Windsong,

Â Here's an example.Â If an AN was measured to be 1.5 cm x 1.0 cm x 0.8 cm, we can divide each "diameter" by 2 to convert them to radius measurements, giving 0.75 cm, 0.5 cm, and 0.4 cm.Â We can plug these radii into the formula listed in the earlier note, using 3.1416 for the value of pi.

4/3 x 3.1416 x 0.75 cm x 0.5 cm x 0.4 cm = 0.62832 cubic cm.

Â It should be noted that there is some error involved in measuring dimensions on MRIs, and trying to represent a complex shape as an ellipsoid.Â I am not knowledable about radiation therapy, but the error involved is probably not significant in calculating radiation dosages.

Regards,

Rob

PS: measuring ellipsoid dimensions is an interesting exercise, and involves tensor mathematics with eigen vectors, etc.Â Tensor mathematics is used by scientists to descibe physical properties in the natural world, for example how a rock allows fluids to flow through it at different rates in differenet directions.