Performance Characteristics of the Whole-Body Discovery IQ PET/CT System. Scientific Publication

Purpose:
The aim of this study was to assess the physical performance of a new PET/CT system Discovery IQ 5 Rings (General Electric, Milwaukee, WI).

Methods:
Performance measurements were obtained using the NEMA NU2-2012 methodology. Image quality was extended by accounting for different acquisition parameters (lesion-to-background ratios of 8:1, 4:1 and 2:1 and acquisition times) as well as different reconstruction algorithms (VPHD, VPHD-S and Q. Clear). Tomographic reconstruction was also assessed using a Jaszczak phantom.

Additionally, a total of thirty patient lesions were analyzed to account for differences on reconstruction algorithms in terms of lesion volume and SUV quantification.

Results:
Spatial resolutions ranged from 4.2 mm at 1 cm to 8.5 mm at 20 cm. Sensitivity measured in the center and at 10 cm was 22.8 and 20.4 kps/kBq, respectively. The measured noise equivalent count rate (NECR) peak was 124 kcps at 9.1 kBq/cm3 The scatter fraction was 36.2%.

The accuracy of correction for the count losses and randoms was 3.9%. In the image quality test the contrast recovery for VPHD/VPHDS/Q. Clear ranged between 18/18/13% (10 mm sphere diameter, ratio of 2:1) and 68/67/81% (37 mm sphere diameter, ratio of 8:1).

The background variability was between 3.4/3.0/2.1% (ratio 2:1) to 5.5/4.8/3.7% (ratio 8:1). On Q. Clear reconstruction, the decrease of the β value has the effect of increasing the contrast recovery coefficients and the background variability.

The Jaszczak phantom presented an overall image quality increase when using a reconstruction algorithm that models the point-spread function (PSF), moreover Q. Clear increased signal-to-noise ratio. Lesions analyzed for VPHD-S and Q. Clear presented a SUVmean of 6.5±3 and 7±3 (p<0.01), respectively, and a SUVmax of 11±4.8 and 12±4 (p<0.01). No significant lesion mean volume differences were found between algorithms.

Conclusion:
Discovery IQ PET/CT with 5 ring block detectors has the highest overall performance of the Discovery BGO based scanners, with improved sensitivity and count rate performance. The Q.Clear reconstruction improves the PET image quality, with higher recovery coefficients and lower background variability.

CITATION J Nucl Med. 2017 Mar 16. pii: jnumed.116.185561. doi: 10.2967/jnumed.116.185561