Simulation/CT

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Simulation/CT

For precise planning of their radiotherapy, almost all patients require simulation. This involves the use of imaging in the form of x-ray or CT scanning.

CT stands for computed tomography - a radiological imaging that uses computer processing to generate an image of tissue density in 'slices' through the patient's body.

Patients require very precise targeting of radiation, particularly those having treatment to the head and neck. For head and neck treatment, an individualised mould is made to keep the person as still as possible during treatment.

The mould is made before any x-rays or CTs are done and may require an additional visit.

To make the mould, all patients are placed in the same position they will be in during treatment. (Whether or not a mould is required depends on the area to be treated and the comfort of the patient.)

Patients for treatment on the cobalt unit usually have their treatment planned using x-rays to localise the area to be treated. Once the team are happy with the treatment area, the patient has this area marked on their skin with ink and some sticky tape is put on to avoid the ink being washed off.

Patients for treatment on a linear accelerator will generally have a CT to plan their treatment.

Patients are CT'd in the same position they will be in when having their treatment. The patient lies on the CT couch usually on their back and immobilisation devices / support wedges are put in place to help the patient keep as still as possible.

About 65-70% of patients have what is called a contrast scan. A warm colourless dye is injected into the patients vein and then the scan taken. The contrast scan shows more detail than a normal scan this is for planning purposes.

When the scan is complete the radiation therapist will place a small ink mark called a tattoo just under the patient's skin using a tiny needle. This tattoo is to enable the treating radiation therapists to locate the area to be treated.

At CT the patient is given the start date for the treatment. In St Luke's hospital the patient is also contacted one or two days before the start of treatment to confirm the appointment time and if a patient is coming into the ward they are contacted by admissions.