馮朝燕,李亮,胡道予,夏黎明,陳敏,Jinxing Yu,Steven Eberhard,王良
第21 屆國(guó)際醫(yī)學(xué)磁共振學(xué)會(huì)(International Society for Magnetic Resonance in Medicine,ISMRM)年會(huì)于2013年4月20-26日在美國(guó)鹽湖城舉辦。ISMRM2013前列腺影像診斷方面的研究進(jìn)展和新技術(shù)主要體現(xiàn)在以下幾個(gè)方面。
擴(kuò)散加權(quán)成像(DWI)、擴(kuò)散張量成像(DTI)、擴(kuò)散峰度成像(DKI)及多b值DWI長(zhǎng)久以來一直是放射科醫(yī)師和物理工程師們研究的熱點(diǎn)。如何有效運(yùn)用它們從而更有效地檢出前列腺癌是本次大會(huì)所關(guān)注的。
DWI新技術(shù)提高了對(duì)前列腺癌的診斷敏感性和特異性。Wang等[1]將T2和DWI融合成一種新的成像方法,即通過3種不同的TE獲得DWI數(shù)據(jù),分別計(jì)算ADC 值和T2值,從而有助于正常前列腺組織與癌灶的鑒別。10例經(jīng)病理證實(shí)的前列腺癌患者行DWI(b值分別為0、750和1500s/mm2,TE值分別為47、75、100ms)檢查。結(jié)果顯示,前列腺癌區(qū)和正常組織的ADC值差異具有高度統(tǒng)計(jì)學(xué)意義(P=0.00009、0.00009、0.00006,TE=47、75、100ms)。正常組織和前列腺癌組織的T2值(b=0)差異也有高度統(tǒng)計(jì)學(xué)意義(P=0.003)。故作者認(rèn)為這種成像方法有助于前列腺癌組織的準(zhǔn)確檢出。有研究表明,可變密度螺旋擴(kuò)散加權(quán)成像(VDS-DWI)與傳統(tǒng)的EPI-DWI序列相比,信噪比高,空間分辨力高,圖像無變形,有良好的應(yīng)用前景[2]。Liu等[3]通過分?jǐn)?shù)階微積分(fractional order calculus,F(xiàn)ROC)模型應(yīng)用于前列腺擴(kuò)散成像的研究表明,這種新的模型有助于正常、良性、惡性前列腺組織的檢出,對(duì)前列腺癌的診斷、分期、治療方案的選擇、治療后的監(jiān)測(cè)也有重要意義。Rosenkrantz等[4]將低b值圖像通過數(shù)學(xué)計(jì)算得到高b值圖像,結(jié)果發(fā)現(xiàn),通過cDWI(計(jì)算得出的DWI圖像)改善了圖像質(zhì)量,提高了腫瘤檢出的敏感性。Ueno等[5]也做了相關(guān)研究,得出了同樣的結(jié)論。Korn等[6]的研究顯示,小視野(rFOV)能夠減少磁敏感偽影,有利于前列腺癌的檢出。
與DWI相關(guān)的其它研究也較多。Babourina-Brook等[7]利用EPI和HASTE兩種序列分別對(duì)19例經(jīng)病理證實(shí)的前列腺癌患者行DWI檢查。在腫瘤區(qū)域、外周帶和移行帶測(cè)得ADC值,并繪制ROC 曲線。結(jié)果發(fā)現(xiàn),外周帶和腫瘤組織的ADC值在兩種序列上均有明顯不同;EPI序列對(duì)CZ(中央帶)和Pca(前列腺癌)有良好的鑒別能力,然而假陽性率也隨之提高;兩種序列都能準(zhǔn)確區(qū)分外周帶組織和Pca(曲線下面積>0.8)。Mazaheri等[8]對(duì)比單獨(dú)使用ERC(直腸內(nèi)線圈)與ERC和PAC(相控陣線圈)聯(lián)合應(yīng)用對(duì)于ADC值信噪比的影響。25例經(jīng)病理證實(shí)的前列腺癌患者行3T MRI兩種方式的檢查。結(jié)果發(fā)現(xiàn),ERC-MRI的信噪比明顯高于PAC-ERC(外周帶高9.27倍,移行帶高5.52倍)。說明PAC獲得的低信噪比圖像在高b值的情況下與ERC相比顯著降低了ADC值。
