MRI在胰岛素瘤诊断中的价值

目的：探讨MRI在胰岛素瘤诊断中的价值。方法：回顾性分析经手术病理证实的43例共55个胰岛素瘤病灶的MRI影像表现。测量并比较胰岛素瘤病灶及周围正常胰腺组织的ADC值。结果：43例胰岛素瘤中,良性单发40例（93%）,多发3例（7%）。38例T1WI抑脂序列呈低信号;36例T1WI正反相位呈低信号;37例T2WI抑脂序列呈高信号;31例在DWI中呈高信号;其中3DLAVA多期动态增强检出26例。3例乏血供胰岛素瘤在MRI平扫时呈异常信号,但其LAVA增强和CT动态增强扫描各期未见显示。31例胰岛素瘤的ADC值平均约（1.71±0.17）×10-3 m/s,周围正常胰腺的ADC值平均约（2.23±0.29）×10-3 m/s,二者差异具有显著统计学意义（P〈0.001）。结论：在抑脂序列下DWI和增强检查能提高胰岛素瘤诊断的敏感性。胰岛素瘤与周围正常胰腺组织信号差异在MRI抑脂序列上较为明显,扫描有利于病灶的检出。对乏血供胰岛素瘤,MRI平扫抑脂序列更具有诊断意义。     

抑脂技术和动态增强MRI在胰岛素瘤诊断中的价值探讨

目的 探讨抑脂技术和动态增强MRI在胰岛素瘤术前定位诊断中的价值。方法 12例手术病理证实的胰岛素瘤患者术前行MR检查，扫描序列包括：横断面SE T1WI，快速自旋回波(FSE)T2WI，加脂肪抑制技术的T1WI和T2WI(即T1WI FS和T2WI FS)，快速多层面扰相梯度回波(FMPSPGR)序列作动态增强扫描。结果 在常规T1WI和T2WI序列仅检出4例肿瘤，表现为T1WI稍低信号和T2WI稍高信号。在T1WI FS上7例呈均匀低信号，显示清晰；在T2WI FS上6例病灶呈不同程度的高信号。快速动态增强扫描(FMPSPGR)检出11例肿瘤，在动脉期7例肿瘤明显强化呈高信号，4例轻度强化呈稍高信号，1例无明显强化呈等信号，胰腺实质期和门脉期6例仍呈高信号，6例呈等信号。与手术后病理结果比较，动态增强MRI对胰岛素瘤术前定位诊断准确率为91．7％(11／12)。结论 动态增强MRI是胰岛素瘤术前定位诊断敏感而准确的方法。     

FLAIR和DWI序列对颅内胆脂瘤的诊断价值

目的:分析颅内胆脂瘤的MRI信号特点,探讨FLAIR和DWI序列对颅内胆脂瘤的诊断价值。方法:回顾性分析20例经病理证实的颅内胆脂瘤的MRI资料,比较FLAIR、DWI序列与常规T2WI、T1WI在显示病变范围、边界及对比度方面的特点。结果:20例颅内胆脂瘤T2WI均呈显著高信号,边界、范围显示不清,与周围脑脊液对比度差;18例T1WI呈类似于或稍高于脑脊液的低信号,2例T1WI呈高低混杂信号。总体边界、范围显示模糊,与周围脑脊液对比度较差;20例瘤体均无强化。20例FLAIR序列均呈混杂的不均匀信号,总体信号略高于或与脑实质类似,病变范围、边界显示较清晰,与脑脊液对比度好,与周围脑组织对比度差;DWI序列b=1000时均呈明显高信号,病变边界、范围显示清晰,与周围脑脊液及脑组织对比强烈,极易发现病变及确定范围。结论:颅内胆脂瘤的FLAIR和DWI序列均具有其特点,综合T1WI、T2WI序列可以较准确的诊断胆脂瘤,与颅内其他囊性病变鉴别;在显示病变边界、范围、对比度方面均优于T2WI、T1WI,特别是DWI序列病变范围边界显示清晰,对比度高,具有很高的诊断价值。     

