Precision Radiotherapy Delivery in Preclinical Models

Mice were anaesthetized with isoflurane and placed on an irradiator bed (SARRP, XStrahl Inc.). Treatment planning and radiation delivery were performed using MuriPlan software (XStrahl Inc.). CT images were acquired at 60 kV and 0.8 mA, with a voxel size of 0.275 mm, which delivers a dose of 1.2 cGy (21 (link)). Tissue segmentation was adjusted for each animal to define bone, tissue, and air. Field isocenters were applied to the segmented images to target radiotherapy delivery, and a collimator was used to customize the radiotherapy field. The SARRP delivers 225-kVp X-rays at 13-mA current (22 (link)), through a 0.15-mm Cu filter, at a dose rate of 3.1 Gy/min, and allows exact anatomic targeting with delivery of beams down to 0.5 mm. Mice received a 90° brain arc field (–45° to 45°), with a field size of 5×5 mm². Animals were treated with 5 Gy per day for 4 days. Temozolomide (100 mg/kg) was administered by oral gavage 1 hour prior to irradiation. Treatment planning and delivery simulates the clinical situation (23 (link)). Mice were euthanized by cervical dislocation when they developed symptoms.