CharacterizingsolidrenalneoplasmswithMRIinadults成人實(shí)性腎腫瘤的MRI特征Introduction

Inordertoaccuratelyclassifyasolidrenalneoplasm,asystematicapproachisrecommended,includingattentiontoclinicalandlaboratorydata,lesionlocationandnumber,lesionsignalintensityandcomposition,enhancementpattern,anddiffusivity.Becausenosinglefeatureinisolationisdefinitivelydiagnosticofaparticulartypeofneoplasm,theindividualcharacteristicsofarenalmassmustthenbecombinedtonarrowthedifferentialdiagnosisorsuggestamostlikelyhistology.為了準(zhǔn)確的鑒別實(shí)性腎腫瘤，在此推薦一種系統(tǒng)的方法，包括臨床和實(shí)驗(yàn)室數(shù)據(jù)、病變位置和數(shù)量、病變信號(hào)強(qiáng)度和成分、強(qiáng)化類(lèi)型及彌散情況。由于沒(méi)有某個(gè)單獨(dú)的特稱(chēng)可用于診斷某一類(lèi)型的腫瘤，因此腎臟腫瘤的多種特征必須結(jié)合起來(lái)縮小鑒別診斷的范圍或者推斷出最為可能的組織學(xué)類(lèi)型。Imagingprotocol成像序列MRimagingisgenerallyperformedwithaphased-arraybodycoilwiththepatientsupine.AtypicalrenalMRIprotocolbeginswithacoronallocalizerusingafastsequencesuchassingle-shotturbo/fastspinecho.Thisprovidesananatomicoverviewoftheabdomenandallowsdepictionofcontourabnormalitiesattherenalpoles.Axialdualgradient-echoT1-weighted(in-phaseandopposed-phase)imagingisperformedwiththelongerechotime(TE)assignedtothein-phaseecho.In-phaseandopposed-phaseimagingallowsdetectionoffatandintracytoplasmiclipid/glycogenorhemosiderinwithinrenalmasses.MRI掃描通常體線圈，病人仰臥位。掃描序列包括首先掃描的冠狀位，提供了腹部的解剖概況并發(fā)現(xiàn)腎臟外形的異常。T1WI（正、反相位）可監(jiān)測(cè)腫塊內(nèi)的脂肪、胞漿內(nèi)的脂類(lèi)/糖原或含鐵血黃素。ThesecomponentscanprovidecluesregardingthebenignormalignantnatureofasolidrenalmassorprovideahintastothesubtypeofRCC.Subtlechangesinsignalintensitybetweenin-andopposed-phaseimagescanoftenbebetterappreciatedwithsubtractionimaging.IfaDixonmethodisused,‘‘fat-only’’and‘‘water-only’’imageswillbeautomaticallygeneratedandcanalsobehelpfulinidentifyingregionsofmicroscopicandmacroscopicfat.這些信息可以提供良惡性腫塊的線索或者腎細(xì)胞癌亞型的提示。正反相位中信號(hào)強(qiáng)度的微小變化可以在減影圖中更好的顯示。如果使用的是“Dixon”成像，“脂像”和“水像”可以自動(dòng)生成，這也有助于確定局部微觀和宏觀的脂肪成分。50歲男性，透明細(xì)胞癌患者，腫瘤內(nèi)含有少量脂肪A軸位T2壓脂序列示右腎可見(jiàn)一信號(hào)混雜腫塊，與腎實(shí)質(zhì)比主要為低信號(hào)；B軸位T1正相位示腫塊內(nèi)可見(jiàn)模糊高信號(hào)影；CT1反相位示腫塊與腎實(shí)質(zhì)呈等信號(hào)難以鑒別，說(shuō)明在正反相位間腫塊內(nèi)存在信號(hào)差異；D減影圖確認(rèn)信號(hào)差異是由于脂肪成分；E增強(qiáng)壓脂T1（動(dòng)脈期）示腫塊與腎實(shí)質(zhì)呈等樣強(qiáng)化。血管平滑肌脂肪瘤和透明細(xì)胞癌都可在考慮之內(nèi)，但病變信號(hào)混雜性加上相對(duì)高的發(fā)病率，透明細(xì)胞癌的可能性更大一些。72歲女性，血管平滑肌脂肪瘤患者A軸位T1反相位示右腎外伸性腫塊，注意箭頭所示細(xì)長(zhǎng)環(huán)形低信號(hào)影（由于脂肪軟組織界面存在），其上為出血；BDixon序列脂像腫塊內(nèi)小范圍脂肪組織；C增強(qiáng)壓脂T1示（腎實(shí)質(zhì)期）腫塊呈蘑菇型伴部分突入腎實(shí)質(zhì)內(nèi)，腫塊前方非增強(qiáng)區(qū)域?yàn)槌鲅?。