扩散加权成像在卵巢肿瘤中的应用

扩散加权成像(DWI)是目前唯一能够检测生物组织内水分子扩散运动的无创方法 ,该种扩散运动可以通过表观扩散系数(ADC)来量化分析。扩散峰度成像(DKI)、体素内不相干运动(IVIM)成像、背景抑制扩散加权全身成像(DWIBS)等DWI新技术用于卵巢肿瘤的评估提高了卵巢肿瘤影像诊断的准确性。综述DWI及其新技术在卵巢肿瘤定性诊断、分期、疗效评估、预后判断中的作用及其潜在缺陷。     

Role of combined DWIBS/3D-CE-T1w whole-body MRI in tumor staging: Comparison with PET-CT

Objectives

To assess the diagnostic performance of whole-body magnetic resonance imaging (WB-MRI) by diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) in malignant tumor detection and the potential diagnostic advantages in generating fused DWIBS/3D-contrast enhanced T1w (3D-CE-T1w) images.

Methods

45 cancer patients underwent 18F-FDG PET-CT and WB-MRI for staging purpose. Fused DWIBS/3D-CE T1w images were generated off-line. 3D-CE-T1w, DWIBS images alone and fused with 3D-CE T1w were compared by two readers groups for detection of primary diseases and local/distant metastases. Diagnostic performance between the three WB-MRI data sets was assessed using receiver operating characteristic (ROC) curve analysis. Imaging exams and histopathological results were used as standard of references.

Results

Areas under the ROC curves of DWIBS vs. 3D-CE-T1w vs. both sequences in fused fashion were 0.97, 0.978, and 1.00, respectively. The diagnostic performance in tumor detection of fused DWIBS/3D-CE-T1w images were statistically superior to DWIBS (p < 0.001) and 3D-CE-T1w (p ≤ 0.002); while the difference between DWIBS and 3D-CE-T1w did not show statistical significance difference. Detection rates of malignancy did not differ between WB-MRI with DWIBS and 18F-FDG PET-CT.

Conclusion

WB-MRI with DWIBS is to be considered as alternative tool to conventional whole-body methods for tumor staging and during follow-up in cancer patients.     

Diagnostic performance of diffusion-weighted magnetic resonance imaging in esophageal cancer

The purpose of this study was to assess the value of diffusion-weighted magnetic resonance imaging (DWI) in detecting esophageal cancer and assessing lymph-node status, compared with histopathological results. DWI was prospectively performed in 24 consecutive patients with esophageal cancer, using the diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) sequence. DWIBS images were fused with T2-weighted images, and independently and blindly evaluated by three board-certified radiologists, regarding primary tumor detectability and lymph-node status. Apparent diffusion coefficients (ADCs) of the primary tumor and lymph nodes were also measured. Average primary tumor detection rate was 49.4%, average patient-based sensitivity and specificity for the detection of lymph-node metastasis were 77.8 and 55.6%, and average lymph-node group-based sensitivity and specificity were 39.4 and 92.6%. There were no interobserver differences among the three readers (P < 0.0001). Mean ADC of detected primary tumors was 1.26 ± 0.29×10⁻³ mm²/s. Mean ADC of metastatic lymph nodes (1.46 ± 0.35×10⁻³ mm²/s) was significantly higher (P < 0.0001) than that of nonmetastatic lymph nodes (1.15 ± 0.24 mm²/s), but ADCs of both groups overlapped. In conclusion, this study suggests that DWI only has a limited role in detecting esophageal cancer and nodal staging.     

