Ge discovery st pet

All 4D CT images were acquired in cine mode on a GE Discovery ST PET/CT scanner (GE Medical Systems, Waukesha, WI) with a 500 ms tube rotation time; the CT component is an 8‐slice LightSpeed CT. A real‐time processing monitor (RPM; Varian Associates, Palo Alto, CA) served as an external surrogate for organ motion, which provided a respiratory trace of relative abdominal height versus time.
Cine 4D CT acquires images in beam‐width steps that correspond to fixed couch positions to cover the superior–inferior scan extent. Acquiring images for at least 1 breathing cycle per couch position ensures data sufficiency; therefore, the acquisition time per couch position (cine duration) was based on the patient's average breathing cycle plus 1 s for all but the oversampling method. This yields several multislice image segments (8×2.5 mm axial images) per couch position. Images from all acquisition methods were reconstructed using 360° of data every 350 ms following the first 500 ms rotation at each couch position. Acquisitions were obtained at 120 kVp, with a 100 mA tube current for clinical acquisitions and a dose‐sparing 50 mA for experimental acquisitions. Each acquisition was processed to yield a final 4D CT with a set of ten 3D CT volumes, each representing a component breathing phase.