Development of Eqs. (A2) and (A3) for photon dose calculation to a point in a water equivalent slab phantom. Successive application of factors transforms the dose rate from the reference condition to the conditions of treatment geometry and depth. Steps in the calculation where the phantom scatter differs from the irradiating field size during the application of and ISL factors are indicated by sectioning the phantom, where the portion enclosed by the solid lines signifies the inclusion of reference field size phantom scatter. The solid circle represents the position of the calculation point, while the dashed line crossing several phantoms indicates changes in the point distance from the source.
Photon dose calculation to a point in a heterogeneous phantom. The first layer of material is assumed to be water equivalent.
BEV showing field blocking used to estimate the exposed equivalent field size for the brain field MUV in Appendix B 1. The calculation point position in the field is indicated by the circle.
Geometry for standard breast MUV calculation in Appendix B 2. (a) Placement of the calculation point within the patient in soft tissue and away from the tissue interfaces. (b) BEV for the field used to estimate the missing scatter from the tangential field. The dashed white line indicates the position of the breast horizon and the crossed circle indicates the location of the calculation point in the field.
BEV of the anterior upper mantle field calculated in Appendix B 3. The circle shows the prescription point used in the MUV calculation, which has been located in the middle of the mediastinum, well away from low-density tissue interfaces.
BEV for the modified mantle field of Appendix B 4. The calculation point centered in the mediastinum is marked by the circle.
BEV for AP lung treatment field described in Appendix B 5. The circle indicates the MUV calculation point.
Orthogonal views of MUV point within a small field lung lesion calculated in Appendices Secs. B 6 a and B 6 b. The isocenter was selected as the calculation point.
Orthogonal views of alternate MUV calculation point placed within the center of the normal density tissue within the target volume, discussed in Appendix B 6 c. The selected point is placed away from tissue interfaces as discussed in Sec. V A.
BEV for a single direct electron field calculation of Appendix B7, with the calculation point indicated by the circle.
Likelihood of potential errors in MU calculation.
Guidelines for action levels for disagreement between verification and primary calculations for homogeneous conditions.
Guidelines for action levels for disagreement between verification and primary calculations with heterogeneity corrections.
TG-71 recommended symbol notation and definitions.
Clinical examples presented in Appendix B.
Whole brain case.
Wedged breast case.
Modified mantle case.
Large field lung case.
Initial calculation point position in B6 small field lung case.
Adjusted calculation point position in B6 small field lung case.
Direct electron case.
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