Tan等[9]將PV(MR前列腺體積)和ADC指標(biāo)加入D′Amico 分級(jí)以更好的預(yù)測(cè)術(shù)后病理結(jié)果。251 例患者分為兩組,低危組(GS=6,PSA≤10,臨床分期T 1a-c)98 例,高危組(GS≥7,PSA>10,臨床分期≥T 2a)153例。術(shù)后病理分期低危(pT2,GS=6,手術(shù)切緣陰性),高危(GS≥7,≥pT3,手術(shù)切緣陽性)。結(jié)果發(fā)現(xiàn),ADC值和MR 前列腺體積與D′Amico高危組(R=0.18,P=0.026)和病理高危組(Spearman’s Rho=r=0.21,P=0.005)呈正相關(guān)。ROC 曲線下面積分別為0.68(D′Amico)、0.80(D′Amico和ADC)和0.84(D′Amico和ADC 以及PV)。他們認(rèn)為,PV、ADC與D′Amico分級(jí)聯(lián)合應(yīng)用能更好的的預(yù)測(cè)低分化腫瘤(Gleason≥7)。Bains等[10]對(duì)DWI檢出前列腺腫瘤可靠性進(jìn)行研究。111例患者(原發(fā)性前列腺癌78例,膀胱癌18例,前列腺癌合并膀胱癌15例),由3位放射科醫(yī)師評(píng)估腫瘤的生物侵襲性??傮w上,DWI檢出前列腺腫瘤的敏感度和陽性預(yù)測(cè)值:觀察者A 為0.91和0.91,觀察者B為0.88和0.93,觀察者C為0.90和0.94);低分化腫瘤的敏感度和陽性預(yù)測(cè)值:A 為0.9 和1.00,B 為0.95 和1.00,C 為0.98 和1.00。DWI對(duì)低分化前列腺腫瘤的檢出,假陽性率為0,假陰性率≤5%;對(duì)高分化腫瘤檢出的假陽性率與前列腺增生、前列腺上皮內(nèi)腫瘤和前列腺炎等有關(guān)。
Plata等[11]研究熱消融對(duì)前列腺組織ADC 值的影響及臨床意義。高強(qiáng)度超聲波(HIE)聚焦犬的前列腺,并通過溫度傳感器和MRI測(cè)溫序列質(zhì)子共振頻率位移測(cè)量(proton resonant frequency,PRF)質(zhì)子共振頻率位移測(cè)量)和 DWI(b1000s/mm2)=序列,后處理得到溫度和ADC 值隨時(shí)間變化的曲線圖,并可通過溫度值得到預(yù)測(cè)的ADC 值。結(jié)果發(fā)現(xiàn),實(shí)測(cè)ADC值總是低于預(yù)測(cè)的ADC值,說明組織失活可引起ADC值的下降。不同的成像設(shè)備、不同的b值,絕對(duì)ADC 值會(huì)有很大差異。Busse等[12]的研究表明,不同情況下標(biāo)準(zhǔn)ADC 值為前列腺癌擴(kuò)散成像定量分析及比較提供了可能。Panagiotaki等[13]比較了單指數(shù)模型和多指數(shù)模型在前列腺組織中的應(yīng)用,結(jié)果表明三指數(shù)模型的應(yīng)用價(jià)值最高。Agarwal等[14]比較了高b值(b=1000和2000s/mm2)與低b值(b=0、188、350、563和750s/mm2)DWI對(duì)前列腺癌分期的影響。高b值DWI更容易檢出前列腺組織邊緣的腫瘤組織。研究顯示經(jīng)直腸超聲引導(dǎo)下(TRUS)前列腺穿刺后出血T1WI、T2WI信號(hào)及ADC 值的變化。發(fā)現(xiàn)出血信號(hào)改變可以持續(xù)6 個(gè)月,而ADC 值不受影響。
