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Wider aspects of Nuclear Medicine

The Petten nuclear facilities are not only used for development, improvement and production of existing and new pharmaceuticals. They are also used in other health-related applications. For some types of therapeutical treatment it is advantageous not to introduce radioactive material into the patient's body, but to produce them in the body. For that purpose the patient has to be brought to a nuclear reactor.

BNCT, Boron Neutron Capture Therapy

Alpha particles are relatively large and heavy. They are ideal bullets for eliminating cancer cells. However, they can only travela very short distance in human tissue - a few micrometers (1 micrometer = 0.000001 meter). An alpha particle will therefore only eliminate a cell at the spot where it is formed.
For BNCT, a patient is injected with a non-radioactive pharmaceutical which has the characteristic of selectively migrating to cancer cells. This pharmaceutical contains the element boron. If the patient is subsequently irradiated by a neutron beam the neutrons react with the boron in the tumour to generate alpha particles which destroy the tumour. Care is needed to ensure that the neutron beam is intensive enough to produce suffient alpha particles and yet does not damage the healthy tissue.

BNCT: not a new concept - history

BNCT is not a new concept. In 1936, only four years after the neutron had been discovered, physicists suggested the possibility of utilizing the reaction ¹⁰B(n,alpha)⁷Li as a method for treating tumours. During the 1950s, BNCT was actually tested in the United States. the results were not very successful and the whole idea was therefore abandoned.
The selectivity of the boron carrier was insufficient, which resulted in irreparable damage to healthy tissue. In the mean time science and technology have progressed and application of the original BNCT concept now has considerably better prospects.

In the high Flux Reactor, HFR, one of the neutron beam channels, which was originally installed for performing fundamental research, has ben specially modified for the irradiation of patients. Physicists use scattering and filtering techniques to provide a neutron beam having the correct narrow band energy level (velocity), sufficient to give the desired penetration into human tissue.

BNCT opstelling bij de HFR te Petten

The first series of 'trial' treatments have been conducted and the results are encouraging.

Other possibilities

Other elements
In principle, other elements which emit suitable radiation after neutron capture could also be candidates for Neutron Capture Therapy.
Alpha emitting radioisotopes which do not need extra neutron irradiation could also be attached to tumour seeking carriers. If the time needed by the carrier to reach the tumour is very short compared to the half-life of the radioisotope, such a nuclear pharmaceutical would cause little damage to healthy tissue but would concentrate damage at the targeted cancer cells.

Low Flux Reactor
De Lage Flux Reactor, een `huiskamer'reactor met een vermogen van 30 kilowatt (als de cv-ketel van een rijtjeshuis), levert thermische (langzame) neutronen die uitstekend geschikt zijn voor BNCT op oppervlakkige of oppervlakte-tumoren (zoals melanomen). Eerste experimenten op een fantoom en op levende cellen hebben al uitgewezen dat ook deze kleine reactor een toekomst heeft voor deze klinische toepassingen.

The Low Flux Reactor is our 'back garden' reactor with a power of 30 kilowatt, equivalent to the power of a central heating boiler in a terraced house.
This reactor provides thermal (slow) neutrons which are extremely suitable for BNCT on superficial or surface tumours such as skin melanomas. Initial experiments on a phantom (= model) and on live cells have shown that this small reactor also has a good potential for clinical applications.

Positron Emission Tomography (PET)
Lastly, we should describe our plans for a PET facility. PET is the acronym of positron emission tomography. this is a diagnostic technique which produces three-dimensional images. Its principle is based on the annihilation of positrons and electrons, resulting in two gamma rays which fly off in opposite directions. Counters set up around the patient detect the emitted gamma rays. Gamma rays arriving at the same time at the counters must have come from the same point in the body.
Advanced computer software programs can then be used to generate a detailed image of the part of the body being examined, as has already been successfully demonstrated for example in Groningen in a collaboration between the Academic Hospital and the Nuclear Physics Accelerator Institute.

For PET a patient must be administered a positron emitter. All positron emitters are short-lived, from two minutes to a few hours, so the PET scanner will have to be stationed close to where the radioisotope is produced, i.e. in the neighbourhood of a cyclotron. Transportation of a short-lived isotope, for example, from Petten to a hospital in Alkmaar would at least take half an hour by which time a substantial part of the 'PET' isotope would have been lost.

A PET facility in Petten would also provide an opportunity for further research and developement of the potentials of this technology.

  
NRG, Postbus 25, NL-1755 ZG Petten, Nederland, Tel +31-224564950, Fax +31-224568912
Informatie: info@nrg.eu
Update 18 June 2004