陳 鈺，朱元利，薛華丹，王 沄，李玉梅，張竹花，金征宇

中國(guó)醫(yī)學(xué)科學(xué)院 北京協(xié)和醫(yī)學(xué)院 北京協(xié)和醫(yī)院放射科，北京 100730

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第3代雙源CT 70 kV管電壓和20～25 ml對(duì)比劑模式下行頭頸聯(lián)合CT血管成像在體質(zhì)量小于75 kg人群中的效果

陳 鈺，朱元利，薛華丹，王 沄，李玉梅，張竹花，金征宇

中國(guó)醫(yī)學(xué)科學(xué)院 北京協(xié)和醫(yī)學(xué)院 北京協(xié)和醫(yī)院放射科，北京 100730

目的觀察第3代雙源CT 70 kV管電壓和20～25 ml對(duì)比劑模式下行頭頸聯(lián)合CT血管成像的效果，評(píng)估注射同側(cè)對(duì)比劑滯留產(chǎn)生的靜脈偽影對(duì)圖像質(zhì)量的影響。方法采用隨機(jī)表格法將懷疑或已有頭頸部動(dòng)脈血管疾病、體質(zhì)量小于75 kg行頭頸第3代雙源CT血管成像掃描的40例患者隨機(jī)分為70 kV組和100 kV組，每組20例，70 kV組采用20～25 ml對(duì)比劑和高級(jí)模擬迭代重建技術(shù)；100 kV組采用40 ml對(duì)比劑和濾波反投影技術(shù)。采用3分法對(duì)對(duì)比劑滯留產(chǎn)生的靜脈偽影及對(duì)比劑滯留范圍進(jìn)行主觀評(píng)分。結(jié)果70 kV組有效劑量較100 kV組下降約58%(t=-18.14，P<0.001)。70 kV 組20例患者中，16例(80.0%)存在靜脈偽影，其中6例(37.5%，6/16)的靜脈偽影影響鄰近動(dòng)脈的評(píng)價(jià)；100 kV組20例患者中，19例(95.0%)存在靜脈偽影，其中7例(36.8%，7/19)的靜脈偽影影響鄰近動(dòng)脈的評(píng)價(jià)；兩組間差異無(wú)統(tǒng)計(jì)學(xué)意義(Z=-0.878，P=0.380)。70 kV組20例患者中，13例(65.0%)對(duì)比劑滯留較明顯，其中2例(15.3%，2/13)對(duì)比劑滯留延續(xù)至上腔靜脈；100 kV組20例患者中，19例(95.0%)對(duì)比劑滯留較明顯，其中13例(68.4%，13/19)對(duì)比劑滯留延續(xù)至上腔靜脈；兩組間差異有統(tǒng)計(jì)學(xué)意義(Z=-3.654，P<0.001)。結(jié)論第3代雙源CT 70 kV管電壓和20～25 ml對(duì)比劑模式下行頭頸聯(lián)合CT血管成像，較100 kV掃描輻射劑量明顯下降，對(duì)比劑滯留范圍明顯減低，靜脈偽影與100 kV組相近。

