1、直肠癌：MRI与临床2023-1-11直肠为大肠的末段，长约15-16cm，位于小骨盆内。上端平第3骶椎处接续乙状结肠，沿骶骨和尾骨的前面下行，穿过盆膈，下端以肛门而终。直肠肛门外科学上，将由盆筋膜脏层包绕的直肠周围脂肪结缔组织、血管、神经和淋巴组织统称之为直肠系膜（mesorectum）。直肠癌环周切缘（circum ferential resection Margin，CRM）是一个外科学概念，是指围绕直肠系膜的盆腔脏层筋膜，即直肠系膜筋膜（mesoretal fascia，MRF）。相关基本概念全直肠系膜切除术（total mesorectal excision TME）解剖学基础：腹膜
2、返折以上的直肠有腹膜覆盖，返折以下的直肠无腹膜，而由盆筋膜所覆盖。盆筋膜分脏层和壁层，其脏层是由腹膜下筋膜向下位于腹膜返折以下，其浅叶包绕盆腔的内脏，如膀胱、子宫、直肠等而形成。盆筋膜壁层与脏层相对应，是由腹膜下筋膜的深叶进入盆腔后覆盖盆壁四周而形成的。临床意义：直肠系膜筋膜（MRF）是直肠与周围邻近器官间的重要屏障，可有效防止直肠炎症或肿瘤等向其它腹膜外间隙扩散，对阻止肿瘤局部浸润和远处转移有重要意义。来源：中国临床解剖学杂志2005年第23卷第4期明确直肠系膜的解剖学结构是应用全直肠系膜切除术(total mesorectal excision,TME)治疗直肠癌的基础。但至今，有关直肠系
3、膜的报道也仅限于零星的外科解剖资料1,2，对直肠系膜形态结构的解剖学研究存在较大的分歧3。该文章进行了专题解剖学研究，以期为临床TME广泛开展提供应用基础理论。研究显示：1 直肠系膜筋膜（即盆脏筋膜）在直肠和直肠系膜周围是一个连续、完 整的结构，下端止于直肠肛管连接处；2 直肠系膜是由环绕在直肠周围的血管、淋巴管、神经及脂肪等疏松 的结缔组织构成。本结果与Bisset等4的研究相类似。直肠系膜的定义应该是包绕在袖套样直肠系膜筋膜（即盆脏筋膜，并包括该筋膜在内）之内的直肠周围所有的血管、淋巴管和淋巴结、神经及脂肪组织等。作者通过仔细地解剖盆脏筋膜，认为直肠和“直肠系膜”一起被完整地包裹在含胶原纤
4、维的袖套样盆脏筋膜中，因此，沿直肠盆脏筋膜外解剖，可以将直肠系膜完整地切除，并且切除后腹下神经和盆丛仍完整地保留在盆腔侧壁上，未受损害。本研究用MRI检测直肠系膜的结果也证实了这一点。解剖学研究与MRI影像图2 盆腔标本解剖前的 MRI(T1WI)箭头示直肠系膜筋膜为均匀的低信号线；三角示直肠系膜则为均匀高信号。图3 盆腔标本解剖后的 MRI(T1WI)箭头示直肠系膜筋膜所产生的低信号线所在的位置；三角示直肠系膜。图1 盆腔矢状剖面新鲜标本（虚线之间为直肠系膜）。来源：中国临床解剖学杂志2005年第23卷第4期Rectal Cancer-MR staging 2.0Rhiannon van L
5、oenhout,Frank Zijta,Max Lahaye,Regina Beets-Tan and Robin Smithuis Radiology Departement of the Medical Centre Haaglanden in the Hague,The Netherlands Cancer Institute in Amsterdam and the Alrijne Hospital in Leiderdorp,the Netherlands直肠癌：MR分期Introduction Total mesorectal excision TNM-stage MR proto
6、col DWI Location of the tumor Low rectal cancer T-stage T1 and T2 T3 T3 with MRF involvement T4a-Invasion peritoneal reflection T4b-Invasion surrounding organs Extramural vascular invasion(EMVI)N-stage Extramesorectal lymph nodes Regional Lymph nodes Surgery Low Anterior Resection(LAR)Abdomino-Perin
7、eal-Resection(APR)Intersphincteric APR and ELAPE Chemo-and Radiotherapy Structured MR report Publication date December 17,2015 This is an updated version of the 2010 article.The two major advancements in the treatment of rectal cancer are total mesorectal excision(TME),and neoadjuvant radiotherapy a
8、nd chemotherapy(1,2,3).Both have dramatically changed the local recurrence and survival rates.MRI is the most accurate tool for the local staging of rectal cancer and is a powerful tool to select the appropriate treatment(4,5,6).The decision whether a patient with rectal cancer is a candidate for TM