Whole-body diffusion-weighted imaging: technical improvement and preliminary results

PURPOSE: To optimize the free-breathing whole-body diffusion-weighted imaging (WB-DWI) protocol by using the short TI inversion-recovery diffusion-weighted echo-planar imaging (STIR-DWEPI) sequence and the built-in body coil. Additionally, to evaluate the feasibility of tumor screening using high-resolution three-dimensional (3D) maximum intensity projection (MIP) images. MATERIALS AND METHODS: The prescan procedure of STIR-DWEPI was modified using the data from 30 volunteers. During each exam, an optimized center frequency (CF) was used to minimize the slice offsets in consecutive scan stations. Prescan time was reduced from 50 seconds to 20 seconds with improved station profile. Total scan time was 30 minutes for five stations and 1.2 m coverage. A total of 30 patients with histologically-proven malignant disease were scanned under the final protocol using a built-in body coil. The image quality and the degree of background body signal suppression were assessed. RESULTS: Free-breathing WB-DWI was 100% successfully performed in all patients, without slice misregistration, fat contamination, significant distortion, or nonuniformity. The reconstructed 3D-MIP images were adequate to depict malignant lesions in all 30 patients. The results of WB-DWI were found to be comparable to those of single-photon emission computed tomography (SPECT) and positron emission tomography (PET). CONCLUSION: Stable and high-resolution WB-DWI is feasible using the technical improvements described in this study. WB-DWI might have important clinical value for the detection of primary and metastatic malignancies within the whole body. The potential for diagnosis and therapeutic assessment of tumors should be further assessed in a larger patient cohort.     

Central nervous system aspergillosis: magnetic resonance imaging, diffusion-weighted imaging, and magnetic resonance spectroscopy features

Aspergillus infection is invasive in nature in the immunosuppressed population and disseminates throughout the body, with the brain being a common site. Conventional magnetic resonance imaging (MRI) combined with diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) play a life-saving role in the early diagnosis and treatment monitoring of this potentially fatal infection. We present MRI, DWI, and MRS findings of a case of central nervous system aspergillosis with treatment follow-up.     

Extracranial applications of diffusion-weighted magnetic resonance imaging

Diffusion-weighted MRI has become more and more popular in the last couple of years. It is already an accepted diagnostic tool for patients with acute stroke, but is more difficult to use for extracranial applications due to technical challenges mostly related to motion sensitivity and susceptibility variations (e.g., respiration and air-tissue boundaries). However, thanks to the newer technical developments, applications of body DW-MRI are starting to emerge. In this review, we aim to provide an overview of the current status of the published data on DW-MRI in extracranial applications. A short introduction to the physical background of this promising technique is provided, followed by the current status, subdivided into three main topics, the functional evaluation, tissue characterization and therapy monitoring.     

Whole-body magnetic resonance imaging and FDG-PET/CT for lymphoma staging: Assessment of patient experience

Purpose

To compare patient experience of whole-body MRI and FDG-PET/CT performed for lymphoma staging.

"Prominent ear sign" on diffusion-weighted magnetic resonance imaging in relapsing polychondritis

Relapsing polychondritis is a rare autoimmune disease characterized by recurrent inflammation of cartilage in multiple sites of the body, including the auricles. Central nervous system involvement appears rare. We encountered a case of relapsing polychondritis with encephalitis that could be diagnosed by the unique appearance of the auricle with signal hyperintensity on diffusion-weighted magnetic resonance imaging.     

