Visualization of dose distributions for photon beam radiation therapy during treatment delivery

In radiation treatment planning, dose distributions within patients' bodies are designed so that high doses can be delivered to target volumes while minimizing exposure to normal tissues. The dose distributions are delivered in accordance with those designed in the treatment plans. However, certain discrepancies inevitably exist between the designed and delivered dose distributions because of systematic and random errors during the actual treatment. Therefore, it is necessary to visualize dose distributions during treatment delivery in order to ensure the quality of the radiation therapy by comparing the actual distributions against the designed dose distributions. In this chapter, we describe the fundamental principles involved in visualizing the dose distributions for photon beam radiation therapy during treatment delivery.