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Figure 1: Gamma knife planning for TN. (a) Trigeminal nerve is detected on T2-weighted image (arrow). (b) A 4-mm diameter radiation dose is administered 2–4 mm anterior from the junction of the trigeminal nerve and pons covering the trigeminal nerve (yellow line). This radiation dose is placed anterior enough to keep the 20% isodose line (green line) on the brainstem surface so that brainstem receives no more than 15 Gy, which is the critical toxic dose for the brainstem. Since the brainstem dose is kept below the critical toxic dose, no shielding was applied in the present study

Figure 1: Gamma knife planning for TN. (a) Trigeminal nerve is detected on T2-weighted image (arrow). (b) A 4-mm diameter radiation dose is administered 2–4 mm anterior from the junction of the trigeminal nerve and pons covering the trigeminal nerve (yellow line). This radiation dose is placed anterior enough to keep the 20% isodose line (green line) on the brainstem surface so that brainstem receives no more than 15 Gy, which is the critical toxic dose for the brainstem. Since the brainstem dose is kept below the critical toxic dose, no shielding was applied in the present study