IMRT

Example ITV vs. Tracking approach

PTV definition: Tracking: CTV=GTV, PTV TR =CTV + 5mm isotropically ITV backup plan: ITV= sum CTV all phases + 5 mm isotropically (for CBCT guidance) PTV ITV =ITV+5mm isotropically PTV TR = 18.3 ccm , PTV ITV =30.2 ccm (39% PTV volume reduction)

Patient History: Male, 74 years old: 7/2009: primary disease: cT4N3M0, treated induction chemo , consolidation RT 8/2010: metastatic disease: Tarceva 5/2012: progression of solitary metastasis lower left lobe , RT 2x20 Gy Delineation: On 60% phase in stable exhale ( volume 4.30 ccm ) Size: AP: 2.6 cm, CC: 2.2 cm, LR: 2.2 cm Motion: Visicoil marker 0.75 mm diameter, 10 mm length Amplitude CC of 14mm p2p in 4D CT

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