Variability in lutetium-177 SPECT quantification between different state-of-the-art SPECT/CT systems

EJNMMI Physics

Table 2 Reconstruction/quantification parameters and processing software used in this study. Quantification packages Q. Metrix, xSPECT Quant, and Broad quantification enable quantitative reconstructions in the scanner software

System	Discovery NM/CT 670 Pro	Symbia Intevo Bold	Symbia T16 system 1	Symbia T16 system 2	All (standardized)
Imaging center	Leiden University Medical Center	University Medical Center Utrecht	Radboud University Medical Center	Erasmus University Medical Center	All
Reconstruction	OSEM^a + Evolution with PSF^a correction	WCG^a + xSPECT with PSF^a correction	OSEM^a + Flash 3D with PSF^a correction	OSEM^a + Hybrid Recon V3.0.0 with PSF^a correction	OSEM^a + Hybrid Recon V3.0.0 with PSF^a correction
Quantification	Q.Metrix	xSPECT Quant/Broad Quantification^b	Manual analysis	Hermes SUV SPECT	Hermes SUV SPECT
Iterations	9^d	6	4	5	5
Subsets	10	8	8	16	16
Post-reconstruction filter	None	5 mm (Gaussian)	4 mm (Gaussian)	5 mm (Gaussian)	5 mm (Gaussian)
Attenuation correction	CT based^c	CT based^c	CT based^c	CT based^c	CT based^c
Scatter Correction	DEW^a (170 ± 10%)	DEW^a (170 ± 10%)	DEW^a (170 ± 10%)	Monte Carlo-based	Monte Carlo-based
Reconstruction voxel size	2.0 × 2.0 × 2.0 mm^{3 e}	4.9 × 4.9 × 4.9 mm³	4.8 × 4.8 × 4.8 mm³	4.8 × 4.8 × 4.8 mm³	4.8 × 4.8 × 4.8 mm³

^a OSEM ordered subset expectation maximization; WCG weighted conjugate gradient, PSF point spread function, DEW double energy window
^b For xSPECT Quant and Broad quantification separate measurements were performed
^c Bilinear conversion of HU into attenuation coefficients at 208 keV
^d Settings were not according to vendor recommendation but to the literature [13]
^e Interpolation to 2.0 × 2.0 × 2.0 mm³ voxels by Q. Metrix for quantification, as recommended by the vendor