Simulation of PET data for modelling
Simulation of regional PET TACs
Simulation of PET frames
The conventional PET data analysis requires instantaneous values of tracer concentration in the tissue at each time point. However, a dynamic PET study consists of series of integral measurements over time "frames". Since in bolus studies the tracer concentration changes during the frame, instantaneous tracer concentrations can not be derived from integrated PET data at any given data point. Usually it is assumed that the average tracer concentration during a frame represents the instantenous concentration at frame middle time point ("midframe approximation", see Buchert et al., 2003). This may be appropriate if time frames are relatively short.
You can use program fr4sim to simulate the effects of PET time frames for regional TACs.
Simulation of noise
Making input data for simulations
- Calculate average TAC from several measured plasma curves
- Extrapolate plasma TAC with 1-exponential function
- Fit a function to measured plasma or blood TAC
Useful tools for working with simulated curves
- Combine/extract TACs from datafiles
- Delete TACs from datafiles
- Rename TACs
- Double the number of samples
- Add sequential plane numbers
- Arithmetic calculations for TACs
- Interpolate TAC to decreasing time intervals
- Executing the same command for several datafiles with one command
- Statistics from result files
Simulation of PET images and sinograms
- Make image files from simulated TACs
- Make sinogram from dynamic image
- Combine simulated sinogram or image planes
- Simulation of patient movement
- References to PET simulators
Important constants needed in simulations
- Vascular volume fraction
- Regional hematocrit
- Ratio of grey and white matter blood flow is 2.8 ± 0.35 [Østergaard et al 1999]
- Water content (%): plasma 93-95 (mean 94), blood 80.5-80.8, RBC 63,
brain 76.3-78.5 (mean 77.4), skeletal muscle 68.9-80.3 (mean 79),
kidneys 76 (Reference Man); adipose tissue 11.4 - 30.5% (Duck 1990)
Alternatively, Hald (1946) measured that water content in human plasma is 0.93 ml/ml and in RBC 0.72 ml/ml, then human RBC to plasma water content ratio is 0.77 ml/ml - Specific gravity (g ml-1): plasma 1.0266; brain 1.04; skeletal muscle 1.04; adipose tissue 0.92; kidneys 1.06; liver 1.08 (Reference Man)
- Rat: brain blood flow, volume and hematocrit (Cremer and Seville, 1983)
