Cancer: Marker, Laser, Destroy!

24. October 2007

Conventional imaging processes such as CT or MRI are gaining an important ally in cancer detection: By means of a laser, the researchers succeeded in detecting tumor cells in the blood of the patients without taking blood. The ray scanned the surface of veins - and found what otherwise remains concealed.

The method developed at thePurdue's Cancer Center in co-operation with the MayoClinic tantamounts to a revolution: a so-called 2-photone-microskope detectseven single circulating cancer cells – a complete novelty.

So far single tumor cells were mainly detected in taken blood samples which entailsone significant disadvantage: Particularly in the early stage of cancer thenumber of malign cells is extremely low. “If we have just two carcinogeniccells per 50 milliliter of blood, chances are slim that we will detect them ina regular 10ml blood sample” explains Professor Ralph C. Corley, teachingchemistry at Purdue University, the preliminary disadvantages of cancerdiagnosis via blood samples.

Exactly this is the weak spot the so-called 2-photon laser method of the USresearchers is bypassing. Because circulating tumor cells can be made visibleby means of certain fluorescence markers if a laser beamof a fixed definedwavelength hits them. The physicians were able to equip prostate-, ovary-,kidney and lung cancer cells with that telltale “coating”. The lethal cellscannot hide any more once marked like that.

Make the tumor cells shine

After all, 100 milliliterper minute of blood is running through the patient's veins – enough to enablethe laser scanning the surface up and down 1000 times per second to lookinside. At this very moment it comes to the key process of the noveldiagnostics: The previously marked tumor cells light up on impact of the photons.As deep as 100 micrometers the optical guards penetrate the vein surface. Thesignal registered there can be transferred to a connected computer and bevisualized – the process detects even the tiniest tumors below the CT-criticalrange of one millimetre diameter. The idea to detect cancer in time by means oflaser-fluorescence is not brand new. Already in 1989 the Defense Technical InformationCenter (DTIC) which is part of the US Navy, referred with reference number ADA205222to a then seemingly visionary document: “Cancer Diagnosis by Laser Spectroscopy”.In this document researchers described the difference between breast cancercells and their healthy counterparts – and recognized that both variations canbe distinguished by using markers and laser beams. This publication enthralledbioradiologists of the US Navy, but its medical relevance caused them to take astep rather unusual for the American military: They did not classify the paperas secret but gave the status “Approved for public release”.

Physicians discover Terahertz-beams

Betweenthen and now a lot has happened in laser diagnostics. The use of so-called Terahertz-systemsis considered as particularly promising here as well. Scientists apply a2-color laser because this laser also used in CD players supplies two specificwavelengths, their differences lie in a Terahertz range. This way two coloredlight beams can be filtered out which are afterwards redirected towards theirinitial point, a laser diode. Having arrived there, they build the so-calledtera-wave which at last via several steps pours out as the diagnostic relevantTerahertz-light.

This beam is able to penetrate tissue – thus making marked tumor cells shine. Theoretically.Because in practicalexperience, the procedure shows an enormous disadvantage: The waves reactextremely sensitive to water during the tests – not a good precondition to takea look at the inside of the body. In 2005 scientists still considered themethod brilliant but especially in the oncology field not matured yet. The factthat transatlantic medical researchers announced a breakthrough, although in amodified form and for now not applicable in clinical routine yet – doesastonish at any rate – but comes as anything but a surprise for insiders.

Big playerson the market have seen the potentials of optoelectronics, which includeslaser-based diagnoses, long ago. For example the traditional company Carl Zeiss , located in Jena,has massively enlarged their microscopy department during the present businessyear. Early March 2007, the Thuringian company took over the instrumentbusiness of Clarient, Inc. in the Californian town of Aliso Viejo. The venture was no coincindence as theThuringians informed a short while ago: “Due to the acquisition newopportunities for growth present themselves to Carl Zeiss MicroImaging on thepromising market of clinical cancer diagnostics and -research”.

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