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B Pickett

Publications and source records attributed to B Pickett.

3 recordsLinked to original sources
PubMed1992

Normalization: what does it really mean?

Attempts have been made to standardize normalization techniques, but it remains a confusing issue. As of late there are five different possible normalization tools consisting of normalizing: 1. to the isocenter, 2. to a specific point other than the isocenter, 3. to a minimum target absorbed dose whose are of maximum target absorbed dose is a 2 cm2 area, 4. to an isodose value, 5. to the dmax of the beams. The International Commission on Radiation Units and Measurements has updated its report number 29 to further recommend normalization standards to include planning to a specification point that: 1. is easy to define in an unambiguous way, 2. is chosen in a region where the dose is rather homogeneous and representative of the dose distribution throughout the target volume, 3. defined where the dose can be accurately determined, 4. normalizes to the isocenter of the plan where the maximum absorbed dose is a 1.5 cm2 area, 5. limits the dose variation to 10%. With increasing complexity involving three-dimensional planning, mixed-beam therapy, and heterogeneity compensation, a full understanding of dose determination is necessary to accurately implement treatment plans.

Humans↗
PubMed1989

An approach to abutting adjacent fields.

Problems arise in designing treatment techniques involving two pair of adjacent opposing fields where machine limitations require the patient to flip from supine to prone positions. Mantle and para-aortic treatments, in particular, can create challenging problems because of changes in patient position, different SSD's between adjacent fields, internal anatomical changes from supine to prone position, as well as field size and other treatment machine limitations. A simulator technique has been developed which takes cognizance of these limitations in specifying the gap between adjacent fields. It employs collinearity of the 50% decrement lines of adjacent-opposed field edges and the intersection of all four edges at an internal mid-plane match point. The technique maintains dose homogeneity and eliminates hot and cold triangles in the area of abutment. Simulation radiographs facilitate identification of collinearity with respect to a specific vertebra in the plane of abutment. In summary, this approach: Verifies abutment of coplanar fields by use of match film, improves isodose uniformity at mid-plane, evaluates dose distributions when abutment occurs at a point anterior or posterior to midline, prevents the possibility of spinal cord complications that might occur due to three field overlap.

Humans↗