In some cases a 2-day protocol is preferred fro practical reasons, or is right out necessery.

In very big patients (that is, top-heavy women over 250 lb., or men over 300 lb.) the 8 mCi standard dose for the first study is insufficient - resulting in unrelible low count data.

For women between 200-250 lb. and men between 250-300 lb., patient habitus should be considered and good judgement exercised..

In a two-day protocol 20-25 mCi for both the first and the second study usually results in satisfactory data. Acquisition times and processing protocols should be the same for the two studies (use the high dose parametrs from a one-day protocol). With a t 1/2 of 6 h very little of the first dose will remain in the body or the heart the next day (24 h = 4 half-life's = about 6%).