Cancer patients and
their families

What is radiation oncology? Here, patients and their families can find a comprehensive guide of radiotherapy treatments in Belgium.

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Healthcare Professionals and radiation oncology

As a medical professional, you're familiar with the basics of radiotherapy. Visit the following pages for a more elaborate approach on the topic.

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Healthcare Policy makers and radiation oncology

Radiation oncology is not like other medical specialties. This section deals with existing quality initiatives and cost-effectiveness.

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Home > Glossary > A - H

A - H

 Accelerator CT FSRT
 Arc Therapy Dose Gating
 Brachytherapy Energy Gy, Gray
 Bunker External Beam Therapy Hadron Therapy
 Collimator Fiducials Hemostatic
 Cone Beam CT            Fluoroscopy  

 

Accelerator

 See: linear accelerator.

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Arc therapy

See VMAT. The treatment machine rotates completely around the body (but without touching the body of the patient). Sometimes different arcs are combined.

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Brachytherapy

Also known as internal radiotherapy, sealed source radiotherapy or curietherapy. It is a form of radiotherapy where a radiation source (applicator or seed) is placed inside or next to the area requiring treatment. Brachytherapy is commonly used as an effective treatment for cervical, prostate, breast, and skin cancer and can also be used to treat tumours in many other body sites. (source: Wikipedia)

More information about brachytherapy >>

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Bunker

A radiotherapy treatment uses ionising irradiation. This irradiation is safe if well targeted to tumors, in patients requiring radiotherapy, however, it should not touch other people who do not require it. Most beams used in radiotherapy have physical characteristics that permit them to cross normal walls of hospital buildings, which must be prevented. To protect visitors and staff of the hospital, treatment machines are therefore located in special rooms that have thick walls and a specific layout, making them 'watertight' for irradiation.

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Collimator

A collimator is a part of a treatment machine that narrows a beam of particles or waves. To "narrow" can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., collimated or parallel) or to cause the spatial cross section of the beam to become smaller. (source: Wikipedia)

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Cone beam CT

Before each treatment fraction of a radiotherapy treatment, the correct placement of the patient needs to be checked, and also if the tumour and the surrounding organs are still at the same place, to assure that the correct dose is given to the correct tissues. Different techniques are available, and the most widely used is Cone Beam CT (CBCT). This is a fluoroscopy system incorporated in the radiotherapy machine that is used continuously while the treatment machines rotates around the patient. As such a three-dimensional image, equivalent to a CT-scan, is obtained. This three dimensional image is called a 'cone beam CT'.

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CT

Computer Tomography. This term refers to the well known imaging modality where a scan is made of a part of the body in 'slices'. Most CT's are done for detecting or measuring the tumor before or after the radiotherapy, but there is also a special CT that is made to technically prepare the radiotherapy treatment : see Simulation.

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Dose

The goal of most radiotherapy treatments is to kill cancer cells by using radiation. The amount of irradiation determines the amount of damage to cancer cells. This amount is called a 'dose' and is expressed in 'Gray'. The total dose of irradiation can be given in a series of smaller doses, called fractions. A possible scheme is for instance to irradiate in 5 daily fractions of 3 Gray to arrive at a total dose of 15 Gy.

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Energy

The radiation beams used during a treatment have different physical characteristics. One of these is the 'energy', which is expressed in a certain amount of Volt. Because energies used are high, we use the term Megavolt (MV), referring to one million Volt. A classical radiotherapy machine working on electricity (not with a radio-active sourced inside) has an energy of between 4 and 25 MV. The energy determines how the irradiation behaves in the body. Easily explained one could say that higher energy irradiation 'flies through' part of the body before deposing the irradiation inside the body, while lower energy beams will depose the energy closer to the skin where the beam enters the body.

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External Beam Therapy

External beam therapy is used to aim highly focused beams of radiation at the edges of the site where cancer is found in order to destroy any abnormal cells and prevent the growth or regrowth of the tumor (Source: Radiologyinfo.org).

More information about External Beam Therapy >>

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Fiducials

In radiotherapy and radiosurgical systems, fiducial points are landmarks in the tumour to facilitate correct targets for treatment. These markers are dense metallic elements inserted into the patient body, usually with a needle. They are then located in or near the tumor, and will move whenever the patient or the tumor region moves. Some more advanced radiotherapy systems can observe these movements not only before the start of the treatment, but also during the execution of the treatment. When fiducials move, the radiotherapy system can then adapt the beam to the movement (interrupting the beam, or re-orientating the beam to seamlessly follow the tumor).

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Fluoroscopy

An X-ray machine delivers low energy photons, which will travel through the patient to obtain a medical image. If these photons encounter structures with a higher density in the patient, they are partially absorbed. On the other side of the patient a detector measures (like a photo camera) how much photons did get through at each part of the body. This system is primarily used for basic radiographies in the radiology department of the hospital. Radiotherapy machines or treatment rooms can also be equipped with fluoroscopy systems to help in controlling if a patient is correctly placed on the table, and in observing movements of patients and tumours before or during the treatment. See 'Cone beam CT' and 'Portal image'.

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FSRT : fractionated stereotactic radiotherapy

In fractionated stereotactic radiotherapy the dose is spread over a number of fractions, for instance in the brain Quite often, stereotactic radiotherapy treatments in the brain are done in one treatment fraction. This is called a radio surgical treatment.

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Gating

During the radiotherapy treatment, while the patient is on the treatment table, the patient and the tumour can move. A major source of movement is the mainly up- and down movement in the trunk induced by the respiration cycle. These movements can make a target volume move outside the treatment beam, which is not desirable. Instead of making the beam larger to cover a bigger area during the movement of the chest, it is also possible to switch the radiotherapy beam off while the tumour is not in the beam, and back on when the tumour returns to the original position a few (milli)seconds later in the respiratory cycle. This requires correlating the movements of the tumour with the movements of the thoracic cage. See also 'Tracking'.

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Gy, Gray

See also 'dose'. A dose of radiation deposited in a (human) body is called a 'Gray', with 'Gy' being the abbreviation. The definition is that 1 Joule (J) of energy per kilogram (kg) is one Gray.

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Hadron therapy

Hadron therapy is also called 'particle therapy'. It is medical radiation treatment during which the radiotherapy beams do not consist of 'photons' (without mass or a charge), but of particles with a mass or a charge. Different particles are possible. For more information on the physics of this treatment, click here. These particles have a different behaviour in the human body, which can help to obtain a higher anti-tumoural effect per dose of irradiation. It is also possible to more precisely determine to what depth the particles will travel, thus potentially sparing parts of the body that do not need irradiation. Classical radiotherapy machines cannot deliver hadron therapy, so a dedicated costly infrastructure is required. For some tumours hadron therapy is considered potentially better than photon based treatment, but these indications are rare. At this moment, there is no hadron therapy facility available in Belgium, but a special reimbursement program allow patients to obtain treatments abroad when needed.

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Hemostatic

Some tumors can induce bleeding, for instance in the lung, on the skin, in the urinary bladder or in gynecologial organs. This bleeding can be annoying for the patient, and continuing bloodloss can lead to a condition called anaemia, with for instance fatigue as a consequence. To increase patient comfort, a radiotherapy treatment of the bleeding area can often stop the bleeding. This is called a 'hemostatic effect' of radiotherapy.

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