磁共振扩散加权成像在兔VX2肝移植瘤研究中的应用价值

目的 探讨兔VX2肝移植瘤模型磁共振成像(MRI)及扩散加权成像(DWI)的成像参数及图像特征.方法 将传代兔瘤块种植到30只新西兰纯种大白兔的肝左叶,建立兔VX2肝移植瘤模型.接种后用二维超声监测肿瘤长至1～2 cm大小,用头线圈进行MRI成像及DWI检查.结果 肿瘤的接种成功率为100%,2周后可在B超下监测到肿瘤.2～3周肿瘤生长最旺盛,其体积迅速增大.T1WI肿瘤呈稍低信号或等信号,T2WI呈不均匀高信号;增强初期可见肿瘤明显强化,后强化程度较前减低,与肝实质强化程度相近.DWI扩散敏感因子(b值)在350、550 s/mm2和1000 s/mm2时,对应的肝组织和肿瘤组织的ADC值分别为(3.0732±0.5326)±10-3mm2/8和(1.7900 4-0.5310)×10-3mm2/s;(2.7204±0.4726)× 10-3mm2/s和(1.5611±0.2007)±10-3mm2/s;(2.0843±0.3312)×10-3mm2/s和(1.2000±0.2148)×10-3mm2/s.b值增大,肝脏组织和肿瘤组织ADC值减小.结论 随着b值增大,肝组织和肿瘤病灶ADC值呈下降趋势.b值大小影响DWI上肿瘤的显示及信号强度.     

兔VX2瘤磁共振成像技术的探讨

目的:探讨临床型磁共振成像仪用于动物实验成像扫描参数的优化。材料和方法:利用1.5T磁共振成像仪对不同部位接种的52只兔VX2肿瘤模型进行常规自旋回波(T1WI,T2WI)及梯度回波扫描,并进行Gd-DTPA和铁剂增强扫描,比较各种序列图像质量并比较不同部位肿瘤/组织对比信噪比。结果:T2WI和增强扫描可以提供较好的肿瘤病灶的组织对比显示。结论:选择适当的成像参数可以在临床型磁共振成像仪上获得较好的动物图像。     

双b值扩散加权成像在脑梗死诊断中的应用

目的:比较双b值DWI对脑梗死体积及ADC值测量的影响,探讨较高b值DWI在脑梗死诊断中的应用价值。方法:回顾性研究30例脑梗死患者,年龄44～84岁,平均67岁,发病时间3～6d,DWI取b值1000和2000s/mm2,分析脑梗死DWI及ADC图,测量兴趣区与对侧正常部位的扩散系数(ADC)并计算相对扩散系数(rADC),测量并计算梗死灶体积。结果:急性和亚急性脑梗死灶均扩散受限,DWI呈高信号、ADC图呈低信号。与b值1000s/mm2相比,b值2000s/mm2DWI示脑灰白质对比度增加,病灶显示更清晰,还能发现新病灶。不同b值下rADC比较没有统计学意义(P=0.884,P>0.05),同侧ADC有统计学意义(P=0.005,P<0.05);对侧ADC有显著统计学意义(P<0.001)。较高b值下梗死体积较低b值增加,且有统计学意义(P=0.04,P<0.05)。结论:DWI是检测脑梗死的重要技术手段,rADC不受b值影响,rADC降低可指导脑梗死诊断;较高b值DWI上脑梗死灶体积测量更准确,有利于观察病灶演变和指导临床治疗。     

兔VX2肝移植瘤TACE治疗前后ADC值与细胞密度的相关性研究

目的：探讨兔VX2肝移植瘤模型TACE治疗前后磁共振扩散加权成像的ADC值与细胞密度的相关性研究。方法：建立兔VX2肝移植瘤动物模型,并随机分为对照组（n=10）和TACE组（n=10）。接种后用二维超声监测肿瘤生长至1～2cm大小,对照组经肝动脉插管给予生理盐水10ml;TACE组给予超液化碘油2mg/kg和阿霉素2mg／kg。介入术前和术后第7天（处死动物前）行DWI检查,观察介入治疗前后肿瘤的磁共振信号及表观扩散系数（ADC值）变化情况。据常规HE染色计算细胞密度,分析肿瘤治疗前后的ADC值和细胞密度的变化及其相关性。结果：对照组不同b值所对应正常肝组织的ADC值明显高于肿瘤组织的ADC值（P〈0．05）,对照组在注人生理盐水前后的ADC值差别无统计学意义（P〉0．05）,肿瘤组织的ADC值与细胞密度呈负相关关系（P〈0．05）。TACE组介入治疗前ADC值高于治疗后的ADC值,差别有统计学意义（P〈0．05）,肿瘤TACE术后ADC值与细胞密度存在负相关性（P〈0．05）,且介入术后TACE组肿瘤细胞密度较对照组降低（P〈0．05）。结论：肿瘤组织与正常肝脏ADC值存在显著差异,ADC值能反映出肿瘤治疗前后组织微观结构的改变,可用于评估肿瘤增殖情况及治疗疗效。     

