**3.2 Calculation of the number of fractions**

It is necessary to find the number of fractions during irradiation of the mammary gland at 2.67 Gy, so that this regimen is isoeffective to the classical one at 2 Gy per fraction up to 50 Gy daily, without taking into account proliferation. For the mammary gland alpha beta is 4.6 Gy; alpha beta of early skin reactions is 8.8 Gy; for late complications is 1.7 Gy.

The data of a dose per fraction, the passed fractions, and the alpha beta coefficient are entered. Next, by the selection method, the number of fractions, at which the value of the equivalent dose will be closest to 50 Grays, is substituted. In the first case, these are 17 fractions (**Figure 3**).

Then, the alpha beta for early skin reactions is changed, and the value of 18 fractions by the selection method is received (**Figure 4**).

**Figure 2.** *Calculation of isoefficient doses.*

## *Radiation Therapy*


#### **Figure 3.**

*Calculation of the number of fractions. Alpha beta 4.6 Gy.*


#### **Figure 4.**

*Calculation of the number of fractions. Alpha beta 8.8 Gy.*


#### **Figure 5.**

*Calculation of the number of fractions. Alpha beta 1.7 Gy.*

For an alpha beta coefficient of 1.7 Gy, the number of fractions is 16 (**Figure 5**).

#### **3.3 Calculation of corrections for the modified treatment regimen**

The patient has prescribed five sessions of preoperative radiation therapy dose per fraction of 5 Gy. On Monday and Tuesday, everything went as had been planned. On Wednesday, there was a break in the treatment. What dose should be given for the last two fractions to complete RT as planned on Friday? α/β = 10 Gr.

The data from the condition of the problem are entered. Simulate a situation in which the third fraction is skipped is simulated, and the result of 6.73 Gy per fraction is obtained (**Figure 6**).

*Linear Quadratic Model in the Clinical Practice via the Web-Application DOI: http://dx.doi.org/10.5772/intechopen.109621*


#### **Figure 6.**

*Calculation of corrections for a modified treatment regimen.*
