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A view inside during radiation therapy

Specific information about Radiation Therapy

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In this video, we will illustrate the different aspects of radiation therapy treatment. For this purpose, we will focus on a lung cancer patient. Please note that in order to show these aspects clearly, we are focusing solely on the thorax, or chest, of the patient. Therefore, the entire patient is not visible in this video. You will be positioned for treatment in the thoracic region using a device similar to this one. The radiation therapist will use a laser system to position you for treatment. You may have had some small tattoo marks placed on your skin at CT in the pretreatment phase.

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These reference marks are aligned with the lasers in the treatment room by the radiation therapist smoothing the treatment couch and moving you. The lights will be dimmed in the treatment room during this procedure. At this time, you will be asked to lie as still as possible and to allow the radiation therapist to move you. You do not need to help, as the movements are quite small and specific. When you are positioned correctly, you will hear the radiation therapists calling numbers and parameters to one another verifying from screens in the treatment room. This is a normal part of quality control and safe practise. On some days of treatment, images are taken before your treatment commences.

This is to check your position and ensure treatment accuracy. Images are taken with an imaging device on the linear accelerator. Here is an example of an image captured for this lung treatment. Here, we can see the area being treated in black, and the areas being protected are shielded from therapy in blue and green. These areas are shielded using motorised leaves known as multileaf collimators, or MLCs, which are made of high-density material and are located in the head of the gantry. Now we will look inside the patient to see exactly what is being treated and what normal tissues or organs at risk, OARs, are being avoided in order to minimise side effects.

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First of all, here is the tumour, known as the target volume. This is what we are treating. The tumour is in the patient’s rights lung. Therefore, areas that need to receive minimal dose are the left lung and the healthy tissue of the right lung.

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Other organs that should receive as low a dose as possible are the spinal cord and the oesophagus. These three-dimensional volumes are reconstructed from the CT that you had in the pretreatment phase. Now we will look at how radiation therapy is delivered. It is delivered using a series of beams. In this personalised plan, there are three beams used. These beams are selected to ensure that the target volume receives the dose prescribed by the radiation oncologist, and that the organs at risk receive as low dose as possible. You will see here that it is impossible to completely avoid all organs at risk. This is due to the location of organs to one another. This is why patients experience side effects.

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For this patient, it is likely that they will experience inflammation of the oesophagus, called oesophagitis, which may cause difficulties when eating, and a cough as some normal tissue of the lung is being treated. However, these can be managed with advice from your expert treatment team. This will be the daily procedure for treatment each day.

In this video, we used the VERT technology again to describe how radiation therapy works in the case of a lung cancer patient.

Here are some terms that you might be unfamiliar with used in the video:

Organs at risk

Organs at risk are normal tissues that are close to tumours, and as a result will be in the treatment field. The impact that radiation therapy has on these organs depends on their sensitivity to radiation therapy. This is taken into account when planning a patient’s treatment in order to minimise the dose to these organs at risk and maximise it to the tumour.

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This content is taken from
Trinity College Dublin online course,

An Introduction to Radiation Oncology: From Diagnosis to Survivorship

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Multileaf collimators

Multileaf collimators (MLCs) are made of high density material and are located in the head of the gantry. They are routinely used to shape the beam by blocking specific parts of the radiation beam.

Target volume

The target volume is the tumour, together with a small margin around, it to ensure that the tumour receives the prescribed dose.

Oesophagitis

This is inflammation of the oesophagus due to radiation. It may feel like pain when swallowing or a lump in your throat which can make eating difficult. This is a side effect which can be managed with advice from your expert treatment team.

Using the information in this video:

Why do some patients experience side effects with radiation therapy?

Want to keep learning?

This content is taken from Trinity College Dublin online course

An Introduction to Radiation Oncology: From Diagnosis to Survivorship

View Course

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An Introduction to Radiation Oncology: From Diagnosis to Survivorship

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