I posted a similar question earlier but the answer wasn\'t accepted. How is the

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I posted a similar question earlier but the answer wasn't accepted. How is the answer 23.3? When I try working it out I get 2228.8, and all the other posts I can find on here for related questions seem to give answers in that range. I don't think the system is broken because the same thing happens for other practice questions of this type. Anyone know what is going on or can show me how the answer 23.3 came about?

A dose of 15 Gy is to be delivered with a 6 MeV beam to a tumour located at a depth of 11 cm. An 11 x 11 cm field is to be used with a 100 cm SSD. For this beam in this geometry, you are given the following additional data: PDD for a 10 × 10 cm field at depth of 10 cm = 67.3%, PDD for a 12 × 12 cm field at depth of 10 cm-68.7%, PDD for a 10 × 10 cm field at depth of 15 cm 52.2%, and PDD for a 12 x 12 crn field at depth of 15 cm-536%, Compute the maximum toe in Gy) received at any location within the patient's anatomy. (For all field sizes and depths stated above, the dose at depth d, D(d), is linear with respect to field size and linear with respect to depth.) 23.3 Gy

Explanation / Answer

1 Gy= 1joule/ kilogram.

Convert 1MeV into joule. 1eV= 1.6x 10 to the power minus nineteen. And one mega is equal to 10 to the power 6. So 6MeV is equal to 6x 1.6x 10 to the power minus 13.

Use this in the calculation to get answer 23.3

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