Patent ID: 7587023

Claim:
A radiation dose modulation apparatus controlling a radiation dose in a coronary CT angiography that utilizes an X-ray CT system including a multi-row detector, the apparatus comprising: a tube current modulation table storage unit which classifies standard deviation values of CT numbers calculated from at least one pre-contrast CT image into a series of levels, stores at least one tube current modulation table in which the levels are associated with corresponding tube current modulation values, for each of a plurality of desired noise level standard deviations; and a processing unit configured to calculate a standard deviation of the CT numbers from the at least one pre-contrast CT image, to determine the tube current value corresponding to the calculated standard deviation for a desired noise level standard deviation, from the at least one tube current modulation table, and to control a scan operation for obtaining a post-contrast CT angiography in accordance with the determined tube current value.