Takahashi等[16]比較常規(guī)DTI與小視野DTI顯示前列腺周圍神經(jīng)血管束(NVB)的情況。結(jié)果發(fā)現(xiàn),后者能夠更好的顯示細(xì)節(jié),為臨床前列腺根治性切除術(shù)患者保留神經(jīng)血管束提供了可能性。Lawrence等[17]研究DKI(擴(kuò)散峰度成像)對(duì)前列腺癌的診斷價(jià)值,關(guān)于b值和噪聲補(bǔ)償對(duì)定量參數(shù)的影響以及短期可重復(fù)性也進(jìn)行相關(guān)分析。18例經(jīng)穿刺活檢證實(shí)前列腺癌并擬行前列腺切除術(shù)的患者納入研究,接受T2WI DTI檢查(b值0、150、600、1050、1500和2000s/mm)。其中10例患者在相同的參數(shù)下重復(fù)做了檢查。使用4種不同的方法[標(biāo)準(zhǔn),低b值(b=0),高b值(b=1500)和無噪聲補(bǔ)償組]計(jì)算Dapp(彌散系數(shù))和Kapp(彌散峰值);變異系數(shù)(CV)評(píng)估可重復(fù)性。結(jié)果發(fā)現(xiàn)無論是外周帶還是移行帶,腫瘤組織和相對(duì)應(yīng)的正常組織的Dapp和Kapp值差異具有顯著性意義,同時(shí)具有良好的短期重復(fù)性(CV-Dapp<7.5%,CV-Kapp<15%)。Bourne等[18]對(duì)2個(gè)根治性前列腺切除的標(biāo)本行9.4T MRI檢查,比較前列腺組織的DTI和DKI。結(jié)果發(fā)現(xiàn),前列腺包膜和纖維肌質(zhì)層在單指數(shù)模型DTI上各向異性(FA)值明顯高于外周帶及中央帶。DK-AV(峰值擴(kuò)散系數(shù)-平均峰度)與DTImono-MD(單指數(shù)擴(kuò)散張量-平均擴(kuò)散系數(shù))相近,但更能體現(xiàn)組織的微觀結(jié)構(gòu),CVk(峰值變異系數(shù))與FA 圖具有明顯的相關(guān)性。DKI與DTI相比,能更清楚地顯示組織的微觀結(jié)構(gòu)并且變異程度較小。
Cai等[19]運(yùn)用單指數(shù)模型和雙指數(shù)模型鑒別前列腺癌和慢性前列腺炎。19例磁共振檢查后行經(jīng)直腸超聲穿刺的患者納入研究。結(jié)果發(fā)現(xiàn)單指數(shù)模型中,灌注分?jǐn)?shù)f在前列腺癌和慢性前列腺炎中差異無統(tǒng)計(jì)學(xué)意義。運(yùn)用IVIM,慢性前列腺炎與前列腺癌相比具有高的擴(kuò)散特性,與正常外周帶相比具有明顯高灌注和低的擴(kuò)散特性。IVIM 將有助于前列腺病變的鑒別診斷。Kuru等[20]搜集臨床確診的27例前列腺癌患者行b=0、50、100、150、200、250 和800s/mm2共7 組b值的DWI檢查。根據(jù)IVIM 的雙指數(shù)模型用兩種方法計(jì)算f和D 值。結(jié)果發(fā)現(xiàn),灌注分?jǐn)?shù)f均很高,擴(kuò)散分?jǐn)?shù)D 能夠有效地區(qū)分癌組織與健康組織。
Jafar等[21]對(duì)有明顯前列腺癌家族史的51 例患者進(jìn)行DWI掃描并測(cè)得ADC 值。風(fēng)險(xiǎn)評(píng)分是基于對(duì)24個(gè)單核苷酸的分析。40 例患者接受了單核苷酸分析評(píng)分,波動(dòng)范圍0.29~4.89。結(jié)果發(fā)現(xiàn)ADC 值和風(fēng)險(xiǎn)評(píng)分的相關(guān)性無統(tǒng)計(jì)學(xué)意義。因此,還需要進(jìn)一步研究能否為臨床確診前列腺癌提供補(bǔ)充信息。Jafar等[22]對(duì)51 例有前列腺癌陽性家族史的人群行3T 直腸DWI檢查,并定量和定性分析比較。由一位經(jīng)驗(yàn)豐富的放射科醫(yī)師結(jié)合DWI和T2WI,在前列腺6分區(qū)上標(biāo)出陽性或陰性區(qū)域。8周以后,由同一位觀察者結(jié)合T2WI在ADC圖上畫出興趣區(qū)。結(jié)果顯示,在高風(fēng)險(xiǎn)人群中,定性分析DWMRI的敏感度和特異度分別是57.1%和97.8%。由于考慮了前列腺體積、大小、形狀及擴(kuò)散受限位置等因素,定性分析比定量分析更易診斷Gleason評(píng)分低的前列腺癌。
