馬超 劉莉 李晶 王莉 邵成偉 方旭 陳士躍 陸建平
·論著·
3.0T磁共振擴(kuò)散加權(quán)成像信號(hào)強(qiáng)度對(duì)胰腺導(dǎo)管腺癌的診斷價(jià)值
馬超 劉莉 李晶 王莉 邵成偉 方旭 陳士躍 陸建平
目的探討3.0T磁共振擴(kuò)散加權(quán)成像(DWI)信號(hào)強(qiáng)度診斷胰腺導(dǎo)管腺癌的價(jià)值。方法 回顧性分析病理證實(shí)的70名胰腺導(dǎo)管腺癌患者及18名胰腺正常志愿者3.0 T上腹部相同掃描參數(shù)DWI(b值為0,600 s/mm2)資料,測(cè)量胰腺癌和正常胰腺的DWI信號(hào)強(qiáng)度(SIb0,SIb600)及表觀擴(kuò)散系數(shù)(ADC)值。計(jì)算測(cè)得的胰腺導(dǎo)管腺癌及正常胰腺SIb0、SIb600、ADC值的一致性系數(shù)(ICC)。胰腺癌與正常胰腺平均SIb0、SIb600和ADC值差異采用獨(dú)立樣本非參數(shù)Mann-WhitneyU檢驗(yàn),SIb0、SIb600和ADC值診斷胰腺導(dǎo)管腺癌的效能采用受試者工作特征曲線下面積(AUC)判斷。結(jié)果 兩位醫(yī)師測(cè)得的胰腺導(dǎo)管腺癌和正常胰腺的SIb0、SIb600及ADC值的一致性均為優(yōu)秀(ICC分別為0.977、0.983、0.961和0.969、0.979、0.973)。胰腺癌和正常胰腺的平均SIb0、SIb600及ADC值分別為1165.7±273.4、503.6±119.8、(1.40±0.20)×10-3mm2/s和650.9±104.5、263.7±49.1、(1.53±0.21)×10-3mm2/s,兩組間各參數(shù)的差異均具有統(tǒng)計(jì)學(xué)意義(P值均<0.05)。以正常胰腺SIb0、SIb600及ADC值為對(duì)照,診斷胰腺癌的AUC分別為0.987、0.980、0.697。SI診斷胰腺導(dǎo)管腺癌的價(jià)值顯著高于ADC(P值均<0.01)。以正常胰腺SIb600為參考,SIb600≤324.4作為診斷胰腺癌臨界值的敏感性和特異性分別為95.7%和94.4%。結(jié)論 3.0T DWI信號(hào)強(qiáng)度較ADC值對(duì)胰腺癌有更好的診斷價(jià)值,SI作為定量影像生物標(biāo)記在臨床應(yīng)用中應(yīng)當(dāng)予以重視。
胰腺腫瘤; 擴(kuò)散加權(quán)成像; 信號(hào)強(qiáng)度; 表觀擴(kuò)散系數(shù)
磁共振擴(kuò)散加權(quán)成像(diffusion-weighted imaging, DWI)在胰腺相關(guān)疾病的研究及應(yīng)用越來(lái)越廣泛?,F(xiàn)有報(bào)道主要關(guān)注于DWI計(jì)算的表觀擴(kuò)散系數(shù)(apparent diffusion coefficient,ADC)在胰腺疾病研究中的應(yīng)用。對(duì)胰腺癌而言,癌組織的ADC值顯著低于正常胰腺組織[1-8]。胰腺癌在DWI上往往表現(xiàn)為擴(kuò)散受限,即明顯的高信號(hào)強(qiáng)度(signal intensity,SI),臨床診斷中SI較ADC值更易獲得,但利用定量SI診斷胰腺癌的研究尚未見(jiàn)報(bào)道。本研究回顧性分析胰腺癌組織的3.0T DWI信號(hào)強(qiáng)度,探討其診斷胰腺癌的臨床價(jià)值。
一、一般資料
回顧性分析2014年1月至2014年12月上海長(zhǎng)海醫(yī)院術(shù)前行MRI檢查、術(shù)后經(jīng)病理證實(shí)的70例胰腺導(dǎo)管腺癌患者的DWI資料。收集同時(shí)段內(nèi)行MRI檢查的18名胰腺正常志愿者相同掃描參數(shù)的DWI資料作為對(duì)照。70例患者中男性43例,女性27例,年齡40~84歲,平均62歲。18位志愿者中男性14名,女性4名,年齡27~65歲,平均47歲。
