15.071 | Spring 2017 | Graduate

# The Analytics Edge

8.3 Radiation Therapy: An Application of Linear Optimization

## 8.3 Radiation Therapy: An Application of Linear Optimization

### Quick Question

In your spreadsheet from Video 3, make sure that you have solved the original small example problem (change the spinal cord limit back to 5 and re-solve if you have changed it, and make sure the objective value is 22.75).

Now, change the weight for the spinal cord term in the objective to 5.

Without re-solving, what does the objective value of the current solution change to?

Exercise 1

Numerical Response

Explanation

The term SUMPRODUCT(B14:B19;F5:F10) in the objective (corresponding to Voxel 5) should now be 5*SUMPRODUCT(B14:B19;F5:F10). This changes the objective value to 42.75.

Now re-solve the model. What does the objective change to?

Exercise 2

Numerical Response

Explanation

You can resolve the model by going to Solver, and just hitting Solve. The new optimal objective function value is 25.666667.

Notice how we are now giving a smaller dose to the spinal cord!