磁共振全身彌散成像對胃腸道惡性腫瘤的術(shù)后隨訪價(jià)值

魏來，朱荊皓，彭屹峰

磁共振全身彌散成像對胃腸道惡性腫瘤的術(shù)后隨訪價(jià)值

魏來，朱荊皓，彭屹峰*

目的探討3.0 T全身磁共振成像的技術(shù)對于胃腸道惡性腫瘤性疾病的術(shù)后隨訪價(jià)值。材料與方法對19例術(shù)后隨訪的胃腸道惡性腫瘤患者行WBMRI (DWI+T2WI)，后處理平臺(tái)為GE ADW4.6工作站。Functool工具拼接橫斷面彌散圖像，得到HD-MIP圖像、黑白反轉(zhuǎn)圖像(類“PET”圖像)及偽彩色圖像；Pasting工具拼接冠狀面T2加權(quán)圖像，得到全身冠狀面T2加權(quán)圖像，再經(jīng)圖像融合得到類“PET-MR”圖像。結(jié)果19例患者(其中胃彌漫性大B細(xì)胞淋巴瘤2例，胃癌8例，結(jié)腸癌7例，直腸癌2例)均獲得圖像質(zhì)量良好的全身磁共振圖像。發(fā)現(xiàn)惡性轉(zhuǎn)移性病例6例，陽性率約32%。結(jié)論使用頭頸聯(lián)合線圈及體線圈接收方法可以改善中心頻率漂移現(xiàn)象，得到符合診斷需要的全身彌散圖像。3.0T MR全身彌散成像可清晰顯示胃腸道惡性腫瘤的轉(zhuǎn)移灶，對胃腸道惡性腫瘤的術(shù)后隨訪和輔助診斷具有重要價(jià)值。

彌散磁共振成像；全身成像；胃腸腫瘤

胃腸道惡性腫瘤的術(shù)前診斷及術(shù)后隨訪均需借助影像學(xué)檢查手段，多層動(dòng)態(tài)增強(qiáng)CT及相關(guān)重建技術(shù)可以很好地顯示大多數(shù)胃腸道惡性腫瘤原發(fā)病灶、部分轉(zhuǎn)移灶。目前，對于轉(zhuǎn)移病灶的檢出主要借助于核素骨掃描或正電子發(fā)射計(jì)算機(jī)斷層顯像(positron emission tomography/computed tomography，PET/CT)。1.5 T全身磁共振成像(whole-body magnetic resonance imaging，WB-MRI)的技術(shù)對于胃腸道惡性腫瘤性疾病的輔助診斷價(jià)值也逐步顯現(xiàn)[1-4]，筆者初步探討3.0 T WB-MRI的診斷價(jià)值。

1 材料與方法

1.1 病例資料

本研究自2015年1至9月收集19例術(shù)后隨訪的消化道惡性腫瘤病例(男10例, 女9例； 年齡范圍52～87歲，平均年齡67.3歲)。所有病例原發(fā)消化道腫瘤病變均經(jīng)病理證實(shí)。其中胃彌漫性大B細(xì)胞淋巴瘤2例，胃癌8例，結(jié)腸癌7例，直腸癌2例。上述病例于3.0 T磁共振完成全身彌散成像。所有病例受檢前需排空胃腸道。

1.2 圖像采集

所有病例均于GE 3.0 T 750 W磁共振完成全身彌散成像，受檢者采取仰臥位、頭先進(jìn)的方式，掃描范圍覆蓋頭至膝關(guān)節(jié)上部，受檢者覆蓋頭頸聯(lián)合線圈及腹部線圈。掃描序列采用短翻轉(zhuǎn)時(shí)間反轉(zhuǎn)恢復(fù)序列，掃描參數(shù)：自由呼吸；TR 8000 ms，TE 249 ms；掃描野(FOV) 420 mm×420 mm；b=50、800 s/mm2；層數(shù)34；層厚5 mm；層間距1 mm；每段掃描時(shí)間1 min 44 s；重復(fù)7段(頭段、頸段、胸段、上腹部、下腹部、盆腔及雙上肢)?？倰呙钑r(shí)間約12 min，于GE ADW 4.6工作站重建得到全身彌散圖像，即類“PET”圖像。此外，加掃冠狀面T2WI，掃描參數(shù)：自由呼吸；TR 最小值，TE 249 ms；FOV 480 mm×480 mm)；層數(shù)19；層厚8 mm；層間距2 mm；每段掃描時(shí)間30 s；重復(fù)4段(頭頸段、胸段、腹盆段、雙上肢)，總掃描時(shí)間約2 min。于GE ADW 4.6平臺(tái)可重建出全身T2WI，通過融合彌散加權(quán)圖像及T2WI，可得到類“PET-MR”(positron emission tomography/ magnetic resonance imaging，PET/MR)圖像。