MRI形態(tài)學(xué)與MRS代謝信息相結(jié)合會(huì)提高對(duì)前列腺癌診斷和定位的特異性,以往用于前列腺的主要是1H 譜,本次大會(huì)重點(diǎn)關(guān)注MRS的最新研究進(jìn)展。
Nagarajan等[23]利用NUS EP-JRESI新序列進(jìn)行采集,壓縮感知技術(shù)進(jìn)行重建后處理來研究前列腺癌組織的生物化學(xué)變化。包括11名前列腺癌患者。結(jié)果顯示NUS EP-JRESI(非均勻采樣回波平面磁共振波譜成像)波譜技術(shù)可以分辨出10種代謝物如檸檬酸鹽(Cit)、肌酸(Cr)、膽 堿(Cho)、精胺(Spm)、肌醇(mI)、鯊肌醇(Scy)、?;撬幔═au)、谷氨酸鹽(Glu)和谷氨酰胺(Gln)。而傳統(tǒng)的MRS由于TE 較長(zhǎng)等原因,只能區(qū)分3種代謝產(chǎn)物。Lagemaat等[24]利用超高場(chǎng)強(qiáng)7.0T MRI31P MRS技術(shù)對(duì)前列腺癌進(jìn)行研究,12例臨床懷疑或已經(jīng)證實(shí)的前列腺癌,運(yùn)用31P TX/RX 直腸線圈對(duì)外周帶和移行帶的可疑癌灶進(jìn)行波譜分析。腫瘤組織PE(乙醇胺)/γ ATP、PE/tPLM(乙醇胺、磷脂膽堿、甘油磷酸膽堿等)和PI/r(γ-三磷酸腺苷)ATP明顯低于正常的外周帶和移行帶。前列腺癌和正常組織含P的代謝產(chǎn)物明顯不同,此研究有助于前列腺良惡性病變的鑒別診斷。Lagemaat等[25]利用7T MR31P-MRS 技術(shù)做了T1弛豫時(shí)間和NOS(核極化效應(yīng))的定量分析,發(fā)現(xiàn)前列腺T1弛豫時(shí)間較其它組織長(zhǎng)。
Keshari等[26]利用超極化13C 標(biāo)記的乳酸作為人前列腺癌組織切片的生物標(biāo)記物進(jìn)行MRS研究。分別運(yùn)用體外細(xì)胞培養(yǎng)人前列腺癌細(xì)胞系(PC-3,VCaP和原發(fā)性前列腺癌細(xì)胞),前列腺癌組織切片(TSC)以及穿刺活檢標(biāo)本三種方式。結(jié)果發(fā)現(xiàn),TSC 和活檢穿刺組織各代謝產(chǎn)物的峰高相似,而PC-3、VCaP原發(fā)代謝物差異卻十分明顯。說明TSC 能反映組織結(jié)構(gòu)以及體內(nèi)的代謝變化。因此,使用這個(gè)模型,可以用超極化13C標(biāo)記的丙酮酸探測(cè)重組葡萄糖、標(biāo)記乳酸來探索前列腺癌的代謝變化。Billingsley等[27]利用超極化的13C-KIC(超極化13C標(biāo)記的酮異己酸)作為分子探針研究前列腺癌支鏈氨基酸的代謝。體外實(shí)驗(yàn),四種不同的人類前列腺癌細(xì)胞系(PC-3,DU-145,LNCaP和LAPC-4)和TRAMP(轉(zhuǎn)基因前列腺癌小鼠模型)小鼠組織提取物進(jìn)行了質(zhì)譜分析。體內(nèi)實(shí)驗(yàn),PC-3和PC-3M 移植小鼠3TGE Signa MRI掃描。結(jié)果發(fā)現(xiàn),就支鏈氨基酸代謝而言,TRAMP小鼠并不能模擬人前列腺癌。PC-3移植小鼠癌細(xì)胞BCAT(支鏈氨基酸)活性是體外PC-3細(xì)胞的2.5倍,PC-3和PC-3M移植癌細(xì)胞蛋白水平分別是(3.81±1.27)U/gram,(2.4 7±1.01)U/gram。Sukumar等[28]的研究結(jié)果表明,LDH-A(乳酸脫氫酶A)基因敲除后1 周,TRAMP小鼠腫瘤體積增加13%(0.85cc到96cc),ADC值下降30%,超極化13C Lac/Pyr(乳酸鹽/丙酮酸鹽)的值下降約25%。因此,LDH-A 基因表達(dá)產(chǎn)物的變化可以通過HP13C MRI探測(cè)到。Steinseifer等[29]研究顯示,在前列腺M(fèi)RS序列semi-LASER中施加GOIA-Wurst(16,4)脈沖,能夠減少射頻能量吸收率(SAR)。
