磁共振DWI在肝癌中的应用

磁共振扩散加权成像（diffusion weighted magnetic resonance imaging,DWI）是目前唯一无创反映活体组织扩散的检查方法,在神经系统DWI作为MRI功能成像新技术,是唯一能在活体检测组织内水分子扩散运动的无创影像检查技术,能在宏观成像中反映活体组织中水分子微观扩散运动。以往DWI主要集中应用于神经放射学领域并且显示出巨大的临床应用价值。随着快速成像技术的迅速发展,DWI已逐步应用到全身其它系统和器官的疾病研究,并开始大量应用于肿瘤疾病,如肿瘤的分期、判断、鉴别诊断和预测肿瘤疗效等,本文着重对其在肝癌中的应用做简单总结。     

磁共振扩散成像技术及其在肝癌的临床应用

磁共振扩散加权成像（DWI）技术可以在分子水平对生物体的组织结构和功能状态进行无创检查.随着磁共振超快速成像序列的开发,使DWI成像技术能够在肝脏应用.肝癌是消化系统常见的恶性肿瘤,DWI在肝癌的鉴别诊断和治疗后评估中具有重要意义,成为一种新的无创检查方法.     

前列腺扩散加权成像技术和诊断应用的研究进展

磁共振扩散加权成像（DWI）是目前唯一能够无创地检测活体组织的水扩散特性的改变,反映分子水平的病理生理过程的检查方法。就前列腺DWI技术及其在前列腺疾病诊断应用中的优势与限度,以及前列腺DWI技术的最新研究进展予以综述。     

磁共振扩散加权成像在乳腺肿瘤中的临床应用

磁共振扩散加权成像（MRdiffusion-weightedimaging,DWI）依赖病理过程中水分子在不同环境中运动差异而成像,DWI成像速度快（平均时间-200s）、无创、没有电离辐射、不需要注射对比剂等优点使其成为乳腺肿瘤方面应用最广的一种功能成像,目前,DWI在应用中存在着诸多限制因素,如场强、b值、诊断的差异等。本文就DWI成像原理及目前在乳腺良恶性病变诊断中的临床应用进行综述。     

磁共振扩散成像技术及其在肝癌的临床应用

磁共振扩散加权成像(DWI)技术可以在分子水平对生物体的组织结构和功能状态进行无创检查。随着磁共振超快速成像序列的开发,使DWI成像技术能够在肝脏应用。肝癌是消化系统常见的恶性肿瘤,DWI在肝癌的鉴别诊断和治疗后评估中具有重要意义,成为一种新的无创检查方法。     

3.0T MR扩散加权成像对宫颈癌放化疗疗效的评估价值

目的：探讨扩散加权成像（DWI）对宫颈癌放化疗疗效的评估价值。方法：46名接受全程放化疗治疗的宫颈癌患者分别在治疗前、治疗2周后、外照射25次后及治疗结束后进行盆腔常规MRI及DWI扫描,每次扫描均测量肿瘤的直径及ADC值。根据治疗结束6个月后的随访结果将患者划分为完全有效组（CR）、部分有效组（PR）及无效组（SD）。计算并两两比较各次 MRI扫描测得的肿瘤ADC值及直径的动态变化值。结果：CR 组在治疗2周及外照射25次的 ADC值提高均高于 RP 组及 SD 组（P＜0．05）,治疗结束后 CR 组的 ADC 值与 PR 组及 SD 组间差异均有统计学意义（P＜0．05）。治疗前、放化疗2周后及外照射25次后各肿瘤组（CR、PR、SD组）的ADC 值、肿瘤最大直径之间差异均无统计学意义（P＞0．05）。结论：DWI可作为预测及监测宫颈癌放化疗疗效的有效方法。     

前列腺癌扩散加权成像的研究进展

MR扩散加权成像(DWI)可以无创地检测活体组织水扩散特性的改变,反映分子水平的病理生理过程,其对前列腺癌的早期诊断、临床分期及侵袭性评估具有重要价值。就DWI对前列腺癌的应用价值,尤其是多种DWI函数模型以及多参数MRI对前列腺癌的应用价值予以综述。     