9、E only or neoadjuvant therapy followed by TME,is made on the findings on MRI(7).2015年12月17日的更新版：直肠癌治疗的2个重要进展，一是全直肠系膜切除术(TME)，二是新辅助放疗和化疗。这两方面的措施明显改善了直肠癌局部的复发率和生存率。MRI是直肠癌局部分期最精确的评价方法，并作为非常有用的工具用于选择适宜的治疗。这里讨论的问题是：直肠癌病人，是只能选择TME？还是采用新辅助治疗而随后再行TME？通过MRI的表现作出决定。The mesorectal fascia(MRF)plays a crucial r
10、ole in the treatment plannnig.In TME the mesorectal fascia is the resection plane and it has to be tumor-free.A distance of the tumor to the mesorectal fascia of 1 mm is regarded as not suitable for TME and is called an involved MRF.This means that the tumor has to be downstaged before TME is possib
11、le.On MRI the mesorectal fat has high signal intensity on both T1-and T2-weighted images.The mesorectal fat is surrounded by the mesorectal fascia,which is seen as a fine line of low signal intensity(arrows).High resolution T2-images are needed to clearly identify the MRF(7).Rectum is surrounded by
12、mesorectal fat within the mesorectal fascia(arrows).Total mesorectal excisionIn 1979 surgeon Richard John Heald introduced the total mesorectal excision(TME).In TME the entire mesorectal compartment including the rectum,surrounding mesorectal fat,perirectal lymph nodes and its envelope,the mesorecta
13、l fascia(MRF),is completely removed by precise dissection along anatomical planes(figure).TME is the best surgical treatment for rectal cancer provided that the resection margin is free of tumor.It is now a standard technique and part of procedures such as low anterior resection(LAR),in which the re
14、ctum and sigmoid colon are resected or abdominoperineal resections(APR),in which the rectum and anal canal are resected.1979年外科医生Richard John Heald开展了全直肠系膜切除术（total mesorectal excision，TME）.TME中的全直肠系膜包括直肠、周围系膜脂肪、淋巴结及其包膜，即直肠系膜筋膜（mesoretal fascia，MRF）完全切除（图）。全直肠系膜切除术(TME)已被证明是直肠癌根治的最佳外科手术方法。直肠由直肠系膜筋膜（
15、箭）内直肠系膜的脂肪包绕直肠系膜筋膜全直肠系膜切除*MRF在直肠癌治疗计划中扮演关键角色。*在TME中，做直肠系膜筋膜切除计划必须要求该系膜筋膜无肿瘤侵犯。*癌灶至直肠系膜筋膜的距离 1 mm 时，被认为不适合TME，这称为直 肠系膜筋膜受侵。*这意味着直肠癌在做TME之前必须处于早期。*在MRI上，直肠系膜脂肪在T1WI和T2WI表现为高信号。*直肠系膜脂肪由直肠系膜筋膜（盆腔脏层筋膜）环绕，表现为线样低信 号影（箭）。*为清晰地证实MRF结构，高分辨T2WI是必须的。The MRF is only circumferential in the low-rectum below the an
16、terior peritoneal reflection(see next illustration).The MRF does not apply to the anterior peritonealized surface of the anterior mid-and high rectum.直肠系膜筋膜（MRF）仅仅是在前腹膜返折处下面的直肠下段呈圆周环绕；而直肠系膜筋膜（MRF）不适用于前表面由腹膜被覆的中、上段直肠。直肠系膜（mesorectum）The treatment of a patient with rectal cancer depends on the TNM-sta
17、ge and whether the MRF is involved.T-staging T1 and T2 tumors are limited to the bowel wall.T3 tumors grow through the bowel wall and infiltrate the mesorectal fat.They are further differentiated in:T3a 15 mm T3 MRF+tumor within 1mm of MRF MRF-no tumor within 1 mm of MRFThe N-stage is based on the n