背景信号抑制扩散加权成像对兔VX2肝移植瘤疗效评价的实验研究

目的探讨磁共振背景信号抑制扩散加权体部成像(MR DWIBS)在经肝动脉化疗栓塞术(TACE)联合静脉注射血管生成抑制剂内皮抑素(ES)治疗VX2肝移植瘤疗效评价中的作用。材料与方法荷瘤兔随机分为两组,每组8只。ES组经耳缘静脉注射ES0.7 mg.kg-1.d-1,连续应用12天;TACE+ES组经肝动脉给予超液化碘油0.2 ml/kg和阿霉素2 mg/kg,并经耳缘静脉注射内皮抑素0.7 mg.kg-1.d-1,连续应用12天。两组均于治疗前后行MR DWIBS检查,分别测量各组肿瘤组织在不同时间点的表观扩散系数(ADC),并评价DWIBS及DWIBS原始图经3D MIP重组及黑白翻转获得类PET图像的图像特征。结果 ADC值从治疗后第3天起即有变化,TACE+ES组ADC值在治疗后第3、7、13天均高于ES组并有统计学意义(P<0.05)。结论 DWIBS可以在治疗早期动态评价TACE术联合静脉注射血管生成抑制剂ES对VX2肝移植瘤的疗效。DWIBS结合ADC值的定量测量及类PET大范围成像,可以无创性活体评价药物抗肿瘤的治疗反应,为肿瘤的诊断、分期、疗效评价提供有价值的信息。     

兔肢体VX2软组织肿瘤MR扩散加权成像

目的:建立兔肢体软组织肿瘤模型,探讨MR扩散加权成像在软组织肿瘤诊断中应用的可行性及适用于软组织肿瘤成像的合适的b值。方法:25只新西兰大白兔(月龄2～3个月,体重1.5～2.0kg,雌雄不限),将肿瘤瘤株种植在左前上肢内侧。在种植瘤株后2～3周使用1.5T磁共振仪行常规MRI及DWI检查,b值取200、400、600、800和1000s/mm2。在MRI检查后3～4周分批处死荷瘤兔,取出肿瘤组织,观察肿瘤的大体形态及病理学表现。结果:肿瘤成瘤率96%(24/25)。种瘤后14、21和28天,肿瘤直径分别约为2.0、4.0和5.5cm。肿瘤直径比较小(14天)时,质地硬,肿瘤坏死、瘤周水肿很少见。在常规T1WI上肿瘤实质多呈等信号,瘤内出血少见;T2WI上肿瘤实质为不均匀高信号,肿瘤中央和瘤周可见信号更高的坏死、水肿区;增强后肿瘤实质明显强化,肿瘤边缘强化更显著。DWI图像上,当b值较小时(200s/mm2)受T2透过效应影响明显,b值比较大时(1000s/mm2)图像信噪比下降明显,b值为600和800s/mm2时,图像质量比较好;b值为200、400、600、800和1000s/mm2时肿瘤的ADC值分别为(1.56±0.11)、(1.32±0.12)、(1.25±0.10)、(1.19±0.08)和(1.14±0.07)mm2/s;b值为600和800s/mm2时,肿瘤实质的ADC值明显小于坏死区及周围肌肉组织,差异有显著性意义(P<0.005)。结论:DWI可以用于兔肢体VX2软组织肿瘤的观察,b值为600和800s/mm2时可以获得比较好的DWI图像。肿瘤组织、肌肉组织及坏死组织的ADC值明显不同,DWI在软组织肿瘤的诊断和预后评估等方面具有广阔的应用前景。     

磁共振扩散加权成像在肝脓肿诊断中的价值

目的:探讨肝脓肿的磁共振扩散加权成像(DWI)影像特征,提高其影像诊断水平.方法:回顾性分析20例患者中30个肝脓肿的常规磁共振扫描加动态增强扫描及DWI图像,表观扩散系数(ADC)值定量分析肝脓肿的脓腔、脓肿壁及周围正常肝组织.结果:ADC图上,30个肝脓肿的脓腔中24个呈明显低信号,2个等信号,4个明显高信号,ADC值为(0.69～2.62)×10-3 mm2/s.30个肝脓肿中,8个未见明显脓肿壁形成; 22个脓肿壁在DWI图像上呈多样信号,在ADC图上均呈稍高信号,平均ADC值为(1.70 ± 0.23)×10-3 mm2/s.结论:肝脓肿的脓腔在DWI上常表现为明显高信号,ADC值较低;但部分脓腔ADC值较高,与肿瘤囊变坏死区难以鉴别;脓肿壁在ADC图上呈稍高信号的影像学特征有助于其诊断和鉴别诊断.     

