Discovery st

Because we accrued patients over a period of 14 y, the PET/CT scans had been obtained with multiple scanner types. However, patient preparation and image acquisition protocols were comparable over the years. All scans were acquired using PET/CT cameras, including Discovery LS, Discovery ST, and Discovery STE (all GE Healthcare) or Biograph LSO-16 (Siemens Medical Solutions). No information on the scanner system was available for 22% of the patients. Patients were instructed to fast for at least 6 h before ¹⁸F-FDG administration, and blood glucose levels were required to be less than 200 mg/dL at the time of injection. The scans were acquired from the upper thighs to the base of the skull (5–7 bed positions) 60–90 min after injection of about 400 MBq of ¹⁸F-FDG. CT was performed for attenuation correction and anatomic localization. Immediately after the CT image acquisition, PET data were acquired for 3–5 min per bed position. The attenuation-corrected PET data were reconstructed using an ordered-subset expectation maximization iterative reconstruction.

The Institutional Review Board approved this study and waived the requirement for informed consent. Data acquisition was performed in compliance with all applicable Health Insurance Portability and Accountability Act regulations. Fifty-five patients have been diagnosed with a cytologically-proven intrathyroid metastases matching an extrathyroid primary tumor at our institution between 2002 and 2016. From this group, those patients in whom an ¹⁸F-PET/CT study was obtained were included in this study. A retrospective review of the patient demographics and ¹⁸F-PET/CT appearance of intrathyroid metastases from a remote primary tumor was performed.
¹⁸F-PET/CT scans were performed on a dedicated PET/CT system (Discovery ST, STe, or RX, General Electric Medical Systems, Milwaukee, WI). Scans were acquired to include a region from the orbits through the mid thighs. Scans were acquired 60 to 90 minutes after intravenous administration of ¹⁸F-PET/CT. PET studies were acquired in either 2-dimensional or 3-dimensional acquisition mode at 3–5 minutes per bed position (depending on the patient body mass index).

Patients were asked to refrain from caffeine containing products for at least twelve hours prior to PET imaging, whereas regular outpatient medications were continued. Dynamic rest-stress 82-Rb PET myocardial perfusion imaging was performed on a hybrid PET 16-slice CT scanner (Discovery ST, GE Healthcare) or a hybrid PET 64-slice CT scanner (Discovery 690, GE Healthcare) as previously described.^{11 (link)} Briefly, dynamic rest PET images were acquired after intravenous (IV) injection of 82-Rb. After the rest PET scan, the ARD patients underwent pharmacological stress with regadenoson (n=91, bolus of 0.4 mg over 40 seconds), adenosine (n=7, continuous infusion at a rate of 140 μg/kg/min) or dobutamine (n=3, continuous infusion at a maximum rate of 40 μg/kg/min). Patients without ARDs also underwent stress using regadenoson (n=96), adenosine (n=3) or dobutamine (n=2) using similar administration protocols. At peak stress, 82-Rb was administered via peripheral IV and dynamic PET images were acquired. A low dose CT scan was acquired to permit attenuation correction of PET images.

A combined PET/CT scanner was used using Discovery ST or Discovery 710 GE Medical Systems. All patients fasted for at least 3 hours. Image acquisition started at approximately 60 minutes after injection of 3.5 Megabecquerels (MBq)/kilogram (kg) of IASOdopa (1.8–5 MBq/kg, median 3.4 MBq/kg).
Volumetric regions of interest were placed over the areas of significant ¹⁸F-FDOPA uptake (>background) in the HNPGL. SUVmax, SUVmean and MTV 42% (for tumour with highest SUVmax values) were obtained. Total lesion (TL) uptake was calculated as the product of tumour SUVmean and MTV 42% (defined as the region enclosed by a 42% isocontour around the maximum PET voxel). Tumour size was not reported since our PET/CT was performed without contrast enhancement.