18、umber of suspicious lymph nodes:N0 no suspicious nodes N1 1-3 suspicious nodes N2 4 suspicious nodesRef:Colon and Rectum Cancer Staging-quick reference(AJCC)直肠癌病人的治疗依赖于TNM分期以及是否存在MRF受侵。T（肿瘤）分期T1和T2肿瘤限于肠壁；T3肿瘤穿过肠壁和侵犯直肠系膜的脂肪，亚型：T3a:超出肠壁固有肌层小于1mmT3b:超出肠壁固有肌层1-5mmT3c:超出肠壁固有肌层5-15mmT3d:大于15mmT3 MRF+：肿瘤在M
19、RF的1mm之内 MRF-：MRF的1mm之内没有肿瘤T4a:侵犯腹膜T4b：侵犯邻近脏器N（区域淋巴结）分期是根据可疑淋巴结的数目N0 没有可疑淋巴结N1 发现1-3个可疑淋巴结N2 发现4个或以上的可疑淋巴结直肠癌的TNM分期（肿瘤分期、区域淋巴结分期）This figure illustrates the T-stage and mesorectal fascia involvement in the axial plane,which is usually the best imaging plane for the T-staging.左图：直肠癌的T分期与直肠系膜筋膜受侵在轴位上的
20、表现。器官轴位扫描是肿瘤T分期最好的成像方位。直肠环周切缘直肠环周切缘（CRM,即即 MRF）示意图：T2 肿瘤限于肠壁T3 肿瘤：T3 CRM（环周切缘）-；T3 CRM+（红箭）T4 肿瘤浸润精囊和前列腺当距筋膜1毫米内出现淋巴结时则需要报告，尤其是大的淋巴结（蓝箭）。N stagingLymph node involvement is an important factor for the treatment and the prognosis of the patient.MR has proven to have a low diagnostic accuracy for disti
21、nguishing positive or negative lymph nodes when characterization is based on size criteria alone.At the moment in the Netherlands we use a combination of both size and morphologic criteria as listed in the table.Nodes larger than 9 mm are always regarded as suspicious.Smaller lymph nodes need additi
22、onal malignant characteristics to be considered suspicious.Since staging and treatment of rectal cancer is constantly evolving,you may have to check your local oncology team for the latest developments.N（区域淋巴结）分期区域淋巴结受侵是直肠癌治疗和预后的一个重要因素。对形态上属于正常大小的淋巴结，究竟是属于阳性还是阴性的淋巴结，MR对此诊断正确率很低。N分期：可疑淋巴结恶性特征边界模糊 不均匀
23、 圆形短轴cN期N0:无可疑淋巴结N1:1-3可疑淋巴结N2:4或4个以上的淋巴结小于5mm:需要3个恶性特征 5-9mm:需要2个恶性特征大于9mm:常为提示恶性左边的图表是依据淋巴结大小与具有的恶性特征两方面定义可疑恶性淋巴结：大于9mm的淋巴结应列为可疑恶性。较小的淋巴结需要有恶性特征，方可考虑可疑恶性。（注：这里没有提到MRI的DWI表现）区域淋巴结分期：可疑淋巴结的影像学判定Treatment The treatment is based on the clinical or cTNM.The cTNM is based on the results of endoscopy and
24、 imaging.1.Low risk tumorsT1,T2 and borderline T3 without suspicious nodes can directly undergo surgery.2.Intermediate risk tumorsT3 with 5mm invasion or tumors with 1-3 suspicious nodes-will be treated with short term radiotherapy preoperatively.3.High risk tumorsT3 with involved MRF or T4 tumors o
25、r tumors with 4 or more suspicious nodes will receive neoadjuvant chemotherapy and long term radiation therapy and will be restaged to determine whether TME is possibleAfter the operation the surgical specimen is analyzed by the pathologist.直肠癌治疗直肠癌的治疗依据临床或cTNMcTNM是依据内窥镜和影像学一、低风险肿瘤T1，T2和T3边缘线没有可疑淋巴结
