Abstract # 2072 Craniospinal Irradiation in the Supine Position - Application of an Image-Guided Radiotherapeutic Technique to Plan, Verify and Treat

Presenter: Lau, Michelle

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Virtual computer tomography [CT] simulation was performed on 8 paediatric and 8 adult patients lying supine on a custom-designed board compatible with both the CT and Varian ExactTM couch. A secured thermoplastic head-and-shoulder mask ensured accurate and reproducible patient positioning. Three-dimensional CT-based plans were developed with the collimator of lateral opposed cranial fields rotated to match the beam divergence of the posterior spine field. The fields junction along a common line running through the mid-sagittal plane. Verification of field junction was determined using a 2.0mm radio-opaque marker at the border of the treatment fields. For each treatment, this marker was placed on the anterior surface of patientís mask at the intersection of inferior borders of cranial fields. Pre-treatment electronic portal images [EPI] of the lateral cranial and posterior spinal field borders were assessed online for field junction verification. Displacements greater than 2.0mm were corrected prior to treatment delivery.

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