二、掃描方法
所有MRI檢查均在3.0T超導(dǎo)磁共振儀(Signa HDxt, GE Healthcare, Milwaukee, USA)上完成。嵌入式體部線圈用于信號(hào)激發(fā),8通道體部相陣控線圈用于信號(hào)接收。掃描序列包括脂肪抑制快速自旋回波T2WI,重復(fù)時(shí)間/回波時(shí)間(TR/TE)=6 316/73.8 ms,采集矩陣320×192,視野(FOV) 36~40 cm,層數(shù)20,層厚5 mm,層間距1 mm,采集次數(shù)2次;呼吸觸發(fā)單次激發(fā)平面回波DWI(single-shot echo-planar DWI, ss EPI-DWI),b值為0及600 s/mm2,TR/TE=6 000/58.6 ms,采集矩陣128×96, FOV 38 cm×30.4 cm,層數(shù)20,層厚5 mm,層間距1 mm,采集次數(shù)2/4次,加速因子2,帶寬250 kHz;基于肝臟快速容積成像(liver acquisition with volume acceleration,LAVA),TR/TE=2.5/1.1 ms,帶寬125 kHz,反轉(zhuǎn)角 11°,采集矩陣256×180,F(xiàn)OV 44 cm×41.8 cm,層厚2.5 mm,層間距0 mm。胰腺癌患者最后行LAVA動(dòng)態(tài)增強(qiáng)掃描。
三、數(shù)據(jù)處理
利用工作站自帶軟件(Function 9.4.05,GE AW 4.4,USA)分析DWI數(shù)據(jù),重建ADC圖。DWI圖像在b0與b600下的信號(hào)強(qiáng)度(SIb0、SIb600)及ADC值由兩位經(jīng)驗(yàn)豐富的放射科醫(yī)師討論一致情況下獨(dú)立測(cè)量完成。因DWI圖像與ADC圖相互關(guān)聯(lián),ADC值測(cè)量時(shí),同一感興趣區(qū)(region of interest, ROI)SIb0及SIb600自動(dòng)計(jì)算出來(lái)。對(duì)照組數(shù)據(jù)測(cè)量時(shí)參考T2及LAVA圖像,避開(kāi)主胰管、動(dòng)脈血管及偽影,采用圓形或橢圓形ROI對(duì)每位志愿者胰腺?gòu)念^至尾部測(cè)量3個(gè)值[9-10],平均值作為每個(gè)正常胰腺的定量參數(shù)。胰腺癌組數(shù)據(jù)測(cè)量時(shí)選擇較為實(shí)性均勻部分,避開(kāi)偽影、腫塊邊緣及囊變壞死出血區(qū),并注意觀察相鄰層面,避免ROI過(guò)大造成部分容積效應(yīng)帶來(lái)的誤差。ROI范圍為51~696 mm2,平均219 mm2。
四、統(tǒng)計(jì)學(xué)處理
應(yīng)用SPSS16.0及Medcalc 12.7.0.0統(tǒng)計(jì)軟件進(jìn)行統(tǒng)計(jì)學(xué)分析。計(jì)算兩位測(cè)量者測(cè)定的胰腺導(dǎo)管腺癌及正常胰腺SIb0、SIb600、ADC值的測(cè)量一致性系數(shù)(intra-class correlation coefficient, ICC)。胰腺導(dǎo)管腺癌與正常胰腺SIb0、SIb600和ADC值的差異采用獨(dú)立樣本非參數(shù)Mann-WhitneyU檢驗(yàn),P<0.05為差異具有統(tǒng)計(jì)學(xué)意義;SIb0、SIb600和ADC值診斷胰腺導(dǎo)管腺癌的效能應(yīng)用受試者工作特征曲線(receiver-operating characteristic, ROC)分析,比較曲線下面積(area under the curve, AUC)的差異,經(jīng)Bonferroni矯正的P<0.017為差異具有統(tǒng)計(jì)學(xué)意義。
