鄧 彤 程曉光 吳志剛 張艷偉
(北京積水潭醫(yī)院放射科,北京市 100035,E-mail:dengtong016@sina.com)
論著·臨床研究
MRI同反相位成像、表觀擴(kuò)散系數(shù)以及彌散加權(quán)成像序列在椎體良惡性疾病鑒別中的價值
鄧 彤 程曉光 吳志剛 張艷偉
(北京積水潭醫(yī)院放射科,北京市 100035,E-mail:dengtong016@sina.com)
目的 探討MRI的同反相位成像(IP/OP)、表觀擴(kuò)散系數(shù)(ADC)以及彌散加權(quán)成像(DWI)序列在鑒別椎體良惡性疾病中的應(yīng)用價值。方法 選擇惡性腫瘤椎體壓縮骨折患者80例作為惡性組,良性疾病導(dǎo)致的椎體壓縮性骨折80例作為良性組,均行MRI常規(guī)序列及DWI掃描,并采用雙回波技術(shù)在3D快速擾相梯度回波序列中采集IP/OP圖像;分析良惡性病變病例的DWI信號特點,定量測定兩組椎體的ADC值、信號強(qiáng)度比(SIR)值和信號衰減程度(SAR)值。結(jié)果 良性及惡性組病灶DWI序列均可表現(xiàn)為高、等、低或混雜信號,兩組DWI信號改變情況比較,差異無統(tǒng)計學(xué)意義(P>0.05);良性組ADC值為(2.24±0.31)×10-3mm2/s,高于惡性組ADC值的(1.72±0.36)×10-3mm2/s(P<0.05);良性組SIR值為0.58±0.15,高于的惡性組的1.26±0.16(P<0.05),良性組SAR值為0.45±0.36,低于惡性組的0.15±0.07(P<0.05)。結(jié)論 DWI信號不能準(zhǔn)確鑒別椎體良惡性病變,而ADC值和SIR值、SAR值具有重要的鑒別診斷價值。
脊柱疾??;良性;惡性;磁共振成像;彌散加權(quán)成像;表觀擴(kuò)散系數(shù);同反相位成像
肺癌及乳腺癌最常見的骨轉(zhuǎn)移部位是脊柱,大約占全身骨轉(zhuǎn)移的10%,對于椎體惡性疾病而言,早期診斷及發(fā)現(xiàn)病變對患者預(yù)后有著至關(guān)重要的作用[1-4]。CT及MRI常用于單一椎體微小病變的診斷,并且已經(jīng)在各中大型醫(yī)院中廣泛應(yīng)用[5]。椎體惡性轉(zhuǎn)移導(dǎo)致的椎體壓縮性骨折有時很難與骨質(zhì)疏松壓縮性骨折鑒別。原發(fā)性惡性腫瘤性疾病中,約有1/3的患者為良性疾病導(dǎo)致的骨折[6-7]。而傳統(tǒng)的MRI T1加權(quán)像(T1-weighted image,T1WI)及T2加權(quán)像(T2-weighted image,T2WI)序列的形態(tài)信號表現(xiàn)缺乏特異性,這給惡性疾病的診斷及預(yù)后判斷帶來困難。因此尋求較為準(zhǔn)確地診斷椎體良惡性病變的方法有重要臨床意義,近年來彌散加權(quán)成像(diffusion-weighted imaging,DWI)、同反相位成像以及表觀擴(kuò)散系數(shù)在脊柱病變診斷上的應(yīng)用使椎體病變的良惡性鑒別成為可能[8-10]。為此我們通過在椎體良惡性疾病患者中分析其MRI 圖像的DWI信號、同反相位成像以及表觀擴(kuò)散系數(shù),評價三者的應(yīng)用價值,為臨床診斷提供參考。
1.1 臨床資料 選擇于2013年1月至2015年8月在我院經(jīng)病理診斷或隨訪確認(rèn)為惡性腫瘤椎體壓縮骨折患者80例共130個椎體(惡性組),良性疾病導(dǎo)致的椎體壓縮性骨折80例共125個椎體(良性組)。其中,男性78例,女性82例,年齡(54.1±1.8)歲。惡性組中,肺癌導(dǎo)致的骨轉(zhuǎn)移32例,乳腺癌導(dǎo)致的骨轉(zhuǎn)移38例,其他腫瘤10例。良性組中,骨質(zhì)疏松52例,外傷62例,血管瘤6例。兩組患者的性別、年齡及發(fā)生部位比較,差異無統(tǒng)計學(xué)意義(P>0.05),見表1。
表1 兩組患者的臨床資料比較(n,%)
1.2 檢查方法 所有患者均采用Philips Achieva 1.5T超導(dǎo)型全身MRI掃描儀(飛利浦公司)進(jìn)行檢查,檢查內(nèi)容包括自旋回波T1加權(quán)像(spin-echo T2-weighted image,SE-T1WI)序列、屏氣快速自旋回波(turbo spin-echo,TSE)、 T2WI和短恢復(fù)時間反轉(zhuǎn)恢復(fù)法(short T1inversion recovery,STIR),對患者進(jìn)行掃描時采用脊柱線圈進(jìn)行掃描,其中矢狀面掃描包括脊柱和周圍軟組織,層厚為4 mm,層間距為0.4 mm,TSE T1WI的重復(fù)時間(repetition time,TR)為475ms、回波時間(echo time,TE)為7.8 ms,TSE T2WI的TR為3 000 ms、TE為102 ms,TSE T2WI脂肪抑制和軸面TSE T2WI掃描,其中激勵次數(shù)(number of excitation,NEX)選取為3,矩陣為320×160。應(yīng)用自旋回波(spin echo,SE)-回波平面成像(echo planar imaging,EPI)-DWI法進(jìn)行擴(kuò)散加權(quán)成像,TE采取最小值,TR采用5 000 ms,NEX選取為4,矩陣為128×128。采用矢狀面掃描,掃描的參數(shù)為TE 90 ms,TR 1 288 ms,矩陣(99~128)×256 mm,視野260 mm,層厚4 mm,層間距1.0 mm。選擇雙回波技術(shù)在3D快速擾相梯度回波(three-dimensional fast spoiled gradient-echo,3DFSPGR)序列中采集MR同/反相位(in-phase and opposed-phase,IP/OP)圖像[11]。
