Calculation of Percentage Depth Dose (PDD) by using different Ionizing Beams

For discussions, it is important to know about BED and EQD2. BED is a measure of the biological dose delivered to a tumor or organ. The theoretical dose, which if delivered in infinitely small fractions, would produce the same biological endpoints as that under consideration. It allows for the quantitative assessment of the biological effects associated with different patterns of radiation delivery. Similarly; EQD₂ is the equivalent dose in 2-Gy fractions. A fraction size of about 2 Gy was considered to be the ‘gold standard’ in external beam radiotherapy.

From Table 5; In this table we use α/β ratio for late responding tissue is 3 while for early responding tissue is 10. it is possible to compare toxicity to Gy3 values for normal tissue in different treatments and similarly evaluate the effectiveness of tumor cell kill in the different treatment strategies for Gy10 values. By comparing the overall dose of 60 Gy against the regimen for 54.9 Gy, it can be seen that in the latter there is reduced toxicity to normal tissue. By comparing the overall dose of 60 Gy against the regimen for 54.9 Gy, it can be seen that in the latter there is reduced toxicity to normal tissue. The overall dose of 54 Gy shows that the impact of radiation treatment on the tumor is also greatly reduced. Accelerated radiotherapy for head and neck cancer has been assessed in randomized studies and it has been suggested that with this technique there is an increase in the severity of acute toxicity compared with that of conventional radiotherapy.

The BED concept is often used to demonstrate the dependence of the therapeutic ratio (TR) on the number of fractions. The therapeutic ratio is defined as the ratio or margin of safety that exist between the dose of a drug that produces the desired effect and the dose that produces unwanted side effects.