一、SI與ADC值測(cè)量的一致性
在DWI圖像上,胰腺導(dǎo)管腺癌較周圍組織表現(xiàn)出明顯的高信號(hào)。兩醫(yī)師測(cè)得的胰腺癌SIb0值分別為1161.8±278.4、1167.5±271.4;SIb600值分別為504.6±123.0、502.5±117.6;ADC值分別為(1.39±0.19×)10-3、(1.40±0.20×)10-3mm2/s。兩醫(yī)師間具有較優(yōu)秀的一致性(ICC分別為0.977、0.983、0.961)。
對(duì)照組MRI圖像未顯示胰腺異常信號(hào),DWI圖像未見(jiàn)明顯偽影,胰腺邊界清晰。兩醫(yī)師測(cè)得的正常胰腺SIb0值分別為652.7±102.2、649.1±108.3;SIb600值分別為263.2±48.2、264.1±50.4;ADC值分別為(1.53±0.21)×10-3、1.53±0.21×10-3mm2/s。兩醫(yī)師間亦具有較優(yōu)秀的一致性(ICC分別為0.969、0.979、0.973)。
二、胰腺導(dǎo)管腺癌與正常胰腺間SI、ADC值的差異
胰腺導(dǎo)管腺癌的平均SIb0、SIb600值分別為1165.7±273.4、503.6±119.8;正常胰腺分別為650.9±104.5、263.7±49.1,胰腺導(dǎo)管腺癌顯著高于正常胰腺,差異有統(tǒng)計(jì)學(xué)意義(Z值分別為-6.352、-6.258,P值均<0.001)。胰腺導(dǎo)管腺癌ADC值為(1.40±0.20×)10-3mm2/s,正常胰腺為(1.53±0.21×)10-3mm2/s,胰腺導(dǎo)管腺癌ADC值顯著低于正常胰腺,差異有統(tǒng)計(jì)學(xué)意義(Z=-0.510,P=0.012)。
三、SI與ADC值診斷胰腺導(dǎo)管腺癌的效能
以正常胰腺平均SIb0、SIb600和ADC值為參考,診斷胰腺導(dǎo)管腺癌的AUC分別為0.987(95%CI0.936~1.000)、0.980(95%CI0.925~0.998)、0.697(95%CI0.590~0.790)。SIb0、SIb600分別以758.9、324.4及ADC以1.395×10-3mm2/s為Cutoff值,SIb0診斷胰腺導(dǎo)管腺癌的敏感性及特異性分別為97.1%(95%CI0.901~0.997)、94.4%(95%CI0.727~0.999),SIb600為95.7%(95%CI0.880~0.991)、94.4%(95%CI0.727~0.999),ADC為61.4%(95%CI0.490~0.728)、77.8%(95%CI0.524~0.936)。SIb0、SIb600的診斷價(jià)值顯著高于ADC值(Z值分別為4.226、4.470,P值均<0.001),而SIb0與SIb600間的差異無(wú)統(tǒng)計(jì)學(xué)意義(Z=0.615,P=0.538,圖1)。
圖1 SIb0、SIb600、ADC值診斷胰腺導(dǎo)管腺癌的ROC曲線
DWI最常用序列是ss EPI,常通過(guò)采集一個(gè)沒(méi)有加權(quán)的數(shù)據(jù)(SIb0)和一個(gè)擴(kuò)散權(quán)重為b的數(shù)據(jù)(SIb)計(jì)算ADC值,反映水分子擴(kuò)散快慢,計(jì)算公式為SIb/SIb0=exp(-b×ADC)。這個(gè)模型通常稱為單指數(shù)模型(mono-exponential),其優(yōu)點(diǎn)是模型簡(jiǎn)單,計(jì)算結(jié)果穩(wěn)定,目前已廣泛應(yīng)用到臨床檢查中[11]。