Imaging

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Radiology is the term used to describe the diagnostic imaging that is used to reveal, diagnose or examine cancers. This helps give an accurate picture of the exact size and shape of the tumour. The images allow the radiation treatment to be delivered very accurately, at optimal strength, while minimising impact on the surrounding healthy tissue.

Diagnostic CT scans and Magnetic Resonance Imaging (MRI) are most commonly used. The CT scans provide cross sections of a tumour, while MRI scans enable clinicians to more accurately outline soft tissue structures such as in the prostate or head and neck.  

Where necessary ARO uses four-dimensional computed tomography (4D CT), which is the latest in imaging technology. It makes CT scans much faster and more accurate, and records precise, 3D images of tumours. Since tumours can move over time or change position with the natural function of your body, 4DCT records this movement too - this is considered the fourth dimension. This is particularly important information for treating cancers near organs that move regularly, like your heart or lungs.

In more detail

You will almost certainly begin your treatment journey with a diagnostic CT scan. If necessary, your planning team will also recommend a MRI or a four-dimensional computed tomography (4D-CT).

4D-CT scanning technology allows treatment to be administered more precisely. It records the size, shape, and crucially, the movement of the tumour. This means radiation treatment can be contained more precisely to the tumour area, with only minimal margins into the healthy tissue. This limits side effects and allows for much higher doses to be administered at one time.

This technology is particularly important when treating moving organs, like the lungs or heart. For example, with traditional imaging, the radiation oncologist can only know the position of a lung tumour at one point in the patient’s breath cycle. This means the radiation beam will hit the tumour only once per breath, reducing the effectiveness of the treatment while also exposing a lot more healthy tissue to radiation. To minimise damage, the radiation must be delivered at a far lower dose, further reducing it effectiveness.

With 4D CT, treatment can be delivered only within a certain interval in the breathing cycle, using gated intensity-modulated radiation therapy (IMRT). This is a form of IMRT where the radiation stops when the tumor is not in the correct position.This allows treatment to be delivered at much higher, more effective levels and also minimises impact on healthy tissue.