Treatment modalities and technologies

An introduction to radiotherapy

Radiotherapy means “to treat using radiation”. You may be familiar with the use of radiation for making an X-ray image. The same kind of X-rays, with a much higher energy, can also be used to treat harmful parts of the human body such as a tumor. Radiotherapy can be applied as an indivudual treatment, or in combination with surgery and/or chemotherapy.

Radiation damages the DNA of cells in your body. When given a high enough radiation dose, the cells in the tumor will no longer be able to divide and tumor growth will be halted. It is, however, unavoidable that cells in your healthy organs will also be hit by the radiation, leading to unwanted side-effects.

A cell may recover from damage by irradiation. Cancer cells typically are less effective at such repair than are healthy tissue cells. Therefore, the radiation dose is often given in multiple treatment fractions. This allows the healthy cells to recover while tumor cells will receive the next radiation dose while still damaged. The optimal fractionation and prescribed dose will be determined by your radiation oncologist.

Sparing healthy tissues

The amount of healthy tissue irradiated, and thereby the side-effects, will be minimized by choosing the right treatment technique. The optimal treatment technique depends on many factors, such as the size, shape and location of the tumor and the proximity to healthy organs. Your radiation oncologist, together with a medical physicst, will choose the radiation type and technology that allow delivery of the prescribed dose to the tumor while minimizing unwanted side-effects.

Computer technology allows the planning and calculation of the radiation dose to be given to the tumor. These calculations are reviewed as to their accuracy and correctness by a multidisciplinary team consisting of radiation oncologists, medical physicists and dose planning specialists.

Our treatment options

We are proud to offer various treatment options in all of these three main categories:

• Photon radiotherapy
• Proton therapy
• Brachytherapy

Please click on the corresponding header (above) to learn more.

The medical physics team ensures that the safety and quality of all treatment options offered in our department are continuously maintained at the highest (inter)national standards. In collaboration with the radiation oncologists and our (inter)national partners we are committed to continuously improve on current international standards of practice. This is realized by implementing and innovating new treatment techniques so that we can offer the best possible treatment for any cancer patient.

What is photon radiotherapy?

In photon radiotherapy one or multiple beams of radiation are aimed at the tumor from outside of the body. It is therefore also called ‘external beam radiation therapy’. The treatment beams are most commonly generated using a linear accelerator, also called a linac. Within the linac a narrow beam of electrons is accelerated and then transformed into broad beam of photons. These high energy X-rays can penetrate the human body. The linac can accurately aim the beam at the tumor and shape it such that the contours of the tumor are narrowly followed. This minimizes the exposure of healthy tissues. Since the linac is able to rotate around you, treatment beams can be given from any angle.

The linac is one of the most  complex machines within the medical field. Accurate and safe operation of the linac is ensured by extensive quality assurance and control measures taken and implemented by the medical physics team. The linac is placed inside a bunker to protect our staff and other people, such as those in the waiting room, from (stray) radiation. The walls of the bunker are made of thick concrete and the door is thick and heavy. Therefore, the radiotherapy department is safe for all visitors.

Treatment on a linac

Prior to treatment, a CT-scan is made of the tumor and surrounding tissues. This allows the planning of the radiation dose in 3D using computer technology. Additional imaging technologies such as functional imaging using MRI or PET-CT can be used to aid the radiation-oncologist in identifying and delineating the tumor. The linac is operated by a group of radiotherapy technologists (RTTs). They will guide you to your treatment and make sure that you are positioned correctly with respect to the treatment beams. When the bunker is closed during treatment they will supervise you through camera’s and you will be in audible contact with them.

During each treatment fraction you will be able to hear the electrical and mechanical components of the linac. You will not be able to see, hear or feel the radiation itself. Depending on the complexity of your treatment, each beam delivery can last from tens of seconds to tens of minutes. As soon as the treatment is finished and the linac is turned off, the radiation will be gone immediately. You will not be(come) radioactive and people will not receive any radiation dose from being near you.