胰岛素瘤的MRI诊断

目的：研究磁共振成像对胰岛素瘤的诊断价值。方法：16例手术证实的胰岛素瘤患者于术前行MR检查,扫描序列包括快速自旋回波序列T1W、T2W及脂肪抑制T1W、T2W。结果：16例均能准确检出,10例呈长T1低信号,13例显示不同程度的长T2高信号,T1及T2抑脂图像肿瘤同胰腺的信号对比增强,显示更为清晰。结论：应用MR快速成像技术和脂肪抑制序列,能够对胰岛素瘤进行较精确的定位诊断。     

弥散MRI诊断颅内表皮样囊肿的价值

目的:探讨磁共振弥散加权成像(DWI)及表观弥散系数(ADC)图诊断颅内表皮样囊肿的价值.材料和方法:分析19例表皮样囊肿常规MRI和DWI的信号特征,定量测定表皮样囊肿、正常脑实质和脑脊液的ADC值.结果:17例表皮样囊肿T1WI、T2WI呈等或稍高于脑脊液信号,2例T1WI呈高低混杂信号.肿瘤边缘弧线形增强或不增强.19例肿瘤DWI呈明显高于脑实质和脑脊液信号,肿瘤较脑脊液的平均ADC值显著减低,较脑实质的平均ADC值显著增高.结论:DWI优于常规MRI发现颅内表皮样囊肿,DWI上表皮样囊肿的高信号可能是肿瘤组织的T2余辉效应所致.     

3.0T磁共振LAVA-FLEX序列对胰腺肿瘤的诊断价值

目的：探讨LAVA-FLEX成像技术在胰腺肿瘤诊断中的应用价值。 方法：收集12例经病理证实的胰腺癌患者,术前行3.0T磁共振常规序列、DWI和LAVA-FLEX序列检查,观察与分析LAVA-FLEX序列与常规扫描序列在胰腺癌病变的敏感性和特异性。 结果：12例胰腺癌在常规序列显示胰腺癌为长T₂信号灶8例,略长T₂信号2例,等T₂信号2例,12例在DWI均呈高信号,T₁WI呈等信号。LAVA-FLEX序列图像质量高,压脂均匀,组织对比度高,扫描速度快,12例胰腺癌均呈低信号,较常规T₁WI具有明显优势。注射对比剂增强后特征性明显。 结论：LAVA-FLEX序列作为新技术,在胰腺癌诊断中具有与DWI相近的特异性与敏感性,可取代常规T₁WI、压脂T₁WI和3D动态增强T₁WI序列。     

原发性肝癌热消融术后疗效的MRI评价

目的 探讨磁共振成像对原发性肝癌射频消融术后疗效的评估价值。方法 选取46例行射频消融术的原发性肝癌患者术前及术后3个月进行肝脏MRI平扫、DWI及增强检查,分析术后疗效。结果 46例原发性肝细胞癌患者57个病灶,术后3个月时所有病灶均较术前缩小,无肿瘤残留者47个病灶,MRI表现T2WI压脂像呈低信号,DWI信号减低,ADC呈高信号,肿瘤复发者10个病灶,MRI表现T2WI压脂像仍呈高信号,DWI呈高信号,ADC呈低信号。结论MRI能够评估肝癌射频消融术后肿瘤是否残存或复发,及早检出复发灶,对制定下一步治疗方案意义重大。     

颅内少见部位胆脂瘤的MRI诊断

目的 探讨颅内少见部位胆脂瘤的MRI表现特征.提高该病的术前诊断率,减少误诊率.方法 回顾性分析经手术病理证实的6例颅内胆脂瘤的MRI表现,采用Siemens 3.0 T Skyra磁共振仪,均行平扫及增强扫描,1例加扫磁敏感加权成像(SWI)序列.结果 本组病例均为单发,枕大孔区1例,左侧中颅窝2例,右侧中颅窝1例,左侧枕叶脑实质2例.病灶范围较大,周边分叶状,灶周未见水肿,部分病灶沿阻力小的地方生长明显.5例T1WI、T2WI、T2 FLAIR序列信号混杂,DWI序列以高信号为主的混杂信号,其中枕大孔区病例信号较为特殊,T1 WI呈高信号,T2WI、T2FLAIR序列呈低信号,DWI为低信号,SWI序列最大强度投影(MIP)为稍高信号,相位(PHASE)图为等信号.结论 颅内少见部位胆脂瘤MRI表现具有特征性,可以做到术前定性诊断.     

