• To scan or not to scan? It has become popular for some people to have yearly whole-body scans (CT scans, formerly called CAT scans), using x rays, just to see if they detect any- thing suspicious. A number of medical people have recently questioned the advisability of such scans, due in part to the radiation they impart. Typically, one such scan gives a dose of 12 mSv, applied to the whole body. By contrast, a chest x ray typically administers 0.20 mSv to only 5.0 kg of tissue. How many chest x rays would deliver the same total amount of energy to the body of a 75 kg person as one whole-body scan?

• To scan or not to scan? It has become popular for some people to have yearly whole-body scans (CT scans, formerly called CAT scans), using x rays, just to see if they detect any- thing suspicious. A number of medical people have recently questioned the advisability of such scans, due in part to the radiation they impart. Typically, one such scan gives a dose of 12 mSv, applied to the whole body. By contrast, a chest x ray typically administers 0.20 mSv to only 5.0 kg of tissue. How many chest x rays would deliver the same total amount of energy to the body of a 75 kg person as one whole-body scan?