LUNG AND BONE CORRECTIONS

Densities we should know:

Density of Tissue : 1 gm/cc or 1

Density of Bone : 1.8 gm/cc or 2

Density for Lung : .33 gm/cc

When planning treatments we must take into account if Lung or Bone is in the field because their densities are different thus the attenuation of the beam will be different.

• When bone is in the field the dose will be less if not taken into account
• When lung is in the field the dose will be more if it is not taken into account

Below: Example of Isodose Curve with Bone in the field on the left.   Where the Bone is the dose will be less since the Density of Bone is 2:1 over tissue.

Below : Example of a field with lung in the field on the right. Where the Lung is the dose will be more since the Density of Lung is .33 as opposed to 1 for tissue.

Below : Example of a Parallel Opposed Field where bone is in the field.   As you can see the lower Isodose Curves move where the bones is due to the dose to this area will be lower due to the higher density of bone.

Below : Example of a Parallel Opposed Field where lung is in the field.   As you can see the higher Isodose Curves move where the lung is due to the dose to this area will be higher due to the lower density of bone to the surrounding tissue.