由2名具有5～10年放射診斷經(jīng)驗(yàn)的放射科醫(yī)師分別閱片診斷。橫斷面彌散原始圖像及冠狀面T2加權(quán)原始圖像作為診斷參照。如診斷意見不一致，由2名醫(yī)師會(huì)診做出最終診斷。

2 結(jié)果

所有病例均耐受該檢查，無任何不良反應(yīng)。無需鎮(zhèn)靜劑或?qū)Ρ葎?。全身彌散圖像發(fā)現(xiàn)6例術(shù)后隨訪的消化道惡性腫瘤患者具有轉(zhuǎn)移性病灶，見表1。7個(gè)轉(zhuǎn)移性病灶位于4個(gè)區(qū)域。其中1例胃癌病例同時(shí)具有肝臟及腹腔淋巴結(jié)轉(zhuǎn)移。原發(fā)病灶均已由病理證實(shí)，其中1例直腸癌術(shù)后病例發(fā)現(xiàn)皮下轉(zhuǎn)移結(jié)節(jié)，該病灶于CT檢查中并無明確陽性表現(xiàn)，但于磁共振全身彌散檢查中得以清晰顯示，1例直腸癌術(shù)后病例發(fā)生雙肺多發(fā)轉(zhuǎn)移，1例胃癌病例發(fā)生后腹膜淋巴結(jié)轉(zhuǎn)移，所有轉(zhuǎn)移灶均由活檢病理證實(shí)(圖1～12)。

同時(shí)，WBD也可以清晰顯示部分良性病灶，1例胃癌術(shù)后的病例顯示直腸腔內(nèi)贅生物，腸鏡病理證實(shí)為腺瘤。此外，于上述病例中發(fā)現(xiàn)肝囊腫4例，腎囊腫6例，胰腺囊腫2例，膽石癥2例。

表1病例構(gòu)成及轉(zhuǎn)移灶分布情況Tab. 1Patients constitution and metastasis distribution

3 討論

3.1 成像技術(shù)改進(jìn)

本研究是基于3.0 T磁共振平臺(tái)，3.0 T磁共振擁有信噪比高、軟組織分辨率高的固有優(yōu)點(diǎn)。

但3.0 T磁共振全身彌散成像較1.5 T磁共振技術(shù)難度大。3.0 T磁共振平臺(tái)的偽影較為嚴(yán)重，如幾何變形、圖像的剪切和重影效果，這些都會(huì)減低圖像質(zhì)量。此外，由于不同段之間中心頻率變化大，即使每一段圖像質(zhì)量良好，全身重建圖像仍可能出現(xiàn)中心漂移，導(dǎo)致位移偽影，影響重建圖像的質(zhì)量，矢狀面重建圖像上尤為明顯[5-8]。雖然對診斷準(zhǔn)確性不會(huì)造成影響，但會(huì)影響重建圖像的質(zhì)量。在本研究中，為改善中心頻率漂移的現(xiàn)象，我們使用頭頸聯(lián)合線圈及腹部線圈接收(不同于此前大多數(shù)研究所采用的體線圈接收)，結(jié)果顯示：段間位移偽影明顯改善，同時(shí)信噪比提高。

