Dure nacht voor student

De jongen nam volgens de politie vanmorgen rond vijf uur op het NS-station aan de Van Leeuwenhoeksingel ‘kennelijk bij wijze van grap’ een brandblusser mee.

Daar bleef het niet bij. In de Coenderstraat spoot hij het apparaat op straat leeg. Toen politieagenten hem vervolgens zagen lopen met de brandblusser, spraken ze hem aan en presenteerden hem een proces-verbaal wegens diefstal en vernieling.

In research being conducted by PhD student Jan Heemskerk, a  method for medical imaging uses a pin-holes technique (bottom image) supported by CCD cameras that allows for much sharper images of the human organs being examined for tumours and other medical maladies. The new pin-hole technique is a vast improvement on the currently used collimation (top image) method.
(Illustration: Jan Heemskerk)

This year’s Nobel Prize of Physics has been awarded to Willard S. Boyle and George E. Smith for their invention of the CCD sensor, and to Charles Kao for his scientific achievements regarding the transmission of light in optical fibres. Both of these inventions now belong to everyday life – CCD sensors for instance feature in digital cameras – and of course CCD sensors and optical fibres also figure prominently in various TU Delft research projects.
Jan Heemskerk, a PhD student from TU Delft’s Radiation, Detection and Medical Imaging section, is working on a setup with CCD sensors. The aim is to build a new type of gamma-ray detector for medical applications.
‘When a gamma-ray picture is taken of a human body, we usually need a detector as large as the body itself, because gamma-rays are difficult to bend,” Heemskerk says. “We’re now developing a method to reduce the size of the detector.”

Heemskerk explains that, with this new method, “first small amounts of radioactive material are brought inside the patient’s body, which is done by attaching the material to a biological molecule – or tracer molecule – that seeks a tumour, for example.”
In Heemskerk’s method, radiation emitted by radioactive elements is captured by a pinhole – a small hole like in a camera obscura: “A CCD sensor is placed behind this pinhole and captures the final image,” he says, adding that this new type of detector is smaller than those currently used. “The radiation coming from the radioactive material emits in all directions; therefore one small CCD camera can make an image of large parts of the body, such as the brain.”

Another advantage of this setup is that the amount of radiation needed is smaller, which of course benefits the patient. The medical application of CCD in Heemskerk’s setup is no exception.
Professor Freek Beekman, head of the Radiation Detection and Medical Imaging section, says that in recent years the CCD camera is increasingly being applied in medical applications, such as with endoscopy: “The CCD sensors used for our medical research make a thousand times less noise than the one in your photo camera.” Consequently, CCD sensors are also now used by the military for night-vision equipment.

Perspective
The CCD sensor, as invented by Nobel Prize winners Boyle and Smith, was not originally developed with this application in mind; rather, the two scientists had only planned to use the sensor as electronic memory, not as cameras capable of detecting single photons.
Dr Florian Bociort, of the Imaging Science and Technology section, puts the idea that Boyle, Smith and Kao are the inventors of CCD and optical fibres into perspective: “Apart from Nobel Prize Laureates, many other researchers have contributed to achieving the quality of CCD sensors and optical fibres as we know them today. The Laureates are considered to have contributed an important part to the chain of developments.”
He takes the development of optical fibres as an example: ‘For optical fibres, it was thought that they were impractical, because of the large attenuation of the signal as it travelled through the fibre. However, Kao discovered that by using improved glass quality this problem could be solved.”

The optics group at TU Delft’s faculty of Applied Sciences claims that one of the faculty’s former professors, Bram van Heel (1899-1966), made an essential contribution in the early stages of fibre optics. “He published an article entitled ‘A new method for transporting optical images without aberrations’ in Nature in 1954,” Bociort says. “But when looking at the history of optical fibres he usually isn’t mentioned.”
Nevertheless, credited or not, Van Heel certainly contributed to the chain of inventions leading to the optical fibres of today. How much further this chain of invention will stretch, no one can ever say.