Is iterative reconstruction an alternative to filtered backprojection in routine processing of dopamine transporter SPECT studies?
In general, striatal dopamine transporter (DAT) binding is assessed by use of data reconstructed by filtered backprojection (FBP). The aim of this study was to investigate whether the use of an iterative reconstruction algorithm (ordered-subset expectation maximization [OSEM]) may provide results comparable to or even better than those obtained by standard FBP.


METHODS
In 50 patients with parkinsonian syndromes, SPECT scans were acquired 4 h after injection of 185 MBq of (123)I-fluoropropyl-2beta-carbomethoxy-3beta-(4-iodophenyl)tropane ((123)I-FP-CIT) by use of a triple-head gamma-camera fitted with low-energy, high-resolution fanbeam collimators. After reconstruction by FBP and OSEM, data were filtered with a Butterworth filter and corrected for attenuation. Patient studies were automatically fitted to a mean template with a corresponding 3-dimensional (3D) volume-of-interest map covering the striatum, caudate, and putamen as well as an occipital reference region to calculate specific DAT binding. In addition, studies with an anthropomorphic 3D striatal phantom were performed to mimic different pathologies.


RESULTS
Visual assessment of phantom and patient data suggested a better separation between the caudate and the putamen in studies reconstructed by OSEM than in those reconstructed by FBP. There was an excellent correlation between specific DAT binding assessed by OSEM and that assessed by FBP (R(2) values: striatum, 0.999; caudate, 0.998; putamen, 0.998). Mean specific striatal binding obtained by OSEM was approximately 6% lower than that obtained by FBP. In no case was diagnostic information from OSEM inferior to that from FBP.


CONCLUSIONS
Iterative reconstruction of (123)I-FP-CIT SPECT studies for the assessment of DAT is feasible in routine clinical practice. A close correlation between FBP and OSEM data suggested that the latter also allow reliable quantification of DAT binding. Because of a better separation between the caudate and the putamen in the visual evaluation, as suggested by phantom and patient studies, OSEM may even be considered the preferable approach.
Koch
Walter
W
Department of Nuclear Medicine, University of Munich, Munich, Germany. walter.koch@med.uni-muenchen.de
Hamann
Christine
C
Welsch
Julia
J
Pöpperl
Gabriele
G
Radau
Perry E
PE
Tatsch
Klaus
K
D000328:Adult; D000368:Aged; D000465:Algorithms; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007457:Iodine Radioisotopes; D008875:Middle Aged; D009716:Numerical Analysis, Computer-Assisted; D010300:Parkinson Disease / Q000000981:diagnostic imaging* / Q000378:metabolism*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014326:Tropanes / Q000493:pharmacokinetics*
D050483:Dopamine Plasma Membrane Transport Proteins; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D014326:Tropanes; C087552:2-carbomethoxy-8-(3-fluoropropyl)-3-(4-iodophenyl)tropane