磁共振扩散加权成像在肝纤维化诊断中的应用

肝炎-肝纤维化-肝硬化-肝细胞癌是逐渐发展的病理过程,其中肝纤维化是唯一可逆性阶段。有关肝纤维化早期诊断和治疗的研究是当今临床及医学影像学研究的热点和难点。磁共振扩散加权成像(DWI)是近年开发并趋向成熟的功能成像技术,尤其对肝纤维化有望成为其早期诊断无创而有效的手段。现就DWI的成像方法及其对肝纤维化病理分级、分期等应用现状予以综述。     

磁共振扩散加权成像在肝纤维化诊断中的应用

肝炎-肝纤维化-肝硬化-肝细胞癌是逐渐发展的病理过程,其中肝纤维化是唯一可逆性阶段。有关肝纤维化早期诊断和治疗的研究是当今临床及医学影像学研究的热点和难点。磁共振扩散加权成像（DWI）是近年开发并趋向成熟的功能成像技术,尤其对肝纤维化有望成为其早期诊断无创而有效的手段。现就DWI的成像方法及其对肝纤维化病理分级、分期等应用现状予以综述。     

磁共振扩散成像及磁敏感加权成像在脊髓损伤中的应用

目前,脊髓MR成像常规检查是诊断脊髓损伤的最佳手段,能清楚地显示受损伤脊髓形态及信号改变,以此明确疾病,但是当MRI常规检查出现信号改变时往往提示脊髓损伤严重,并非病变的早期,使得病人错过最佳治疗时期。而MR扩散加权成像(DWI)和磁敏感加权成像(SWI)对脊髓损伤的早期诊断、治疗和预后均具有重要价值。对DWI及SWI在急慢性脊髓损伤中的应用情况及研究进展进行综述。     

Diffusion weighted MR imaging of pancreatic islet cell tumors

Purpose

The aim of our study is to demonstrate the feasibility of body diffusion weighted (DW) MR imaging in the evaluation of pancreatic islet cell tumors (ICTs) and to define apparent diffusion coefficient (ADC) values for these tumors.

Materials and methods

12 normal volunteers and 12 patients with histopathologically proven pancreatic ICT by surgery were included in the study. DW MR images were obtained by a body-phased array coil using a multisection single-shot echo planar sequence on the axial plane without breath holding. In addition, the routine abdominal imaging protocol for pancreas was applied in the patient group. We measured the ADC value within the normal pancreas in control group, pancreatic ICT, and surrounding pancreas parenchyma. Mann-Whitney U-test has been used to compare ADC values between tumoral tissues and normal pancreatic tissues of the volunteers. Wilcoxon Signed Ranks Test was preferred to compare ADC values between tumoral tissues and surrounding pancreatic parenchyma of the patients.

Results

In 11 patients out of 12, conventional MR sequences were able to demonstrate ICTs succesfully. In 1 patient an indistinct suspicious lesion was noted at the pancreatic tail. DW sequence was able to demonstrate the lesions in all of the 12 patients. On the DW images, all ICTs demonstrated high signal intensity relative to the surrounding pancreatic parenchyma. The mean and standard deviations of the ADC values (×10⁻³ mm²/s) were as follows: ICT (n = 12), 1.51 ± 0.35 (0.91-2.11), surrounding parenchyma (n = 11) 0.76 ± 0.15 (0.51-1.01) and normal pancreas in normal volunteers (n = 12), 0.80 ± 0.06 (0.72-0.90). ADC values of the ICT were significantly higher compared with those of surrounding parenchyma (p < 0.01) and normal pancreas (p < 0.001).

Conclusion

DW MR imaging does not appear to provide significant contribution to routine MR imaging protocol in the evaluation of pancreatic islet cell tumors. But it can be added to MR imaging protocol to detect the lesion in a limited number of patients with clinical suspicion for pancreatic ICT with negative or suspicious imaging findings.     

