CT Users Group

Nicholas Keat

GlaxoSmithKline Clinical Imaging Centre,
Imperial College - London,
London

Abstract

PET-CT scanning can be a valuable tool for use in the pharmaceutical development process. Direct imaging of important issues such as receptor occupancy, and the kinetics and dynamics of drug metabolism offer insights that can only be gained indirectly, if at all, by other means. Monitoring disease progression through the use of biomarkers can also yield useful information.

In many early phase PET-CT investigations, the subjects are healthy volunteers who will gain no direct benefit from the scan. In these circumstances, the need to constrain and optimise radiation dose is paramount.

In most PET-CT pharmaceutical studies, the role of CT is to provide information for attenuation scanning, rather than anatomy. Image quality requirements of attenuation scans are lower than diagnostic scans, so they are typically carried out at low exposure parameters.

The goal of this study is to assess the effect of reducing the exposure further than in standard 'attenuation correction only' scans, to see how low we can go with CT radiation dose.

Anatomical head and body phantoms were scanned at a range of CT tube voltages and tube currents and PET images of these phantoms were reconstructed using each of the CT data sets. The image quality of the resulting PET images was assessed, and the effect of reduced CT dose quantified through the change in noise and activity concentration.

The results show that it is possible see the effect of reduced CT exposure in the PET images, but the increase in image noise is small. The use of different x-ray tube voltages can also be seen as a difference in absolute activity concentrations in the PET images. For this reason, it is concluded that the tube current can be reduced significantly from the default value, but care must be taken when considering changing the tube voltage.

Click the link for a pdf of the presentation:

Back to meeting timetable