背景 主動脈弓縮窄的發生率佔所有先天性心臟疾病的百分之八至十。以往，主動脈弓縮窄的確定診斷端賴心臟血管攝影術。然而，此技術使用幅射線且有可能引起血管傷害之危險，特別是在對嬰幼兒的使用上。此研究之目的乃在探討核磁共振影像(MRI)是否可作為評估主動脈弓縮窄術前術後嚴重程度的有用且非侵犯性工具。方法 總計有10名病童(四位男童和六位女童)，其年齡分布為17天至七歲(平均為1.1歲)。其中有六位病童為先天性主動脈弓縮窄及四位病童為術後復發縮窄，分別進行MRI和心臟血管攝影檢查。分別以MRI及心臟血管攝影術測量及比較在左頸動脈分支之主動脈弓(AA)，主動脈最狹窄處(CoA)及橫膈膜處之下降主動脈(DA)之直徑。利用統計得出MRI及心臟血管攝影結果間之平均差。另以線性相關係數比較以MRI及心臟血管攝影所測得之直徑，且以CoA/DA×100% 計算分別以MRI及心臟血管攝影所測得之相對主動脈弓縮窄。結果 以MRI測得之AA，CoA及DA的平均直徑為6.3±1.88公釐，3.8±2.0公釐，及7.2±1.4公釐，利用心臟血管攝影所測得之數值則為6.6±2.7公釐，4.0±2.1公釐7.2±1.8公釐。此二種方法所測得之平均差在AA為1.48公釐(SD=1.32公釐)，CoA為0.72公釐(SD =0.78公釐)，DA則為0.90公釐(SD=0.83公釐)。以MRI及心臟血管攝影所測得之主動脈各位置之直徑其線性相關係數(r值)在AA為0.662，CoA為0.868和DA為0.706。相對主動脈弓縮窄超過60%者被認為會引發有意義之壓力差且應以手術治療之。依此標準，發現以MRI及心臟血管攝影所測得之相對主動脈弓縮窄是一致的。結論 以MRI及心臟血管攝影所測得之直徑顯示有可接受的平均差及好的線性相關係數。此外，MRI就狹窄之嚴重度的評估提供了一可信賴的而與心臟血管攝影一致的結果。是故，可認定MRI適於評估主動脈弓縮窄術前術後狹窄之位置、大小及嚴重度。

　　　　　Background: Coarctatoin of the aorta (CoA) is encountered in 8% to 10% of all patients with congenital heart defects. In the past, the confirmed diagnosis of CoA relied on angiography, however, this technique uses hazardous radiation, and carries a risk of causing vascular damage at the puncture site, particularly in infants. This study aimed to discover whether magnetic resonance imaging (MRI) was a useful-non-invasive tool to estimate the severity of CoA before or after repair.Methods: Ten children (4 boys and 6 girls), aged from 17 days to 7years (mean, 1.1 years), 6 who had native CoA and 4 who had re-stenosis after repair, underwent MRI and angiography. The diameters of the aortic arch at the left carotid artery branching (AA), as well as the diameters at the narrowest site on the aorta and descending aorta in the diaphragmatic area (DA), were measured and compared using the above-mentioned 2 methods. Linear correlation coefficients were applied to compare the correlation between MRI and angiography. The relative narrowing of CoA was calculated by using CoA/DA × 100% between MRI and angiographic measurement. Narrowing of more than 60% was thought to induce a significant pressure gradient that called for surgical intervention.Results: The mean diameters of AA, CoA and DA were, respectively, 6.3±1.8 mm, 3.8±2.0 mm and 7.2±1.4 mm by MRI measurement, and 6.6±2.7 mm, 4.0±2.1 mm and 7.2±1.8 mm by angiography. The mean differences of measured diameters by the 2 methods were AA 1.48 mm (SD=1.32 mm), CoA 0.72 mm (SD=0.78 mm) and DA 0.90 mm (SD=0.83mm). The linear correlation coefficient (r value) for the diameter of different locations along the aorta as measured by MRI and angiography was 0.662 at AA, 0.868 at CoA and 0.706 at DA. Using this criteria, there was a consistent, relative narrowing calculated by both MRI and angiography.Conclusion: The mean difference, when taken together with a good linear correlation coefficient of the diameters as measured by MRI and angiography, make this technique acceptable. In addition, MRI proved to be a reliable predictor of the probable severity of coarctation. As a result, we may conclude that MRI is suitable for evaluating the location, size and severity of the coarctation before and after treatment.