Symbia intevo 6

All patients underwent whole-body planar imaging (scanned 2.5–4.5 h after injection)with a low-energy high-resolution collimator and quantitative SPECT/CT (Siemens Symbia Intevo 6, USA) on planar scintigraphy high-uptake regions. SPECT was acquired at a mean patient dose of 831 ± 44 MBq (22.45 ± 1.19 mCi, range: 20.00–25.20 mCi) ^99mTc-MDP intravenous injection (from HTA Co., Ltd., and Beijing Senke Pharmaceutical Co., Ltd) and 0–3.5 h after the whole-body planar bone scan. Images were captured using a 256 × 256 matrix size and 6 degrees rotation/step, 15 seconds/projection. CT scans were performed using adaptive dose modulation at 130 kV and 60 mAs (Siemens Care Dose). The CT data were reconstructed using B60s medium sharp with a slice thickness of 2.5 mm. SPECT images were reconstructed using the Flash 3D algorithm (xSPECT Skeletal mode) with eight iterations, four subsets, and a Gaussian filter. The SPECT reconstructed values were decay-corrected to the time of injection and final values of quantitative radioactivity concentrations were obtained to allow SUV body weight quantification (SUVbw) on post-processed images and measurement of SUVmax (g/ml) using the xSPECT reconstruction algorithm. SUVmax was defined as the pixel value with the highest activity concentration within a volume of interest (VOI).

Data were acquired on five state-of-the-art SPECT/CT systems from three manufacturers: a Discovery NM/CT 670 Pro (GE Healthcare, Milwaukee, USA), a Precedence 6 (Philips Healthcare, Best, The Netherlands), a Symbia Intevo 6, and two Symbia T16’s (Siemens Healthineers, Erlangen, Germany) (Table 1).
Table 1

Characteristics of all used SPECT/CT systems with LEHR collimator

System	Discovery NM/CT 670 Pro	Precedence 6	Symbia Intevo 6	Symbia T16
Detector crystal	3/8” NaI	3/8” NaI	3/8” NaI	3/8” NaI
PMT*	59	55	59	59
FOV*	40 × 54 cm	38.1 × 50.8 cm	38.7 × 53.3 cm	38.7 × 53.3 cm
Hole shape	Hexagonal	Hexagonal	Hexagonal	Hexagonal
Number of holes (× 1000)	Not specified	86.4	148	148
Collimator hole diameter	1.50 mm	1.40 mm	1.11 mm	1.11 mm
Hole length	35 mm	32.8 mm	24.05 mm	24.05 mm
Septal thickness	0.2 mm	0.152 mm	0.16 mm	0.16 mm
Sensitivity for 99mTc @ 10 cm	72 cps/MBq	66 cps/MBq	91 cps/MBq	91 cps/MBq
Septal penetration @ 140 keV	0.3%	1.3%	1.5%	1.5%
Planar resolution†	7.4 mm	7.4 mm	7.5 mm	7.5 mm
SPECT central resolution†	6.4 mm	4.4 mm	4.4 mm	4.4 mm
SPECT peripheral radial resolution†	5.7 mm	4.2 mm	4.0 mm	4.0 mm
SPECT peripheral tangential resolution†	5.1 mm	4.3 mm	3.9 mm	3.9 mm

* (C)FOV (center) field of view, PMT photomultiplier tube

† Spatial resolution without scatter (LEHR collimator at 10 cm, (full width at half maximum (FWHM) in CFOV [mm], 3/8” crystal)