第3代雙源CT；頭頸部動(dòng)脈；CT血管成像；對(duì)比劑；管電壓

ActaAcadMedSin，2017,39(1)：4-11

在進(jìn)行頭頸部血管成像(CT angiography，CTA)過程中，對(duì)比劑注射后滯留在頸部靜脈中形成的顯著的高密度影，可能產(chǎn)生X線的硬化線束偽影，將影響診斷的準(zhǔn)確性，例如鄰近動(dòng)脈血管是否有血栓或夾層[1]。此外，高密度也可能影響重建圖像的質(zhì)量。減少對(duì)比劑用量是減少靜脈強(qiáng)化程度及靜脈對(duì)比劑滯留最直接有效的方法。減少對(duì)比劑的滯留也會(huì)減少靜脈偽影的產(chǎn)生。多項(xiàng)研究表明，對(duì)比劑用量減少，對(duì)比劑注射同側(cè)的靜脈偽影也相應(yīng)減少[2-3]。Hinkmann等[3]研究顯示，行頭頸CTA檢查時(shí)，30 ml組患者的靜脈強(qiáng)化程度明顯低于80 ml組，出現(xiàn)線束偽影的比例也少于80 ml組。Xia等[4]采用64排CT，結(jié)果顯示80 kV采用較低對(duì)比劑用量(175 mgI/kg體重)，其靜脈線束偽影評(píng)分優(yōu)于120 kV組及較多對(duì)比劑用量(350 mgI/kg)。雖然對(duì)比劑用量可以減少靜脈偽影，但是管電壓的降低又增加了靜脈偽影。這是因?yàn)楣茈妷狠^低時(shí)，X線的穿透能力下降，密度較高的物質(zhì)引起硬化線束產(chǎn)生的線束偽影也更加明顯，這在金屬物質(zhì)及骨骼方面表面得較為明顯。迭代重建可以減少這種效應(yīng)[5- 7]。伴隨超高速、寬探測(cè)器以及迭代重建算法的使用，70 kV已經(jīng)廣泛應(yīng)用于臨床[8- 11]。由于第3代雙源CT具有更強(qiáng)大的管電流輸出能力[12]，結(jié)合高級(jí)模擬迭代重建(advanced modeled iterative reconstruction，ADMIRE)技術(shù)[13]，使得在70 kV的條件下，對(duì)比劑用量有了進(jìn)一步下降的可能性。本研究觀察了第3代雙源CT 70 kV管電壓和20～25 ml對(duì)比劑模式下行頭頸聯(lián)合CTA的效果，評(píng)估了注射同側(cè)對(duì)比劑滯留產(chǎn)生的靜脈偽影對(duì)圖像質(zhì)量的影響。

對(duì)象和方法

對(duì)象及分組2015年10月至2016年3月在北京協(xié)和醫(yī)院放射科行頭頸CTA掃描的患者40例，采用隨機(jī)表格法隨機(jī)分為70 kV組和100 kV組，每組20例。入選標(biāo)準(zhǔn)：(1)懷疑或已有頭頸部動(dòng)脈血管疾??；(2)體質(zhì)量<75 kg。排除標(biāo)準(zhǔn)：(1)對(duì)含碘對(duì)比劑過敏；(2)嚴(yán)重肝腎功能不全；(3)嚴(yán)重失代償性心功能不全；(4)懷孕或哺乳期婦女；(5)煙霧??；(6)動(dòng)靜脈瘺；(7)顱內(nèi)有金屬植入物(鈦夾或彈簧圈)。本研究經(jīng)北京協(xié)和醫(yī)院倫理委員會(huì)批準(zhǔn)，所有患者均簽署知情同意書。

頭頸部CTA檢查及圖像后處理采用192層第3代雙源CT(SOMATOM Definition Force；Siemens Healthcare，F(xiàn)orchheim，Germany)，患者仰臥在檢查床上，在患者肘前靜脈置入18 G套管針。經(jīng)雙筒高壓注射器注入對(duì)比劑優(yōu)維顯(碘普羅胺，含碘370 mgI/ml，德國(guó)拜耳醫(yī)藥保健有限公司)及生理鹽水。

