PET imaging is widely used in the management of cancer patients.
Most commonly, an FDG PET scan is carried out to identify areas
with high glucose metabolism, such as tumours. These images are
useful for diagnosis, staging and monitoring treatment.
Such a scan requires the injection of a radioactive 'tracer' -
which is taken up by the tumour tissue - and therefore the
procedure has an associated radiation dose for the patient and for
staff at the imaging facility.
A recent study by scientists at Central
Manchester University Hospitals NHS Foundation Trust and The
University of Manchester investigated whether technological
developments in scanner equipment over the last decade could allow
a reduction in the amount of radioactive tracer used.
Ian Armstrong, a
nuclear medicine physicist who led the study, said: "Despite
improvements in PET technology, we haven't seen any change in the
guidance regarding the amount of injected radiotracer we should use
for FDG PET."
PET imaging relies on the detection of simultaneous pairs of
gamma rays produced when positron particles emitted by the injected
tracer interact inside the body. The team looked at an analysis
approach using time-of-flight (TOF) information, which utilises the
faster detectors present in modern PET systems to more accurately
locate the source of each pair of rays.
They found that by making use of TOF information, they could
reduce the number of 'counts', or individual gamma ray pairs, they
measured. This means that for the same quality of image, they could
reduce the injected radioactive dose, or scan for a shorter period
Ian said: "Here in Manchester we've decided to use this
improvement to do both - reduce the administered activity and the
scan time. As a result we have managed to lower the radiation dose
for cancer patients and our staff and also increase the numbers of
scans we are able to carry out."
Paper entitled "The assessment
of time-of-flight on image quality and quantification with reduced
administered activity and scan times in 18F-FDG PET" Armstrong
et al. (2015) Nuclear Medicine Communications 36:728-37
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