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Stereotactic radiosurgery (single treatment)

Patient information A-Z


The aim of this leaflet is to explain the general process and side effects of having stereotactic radiosurgery (SRS). Before the radiosurgery treatment can be delivered you will need to attend for some planning visits.

What is stereotactic radiosurgery?

Stereotactic radiosurgery (SRS) is a very precise treatment to a small area of the brain. The treatment aims to give a high dose to small, isolated tumour(s) and a very low dose to the surrounding normal brain tissue. Treatment is normally delivered in a single treatment session but occasionally is given in three to five visits.

Planning visits

To allow the radiosurgery to be delivered very precisely and accurately and also to help you keep as still as possible, a device called an immobilisation mask will be made for you. Once this has been made, you will also need to have some scans to allow your doctor and the radiotherapy planning team to plan the radiosurgery. The planning of your stereotactic radiosurgery is a complex process which involves several stages and visits to the department.

Visits include:

  • Mask making process followed by a computed tomography (CT) scan
    Your mask will be created in our CT room; we will then perform a CT scan to aid us with planning your treatment.
  • The magnetic resonance imaging (MRI) scanner
    An MRI scan is performed to aid with the planning of your treatment - you will not need to wear a mask for this.
  • Radiotherapy treatment room
    This is where you will have your treatment.

What is an immobilisation mask?

To make sure your treatment position is exactly right, it is important that we keep you very still and supported. This is done using a mask made from thermoplastic material. The mask is individually made to fit you. It will cover your head and face. It is close fitting, but there are holes in the material so you will be able to breathe normally both while it is being made and during treatment.

The mask serves three purposes:

  1. It ensures that you are in exactly the same position for your planning CT and the treatment delivery.
  2. It helps you to keep still while the radiotherapy is being delivered.
  3. Any marks needed to position you for treatment can be drawn on the mask and not on your skin.

It is important that the mask fits you well so that the radiotherapy is accurate. If you have a beard, a moustache, or very long or thick hair, you may be advised to shave off your beard or moustache and have your hair trimmed before you attend for this first visit. This will ensure the mask is made as accurately as possible. Please also note that your hair will need to be free from hair products such as gels, hairspray and suchlike.

How is the mask made?

You will be asked to lie flat with your head, neck and body as straight as possible. Once you are in the correct position we use the thermoplastic material to form the mask. To do this the material is placed in a bath of warm water until it becomes flexible. The material will feel warm when placed over you.

The mask is made of three pieces of material (see Figure 1).

  1. The first piece is used to form an individual head and neck support. The material is warmed up in the water bath and then positioned over a headrest to enable us to make an impression of the back of your head.
  2. The next piece is used to take an impression of the front of your head, covering your forehead, bridge of your nose, upper lip and chin.
  3. The final piece will take an impression of your face; this piece of plastic is covered in tiny holes so you will be able to breathe normally throughout the process.

The mask will need to be on for at least 30 minutes before we can take it off (see Figure 2 for finished mask). The radiographers will check that you are comfortable and will ask for a 'thumbs up' sign. We prefer you not to answer us so that your mask does not change.

The three pieces comprising an immoblisation mask A finished immobilisation mask
The three pieces comprising an immoblisation mask
Figure 1: Mask components
A finished immobilisation mask
Figure 2: Finished mask

The CT scan

After the mask has been made, a CT scan is then performed to allow us to plan your radiotherapy treatment. You will need to wear your mask during the CT scan. Most patients will also require an injection of contrast agent; this helps to show up the tumour more clearly and plan your radiosurgery.

The MRI scan

To help us plan your radiosurgery treatment you may also need a new MRI scan. You will not need to wear the mask for this scan. We will, if possible, arrange for this scan to be done on the same day as your mask and CT scan appointment. This MRI can’t be done at your local hospital as we need some detailed MRI images for planning radiosurgery. An injection of contrast agent will need to be given, to help show up the tumour more clearly.

What happens next?

