Radiology & Imaging

Q&A: Dense breast tissue and molecular breast imaging

DEAR MAYO CLINIC: After a recent mammogram, I was told that I have dense breast tissue. What does that mean? Should I be concerned? What does that mean for my future screenings?

Oncology & Cancer

New technique for ultrafast tumor therapy

For the first time, researchers at the Center for Proton Therapy at the Paul Scherrer Institute PSI in Switzerland have tested ultrafast, high-dose irradiation with protons. This new, experimental FLASH technique could revolutionize ...

Oncology & Cancer

Study: Cancer cases likely in those exposed to atomic test

After years of study, the National Cancer Institute said Tuesday that some people probably got cancer from the radioactive fallout that wafted across New Mexico after the U.S. government detonated the first atomic bomb in ...

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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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