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biomedic engineering

A laser in the interior of the human body

A catheter of optic fibers identifies and cures heart diseases and cancer

Concentrated light, known as a laser beam, is being prepared to take on another use in medicine. After having conquered, for example, surgery on the eye and varicose veins, the advance now is in the interior of the human body as an assistance in the diagnosis and treatment of heart diseases and even of cancer in the mucous areas of the digestive tract and in the respiratory organs. The technology to reach these uses is being developed throughout the world, including in Brazil where, in São José dos Campos, a catheter of optic fibers which transports laser light inside arteries, was developed at the Research and Development Institute (IPD) of the University of the Valley of Paraíba (Univap), under the coordination of professor Renato Amaro Zângaro, Director of the School of Health Sciences.

The instrument allows the laser light to identify and to recover possible clogged arteries and eliminate tumors in a fraction of a second. Ready and tested in the laboratory and on animals, the catherer awaits the beginning of tests on humans.

The project Fiber Optic Catherer for the Diagnosis of Arteriosclerosis Plates in the Cardiovascular System is being carried out in partnership with Tecnobio, a company specializing in the manufacture and distribution of medical equipment. The initiative is part of the Partnership Program for Innovative Technology (PITE) of FAPESP. The financing of the Foundation to the University was R$ 129,000 and that of Tecnobio towards the project was R$ 150,000.

The new technique was conceived, in principle, to substitute the traditional catheterization, an examination for the diagnosis of obstructions in coronary arteries. It consists of a fiber optic catheter with lateral vision coupled to a spectroscope, a device that emits light and allows the doctor to minutely evaluate the conditions of the arterial tissues. Using it, one can identify small cellular changes and the formation of atheromas – deposits of fatty material in the arteries -, whose evolution could obstruct the passage of blood, causing a infarct of the myocardium. The facilitator of a precocious diagnosis, the new catheter also permits that, during the same procedure, the laser can be switched on to treat the affected area, pulverizing the material that has accumulated there.

Double action
Besides the catheter for coronary diagnosis, Zângaro coordinated another project that resulted in innovative technology of the catheter developed at Univap. With a slight modification at the tip, the catheter was adapted for the diagnosis of cancer in the rectal colon. The emission of the laser and the collection of the response given off by the tissues, are done using a spectrofluorometer, equipment also developed at Univap, through the financing of FAPESP, in the field of assistant research program, through the project Multilines Spectrofluorometer for the Precocious Diagnosis of Cancer.

With the collaboration of the Cancer Hospital where 30 patients took the new examination, the equipment presented excellent results according to Zângaro. The possible advantage of the new system will be the elimination of the biopsy examinations, no longer being necessary to remove a sample of the tissue of the patient to obtain a complete diagnosis.The new apparatus shows the results immediately through graphs which demonstrate the presence of porphyrins (fluorescent substances), normally present in cancerous tissue. If there is a tumor, for example, the difference between the frequencies of this sick tissue and of a normal tissue will shown up on the graph.

Diagnosis and treatment
In the heart examination, the catheter can also analyze the nature of the deposited material on the arterial wall and identify the various stages of the development of an atheroma. With the laser it would be possible to make a diagnosis which localizes and analyses the obstructions without the necessity of looking at the arteries via x-rays, as it is done today, through an injection of a substance which presents a contrast in the blood stream.

The equipment used in the new test is the Raman spectroscope, an apparatus which collects data for biochemical analysis of tissue in vitro. “When linked to the fiber optic catherer, this analysis of the tissue can be done directly on the patient, with instantaneous results”, explains Zângaro.

The medical procedures for the diagnosis are similar to catheterization but the results are much more precise: the equipment allows for the identification of which molecules are present in the atheroma. According to the researcher, this brings a large benefit to the doctor, who can determine the treatment according to the material observed, including shooting the laser to remove possible obstructions.

This atheromas destruction procedure, called ablation, promises to be more efficient than the one currently in use. According to the researcher, the laser pulverization is capable of reducing the atheroma to minute particles, eliminating the risk of an obstruction at some point further on inside the artery as it can occur with the usual rotor ablator which functions in a similar form to a triturator. Zângaro explains that the diagnosis by laser can also avoid another type of accident. “During the catheterization, the simple introduction of the catheter can be enough to dislocate a thrombus or a clot, provoking a serious obstruction. However, with the fiber optic catheter this can be avoided, as it permits one to see and to pulverize a clot before the passage of the catheter”, says.

A coronary examination is not something simple. In general, the procedure involves considerable risk that needs to be reduced to the minimum. For this reason only the project of the development of the catheter ran into some difficulties. The first of them was in relation to flexibility.

High risk
“The catheter needs to be very flexible so as not to damage the walls of the artery, which could provoke an inflammation in the region,” explains Zângaro. It is composed of seven fibers: one central, which takes the laser to the tissue, and six surrounding, which collect the light response emitted by the tissue. The technology of the assembling – joining together of the fibers, gluing and covered with polyurethane – was part of the partnership with Tecnobio.