DWI 是唯一在體測(cè)量組織內(nèi)水分子擴(kuò)散的MRI方法,提供了常規(guī)MRI無(wú)法獲得的組織微觀結(jié)構(gòu)信息,可用于腫瘤的良惡性鑒別、療效評(píng)估和早期發(fā)現(xiàn)等方面,在胰腺疾病診斷與鑒別診斷中體現(xiàn)出重要價(jià)值[1-8]。最新研究表明[1],DWI聯(lián)合常規(guī)增強(qiáng)MRI診斷小胰腺癌(<3 cm)的效能顯著高于常規(guī)增強(qiáng)MRI(敏感性97.0%比75.5%,特異性92.0%比87.5%)。在胰腺相關(guān)疾病研究中,以往報(bào)道往往關(guān)注于ADC值在胰腺癌與正常組織的差異對(duì)比及診斷效能評(píng)估,忽略了DWI信號(hào)強(qiáng)度的價(jià)值[1-8],SI作為最易獲得的定量參數(shù)診斷胰腺癌價(jià)值的研究尚未見(jiàn)報(bào)道。本研究報(bào)道了DWI信號(hào)強(qiáng)度診斷胰腺癌的價(jià)值,結(jié)果表明SI顯著高于ADC值獲得的AUC,與在直腸癌相關(guān)研究中的報(bào)道一致[12]。
除了組織本身特征影響DWI信號(hào)強(qiáng)度及ADC值外,DWI技術(shù)也會(huì)對(duì)定量參數(shù)有一定的影響。本研究中DWI選擇呼吸觸發(fā)技術(shù)的目的是最大程度地保證胰腺DWI圖像質(zhì)量及定量參數(shù)的可靠性[13-15]。擴(kuò)散加權(quán)的權(quán)重b值是DWI最重要的掃描參數(shù),b值為600 s/mm2是長(zhǎng)海醫(yī)院胰腺DWI掃描中規(guī)范的序列參數(shù),目的是減少掃描時(shí)間、圖像變形及偽影,且可有效降低ADC值測(cè)量中T2透射效應(yīng)帶來(lái)的誤差,使ADC值更接近于真實(shí)值[16-17]。另外,Koc等[18]研究了腹部病變DWI b值的選擇,認(rèn)為b值≥600 s/mm2是推薦的掃描參數(shù)。本研究發(fā)現(xiàn),基于b值為600 s/mm2的呼吸觸發(fā)DWI獲得的SI及ADC值具有較好的組間測(cè)量一致性,獲得的胰腺癌ADC值顯著低于正常胰腺組織,與大量文獻(xiàn)中報(bào)道的結(jié)果一致[1-8]。
DWI中SI較ADC值更容易測(cè)量,且不會(huì)因運(yùn)動(dòng)等因素造成不同b值下相同掃描層面的不匹配帶來(lái)的ADC值計(jì)算誤差。在臨床診斷中SI除了用于定性描述病變特征外,也可以用于病變的定量分析。但在臨床掃描中,DWI掃描參數(shù)往往因操作者習(xí)慣不同稍作更改,對(duì)SI定量分析影響很大。本研究選擇同一MR設(shè)備、相同參數(shù)對(duì)胰腺癌患者和胰腺正常志愿者的DWI數(shù)據(jù)進(jìn)行定量分析,并與ADC值診斷胰腺癌的價(jià)值進(jìn)行比較,發(fā)現(xiàn)SIb0與SIb600對(duì)胰腺癌診斷效能皆顯著高于ADC值。值得注意的是,盡管SIb0與SIb600獲得的AUC之間差異不具有統(tǒng)計(jì)學(xué)意義,但胰腺導(dǎo)管腺癌在DWIb600圖像上具有更好的組織對(duì)比度,因此,當(dāng)進(jìn)行胰腺DWI研究時(shí),SIb600作為定量影像生物標(biāo)記在臨床應(yīng)用中應(yīng)當(dāng)予以重視。
[1] Park MJ, Kim YK, Choi SY, et al. Preoperative detection of small pancreatic carcinoma: value of adding diffusion-weighted imaging to conventional MR imaging for improving confidence level[J]. Radiology, 2014, 273(2):433-443.