磁共振在食管癌原发灶放化疗近期疗效评价中的应用

目的 根据食管癌放化疗前后磁共振扫描结果,结合临床疗效评估,对食管癌原发灶进行疗效判定,并结合原有CT及造影的评价标准,验证磁共振在食管癌放化疗近期疗效评价的可靠性。方法 2010年5月至2014年3月采用三维适形或调强放疗的83例食管癌患者,处方剂量50~64 Gy,中位剂量60 Gy,单次1.8~2.0 Gy,其中34例接受了FP或TP方案的同期化疗,放疗前后均行食管钡餐造影、胸及上腹CT、磁共振弥散加权成像（DWI）检查。依据1989版和2013版食管癌近期疗效评价标准进行疗效评价和比较,同时依据患者疗末病变区域DWI高信号表达情况进行疗效界定和亚组分析。结果 依据1989版及2013版近期疗效评价标准,全组完全缓解和部分缓解分别为：45例（54.2%）和38例（45.8%）;35例（42.2%）和48例（57.8%）。两种评价标准中完全缓解组1~5年的局部控制率和生存率均好于部分缓解组。治疗后病变区域DWI高信号完全消失者48例（将其界定为完全缓解）,呈稍高信号表达者25例、高信号表达者10例（部分缓解）,前者1~5年的局部控制率和生存率均好于后者（χ²=6.125、11.652,P<0.05）。与2013版近期疗效评价标准相比,一致性为中等（Kappa值=0.478）。依据钡餐造影、CT扫描、DWI检查综合评价,3项均达完全缓解标准者25例,部分缓解为58例,前者1~5年的局部控制率和生存率均高于后者（χ²=5.559、10.014,P<0.05）。结论 基于钡餐造影和CT扫描的近期疗效评价标准可较好地提示食管肿瘤局部控制情况;DWI可为食管癌治疗反应评价提供直观、量化的参考信息,疗末食管病变局部仍有高信号表达预示极高的复发风险。用3种影像学技术综合评价疗效更全面、客观、准确。     

Diffusion-weighted magnetic resonance imaging in autoimmune pancreatitis

Purpose  The aim of this study was to investigate the usefulness of diffusion-weighted magnetic resonance imaging (DWI MRI) for the diagnosis and evaluation of autoimmune pancreatitis (AIP). Materials and methods  A total of 4 consecutive patients with AIP, 5 patients with chronic alcoholic pancreatitis (CP), and 13 patients without pancreatic disease (controls) were studied. DWI was performed in the axial plane with spin-echo echo-planar imaging single-shot sequence. Apparent diffusion coefficients (ADCs) were measured in circular regions of interest in the pancreas. In AIP patients, abdominal MRI was performed before, and 2–4 weeks after steroid treatment. Follow-up study was performed chronologically for up to 11 months in two patients. The correlation between ADCs of the pancreas and the immunoglobulin G4 (IgG4) index (serum IgG4 value/serum IgG4 value before steroid treatment) was evaluated. Results  In the AIP patients, DWI of the pancreas showed high signal intensity, and the ADCs of the pancreas (mean ± SD: 0.97 ± 0.18 × 10⁻³ mm²/s) were significantly lower than those in patients with CP (1.45 ± 0.10 × 10⁻³ mm²/s) or the controls (1.45 ± 0.16 × 10⁻³ mm²/s) (Mann-Whitney U-test, P < 0.05). In one AIP patient with focal swelling of the pancreas head that appeared to be a mass, DWI showed high signal intensity throughout the pancreas, indicating diffuse involvement. The ADCs of the pancreas and IgG4 index were significantly inversely correlated (Spearman’s rank correlation coefficient, r _s = −0.80, P < 0.05). Conclusion  Autoimmune pancreatitis showed high signal intensity on DWI, which improved after steroid treatment. ADCs reflected disease activity. Thus, diffusion-weighted MRI might be useful for diagnosing AIP, determining the affected area, and evaluating the effect of treatment. T. Taniguchi and H. Kobayashi contributed equally to this study     

Discordance of motion artifacts on magnetic resonance imaging in Creutzfeldt-Jakob disease: comparison of diffusion-weighted and conventional imaging sequences