双肾多发血管平滑肌脂肪瘤的MRI诊断

目的 分析双肾多发血管平滑肌脂肪瘤(angiomyolipoma,AML)的磁共振成像表现,探讨MRI对该病的诊断及鉴别诊断价值.方法 收集16例双肾AML病例,分析其MRI影像学表现,部分病例与手术病理结果对照.结果 16例病例共检出63个病灶,其中14例得到正确诊断并经手术(5例)或随访证实(9例),2例术前不能正确诊断.双肾AML的典型MR表现为:11例抑脂T2WI序列上呈不均匀低信号,5例抑脂T2WI序列上呈混杂高信号,13例T1WI正相位呈等信号,反相位信号有所衰减,3例T1WI正反相位信号无明显变化,增强后信号较均匀3例,欠均匀13例,见假包膜形成6例,见粗大的血管影2例,增强后16例部分实质成分有所强化但不如肾实质强化程度.结论 相对CT而言,MRI对双肾多发AML的诊断具有一定的优势.     

脾脏错构瘤的影像学表现分析

目的探讨脾脏错构瘤的影像学特点,提高对本病的诊断水平。方法回顾性分析10例经病理证实的错构瘤的影像学表现。结果本组脾脏错构瘤9例为单发病灶,1例为多发。.肿瘤体积较大,最大直径为4.5cm导致脾脏局部形态失常。CT扫描脾脏错构瘤为等或稍低密度。磁共振扫描肿块在T1WI及T2WI序列为等或稍低。DWI序列以低信号为主。增强扫描,肿瘤多呈明显、持续性强化,延时后与脾脏实质密度或信号相仿。结论脾脏错构瘤的CT及磁共振扫描具有一定的典型性表现,尤其是磁共振T1WI、T2WI及DWI序列并结合增强扫描,可以与其他脾脏病变区别。     

Localization of pancreatic insulinomas with MR imaging at 0.5 T

OBJECTIVE: To determine the role of MR imaging in the localization of pancreatic insulinomas in patients with clinical and laboratory diagnosis of insulin-producing tumor. MATERIAL AND METHODS: Thirty-one patients presenting with signs and symptoms of pancreatic insulinomas were prospectively included in our study. Twenty-six patients underwent surgery, and pathologic specimens were examined: 5 patients, in whom the initial diagnosis of insulinoma was excluded, were also studied and then followed up. All patients were studied with a high gradient power 0.5 T magnet. Images were evaluated by 2 radiologists blinded to previous investigations, tests and results. RESULTS: MR imaging correctly localized 24 of the 26 insulinomas (2 were false-negative and 1 false-positive) and was correctly negative in the 5 control patients. The interobserver agreement had a kappa value of 0.89. CONCLUSION: MR imaging was accurate in localizing pancreatic insulinomas and as a consequence, patients in our institution are now submitted to surgery directly after the MR examination. Invasive methods are considered only in cases in which, despite clear biochemical results, MR imaging has not demonstrated a pancreatic focal lesion.     