Kobus等[33]提出一種新的假設(shè),即前列腺癌枸櫞酸鹽水平的下降與腫瘤生長(zhǎng)引起腺腔體積縮小有關(guān),并驗(yàn)證了這一假設(shè)。55例患者術(shù)前均行T2WI和MRS檢查。HE 切片采用彩色圖像分割技術(shù)分別測(cè)得腺腔、基質(zhì)及胞核的百分比。在相對(duì)應(yīng)到的T2WI圖像上分別計(jì)算各ROI的Cho+Spm(精胺)+Cr/Cit比值。結(jié)果發(fā)現(xiàn),Cho+Spm+Cr/Cit比值與腺腔面積和胞核面積有關(guān),符合線性混合模型(y=0.182+0.298)。7T MRI可以將精胺與膽堿和肌酸代謝產(chǎn)物區(qū)分開,Luttje等[34]的研究結(jié)果表明,腫瘤組織與健康組織的(Cho+Cr)/Cit值差異不明顯,(Cho+Pa+Cr)/Cit的值差異十分顯著。這說明,精胺與腫瘤組織的侵襲性有關(guān)。Kailavasan等[35]利用MRS研究人前列腺癌細(xì)胞系列LNCaP(不易轉(zhuǎn)移)和LNCaP-LN3(易轉(zhuǎn)移)代謝產(chǎn)物的不同及添加DCA(丙酮酸脫氫酶激酶抑制物)后代謝產(chǎn)物的變化。實(shí)驗(yàn)以大鼠P22肉瘤細(xì)胞作為對(duì)照組。結(jié)果發(fā)現(xiàn),LNCaP-LN3和大鼠p22細(xì)胞系列代謝產(chǎn)物無LDH-B,而LNCaP表達(dá)LDH-A 和LDH-B。MRS檢測(cè)到乳酸、脂肪酸、丙氨酸、谷氨酰胺、膽堿和肌酸共6種代謝產(chǎn)物。1h時(shí)LNCaPLN3乳酸濃度中位數(shù)(19500μmol/108)明顯高于大鼠P22(12000μmol/108)和LNCaP(864μmol/108)。DCA(丙酮酸脫氫酶激酶抑制物)治療后,三種細(xì)胞系列Cho濃度都明顯降低。他們認(rèn)為,乳酸含量的增加與腫瘤進(jìn)展有關(guān),DCA 影響細(xì)胞的代謝。
Otto等[36]聯(lián)合應(yīng)用MRS和DWI評(píng)估前列腺腫瘤的侵襲性。39例患者接受直腸線圈3T MR DWI(b值50、500、800和1500s/mm2)及PRESS(點(diǎn)分辨自旋回波波譜)序列圖像采集。病理切片Gleason評(píng)分分3 個(gè)等級(jí)(高分化、中分化、低分化,GS分別≤6、7 和≥8)。分別測(cè)得圖像的ADC、nADC(標(biāo)準(zhǔn)ADC)、CC(膽堿/枸櫞酸鹽)、CCC(膽堿+肌酸/枸櫞酸鹽)與Gleason評(píng)分的相關(guān)性及繪制ROC 曲線。結(jié)果發(fā)現(xiàn)nADC 與ADC,CC和CCC相比有較高的鑒別能力(AUC:0.88vs 0.72,0.72vs 0.78)。以nADC<0.46 和CCC>1.3為界值點(diǎn),診斷敏感度、特異度和符合率分別為79%、72%和85%。他們得出結(jié)論,nADC 與CCC 聯(lián)合應(yīng)用有助于評(píng)估腫瘤的侵襲性。Shukla-Dave等[37]運(yùn)用1H-MRS和18F-FDG-PET掃描研究前列腺癌枸櫞酸鹽的代謝和葡萄糖的消耗。共22例患者,其中11例成像之前接受過外放射治療。使用PRESS體素激發(fā)和水脂抑制。測(cè)得3D 每個(gè)體素的膽堿+多胺+肌酸/枸櫞酸鹽比值。