**8. Pediatrics**

Pediatrics is a special subgroup of patients requiring considerable care and attention to detail. This population requires many departments within the hospital setting including anesthesia and social services to manage and optimize patient care. Often the targets treated in children are both similar and dissimilar to adult counterparts. CNS tumors often require similar normal tissue avoidance strategies with careful attention to the volume of temporal lobe treated including essential structures including but not limited to the chiasm, cochlea, retina, and brain stem. Diseases including germ cell tumors and medulloblastoma require therapy to the CNS fluid pathways, therefore strategy of care is different than adults and includes the craniospinal axis. Intensity modulation and protons have been used to limit exit dose to cardiac, pulmonary, liver, bowel, vertebral body, and renal volumes. Pediatric diseases often requiring whole lung therapy and strategies are now more routine to provide conformal avoidance of the heart using four-dimensional technology and volume modulated arc therapy. Neuroblastoma, sarcoma and other soft/bone tissue primary lesions often require advanced technology therapy application with a growing interest in theranostics for neuroblastoma care. In NCTN clinical trials, more than 25% of pediatric patients are now treated with protons when they receive radiation therapy, and this number is expected to increase moving forward. **Figure 8** is a 7-year-old patient

requiring whole lung therapy being treated with cardiac avoidance. Note the ability to limit dose to the cardiac structures using volume modulated arc therapy [93, 99–106].

### **9. Imaging in radiation oncology**

With the advent of volumetric radiation therapy planning systems, imaging has become essential for modern therapy including dosimetry. Prior to the development of computer tomography-based simulation, patients were treated with two-dimensional planning with fluoroscopy simulators. Computer tomography simulation was a paradigm shift in radiation oncology. Today imaging is the infrastructure to all elements of activity in the department. Thoracic and upper abdominal patients are simulated with four-dimensional imaging. Many head and neck and nearly all CNS patients are planned with fusion imaging to accurately define target volumes of interest. Many CNS patients are now planned with multiple MR sequences which when applied are used for dose painting on clinical protocols using FLAIR, spectroscopy, and contrast as areas to target. Cone beam computer tomography has been incorporated into linear accelerators for daily target validation and can be applied for adaptive radiation therapy planning. Portal imagers have a dual role as a dosimeter. Single photon emission computed tomography (SPECT) imaging will play an essential role in computational analytics for theranostics at multiple time points to evaluate dose to volume and migration. Today, all patients are treated with image guidance to ensure stability and reproducibility in daily positioning. Optical tracking tools are used to ensure three-dimensional stability of patient set up during treatment and imaging is used to validate outcome. These changes in daily work and workflow have largely occurred during the past two decades, therefore physics staff and dosimetrists have become nimble in image acquisition and fusion. Modern planners have become expert in radiographic anatomy and often are responsible for contouring normal tissues including subtle structures such as the optic chiasm and the cochlea. These skills are far different than the skill set required two decades ago, and this evolving expertise is an important aspect to modern planning teams [1–11].
