National Physical Laboratory

Always faithful

NPL scientists have developed a new instrument called 'Fidelis' (Latin for 'faithful') which will ensure the safety of patients having nuclear medicine treatments.

Always faithful

More than 600,000 people a year undergo medical procedures using nuclear medicine. These procedures range from diagnostic scans through to cancer therapies.

The Challenge

In nuclear medicine, the accuracy of the dose received by the patient is all-important, both in terms of the safety of the patient, and the quality of the treatment itself. In diagnostic procedures radioactive compounds are injected into the patient and the resulting particle emissions are recorded via photographic techniques. If the dose is too low the images produced can be inconclusive. And if the dose is too high there is a health risk to the patient.

The Solution

A new instrument, called 'Fidelis', allows medical physicists to check their in-house instruments against the UK national standards for radioactivity, held at NPL. Once confident that their own instruments are measuring activity correctly, the right dose should always be given to the patient.

Fidelis comprises an NPL-designed ionisation chamber and a brand new electrometer module from Southern Scientific Ltd. An ionisation chamber is a gas filled enclosure between two conducting electrodes. When a radioactive source is placed near to the enclosure, gamma-rays emitted by the source ionise the gas - the current produced can be measured by the electrometer. 

The Impact

Previously hospitals used off-the-shelf Radionuclide Calibrators, which needed re-calibrating every time new applications for nuclear medicine or a new design of vial were developed. With Fidelis, this problem is solved - and medical physicists can be confident of their dosage, and the safety of their patients.

For further information, contact

Find out more about NPL's research in Radioactivity

Last Updated: 10 Aug 2012
Created: 8 Dec 2010


Please note that the information will not be divulged to third parties, or used without your permission