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Table 2 Treatment planning and delivery characteristics

From: Phase II trial on SBRT for unresectable liver metastases: long-term outcome and prognostic factors of survival after 5 years of follow-up

Patient position
 • Supine position with arms above the head
Immobilization device
 • Thermoplastic body mask
 • Styrofoam block for abdominal compression
CT scan
 • Contrast-free and 3 phases contrast-enhanced
 • Acquisition in free quiet breathing mode
 • 3-mm slice thickness
4-dimensional CT (4DCT)
 • In case of lesions located in the postero-superior segments, or with a shift greater than 5 mm on the CT scan
GTV delineation
 • CT scan
 • Co-registration with magnetic resonance imaging (MRI) or positron emission tomography (PET)
ITV and PTV delineation
 • For patients with 4D-CT, an internal target volume (ITV) was defined as the envelope of all GTVs in the different respiratory phases.
 • PTV = ITV + overall isotropic margin of 5 mm
 • PTV = GTV + 7–10 mm in the cranial-caudal axis and 4–6 mm in the anterior-posterior and lateral axes
Prescription dose
 • 75 Gy/ 3 fractions (Full dose)
 • 67.5 Gy/ 3 fractions (Reduction of 10%)
 • 60 Gy/ 3 fractions (Reduction of 20%)
 • 52.5 Gy/ 3 fractions (Reduction of 30%)
Dose constraints for OARs
 • Healthy liver: V15 Gy (volume receiving 15 Gy) < (total liver volume - 700 cm3)
 • Spinal cord: D 0.1 cm3 < 18 Gy
 • Both kidneys: V15 Gy < 35%
 • Duodenum, small bowel, esophagus, and stomach: V21 Gy < 1%
 • Heart: V30 Gy < 1%
 • Ribs: D30 cm3 < 30 Gy
 • dose fall off: from 100 to 30% in 5 mm
IGRT system
 • Megavoltage CBCT before each daily session