1.3 測量方法以及圖像分析 由2名經(jīng)驗豐富的影像診斷醫(yī)師運(yùn)用工作站自帶的AW4.2 Functool 2軟件,獨立對病變椎體以及正常椎體進(jìn)行同序列、同層面的比較分析,分析的主要內(nèi)容有病變椎體在常規(guī)序列T1WI和T2WI及抑脂像上的信號改變。根據(jù)T1WI和T2WI的影像學(xué)特點確定感興趣區(qū),面積為40 mm2,測定兩組患者的OP、IP信號值、表觀擴(kuò)散系數(shù)(apparent diffusion coefficient,ADC)值,DWI信號改變以低、中、高或混雜進(jìn)行評價,其中OP、IP信號值分別以相對信號強(qiáng)度比(signal intensity ratio,SIR)值及信號衰減程度(signal attenuation ratio,SAR)值表示,獨立測試3次取平均值。
1.4 統(tǒng)計學(xué)分析 采用SPSS 20.0進(jìn)行統(tǒng)計學(xué)分析,計量資料采用(x±s)表示,兩組間比較采用t檢驗,計數(shù)資料比較采用χ2檢驗,以P<0.05為差異有統(tǒng)計學(xué)意義。
2.1 兩組患者DWI信號改變情況 良性組、惡性組均可表現(xiàn)為低信號、等信號、高信號及混雜信號,兩組DWI信號改變比例比較,差異無統(tǒng)計學(xué)意義(χ2=1.067,P=0.785)。見表2。
表2 兩組患者DWI不同信號比例比較(n,%)
2.2 兩組患者ADC值比較 良性組ADC值為(2.24±0.31)×10-3mm2/s,惡性組ADC值為(1.72±0.36)×10-3mm2/s,良性組的ADC值高于惡性組(t=9.789,P<0.001)。2.3 兩組患者SIR值及SAR值的比較 良性組SIR值為0.58±0.15,低于惡性組的1.26±0.16(t=-27.732,P<0.001);良性組SAR值為0.45±0.36,高于惡性組的0.15±0.07(t=7.317,P<0.001)。
本研究中,通過對比分析良性病變和惡性疾病導(dǎo)致的腰椎骨的MRI圖像發(fā)現(xiàn),兩組的DWI信號改變情況比較,差異無統(tǒng)計學(xué)意義(P>0.05),提示DWI信號改變情況并不能為診斷脊柱良惡性病變提供有用的診斷信息,這與Castillo等[12]的研究結(jié)果基本一致。而且Castillo等[12]認(rèn)為采用DWI序列進(jìn)行診斷并不優(yōu)于T1WI序列,但是在診斷轉(zhuǎn)移瘤中優(yōu)于T2WI序列。在良惡性疾病導(dǎo)致的脊柱骨折過程中,患者脊柱均可表現(xiàn)高、低或者混合信號,這可能是造成在發(fā)生骨折后DWI信號變化多端以及應(yīng)用DWI信號很難將良惡性疾病區(qū)分的主要原因[5,13]。另外,Backens[14]認(rèn)為T2效應(yīng)再加上骨折后出血,良性疾病均會表現(xiàn)會高信號影,這可能是DWI信號難以將兩者區(qū)分的另一個原因。李彩霞等[15]對良惡性骨腫瘤疾病的DWI進(jìn)行對比分析后發(fā)現(xiàn),兩者DWI信號無差別,而ADC可鑒別良惡性疾病導(dǎo)致的骨折。而我們通過分析兩組ADC數(shù)值的變化也發(fā)現(xiàn),良性組ADC值為2.24±0.31×10-3mm2/s,惡性組ADC值為1.72±0.36×10-3mm2/s,惡性組患者的ADC值較良性組患者明顯降低(P<0.05),提示ADC數(shù)值的變化可用于鑒別良惡性疾病導(dǎo)致的骨折。水分子布朗運(yùn)動可由DWI反映,而良惡性疾病細(xì)胞外水分?jǐn)U散速度不同,這可能是ADC數(shù)值鑒別良惡性疾病導(dǎo)致的骨折的機(jī)制[16]。另外由于脊柱良性疾病為單純的骨髓水腫,而導(dǎo)致細(xì)胞外水分?jǐn)U散增強(qiáng),而在脊柱惡性疾病中,異常增殖的腫瘤細(xì)胞浸潤會造成細(xì)胞外水分?jǐn)U散受阻,這是良惡性脊柱病變DWI值不同的原因[17-18]。
采用MRI常規(guī)序列對脊柱良惡性疾病進(jìn)行診斷一直以來存在爭議,既往研究顯示,由于T1WI、T2WI及STIR的信號強(qiáng)度不同,可再結(jié)合周圍軟組織情況,可準(zhǔn)確診斷脊柱良惡性疾病[19]。另外,也有研究表明,雖然脊柱轉(zhuǎn)移瘤在T1WI上顯示為低信號,但在T2WI及SITR上信號并無規(guī)律,故不宜作為確診良惡性疾病的標(biāo)準(zhǔn)[11,19]。本研究利用回波IP/OP技術(shù)對兩組患者進(jìn)行檢查后發(fā)現(xiàn),良性組SIR值為0.58±0.15,高于惡性組的1.26±0.16(P<0.05),良性組SAR值為0.45±0.36,低于惡性組的0.15±0.07(P<0.05),提示椎體轉(zhuǎn)移瘤OP的信號相對增高,而IP的信號降低,這可能為臨床應(yīng)用回波IP/OP技術(shù)技術(shù)診斷良惡性腫瘤性疾病提供依據(jù)。這和Thawait等[20]的研究結(jié)果相似,其通過Meta分析發(fā)現(xiàn)表觀系數(shù)和MR反相對良惡性診斷價值較大。
