磁共振扩散加权成像在超急性期脑梗死诊断中的应用

目的 评价磁共振扩散加权成像（DWI）对超急性期脑梗死诊断的准确性。方法 对卒中样起病且发病时间在6h以内、临床高度怀疑脑梗死的21例患者进行DWI和常规MRI扫描。结果 DWI诊断脑死16例，其最终临床诊断均为急性脑梗死，DWI阴性5例，其最终临床诊断为短暂性脑缺血发作；DWI所见高信号区域的同一部位在以后的CT和（或）MRI随访中均有脑梗死病灶；DWI诊断超急性期脑梗死的敏感度和特异度均为100％，常规MRI诊断超急性期脑梗死的敏感度为25％，特异度为100％。结论 DWI对超急性期脑梗死的诊断高度准确，其敏感度明显高于常规MRI。     

高扩散敏感系数扩散加权像异常高信号疾病的鉴别诊断

目的　总结在扩散加权像 (DWI)上表现为异常高信号的疾病种类及其MRI表现 ,探讨高扩散敏感系数 (高b值 )DWI上异常高信号征象的鉴别诊断与相关的生物物理学机制。方法　分析临床高度怀疑脑缺血性中风 ,并且在高b值DWI上发现异常高信号病灶的病人 90例 ,根据发病距检查时间分组 :A组 (1 5～ 6 0h) 13例 ,B组 (7h至 8d) 77例。总结MRI的表现 ,并对病灶进行表观扩散系数 (ADC)及各向异性变异系数 (CV)的计算。结果　急性期脑缺血、颅内出血与血肿、脑脓肿、脑膜瘤、多发性硬化 (MS)的急性发作期等均可在高b值DWI上表现为异常信号。超急性期脑缺血ADC值下降为 (5 87± 1 0 2 )× 10 -4mm2 /s,而MS病例中ADC值轻微升高达 (8 0 8± 1 15 )× 10 -4mm2 /s(P <0 0 5 ) ;脑缺血区的各向异性CV升高 ,与正常对照组的比值为 9 2 1(2 36～ 36 0 5 ) ,(P <0 0 5 ) ,而MS的CV明显下降 ,与正常对照的比值为 0 4 1(0 2 1～ 1 4 5 ) (P <0 0 5 )。超急性、急性期脑缺血与活动性MS均在DWI上与T2 WI上表现相似 ,ADC比率间无显著性差异 (P >0 0 5 ) ,而CV比率间存在显著性差异 (P <0 0 5 )。结论　应用DWI诊断疾病时 ,应常规计算ADC值 ,并结合病史进行综合诊断。针对鉴别困难的病例 ,扩散各向异性CV有重要价值     

高b值DWI对前列腺癌和前列腺炎的鉴别诊断价值

目的探讨高b值DWI对前列腺癌和前列腺炎的鉴别诊断价值。资料与方法 26例经外科手术或穿刺、病理证实的前列腺疾病患者,其中前列腺癌15例,前列腺炎11例,所有患者于手术或穿刺前行MR扩散加权成像,b值选择1000、2000、3000s/mm2,观察对不同b值的扩散加权图像,比较不同b值对前列腺癌及前列腺炎的定性诊断准确率。结果 b值为1000s/mm2时,DWI诊断前列腺癌和前列腺炎的敏感度及特异度分别为66.6%和63.6%;b值为2000s/mm2时,DWI诊断前列腺癌和前列腺炎的敏感度及特异度分别为93.3%和90.9%;b值为3000s/mm2时,DWI诊断前列腺癌和前列腺炎的敏感度及特异度分别为93.3%和100.0%。在b值为1000s/mm2时,DWI诊断前列腺癌和前列腺炎的敏感度及特异度均低于b值为2000、3000s/mm2(P<0.05)。结论选择较高b值,对前列腺癌和前列腺炎的鉴别具有较高的灵敏度和特异度。DWI可作为鉴别前列腺癌和前列腺炎的辅助方法。     