測(cè)量前列腺不同放射性濃聚組織SUV(PET 的標(biāo)準(zhǔn)攝取)值,并與前列腺病理組織相對(duì)照,22個(gè)腫瘤病灶中21個(gè)被1H-MRSI準(zhǔn)確描述,而只有3個(gè)病灶發(fā)現(xiàn)有18F-FDG 的攝取,這說明18F-FDG-PET主要應(yīng)用于轉(zhuǎn)移病灶的檢出和治療評(píng)價(jià)。腫瘤低氧狀態(tài)和PH 值與腫瘤的侵襲性、治療效果和預(yù)后有關(guān)[38]。該實(shí)驗(yàn)運(yùn)用1H 和31P MRS和DCE-MRI評(píng)估3種前列腺癌模型的腫瘤PH、代謝和血管。用3-APP(3-氨基丙烷磷酸)測(cè)定腫瘤細(xì)胞外pH 值(PHe),而腫瘤缺氧運(yùn)用DCE-MRI的數(shù)據(jù)進(jìn)行評(píng)估。結(jié)果發(fā)現(xiàn),細(xì)胞內(nèi)的PH 值不受3-APP 注入量的影響,PC-3-CA-IX腫瘤細(xì)胞的細(xì)胞外PH 值比LNCaP 低一些。體內(nèi)增強(qiáng)數(shù)據(jù)顯示,細(xì)胞外壞境偏酸可能與腫瘤的乏氧狀態(tài)有關(guān)。
藥代動(dòng)力學(xué)的的測(cè)量方法和各種參數(shù)的定性分析、以及Ktrans(轉(zhuǎn)運(yùn)常數(shù))、Kep(速率常數(shù))等反映藥代動(dòng)力學(xué)參數(shù)特征的定量分析,ASL技術(shù)在大會(huì)上做了相關(guān)報(bào)道。
Mischi等[39]發(fā)現(xiàn)一種新的DCE-MRI模型,即通過評(píng)估血管內(nèi)對(duì)比劑動(dòng)力學(xué)來研究微血管結(jié)構(gòu)。結(jié)果表明,此模型參數(shù)κKep的敏感度、特異度、曲線下面積分別是82.6%、89.5%、91%和58.0%、80.9%、72%。這種新方法為前列腺癌的定位和富血管腫瘤病變的研究提供了新思路。Dikaios 等[40]對(duì)DCE-MRI的定量參數(shù)Ktrans、Kep、SoE(初始上升梯度)、DCE nSI(標(biāo)準(zhǔn)信號(hào)強(qiáng)度)、ME(最大信號(hào)強(qiáng)度)和Etype(曲線類型)建立Logistic回歸方程,并對(duì)診斷效能做ROC曲線分析。比較前列腺正常組織和腫瘤組織外周帶移行帶各參數(shù)的差異。研究表明,外周帶或移行帶腫瘤組織各參數(shù)無明顯差異,非癌組織參數(shù)有明顯差異。大部分參數(shù)都有助于外周帶癌灶的檢出,而移行帶癌灶的檢出卻僅限于ME。此項(xiàng)研究所提供的數(shù)據(jù)有助于臨床上對(duì)前列腺癌的檢出。
磁共振動(dòng)態(tài)增強(qiáng)定量分析可用于前列腺骨轉(zhuǎn)移的檢測(cè)。Du等[41]的研究結(jié)果表明,骨轉(zhuǎn)移病變動(dòng)力學(xué)參數(shù)高于正常骨組織[Ktrans(0.101±0.029)/min vs(0.017±0.009)/min,Ve(0.595±0.117)vs(0.411±0.065)],41處轉(zhuǎn)移病灶的平均面積Ktrans圖(929.93mm2)大于DWI圖(425.32mm2)。Ktrans圖發(fā)現(xiàn)轉(zhuǎn)移病灶的敏感性很高,RLVC(局部體素聚集模型)為早期骨轉(zhuǎn)移病變提供了更多的診斷信息。Iltis等[42]在研究前列腺癌小鼠模型MR 納米粒子預(yù)處理的效果。十只雄性裸鼠后肢注入LNCaP細(xì)胞,4~5周后將小鼠分為兩組,一組接受靜脈注射CYT-609(納米粒子處理的抗腫瘤藥)后4h進(jìn)行動(dòng)態(tài)增強(qiáng)掃描,對(duì)照組不接受。無論是腫瘤組織還是肌肉組織,CYT(實(shí)驗(yàn)組)的信號(hào)強(qiáng)度總是大于CTRL(對(duì)照組)。納米粒子預(yù)處理可以提高增強(qiáng)效果。
