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Hi List, I was recently contemplating the definition of CTDIw, and wondered why weighting factors of 2/3 periphery to 1/3 center CTDI100 were chosen. Anyone know the history here? If CTDIw is meant to estimate the average dose in the axial slice,</div>
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Hi List,</div>
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I was recently contemplating the definition of CTDIw, and wondered why weighting factors of 2/3 periphery to 1/3 center CTDI100 were chosen. Anyone know the history here?</div>
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If CTDIw is meant to estimate the average dose in the axial slice, then of course the periphery must have a higher weighting than the center due to geometric arguments (the area of the "periphery " region is larger than the "center" region) but it seems rather
arbitrary and simplistic to pick a 2:1 ratio. In a CTDI phantom of radius R, if you consider the "center" region to have radius R/2, and thus the "periphery" to be an annulus of outer-inner radius R-R/2, then the areal ratio would be 3:1 (or ¾ to ¼ periphery
to center weighting). Is it one of those things where a 2:1 ratio is "close enough" to experimental measurements and MC simulation data, and easy to remember?</div>
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Curious to hear what people know!</div>
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-P</div>
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<span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Peter Watson, PhD, MCCPM</span></p>
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(masculine pronouns)</div>
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<span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Medical Physicist, McGill University Health Centre</span></p>
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<span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Assistant Professor, Medical Physics Unit and Department of Oncology, McGill University</span></p>
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