26、能够直接接受外科手术。二、中间级风险肿瘤侵犯范围大于5mm或伴1-3个可疑淋巴结的T3，需要做短期的术前放疗。三、高风险肿瘤MRF侵犯的T3，或T4肿瘤或肿瘤伴4个或更多可疑淋巴结，需要接受新辅助化疗和长时间的放疗再重新评价实施TME的可能性。手术后，切除标本由病理学家分析。新辅助化疗、长时间放疗 TME短时间放疗 N0无可疑淋巴结 N11-3个可疑淋巴结 N24个以上可疑淋巴结 T1 T2T3 5mm 侵润T3 5mm 侵润T3 1mm 距离 MRFT4 器官侵犯TMEMR protocol T2-weighted FSE High resolution 2D T2WI FSE in the
27、 sagittal,axial and coronal plane are required for state-of-the-art staging of rectal cancer.The slice thickness should be 3 mm.Gadolinium-enhanced MR does not improve diagnostic accuracy and is not included in the protocol.Start with the sagittal series.These can be used to plan the axial images,pe
28、rpendicular to the rectal wall at the level of the tumor to avoid volume averaging(yellow box).Coronal images are planned parallel to the anal canal(green box),especially in low-rectal tumors in order to accurately evaluate the depth of tumor invasion into the anal sphincter.The cranial border of th
29、e FOV is vertebral body L5,the caudal border is below the anal canal.AngulationProper angulation is of vital importance in correctly identifying tumor borders.In this example the axial images were originally not properly angulated(red lines not perpendicular to the tumor).This resulted in the false
30、impression that the MRF was involved on the anterior side(red circle).After proper angulation it was clear that the MRF was not involved(yellow circle).MR检查方案T2WI FSE序列高分辨2D快速自旋回波T2WI的矢状、轴位及冠状是直肠癌检查的基本序列，层厚取3mm。Gd-DTPA不改善诊断的准确性，故检查方案中不予包括。扫描从矢状序列入手。轴位成像时注意要使扫描线垂直于肿瘤部的肠壁，从而避免形态的失真（黄框）。冠状成像，扫描线平行于肛管（绿
31、框），尤其是低位直肠癌用于准确评价肿瘤侵犯肛门括约肌的深度。扫描范围：FOV的头侧包括腰5椎体，尾侧缘包括肛管下缘。扫描线的倾斜角适当的扫描线倾斜角对识别肿瘤的边界至关重要。左图的举例：红线未与肿瘤垂直，造成MRF前缘受侵之假象（红圈）。在给予适当的倾斜角后，清楚显示MRF未受侵（黄圈）。DWIDiffusion weighted imaging can be useful for。The figure shows a semicircular T3 tumor with perirectal invasion extending from 3-9 oclock of the circumfe
32、rence.Corresponding diffusion restriction on the ADC map and calculated DWI(b=1000 s/mm2)。DWI in restaging DWI is very useful in determining the response to chemoradiation.In this case there is persistent high signal on images with high B-values.which indicates incomplete response.DWI在原发癌的分期中，DWI有助于
33、肿瘤及淋巴结的检测。左上图显示半环形T3肿瘤并周围3-9点钟范围的环周侵犯。对应的DWI扩散受限（b值=1000）。肿瘤再分期：DWIDWI在肿瘤化疗、放疗效果判断中，是非常有用的。右上图病例在新辅助放疗后，在高B值图上存在持久性的高信号，它表明疗效反应的不均衡性。ADCADCDWI B=1000放化疗后，不能只对比大小，也不可能又做活检吧？插入：转移性肿瘤治疗效果影像学的评估：DWI （附2个病例展示）加深印象T2WIT1WIDWIADC8月9月11月本院3.0T病例胆囊癌腹膜后胆囊癌腹膜后转移癌灶治疗转移癌灶治疗前后前后 三个月的三个月的变化（同样的变化（同样的B B值）。值）。看看DWI