3.2 WB-DWI用于胃腸道惡性腫瘤的臨床價(jià)值

目前，WB-MRI多用于全身多發(fā)性病變的相關(guān)研究，尤其是惡性腫瘤骨轉(zhuǎn)移方面。WB-MRI用于胃腸道腫瘤性病變的相關(guān)研究則較少。本研究選擇胃腸道惡性腫瘤術(shù)后隨訪的病例為研究對象，初探其應(yīng)用價(jià)值，研究結(jié)果表明WB-MRI (DWI+T2WI序列)可用于胃腸道惡性腫瘤的隨訪復(fù)查及輔助診斷，可以清晰顯示肝內(nèi)轉(zhuǎn)移、周圍及后腹膜淋巴結(jié)轉(zhuǎn)移、腹壁以及肺內(nèi)的轉(zhuǎn)移灶，但對于肺部微小病變顯示較差，對于肺部2 cm以上轉(zhuǎn)移性病變較為敏感。此外，WB-MRI可顯示其他良性病變。

胃腸道惡性腫瘤的轉(zhuǎn)移通常累及范圍是實(shí)質(zhì)臟器、腹盆腔及淋巴結(jié)轉(zhuǎn)移。WB-MRI可以清晰顯示淋巴結(jié)，尤其是病理性腫大淋巴結(jié)[9-12]。本研究中，WB-MRI結(jié)合常規(guī)磁共振序列還可以清晰顯示胃腸道惡性腫瘤的腹部實(shí)質(zhì)臟器和軟組織的轉(zhuǎn)移。轉(zhuǎn)移性病變于DWI序列大多呈高信號(hào)，有時(shí)在CT掃描及磁共振其他序列上會(huì)體現(xiàn)出原發(fā)腫瘤灶的影像學(xué)特點(diǎn)，但最為可靠的診斷依據(jù)仍是明確的胃腸道惡性腫瘤病史?；仡櫺苑治霭l(fā)現(xiàn)，胃腸道惡性腫瘤發(fā)生術(shù)后轉(zhuǎn)移者大多是進(jìn)展期惡性腫瘤病例，一些病例甚至于術(shù)中就已發(fā)現(xiàn)局部淋巴結(jié)轉(zhuǎn)移，與胃腸道惡性腫瘤的臨床特征相符。

圖1，2男，64歲，直腸浸潤潰瘍型管狀腺癌術(shù)后，肛周不適1周，盆腔CT平掃及增強(qiáng)示臀裂處皮下軟組織增厚，平掃平均CT值約49 Hu，增強(qiáng)掃描平均CT值約57 Hu，較難診斷圖3～6圖3為黑白反轉(zhuǎn)圖像。圖4為橫斷面彌散圖像。圖5、6為橫斷面T1WI脂肪抑制圖像、T2WI脂肪抑制圖像。MRI可以清晰顯示右側(cè)臀部局部皮下轉(zhuǎn)移結(jié)節(jié)灶，彌散圖像對病灶顯示的敏感性更高，且彌散加權(quán)呈高信號(hào)有助于定性診斷圖7，8女，79歲，直腸潰瘍性腺癌術(shù)后，咳嗽、咳痰2 d。黑白反轉(zhuǎn)圖像及融合類“PET-MR”圖像示兩肺多發(fā)腫塊(箭頭)。針吸活檢病理示轉(zhuǎn)移性癌圖9，10女，85歲，胃腺癌術(shù)后，近來納差、體重減輕，黑白反轉(zhuǎn)圖像及橫斷面彌散圖像示后腹膜淋巴結(jié)轉(zhuǎn)移(箭頭)圖11，1257歲，胃癌根治術(shù)后16年，左下腹疼痛不適1周余。橫斷面彌散圖像及黑白反轉(zhuǎn)圖像示直乙結(jié)腸交界處團(tuán)片狀異常信號(hào)灶，磁共振全身彌散成像診斷為腸癌，腸鏡病理示高級別上皮內(nèi)瘤變Fig. 1, 2Fig.1 (left) and 2 (right). A 64 years old man post resection of rectal ulcerating tubular adenocarcinoma had discomfort around anus door for 1 week. Pelvic CT with enhancement showed perianal subcutaneous soft tissue thickening. Pre-contrast scan the average CT number was 49 Hu, while postcontrast scan the average CT number was 57 Hu. But it was hard to diagnose.Fig. 3—6Fig.3: The gray-scale inverted DWI. Fig.4: The axial DWI with fat suppressed. Fig.5, 6: The axial T1WI and T2WI with fat suppressed. A subcutaneous metastasis nodule was found (arrowhead). DWI is more sensitive in detecting the lesion and easier to diagnosis.Fig. 7, 8A 79 years old female patient post resection of rectal ulcerating adenocarcinoma had cough and sputum for 2 days. There are multiple pulmonary masses showed on gray-scale inverted DWI (Fig.7) and “PET-MR” like images (Fig.8) as indicated by the arrowhead. The pathological result of aspiration biopsy was metastatic carcinoma.Fig. 9, 10A 85 years old female patient post resection of gastric adenocarcinoma had a recent sizable weight loss. The gray-scale inverted DWI and axial DWI showed retroperitoneal lymph node metastasis (arrowhead).Fig. 11, 12A 57 years old female patient post radical operation of gastric cancer before 16 years ago had left lower abdominal pain for more than a week. The gray-scale inverted DWI and axial DWI showed abnormal signal around straight sigmoid junction (arrowhead) diagnosed as cancer. The pathological diagnosis of endoscope biopsy was high grade intraepithelial neoplasia.

