1529 poster PATIENT STABILITY DURING STEREOTACTIC BODY RADIOTHERAPY (SBRT) DELIVERED WITHOUT EXTERNAL IMMOBILIZATION

Stereotactic body radiation therapy for liver metastasis – The linac-based Greater Poland Cancer Centre practice

“…23 According to the SBRT assumptions, the highest dose per fraction (from 5.0 Gy up to 25.0 Gy) 10,12,28 is delivered to small target volumes. Even if the highest scheme of dose per fraction is used, all literature reports underline that if a dose reduction is needed, based on acceptable location of a tumor close to the OARs (esophagus, stomach, bowel and kidneys), a lower dose level for the target is to be chosen.…”

“…An appropriate preparation for the SBRT treatment is started by forming the vacuum pillow on which the patient is positioned frameless in a standard supine position, the patient's arms are abducted alongside the head, and knee support is utilized. 9,10 The CT images are acquired at 3 mm slice spacing in different breathing conditions:…”

“…-free shallow breathing for planning purpose 10,11 ; -deep breathing while maintaining position; -free shallow breathing with contrast enhancement. 10 All CT scans are transferred to the Eclipse V.10.0 Treatment Planning System (Varian Medical Systems, Palo Alto, California, USA).…”

“…10 All CT scans are transferred to the Eclipse V.10.0 Treatment Planning System (Varian Medical Systems, Palo Alto, California, USA). A gross tumor volume (GTV) and organs at risk (OARs) are delineated by a physician on the free breathing CT scan.…”

“…A gross tumor volume (GTV) and organs at risk (OARs) are delineated by a physician on the free breathing CT scan. 10,30 The gross tumor volume is considered to be identical with the clinical target volume (CTV) and expanded by 5 mm margin (the exception being by 10 mm in the cranio-caudal direction) to create the planning target volume (PTV) [11][12][13] for the respiratory motion observed at the time of simulation. The OARs may include healthy organs (liver for which the PTV volume is subtracted, kidneys, spinal cord, stomach, esophagus, bowel, heart).…”