34、DWI对对癌灶活性检测癌灶活性检测敏感性评价。敏感性评价。2015年5月、6月、9月、12月CT平扫。期间化疗射频治疗后呢？如何评价疗效？结肠癌肺转移灶2016年3月CT平扫（右下肺肿块增大，另注意左肺新出现了结节灶）。4月下旬行右肺肿块的射频消融治疗5.5mm5月11日CT平扫轴位：右肺肿块CT增强后期轴位：右肺肿块射频消融治疗后，右肺的肿块疗效如何？冠状图：右下叶肿块平扫加增强那么射频治疗后的CT平扫加增强能判断右下灶的治疗效果吗？很难判断！平扫增强CT值无大的差别8.0mm2016年5月11日CT，再看看左侧结节也只是较前稍增大，打药前后密度上没啥特征再看看：右肺病变2016年5月20日
35、MRIT1WIT2WI轴位压脂肪T2WI左肺结节的T2WI压脂肪图：与右肺病灶的信号明显不同注：ADC图中央区的低值，不要误认为扩散受限！为什么？左肺的结节扩散受限右侧肺肿块及左肺结节的DWI（b=800）左右肺部病灶的中b值（b=150）图MRI多期增强检查：右侧肺肿物无明显强化左肺小结节MR动态增强：可见强化预扫早期中期后期左肺的结节灶可见强化（冠状）2016-8-15即3个月后再复查MRI9.79cm从这个肺部病例，也看出MRI技术综合使用的优势，尤其DWI技术在评价肿瘤活性的重要应用价值。Location of the tumorThe rectum extends from the
36、anorectal junction to the sigmoid.The rectosigmoid junction is arbitrarily defined as 15 cm above the anorectal angle.A tumor more than 15 cm above the anorectal angle is regarded and treated as a sigmoid tumor.Rectal cancer can be divided into:Low rectal cancer:Distal border is 0-5 cm from the anor
37、ectal angleMid rectal cancer:Distal border is 5-10 cm from the anorectal angleHigh rectal cancer:Distal border is 10-15 cm from the anorectal angle肿瘤的定位 直肠是由肛门上延伸并与乙状结肠相接的部分。*直肠-乙状结肠结合部长度不恒定，一般指位于 直肠肛管角上15cm处。*超过直肠肛管角15cm以上的肿瘤，是作为乙状 结肠肿瘤定义并治疗。直肠癌的划分：*低位直肠癌 直肠肛管角上 0-5cm的直肠末端*中位直肠癌 直肠肛管角上 5-10cm的直肠末端*
38、高位直肠癌 直肠肛管角上10-15cm的直肠末端Low rectal cancerLow rectal cancer has a higher local recurrence rate.The distal tapering of the mesorectal fat implies that low rectal cancer more easily invades the mesorectal fascia,pelvic wall and surrounding organs.It will be more difficult for the surgeon to get a tumor
39、 free resection(see figure).The report should describe the relationship of the tumor to the anal sphincter complex in case of low rectal cancer.The internal sphincter is the distal continuation of rectal circular fibers.Consequently,if a tumor extends caudally into the internal sphincter,it is consi
40、dered a T3 tumor.Involvement of the intersphincteric plane,external sphincter and levator musculature should be assessed,as this may influence treatment planning(see section surgery).Involvement of the intersphincteric plane is best observed on coronal planes(figure)(7).Low rectal cancer with extens
41、ion of the tumor in the internal sphincter and intersphincteric space.The longitudinal muscle layer within the right intersphincteris space,can still be depicted(arrow)低位直肠癌低位直肠癌低位直肠癌局部复发率较高。直肠系膜远端的脂肪逐渐变细意味着低位直肠癌更容易侵入MRF及盆壁与周围的结构，外科手术根治肿瘤将会更难。低位直肠癌，肿瘤侵犯内括约肌及内括约肌间隙。右侧内括约肌间隙内的纵行的肌层得以显示（箭）。*低位结肠癌病例，诊断报
42、告应叙述肿瘤与直肠括 约肌复合体的关系。*肛门内括约肌是直肠环形纤维在末端的延续，因此，如果肿瘤延伸至尾侧而进入内括约肌，则 被认定为T3肿瘤。*肿瘤对内括约肌平面的侵犯时，由于会影响到 治疗计划，因而要对外括约肌、肛提肌进行评估。*MR上采用冠状位（注意扫描角度，见前述），最适于 观察内括约肌平面的侵犯。T-stageSemicircular T2 tumor in the distal rectum,with sharply demarcation of the external muscular layer.T1 and T2T1 and T2 tumors are limited to