MR扩散加权成像在乳腺良恶性病变诊断及鉴别诊断中的应用研究

目的 探讨磁共振扩散加权成像(DWI)及表观扩散系数(ADC)在乳腺良恶性病变鉴别诊断中的价值.方法 DWI采用自旋回波-回波平面成像(SE-EPI),扩散敏感系数(即b值)分别为500 s/mm2、1 000 s/mm2.测量正常乳腺组(80例)、经手术病理证实的良性(32个病灶)和恶性病变组(48个病灶)共75例ADC值,比较同b值下3组间ADC值差异的统计学意义及不同b值(b = 500 s/mm2、1 000 s/mm2)时各组内ADC值差异的统计学意义.以恶性组平均ADC值的95%可信区间的上限值作为良恶性病变的界值,与病理结果比较,计算b值为500 s/mm2、1 000 s/mm2时诊断的灵敏度、特异度、阳性预测值、阴性预测值、正确率、Youden指数、阳性似然比、阴性似然比.结果 乳腺良、恶性病变在DWI图上均呈高信号.乳腺良、恶性病变,正常腺体间ADC值差异均有统计学意义;2组b值间ADC值差异有统计学意义,并且b值越低,ADC值越大;根据恶性组平均ADC值的95%可信区间的上限值作为诊断乳腺癌的阈值,b值为500 s/mm2、1 000 s/mm2时诊断的各项诊断指标均较高.结论 DWI及ADC值可以作为乳腺良恶性病变诊断及鉴别诊断的重要依据,与MRI其他扫描序列结合可提高乳腺癌的早期诊断率.     

高b值MR扩散加权成像在乳腺良恶性病变诊断中的应用价值

目的 评价高b值MR DWI及ADC值在乳腺良恶性病变诊断中的应用价值.方法 165例患者在行乳腺MR动态增强扫描前行不同b值(分别为500、1500 s/mm2)的DWI扫描,对171个怀疑或高度怀疑恶性病变者行回顾性分析.以正常乳腺组织为参考基准,选择增强图像中异常强化的高信号病变,同时在高b值(b= 1500 s/mm2)DWI中视觉判定是高信号的病变定义为恶性病变阳性结果,否则为良性病变阴性结果.对其中111个DWI视觉判定阳性结果的病变计算ADC值.依据全部病变穿刺活检病理诊断结果,应用Fisher精确检验和Wilcoxon秩和检验对比分析高b值DWI视觉评估中恶性和良性病变的阳性和阴性病灶数,以ADC值=1.13×10-3 mm2/s作为临界值,计算诊断的特异度和敏感度.结果 乳腺病变穿刺活检病理证实的171个乳腺病变中,91个恶性病变,80个良性病变.高b值DWI视觉评估,139个阳性结果中,恶性病变83个,良性病变56个;32个阴性结果中,良性病变24个,恶性病变8个(非肿块性导管原位癌),差异有统计学意义(P＜0.01).所有浸润性癌和肿块样导管原位癌(DCIS)在DWI视觉判定中为阳性,8例非肿块性DCIS判定为假阴性,总体的敏感度为91.2％ (83/91),特异性为30.0％ (24/80).110个肿块样病变和1个局灶性病变DWI视觉评估阳性结果的病变中,63个恶性病变平均ADC值为(0.73±0.24)×10-3 mm2/s,48个良性病变平均ADC值为(1.19±0.42)×10-3mm2/s,差异有统计学意义(Z=5.818,P＜0.01).以ADC值=1.13×10-3mm2/s作为临界值时,61个恶性病变为阳性结果,2个黏液癌为假阴性结果;27个良性病变为阴性结果,21个良性病变为假阳性,诊断敏感度是96.8％(61/63),特异度为56.2％ (27/48).结论 高b值DWI及ADC值对乳腺良恶性病变的鉴别诊断有一定的作用,但在诊断非肿块性乳腺病变时仍需慎重.     

低场磁共振扩散加权成像在超急性期脑梗死的应用

目的：评价低场磁共振的扩散加权成像（DWI）在超急性期脑梗死诊断上的应用价值。方法：用低场磁共振扩散加权成像诊断超急性期脑梗死36例,分析不同时间的影像学特点,并与常规 MRI 平扫进行比较。结果：低场磁共振DWI 能显示所有患者超急性脑梗死病灶,而有11例患者在常规 MRI 平扫上未发现异常,其中7例为发病2 h 内,4例为2～4 h。此外,DWI 还可发现发病1 h 内的脑梗死高信号灶,而且 DWI 显示的病灶范围较常规 T2 WI 显示的范围更大、信号更高。结论：颅脑低场强磁共振扩散成像可以诊断超急性期脑梗死,比 T2 WI、T2 FLAIR 平扫能更早显示病变,在发现病变、确定病变部位、病变范围具有较高的价值,可为临床早期治疗提供可靠的诊断依据。     