70 kV組掃描及對(duì)比劑注射方案：參考Lell等[14]研究，根據(jù)患者公斤體質(zhì)量設(shè)計(jì)不同掃描參數(shù)。體質(zhì)量<65 kg患者，以4 ml/s速率注射20 ml對(duì)比劑，管電壓70 kV，參考管電流500 mA；65 kg≤體質(zhì)量<75 kg的患者，以5 ml/s速率注射25 ml對(duì)比劑，管電壓70 kV，參考管電流700 mA。以與對(duì)比劑相同的速率注射40～ 50 ml生理鹽水。其余參數(shù)：采用自動(dòng)管電流調(diào)節(jié)技術(shù)，準(zhǔn)直192×0.6 mm，轉(zhuǎn)速0.25 s，螺距(pitch)1.5。采用團(tuán)注追蹤技術(shù)觸發(fā)，感興趣區(qū)(region of interest，ROI)設(shè)置在升主動(dòng)脈，監(jiān)測(cè)CT值達(dá)到80 HU后，延遲2 s開始掃描，掃描方向頭至足。70 kV圖像采用ADMIRE，卷積核(kernal)為“Bv36”，迭代強(qiáng)度采用經(jīng)驗(yàn)值3。所有圖像采用0.6 mm層厚以及0.4 mm 間隔進(jìn)行重建軸位圖像。

100 kV組掃描及對(duì)比劑注射方案：以5 ml/s速率注射40 ml對(duì)比劑以及50 ml生理鹽水。根據(jù)系統(tǒng)自行設(shè)定的掃描方案，采用半自動(dòng)管電流調(diào)節(jié)，管電壓設(shè)置為100 kV，參考值設(shè)為120 kV/84 mA。掃描方向足至頭。100 kV圖像采用濾波反投影進(jìn)行重建，kernal為“Bv36”，重建層厚0.6 mm,重建間隔0.4 mm。

將圖像編號(hào),去除患者姓名及掃描參數(shù)標(biāo)記后傳至后處理工作站(syngo. Via VA30，Siemens Healthcare)。

圖像質(zhì)量評(píng)價(jià)記錄患者的性別、年齡、身高和體質(zhì)量，計(jì)算體質(zhì)量指數(shù)(body mass index，BMI)。記錄掃描時(shí)間、視野(field of view，F(xiàn)OV)、X線管的實(shí)際管電流和輻射劑量。輻射劑量指標(biāo)包括CT容積劑量指數(shù)(CT dose index volume，CTDIvol)和劑量長(zhǎng)度乘積(dose-length product，DLP)。計(jì)算有效劑量(effective dose，ED)，ED=DLP×0.0048 mSv[15]。

重建不同角度的最大密度投影及多平面重組圖像。由2名具有頭頸部影像診斷經(jīng)驗(yàn)的醫(yī)師共同閱片，從以下兩方面評(píng)價(jià)對(duì)比劑注射同側(cè)靜脈偽影及對(duì)比劑滯留的情況，并獲得一致性評(píng)分。

靜脈偽影評(píng)分：主要指鎖骨下或腋下靜脈內(nèi)對(duì)比劑產(chǎn)生的偽影對(duì)鄰近鎖骨下動(dòng)脈或腋下動(dòng)脈的影響，采用3分法評(píng)分[3]：1分：優(yōu)秀，無(wú)靜脈偽影；2分：好，有靜脈偽影，但不影響鄰近動(dòng)脈評(píng)估；3分：差，靜脈偽影影響鄰近動(dòng)脈評(píng)估(圖1)。

對(duì)比劑滯留評(píng)分：對(duì)比劑在鎖骨下靜脈、頭臂靜脈及上腔靜脈內(nèi)的滯留情況采用3分法評(píng)分[16]：1分：優(yōu)秀，頭臂靜脈及上腔靜脈內(nèi)沒有對(duì)比劑滯留，鎖骨下靜脈僅有少量滯留；2分：好，上腔靜脈內(nèi)沒有對(duì)比劑滯留，頭臂靜脈及鎖骨下靜脈可見滯留；3分：差，上腔靜脈、頭臂靜脈以及鎖骨下靜脈內(nèi)均見對(duì)比劑滯留(圖2)。