儿童急性局灶性细菌性肾炎的DWI诊断价值

目的分析儿童急性局灶性细菌性肾炎（AFBN）的扩散加权成像（DWI）的影像学表现,并以钆-T1加权像（Gd-T1WI）增强检查为参考标准评估DWI对AFBN的诊断价值。方法2016年2月至2017年12月经临床确诊为AFBN的患儿26例（男患儿12例、女患儿14例）,均行磁共振检查,包括常规磁共振序列（T1WI、T2WI）、DWI及Gd-T1WI增强扫描,以Gd-T1WI增强表现来评定DWI诊断AFBN的灵敏度和特异度。应用Kappa检验和McNemar检验方法统计扫描序列之间的一致性和观察者之间的可重复性。结果26例患儿中有24例在Gd-T1WI增强图像上表现出楔形低灌注区,21例单侧肾脏受累,3例双侧肾脏受累。26例患儿于DWI图像上均发现阳性结果,其中,23例单侧肾脏受累,3例双侧肾脏受累。病变在DWI上表现为高信号,表现扩散系数的平均值较正常肾组织减低。采用DWI检测病变的灵敏度和特异度分别为100%和92%。DWI与Gd-T1WI具有很好的一致性,对病灶的检测差异无统计学意义（k=0.923,P=0.25）。各观察者应用DWI检测病变具有很好的可重复性（k=0.76）。结论DWI序列可明确诊断儿童AFBN,尤其是对肾功能不全、不宜使用对比剂者;其影像表现为楔形或片状高信号影,诊断有效性与MRI增强扫描基本一致。     

磁共振常规成像及DWI对脑膜瘤的诊断价值

目的:比较磁共振常规成像序列(T1WI、T2WI及FLAIR)与DWI对脑膜瘤的检出率,探讨其鉴别病理亚型及良恶性的价值。方法:回顾性分析70例经手术病理证实的脑膜瘤患者的MRI图像,计算不同序列对脑膜瘤的检出率;测量并比较不同病理亚型、不同病理分级的肿瘤实质的平均ADC值和相对ADC值(rADC值)。结果:在T2WI上出现低信号的多是纤维型、过渡型和砂粒体型,出现高信号的多是脑膜上皮型和血管瘤型。在各个序列中,以DWI对脑膜瘤病变的检出率最高(87.1%),T2WI次之(74.3%),T1WI最低(38.6%)。恶性脑膜瘤的囊变发生率(67%)明显高于良性脑膜瘤(22%)。良性组各亚型间、良恶性两组间平均ADC值及rADC值差异均无统计学意义(P>0.05)。结论:DWI可提高对脑膜瘤的检出率,但单独根据ADC值并不能鉴别脑膜瘤的亚型及良恶性。DWI结合常规MRI表现对脑膜瘤亚型及良恶性的鉴别有一定意义。     

Gd- DTPA对肝脏、脾脏及肾脏1.5T MR弥散加权成像的影响

目的:探讨钆喷酸葡胺(Gd-DTPA)在1.5T MR机对正常肝脏、脾脏、肾脏弥散加权成像(DWI)的影响.方法:30例健康体检者在1.5T MR机做上腹部MRI.除常规MR平扫和增强外,在增强前和增强后7min采用b值=500 s/mm2单次激发自旋回波平面成像序列(SE- EPI)分别行DWI扫描.测量增强前后肝脏、脾脏、肾脏在DWI上的信噪比(SNR)、脾脏-肝脏对比噪声比(CNR)、信号强度值和ADC值,并进行统计分析.结果:30例健康体检者检查结果均正常.正常肝脏、脾脏DWI的SNR、CNR、信号强度值、ADC值增强后7min与增强前比较差异无统计学意义(P＞0.05),肾脏DWI SNR、信号强度值、ADC值增强后7min较增强前降低,差异有统计学意义(P＜0.05).结论:Gd-DTPA增强后7min对肝脏、脾脏DWI的图像质量和ADC值无明显影响,而肾脏DWI的图像质量和ADC值降低.     

Diffusion-weighted MRI (DWI) in the oncology patient: value of breathhold DWI compared to unenhanced and gadolinium-enhanced MRI

