ACCELERATED EM RECONSTRUCTION IN TOTAL-BODY PET - POTENTIAL FOR IMPROVING TUMOR DETECTABILITY

Total-body positron emission tomography (PET) is a useful diagnostic t ool for evaluating malignant disease. However, tumour detection is lim ited by image artefacts due to the lack of attenuation correction and noise. Attenuation correction may be possible using transmission data acquired after or simultaneously with emission data. Despite the elimi nation of attenuation artefacts, however, tumour detection is still ha mpered by noise, which is amplified during image reconstruction by fil tered backprojection (FBP). We have investigated, as an alternative to FBP, an accelerated expectation maximization (EM) algorithm for its p otential to improve tumour detectability in total-body PET. Signal to noise ratio (SNR), calculated for a tumour with respect to the surroun ding background, is used as a figure of merit. A software tumour phant om, with conditions typical of those encountered in a total-body PET s tudy using simultaneous acquisition, is used to optimize and compare v arious reconstruction approaches. Accelerated EM reconstruction follow ed by two-dimensional filtering is shown to yield significantly higher SNR than FBP for a range of tumour sizes, concentrations and counting statistics (Delta SNR = 6.3 +/- 3.9, p < 0.001). The methods develope d are illustrated by examples derived from physical phantom and patien t data.