Nuclear Medicine: Scaling Images


In a certain imaging study the screen is set to a scale of 1:3 (i.e. 1 cm viewed on the screen is equivalent to 3 cm in the person’s body.) If a screen view of the liver displays a lesion area of 1.6 cm2, how large is the lesion area in the person’s liver?


You might say the solution is an easy ratio and proportion or is it? The answer is not as simple as 3 x 1.6.

The trick is to recognize that when area is involved both dimensions (length and width) are changing. If you visualize a square 1 unit by 1 unit that expands to a square 3 units by 3 units, the area of the square increases by a factor of 9.


The correct solution in this case is :

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Written by Louise Routledge, September 1, 1998