[2] Akisik MF, Aisen AM, Sandrasegaran K, et al. Assessment of chronic pancreatitis: utility of diffusion-weighted MR imaging with secretin enhancement[J]. Radiology, 2009, 250(1): 103-109.
[3] Ichikawa T, Erturk SM, Motosugi U, et al. High-b value diffusion-weighted MRI for detecting pancreatic adenocarcinoma: preliminary results[J]. Am J Roentgenol, 2007, 188(2): 409-414.
[4] Kartalis N, Lindholm TL, Aspelin P, et al. Diffusion-weighted magnetic resonance imaging of pancreas tumours[J]. Eur Radiol, 2009, 19(8): 1981-1990.
[5] Klauss M, Lemke A, Grunberg K, et al. Intravoxel incoherent motion MRI for the differentiation between mass forming chronic pancreatitis and pancreatic carcinoma[J]. Invest Radiol, 2011, 46(1): 57-63.
[6] Schoennagel BP, Habermann CR, Roesch M, et al. Diffusion-weighted imaging of the healthy pancreas: Apparent diffusion coefficient values of the normal head, body, and tail calculated from different sets of b-values[J]. J Magn Reson Imaging, 2011, 34(4): 861-865.
[7] Akisik MF, Sandrasegaran K, Jennings SG, et al. Diagnosis of chronic pancreatitis by using apparent diffusion coefficient measurements at 3.0-T MR following secretin stimulation[J]. Radiology, 2009, 252(2): 418-425.
[8] 姚秀忠, 曾蒙蘇, 饒圣祥, 等. 3.0 T MR灌注加權(quán)成像和擴(kuò)散加權(quán)成像在胰腺腫塊診斷中應(yīng)用[J]. 中華放射學(xué)雜志, 2012, 45(7): 646-652.
[9] Schoennagel BP, Habermann CR, Roesch M,et al.Diffusion-weighted imaging of the healthy pancreas: apparent diffusion coefficient values of the normal head, body, and tail calculated from different sets of b-values[J].J Magn Reson Imaging, 2011, 34(4):861-865.
[10] 潘春樹(shù),馬超,汪劍,等.胰腺不同部位表觀擴(kuò)散系數(shù)正常值初探[J].中華胰腺病雜志, 2012,12(5):310-312.
[11] Lee SS, Byun JH, Park BJ, et al. Quantitative analysis of diffusion-weighted magnetic resonance imaging of the pancreas: usefulness in characterizing solid pancreatic masses[J]. J Magn Reson Imaging, 2008, 28(4):928-936.
[12] Cai PQ, Wu YP, An X, et al. Simple measurements on diffusion-weighted MR imaging for assessment of complete response to neoadjuvant chemoradiotherapy in locally advanced rectal cancer[J]. Eur Radiol, 2014, 24(11):2962-2970.
[13] Kartalis N, Loizou L, Edsborg N, et al. Optimising diffusion-weighted MR imaging for demonstrating pancreatic cancer: a comparison of respiratory-triggered, free-breathing and breath-hold techniques[J]. Eur Radiol, 2012, 22(10):2186-2192.
[14] Kwee TC, Takahara T, Koh DM, et al. Comparison and reproducibility of ADC measurements in breathhold, respiratory triggered, and free-breathing diffusion-weighted MR imaging of the liver[J]. J Magn Reson Imaging, 2008, 28(5):1141-1148.
[15] Ma C, Wang J, Li Y, et al. Comparisons of Image Quality and ADCs in Breath-Hold, Respiratory-Triggered and Free-Breathing DWI of Pancreas at 3-T[J]. Open Journal of Radiology, 2014, 4:279-292.
