Assignement: Whole Brain Module

 

Case # 1

 

Patient Name: Jane Whole Brain

Treatment Site: SAD Whole Brain

Field Size: X=25  Y=17 

Collimator Rotation 30 degrees

Calculation Point: The Isocenter

RX: 3000 cGy in 10 Fractions; 6MV
Beam arrangement: 2 Lateral Beams
IFD: 15 CM

 

The IFD (Inner Field Distance) is the thickness of the patient through the planning area.
Knowing the thickness can help us to determine the SSD in an SAD setup.

If the thickness is 15 cm, and the patient is setup midplane, then we know that ½ of the IFD is the distance from the surface of the skin to the CA. In this case, 7.5cm. Since this case is set-up SAD (@ 100cm), we can subtract the 7.5cm from the 100 and get the SSD.

 

Thus SSD = SAD – ½ IFD 

Or    SAD = SSD + ½ IFD

 

 

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