低场MR扩散加权成像在超急性期脑梗死诊断中的应用

目的 :评价低场MR扩散加权成像 (DWI)在超急性期脑梗死 (HCI)诊断中的应用价值。方法 :对起病时间 6h内临床拟诊脑梗死的 12例患者使用 0 .2T磁共振仪行DWI和常规MRI扫描。结果 :DWI诊断HCI 8例 ,DWI阴性 4例 ;常规MRI扫描 2例符合脑梗死诊断 ,10例不符合 ,最终临床诊断为HCI 8例。DWI所见异常高信号区在以后的CT或MR随访中均见明显梗死病灶。结论 :低场DWI在HCI诊断中能得到成功运用 ,且诊断高度准确。     

大鼠超急性期脑缺血的磁共振扩散加权成像研究

目的：利用磁共振扩散加权成像（DWI）评价大鼠超急性期脑缺血的诊断价值。方法：12只Wistar雄性大鼠,采用线栓法制作右侧大脑中动脉闭塞（MCAO）脑缺血模型,分别于栓塞后1h和6h行大鼠冠状位磁共振DWI、T2WI和T1WI检查,并测量缺血区DWI异常高信号的体积、表观扩散系数（ADC）值,将所测值进行比较。磁共振检查结束后处死大鼠,断头取脑行TTC染色,并与DWI结果进行比较。结果：大鼠MCAO后1h进行MRI扫描右侧大脑中动脉供血区DWI可见异常稍高信号,ADC为低信号,T2WI和T1WI均未见异常信号;MCAO后6hDWI可见明显高信号,较1hADC值显著减低（P〈0.01）,DWI上梗死灶体积显著扩大（P〈0.01）,T2WI显示缺血区异常高信号,T1WI可见稍低信号。TTC染色者均显示脑梗死灶,与MCAO后6h的DWI显示脑缺血范围一致。结论：DWI对超急性期脑梗死较常规MRI敏感,是超急性期脑缺血重要的检查方法。     

低场MR弥散加权成像在超急性期脑梗死诊断中的应用

目的：评价低场MR扩散加权成像（DWI）在超急性期脑梗死（HCI）诊断中的应用价值。方法：对起病时间6h内临床拟诊脑梗死的16例患者使用0．35T磁共振仪行DWI和常规MRI扫描。结果：DWI诊断HCI12例，DWI阴性4例；常规MRI扫描3例符合脑梗死诊断，9例不符合，最终临床诊断为HCI12例。DWI所见异常高信号区在以后的CT或MR随访中均见明显梗死病灶。结论：低场DWI在HCI诊断中能得到成功运用，且诊断高度准确。能在最短时间内确定患者梗塞部位，为进一步治疗赢得时间。     

DWI及FLAIR技术在急性脑梗塞中的临床应用探讨

目的　探讨弥散加权成像 (DWI)技术及FLAIR技术在急性脑梗塞中的临床应用价值。方法　收集 60例急性脑梗塞患者 ,其中超急性期 ( <6h) 7例 ,急性期 ( 6～ 2 4h) 2 4例 ,亚急性期 ( 2 4～ 72h) 2 9例。均行常规T1WI ,T2 WI及FLAIR ,DWI扫描 ,比较病灶显示范围、边界及对比度 ,并计算病灶的ADC与rADC值。结果　①DWI及FLAIR序列对病灶的显示范围、对比均优于常规T1WI、T2 WI ,而且DWI对病灶显示较FLAIR更清晰。②DWI的b值越高 ,弥散效果越好 ,显示病灶越清晰。同时 ,弥散全方向比单方向显示病灶更清晰。③所有病例病灶的ADC与rADC值均下降。结论　DWI技术对急性脑梗塞病变敏感性最高 ,结合FLAIR技术可准确、可靠地诊断急性脑梗塞     

DSA功能性参数的提取与利用

本文介绍了在临床实际中利用功能性参数，对冠状动脉ＤＳＡ心肌血流灌注成像、冠状动脉血流量测定、左心室功能测定、肺动脉高压程度的评价等项目研究结果。重点讨论了提取ＤＳＡ功能性参数的一般方法，认为功能性参数在现代影像诊断学中的作用是对疾病做出程度、定量、动态及功能诊断。     

Current Status of Optical Imaging for Evaluating Lymph Nodes and Lymphatic System

Optical imaging techniques use visual and near infrared rays. Despite their considerably poor penetration depth, they are widely used due to their safe and intuitive properties and potential for intraoperative usage. Optical imaging techniques have been actively investigated for clinical imaging of lymph nodes and lymphatic system. This article summarizes a variety of optical tracers and techniques used for lymph node and lymphatic imaging, and reviews their clinical applications. Emerging new optical imaging techniques and their potential are also described.     

