Radiation equivalent to ten chest X-rays, although dismissed by the Reuters article as inconsequential, strikes me as a high dose for a procedure to determine whether or not to take a drug.
The lungs are mostly air so the amount of radiation used to penetrate tissues for a chest xray is suprisingly small. Flying cross country is 2-5 milli rem which is about a half a chest xray (8 millirem.)
If you have a buildup of coronary artery calcium you have basically coronary artery disease. Nice to know.