ESTRO 37 Abstract book

S1220

ESTRO 37

and 0.995 (range 0.968 – 1.027) for film. Being off-axis did not compromise the dose accuracy (see the attached figures). Gamma criteria of 5% dose, 2 mm distance to agreement, and 50% threshold assessed with a minimum passing rate of 90% reliably detected introduced dosimetric and geometric errors while allowing for acceptable uncertainties. Increasing the threshold from our normal value of 10% to 50% allows for better assessment of small, distributed targets.

respiratory motion demonstrate positive correlations in cuneus, cerebellum, middle cingulate cortex and middle temporal gyrus, and negative correlations in anterior cingulate cortex, sensorimotor area and PCu/PCC.

Fig 1. Statistical T-maps of inter-state neural activity differences. The color-bar shows the statistical t-value for all maps. Red/blue indicates increased/decreased activity in hypnosis state. T-maps are threshold at voxel p<0.005, AlphaSim-corrected, cluster size >324mm 3 (fALFF= fractional amplitude of low frequency fluctuation; ReHo= regional homogeneity; DC= degree centrality; L= left hemisphere; R = right hemisphere; IPL= inferior parietal lobule; CAL = cerebellum anterior lobe; SFGdor = dorsolateral superior frontal gyrus; PCu = precuneus; PCC = posterior cingulate cortex; IFGtri = triangular part of inferior frontal gyrus; MFG = middle frontal gyrus; CPL = cerebellum posterior lobe; MPFGorb = medial orbital of prefrontal gyrus).

Conclusion VMAT-based, single isocenter SRS for multiple targets was validated for targets as small as 6 mm diameter (0.11 cm3) and up to 5.6 cm off-axis. Patient-specific QA with the ArcCheck device can reliably detect clinically significant inaccuracies. EP-2203 A functional MRI study of hypnosis for respiratory motion control during radiotherapy Y. Liu 1 , R. Li 1 , Y. Xie 1 1 Shenzhen Institutes of Advanced Technology- Chinese Academy of Sciences, Institute of Biomedical and Health Engineering, shenzhen, China Purpose or Objective Hypnosis has been proven effective in clinical therapy as a psychological technology and respiration control is essential in radiotherapy. This study examined the effect of hypnosis for respiration control and investigated the altered spontaneous brain activity as well as neural correlation of respiratory motion. Material and Methods Resting state functional magnetic resonance imaging was applied to an intra-subject design of eight healthy subjects in normal state (NS) and hypnosis state guided by hypnotist (HS). Results The results show that significant lower respiratory amplitude in HS (14.23±3.40mm in NS, 12.79±2.49mm in HS, p=0.0350), with mean amplitude deduction of 9.2%. Inter-state difference of neural activity show activations in visual cortex and cerebellum, and deactivations in prefrontal cortex and precuneus/posterior cingulate cortex (PCu/PCC) in HS (Figure 1). Within these regions, coupled negative neural activity and respiratory motion in visual cortex, decoupled positive correlation in PCu/PCC and decoupled negative correlation in DLPFC (Figure 1). Moreover, voxel-wise neural correlations of

Fig 2. Correlation of neural activity and respiratory motion in brain regions showing inter-state neural activity difference. (A) Correlation of ReHo and respiration in left precuneus/posterior cingulate cortex (L-PCu/PCC). (B) Correlation of ReHo and respiration in left triangular part of inferior frontal gyrus and middle frontal gyrus (L-IFGtri/MFG). (C) Correlation of DC and respiration in left precuneus/cuneus (L-PCu/Cuneus). (D) Correlation of DC and respiration in right calcarine. ReHo=regional homogeneity; DC=degree centrality; NS=normal state; HS=hypnosis state; TEI=tail end of inspiration; TEE=tail end of expiration. Conclusion These findings reveal the involvement of cognitive, executive control and sensorimotor processing in the control mechanisms of hypnosis for respiration, and shed new light on hypnosis performance in interaction of psychology, physiology and cognitive neuroscience. EP-2204 Impact Of A Motion Correction Method (Q.Static) In The Definition Of The Metabolic Tumor Volume R. Martin Vaello 1 , G. Reynés-Llompart 1 , D. Mateo- Navarro 2 , A. Sabaté-Llobera 2 , E. Montes 1 , I. Sancho 1 , J.