Fast imaging of phosphocreatine in the normal human myocardium using a three-dimensional RARE pulse sequence at 4 Tesla

PURPOSE: To investigate the use of a three-dimensional rapid acquisition with relaxation enhancement (RARE) pulse sequence for direct acquisition of phosphocreatine (PCr) images of the human myocardium. MATERIALS AND METHODS: A short elliptical birdcage radiofrequency (RF) body coil was constructed to produce a uniform flip angle throughout the chest cavity. In vivo images using a spectrally-selective RARE sequence with a spatial resolution of 1.2 cm x 1.2 cm x 2.5 cm (4 cm(3)) were acquired in nine minutes and 40 seconds. RESULTS: Scans of phantoms demonstrated excellent spectral selectivity. The signal-to-noise ratio in the myocardium ranged from 12.6 in the anterior wall to 5.3 in the mid septum. CONCLUSION: This study demonstrates that PCr data can be acquired using a three-dimensional RARE sequence with greater spatial and temporal resolution than spectroscopic techniques.     

Molecular imaging of the lungs

An emerging suite of new imaging techniques offer the ability to monitor and quantify molecular and cellular processes in the lungs noninvasively. These techniques take advantage of dramatic advances in both imaging technology as well as molecular and cell biology. Molecular imaging is being used with increasing regularity in research protocols, and forms of molecular imaging have found their way into the patient care setting (eg, positron emission tomography imaging in cancer). Such techniques will afford the basic scientist as well as the clinician an unprecedented opportunity for in vivo study of the lung biology that drives normal pulmonary physiology as well as pathophysiology.     

Dynamic bioluminescence imaging for quantitative tumour burden assessment using IV or IP administration of <Emphasis Type="SmallCaps">d</Emphasis>-luciferin: effect on intensity,time kinetics and repeatability of photon emission

Introduction In vivo bioluminescence imaging (BLI) is a promising technique for non-invasive tumour imaging. d-luciferin can be administrated intraperitonealy or intravenously. This will influence its availability and, therefore, the bioluminescent signal. The aim of this study is to compare the repeatability of BLI measurement after IV versus IP administration of d-luciferin and assess the correlation between photon emission and histological cell count both in vitro and in vivo. Materials and methods Fluc-positive R1M cells were subcutaneously inoculated in nu/nu mice. Dynamic BLI was performed after IV or IP administration of d-luciferin. Maximal photon emission (PE_max) was calculated. For repeatability assessment, every acquisition was repeated after 4 h and analysed using Bland–Altman method. A second group of animals was serially imaged, alternating IV and IP administration up to 21 days. When mice were killed, PE_max after IV administration was correlated with histological cell number. Results The coefficients of repeatability were 80.2% (IV) versus 95.0% (IP). Time-to-peak is shorter, and its variance lower for IV (p < 0.0001). PE_max was 5.6 times higher for IV. A trend was observed towards lower photon emission per cell in larger tumours. Conclusion IV administration offers better repeatability and better sensitivity when compared to IP. In larger tumours, multiple factors may contribute to underestimation of tumour burden. It might, therefore, be beneficial to test novel therapeutics on small tumours to enable an accurate evaluation of tumour burden. Marleen Keyaerts is a Ph. D. fellow of the Research Foundation—Flanders (Belgium; FWO).     

Molecular imaging programs in the United States: results of a national survey

RATIONALE AND OBJECTIVES: We sought to identify and describe the characteristics of molecular imaging (MI) programs in the United States and to determine the factors considered critical for their future. MATERIALS AND METHODS: In a cross-sectional study, a validated survey was sent to members of the Society of Chairmen in Academic Radiology Departments (SCARD) in the United States, and 26 variables were studied. RESULTS: The response rate was 40.3%; 67.9% of the departments surveyed have an MI program. The main focus of 47.4% of departments is oncology. The number of radiologists working for the department was the only variable found to be significantly positively correlated with (1) number of researchers in the MI program, (2) number of MI modalities available, (3) total number of grants, and (4) having ongoing MI clinical trials. These four variables plus the number of federal grants and the space used by MI programs were independent of the geographical region, hospital size (number of beds), and department size (number of radiological examinations per year). All the MI programs received grants during 2005. Only 16.1% have no alliances with industry. Among all the departments, 82% identified staff training and recruitment as the keys for success; 78.57% considered oncology the most important future application of MI and cancer management the hospital service most affected by MI. CONCLUSION: MI programs are starting to be more widespread throughout the United States, and the trend is for more academic radiology departments to become engaged in MI activities; their development is independent of department characteristics. Radiology departments strongly agreed about the key components for success of MI initiatives and the areas that will be most affected by MI applications.     