PURPOSE: To evaluate the feasibility and added value of single breathhold diffusion-weighted (DW) imaging (DWI) in oncology patients undergoing abdominal MRI. MATERIALS AND METHODS: A total of 169 patients with malignancy underwent abdominal MRI at 1.5T, including T1-weighted (T1W), T2-weighted (T2W), and dynamic gadolinium-enhanced imaging. Axial DWI was performed with a single-shot spin-echo (SE) echo-planar imaging (EPI) sequence using a b-value of 500 seconds/mm2. A total of 24 slices were obtained during a 20-second breathhold. Two observers reviewed the conventional MR images for tumor. Next, the DW images were reviewed for additional tumor not depicted on conventional MR images RESULTS: For the 169 patients, additional tumors were noted on the DW images in 77 (0.46) for observer 1 and 67 (0.40) for observer 2. For observer 1 the additional tumor included lymphadenopathy (47), peritoneal metastases (15), renal (1), liver (12), and osseous (2), while for observer 2 the corresponding values were lymphadenopathy (40), peritoneal (12), renal (1), liver (6), osseous (4), and gastrointestinal (1). The DW images resolved as benign findings noted on the conventional MR images in three patients for observer 1 and four patients for observer 2. The conventional MR exam was entirely normal while the DW images showed tumor in 12 (0.07) patients for observer 1 and 10 (0.06) patients for observer 2. CONCLUSION: DWI is feasible in a single breathhold and provides additional clinically important information in oncology patients when added to routine abdominal MR sequences.     

Monitoring therapeutic responses of primary bone tumors by diffusion-weighted image: initial results

The purpose of our study was to investigate whether quantitative diffusion-weighted images (DWI) were useful for monitoring the therapeutic response of primary bone tumors. We encountered 18 osteogenic and Ewing sarcomas. Magnetic resonance (MR) images were performed in all patients before and after therapy. We measured the apparent diffusion coefficient (ADC) values, contrast-to-noise ratio (CNR), and tumor volume of the bone tumors pre- and posttreatment. We determined change in ADC value, change in CNR on T2-weighted images (T2WI), change in CNR on gadopentetate dimeglumine (Gd)-T1-weighted images (Gd-T1WI), and change in tumor volume. The bone tumors were divided into two groups: group A was comprised of tumors with less than 90% necrosis after treatment and group B of tumors at least with 90%. Changes in ADC value, tumor volume, and CNR were compared between the groups. Change in the ADC value was statistically greater in group B than that in the group A (p=0.003). There was no significant difference in the changes in CNR on T2WI (p=0.683), in CNR on Gd-T1WI (p=0.763), and tumor volume (p=0.065). The ADC value on DWI is a promising tool for monitoring the therapeutic response of primary bone sarcomas.     

Role of dynamic contrast-enhanced and diffusion weighted MRI in evaluation of necrosis of hepatocellular carcinoma after chemoembolization

Purpose

The purpose of this study is to evaluate the role of dynamic contrast enhanced and diffusion weighted MRI in the assessment of response and necrosis in the treatment of hepatocelluar carcinoma after transcatheter arterial chemoembolization (TACE).

Subjects and methods

Precontrast T1, T2, STIR, Dynamic contrast enhanced and respiratory triggered diffusion weighted MR images (b factor, 500, 1000 s/mm² obtained in 50 patients with hepatocellular carcinoma who underwent transarterial hepatic chemoembolization). Diffusion-weighted MR images, gadolinium-enhanced MR images after TACE were assigned confidence levels for postoperative HCC recurrence. The sensitivity, specificity, PPV, NPV and overall agreement were calculated for both the dynamic and the DWI images. Apparent diffusion coefficients (ADCs) were calculated searching for a cut off value using the ROC curve.

Results

Dynamic MRI had a sensitivity of 90.5%, a specificity of 96.6%, a positive predictive value of 95%, a negative predictive value of 93.3% and an overall agreement of 94% compared to 100%, 65.5%, 67.7%, 100% and 80% respectively of diffusion weighted imaging.The difference between the malignant and benign groups’ ADC variables was statistically significant P value 0.006.The ROC curve showed that the area under the curve is C = 0.728 with SE = 0.075 and 95% CI from 0.582 to 0.874.

Conclusion

Diffusion weighted MR imaging has lower specificity compared to dynamic MRI with increased false positives. We suggest that increase is due to intralesional hemorrhage or liquefactive necrosis causing diffusion restriction. Diffusion weighted imaging may act as a supplementary sequence to compensate the dynamic MRI in patients who could not hold their breath adequately.