統(tǒng)計(jì)學(xué)處理采用SPSS 17.0統(tǒng)計(jì)軟件，2組患者的年齡、身高、體質(zhì)量、BMI、掃描時(shí)間、FOV、實(shí)際管電流、輻射劑量等符合正態(tài)分布的計(jì)量資料以均數(shù)±標(biāo)準(zhǔn)差表示，組間差異比較采用獨(dú)立樣本t檢驗(yàn)；2組患者的性別比較采用χ2檢驗(yàn)；對(duì)2種掃描方案的靜脈偽影、對(duì)比劑滯留評(píng)分比較采用Wilcoxon非參數(shù)檢驗(yàn)；P<0.05為差異有統(tǒng)計(jì)學(xué)意義。對(duì)同一研究方案組，采用kappa(κ)值檢驗(yàn)靜脈偽影及對(duì)比劑滯留評(píng)分的一致性：κ=0～0.2，差；κ=0.21～0.40，一般；κ=0.41～0.60，中等；κ=0.61～0.80，好；κ=0.81～1.00，非常好。

結(jié) 果

一般情況的比較70 kV組和100 kV組患者在性別、年齡、身高、體質(zhì)量和BMI方面差異均無(wú)統(tǒng)計(jì)學(xué)意義(P均>0.05)(表1)。

掃描參數(shù)及輻射劑量比較70 kV組的掃描時(shí)間(t=-35.43，P<0.001)、CTDIvol(t=-23.43，P<0.001)和DLP(t=-18.14，P<0.001)均明顯低于100 kV組，ED較100 kV組下降約58%(t=-18.14，P<0.001)，實(shí)際管電流明顯高于100 kV組(t=17.06，P<0.001)。兩組FOV差異無(wú)統(tǒng)計(jì)學(xué)意義(t=1.15，P=0.257)(表2)。

表1 兩組患者一般情況比較Table 1 Comparisons of the general data between two groups

BMI：體質(zhì)量指數(shù)

BMI：body mass index

BMI：體質(zhì)量指數(shù)；MPR：多平面重組圖像

BMI：body mass index；MPR：multi-planer reformation

A.男，44歲，體質(zhì)量60 kg，BMI為21.2 kg/m2，70 kV，右上肢注射20 ml對(duì)比劑，軸位MPR圖像顯示右側(cè)腋下靜脈(粗箭頭)未見明顯對(duì)比劑滯留，鄰近腋下動(dòng)脈(細(xì)箭頭)未見明顯靜脈偽影，評(píng)分為1分；B. 女，47歲，體質(zhì)量63 kg，BMI為24.6 kg/m2，右上肢注射對(duì)比劑40 ml，100 kV，軸位MPR圖像顯示右側(cè)腋下靜脈(粗箭頭)可見明顯對(duì)比劑滯留，鄰近腋下動(dòng)脈(細(xì)箭頭)可見少量線束偽影，評(píng)分為2分；C. 女，63歲，體質(zhì)量60 kg，BMI為26.0 kg/m2，左上肢注射對(duì)比劑20 ml，70 kV，軸位MPR圖像顯示左側(cè)腋下靜脈(粗箭頭)對(duì)比劑滯留，鄰近腋下動(dòng)脈(細(xì)箭頭)可見明顯線束偽影，影響動(dòng)脈管腔評(píng)價(jià)，評(píng)分為3分

A.a 44-year-old man，60 kg，BMI 21.2 kg/m2，70 kV， 20 ml of contrast media was injected in the right arm, on the axial MPR image，there was no obvious residue in the right axillary vein (thick arrow)and no obvious artifact in the right axillary artery (thin arrow), the score of venous artifacts was 1; B.a 47-year-old woman，63 kg，BMI 24.6 kg/m2，100 kV, 40 ml of the contrast media was injected in the right arm, on the axial MPR image，there was obvious residue in the right axillary vein (thick arrow)and slight artifacts in the right axillary artery (thin arrow), the score was considered as 2; C.a 63-year-old woman，60 kg，BMI 26.0 kg/m2，70 kV, 20 ml of contrast media was injected in the left arm, on the axial MPR image，there were some residues in the left axillary vein (thick arrow)and obvious artifacts in the left axillary artery, the score was considered as 3

