Quantification of dopaminergic neurotransmission SPECT studies with 123I-labelled radioligands. A comparison between different imaging systems and data acquisition protocols using Monte Carlo simulation.
OBJECTIVE
(123)I-labelled radioligands are commonly used for single-photon emission computed tomography (SPECT) imaging of the dopaminergic system to study the dopamine transporter binding. The aim of this work was to compare the quantitative capabilities of two different SPECT systems through Monte Carlo (MC) simulation.


METHODS
The SimSET MC code was employed to generate simulated projections of a numerical phantom for two gamma cameras equipped with a parallel and a fan-beam collimator, respectively. A fully 3D iterative reconstruction algorithm was used to compensate for attenuation, the spatially variant point spread function (PSF) and scatter. A post-reconstruction partial volume effect (PVE) compensation was also developed.


RESULTS
For both systems, the correction for all degradations and PVE compensation resulted in recovery factors of the theoretical specific uptake ratio (SUR) close to 100%. For a SUR value of 4, the recovered SUR for the parallel imaging system was 33% for a reconstruction without corrections (OSEM), 45% for a reconstruction with attenuation correction (OSEM-A), 56% for a 3D reconstruction with attenuation and PSF corrections (OSEM-AP), 68% for OSEM-AP with scatter correction (OSEM-APS) and 97% for OSEM-APS plus PVE compensation (OSEM-APSV). For the fan-beam imaging system, the recovered SUR was 41% without corrections, 55% for OSEM-A, 65% for OSEM-AP, 75% for OSEM-APS and 102% for OSEM-APSV.


CONCLUSIONS
Our findings indicate that the correction for degradations increases the quantification accuracy, with PVE compensation playing a major role in the SUR quantification. The proposed methodology allows us to reach similar SUR values for different SPECT systems, thereby allowing a reliable standardisation in multicentric studies.
Crespo
Cristina
C
Unitat de Biofísica i Bioenginyeria, Departament de Ciències Fisiològiques I, Facultat de Medicina, Universitat de Barcelona-IDIBAPS, Casanova 143, 08036 Barcelona, Spain.
Gallego
Judith
J
Cot
Albert
A
Falcón
Carles
C
Bullich
Santiago
S
Pareto
Deborah
D
Aguiar
Pablo
P
Sempau
Josep
J
Lomeña
Francisco
F
Calviño
Francisco
F
Pavía
Javier
J
Ros
Domènec
D
D000465:Algorithms; D001921:Brain / Q000000981:diagnostic imaging* / Q000502:physiology*; D004298:Dopamine / Q000502:physiology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007457:Iodine Radioisotopes; D008024:Ligands; D009010:Monte Carlo Method; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000503:physiopathology; D019047:Phantoms, Imaging; D009435:Synaptic Transmission / Q000502:physiology*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods* / Q000706:statistics & numerical data
D007457:Iodine Radioisotopes; D008024:Ligands; D004298:Dopamine