Chang等[43]的結(jié)果表明,使用Bloch-Siegert(限制性頻譜成像)方法來校正B1的不均勻性,可以改善前列腺T1定量圖像和DCE-MRI定量參數(shù)如Ktrans圖像等,從而有助于前列腺病變的檢出。Cai等[44]比較了前列腺磁共振脈沖動(dòng)脈自旋標(biāo)記(PASL-MRI)與DCE-MRI對(duì)前列腺癌骨轉(zhuǎn)移的成像效果。結(jié)果發(fā)現(xiàn),在不同的TI時(shí)間,ASL-MRI在瘤骨區(qū)域測(cè)得的BF明顯高于非腫瘤骨區(qū)域。BF(血流量)與Ktrans和kep 呈正相關(guān)。此研究表明ASL能夠探測(cè)前列腺骨轉(zhuǎn)移,因?yàn)檗D(zhuǎn)移瘤多血供(產(chǎn)生大量的新生微血管)的特性與DCE-MRI 得到的Ktrans、kep和Ve有關(guān)。對(duì)于由于腎功能不良或者其它原因不能進(jìn)行DCE-MRI檢查的患者可借助磁共振ASL 檢查明確診斷。Li等[45]也做了利用VS-ASL 進(jìn)行前列腺灌注成像的研究。
隨著MRI硬件系統(tǒng)、成像序列和軟件系統(tǒng)的提高及醫(yī)學(xué)工程學(xué)、計(jì)算機(jī)科學(xué)和分子生物學(xué)的發(fā)展,新的成像序列及診斷方法應(yīng)運(yùn)而生。
Karow 等[46]評(píng)估RSI-CM 技術(shù)在高級(jí)別前列腺腫瘤檢出的價(jià)值,從定性和定量?jī)蓚€(gè)方面分析比較。5例術(shù)前患者接受RSI-CM、DWI(b值為100、400、800s/mm2)和DCE 檢查并最終行根治性前列腺切除。結(jié)果發(fā)現(xiàn),RCI-CM 圖與Ktrans圖、常規(guī)ADC圖、高b值A(chǔ)DC 相比,能更明顯的顯示病灶。Z-score圖顯示RSI-CM(-3分)明顯高于高b值A(chǔ)DC 圖(<0.5分),ROC示曲線下面積分別為0.97和0.64.RSI-CM 技術(shù)能夠更好的檢出高級(jí)別前列腺腫瘤。Kim 等[47]研究新的生物成像方式即MREIT(磁共振電阻抗成像)。5只畢格犬用于成像實(shí)驗(yàn),結(jié)果得到MRI幅度圖像、重建后的導(dǎo)電圖和顏色編碼圖像。前列腺、骶骨、直腸、肌肉等組織在幅度圖上可以清晰分辨,電導(dǎo)率圖像清楚的顯示了前列腺外周帶和中央帶的分界,這將有助于前列腺良性增生、前列腺癌等疾病的鑒別診斷。Basharat等[48]在11.7T 高場(chǎng)磁共振研究了精胺和枸櫞酸鹽生理濃度和PH 值的化學(xué)交換飽和轉(zhuǎn)移效應(yīng)。實(shí)驗(yàn)分為3部分,溫度控制在310K,分別在PH 值6、7、8的條件下測(cè)量10mmol/L精胺溶液的化學(xué)交換飽和轉(zhuǎn)移效應(yīng)。PH 值范圍4~8,測(cè)量10mmol/L精胺和100mM 枸櫞酸鹽的CEST(化學(xué)交換飽和轉(zhuǎn)移)效應(yīng)。實(shí)驗(yàn)發(fā)現(xiàn)PH=6、頻率是2.4ppm 的條件下,CEST 的不對(duì)稱性是6.1%。把溫度從310K 降到300K,研究精胺的化學(xué)交換速率,結(jié)果發(fā)現(xiàn)CEST 不對(duì)稱性從41.0%提高到54.2%(pH=6.0,δ=+3.0ppm)。通過研究體外不同濃度精胺和枸櫞酸鹽的CEST(化學(xué)交換飽和轉(zhuǎn)移)效應(yīng),進(jìn)而得到體內(nèi)這兩種代謝物的濃度,從而為前列腺疾病的診斷提供依據(jù)。