43、 the bowel wall and have a good prognosis.MR imaging is unable to distinguish between tumor extension into the mucosa,submucosa and muscularis propria and therefore can not differentiate between Tis(in situ),T1 and T2 tumors.Although T1 tumors could be treated with local excision,the treatment of ch
44、oice in both T1 and T2 tumors is TME.Only if there is a preference for local excision through transanal endoscopic microsurgery(TEM-procedure),endorectal US can be helpful,because it sometimes can differentiate between T1 and T2 tumors.Key finding in T1 and T2 rectal tumors is an intact external mus
45、cularis layer,which is identified as a hypointense thin line surrounding the rectum(figure).肿瘤分期肿瘤分期T1或T2肿瘤限于肠壁；T3a:超出肠壁固有肌层小于1mmT3b:超出肠壁固有肌层1-5mmT3c:超出肠壁固有肌层5-15mmT3d:大于15mmT3 MRF+：肿瘤在MRF的1mm之内 MRF-：MRF的1mm之内没有肿瘤T4a:侵犯腹膜T4b：侵犯邻近脏器（见前介绍）肿瘤1期和肿瘤2期1期和2期的肿瘤限于肠壁，预后好。MR成像不能区分二者：侵犯粘膜层或粘膜下层，还是侵及固有肌层。因此，不能鉴
46、别1期即原位癌和2期的肿瘤。虽然1期的肿瘤应该是局部切除，但在实际治疗的选择上，对1、2期还是采用TME.如果适合经内窥镜下微创做肿瘤局部切除，直肠超声会有帮助，因有时可区分T1与T2期的肿瘤。T1与T2期的直肠肿瘤关键的表现是外肌层完整，它表现为直肠环周的线状低信号（图，此时若结合DWI更有意义）。直肠远侧半圆形T2期肿瘤，外肌层边缘锐利。T3 T3-tumors grow through the external muscularis into the surrounding mesorectum.As the rectum does not contain a serosal layer
47、,tumor invades directly into the mesorectal fat and can spread to lymph nodes and beyond.Spread into the mesorectum can be depicted as spicules of low signal intensity in the hyperintense mesorectal fat or distortion of the hypointense muscularis propria.T3-tumors are further differentiated in:T3a:t
48、umour extends 15 mm beyond muscularis propria MRF-no tumor within 1mm of MRF MRF+tumor within 1mm of MRFT3 MRF-rectal cancer.Semicircular mid rectum tumor with tumor invasion into the mesorectum,extending from app.1-4 oclock of the circumference.直肠癌T3期伴直肠系膜筋膜阴性（MRF-）。半圆形的中位直肠癌伴肿瘤侵犯直肠系膜，侵及圆周范围1-4点钟位。
49、*T3（肿瘤3期）肿瘤生长透过外肌层而侵犯 周围的直肠系膜。*因为直肠没有浆膜层，肿瘤直接侵犯直肠系 膜脂肪并可扩散至淋巴结甚至其以外。*肿瘤扩散至直肠系膜，表现为位于直肠系膜脂 肪内针状的低信号或者为低信号的粘膜固有层 变形。T3期肿瘤进一步划分：T3a:肿瘤超出肠壁固有肌层小于1mm T3b:肿瘤超出肠壁固有肌层1-5mm T3c:肿瘤超出肠壁固有肌层5-15mm T3d:肿瘤超出肠壁固有肌层大于15mm MRF-：MRF的1mm之内没有肿瘤 MRF+：肿瘤在MRF的1mm之内Perirectal stranding Difficulty in distinguising true mes
50、orectal tumor invasion from desmoplastic reaction,is the main cause of overstaging.However,to prevent understaging,it is recommended to stage a tumor as T3 when stranding is present.Here we see two tumors with a similar MR-appearance.In A there was perirectal tumor invasion.In B the tumor was limite
