Science is - what you make of it

Blog 12 – Science is - what you make of it

More x-rays on Thursday last week for the dry run – which involved using x-rays to line things up rather than gamma rays to deliver treatment. You know, having just written that, I’m driven to find out what’s the difference. So here’s the science bit.

The distinction between X-rays and gamma rays has changed in recent decades. Older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10−11 m, defined as gamma rays. However, they are now usually distinguished by their origin: X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus. (Try this for more but simplistic  explanation http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/radiation/treatmentrev1.shtml)

Radiation treatment can be systemic – you swallow the radioactive material or inject it into the blood; Internal (aka Brachytherapy) – you wear it – either a pill injected next to the affected area or the material is taped to the skin; or external – you have it thrown into you by big spanky, shiny machines.

Mine will be external – so photon beams. A photon is the basic unit of electromagnetic radiation. It can be thought of as a bundle of energy. The amount of energy in a photon can vary. For example, the photons in gamma rays have the highest energy, followed by the photons in x-rays and way down the list is light.

There are many different way of delivering the photons. Mine will be IMRT (Intensity-modulated radiation therapy) – IMRT uses hundreds of tiny radiation beam-shaping devices, called collimators, to deliver a single dose of radiation. The collimators can be stationary or can move during treatment, and can allow the intensity of the radiation beams to change. This modulation allows different areas of a tumour or nearby tissues to receive different doses of radiation.

Like chemotherapy (explained in the previous blog), radiation works by breaking a piece of the DNA molecule inside the cells that it hits. This break keeps the cell from growing, dividing, and spreading. Unlike chemotherapy which attacks rapidly dividing cells, radiation is indiscriminate –so both cancer and non-cancer cells are killed, and you have to wait for normal cells recover and work the way they are supposed to. The dying off continues for two weeks after radiotherapy commences, the recovery takes a long time to complete – for some things, a few weeks, for a lot of things, three months, and for some other things it could be a few years or it could be never.