Articles | 2018

Journal of the Royal Society Interface, 2018, in press

The attenuated spline reconstruction technique for single photon emission computed tomography (SPECT)

Nicholas E. Protonotarios, Athanassios S. Fokas, Kostas Kostarelos, George A. Kastis

We present the attenuated spline reconstruction technique (aSRT) which provides
an innovative algorithm for single photon emission computed
tomography (SPECT) image reconstruction. aSRT is based on an analytic
formula of the inverse attenuated Radon transform (IART). It involves the
computation of the Hilbert transforms of the linear attenuation function
and of two sinusoidal functions of the so-called attenuated sinogram. These
computations are achieved by employing the attenuation information provided
by computed tomography (CT) scans and by utilizing custom-made
cubic spline interpolation. The purpose of this work is: (i) to present the
mathematics of aSRT, (ii) to reconstruct simulated and real SPECT/CT
data using aSRT and (iii) to evaluate aSRT by comparing it to filtered backprojection
(FBP) and to ordered subsets expectation minimization (OSEM)
reconstruction algorithms. Simulation studies were performed by using an
image quality (IQ) phantom and an appropriate attenuation map. Reconstructed
images were generated for 45, 90 and 180 views over 360 degrees
with 20 realizations and involved Poisson noise of three different levels
(NL), namely 100% (NL1), 50% (NL2) and 10% (NL3) of the total counts,
respectively. Moreover, real attenuated SPECT sinograms were reconstructed
from a real study of a Jaszczak phantom, as well as from a real
clinical myocardial SPECT/CT study. Comparisons between aSRT, FBP
and OSEM reconstructions were performed using contrast, bias and image
roughness. The results suggest that aSRT can efficiently produce accurate
attenuation-corrected reconstructions for simulated and real phantoms, as
well as for clinical data. In particular, in the case of the clinical myocardial
study, aSRT produced reconstructions with higher cold contrast than both
FBP and OSEM. aSRT, by incorporating the attenuation correction within
itself, may provide an improved alternative to FBP. This is particularly
promising for ‘cold’ regions as those occurring in myocardial ischaemia.