圖1 靜脈偽影評(píng)分舉例

Fig 1 Exmaples of venous artifacts of contrast medium

表2 兩組掃描參數(shù)及輻射劑量的比較Table 2 Comparisons of the scan characteristics and radiation dose between two groups

FOV：視野；CTDIvol：CT容積劑量指數(shù)；DLP：劑量長(zhǎng)度乘積；ED：有效劑量

FOV：field of view；CTDIvol：CT dose index volume；DLP：dose-length product；ED：effective dose

靜脈偽影評(píng)分70 kV組20例患者中，16例(80.0%)存在靜脈偽影，其中6例(37.5%，6/16)的靜脈偽影影響鄰近動(dòng)脈的評(píng)價(jià)；100 kV組20例患者中，19例(95.0%)存在靜脈偽影，其中7例(36.8%，7/19)的靜脈偽影影響鄰近動(dòng)脈的評(píng)價(jià)；兩組間差異無(wú)統(tǒng)計(jì)學(xué)意義(Z=-0.878，P=0.380)。(表3、4，圖3、4)

對(duì)比劑滯留評(píng)分70 kV組20例患者中，13例(65.0%)對(duì)比劑滯留較明顯，其中2例(15.3%，2/13)對(duì)比劑滯留延續(xù)至上腔靜脈；100 kV組20例患者中，19例(95.0%)對(duì)比劑滯留較明顯，其中13例(68.4%，13/19)對(duì)比劑滯留延續(xù)至上腔靜脈；兩組間差異有統(tǒng)計(jì)學(xué)意義(Z=-3.654，P<0.001)。(表3、4，圖3、4)。

靜脈偽影及對(duì)比劑滯留評(píng)分相關(guān)性分析70 kV組中對(duì)比劑滯留與靜脈偽影評(píng)分一致的共9例(45%，9/20)，而靜脈偽影評(píng)分高于對(duì)比劑滯留評(píng)分的共9例(45%，9/20)，靜脈偽影評(píng)分低于對(duì)比劑滯留評(píng)分的共2例(10%，2/20)，兩者一致性差(κ=0.12，P=0.424)。100 kV組中對(duì)比劑滯留與靜脈偽影評(píng)分一致的也是9例(45%，9/20)，靜脈偽影評(píng)分高于對(duì)比劑滯留評(píng)分的共3例(15%，3/20)，靜脈偽影評(píng)分低于對(duì)比劑滯留評(píng)分的共8例(40%，8/20)，兩者一致性差(κ=0.068，P=0.680)(表3、4，圖3、4)。

討 論

管腔強(qiáng)化具有良好的均勻性,是CTA檢查顯示動(dòng)脈血管的必要條件。周圍結(jié)構(gòu)的強(qiáng)化需要低于動(dòng)脈強(qiáng)化才能有較好的重建質(zhì)量。靜脈污染和靜脈滯留導(dǎo)致靜脈內(nèi)強(qiáng)化程度較高，因此會(huì)影響周圍動(dòng)脈。導(dǎo)致靜脈滯留和靜脈高強(qiáng)化的常見原因包括靜脈反流、嚴(yán)重心力衰竭、呼氣、縱膈腫物、主動(dòng)脈瘤、頭臂靜脈狹窄及上腔靜脈綜合征[17- 21]。減少對(duì)比劑用量能從根本上改善靜脈污染及靜脈滯留的情況。

