對於冠狀動脈心臟病的病患而言，支架置放是最普遍的治療方式。在藥物支架的年代，適當的支架尺寸能避免支架內狹窄的發生。本研究的目的是在於比較冠狀動脈定量分析量測的血管直徑與血管內超音波量測的血管內徑的差異，並找出兩著之間的修正因數。本研究收案在2004年11月到2010年3月，根據排除條款，共有三十位病患（25位男性，5位女性，平均年齡68±8歲）經過冠狀動脈攝影與血管內超音波的檢查，冠狀動脈攝影是經由股動脈或是橈動脈進行，使用6－8號的血管鞘與同尺寸的導管進行檢查。冠狀動脈攝影評估左前降枝至少由兩個角度，也至少有兩個富有血管攝影經驗的醫師進行評估。在冠狀動脈攝影後，再以導引導絲帶血管內超音波導管進入待測血管病量側血管大小。冠狀動脈定量分析量測左前降枝近端平均參考尺寸為3.21毫米；血管內超音波量測左前降枝近端平均參考尺寸為3.40毫米。冠狀動脈定量分析量測左前降枝中段平均參考尺寸為3.00毫米；血管內超音波量測左前降枝中段平均參考尺寸為3.28毫米。我們使用線性迴歸的方法，找出兩著差的方程式。這結果確實呈現冠狀動脈定量分析明顯低估血管真實大小，依賴此結果會增加支架內再發狹窄的風險；而血管內超音波測量的結果是準確且值得信賴的。

Stent implantation is a common treatment for patients with coronary artery disease (CAD). In the drug-eluting stent (DES) era, the optimal stent size would avoid intra-stent restenosis. The purpose of this study was to compare the coronary artery diameter calculated by quantitative coronary angiography and intravascular ultrasound (IVUS) then find out the correction parameter. Based on the exclusion criterion, a total of 30 patients (25 males, 5 females; mean age, 68 ± 8 years) who underwent coronary angiography and IVUS examination were enrolled from November 2004 to March 2010. Coronary angiography was performed via the femoral artery approach or radial artery approach, with insertion of a 6 to 8 Fr. Sheath followed by angiography catheter or guiding catheter of the same size. Angiographic assessments of the left anterior descending (LAD) was made from at least 2 views. Two experienced angiographers reviewed the angiogram. After angiography, a 0.014-inch guide wire was passed through a 6 Fr to 8 Fr. IVUS examinations were conducted to determine the most appropriate vessel diameter. The mean reference diameter of LAD proximal segment by QCA was 3.21 mm and IVUS was 3.40 mm. The mean reference diameter of LAD middle segment by QCA was 3.00 mm and IVUS was 3.28 mm. We used the linear regression analysis to find the formula that is between QCA and IVUS. These results demonstrate that assessing vessel diameter by QCA significantly underestimate the true luminal diameter. The assessing vessel diameter by QCA will cause stent apposition increase the risk of intra-stent restenosis. The assessing vessel diameter by IVUS is more accurate than QCA.