MR多參數(shù)成像評(píng)估慢性胰腺炎臨床分級(jí)的價(jià)值

柏梅 陸建平 賴曉偉

·論著·

MR多參數(shù)成像評(píng)估慢性胰腺炎臨床分級(jí)的價(jià)值

柏梅 陸建平 賴曉偉

目的探討應(yīng)用多種MRI技術(shù)評(píng)估慢性胰腺炎(CP)臨床分級(jí)的價(jià)值。方法納入經(jīng)病理和臨床隨訪證實(shí)的65例CP患者，按M-annheim分級(jí)分為輕度組(14例)、中度組(37例)和進(jìn)展組(14例)，并以20例健康志愿者作為對(duì)照。在上腹部常規(guī)T1WI及T2WI抑脂掃描后，進(jìn)行胰腺M(fèi)RCP檢查及胰腺動(dòng)態(tài)MR檢查。測(cè)量T1WI、T2WI加權(quán)掃描的胰腺實(shí)質(zhì)信號(hào)及肝臟信號(hào)，獲取它們的比值(rT1、rT2)，根據(jù)MRCP測(cè)量主胰管最大直徑(MPD)，并對(duì)胰腺病變進(jìn)行評(píng)估、分類；測(cè)量動(dòng)態(tài)MR增強(qiáng)時(shí)胰腺實(shí)質(zhì)信號(hào)值，并計(jì)算強(qiáng)化率；ROC分析MRI表現(xiàn)與CP臨床分級(jí)的相關(guān)性。結(jié)果正常、輕度、中度和進(jìn)展組rT1分別為0.98±0.27、0.84±0.12 、0.81±0.16和0.75±0.24，中度、進(jìn)展組較正常組明顯降低(P﹤0.01)；rT2分別為1.28±0.30、1.46±0.44、1.46±0.55和1.76±0.72，各組間無(wú)統(tǒng)計(jì)學(xué)差異；MPD為(2.0±0.6)mm、(5.4±2.4)mm、(6.5±3.3)mm和(8.1±4.1)mm，各組間差異顯著(P值均﹤0.01)。輕度、中度和進(jìn)展組的劍橋重度分級(jí)分別有4例(29%)、33例(90%)和13例(93%),差異顯著(P﹤0.01)；胰管結(jié)石分別有2例(14%)、11例(30%)和5例(36%)，胰腺假性囊腫分別有0例、6例(16%)和3例(21%)，胰腺萎縮分別有4例( 29%)、 22例(60%)和10例(71%)，各組間均無(wú)統(tǒng)計(jì)學(xué)差異。正常、輕度、中度和進(jìn)展組的胰腺動(dòng)態(tài)增強(qiáng)掃描實(shí)質(zhì)期與動(dòng)脈期胰腺信號(hào)強(qiáng)化率比值(P/A)分別為0.88±0.08、1.10±0.08、1.37±0.15和1.48±0.53，各組間差異顯著(P﹤0.05)。rT1值、劍橋分級(jí)、胰管直徑及P/A比值與臨床分級(jí)均有相關(guān)性(r值分別為0.34、0.41、0.62、-0.43)。ROC分析顯示，MPD>2.5 mm、rT1<0.8、P/A>0.8診斷CP均有較好的敏感性和特異性，三者結(jié)合時(shí)診斷CP的特異性可提高到95%。結(jié)論應(yīng)用磁共振的 T1WI、MRCP及動(dòng)態(tài)增強(qiáng)檢查能準(zhǔn)確、良好地評(píng)估CP的嚴(yán)重程度，其中MRCP的敏感性及特異性最高，其次是動(dòng)態(tài)增強(qiáng)檢查與T1平掃。

胰腺炎，慢性; 磁共振成像; 動(dòng)態(tài)增強(qiáng)

