The new particle detection technology developed by the French
winner of the 1992 Nobel Prize for Physics, Georges Charpak, has caused
an upheaval in nuclear medical imaging. With the support of the Standards,
Measurements and Testing programme, and in cooperation with Italian
and UK partners, the French SME, Biospace Instruments, has developed
a light and simple instrument to monitor, in real time, the radioactive
products used to display certain organs. From now on cardiologists
in several European hospitals will find it easier to monitor the heartbeats
of their patients "live".
Imaging of the cardiac cycle by the emission
of radionuclides makes it possible to measure with precision
the ejection fraction of the left ventricle.
For more than 30 years the technique of injecting
radioactive products capable of fixing themselves selectively in certain
organs has been used in nuclear medicine to display the liver, brain,
thyroid and heart, and to look for tumour metastases throughout the
body. "The same system, the Anger camera, has been used since the
1960s to display the distribution of radioactivity. At this level,
progress has been minimal," notes Claude Hennion, Director of Biospace
Instruments. However, the innovative results presented by this SME
on completion of the European project in question could revolutionise
this medical technique. In 1996 this project was able to draw on the
additional combined expertise of Biospace (sensors), the Italian firm
Caen (high-speed electronics), the UK firm Hamilton & Hamilton (nuclear
medicine), the G. Galilei Department of Physics at Padua and the IDSET
in Paris. In the enthusiastic words of Eddie Maier, the scientist
responsible at the European Commission: "This is an exemplary project
that has benefited from the CRAFT measures to promote research by
SMEs. By embarking on the transfer of technology and high-energy physics
to scientific and medical instrumentation, Biospace has developed
a product which meets the expectations of the market and which therefore
has every chance of becoming commercially viable."
All this began in the 1980s when Georges Charpak, a physicist specialising
in particle detectors at the CERN laboratories in Geneva - and a future
winner of the Nobel Prize (1992) for his discoveries in this area(1)
- suggested to a biologist that they should construct a machine capable
of displaying the radioactive markers relating to his own experiments.
The image would be obtained in record time - several hours rather
than several months. "Although the machine as initially developed
was a physicist's prototype and extremely complicated to use," recalls
Claude Hennion, "my enthusiasm as a biologist at the results obtained
showed that the technology met a more general need, far exceeding
previous expectations. Together with Georges Charpak, we then decided
to set up Biospace Instruments. That was in 1989."
Rotary filming of the movement of the
After two or three years of R&D, the first fully automatic autoradiography
detector, displaying the distribution of radioactive markers on
a section of organ, for example, was developed. The instrument,
which now has the advantage of being simple to produce, consists
of superimposed metal grills under high voltage, encompassed within
a specific gaseous medium. When an ionising particle resulting from
a radioactive disintegration penetrates the sensor, it draws off
a cascade of electrons from the gas molecules, thereby creating
a light-emitting cloud that is easily detectable by a camera or
electronic means. Thus, in detecting the particles one by one, the
system does not merely provide an image of the distribution of the
radioactive product but also serves as sort of Geiger counter giving
an absolute reading of the number of radioactive molecules present.
"We then sought to apply this capability to the vast nuclear medical-imaging
market. In numerous diagnostic applications, such as pinpointing
cancerous tumours or displaying cardiac pump efficiency by measuring
the ejection fraction, the Anger camera has the disadvantage of
being an expensive and heavy - 400 kg to 500 kg - instrument, of
low efficiency and requiring lengthy integration periods. However,
what the cardiologists need is an image of the moving heart in real
At the patient's bedside
During 1999, the first mobile devices, available to the cardiologist
as and when required - i.e. at the patient's bedside - were installed
in a number of prestigious European hospitals.
The efficiency of the detection technique, which requires only
low doses and produces real-time images, opens up possibilities
for numerous applications. "In cancer chemotherapy, our detectors
will make it possible to adapt the treatment to each patient, ensuring
the greatest possible therapeutic effect while at the same time
avoiding cardiotoxic risks. In cardiac surgery, they will enable
the results of an open-heart operation to be displayed before the
thorax is closed up again, allowing for immediate further intervention
if necessary. In brain surgery, the fact that an image of the tumour
is available throughout the operation should permit a much more
precise ablation." The possibilities offered by a sensitive, compact
and relatively cheap machine will encourage the emergence of new
working practices hitherto undreamed of.
Once launched on the market, however, this technology will still
have to overcome a number of regulatory obstacles, since in many
countries the authorising procedures governing the use of radioactive
products are very strict as far as premises and personnel are concerned.
Claude Hennion remains unperturbed: "Once the therapeutic benefits
have been demonstrated, the pace of progress will be rapid."
Leaving aside the nuclear medicine sector, the Biospace detectors
will also be able to adapt to conventional radiography with the
added advantage of reducing by 20 to 30 times the levels of irradiation
associated with each examination. The question of monitoring the
levels of X-rays to which patients are exposed, particularly in
the area of screening, is becoming more and more pressing in the
context of international regulations.
A vast potential market therefore exists for the technology developed
by Biospace, which holds more than 10 international patents. "As
soon as we have entered the industrial marketing stage in nuclear
medicine, we shall be embarking on a radiology-intensive R&D phase,"
concludes Claude Hennion. This, in turn, opens up the prospect of
a new European project.
(1) The technology devised at CERN by Georges
Charpak has been developed in order to provide of a means of identifying
black matter in the universe - this missing mass the nature of which
is still a mystery to the astrophysicists, who are nevertheless
obliged to postulate its existence in order to explain the dynamics
of the galaxies which they observe.