Orthovolt treatments

Another type of photon radiation treatment uses so-called orthovoltage X-rays. The energy of the photons, and thereby their ability to penetrate the human body, is much lower. This type of photon radiation is therefore applied for the treatment of superficial tumors (such as skin tumors). Because of the much lower energy, the treatment machine and the (walls of the) treatment room are much smaller.  

A linear accelerator (linac)

Start of patient treatments

As of January 2018 the UMCG department of radiation oncology is the first department in the Netherlands to offer proton therapy as a treatment modality.

What is proton therapy?

Protons are small particles that are electrically charged. A cyclotron in a separate bunker accelerates the protons to two-thirds of the speed of light. The protons are subsequently guided towards the treatment room using magnets. Inside the treatment room a so-called gantry allows the aiming of the proton beam from any angle. This gantry is much larger than the linac used in photon therapy.

Because of their charge and depending on their energy, protons will only be able to penetrate the human body to a specific depth. Most of their energy is lost near this end of range, resulting in the characteristic Bragg-peak. Compared to photons and for an equal dose to the tumor, this results in a reduction of dose to the surrounding healthy tissues. This reduction in dose can result in a reduction of side effects.

Dose as a function of depth in the body, for both a photon beam and a proton beam.

The proton beam is very thin so that it only treats a small part of the tumor at a time. For this reason, the proton beam is sometimes called a pencil beam. The pencil beam is moved in a scanning motion, each time irradiating a small part of the tumor. This ensures adequate radiation dose in the entire tumor while minimizing the dose to the surrounding healthy tissue.

Your proton therapy treatment

During each treatment fraction you will be able to hear the electrical and mechanical components of the proton gantry. You will not be able to see, hear or feel the radiation itself. Depending on the size of your tumor and the complexity of your treatment, a treatment fraction may last for up to 30 or 60 minutes. As soon as the treatment is completed and the proton beam is turned off, the radiation will be gone immediately. After treatment you will be very mildly radioactive but you will pose no danger to people around you.

The medical physics team has implemented an extensive and continuous quality assurance program in accordance with international standards to guarantee an accurate and safe treatment. We strive to further improve the treatment techniques and quality assurance through scientific research and innovation in collaboration with our (inter)national academic and industrial partners.

Proton therapy: not for everyone

Proton therapy will not always be the best treatment modality for your tumor. Some patients, such as children, will always be eligible for proton therapy. Other patients are only eligible if they are expected to have a large benefit from proton treatment. For these patients, two treatment plans are made and compared: one using photons and another using protons. If the calculated differences in side-effects are sufficiently large, you become eligible to receive proton treatment.

A proton therapy gantry (photo by RTV Noord)

Radiotherapy delivered from inside your body

When radiation therapy is applied from within the body – with a small source - it is called brachytherapy. The source has the size of a grain of rice and is placed close to or within the tumor. The amount of radiation dose very quickly declines with increasing distance from the source. Healthy tissues that are located more than a few centimeters away from the source will therefore receive very little dose, leading to a reduction in side-effects. To apply brachytherapy it has to be possible to reach all regions of the tumor with the radioactive source. The use of brachytherapy is therefore strongly dependent on the specific properties and location of the tumor.

The small radioactive source is stored in a lead vault, called an afterloader. Before treatment, one or more tubes are positioned near the tumor. These tubes are connected to the afterloader and guide the radioactive source towards the tumor. The source will spend a short, pre-calculated, time at one or multiple pre-determined locations, before it is retracted into the afterloader at the end of treatment.

During treatment you will be able to hear the electrical and mechanical components of the afterloader. You will not be able to see, hear or feel the radiation itself. As soon as the treatment is completed and the source retracted, the radiation will be gone immediately. You will not be(come) radioactive and people will not receive any radiation dose from being near you.