Fig. 3

Plan comparison study on different CT from the same patient selected for spacer positioning at CNAO. a Different CIRT plans depicted on axial images at the same anatomical level for the same chordoma patient. Red lines for GTV and green lines for CTV are included within the prescription dose isodose in both CIRT plans of 70.4 Gy (RBE). In the upper panel, the digestive area (rectal wall in green and intestine in blue) is contiguous to the prescribed dose isodose. In the lower panel, the digestive tract is far away from irradiated area due to the spacer (pointed by a red arrow). b Comparison of DVH for GTV (red), PTV (pink), and digestive tract (rectum green, intestine blue) dose coverage from the two CIRT plans compared in a. Coverage of the tumor is higher with the spacer CIRT plan (dotted lines) compared to the plan without it (continuous lines). With the CIRT spacer, plan dose sparing to the digestive tract is achieved