Man lying on couch in treatment room wearing an immobilisation mask
Figure 3: Fitted mask in treatment room

Once we have all the imaging, we can plan your radiotherapy. It should take a week or two to prepare the plan.


When you attend for your radiosurgery, the radiographers who are going to treat you will show you the room and explain what will happen.

For the treatment, you will need to lie on a treatment couch and the radiographers will position you in your mask (see Figure 3). It is important that the mask is tight, but if the mask isn’t comfortable or feels too tight it is important that you tell the radiographers so that adjustments can be made before the treatment starts.

Once you are positioned, the radiographers will leave the treatment room but will be watching you all the time on CCTV and can also talk to you via an intercom if you wish. If you need them to stop and come in you should wave a hand. The mask can be taken off at any time and this will not affect the treatment. You can also have music playing while the treatment is being delivered. To make sure the treatment is very accurate, a number of images will be taken before and during the treatment. These allow us to check your position in the mask and to make small adjustments to the couch position if necessary.

Treatment is then delivered. The noises the machine makes during scanning and treatment include humming and clicking noises, there is also a beeping noise which is the room monitor.

The treatment is delivered using a specially adapted linear accelerator (see Figure 4). On the linear accelerator the couch will rotate into different positions whilst the head of the machine rotates around you. You may notice the couch moving slightly during the process, but this is normal. The machine will not touch you and you will not feel anything as the radiosurgery is delivered. Treatment can take up to 45 minutes to deliver (per tumour being treated), and is usually delivered in three to six segments. You will be given the option of having a break in the middle if you wish.

Side effects

This single dose of radiotherapy may cause some swelling around the area of brain treated. The doctor will prescribe some tablets (steroids) to try to minimise any possible side effects. You will be given instructions on when and how much to take when you attend the initial clinic. It is important that you follow these instructions. You may still find that you experience some headaches and nausea in the days following your treatment. Your doctors will also have prescribed some anti-nausea medication to have available at home after the radiosurgery. One of the main side effects is normally fatigue which can last for some time after the treatment.

You may also lose some hair in the weeks following the radiotherapy. This will only be in the area where the radiotherapy beams enter. It should grow back normally, but this may take some months. Your treatment radiographers will advise you on appropriate skin and hair care.

A specially adapted linear accelerator
Figure 4: A linear accelerator

What happens after treatment?

One week after your treatment you will receive a follow-up phone call or face-to-face appointment with the neuro-oncology team who organised your radiosurgery. This is to check that you are recovering from the radiotherapy and have no queries or concerns about the treatment. Normally, you will be discharged back to the care of your normal oncologist after this appointment, and their team will be asked to arrange for a new scan about three months after the radiosurgery.


If you have a brain tumour and you drive any type of vehicle, you must contact the DVLA and inform them of your diagnosis. If you have a single brain metastasis on your scan, and it is treated with radiosurgery, then you may reapply for your licence if you are well 12 months after completion of radiosurgery. If you have more than one metastasis on your scan, then you may reapply for your licence 24 months after radiosurgery. The DVLA also has strict guidelines if you have suffered from seizures before, during, or after your treatment.

Failure to comply with these regulations is illegal and potentially dangerous; your insurance will be invalid and you may be fined up to £1000.

Further questions

It is important to us that you have all the information you feel you need about your treatment before the treatment starts. If you have any questions about your radiotherapy treatment, the side effects that you may experience, or anything else that we may be able to help with, please contact the specialist SRS/SABR radiographer on 01223 348048 or bleep: 01223 245151 (152 187) (Tuesday-Friday).


Addenbrooke’s acute 24 hour oncology helpline: 01223 274224

Specialist SRS/SABR radiographer: 01223 348048 or bleep 152-187 via 01223 245151

Radiotherapy reception: 01223 216634

Oncology reception: 01223 216551 / 216552

DVLA: 0300 7906806 / Drivers Medical Group, DVLA, Swansea, SA6 7JL

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

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Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151