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 anything 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 6.0 kg of tissue. how many chest x rays would deliver the same total amount of energy to the body of a 85 kg person as one whole-body scan?