隨著慢性胰腺炎(CP)的病因?qū)W、流行病學(xué)、遺傳學(xué)以及影像學(xué)技術(shù)的發(fā)展，CP的臨床分類越來(lái)越完善[1]。德國(guó)海德堡大學(xué)Schneider等[2]建立的M-ANNHEIM分類系統(tǒng)能簡(jiǎn)單、客觀、精確和相對(duì)非侵害性地對(duì)CP進(jìn)行臨床分級(jí)，并采納了CP劍橋分級(jí)系統(tǒng)[3]。隨著成像速度的加快和圖像信噪比的提高，MRI在CP的影像檢查中所起的作用逐漸加大，其多參數(shù)成像更是為胰腺病變提供了豐富的檢查序列。本研究分析臨床不同嚴(yán)重程度的慢性胰腺炎(CP)的各種MRI表現(xiàn)，評(píng)估MRI多種成像技術(shù)在CP臨床分級(jí)中的價(jià)值。

材料與方法

一、臨床資料

收集第二軍醫(yī)大學(xué)長(zhǎng)海醫(yī)院2008年4月至2009年10月確診的CP患者65例，以20例健康者作為正常組。按M-annheim評(píng)分將CP患者分為輕度、中度、進(jìn)展3組，分別有14例、37例和14例。

二、掃描方法

所有掃描均采用Siemens Avanto 1.5T MR掃描儀。掃描序列和參數(shù)：T1WI采用三維容積內(nèi)插快速擾相梯度回波序列，橫斷面掃描，脂肪抑制，TR 5.8 ms，TE 2.6 ms，激勵(lì)次數(shù)1，F(xiàn)A10，矩陣142×256，F(xiàn)OV 300 mm×400 mm，層厚3.0 mm。T2WI采用快速自旋回波序列，橫斷面掃描，脂肪抑制，TR 7000～9000 ms，TE 104 ms，激勵(lì)次數(shù)2，矩陣173×384，F(xiàn)OV 300 mm×400 mm，層厚5 mm，層間距10%。MRCP采用單次激發(fā)半傅里葉采集快速自旋回波序列，厚層MRCP TR 4500 ms，TE 754 ms，激勵(lì)次數(shù)1，F(xiàn)A180，矩陣308 mm×384 mm，F(xiàn)OV 350×350，模塊厚69.8 mm；薄層MRCP TR 1210 ms，TE 114 ms，激勵(lì)次數(shù)1，F(xiàn)A 125，矩陣192×320，F(xiàn)OV 329×329，層厚3.5 mm，層間距10%。橫斷面屏氣抑脂T1加權(quán)動(dòng)態(tài)增強(qiáng)掃描，完全重復(fù)增強(qiáng)前的序列。使用高壓注射器經(jīng)靜脈注射Gd-DTPA，劑量0.2 mmol/kg，流速3 ml/s，注射后18、26和38 s重復(fù)采集，獲取動(dòng)脈期、實(shí)質(zhì)期及延遲期圖像。

三、圖像評(píng)價(jià)及分析

由兩位對(duì)胰腺疾病診斷有豐富經(jīng)驗(yàn)的高級(jí)職稱醫(yī)師共同閱片。影像評(píng)價(jià)指標(biāo)：測(cè)量正常組和CP組T1WI、T2WI掃描的胰腺實(shí)質(zhì)信號(hào)及肝臟信號(hào)，獲得它們的比值(rT1、rT2)；測(cè)量主胰管最大直徑(MPD)；記錄胰管結(jié)石、假性囊腫、胰腺萎縮狀況；進(jìn)行劍橋程度分級(jí)；測(cè)量胰腺動(dòng)脈期、實(shí)質(zhì)期及延遲期的信號(hào)強(qiáng)度，并計(jì)算各期的胰腺?gòu)?qiáng)化率，強(qiáng)化率=(強(qiáng)化后的胰腺信號(hào)均值- T1平掃的胰腺信號(hào)均值)/T1平掃的胰腺信號(hào)均值；ROI的選擇盡可能大，但不能達(dá)到臟器邊緣，胰腺各部位ROI還要避開(kāi)肉眼可見(jiàn)的大血管，以減少部分容積效應(yīng)對(duì)結(jié)果準(zhǔn)確性的影響，肝臟選取肝右葉，避開(kāi)膽管、血管及肝內(nèi)病變，部分病例胰腺某部位明顯萎縮而無(wú)法測(cè)量則為空缺值。

