Biograph truev

Patient preparation in the PET unit and PET acquisition and reconstructions was performed as per the European Association of Nuclear Medicine (EANM) guidelines for PET tumor imaging [18 (link)], our PET unit being EANM research Ltd. (EARL) accredited since 2015 [19 (link),20 (link)]. ¹⁸F-FDG was injected after the glucose level had been checked to be <200 mg/dL in patients who had been fasting for at least 4 h. Patients were provisionally scanned 60 min after the tracer injection. They were scanned from the base of the skull to mid-thigh with the arms on their sides for upper limb melanoma patients, or whole-body scanned for patients with primary melanoma of the lower limb or in patients with known distal subcutaneous metastases.
Two different PET/CT scanners were used: a Vereos system (Philips Medical Systems. Cleveland OH) and a Biograph TrueV with extended field-of-view (Siemens Medical Solutions, Erlangen, Germany). Details regarding acquisition and reconstruction parameters can be found elsewhere [21 (link)].

Eleven PET/CT scanners were used for the robustness study: n. 2 Discovery ST (S1, S2) [17 (link)], n. 1 Discovery STE (S3) [18 (link)], n. 2 Discovery 600 (S4, S5) [19 (link)], and n. 1 Discovery 690 (S6) [20 (link)] (GE Healthcare, Milwaukee, WI), n. 1 Biograph HI-REZ (S7) [21 (link)] and n. 1 Biograph TRUEV (S8) [22 (link)] (SIEMENS Medical Solutions, Knoxville, TN), n. 1 Gemini XL (S9) and n. 2 Gemini TF (S10, S11) [23 (link)] (Philips Medical Systems, Cleveland, OH). The technical characteristics and physical performances of the PET/CT scanners were derived from factory data and/or previous publications and are reported in Table 1.

PET/CT acquisitions were performed using a PET/CT scanner (Biograph TrueV, Siemens Medical Solutions) with a six-slice spiral CT component and an extended field-of-view of 21.6 cm. Patients were asked to fast for ≥ 6 h before ¹⁸FDG injection (4.0 ± 0.2 MBq per kg). Blood glucose level was 6.0 ± 1.7 mmol/l. WB PET/CT images were performed 58 ± 3 min post injection from mid-thigh to the base of the skull with an acquisition time per bed position of 2 min and 40 s in patients of low and average weight (i.e. body mass index [BMI] < 25 kg/m²) or 3 min and 40 s in overweight patients (i.e. BMI ≥ 25 kg/m²). HN PET was performed either immediately after the WB acquisition and patient repositioning (3 ± 2 min between WB and HN PET, 14 patients) or after the WB acquisition of the next-scheduled patient (18 ± 5 min between WB and HN PET, 7 patients). HN PET/CT data sets were acquired in list-mode (LM) using a single-bed position of 10 min from the base of the skull to the superior mediastinum. All patients were repositioned with arms along the chest. A low-dose CT scan was acquired prior to HN PET/CT with the same longitudinal field of view. CT parameters were set to 100 mAs and 130 kV, slice thickness of 2.5 mm and pitch 1.

After a 15-min rest in a warm room, patients who had been fasting for 6 h were injected with ¹⁸F–FDG. The injected activity, capillary blood glucose level at injection time and the delay between injection and the start of the acquisition, height and body weight were recorded (acquisition parameters were extracted from the DICOM headers). Body Mass Index (BMI) was calculated as follows: $$\mathit{BMI}=\frac{\mathit{\text{body weight}}\left(\mathit{kg}\right)}{{\mathit{\text{height}}}^2\left(m^2\right)}$$
All PET imaging studies were performed on a Biograph TrueV (Siemens Medical Solutions) with a 6-slice spiral CT component. Technical details regarding this system can be found elsewhere [9 (link)]. CT acquisition was performed first, with the following parameters: 60 mAs, 130 kV, pitch 1 and 6 × 2 mm collimation. Subsequently, the PET emission acquisition was performed in 3-D mode. Patients were scanned from the skull base to the mid-thighs, with time per bed acquisitions of 160 and 220 s for normal weight (BMI <25 kg/m²) and overweight patients (BMI ≥25 kg/m²), respectively.
Raw data were reconstructed with a PSF reconstruction algorithm (HD; TrueX, Siemens Medical Solution) with three iterations and 21 subsets and without filtering. Matrix size was 168 × 168, resulting in a 4.07 × 4.07 × 4.07 mm voxel size. Scatter and attenuation corrections were applied based on the CT scan.

All ¹⁸F-FDG PET/CT acquisitions were performed on a Biograph TrueV (Siemens Healthineers) before any treatment. Patients were fasted during at least 6 h. A high-resolution (HR) breast-dedicated bed position (6 min per bed position) was acquired 75 min after the radiopharmaceutical injection. Data were reconstructed using an algorithm with point spread function (PSF) modeling (HD; TrueX, Siemens Healthineers, 3 iterations, and 21 subsets) with no post-filtering and a 512² matrix size leading to voxels of 1.3 × 1.3 × 1.9 mm (19 (link)).