Purpose Motion artifact is problematic in the diagnosis of Creutzfeldt-Jakob disease (CJD) because of dementia. The purpose was to compare the occurrence of this artifact between a diffusion-weighted (DW) magnetic resonance (MR) imaging sequence and conventional sequences. Materials and methods Ten MR examinations comprising T2-weighted, T1-weighted, DW, and fluid-attenuated inversion recovery imaging in seven CJD patients were retrospectively evaluated. The occurrence of motion artifacts on each sequence were assessed, and the examination was classified into four groups as follows: group A, motion artifact not revealed on DW imaging but revealed on one or more other sequences; group B, revealed on DW imaging and one or more other sequences; group C, not revealed on any sequences; and group D, revealed on DW imaging but not on any other sequences. Results The 10 MR examinations were classified as eight group A (80%), one B (10%), one C (10%), and zero D (0%). Conclusion Motion artifacts are likely to occur in any conventional imaging sequences in CJD, but the fast-imaging ability of DW imaging can reduce this artifact. The combination of an absence of motion artifact on DW imaging and the presence on conventional sequences may be one of the frequent findings of CJD.     

磁共振弥散加权成像在食管癌放疗疗效评价中的应用价值探讨

目的 探讨磁共振弥散加权成像（DWI）在食管癌放疗疗效评价中的应用价值。方法 74例食管鳞癌患者接受三维适形放疗或调强放疗, 处方剂量56~61.2 Gy,单次1.8~2 Gy。放疗前、放疗末及放疗后1~3个月行DWI检查,用食管钡餐造影、DWI高信号消失情况、表面弥散系数（ADC）对放疗疗效进行评价,并与预后相结合进行生存分析。结果 中位随访时间22个月,随访率98.7%。放疗末DWI高信号消失组23例,1、2年生存率分别为82.6%、68.5%;放疗后1~3个月消失组40例,1、2年生存率分别为74.5%、49.2%;始终未消失组11例,1年生存率9.1%,生存期最长17个月（χ²=39.78,P<0.05）。造影评价完全缓解47例中,20例放疗末DWI高信号消失;23例放疗后1~3个月消失,其1、2年生存率分别为80%、64.3%和86.7%、66.1%;高信号始终未消失4例,生存期4~7个月（χ²=37.80,P<0.05）。造影评价为部分缓解的26例中,3例放疗末高信号消失;17例放疗后1~3个月高信号消失,1、2年生存率为58.8%、19.3%、高信号始终未消失6例,生存期4~17个月（χ²=11.72,P<0.05）。患者正常食管组织的ADC₀、食管肿瘤放疗前的ADC₁及放疗末的ADC₂值分别为（3.12±0.53）、（1.64±0.48）、（2.65±0.58）s/mm²,疗末ADC₂/ADC₀≤90%组（40例）与>90%组（34例）1、2年生存率分别为56.4%、28.2%和83.1%、75.7%（χ²=10.35,P<0.05）。放疗末肿瘤区域ADC值为独立预后影响因素（OR=0.060,P<0.05）。结论 利用磁共振弥散加权成像检查对食管癌放疗疗效进行评价可以较好地提示预后,弥补食管钡餐造影在疗效评价中的不足,疗后肿瘤区域ADC值大小为独立预后影响因素。     

Sandwich sign of Borrmann type 4 gastric cancer on diffusion-weighted magnetic resonance imaging

Objective

To assess the appearance of Borrmann type 4 (BT-4) gastric cancer on diffusion-weighted magnetic resonance imaging (DWI) and to investigate the potential of qualitative and quantitative DW images analysis to differentiate BT-4 gastric cancer from poorly distended normal stomach wall.

Materials and methods

DWI was performed on 23 patients with BT-4 gastric cancer and 23 healthy volunteers. The signal characteristics and correlated histopathological basis of the cancers on DWI were investigated. The contrast-to-noise ratios (CNR) of cancer were compared between DWI and T1WI/T2WI_. The thickness and apparent diffusion coefficient (ADC) of cancer and normal stomach wall were compared.

