because of unexpected administrative barrier, it was very difficult to enroll case.

The clinically widely used X-ray computed tomography examination has a low-grade radiation effect and recently has attracted much attention concerning the possible adverse effects of radiation on human body [ref. 1-5]. The radiation is harmful to human tissues and cells mainly because it can interact with water (which makes up to 80% of cells) to generate reactive oxygen species (ROS), especially the formation of hydroxyl radicals. So far as we can reach, there is no report concerning the relation between X-ray computed tomography examination and the blood ROS level. Therefore, we wish to conduct this study to clarify if the cardiac computed tomography angiography (cardiac CTA) may induce a higher level of ROS in the peripheral blood.

Study subjects will be OPD patients who are arranged for cardiac CTA examination because of suspect coronary artery disease (CAD). In total, twenty cases will be enrolled for the study. The formal consent will be delivered and explained to the patients and families after the arrangement of cardiac CTA. It then will be retrieved just before the performance of cardiac CTA.

For each enrolled case, peripheral blood will be sampled three times (once before and twice after the performance of cardiac CTA). Totally 60 blood samples will be collected from 20 study subjects within 3 months (January 1 ~ March 31, 2009). ROS level in the collected blood samples will be then measured, compared, and analyzed.

Inclusion Criteria:

• subjects who are arranged for cardiac CTA examination because of suspect coronary artery disease.

Exclusion Criteria:

• none

Study subjects will be OPD patients who are arranged for cardiac CTA examination because of suspect coronary artery disease.