As most tumours have a high glucose consumption, important information on tumour
metabolism can be obtained from PET imaging using 18F-FDG as a radioactive glucose
analogue. From literature it is known that quantitative analysis improves the clinical
value of 18F-FDG PET. However, instead of measuring the true tumour glucose consumption
Km, in current clinical practice the 18F-FDG uptake is measured at a certain time after
administration as a surrogate for Km, the so-called standardized uptake value (SUV). As
the SUV suffers from a number of important shortcomings, discrepancies between Km and the
SUV have been reported which may lead to erroneous conclusions regarding disease
progression based on the SUV.
Alternatively, pharmacokinetic modelling approaches facilitate accurate Km assessment.
Unfortunately, these approaches typically require complex mathematical modelling, lengthy
dynamic PET imaging and/or invasive arterial blood sampling and are therefore not
compatible to current clinical oncologic 18F-FDG PET scanning. However, from these models
it can be derived that at late time points after administration Km can be approximated
using a simplified approach known as the fractional uptake rate (FUR). Our hypothesis is
that the correlation between the FUR and Km is superior compared to the correlation
between the SUV and Km. Therefore we expect that quantification of 18F-FDG PET images
based on the FUR is superior to SUV quantifications.
The results of this study may therefore lead to a new and improved method to quantify
oncologic PET images which may enhance the diagnostic value of PET. In particular, this
method may lead to a more accurate assessment of tumour response to therapy and may
therefore prevent continuation of unsuccessful therapy or termination of a successful
therapy.
Primary objective:
To investigate whether the correlation between the FUR and Km is superior compared to the
correlation between the SUV and Km.
Secondary objectives:
Validation of the FUR in 18F-FDG PET to accurately assess tumour metabolic activity
Km.
To investigate the impact of the use of patient-specific versus a (scaled)
population-based input function on the accuracy of Km assessment using the FUR.
The risks and patient discomfort associated with this scientific study are low. Only
patients are included who already receive an 18F-FDG PET/CT scan as part of standard
care.
Instead of resting on a standard hospital bed for one hour after 18F-FDG injection,
patients will be resting inside the PET/CT system while a dynamic PET acquisition is
performed.
In addition to their standard PET/CT examination, an extra low-dose attenuation CT scan
will be performed resulting in an added radiation exposure of the patient of 3.6 mSv.
Moreover, three additional venous blood samples will be obtained at three time points,
one before and two after 18F-FDG administration will be obtained from the patient.