Medical Imaging Systems · Nuclear Imaging · 2 marks · Numerical answer
For the source’s ideal inverse-square radiation model, a person one metre from a 4000-curie source receives a specified lethal dose in five minutes. At three metres, how many minutes give the same dose? Give an integer.
Dose rate from the ideal point source scales as 1/r². At three times the distance, rate is one ninth, so equal accumulated dose takes nine times as long. Thus 5×9=45 minutes. This is the mathematical exam model with unchanged source and no shielding.
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