- Introduction
Soon after Wilhelm Conrad Röntgen discovered his X-rays in 1895, people realized its potential use in clinical use. It was Röntgen self who made the first x-ray picture in the way we are all familiar with. A photo from the hand of his wife clearly shows the bones of her fingers inside the flesh. It did not take long before x-ray imaging became one of the most important diagnostic tools in the clinic, a status it still has today.
Although mainly unaware of the potential dangers, physicians at that time also noticed that the x-rays showed benificial and curable effects on diseases of the skin and cancerous tumors. This finding gave birth to a new field of medicine, radiation oncology, where the battle against cancer could now be fought with this newly discovered form of radiation. Nowadays, every cancer hospital has a radiotherapy department and irradiation has become the treatment of choice for many types of cancer. Also the NKI/AVL has a rich history of radiotherapy treatment, in fact the possibility to perform X-ray treatments was one of the main reasons to found the hospital in 1915. In the 1930's, the work of physician Daniel den Hoed played an important role in the development of better and more accurate irradiation protocols. The NKI/AVL is still a frontrunner today, and developments of new treatment techniques and optimizations are a key part of its radiotherapy department.
- Cone beam CT scan
While in 1936 Daniel den Hoed was the first physician in Europe with a radiation machine that was able to work at ultra-high voltages of up to 1 million Volts, todays "linear accelerators" easily reach 10 to 20 times as much. Of course with these devastating powers at hand, it becomes extremely important to only hit the cancerous tumors and not the healthy surrounding tissues. Therefore, scientists more and more try to combine irradiation protocols with online imaging techniques, working towards so-called "image guided radiotherapy".
- A number of imaging techniques have been developed to visualize the internal organs at high resolution, including Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), and Computed Tomography (CT), each with specific applications and advantages. The classical Computed Tomography or CT scan, is well known by many through the characteristic tunnel-like machine. The scanner directs a series of X-ray pulses through the body. Each X-ray pulse is detected by a line-detector and thus represents a "slice" of the area being scanned. After moving the subject slowly through the tunnel, all slices can then be used to reconstruct the complete organ under study.
In contrast to the classical CT scanner, the cone beam CT scanner does not image slices, instead its cone shaped beam illuminates a complete volume at once (see figure). By rotating the beam around the subject and making an image every so many degrees, the area of interest is observed from many different angles. Then, with help of advanced image reconstruction algorithms, the subject can be reconstructed in 3D at high resolution as shown in this example of the head and neck region. Using these images, the physicians can get an exact idea of the location of the tumor, which allows them to precisely point the radiation beam to the right spot, saving the surrounding healthy tissues.- The 4th dimension
Together with the manufacturer and a consortium of reknowned cancer centers, the NKI/AVL have developed a linear accelerator with integrated cone beam CT scanner. A kV diagnostic X-ray tube and a flat-panel imager are mounted on the gantry drum structure of an Elekta linear accelerator perpendicular to the treatment beam. Now just prior to treatment, a 3D reconstruction of the area of interest can be acquired and used to accurately adjust the treatment beam to fit exactly the shape of the tumor thereby minimizing damaging effects on vital organs. The software for image reconstruction and analysis has been developed in-house. In Februari of this year, the NKI/AVL was the first hospital worldwide to take this kind of machine in clinical practise.
Currently, the group of Marcel van Herk is working to further improve image guided radiotherapy by accounting for organ movement during radiotherapy treatment. While a patient is irradiated, he or she is not a static object. For instance, breathing motions continuously shift the position of both vital organs and the tumor, which can form a serious problem in the treatment of for example lung cancer patients. By online imaging and analysis of breathing cycles, Van Herk and colleagues hope to further increase the succesrate of treatment protocols by hitting the tumors with even higher precission.-
- More information
- Further information please visit the Van Herk group's webpage using the following link: Learn more >>
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A CT scan uses x-rays to produce detailed pictures of structures inside the body, and stands for Computed Tomography scan. Another familiar name is CAT scan, for Computed Axial Tomography. The classical CT scanner is a tunnel-like, donut-shaped machine in which the area being studied is positioned. The inside of the machine rotates and takes x-rays from different angles, which are later used by computers to make an image of a ’Äúslice’Äù (or cross-section) of the organ studied.
On 8 November 1895, German physics professor Wilhelm Conrad Röntgen (1845-1923) discovers a new kind of rays originating from discharging electrical current in highly-evacuated glass tubes, which he calls X-rays.
To Röntgen's surprise, he notes that when his cardboard-shrouded tube was charged, a screen across the room begins to glow. While holding materials between the tube and screen to test the new rays, he observes the bones of his hand clearly displayed in an outline of flesh. His subsequent experiments result in his now famous report "Uber eine neue Art von Strahlen" which is published in December, and is accompanied by experimental radiographs and the image of his wife's hand. By New Year's Day physicist friends across Europe have read the report in amazement. Soon after the world is gripped by "X-ray mania", which turned out to be only the start of a wide variety of applications that are now impossible to think away in daily life. In 1901, Wilhelm Röntgen wins the first Nobel prize in physics.