Discovery pet ct 600

BAT activity was measured using FDG-PET/CT, using a previously reported method (2 (link)) after slight modifications. Briefly, after fasting for 10-12 h, participants wore light clothes (T-shirt and shorts) and remained in a room at 19^°C for 2 h. After 1 h, the participants received [¹⁸F]FDG (1.7 MBq/kg body weight) intravenously and remained in the same cold conditions for another hour. One hour after [¹⁸F]FDG administration, PET/CT was performed at 24^°C room temperature using a dedicated PET/CT system [Aquiduo (Toshiba Medical Systems, Otawara, Japan), Biograph 16 (Siemens Medical Solutions, Knoxville, TN, USA), or Discovery PET/CT 600 (GE Healthcare, Waukesha, WI, USA)]. Detectable [¹⁸F]FDG uptake into the supraclavicular BAT was assessed by visual judgment. In parallel, the [¹⁸F]FDG uptake was quantified as the maximal standardized uptake value (SUV_max).

We used Discovery PET/CT 600 and Discovery PET/CT 710 scanners (GE Healthcare, Milwaukee, WI, USA). Table 1 shows the features of two PET devices compared herein. The Discovery 600 comprises 24 rings of 512 bismuth germinate (BGO) crystals (4.7 × 6.3 × 30 mm), covering transaxial and axial FOV of 700 and 157 mm, respectively. The spatial resolution at 1 cm from the center of the FOV was 4.9 mm at full width at half maximum (FWHM) according to NEMA NU2-2007 [14 (link)]. The Discovery 710 comprises 24 rings of 576 lutetium-yttrium oxyorthosilicate (LYSO) crystals (4.2 × 6.3 × 25 mm), covering transaxial and axial FOV of 700 and 157 mm, respectively. The spatial resolution at 1 cm from the center of the FOV was 4.7 mm at FWHM according to NEMA [15 (link)].Table 1

Comparison of device features

	Discovery 600	Discovery 710
Transaxial FOV (mm)	700	700
Axial FOV (mm)	157	157
No. of ring	24	24
No. of individual crystals	12,288	13,824
No. of crystals/ring	512	576
No. of image planes	47	47
Crystal size (mm)	4.7 × 6.3 × 30	4.2 × 6.3 × 25
Crystal array per block	8 × 6	9 × 6
Scintillator material	BGO	LYSO
Coincidence window (nsec)	9.5	4.9

All PET/CT scans were performed on a combined in-line system (Discovery PET/CT 600, GE Healthcare, Milwaukee, WI, USA) with a multidetector helical 16-slice CT and integrated full-ring PET. This dedicated system allows for acquisition of co-registered PET and CT images in one step. After the injection of a standard dose of 300 to 340 MBq ¹⁸F-FDG, the PET/CT imaging started with a delay of 60 min. The patients were advised to drink 1,000 ml of oral contrast medium during this uptake time.
The non-enhanced low-dose CT part of the combined scan was acquired with a tube voltage of 120 kV, a tube current of 40 mA, and a tube rotation time of 0.5 s. The imaging range was from the vertex to the upper thighs. Consecutively, the emission PET data acquisition started with an acquisition time of 2 min per bed position. The CT data was used for attenuation correction. CT images were later reconstructed with 3.75-mm slice width, using a fully 3D iterative algorithm (ordered subset expectation maximization (OSEM)). For image post-processing, co-registration, and analysis, the reconstructed images were transferred to a commercially available computer workstation (Advantage Workstation 4.4, GE Healthcare).

BAT activity was measured using FDG-PET/CT as reported previously [14 (link)]. Briefly, after fasting for 10–12 h, subjects wore light clothes (T-shirt and shorts) and remained in a room wherein the temperature was adjusted to 19 °C for 2 h. Intermittently, a towel-wrapped ice block was placed against the soles of their feet. After 1 h, ¹⁸F-FDG (1.66–5.18 MBq/kg body weight) was intravenously administered and the subjects remained in the same cold conditions for another hour. One hour after ¹⁸F-FDG administration, a PET/CT scan was performed at 24 °C using a dedicated PET/CT system (an Aquiduo [Toshiba Medical Systems, Otawara, Japan], Biograph 16 [Siemens Medical Solutions, Knoxville, TN, USA], or Discovery PET/CT 600 [GE Healthcare, Waukesha, WI, USA]). Detectable FDG uptake into the supraclavicular BAT was assessed by visually judging. In parallel, the FDG uptake was semiquantitatively measured as the maximal standardized uptake value (SUV_max). The SUV_max threshold level between the detectable and undetectable was 2.00 [14 (link)].

Patient demographics were recorded, along with relevant oncologic history, laboratory values, and tumor pathology data. Referring physicians completed a questionnaire describing the intended course of treatment before the ¹⁸F-DCFPyL PET/CT scan. Participants were followed up 24 h after radiotracer administration to identify adverse events. A second questionnaire was sent to referring physicians a few weeks after the scan to assess changes in management.
¹⁸F-DCFPyL was synthesized according to a previously published method (13 (link)). The administered activity was scaled by body weight (range, 237–474 MBq), allowing a 10% variation in target activity. After a 4-h fast, participants were injected intravenously with ¹⁸F-DCFPyL. Vital signs were measured before injection, 5–15 min afterward, and after the uptake phase. The subjects could eat between the radiotracer injection and the scan. After a 120-min uptake period, patients were imaged from top of head to mid thigh on a Discovery PET/CT 600 or 690 (GE Healthcare). A CT scan for localization and attenuation correction (120 kV, automatic milliamperage selection [range, 30–200 mA], and noise index of 20) was acquired. PET data were acquired immediately after the CT data over 2–4 min/bed position, adjusted for participant girth, and reconstructed with ordered-subset expectation maximization and point-spread-function modeling.