四、數(shù)據(jù)統(tǒng)計(jì)分析

采用SPSS17.0軟件包。計(jì)量資料采用單因素方差分析，計(jì)數(shù)資料采用χ2檢驗(yàn)；各項(xiàng)MRI表現(xiàn)與CP臨床分級(jí)的關(guān)系采用spearman秩相關(guān)分析；有統(tǒng)計(jì)學(xué)差異的變量作為評(píng)估參數(shù)行ROC分析。P﹤0.05有統(tǒng)計(jì)學(xué)意義。

結(jié) 果

一、MRI掃描圖征象及參數(shù)的變化

65例CP患者中，T1信號(hào)降低37例，其中32例全程不均勻降低，1例局限于胰尾，4例局限于胰腺頭頸部；T2信號(hào)的改變多樣，感染時(shí)可輕度增高或呈不均勻信號(hào)改變。正常、輕度、中度、進(jìn)展組的rT1值分別為0.98±0.27、0.84±0.12、0.81±0.16和0.75±0.24，中度和進(jìn)展組較正常組明顯降低(P﹤0.01)。rT1值與CP臨床分級(jí)相關(guān)(r=0.34，P<0.01)。正常、輕度、中度、進(jìn)展組的rT2值分別為1.28±0.30、1.46±0.44、1.46±0.55和1.76±0.72，各組間無(wú)顯著差異。

正常、輕度、中度、進(jìn)展組的MPD分別為(2.0±0.6)mm、(5.4±2.4)mm、(6.5±3.3)mm和(8.1±4.1)mm，CP組較正常組明顯增大(P﹤0.01)，進(jìn)展組又較輕度組明顯增大(P﹤0.05)。MPD與CP臨床分級(jí)相關(guān)(r=0.62，P<0.01)。

根據(jù)CP劍橋分級(jí)，輕度、中度、進(jìn)展組的中度分級(jí)者分別有7例(50%)、2例(5%)和1例(7%)；重度分級(jí)者有4例(29%)、33例(89%)和13例(93%)。中度和進(jìn)展組的劍橋重度分級(jí)者較輕度組顯著增加(P<0.01)。劍橋分級(jí)與CP臨床分級(jí)相關(guān)(r=0.41，P<0.01)。

主胰管擴(kuò)張59例，主胰管狹窄并遠(yuǎn)端擴(kuò)張1例，主胰管未見(jiàn)異常5例。胰管結(jié)石18例，其中輕度組2例(14%)，中度組11例(30%)，進(jìn)展組5例(36%)。胰腺假性囊腫9例，其中中度組6例(16%)，進(jìn)展組有3例(21%)。胰腺萎縮36例，輕、中、進(jìn)展組分別有4例(29%)、22例(60%)和10例(71%)。各組間均無(wú)顯著差異。

rT1、MPD的ROC見(jiàn)圖1和表1。以MPD>2.5 mm為界，診斷CP的敏感性94%，特異性79%；以rT1<0.8為界，敏感性90%，特異性48%。

二、MRI動(dòng)態(tài)增強(qiáng)圖征象及參數(shù)的變化

正常組的胰腺?gòu)?qiáng)化峰值在注射造影劑18 s后的動(dòng)脈期出現(xiàn)，實(shí)質(zhì)期和延遲期造影劑緩慢退出，實(shí)質(zhì)期與動(dòng)脈期胰腺信號(hào)強(qiáng)化率比(P/A)<1；CP組的胰腺?gòu)?qiáng)化峰值在注射造影劑26 s后的實(shí)質(zhì)期出現(xiàn)，輕度、中度和進(jìn)展組的P/A值分別為1.10±0.08、1.37±0.15和1.48±0.53，各組間差異明顯(P﹤0.05，表2)。P/A值與CP臨床分級(jí)相關(guān)(r=-0.43，P<0.01)。以P/A值>0.8為界，診斷CP的敏感性95%，特異性47%，結(jié)合MPD>2.5 mm及rT1<0.8診斷CP的特異性可提高到95%。