Bomers等[49]研究MRI引導(dǎo)下的經(jīng)直腸激光消融治療前列腺癌同時(shí)實(shí)時(shí)監(jiān)測(cè)溫度。包括15例臨床懷疑前列腺癌或復(fù)發(fā)患者,接受3T MRI檢查,穿刺針導(dǎo)航定位,Planning@IFE技術(shù)監(jiān)測(cè)溫度,TMAP(三垂直平面溫度成像)@IFE 觀察溫度的穩(wěn)定性。結(jié)果發(fā)現(xiàn),整個(gè)工作流程對(duì)所有患者都是可行的,B0漂移校正情況下,前列腺溫度37.0℃(范圍34.8℃~38.0℃),偏離基線溫度中位數(shù)0.8℃(范圍0.5℃~2.6℃);無B0漂移校正情況下分別為36.9℃(范圍30.8℃~43.2℃),偏離1.6℃(范圍0.4℃~6.4℃)。他們認(rèn)為MRI引導(dǎo)下的經(jīng)直腸激光消融治療前列腺癌是可行的。Fennessy等[50]研究多參數(shù)MRI序列和前列腺癌病理分期結(jié)果的空間相關(guān)性。搜集27例臨床懷疑或已確診的前列腺癌患者,利用直腸內(nèi)線圈3.0T MR 機(jī),所有患者均行T2WI、HTR-DCE、DWI檢查,隨后行TRUS或MR穿刺活檢或前列腺根治性切除術(shù)。排除病理報(bào)告結(jié)果不充分、活檢陰性或圖像質(zhì)量不好等,共計(jì)14 例納入該實(shí)驗(yàn)研究。共勾畫出14處腫瘤病灶和4處正常組織,與病理相對(duì)比,以此顯示多參數(shù)磁共振序列圖像與病理組織的相關(guān)性。
Zhao等[51]比較了前列腺上皮細(xì)胞,基質(zhì)和腺腔體積在擴(kuò)散加權(quán)縮微圖像和組織學(xué)上的差異。標(biāo)本接受16.4T MRI成像,分別在DWI圖像和光鏡下分割出上皮組織,基質(zhì)及腺腔結(jié)構(gòu)。結(jié)果發(fā)現(xiàn),DWI分割圖像與體素?cái)U(kuò)散率統(tǒng)計(jì)得到的結(jié)果類似,然而與組織切片測(cè)量圖像相比,DWI測(cè)得的腺腔體積較小。隨著Gleason評(píng)分的增加,上皮細(xì)胞體積增大,基質(zhì)體積變小,解釋了ADC 值下降這一現(xiàn)象。Wang 等[52]運(yùn)用Levenberg-Marquardt神經(jīng)網(wǎng)絡(luò)算法研究前列腺癌的早期發(fā)現(xiàn),包括512例臨床懷疑前列腺癌患者。第一階段,所有患者tPSA(總前列腺特異抗原)、f/tPSA(游離前列腺抗原/總前列腺抗原)、年齡,MRI接受人造神經(jīng)元網(wǎng)絡(luò)的訓(xùn)練和實(shí)驗(yàn)?zāi)J剑坏诙A段,隨機(jī)抽取360例患者資料進(jìn)行訓(xùn)練,其余患者數(shù)據(jù)進(jìn)行測(cè)試。結(jié)果第一階段臨床、MRI以及臨床結(jié)合MRI指標(biāo)ROC 曲線下面積分別為0.81±0.02、0.85±0.02和0.91±0.01;第二階段分別為0.76、0.84和0.86。說明臨床指標(biāo)結(jié)合MRI對(duì)前列腺癌早期診斷的價(jià)值最大,其敏感度、特異度和符合率分別為78%、84%、81%。線圈的設(shè)計(jì)及應(yīng)用[53-58]、前 列 腺癌定位[59-60]、前列腺穿刺活檢[61-64]、放療[65-67]、激光治療[68]、冰凍消融治療[69]、有效監(jiān)督[70]也是本次大會(huì)研究的熱點(diǎn)。
綜上所述,前列腺癌是中老年男性最常見的泌尿系統(tǒng)腫瘤,居發(fā)達(dá)國(guó)家惡性腫瘤之首,國(guó)內(nèi)發(fā)病率也逐年提高。因此前列腺癌的早期檢測(cè)和早期診斷至關(guān)重要。ISMRM2013是一次學(xué)術(shù)盛宴,為前列腺癌的早期檢出、診斷和治療提供新的思路。
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