Gold nanoparticles for cancer treatment

A new project at the National Physical Laboratory (NPL) will develop methodologies to measure the radio-biological impact of gold nanoparticles, when used in combination with ionising radiation for enhancing radiotherapy ...

Moon tourists risk rough ride, experts say

Non-stop vomiting, a puffy face and the constant need to pee: Volunteers for a week-long loop around the Moon may be in for a rough ride even if all goes to plan.

Primordial fear: why radiation is so scary

Nuclear radiation is frightening stuff. A quarter century after Chernobyl, and more than 65 years after atomic bombs laid waste to Hiroshima and Nagasaki, fatally sickening thousands not killed outright, even unfounded fear ...

Cosmic rays zap a planet's chances for life

Mysterious cosmic rays constantly bombard Earth from outer space. Now scientists find these energetic particles could limit where life as we know it might exist on alien planets.

Using calorimetry to estimate absorbed dose from CT scans

In the United States, about 80 million x-ray computed tomography (CT) scans are made every year – 7 million of them on children – according to the American Association of Physicists in Medicine (AAPM). Not surprisingly, ...

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Absorbed dose

Absorbed dose (also known as total ionizing dose, TID) is a measure of the energy deposited in a medium by ionizing radiation. It is equal to the energy deposited per unit mass of medium, and so has the unit J/kg, which is given the special name Gray (Gy).

Note that the absorbed dose is not a good indicator of the likely biological effect. 1 Gy of alpha radiation would be much more biologically damaging than 1 Gy of photon radiation for example. Appropriate weighting factors can be applied reflecting the different relative biological effects to find the equivalent dose.

The risk of stochastic effects due to radiation exposure can be quantified using the effective dose, which is a weighted average of the equivalent dose to each organ depending upon its radiosensitivity.

When ionising radiation is used to treat cancer, the doctor will usually prescribe the radiotherapy treatment in Gy. When risk from ionising radiation is being discussed, a related unit, the sievert is used.

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