WB-MRI對于胃腸道轉(zhuǎn)移性病變的檢出非常敏感。WB-MRI有助于病灶檢出及病灶定性。胃腸道惡性腫瘤患者臨床中需規(guī)律隨訪，最為普遍使用的檢查方法是骨掃描。條件允許的情況下，PET/CT是更好的選擇。但在長期規(guī)律的腫瘤患者隨訪中，輻射劑量不可以忽略不計(jì)。相比常規(guī)的核素骨掃描及PET/CT檢查，WB-MRI優(yōu)勢在于無電離輻射，可以提供骨骼、全身臟器及組織的影像學(xué)信息，而價(jià)格相對低廉。

WB-MRI是癌癥分期的一項(xiàng)新進(jìn)影像診斷技術(shù)[13-15]。使用頭頸聯(lián)合線圈及體線圈接收方法可以改善中心頻率漂移現(xiàn)象，得到符合診斷需要的全身彌散圖像。3.0 T MR全身彌散成像可清晰顯示胃腸道惡性腫瘤轉(zhuǎn)移灶，對胃腸道惡性腫瘤的臨床隨訪和輔助診斷具有重要價(jià)值。WB-MRI有望成為胃腸道惡性腫瘤性病變術(shù)后隨訪的全身檢查方法之一。

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Application of whole-body diffusion-weighted imaging on gastrointestinal malignant tumors

WEI Lai, ZHU Jing-hao, PENG Yi-feng*
Department of Radiology, Shanghai PutuoHospital, Shanghai University of Traditional Chinese Medicine, Shanghai 200062, China

Objective:To discuss the technical feasibility of whole body diffusion weighted imaging (WB-DWI) on 3.0 T magnetic resonance imaging (MRI).To evaluate the auxiliary diagnostic role of WB-DWI in patients with gastrointestinal malignant tumors by detection of primary tumors and metastasis.Materials and Methods:Nineteen patients with gastrointestinal malignancy operation history were enrolled in our study. All patients received whole body MRI examination. The magnetic resonance (MR) examination was performed on 3.0 T MR scanner using coils. The images were reviewed separately by two radiologists.Results:A total of 8 metastatic lesions in 4 regions of 7 patients were detected by whole body DWI. One patient with stomach cancer had both liver metastasis and lymph nodes metastasis.Conclusions:The WB-DWI images that meet the diagnostic needs can be obtained on 3.0 T MRI. WB-DWI reveals excellent detection of metastasis of gastrointestinal malignant tumors.

Diffusion magnetic resonance imaging; Whole body imaging; Gastrointestinal neoplasms

上海中醫(yī)藥大學(xué)附屬普陀醫(yī)院放射科，上海 200062

彭屹峰，E-mail：peng2188@sina.com

2016-06-28

接受日期：2016-09-26

R445.2；R57

A

10.12015/issn.1674-8034.2016.11.010

魏來, 朱荊皓, 彭屹峰. 磁共振全身彌散成像對胃腸道惡性腫瘤的術(shù)后隨訪價(jià)值. 磁共振成像, 2016, 7(11): 847-850.

*Correspondence to: Peng YF, E-mail: peng2188@sina.com

Received 28 June 2016, Accepted 26 Sep 2016