Autologous white blood cell scan with whole-body imaging 24 hours post-administration

Q.

We performed an autologous white blood cell scan with whole-body imaging at four hours and 24 hours post-administration of the radiopharmaceutical. One of my co-workers contends this will be a single-day study, but I think it is two days. Which is correct? 

A.

Four- and 24-hour imaging would indicate two day imaging. “Day” is a calendar day, not per 24 hours. So, if you administer the radiopharmaceutical at 8:00 a.m. on Monday, imaging at 24 hours post-administration would be 8:00 a.m. on Tuesday – two days.