Intraprocedural diffusion‐weighted PROPELLER MRI to guide percutaneous biopsy needle placement within rabbit VX2 liver tumors

Purpose

To test the hypothesis that diffusion‐weighted (DW)‐PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) magnetic resonance imaging (MRI) can be used to guide biopsy needle placement during percutaneous interventional procedures to selectively target viable and necrotic tissues within VX2 rabbit liver tumors.

Materials and Methods

Our institutional Animal Care and Use Committee approved all experiments. In six rabbits implanted with 15 VX2 liver tumors, baseline DW‐PROPELLER images acquired prior to the interventional procedure were used for apparent diffusion coefficient (ADC) measurements. Next, intraprocedural DW‐PROPELLER scans were performed with needle position iteratively adjusted to target viable, necrotic, or intermediate border tissue regions. DW‐PROPELLER ADC measurements at the selected needle tip locations were compared with the percentage of tumor necrosis qualitatively assessed at histopathology.

Results

DW‐PROPELLER images demonstrated intratumoral tissue heterogeneity and clearly depicted the needle tip position within viable and necrotic tumor tissues. Mean ADC measurements within the region‐of‐interest encompassing the needle tip were highly correlated with histopathologic tumor necrotic tissue assessments.

Conclusion

DW‐PROPELLER is an effective method to selectively position the biopsy needle tip within viable and necrotic tumor tissues. The DW‐PROPELLER method may offer an important complementary tool for functional guidance during MR‐guided percutaneous procedures. J. Magn. Reson. Imaging 2009;30:366–373. © 2009 Wiley‐Liss, Inc.     

兔肝VX2瘤MR扩散加权成像与病理的动态对照研究

目的探讨兔肝VX2瘤种植后MR扩散加权成像（OWI）的价值、动态特征及其病理机制。方法新西兰大白兔40只，采用开腹下块种植法行肝内VX2瘤种植，其中25只种植1个部位、15只种植2个部位。对全部种植兔于种植后第7、14、21天行DWI和第7、14天行常规MRI（T1WI、T2WI）检查，并对其中10个肿瘤标本行病理检查。结果种植后第7天DWI、T1WI、T2WI病灶发现率分别为78．7％（37／47）、10．7％（3／28）、53．6％（15／28），差异有统计学意义（χ^2=32．61，P〈0．01）；第14天分别为95．7％（45／47）、54．3％（19／35）、82．9％（29／35），差异有统计学意义（χ^2=21．50，P〈0．01）。种植后7d肿瘤生长较慢，内部尚未坏死，信号均匀；约14d后肿瘤生长开始加速，但此时内部坏死仍不明显，呈等或不均匀信号；第21天时肿瘤内部出现明显坏死，DWI上呈不均匀信号，成活肿瘤部分呈高信号，肿瘤坏死部分呈低信号，而囊变、液化部分呈高信号；从第7天至第21天。肿瘤边界逐渐由不清楚至清楚，内部信号由均匀至不均匀。敏感梯度因子（b）值为100s／，咖112时，种植后第7、14及21天，肿瘤周围表观扩散系数（ADC）值分别为（2．18±0．29）×10^-3、（1．96±0．33）×10^-3与（1．80±0．35）×10^-3mm^2／s，而肿瘤周围正常肝实质ADC值分别为（2．82±0．36）×10^-3、（2．61±0．40）×10^-3与（2．75±0．43）×10^-3mm^2／s。结论VX2瘤成活与坏死、囊变部分DWI具有典型表现，同时DWI在早期发现病变方面有重要潜在的价值。     

Diffusion weighted imaging of liver lesions suspect for metastases: Apparent diffusion coefficient (ADC) values and lesion contrast are independent from Gd-EOB-DTPA administration

Purpose

Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) enhanced liver MRI is widely used for detection and differentiation of focal liver lesions. Diffusion weighted imaging (DWI) including apparent diffusion coefficient (ADC) measurements is increasingly utilised as a fast and, with limitations, quantitative method for liver lesion detection and characterisation. Herein we investigate whether the administration of Gd-EOB-DTPA affects DWI.

Materials and methods

31 consecutive patients referred to standardised liver MRI (1.5 T, Gd-EOB-DTPA, 0.025 mmol/kg) were retrospectively reviewed. All underwent a breathhold DWI sequence before and after contrast agent administration (EPI-DWI, TR/TE (effective): 2100/62 ms, b-values: 0 and 800 s/mm²). Patients with previously treated liver lesions were excluded. Signal intensity of lesion, parenchyma and noise on DWI images as well as the ADC value were measured after identification by two observers in consensus using manually placed regions of interest. The reference standard was imaging follow-up determined separately by two radiologists. Data analysis included signal-to-noise (SNR) ratio and contrast-to-noise ratio (CNR) calculations, comparisons were drawn by employing multiple Bonferroni corrected Wilcoxon signed-rank tests.