[16] Murtz P, Flacke S, Tr?ber F, et al. Abdomen: diffusion weighted MR imaging with pulse-triggered single shot sequences[J]. Radiology, 2002, 224(1):258-264.
[17] Matsuki M, Inada Y, Nakai G, et al. Diffusion-weighed MR imaging of pancreatic carcinoma[J]. Abdom Imaging, 2007, 32(4):481-483.
[18] Koc Z, Erbay G. Optimal b value in diffusion-weighted imaging for differentiation of abdominal lesions[J]. J Magn Reson Imaging, 2014, 40(3):559-566.
(本文編輯:呂芳萍)
The value of signal intensity of diffusion weighted 3.0T magnetic resonance imaging in the diagnosis of pancreatic cancer
MaChao,LiuLi,LiJing,WangLi,ShaoChengwei,FangXu,ChenShiyue,LuJianping.DepartmentofRadiology,ChanghaiHospital,SecondaryMilitaryMedicalUniversity,Shanghai200433,China
Correspondingauthor:LuJianping,Email:cjr.lujianping@vip.163.com
Objective To investigate the value of signal intensity (SI) of diffusion weighted imaging(DWI) at 3.0 T magnetic resonance in the diagnosis of pancreatic adenocarcinoma. Methods Seventy patients with histologically confirmed pancreatic ductal adenocarcinoma and 18 healthy volunteers underwent DWI at 3.0 T (b=0, 600 s/mm2). The SIb0,SIb600and apparent diffusion coefficient (ADC) values of normal pancreas as well as the pancreatic adenocarcinomas were measured by two independent observers. The inter-observer variability for SIb0, SIb600and ADC values was analyzed by using interclass correlation coefficient (ICC). The SIb0, SIb600and ADC values between the tumors and normal pancreatic tissues were analyzed and compared by using Mann-WhitneyUtest, and receiver-operating characteristic (ROC) analyses were used to determine the diagnostic performances of the three parameters to distinguish pancreatic adenocarcinoma from normal pancreas. Results All the SIb0,SIb600and ADC indicated excellent inter-observer variability. ICC values for ADC, SIb0, SIb600of pancreatic adenocarcinoma were 0.977, 0.983, 0.961, and ICC values of normal pancreas were 0.969, 0.979, 0.973. The mean SIb0, SIb600and ADC values were 1165.7±273.4, 503.6±119.8, (1.40±0.20)×10-3mm2/s in pancreatic adenocarcinoma, and650.9±104.5,263.7±49.1, (1.53±0.21)×10-3mm2/s in normal pancreas, and the difference between the two groups was statistically significant (P<0.01). With the SIb0、SIb600and ADC values of normal pancreas as a reference, the area under ROC curve (AUC) were 0.987, 0.980 and 0.697, respectively. SI was significantly better than ADC for diagnosis of pancreatic adenocarcinoma (P<0.01). With the SIb600of normal pancreas as a reference, SIb600≤324.4 as the cutoff value for diagnosis of pancreatic adenocarcinoma, the sensitivity and specificity were 95.7% and 94.4%. Conclusions SI of DWI at 3.0 T has a better diagnostic accuracy in the diagnosis of pancreatic ductal adenocarcinoma than ADC. As a quantitative imaging bio-marker in clinical practice, SI should be valued.
Pancreatic neoplasms; Diffusion weighted imaging; Signal intensity; Apparent diffusion coefficient
10.3760/cma.j.issn.1674-1935.2015.06.001
上海市自然科學(xué)基金(14ZR1408300);上海市科委醫(yī)學(xué)引導(dǎo)項(xiàng)目(14411960100);長(zhǎng)海醫(yī)院“1255”學(xué)科建設(shè)計(jì)劃(CH125520800,CH125510102,CH125510302);長(zhǎng)海醫(yī)院青年科研啟動(dòng)基金(2013002)
200433 上海,第二軍醫(yī)大學(xué)附屬長(zhǎng)海醫(yī)院放射科
陸建平,Email:cjr.lujianping@vip.163.com
2015-03-10)