Fat-suppressedT2-weightedimagesintheaxialplanearehelpfulfordetectingandcharacterizingcysticlesionsandrevealingperinephricedemaandfluidcollections.ComplexcystscontaininghemorrhagicorproteinaceousfluidarevariableinsignalintensityonT2-weightedimagesandcanbeconfusedwithsolidmassesunlesspre-andpost-contrastT1-weightedimagesarereviewed.軸位T2壓脂序列有助于檢測(cè)和定性囊性病變以及顯示腎周水腫和積液。包含出血或蛋白的復(fù)雜成分囊腫在T2WI上信號(hào)復(fù)雜，有時(shí)會(huì)誤認(rèn)為實(shí)性腫塊，此時(shí)需在增強(qiáng)前后的T1WI上鑒別。ThesignalintensityofasolidrenalmassonT2-weightedimagingcanassistinnarrowingthedifferentialdiagnosis;however,whendevelopingarenalMRIprotocol,keepinmindthatgadolinium-basedcontrastagents(GBCAs)canaltertherelativesignalintensityofamasscomparedtonormalrenalparenchymaonaT2-weightedimage.Therefore,itcanbehelpfultoperformatleastoneT2-weightedsequencepriortointravenouscontrastadministration.實(shí)性腫塊的T2WI信號(hào)強(qiáng)度可有助于縮小鑒別診斷。然而，造影劑可以改變腫塊的T2信號(hào)強(qiáng)度，因此，在注射造影劑前應(yīng)至少掃描一個(gè)T2序列。Weincludediffusion-weightedimaging(DWI)withapparentdiffusioncoefficient(ADC)mapsinourrenalmassprotocol,ascertainsolidneoplasms,suchaspapillaryRCC(pRCC),urothelialcarcinoma,andlymphomaoftendemonstraterelativelylowADCvaluescomparedwithnormalrenalparenchyma.Becauserenalparenchymacanappearrelativelybrightonadiffusion-weightedimageperformedwithalowtointermediateb-value,weroutinelyincludeatleastoneacquisitionwithab-valueof800–1000s/mm2toenhancetheconspicuityofpotentialrenalneoplasms.DWI和ADC圖也需要加入腎臟腫塊的掃描序列中，例如乳頭狀腎癌、尿路上皮癌和淋巴瘤與正常腎實(shí)質(zhì)相比常表現(xiàn)為相對(duì)低的ADC值。由于腎實(shí)質(zhì)在低到中b值的DWI上呈較高信號(hào)，因此常規(guī)應(yīng)包括一個(gè)800–1000s/mm2b值的掃描，來(lái)強(qiáng)化潛在腎腫瘤的對(duì)比度。70歲男性，腎門(mén)處淋巴瘤A壓脂T2示腎竇中心可見(jiàn)一較大均勻侵潤(rùn)性低信號(hào)腫塊影；BT1示病變內(nèi)未見(jiàn)脂肪或出血信號(hào)；CDWI（b=1000s/mm2）示腫塊明顯彌散受限呈高信號(hào)；DADC圖腫塊呈低信號(hào)影；E增強(qiáng)壓脂T1（皮髓質(zhì)期）示腫塊輕度均勻強(qiáng)化，箭頭示腫塊包繞腎動(dòng)脈。Multiphasecontrastenhancedimagingcanbeperformedintheaxialorcoronalplane,dependingonpersonalpreference,usinga3-dimensional,fat-suppressedT1-weightedgradientechosequence.EnhancementpatternonmultiphaseMRIisapotentialdiscriminatorbetweenrenalneoplasms.PrecontrastimaginghelpstoidentifyT1hyperintensehemorrhagicorproteinaceousmaterialwithinoraroundarenalmass.IntrinsicallybrightmaterialonaT1-weightedimagecaninterferewithidentifyingcontrastenhancementandmaynecessitatesubtractionimaging.Therefore,carefulbreath-holdinginstructionsarecriticaltoensurethatpre-andpost-contrastenhancedimagesareidenticallyregistered.多期增強(qiáng)可運(yùn)用壓脂T1WI序列行軸位或冠位成像。強(qiáng)化類(lèi)型可用于鑒別不同的腎腫瘤。蒙片有助于確認(rèn)病變內(nèi)或周?chē)某鲅虻鞍壮煞帧1WI上固有的高信號(hào)成分可以對(duì)確認(rèn)強(qiáng)化程度造成干擾，因此也許需要減影圖。認(rèn)真的閉氣指令對(duì)于確保增強(qiáng)前后的圖像定位一致也十分重要。Clinicalandlaboratorydata