綜上所述,DWI信號不能準(zhǔn)確診斷椎體良惡性病變,而ADC值和SIR值、SAR值具有重要的鑒別診斷價值,這可為臨床診斷椎體良惡性椎體病變提供參考。但是由于本研究納入病例較少,今后需進(jìn)一步開展臨床對照試驗研究,采用兩種不同方法對同一類椎體骨折患者進(jìn)行診斷,并長期隨訪,以觀察檢測方法的診斷準(zhǔn)確性。
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Value of MRI in-phase and opposed-phase,apparent diffusion coefficient and diffusion-weighted imaging in distinguishing benign and malignant spinal lesions
DENGTong,CHENGXiao-Guang,WUZhi-Gang,ZHANGYan-Wei
(DepartmentofRadiology,BeijingJishuitanHospital,Beijing100035,China)
Objective To explore the application value of MRI in-phase and opposed-phase(IP/OP),apparent diffusion coefficient(ADC) and diffusion-weighted imaging(DWI) in distinguishing benign and malignant spinal lesions.Methods A total of 80 patients with vertebral compression fractures caused by malignant tumor were enrolled as malignant group,and 80 patients with vertebral compression fractures caused by benign disease as benign group.The patients in both groups received MRI scanning with routine sequence and DWI.And the double-echo technology was used to obtain IP/OP imaging by three-dimensional fast spoiled gradient-echo.The characteristics of DWI signals were analyzed in the cases of benign and malignant lesions.The ADC,signal intensity ratio(SIR) and signal attenuation ratio (SAR) were quantitatively determined.Results High,equal,low or mixed signals of DWI sequences were observed in both of benign group and malignant group.No significant difference in the signal change of DWI was observed between two groups(P>0.05).The ADC in the benign group was (2.24±0.31)×10-3mm2/s,and was higher than that in the malignant group(1.72±0.36)×10-3mm2/s(P<0.05).The SIR in the benign group was 0.58±0.15,and was higher than that in the malignant group(1.26±0.16)(P<0.05).The SAR in the benign group was 0.45±0.36,and was lower than that in the malignant group(0.15±0.07)(P<0.05).Conclusion DWI signal can not be used to distinguish benign and malignant spinal lesions of vertebral bodies accurately.But ADC,SIR and SAR are valuable in the differential diagnosis of benign and malignant lesions.
Spinal lesions,Benign,Malignant,Magnetic resonance imaging,Diffusion-weighted imaging,Apparent diffusion coefficient,In-phase and opposed-phase
鄧彤(1979~),男,本科,主管技師,研究方向:影像質(zhì)量控制。
R 445.2
A
0253-4304(2016)01-0060-03
10.11675/j.issn.0253-4304.2016.01.18
2015-10-09
2015-12-22)