Results

All of the gastric cancers displayed hyperintensity compared to the nearby normal gastric wall on DWI. A three-layer sandwich sign that demonstrated high signal intensity in the inner and outer layer, and low signal intensity in the intermediate layer was observed in 69.6% of cancers on DWI. The low signal intensity represents the muscularis propria through the comparison with pathology, and it is postulated that scattering distribution of the cancer cells in this layer causes less damage and subsequently less restriction of water movement, which causes the low signal intensity on DWI. The CNR obtained with DWI was higher than that with T1WI and T2WI (P < 0.001). The mean ADC value of BT-4 gastric cancer was significantly lower than the poorly distended normal stomach wall (1.12 ± 0.23 × 10⁻³ mm²/s vs. 1.93 ± 0.22 × 10⁻³ mm²/s, P < 0.01).

Conclusion

DWI can highlight the signals of BT-4 gastric cancer which may present a characteristic three-layer sandwich sign, and ADC values are helpful in the discrimination of gastric cancer from poorly distended stomach wall.     

Intravascular malignant lymphomatosis: diffusion-weighted magnetic resonance imaging characteristics

Intravascular malignant lymphomatosis is an unusual condition in which malignant lymphoma cells form microscopic masses within the blood vessels of the central nervous system. Occlusion of the involved blood vessels can lead to multifocal cerebral infarcts. Diffusion-weighted magnetic resonance imaging (MRI) reveals a subacute infarction pattern (bright high signal intensity on b = 1000 s/mm² images and intermediate apparent diffusion coefficient values) in the cerebral deep white matter. We present MRI findings of a 68-year-old woman with intravascular malignant lymphomatosis involving the cerebral white matter and the thoracic cord.     

正常与退变腰椎间盘磁共振弥散加权成像的对比研究及其临床意义

目的：探讨磁共振弥散加权成像（DWI）及表观弥散系数测量值（ADC值）在腰椎间盘退变中的临床应用价值并对可能影响ADC值的相关因素进行分析。方法：对24例健康志愿者和16例腰腿痛患者进行常规T2WI及DWI扫描检查,进行相关研究。结果：正常腰椎间盘ADC值与年龄、性别、体重指数均无相关性。正常与退变椎间盘平均ADC值分别为（1.82±0.70）×10^-3mm^2/s和（1.22±0.27）×10^-3mm^2/s,正常与退变之间差异具有统计学意义。结论：弥散加权成像ADC测量值对退变椎间盘的诊断有一定的临床价值,利用磁共振弥散加权成像ADC值诊断退变椎间盘时可不考虑年龄、性别和体重指数的影响。     

扩散加权成像对良恶性淋巴结鉴别的研究进展

淋巴结转移与否对于癌症病人的预后、分期及治疗方案的选择极为重要。目前常规MRI依靠淋巴结大小鉴别其良恶性的准确性不高,利用MR功能成像方法鉴别淋巴结良恶性是目前影像学研究的热点。其中扩散加权成像相较其他方法具有诸多优点。近年来非高斯模型包括双指数模型、拉伸指数模型、扩散峰度模型等逐渐应用于临床。现就传统及非高斯模型扩散加权成像在淋巴结良恶性鉴别上的研究现状及价值予以综述。     

Advanced magnetic resonance imaging findings in salivary gland tumors

Salivary gland tumors (SGTs) make up a small portion (approximately 5%) of all head and neck tumors. Most of them are located in the parotid glands, while they are less frequently located in the submandibular glands, minor salivary glands or sublingual gland. The incidence of malignant or benign tumors (BTs) in the salivary glands varies according to the salivary gland from which they originate. While most of those detected in the parotid gland tend to be benign, the incidence of malignancy increases in other glands. The use of magnetic resonance imaging (MRI) in the diagnosis of SGTs is increasing every day. While conventional sequences provide sufficient data on the presence, localization, extent and number of the tumor, they are insufficient for tumor specification. With the widespread use of advanced techniques such as diffusion-weighted imaging, semi-quantitative and quantitative perfusion MRI, studies and data have been published on the differentiation of malignant or BTs and the specificity of their subtypes. With diffusion MRI, differentiation can be made by utilizing the cellularity and microstructural properties of tumors. For example, SGTs such as high cellular Warthin’s tumor (WT) or lymphoma on diffusion MRI have been reported to have significantly lower apparent diffusion values than other tumors. Contrast agent uptake and wash-out levels of tumors can be detected with semi-quantitative perfusion MRI. For example, it is reported that almost all of the pleomorphic adenomas show an increasing enhancement time intensity curve and do not wash-out. On quantitative perfusion MRI studies using perfusion parameters such as Ktrans, Kep, and Ve, it is reported that WTs can show higher Kep and lower Ve values than other tumors. In this study, the contribution of advanced MRI to the diagnosis and differential diagnosis of SGTs will be reviewed.     