Phase insensitive preparation of single-shot RARE: Application to diffusion imaging in humans

Although RARE and GRASE can produce single-shot images of excellent quality, their utility has been restricted because preparation of the magnetization with interesting contrast before imaging can cause severe artifacts. These artifacts relate to the strong sensitivity of multiple spin echo sequences to the phase of the prepared magnetization. Modifications of the RARE sequence to eliminate these artifacts are discussed, and an approach that eliminates the artifact producing signals from the very first echo is presented. The approach is applied to diffusion imaging of the human brain in normal volunteers and one patient.     

Head and neck imaging: the role of CT and MRI

High-resolution computed tomography (CT) and magnetic resonance imaging (MRI) have become indispensable tools for the evaluation of conditions involving the head and neck. Complex anatomic structures and regions, such as the orbit, skull base, paranasal sinuses, deep spaces of the neck, larynx, and lymph nodes, require that the radiologist be familiar with the imaging modalities available and their appropriate applications. The purpose of this article is to review the techniques of CT and MRI and the roles they play in clinical practice, including head and neck disorders.     

A Velocity k-Space Analysis of Flow Effects in Echo-Planar and Spiral Imaging

A velocity k-space formalism facilitates the analysis of flow effects for imaging sequences involving time-varying gradients such as echo-planar and spiral. For each sequence, the velocity k-space trajectory can be represented by k_v (k)_r; that is, its velocity-frequency (k_r) position as a function of spatial-frequency (k_r) position. In an echo-planar sequence, k_r is discontinuous and asymmetric. However, in a spiral sequence, k_r is smoothly varying, circularly symmetric, and small near the k_r origin. To compare the effects of these trajectory differences, simulated images were generated by computing the k-space values for an in-plane vessel with parabolic flow. Whereas the resulting echo-planar images demonstrate distortions and ghosting that depend on the vessel orientation, the spiral images exhibit minimal artifacts.     

CAIPIRINHA-Dixon-TWIST (CDT)-volume-interpolated breath-hold examination (VIBE) for dynamic liver imaging: Comparison of gadoterate meglumine,gadobutrol and gadoxetic acid

Purpose

CAIPIRINHA-Dixon-TWIST (CDT)-VIBE is a robust method for abdominal magnetic resonance imaging providing both high spatial and high temporal resolution. The purpose of this study was to examine the influence of different gadolinium based contrast agents (GBCA) on image quality (IQ) with CDT-VIBE.

Materials and methods

In this IRB-approved, retrospective, inter-individual comparison study, 86 patients scanned at 3T were included. Within 28 s, 14 high-resolution 3D datasets were acquired using CDT-VIBE. 37 patients received 0.1 mmol/kg gadoterate meglumine, 28 patients 0.1 mmol/kg gadobutrol, and 19 patients 0.1 mL/kg gadoxetic acid. Two blinded, board-certified radiologists assessed the image quality on a 5 point scale, as well as the number of hepatic arterial dominant (HAD) phases.

Results

Regardless of the GBCA utilized, CDT-VIBE resulted in good IQ in terms of best IQ achieved among all 14 datasets (gadobutrol 4.3, gadoterate meglumine 3.9, gadoxetic acid 3.7). With respect to worst IQ, the three groups showed statistically significant differences with gadobutrol receiving the highest rating (3.6) and gadoxetic acid the lowest (2.4) (gadoterate meglumine 3.0; 0.0014 < p < 0.0485). No statistically significant differences were found in the mean number of acquired HAD phases (gadobutrol 3.4, gadoterate meglumine 3.9, gadoxetic acid 3.1; 0.18 < p < 0.57).

Conclusion

Different gadolinium-based contrast agents can be utilized for dynamic liver imaging with CDT-VIBE resulting in good image quality.