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  • MRI-based tumor motion char...
    Heerkens, Hanne D; van Vulpen, Marco; van den Berg, Cornelis A.T; Tijssen, Rob H.N; Crijns, Sjoerd P.M; Molenaar, Izaak Q; van Santvoort, Hjalmar C; Reerink, Onne; Meijer, Gert J

    Radiotherapy and oncology, 05/2014, Letnik: 111, Številka: 2
    Journal Article

    Abstract Background and purpose To characterize pancreatic tumor motion and to develop a gating scheme for radiotherapy in pancreatic cancer. Materials and methods Two cine MRIs of 60 s each were performed in fifteen pancreatic cancer patients, one in sagittal direction and one in coronal direction. A Minimum Output Sum of Squared Error (MOSSE) adaptive correlation filter was used to quantify tumor motion in craniocaudal, lateral and anteroposterior directions. To develop a gating scheme, stability of the breathing phases was examined and a gating window assessment was created, incorporating tumor motion, treatment time and motion margins. Results The largest tumor motion was found in craniocaudal direction, with an average peak-to-peak amplitude of 15 mm (range 6–34 mm). Amplitude of the tumor in the anteroposterior direction was on average 5 mm (range 1–13 mm). The least motion was seen in lateral direction (average 3 mm, range 2–5 mm). The end exhale position was the most stable position in the breathing cycle and tumors spent more time closer to the end exhale position than to the end inhale position. On average, a margin of 25% of the maximum craniocaudal breathing amplitude was needed to achieve full target coverage with a duty cycle of 50%. When reducing the duty cycle to 50%, a margin of 5 mm was sufficient to cover the target in 11 out of 15 patients. Conclusion Gated delivery for radiotherapy of pancreatic cancer is best performed around the end exhale position as this is the most stable position in the breathing cycle. Considerable margin reduction can be established at moderate duty cycles, yielding acceptable treatment efficiency. However, motion patterns and amplitude do substantially differ between individual patients. Therefore, individual treatment strategies should be considered for radiotherapy in pancreatic cancer.