臨床和實(shí)驗(yàn)檢查數(shù)據(jù)Clinicaldatacansometimesnarroworalterthedifferentialdiagnosisofarenalmass,orwhencombinedwithimagingfeatures,suggestamostlikelydiagnosis.Avarietyofgeneticsyndromesareassociatedwithrenalneoplasmsofaparticularhistopathology,andpreexistingknowledgeofsuchadisorderalertstheradiologisttoconsiderspecifictypesofrenalneoplasmsinthedifferentialdiagnosis.InadditiontothoselistedinTable1,otherassociationsexistbetweenaclinicalconditionandaspecifictypeofrenalneoplasm.臨床數(shù)據(jù)有助于縮短或者改變一個(gè)腎臟腫塊的鑒別診斷，有時(shí)結(jié)合影像學(xué)特征，可以得出最可能的診斷。多種遺傳綜合征會(huì)與某個(gè)特定病理類(lèi)型的腎腫瘤相關(guān)，如果一個(gè)影像科醫(yī)生事先知道這一障礙會(huì)提醒其在鑒別診斷時(shí)考慮某種類(lèi)型的腫瘤。除了在下表中所列出的，還存在有其他臨床病癥與腫瘤類(lèi)型的相關(guān)性。遺傳癥狀相關(guān)腎臟疾病結(jié)節(jié)性硬化癥血管平滑肌脂肪瘤（75%–80%）囊腫（接近45％）腎細(xì)胞癌（1-4％）上皮樣血管平滑肌脂肪瘤嗜酸細(xì)胞瘤vonHippel–Lindau希佩爾-林道綜合征（VHL綜合征）囊腫（接近60％）透明細(xì)胞癌（24-45％）Birt–Hogg–Dube綜合征混合嗜酸細(xì)胞腫瘤（50%–67%）嫌色細(xì)胞腎癌（23%–34%）透明細(xì)胞癌（(7%–9%）嗜酸細(xì)胞瘤（3%–5%）乳頭狀腎細(xì)胞癌（罕見(jiàn)）遺傳性乳頭狀腎細(xì)胞癌I型乳頭狀腎細(xì)胞癌低級(jí)別Fuhrman分級(jí)遺傳性平滑肌瘤病和腎細(xì)胞癌II型乳頭狀腎細(xì)胞癌(17%–20%)常為孤立/單側(cè)常表現(xiàn)為侵襲性Forexample,thepossibilityofpost-transplantlymphoproliferativedisordershouldbeconsideredinanimmunosuppressedtransplantpatientwitharenalmass,andmetastaticdiseaseshouldbeconsideredinapatientwithmultipleoratypicalappearinglesionsandahistoryofadvancedextrarenalmalignancy.例如，移植后淋巴組織增生的可能性應(yīng)在一個(gè)接受免疫抑制治療的移植患者中考慮，而多發(fā)或非典型表現(xiàn)的病變伴有腎外惡性腫瘤病史者應(yīng)考慮轉(zhuǎn)移性疾病。62歲女性，腎臟轉(zhuǎn)移癌A周?chē)鶷2示左上腎極可見(jiàn)一與腎實(shí)質(zhì)信號(hào)相近的小腫塊影；BDWI高b值（b=500）上顯示更明顯；C壓脂增強(qiáng)T1（皮髓質(zhì)期）示腫塊呈邊緣強(qiáng)化；D壓脂增強(qiáng)T1（腎實(shí)質(zhì)期）示腫塊呈中心強(qiáng)化。由于臨床上懷疑轉(zhuǎn)移性疾病，對(duì)此腫塊進(jìn)行了活檢Occasionally,laboratoryabnormalitiescanpointtoaspecificdiagnosis.Renalcellcarcinomacanbeassociatedwithavarietyofparaneoplasticsyndromes,someofwhichinducelaboratoryabnormalitiessuchaselevatedliverenzymesandpolycythemia.Polycythemiahasalsobeenlinkedtosomecasesofmetanephricadenoma.Somemesenchymaltumors,suchassolitaryfibroustumor,canproduceaninsulin-likegrowthfactorthatcanresultinhypoglycemia.有時(shí)實(shí)驗(yàn)室檢查異常也可以指向某一特定診斷。腎細(xì)胞癌可與各種副腫瘤綜合征有關(guān)，其中的一些可以導(dǎo)致實(shí)驗(yàn)室檢查異常諸如肝酶升高和紅細(xì)胞增多癥。紅細(xì)胞增多癥某些情況下與后腎腺瘤也有關(guān)。一些間質(zhì)腫瘤，如孤立性纖維性腫瘤，可產(chǎn)生胰島素樣生長(zhǎng)因子，可能導(dǎo)致低血糖癥。DiscriminatoryimagingfeaturesonMRI

MRI影像學(xué)特征TheabilitytoaccuratelycharacterizesolidrenalneoplasmswithMRIinpartdependsonone’sabilitytoidentifykeyimagingfeaturesandcombinethosefeaturestogenerateamostlikelydiagnosisorashortlistofdifferentialconsiderations.Inthissection,wereviewMRimagingfeaturesthatcanhelpguidetheinterpretingphys