The Main Event
« Multimodal thinking on breast cancer | Main | A closer look at low-light therapy »
Looking for some hot stuff…
Sunday 22.30 PT: Yesterday evening I joined over 500 hard-core biomedical-optics types for what’s become something of a BiOS institution. I’m referring to the Hot Topics session, an annual event that’s renowned as much for its beyond-the-call-of-duty timing (7 till 9.30 p.m. on conference Saturday) as for the masses of factual and quantitative information that speakers are required to cram into a 10-minute speaking slot.
Time - or rather the lack of it - precludes anything like a comprehensive write-up of all the Hot Topics. Instead I’ll focus on a couple of papers that I think showcase the wide-ranging therapeutic and diagnostic potential of clinical photonics.
Rox Anderson, professor of dermatology at the Wellman Center for Photomedicine (Boston, MA), got the session started with a review of the latest advances in therapeutic lasers. He reckons that optical therapies are “poised for huge impact” and encouraged the audience to use BiOS and Photonics West to “network with MDs, heck even talk to me”.
Over the years, Anderson and his colleagues have pioneered all manner of laser treatments - among them selective photothermolysis for the treatment of vascular birthmarks without scarring, as well as lasers for tattoo removal and permanent hair removal. His group is currently working on laser targeting of other skin structures, such as sebaceous glands, sweat glands and fat (see Free-electron lasers: ready to shine on medicalphysicsweb).
Anderson is particularly excited by progress in microbeam laser treatments. Here an array of invisibly small burns (or “little murders”) are delivered to diseased skin tissue in such a way that it is possible to “tune” the depth of the beams. Future applications could include laser-surgery treatment for cancers of the larynx, lung, brain, bladder and breast.
Another area singled out for attention was low-level laser therapy, with Anderson citing impressive results published in the journal Stroke on the efficacy of infrared laser therapy as a new treatment strategy for ischaemic stroke (Stroke 2007 38 1843).
Subsequent Hot Topic papers, in the main, concentrated on the diagnostic capabilities of photonics. Mary-Ann Mycek, associate professor in the department of biomedical engineering at the University of Michigan (Ann Arbor, MI), provided a neat case study with a talk entitled “Probing pancreatic disease using tissue optical spectroscopy”.
Pancreatic cancer is the fourth leading cause of cancer death in the US and has a five-year survival rate of only 4%. The biggest problem is late detection - due in large part to the inaccessibility of the organ, which complicates diagnosis via conventional radiological procedures (e.g. ultrasound, CT and MRI).
Subsequent treatment comprises lengthy and complex surgery, after which many patients turn out to have pancreatitis (a treatable inflammation of the organ) rather than pancreatic cancer. For any would-be optical interrogation scheme, the task is therefore to differentiate a cancerous organ from one affected by pancreatitis.
With this in mind, Mycek and her colleagues have studied fluorescence and reflectance data for normal and diseased pancreas tissue. In what’s claimed to be the first limited pilot study to optically probe freshly excised human pancreatic tissue and in vivo human xenografts in mice, they observed increased reflectance from cancer cells (versus normal tissue and tissue exhibiting pancreatitis).
They’ve linked this behaviour to changes in optical scattering properties caused by the increased size of the cell nucleus in cancerous tissue. “Although the preliminary studies are small, optically detectable biomarkers appear to be consistent with disease progression,” noted Mycek.
The other Hot Topics papers covered a diverse range of subject matter. Specifically:
• Monitoring and predicting chemotherapy using diffuse optics
• Imaging and treatment of cancer using gold nanoparticles
• Photoacoustic microscopy and computed tomography
• Real-time quantitative microscopy on the nanometre scale
• Multidimensional fluorescence imaging
• Single-molecule superresolution imaging and trapping
• Spectroscopy for diagnostic and interstitial photodynamic treatment control.