Another difficulty of the project was to pick out, in the types of fibers existing on the market normally used in telecommunications, the ones which present the highest level of purity. Produced in silicone, the fibers presented impurities which interfered with the collecting signal of the apparatus. These “noises” could mask the reading of the signal emitted by the tissue, jeopardizing prejudicing the diagnosis.

Although these difficulties have been overcome and the project of the catheter has been concluded, some questions still remain to be resolved so that the equipment can comply with its purpose in medical clinics. From the operational point of view, the interval between the processing of the diagnosis and the ablation cannot go beyond 0.5 seconds, the time that the catheter is capable of maintaining itself in the same position within the artery. Beyond 0.5 seconds the catheter can move itself, pushed ahead by the blood pressure, creating the situation where the ablation laser doesn’t reach the desired point.

Furthermore, the treatment also requires a vigorous control of the strength of the ablation. To determine the exact quantity of energy to be launched at the tissue, there is a parallel study under way at the Ablation Laboratory of IPD of Univap, also with the support of FAPESP. Various tests are necessary to evaluate the effect of different pulse strengths of the laser on biological tissue and as well to verify the behavior of the material resulting from the ablation.

Test on humans
Due to the cost of the catheter – around US$ 1,000 –, it was also necessary to carry our various tests to increase the useful life of the instrument without this implying any risk of contamination to the patients. According to Zângaro, the expectation is that the catheter could be used for up to ten examinations. The commercialization of this product will be the responsibility of Tecnobio, but that still depends on obtaining its registration at the Ministry of Health. In spite of the difficulty of testing the equipment on human beings – tests have only been done on animals – , José Maria Rodrigues Bastos, the President of Tecnobio, believes that the product will be approved, at least for diagnosis, and it will not present any problems because the efficiency and absence of risk are well analyzed.

Bastos expects the product to go on the market in the middle of 2001 and his expectation is for a high acceptance rate in Brazil and abroad. “It is a promising product, due to the present al demand and the low cost, and also because of the possibility of the elimination of costs of laboratory analysis and sophisticated systems of diagnosis by imaging”, he says. Also, there are advantages in the use of the catheter for the diagnosis of cancer of the rectal colon. For its capacity of diagnosing cases of hyperplasia and adenoma, situations that can be pre-cancerous, the expectation of the researcher is that this type of exam will become a routine  procedure, making part of the list of preventative examinations. “It is much cheaper for the State to work on prevention than on the treatment of cancer, which lots of times requires long hospital stays, medicines and expensive procedures”, he says.

Besides making diagnosis, the spectrofluorimeter can also help in photodynamic therapy, a technique which could in time substitute that of chemotherapy. In this system, a drug is injected into the vein of the patient which then spreads through the body and ends up concentrating itself in the areas of the tumors. The drug on its own does not eliminate cancer, but when it is irradiated with a laser, it produces free radicals and oxygen which penetrate into the cancerous cells provoking a necrosis in the region of the tumor.

In this case the spectrofluorimeter helps in the verification of the distribution of the drug in the region of the tumor, indicating its concentration in a qualitative form.

Considerable advantage
For now the technique is awaiting the approval of the Commission of Ethics of the Cancer Hospital so that it can be used on patients who have submitted themselves to various other types of treatment without positive results. According to the researcher, the photodynamic therapy brings a considerable advantage to the patients in relation to chemotherapy. As it takes effect at only localized points, the technique does not attack the immunological system in a general manner, reducing the incidence of infection opportunities. The technique could even, in Zângaro’s opinion, avoid a large number of surgeries, which always imply higher risks, including that of provoking metastasis.

As yet there are no precise calculations about the cost of the commercialization of the spectrofluorimeter. It is estimated that it could get as high as US$ 70,000 since 70% of the components are imported. Even so, in the Zângaro’s opinion, the relationship of cost to benefit could be highly advantageous.
He estimates that in one year from now the equipment could be available on the market, but this as yet depends on negotiations with interested companies in establishing a commercial partnership. The important thing is that both the research and the commercial perspectives for the catheter and the spectrofluorimeter are at an advanced stage. They are going to provide improved techniques of diagnosis and the treatment of the illness with the use of the laser.

The projects
1. A Fiber Optic Catheter for the Diagnosis of Atheromatosis Plates in the Cardiovascular System (nº 96/06575-8); Type Partnership Program for Innovative Technology (PITE); Coordinator Dr. Renato Amaro Zângaro – Univap; Investment R$ 129,782.03 (FAPESP), and R$ 150,000.00 (Tecnobio)
2. Multiline Spectrofluorimeter for the Preventative Diagnosis of Cancer (nº 98/15541-5); Type Assistance to research program; Coordinator Dr. Renato Amaro Zângaro – Univap; Investment R$ 47,118.00 and US$ 84,156.51

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