features that are different from what is seen with traditional neurological therapies, including transcranial focused ultrasound,” said Dr. Xu. “The effects of the transcranial histotripsy, such as mechanical cellular breakdown, were immediately visible on MRI. This is a stark contrast to radiosurgery lesions, which do not show on MRI until a month after therapy. Histotripsy produced acute, localized bleeding that safely resolved within a week of treatment.”
The group used an eight-element histotripsy transducer to treat 18 normal mice and nine from a glioma model then collected several types of MRI images and corresponding histology samples up to 28 days after treatment (limited to days 0, 2, and 7 for the glioma models due to the aggressive tumor growth of the model and expanded to days 14, 21, and 28 for the normal mice). They found the T2* and T2 images to be especially useful for determining each treatment zone created by the application of histotripsy. Because histotripsy induces minor localized bleeding, the team determined that both T1 and T2 images could be used to determine the evolution of blood products over time. T1-gadolinium (T1-Gd) images were helpful for determining residual tumor volume and the state of the blood-brain barrier (BBB).
The chart below summarizes the research team’s recommended findings:
To Monitor
Edema or inflammation
The histotripsy zone
Blood product evolution
BBB disruption
Use this MRI Sequence
T2 then T1-Gd
T2* then T2
T1 then T2
T1-Gd
The development of such predictive imaging biomarkers will more rapidly advance the use of histotripsy for brain tumors and other serious neurological conditions. This work was funded by the National Institutes of Health and the Focused Ultrasound Foundation.