磁共振弥散加权成像预测食管癌移植瘤放疗反应的实验研究

目的 探讨磁共振弥散加权成像（DWI）在预测食管癌放疗反应的应用价值。方法 将人食管癌Eca-109裸鼠皮下移植瘤模型按随机数表法分为实验组（14只,接受单次剂量15 Gy 6 MV X射线照射）和对照组（10只,无治疗）,均在实验组照射前及之后的1、6、13 d行DWI检测。比较不同时间点两组表观弥散系数（ADC）值及体积差异。结果 两组ADC值在第1天均下降,在第6、13天时实验组逐渐升高,并高于照射前,而对照组持续下降,两组比较,差异有统计学意义（F=6.178、16.181、58.733,P<0.05）,且ADC值的变化率差异有统计学意义（F=9.038、12.360、35.140,P<0.05）;而照射前两组ADC值差异无统计学意义（P>0.05）。与对照组比较,移植瘤体积在照射前及照射后的前4 d差异无统计学意义（P>0.05）,从第5天开始增长明显慢于对照组（F=28.587,P<0.05）。对照组移植瘤实验前的ADC、实验后第1天的ADC与其体积的后期变化存在线性相关关系,放疗后0~24 d,r值从-0.118逐渐升高至0.896。结论 磁共振ADC值可在食管癌移植瘤受照射后早期先于形态学发生变化,并且与肿瘤后期的体积变化存在相关关系。     

Abdominal applications of diffusion-weighted magnetic resonance imaging: Where do we stand

Diffusion-weighted imaging (DWI) is one of the magnetic resonance imaging (MRI) sequences providing qualitative as well as quantitative information at a cellular level. It has been widely used for various applications in the central nervous system. Over the past decade, various extracranial applications of DWI have been increasingly explored, as it may detect changes even before signal alterations or morphological abnormalities become apparent on other pulse sequences. Initial results from abdominal MRI applications are promising, particularly in oncological settings and for the detection of abscesses. The purpose of this article is to describe the clinically relevant basic concepts of DWI, techniques to perform abdominal DWI, its analysis and applications in abdominal visceral MR imaging, in addition to a brief overview of whole body DWI MRI.     

Updates in advanced diffusion-weighted magnetic resonance imaging techniques in the evaluation of prostate cancer

Diffusion-weighted magnetic resonance imaging (DW-MRI) is considered part of the standard imaging protocol for the evaluation of patients with prostate cancer. It has been proven valuable as a functional tool for qualitative and quantitative analysis of prostate cancer beyond anatomical MRI sequences such as T2-weighted imaging. This review discusses ongoing controversies in DW-MRI acquisition, including the optimal number of b-values to be used for prostate DWI, and summarizes the current literature on the use of advanced DW-MRI techniques. These include intravoxel incoherent motion imaging, which better accounts for the non-mono-exponential behavior of the apparent diffusion coefficient as a function of b-value and the influence of perfusion at low b-values. Another technique is diffusion kurtosis imaging (DKI). Metrics from DKI reflect excess kurtosis of tissues, representing its deviation from Gaussian diffusion behavior. Preliminary results suggest that DKI findings may have more value than findings from conventional DW-MRI for the assessment of prostate cancer.