DMIDR 장치의 재구성 알고리즘 별 성능 평가

Performance Evaluation of Reconstruction Algorithms for DMIDR

Purpose DMIDR(Discovery Molecular Imaging Digital Ready, General Electric Healthcare, USA) is a PET/CT scanner designed to allow application of PSF(Point Spread Function), TOF(Time of Flight) and Q.Clear algorithm. Especially, Q.Clear is a reconstruction algorithm which can overcome the limitation of OSEM(Ordered Subset Expectation Maximization) and reduce the image noise based on voxel unit. The aim of this paper is to evaluate the performance of reconstruction algorithms and optimize the algorithm combination to improve the accurate SUV(Standardized Uptake Value) measurement and lesion detectability. Materials and Methods PET phantom was filled with 18F-FDG radioactivity concentration ratio of hot to background was in a ratio of 2:1, 4:1 and 8:1. Scan was performed using the NEMA protocols. Scan data was reconstructed using combination of ①VPFX(VUE point FX(TOF)), ②VPHD-S(VUE Point HD+PSF), ③VPFX-S (TOF+PSF), ④QCHD-S-400((VUE Point HD+Q.Clear(β-strength 400)+PSF), ⑤QCFX-S-400(TOF +Q.Clear (β-strength 400)+PSF), ⑥QCHD-S-50(VUE Point HD+Q.Clear(β-strength 50)+PSF) and ⑦QCFX-S-50 (TOF+Q.Clear(β-strength 50)+PSF). CR(Contrast Recovery) and BV(Background Variability) were compared. Also, SNR(Signal to Noise Ratio) and RC(Recovery Coefficient) of counts and SUV were compared respectively. Results VPFX-S showed the highest CR value in sphere size of 10 and 13 ㎜, and QCFX-S-50 showed the highest value in spheres greater than 17 ㎜. In comparison of BV and SNR, QCFX-S-400 and QCHD-S-400 showed good results. The results of SUV measurement were proportional to the H/B ratio. RC for SUV is in inverse proportion to the H/B ratio and QCFX-S-50 showed highest value. In addition, reconstruction algorithm of Q.Clear using 400 of β-strength showed lower value. Conclusion When higher β-strength was applied Q.Clear showed better image quality by reducing the noise. On the contrary, lower β-strength was applied Q.Clear showed that sharpness increase and PVE(Partial Volume Effect) decrease, so it is possible to measure SUV based on high RC comparing to conventional reconstruction conditions. An appropriate choice of these reconstruction algorithm can improve the accuracy and lesion detectability. In this reason, it is necessary to optimize the algorithm parameter according to the purpose.