許多研究表明，減少對(duì)比劑用量，可以減少頭頸CTA靜脈偽影的程度。大多數(shù)研究是比較相同管電壓設(shè)置下，不同對(duì)比劑用量對(duì)靜脈偽影的影響。例如：Hinkmann等[3]采用128層螺旋CT掃描，觀察了不同對(duì)比劑用量對(duì)頸動(dòng)脈CTA圖像質(zhì)量的影響，管電壓均為120 kV，結(jié)果顯示，30 ml組頸內(nèi)靜脈的增強(qiáng)后CT值明顯低于80 ml組。30 ml組有9例患者注射同側(cè)的鎖骨下靜脈出現(xiàn)靜脈偽影，只有1例比較嚴(yán)重；80 ml組有13例鎖骨下靜脈出現(xiàn)靜脈偽影，8例患者比較嚴(yán)重。Chen等[2]研究發(fā)現(xiàn)，采用雙能量掃描，在相同的管電壓設(shè)置下，40 ml組頸內(nèi)靜脈偽影的評(píng)分明顯優(yōu)于50 ml組。其原因在于，對(duì)比劑用量減少時(shí)，對(duì)比劑團(tuán)注時(shí)間縮短，注射及掃描觸發(fā)的時(shí)間間隔將延長(zhǎng)，有利于隨后注射的鹽水對(duì)靜脈內(nèi)對(duì)比劑的稀釋；與之相反，對(duì)比劑用量增加，團(tuán)注時(shí)間延長(zhǎng)，注射及掃描觸發(fā)的時(shí)間間隔縮短，導(dǎo)致鹽水不能充分稀釋靜脈內(nèi)對(duì)比劑，因此對(duì)比劑滯留增加[4，22- 23]。以往只有少量研究是針對(duì)“雙低”模式的靜脈偽影，不過管電壓最低設(shè)置為80 kV。例如：Xia等[4]等采用64排CT，比較80 kV、較低對(duì)比劑用量(175 mgI/kg)，以及120 kV組、較多對(duì)比劑用量(350 mgI/kg)，結(jié)果表明前者的靜脈偽影評(píng)分優(yōu)于后者。

MIP：最大密度投影

MIP：maximum intensity projections

A. 男，44歲，體質(zhì)量60 kg，BMI為21.2 kg/m2，70 kV，右上肢注射對(duì)比劑20 ml，MIP圖像顯示右側(cè)腋下靜脈可見少量對(duì)比劑滯留(箭頭),對(duì)比劑滯留評(píng)分為1分；B.男，63歲，體質(zhì)量67 kg，BMI為26.1 kg/m2，70 kV，右上肢注射對(duì)比劑25 ml，MIP圖像顯示右側(cè)鎖骨下靜脈內(nèi)見明顯對(duì)比劑滯留，部分進(jìn)入右側(cè)頭臂靜脈(箭頭)，對(duì)比劑滯留評(píng)分為2分;C. 女，76歲，體質(zhì)量40 kg，BMI為17.8 kg/m2，70 kV，左上肢注射對(duì)比劑20 ml，MIP圖像顯示左側(cè)鎖骨下靜脈、左側(cè)頭臂靜脈及上腔靜脈(箭頭)內(nèi)均見對(duì)比劑滯留，對(duì)比劑滯留評(píng)分為3分

A.a 44-year-old man，60 kg，BMI 21.2 kg/m2， 20 ml of contrast medium was injected in the right arm, on the MIP image of 70 kV，only slight residues were seen in the axillary vein (arrow), the score of residues was 1; B.a 63-year-old man，67 kg，BMI 26.1 kg/m2, 25 ml of contrast medium was injected in the right arm，on the MIP image of 70 kV，obvious residues appeared in the right subclavian vein，parts of them went into the right brachiocephalic vein (arrow)，slight reflux was detected in the veins of neck (thin arrow),the score of residues was 2; C.a 76 year-old woman，40 kg，BMI 17.8 kg/m2, 20 ml of contrast media was injected in the left arm，on the MIP image of 70 kV，residues were present in the superior vena cava(thick arrow)，brachiocephalic and subclavian veins，and obvious reflux was detected in the veins of neck(thin arrow),the score of residues were 3

圖2 對(duì)比劑滯留評(píng)分舉例

Fig 2 Examples of venous residues of contrast media

表3 70 kV組患者靜脈偽影與對(duì)比劑滯留評(píng)分之間的關(guān)系Table 3 Relationship between contrast-medium residues and venous artifacts in 70 kV group

