What validation tests can be done by the clinical medical physicist while waiting for the standardization of quantitative SPECT/CT imaging?

Abstract

Objective The aim of the study was to assess the accuracy of quantitative SPECT/CT imaging in a clinical setting and to compare test results from two nuclear medicine departments.Methods Phantom studies were carried out with two gamma cameras manufactured by GE Healthcare: Discovery NM/CT 670 and NM/CT 850, used in two nuclear medicine departments.Results The convergence of activity concentration recovery was validated for the two gamma cameras operating in two medical centres using a homogeneous 3D phantom. The comparison of results revealed a 5% difference in the calibration factor Bg. cal; 6% difference in COV, and a 0.6% difference in total activity deviation ∆Atot.Recovery coefficients (RCmax) for activity concentration in spheres of the anthropomorphic phantom was measured for different image reconstruction techniques. RCmax was in the range of 0.2-0.4 for the smallest sphere (ϕ10 mm), and 1.3-1.4 for the largest sphere (ϕ37 mm). Conversion factors for SUVmax and SUVmean for the gamma camera systems used were 0.99 and 1.13, respectively.Conclusions 1) Measurements taken in our study confirmed the clinical suitability of 5 parameters of image quality (Bg. cal- background calibration factor, ∆Atot- total activity deviation, COV- noise level estimation, QH- hot contrast, AM-accuracy of measurements or RC- recovery coefficient) for the validation of SPECT/CT system performance in terms of correct quantitative acquisitions of images. 2) This work shows that absolute SPECT/CT quantification is achievable in clinical nuclear medicine centers. Results variation of quantitative analyzes between centers is mainly related to the use of different reconstruction methods. 3) It is necessary to standardize the technique of measuring the SUV conversion factor obtained with different SPECT/CT scanners.

Physical quantities useful for quality control of quantitative SPECT/CT imaging

“…The variation between centres is mainly caused by the use of different reconstruction algorithms and/or settings. Based on their research, the authors confirmed that the OSEM iterative method with 5 iterations and 15 subsets, without the 3D post-reconstruction filter, is the optimal clinical method for the reconstruction of quantitative images obtained with the NM/CT850 gamma camera [21,12]. On the other hand, for the gamma camera Symbia Intevo, Gnesin et al [2] chose the iterative reconstruction technique with 16 iterations and 4 subsets and Gaussian smoothing of FWHM 7.5 mm (for foci with a diameter greater than 24 mm) as the optimal method.…”