Screening for Atherosclerosis with Magnetic Resonance Imaging and Ultrasound

Sammanfattning: Atherosclerosis is a major cause of death and disability worldwide. Although traditional risk factors can identify the healthy or severely affected individuals, sudden lethal outcome is still frequent in those suggested as intermediate in risk for cardiovascular events (CVE). Adding imaging to the traditional scoring systems might improve risk stratification.This thesis investigates whether the addition of magnetic resonance imaging (MRI) and ultrasound (US) to traditional risk factors might render atherosclerosis suitable for mass screening, selective screening or screening in research settings.In paper I the carotid arteries were assessed in six different manners (carotid intima media thickness (CIMT) in two different locations, presence of plaque, number of plaques, plaque size and plaque composition) using US. More than 800 Caucasian subjects were assessed at ages 70 and 75, and outcome examined at 80 years of age. Plaques with an area exceeding 10mm2 in the bulb were found to be most closely related to CVE.Paper II established that carotid plaque volume measured with MRI did not correlate with carotid plaque area assessed with US. MRI reached the highest levels of reproducibility of the two methods.Paper III used the previously created total atherosclerotic score (TAS), a scoring system based on whole body magnetic resonance angiography (WBMRA) that assesses global atherosclerosis. TAS was found to predict CVE in 305 PIVUS-subjects at age 70 years during 5 years of follow-up. The risk for CVE was found to be eightfold with TAS>0.In paper IV CIMT was assessed with US at ages 70 and 75 years. CIMT at baseline, but not the change in CIMT over five years, was significantly related to TAS, thus suggesting carotid changes to correlate with atherosclerosis throughout the body.In conclusion, in research settings WBMRA and MRI, as well as US, can be used for screening and following up of atherosclerotic changes, as their predictive values and reproducibility are good. US might be feasible in selective screening but none of these methods are as of now suitable for mass screening.