表4 100 kV組患者靜脈偽影與對(duì)比劑滯留評(píng)分之間的關(guān)系Table 4 Relationship between contrast-medium residues and venous artifacts in 100 kV

A.冠狀位MIP圖像顯示右側(cè)腋下靜脈(粗箭頭)少量對(duì)比劑滯留，對(duì)比劑滯留評(píng)分為1；B.軸位MPR圖像顯示相鄰右側(cè)腋下動(dòng)脈(細(xì)箭頭)存在明顯線束偽影，靜脈偽影評(píng)分為3分A.on the coronal MIP image，there was a little contrast-medium detected in the right axillary vein (thick arrow)，and the score of contrast-medium residues was 1; B.on axial MPR image，there were obvious artifacts detected in the right axillary artery (thin arrow)，and the score of venous artifacts was 3

圖3 70 kV組患者靜脈偽影評(píng)分與對(duì)比劑滯留評(píng)分不一致情況舉例：女，65歲，體質(zhì)量57 kg，BMI為22.83 kg/m2，右上肢注射對(duì)比劑20 ml

Fig 3 An example of patient in 70 kV group with the inconsistent scoring results between venous artifacts and contrast-medium residues：a 65-year-old woman，57 kg，BMI 22.83 kg/m2,20 ml of contrast-medium was injected in the right arm

A. 冠狀位MIP圖像顯示左側(cè)腋下靜脈、鎖骨下靜脈 (粗箭頭)大量對(duì)比劑滯留，延續(xù)至頭臂靜脈，對(duì)比劑滯留評(píng)分為2;B. 軸位MPR圖像顯示左側(cè)腋下動(dòng)脈(細(xì)箭頭)未見線束偽影，靜脈偽影評(píng)分為1分

A.on the coronal MIP image，there were amount of contrast-medium residues detected in the left axillary vein and subclavian artery (thick arrow)，extending to the left brachiocephalic vein, the score of contrast-medium residues was 2; B.on the axial MPR image，there were obvious artifacts detected in the right axillary artery (thin arrow)，and the score of venous artifacts was 1

圖4 100 kV組患者靜脈偽影評(píng)分與對(duì)比劑滯留評(píng)分不一致情況舉例：女，66歲，體質(zhì)量60 kg，BMI為23.44 kg/m2，左上肢注射對(duì)比劑40 ml

Fig 4 An example of patient in the 100 kV group with the inconsistent scoring results between venous artifacts and contrast-medium residues：a 66-year-old woman，60 kg，BMI 23.44 kg/m2，40 ml of contrast-medium was injected in the left arm

本研究采用70 kV，對(duì)比劑用量也進(jìn)一步降低，結(jié)果和文獻(xiàn)報(bào)道有所不同。雖然70 kV組患者對(duì)比劑滯留范圍少于100 kV組，但是靜脈偽影評(píng)分兩組無(wú)顯著差異。當(dāng)采用κ值進(jìn)行一致性檢驗(yàn)時(shí)，無(wú)論是70 kV 組還是100 kV組，對(duì)比劑滯留范圍與靜脈偽影評(píng)分均無(wú)相關(guān)性。70 kV組中，45%患者靜脈偽影評(píng)分高于對(duì)比劑滯留評(píng)分，說明部分患者對(duì)比劑滯留不太嚴(yán)重時(shí)，靜脈偽影卻比較明顯。100 kV中，40%患者靜脈偽影評(píng)分低于對(duì)比劑滯留評(píng)分，說明部分對(duì)比劑滯留明顯的患者，靜脈偽影反而不太明顯。因此，本研究中，對(duì)靜脈偽影評(píng)分產(chǎn)生影響的因素不僅有對(duì)比劑用量，還包括管電壓設(shè)置。