Results

50 malignant and 39 benign lesions were identified. Neither SNR, CNR nor ADC values showed significant differences between pre- and postcontrast DWI. Both pre- and postcontrast ADC values differed significantly between benign and malignant lesions (P < 0.001).

Conclusion

We did not identify a significant influence of Gd-EOB-DTPA on DWI of liver lesions. This allows for individual tailoring of imaging protocols according to clinical needs.     

磁共振弥散加权成像在肝海绵状血管瘤中的应用价值

目的:分析肝海绵状血管瘤不同b值的MRI弥散加权成像特性,提高病变检出率和图像质量。方法:对连续的MRI平扫和增强明确诊断的13例肝海绵状血管瘤,比较弥散加权成像b值分别为0s/mm2,100s/mm2和700s/mm2时的特征。结果:MRI平扫和增强分别显示34个(87%)和29个(74%)病变;在弥散加权成像中,b为0s/mm2时显示21个(54%),小的病变与血管和胆管易混淆;b为100s/mm2时显示39个(100%),病变与周围组织界限清晰;b为700s/mm2时显示33个(85%)。正常肝组织的信噪比以b值为100s/mm2最高(19.15±0.85);病变的信噪比以b值为0s/mm2时最高(12.89±0.96);病变与周围正常肝组织的对比度以b为700s/mm2时最低(0.37±0.02)。结论:MRI弥散加权成像进一步提高了对肝海绵状血管瘤的敏感性,以b值为100s/mm2时,病变检出率和图像质量最高。     

MR扩散加权成像在宫颈癌诊断和分期中的应用价值

目的 探讨磁共振扩散加权成像（DWI）在宫颈癌诊断的敏感性、分期的准确性及盆腔淋巴结转移的检出率和定性准确率中的应用价值.方法 回顾性分析经术后病理证实的98例宫颈癌患者的影像资料,比较DWI联合常规MRI序列与单纯常规MRI序列在宫颈癌诊断、分期及盆腔淋巴结转移方面的差异.结果 DWI联合常规MRI序列对Ⅰb期的漏诊率（1/20）低于单纯常规MRI序列漏诊率（5/20）.DWI联合常规MRI序列对Ⅱb期分期准确率（21/23）高于单纯常规MRI序列准确率（14/23）;其余各期分期,两者无明显差异.DWI联合常规MRI序列对盆腔淋巴结转移的检出率（135/148）和定性准确率（76/82）均高于单纯常规MRI序列的检出率（101/148）和定性准确率（56/82）.结论 相对于常规MRI序列,DWI联合常规MRI序列对宫颈癌的诊断更敏感,Ⅱb期分期更准确,盆腔淋巴结检出率和定性准确率更可靠.     

磁共振DWI在判断小儿颅内肿瘤分级中的价值

目的：探讨磁共振DWI在判断小儿颅内肿瘤分级中的价值。方法：回顾性分析60例经病理证实小儿颅内肿瘤的扩散加权成像（DWI）及ADC图像,包括WHOⅠ级19例,Ⅱ级17,Ⅲ级14例,Ⅳ级10例。测量肿瘤实质部分及正常脑白质的ADC值,经统计学分析各组之间的差异。结果：肿瘤实质ADC及实质/白质值（rADC）测量,Ⅰ-Ⅳ级肿瘤的ADC值分别为（1.30±0.35）×10^-3（、1.06±0.23）×10-3、（0.91±0.15）×10^-3和（0.63±0.11）×10^-3mm^2/s,rADC分别为1.69±0.49、1.32±0.28、1.20±0.29和0.79±0.19,除Ⅱ、Ⅲ级肿瘤间不存在统计学差异外,其余各组间差异均有统计学意义。Ⅰ-Ⅱ和Ⅲ-Ⅳ级组肿瘤ADC值分别为（1.24±0.34）和（0.87±0.28）×10^-3mm^2/s,rADC分别为1.60±0.45和1.17±0.38,两组差异有统计学意义（P〈0.05）,Ⅰ-Ⅱ级组高于Ⅲ-Ⅳ级组。结论：DWI对于小儿颅内肿瘤级别的判断有一定的帮助,而ADC或rADC值,特别是后者能较为可靠地鉴别小儿常见颅内肿瘤的级别。