Biomedical Engineering Reference
In-Depth Information
glioblastoma [McDannold et al., 2010]. In two patients, tempera-
tures of 48°C and 51°C were achieved. One patient experienced
sonication related pain, and temperatures to induce clear coagu-
lation were not achieved. However, the results show promise for
future use of transcranial FUS for tumor ablation. In the follow-
up study in Zurich, nine patients participated in a study involv-
ing the use of transcranial FUS for the treatment of chronic
pain [Martin et al., 2009]. This study used the InSightec system
improved after the first three patients in Boston. This system had
1024 elements and operated at 670 kHz. Temperatures ranging
between 51°C and 60°C were achieved, producing precise lesions
(3-5 mm diameter) visible on MRI after 48 hours. Initial pub-
lished results from the study were positive, showing good pain
relief levels (30-100%). However, long-term follow-up data have
yet to be published.
acknowledgments
The authors would like to thank Dr. Junho Song and Robert
Staruch for their contributions to Figures 14.2 and 14.7. This work
was supported by grant No R01 EB003268 from the National
Health Institute and the Canada Research Chair program.
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14.5 potential Future treatments
Transcranial FUS has great potential for future use in brain can-
cer treatments. Ideally, the coming years will see an increase in
the number of tumor ablation studies performed worldwide. The
advancement of BBB disruption into clinical practice has great
potential to revolutionize the treatment of not only brain cancer
but of a range of neurological disorders. Delivery of therapeutics
would be more beneficial for the treatment of diffuse metasta-
ses than ablation, which is best suited for localized treatments.
Additionally, BBBD procedures would be capable of targeting
regions close to bony structures without the same concern for
skull heating as in ablative procedures. A combination of treat-
ments, as suggested by McDannold et al. [2006b] could pro-
vide the most powerful treatment tool. Tumor centers could be
ablated using high intensities, while treating the periphery of the
tumor using BBBD to deliver chemotherapy agents.
14.6 Needs for advancement
of transcranial FUS into
routine Clinical practice
The advancement of transcranial FUS into routine clinical prac-
tice currently faces several obstacles. Long-term follow-up to
initial clinical trials is necessary to establish the safety of the
procedures. Most importantly, transcranial FUS requires a real-
time monitoring technique to provide information on treatment
progress. MR-thermometry can provide information about
thermal effects. However, monitoring of the acoustic field is nec-
essary to ensure safety. The ExAblate 4000 allows a few elements
to be used as passive cavitation detectors during therapy. Ideally,
a larger receiver array would be integrated into the therapy array
to allow passive imaging of cavitation events. This is especially
important if BBBD is to be implemented clinically, as knowledge
of the microbubble interactions with the acoustic field is neces-
sary to ensure that cavitation events are not occurring outside
the focus. Continued research interest in the field will help refine
the technology and push transcranial FUS into the clinic.
