10.6.4 Use of high energy X-rays

High-energy X-rays

High-energy X-rays are commonly used in radiotherapy to target and destroy malignant (cancerous) cells. This approach is effective in either killing tumour cells or limiting their growth. Since X-rays are a form of ionising radiation, they are capable of damaging any cell they penetrate, including healthy ones. Therefore, specific strategies are employed to minimise exposure to healthy tissue while maximising the dose to the tumour.

Techniques for Targeted Use of X-rays in Cancer Treatment

1. Tumour Localisation with Scans: Before treatment, scans are conducted to accurately pinpoint the tumour's location. This helps to ensure that the high-energy X-rays are directed precisely at the tumour, reducing unnecessary exposure to surrounding healthy tissue.

2. Selecting the Correct Energy Level: The energy level of the X-rays must be carefully chosen. Higher energy levels are used to penetrate deeply situated tumours, while lower energy levels may suffice for tumours near the surface. Choosing the correct energy allows for effective tumour targeting with minimal harm to surrounding tissue.

3. Use of Shielding: To protect non-cancerous tissue from radiation, shielding materials such as lead may be placed over healthy areas. This reduces the risk of radiation damage to critical organs and tissues adjacent to the tumour site.

4. Collimated X-ray Beams: The X-ray beam is narrowed and directed through a collimator to make the photon stream more parallel. This process focuses the radiation onto the tumour and reduces scatter, thereby lowering the dose received by healthy tissues.

5. Multiple Beams Targeting the Tumour: Several beams of radiation are directed at the tumour from different angles. Each individual beam is relatively weak and thus causes minimal damage to the tissue it passes through. However, all the beams converge on the tumour, delivering a higher cumulative dose precisely at the target site.

6. Rotating Beam (Isocentric Technique): In this method, the X-ray source rotates around the patient with the tumour located at the centre of rotation. By continuously changing the angle, the beam delivers the highest dose to the tumour while limiting exposure to surrounding tissues, as each part of the surrounding tissue only briefly intercepts the beam.