肿瘤放射物理学（甄鑫）第一讲 History of Radiantion Therapy.pptVIP

* Accuray CyberKnife (3) 3D images are obtained through spiral CT, CT-on-rail or Cone Beam CT. Siemens Primatom use the so-called CT-on-rail technology: An additional CT is mounted on the opposite side of the linac, and the CT shares the same bed with the linac. Before every fraction of the treatment, patient is performed CT scan to obtain the current anatomical information, and use this current CT image to register with the planning CT, thus, organ deformation can be found, as well as set-up errors. Tomotherapy The advantages of 3D cone-beam CT images in Arstite, Synergy and Trilogy: ①3D images can provide 6 degrees of freedom (3 translation and 3 rotation) of the setup errors. In contrast, 2D images can only provide 5 degrees of freedom (3 translational and 2 rotational) ②Deformable image registration (DIR) can be used to account for tissue deformation based 3D images ③The initial treatment plan can be deformed to current 3D volume via DIR, e.g. the contours, and the dose is recalculated and the plan is re-optimized ④To facilitate dose accumulation IMRT—动态旋转(IMAT) Subfield 1 Subfield 2 Subfield 3 Subfield 1 Subfield 2 Subfield 3 Subfield 1 Subfield 2 Subfield 3 Subfield 1 Subfield 2 Subfield 3 Subfield 1 Subfield 2 Subfield 3 Subfield 1 Subfield 2 Subfield 3 Subfield 1 Subfield 2 Subfield 3 Subfield 1 Subfield 2 Subfield 3 L1 L2 L3 Every 5~10 deg There might be up to 72 fields * IMAT Varian—RapidArc Elekta—VMAT(Volumetric Arc Therapy) Irradiation is delivered during one arc : Varying gantry rotation speed Varying MLC-positioning Varying dose rate VMAT Video Possible advantages of IMAT1. Dose distributions that are as good or better than IMRT.2. Lower MU than for IMRT plans.3. Decreased treatment time. IMRT IMAT So what? IMAT vs IMRT: The same target coverage but an decreased dose to OAR. Much faster! High modulation, small beams, tight margins, steep dose gradients, multiple target