Journal of Computer Assisted Tomography · 1979 · 444 citations · 1 references
Computed TomographyEngineeringMeasurementInaccurate Attenuation CorrectionPositron Emission TomographyCalibrationCt ScanPhoton-counting Computed TomographyInstrumentationNuclear MedicineRadiologyHealth SciencesMedical ImagingMedical Image ComputingRadiographic ImagingPositron EmissionBiomedical ImagingEffective Total CountsTomography
The study examined how object size influences PET’s ability to quantify isotope concentrations in cross‑sectional images. The authors measured the relationships between apparent isotope concentration, image size, and true object size across three PET resolutions and four convolution filters. They found that objects at the instrument resolution are underestimated by up to 50 % in isotope concentration, whereas objects larger than 1.0 FWHM can be accurately sized and quantified, allowing practical compensation schemes, while smaller objects suffer severe sensitivity loss and large correction factors, yet the results agree with theoretical predictions.
The effect of object size on the capability of positron emission computed tomography to measure isotope concentrations in a cross section was studied. The relationship between the apparent isotope concentration in an image and the true concentration was measured as a function of object size for three instrument resolutions and four convolution filters. The relationship between image size and object size was also measured under the same conditions. Depression of apparent isotope concentration in an image for objects equal in size to the instrument resolution (FWHM) was significant (50% for a cylinder and 25% for a bar). For objects larger than 1.0 FWHM, accurate object sizes can be estimated from the images. Thus, reasonably accurate and practical schemes of compensation for object size effects can be implemented for objects larger than 1.0 FWHM. Accuracy in quantitating isotope concentrations in smaller objects is seriously compromised by the loss of sensitivity to the object size and the large correction factors required to compensate for instrument response. The results of the measurements were found to be in good agreement with theoretical predictions for ideal systems of comparable resolution.
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