圖1 rT1、MPD及P/A的ROC曲線圖

變量截?cái)帱c(diǎn)敏感性(%)特異性(%)Kappa值A(chǔ)UC(%)P值MPD2.594790.7280.9580.000rT10.890480.2950.7240.003P/A0.895470.4920.7890.000

注：AUC為曲線下面積

討 論

早期確診CP及對(duì)其嚴(yán)重程度進(jìn)行分級(jí)對(duì)于CP的治療、患者的預(yù)后、生活質(zhì)量的提高等均有重要的影響。多年來(lái)人們制定了不同的CP臨床分級(jí)方式，如Marseilles系統(tǒng)[4-5]、Amman的CP分期標(biāo)準(zhǔn)[6]、Chari系統(tǒng)[7]、Ramesh的ABC系統(tǒng)[4]。M-ANNHEIM評(píng)分系統(tǒng)[2]等影像學(xué)檢查可為CP患者提供多項(xiàng)參數(shù)。

表2 正常組和CP各組胰腺信號(hào)強(qiáng)化率及P/A值

本組采用MRCP技術(shù)測(cè)量MPD，發(fā)現(xiàn)CP臨床分級(jí)越重，主胰管直徑擴(kuò)張?jiān)矫黠@。當(dāng)主胰管直徑>2.5 mm時(shí)診斷CP的敏感性達(dá)94%，特異性為79%。此外，MRCP能發(fā)現(xiàn)直徑在2 mm以上的結(jié)石[8]以及與胰管不相通的假性囊腫。CP臨床分級(jí)越重，結(jié)石或囊腫的出現(xiàn)概率也越高。

胰腺實(shí)質(zhì)T1及T2信號(hào)的改變是CP的影像學(xué)表現(xiàn)之一。臨床經(jīng)驗(yàn)顯示，胰肝信號(hào)強(qiáng)度的比是鑒別胰腺實(shí)質(zhì)正常與否最好的指標(biāo)[9]。本組結(jié)果發(fā)現(xiàn)，CP組T1加權(quán)像上胰腺信號(hào)常有不同程度的降低，且CP臨床分級(jí)越重，T1信號(hào)降低越明顯。當(dāng)T1信號(hào)比值<0.8時(shí)診斷CP有較高的敏感性和一定的特異性，有一定的臨床應(yīng)用價(jià)值。T2加權(quán)成像可以顯示感染而造成的胰腺T2信號(hào)輕度增高或不均勻信號(hào)改變[7]。磁共振平掃的不足之處在于對(duì)CP鈣化的顯示遠(yuǎn)不及CT。本組有3例CT顯示的胰腺鈣化，在磁共振檢查時(shí)未發(fā)現(xiàn)。

Zhang等[10]研究發(fā)現(xiàn)，Gd-DTPA動(dòng)態(tài)增強(qiáng)時(shí)，T1WI上正常胰腺信號(hào)動(dòng)脈期升高最明顯，而CP時(shí)胰腺信號(hào)則在靜脈早期或延遲期增加最明顯，胰腺靜脈早期與動(dòng)脈早期的信號(hào)強(qiáng)度比﹤1.7以及胰腺峰值強(qiáng)化延遲診斷早期CP的敏感性為92%，特異性為75%，明顯高于僅靠胰腺形態(tài)學(xué)改變?cè)\斷的50%的敏感性，提示血供改變有時(shí)在CP早期無(wú)明顯主胰管形態(tài)學(xué)改變之前發(fā)生。Johnson等[11]研究亦證實(shí)，Gd-DTPA動(dòng)態(tài)增強(qiáng)T1WI脂肪抑制像上CP患者胰腺實(shí)質(zhì)呈逐漸強(qiáng)化，與正常胰腺在動(dòng)脈期或門脈期明顯強(qiáng)化不同，從而有利于CP的發(fā)現(xiàn)。本組結(jié)果發(fā)現(xiàn)CP患者的胰腺?gòu)?qiáng)化峰值較正常組推遲，常出現(xiàn)在實(shí)質(zhì)期，且隨著CP程度加重，胰腺?gòu)?qiáng)化延遲越明顯，當(dāng)P/A值>0.8時(shí)診斷CP的敏感性高達(dá)95%，特異性也有47%。

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2010-07-04)

(本文編輯：呂芳萍)

EvaluationofMRmultiparameterimagingforclinicalclassificationofchronicpancreatitis

BAIMei,LUJian-ping,LAIXiao-wei.