本研究存在以下局限性：(1)樣本量較小，在采用κ值對(duì)靜脈偽影與對(duì)比劑滯留范圍一致性進(jìn)行分析時(shí)，P均>0.05，影響了統(tǒng)計(jì)檢驗(yàn)效能，未來需要進(jìn)一步擴(kuò)大樣本量。(2)沒有采用統(tǒng)計(jì)學(xué)方法對(duì)管電壓及對(duì)比劑用量的交互效應(yīng)進(jìn)行分析，未來可以增加實(shí)驗(yàn)研究組進(jìn)一步研究。(3)70 kV組掃描方案只選擇1種迭代強(qiáng)度進(jìn)行重建，沒有比較不同迭代強(qiáng)度對(duì)于線束偽影影響的差異，今后可進(jìn)一步開展相關(guān)研究。

綜上，本研究結(jié)果顯示，第3代雙源CT 70 kV管電壓和20～25 ml對(duì)比劑模式下行頭頸聯(lián)合CTA，較100 kV掃描輻射劑量明顯下降，對(duì)比劑滯留明顯較低，靜脈偽影與100 kV組相近，具有良好的臨床應(yīng)用前景。

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Third-generation Dual-source CT for Head and Neck CT Angiography with 70 kV Tube Voltage and 20- 25 ml Contrast Medium in Patients With Body Weight Lower than 75 kg

CHEN Yu，ZHU Yuanli，XUE Huadan，WANG Yun，LI Yumei，ZHANG Zhuhua，JIN Zhengyu

Department of Radiology，PUMC Hospital，CAMS and PUMC，Beijing 100730，China

JIN Zhengyu Tel：010- 69155442，E-mail：jin_zhengyu@163.com

Objective To investigate the image quality of head and neck CT angiography (CTA)using the third-generation dual-source CT combined with 70 kV tube voltage and 20- 25 ml contrast medium (CM)，and evaluate the effects of venous artifacts arising from the CM on the ipsilateral side of injection. Methods Totally 40 consecutive patients with suspected vascular diseases and body weight lower than 75 kg prospectively underwent head and neck CTA examination using the third-generation dual-source CT. CTA was performed with a third-generation dual-source CT system. Patients were randomly divived into 70 kV group (n=20)and 100 kV group (n=20). The 70 kV group used 20- 25 ml CM and advanced modeled iterative reconstruction technique，and the 100 kV group used 40 ml CM and filtered back projection. Venous artifacts and CM residues were evaluated by a 3-point scale (1=excellent，3=poor)，respectively. Results The effective dose of 70 kV group decreased 58% compared to 100 kV group (t=-18.14，P<0.001).In the 70 kV group，16 patients (80.0%)presented with venous artifacts and six of them (37.5%，6/16)affected the adjacent arteries. In the 100 kV group，19 patients (95.0%)presented with venous artifacts，and seven of them (36.8%，7/19)affected the adjacent arteries (Z=-0.878，P=0.380). In the 70 kV group，13 patients (65.0%)presented with obvious CM residues and two of them (15.3%，2/13)prolonged into the superior vena cava (SVC). In the 100 kV group，19 patients(95.0%)presented with obvious CM residues，and thirteen of them(68.4%，13/19)prolonged into the SVC (Z=-3.654，P<0.001). Conclusion Compared with the 100 kV，the third-generation dual-source CT for head and neck CTA，combined with 70 kV and 20- 25 ml CM，can remarkably decrease the radiation dose，along with reduced CM residues and comparable venous artifacts.

third-generation dual-source CT；head and neck artery；CT angiography；contrast medium；tube voltage

國(guó)家臨床重點(diǎn)專科建設(shè)項(xiàng)目(2014)和衛(wèi)生公益性行業(yè)科研專項(xiàng)項(xiàng)目(201402019)Supported by the National Key Clinical Specialist Construction Programs of China(2014)and the Health Industry Special Scientific Research Project (201402019)

金征宇 電話：010- 69155442，電子郵件：jin_zhengyu@163.com

R814.42；R816.1；R364.32

A

1000- 503X(2017)01- 0004- 08

10.3881/j.issn.1000- 503X.2017.01.002

2016- 12- 15)