Editors' ChoiceCancer Imaging

A Big Step Forward for Tiny Particles

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Science Translational Medicine  25 Apr 2012:
Vol. 4, Issue 131, pp. 131ec73
DOI: 10.1126/scitranslmed.3004181

Surgical removal of brain tumors is often the only curative approach. Because remaining cancer tissue may spur relapse of disease, neurosurgeons are in a tight spot: On one hand, the cancerous tissue should be removed in its entirety; on the other, removal of healthy brain tissue can cause neurological deficits. Hence, the surgeon walks a fine line, trying to remove all of the cancerous tissue without compromising healthy brain. A recent nanoparticle developed by Kircher et al. may make this fine line bolder, by helping surgeons to clearly delineate tumor margins in mice with glioblastoma.

The authors created a new nanoparticle, with a size of around 100 nm, a gold core, and a silica shell, that could be detected in the brain using three different modes of imaging: magnetic resonance (MR), photoacoustic, and Raman. The nanoparticles passively accumulated in tumor tissue in the brains of mice shortly after intravenous injection. Kircher and colleagues first used the particle's gadolinium content to image the cancer by MRI, as is often done in the clinic to plan therapy. Then, during surgery, photoacoustic imaging excited particles with a laser and recorded resulting ultrasound waves that originated from the particles, improving on penetration depth and resolution of standard fluorescence tomography. Raman imaging targeted the active outer layer of the particle. Both photoacoustic and Raman modalities were used to guide brain tumor resection, and detected very small amounts of leftover cancer tissue in the surgical field.

Overall, the work reflects the trend towards multimodal and multiscale solutions to overcome the physical limitations of specific imaging modalities. In this study by Kircher et al., the same trimodal nanoparticle was detected in presurgical staging, during surgery, and by histology in removed tissue. It is still a long way for clinical approval of these particles, which will also require careful toxicity studies. Nevertheless, for neurosurgeons and their patients, using tiny particles could make a big difference.

M. F. Kircher et al., A brain tumor molecular imaging strategy using a new triple-modality MRI-photoacoustic-Raman nanoparticle. Nat. Med. 15 April 2012 (10.1038/nm.2721). [Abstract]

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