DepartmentofRadiology,ChanghaiHospital,SecondMilitaryMedicalUniversity,Shanghai200433,China

LUJian-ping,Email:cjr.lujianping@vip.163.com

ObjectiveTo investigate the value of MR multiparameter imaging for the clinical classification of chronic pancreatitis.Methods65 patients with confirmed chronic pancreatitis by follow-up and pathologic examinations (14 mild, 37 moderate and 14 severe according to MANNHEIM system) and 20 healthy volunteers were included in this study. MR examination including routine T1WI, T2WI, MRCP and dynamic enhanced MRI. The data were measured and statistical analysis was applied in four groups. Two radiologists assessed pancreatic duct diameter, pancreatic size, pancreatic cyst, pancreatic stone and pancreatic signal intensity on MRCP, T1-weighted and T2-weighted images. Pancreatic signal intensity were also measured on dynamic enhanced MR.ResultsMean values of pancreatic signal intensity ratio on T1WI (rT1) in the pancreas were significantly reduced in patients with moderate and severe CP compared with volunteers.

There was significant difference among four groups (normal, 0.98±0.27; mild, 0.84±0.12; moderate, 0.81±0.16; severe, 0.75±0.24). Mean values of pancreatic signal intensity ratio on T2WI (rT2) in the pancreas were no difference among four groups (normal, 1.28±0.3; mild,1.46±0.44, moderate, 1.46 ±0.55; severe, 1.76 ±0.72). Pancreatic duct diameters were significantly increased in mild, moderate and severe CP groups [mild (5.3±2.4)mm; moderate (6.5 ±3.3)mm; severe (8.1 ±4.1)mm] compared with patients without CP [(2.0±0.6)mm;P﹤0.01]. Severe degree of Cambridge classification was graded as mild in 4 (29%), moderate in 33 (89%), severe in 13 (93%). Pancreatic calcification was graded as mild in 2 (14%), moderate in 11 (30%), severe in 5 (36%). Pancreatic pseudocyst was graded as mild in 0, moderate in 6 (16%), severe in 3 (21.43%). Pancreatic parenchymal atrophy was graded as mild in 4 (29%), moderate in 22 (59%), severe in 10 (71%). They did not vary among CP groups. Parenchymal/arterial phase enhanced ratio (P/A) in the pancreas were significantly increased in patients with mild, moderate and severe CP (mild, 1.10±0.08; moderate, 1.37±0.15; severe, 1.48±0.53) compared with patients without CP (0.88±0.08,P﹤0.05). Significant correlation was present between the severity level of CP and the change of rT1, severe degree of Cambridge classification, the pancreatic duct diameter and P/A (r=0.34, 0.41, 0.62, -0.43;P﹤0.01). ROC analysis showed the presence of pancreatic duct diameters more than 2.5mm, rT1 less than 0.8 and P/A more than 0.8 had a sensitivity and specificity of diagnosing chronic pancreatitis of 94% and 79%, 90% and 48%, 95% and 47% respectively. Combined with the three variables, the specificity of diagnosing chronic pancreatitis can be improved to 95%.ConclusionsT1-weighted, MRCP and dynamic enhanced MRI imaging can accurately evaluate the clinical severity of chronic pancreatitis. MRCP had the highest sensitivity and specificity, followed by T1-weighted and dynamic enhanced MRI imaging.

Pancreatitis,chronic; Magnetic resonance imaging; Dynamic enhanced MRI

10.3760/cma.j.issn.1674-1935.2010.05.001

國(guó)家自然科學(xué)基金(2006BAI02A12)

200433 上海，第二軍醫(yī)大學(xué)長(zhǎng)海醫(yī)院放射科(柏梅、陸建平)，消化內(nèi)科(賴曉偉)

陸建平，Email: cjr.lujianping@vip.163.com