Abstract:
Objective To establish a low-dose but image-comparable respiratory-gated PET/CT(RG PET/CT) protocol based on 30 mA tube current plus other improved scanning parameters, such as the tube current, the number of respiratory phase and length of breathing cycle.
Methods Twenty-six patients with 18F-FDG-intaking lung nodules underwent one-bed standard-dose PET/CT(120 mA, 2 min/bed)and low-dose RG PET/CT(30 mA, 6 respiratory phases, 1min/phase). The radiation dose and image quality were analyzed subsequently with signal to noise ratio(SNR)for PET and the homogeneity, noise level for CT in the water phantom respectively. Otherwise the CT images were both visual evaluated by two experienced doctors. In addition, different respiratory cycle was simulated to observe its relation with radiation dose.
Results The effective dose of low-dose RG PET/CT was 4.88~7.69 mSvmean(5.68±0.83) mSv. The PET SNR showed no significance between groups. The homogeneity of 30 mA is good(< 5 HU), although noise level was high, the visual character like lobulation, speculation of lung nodule was superior in some respiratory phases. The radiation dose was positively correlated with respiratory cycle.
Conclusions The performance of low-dose RG PET/CT was comparable to those of standard-dose PET/CT based on a protocol with 30 mA tube current, 6 respiratory phases and breathing state of eupnoea. It produced a much lower radiation exposure and the image quality was enough for clinical use such as delineation of tumor active target, characterization and staging of lung nodules, etc.
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