All female subjects who are randomized to the MSCT arm will be required to wear a radioprotective bismuth shield during the actual MSCT scan. This radioprotective brassiere (Cone Instruments Inc, Solen, Ohio) composed of neoprene and bismuth trioxide has been studied in 16 slice CT scans and has been shown to reduce breast radiation exposure by approximately 40%.25 The bra will be placed directly over both breasts of the female subjects by either a female nurse or technician in the Radiology Department. The adhesive strips on the undersurface of these radioprotective bras will prevent any slippage during the actual scan. Depending on the bust size of the subject, either a medium or large bra will be employed for best fit. Each bra is intended for single patient use only and will be discarded after each study. The effect of these bismuth shields on image interpretation is unknown. If images of the coronary arteries are deemed to be unevaluable, women 40 years and younger will be excluded from participation in the study. In this event, only women greater than the age of 40 years will be enrolled and radioprotective shields will not be used.