幕上原始神经外胚叶瘤的常规MRI与DWI表现

目的 分析幕上原始神经外胚叶瘤的常规MRI表现并探讨扩散加权成像（DWI）对幕上原始神经外胚叶瘤（PNETs）的诊断价值。资料与方法 回顾性分析13例经手术病理证实的幕上PNETs的常规MRI表现和3例DWI特点。常规MRI扫描采用梯度回波（Flash）、自旋回波（SE）、快速自旋回波（TSE）序列;DWI采用自旋回波一回波平面（SE-EPI）序列。结果 幕上PNETs常规MRI表现：肿瘤位于幕上脑内任何部位,呈类圆形,边界清楚,T1WI肿瘤呈稍低信号或等信号,T2WI呈等或稍高信号,瘤周无明显水肿或水肿较轻．肿瘤实质多均匀强化,少数肿瘤内可见囊变坏死区或出血灶,肿瘤可引起脑脊液转移,甚至出现远处转移。幕上PNETs的DWI特点：肿瘤实质扩散受限,DWI上呈高信号,表观扩散系数（ADC）呈低信号,ADC值低于其他颅内原发性肿瘤。结论 结合幕上PNETs的常规MRI表现和DWI特点有助于其术前定性诊断和鉴别诊断。     

磁共振扩散加权成像在大肠癌中的诊断应用

磁共振扩散加权成像（DWI）是利用水分子扩散运动特性成像的新技术。它对人体的研究深入到细胞水平，反映着人体组织的微观结构和细胞内外水分子的转运等变化。随着MRI技术的发展，DWI在大肠肿瘤的应用逐渐引起人们的关注，就DWI的基本原理及在大肠癌诊断中的应用现状予以综述。     

体素内不相干运动扩散加权成像对腹部肿瘤的诊断和疗效预测价值

体素内不相干运动（IVIM）扩散加权成像（DWI）可用于评估腹部肿瘤组织的坏死和肿瘤血管的生成,对于腹部（肝脏、胰腺、肾脏、生殖系统等）肿瘤的诊断和鉴别诊断、病理分级的预测、治疗疗效和副反应评估以及对病人预后的预测和治疗方案的优化都有显著意义。就IVIM 的概念、各技术参数的意义及其在腹部肿瘤诊治及疗效 预测中的价值做一综述。     

A monitoring,feedback, and triggering system for reproducible breath-hold MR imaging

A technique is described that provides improved reproducibility of breath-holding for MR image acquisition by monitoring the superior-inferior (S/I) position of the diaphragm. The method incorporates detection of the level of inspiration using an MR signal, rapid display to the patient of diaphragm position to enable breath-hold adjustment, and triggering of image data acquisition once appropriate position is attained. The response time of the system is short, approximately 10 ms. Studies in six volunteers using this method demonstrate a considerable decrease in the S/I range of diaphragm position over 10 consecutive periods of suspended respiration. The mean range is 1.3 mm with the system, while it is 8.3 mm without using it is expected that this method will be of assistance in many abdominal and cardiothoracic studies that use breath-hold techniques.     

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。     

RARE spiral T2-weighted imaging

Spiral imaging has a number of advantages for fast imaging, including an efficient use of gradient hardware. However, inhomogeneity-induced blurring is proportional to the data acquisition duration. In this paper, we combine spiral data acquisition with a RARE echo train. This allows a long data acquisition interval per excitation, while limiting the effects of inhomogeneity. Long spiral k-space trajectories are partitioned into smaller, annular ring trajectories. Each of these annular rings is acquired during echoes of a RARE echo train. The RARE refocusing RF pulses periodically refocus off-resonant spins while building a long data acquisition. We describe both T₂-weighted single excitation and interleaved RARE spiral sequences. A typical sequence acquires a complete data set in three excitations (32 cm FOV, 192 × 192 matrix). At a TR = 2000 ms, we can average two acquisitions in an easy breath-hold interval. A multifrequency reconstruction algorithm minimizes the effects of any off-resonant spins. Though this algorithm needs a field map, we demonstrate how signal averaging can provide the necessary phase data while increasing SNR. The field map creation causes no scan time penalty and essentially no loss in SNR efficiency. Multiple slice, 14-s breath-hold scans acquired on a conventional gradient system demonstrate the performance.     

Echo-Time-Encoded Burst Imaging (EBI): A Novel Technique for Spectroscopic Imaging

A new technique for rapid spectroscopic imaging is presented. The proposed experiment enables a complete mapping of the two-dimensional reciprocal space k_x, k_o, and thus the acquisition of a 1D spectroscopic image in a single scan. The properties of the pulse sequence, based on the use of a burst of low flip angle pulses, are analyzed in the framework of linear response theory, and it is shown that chemical shift information may be introduced into the spatially encoded echoes. First experimental results are presented demonstrating that 32 x 32 proton spectroscopic images may be acquired within less than 1 min with a conventional imaging system.     

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.     

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.     

Simultaneous multislice (SMS) imaging techniques

Simultaneous multislice imaging (SMS) using parallel image reconstruction has rapidly advanced to become a major imaging technique. The primary benefit is an acceleration in data acquisition that is equal to the number of simultaneously excited slices. Unlike in‐plane parallel imaging this can have only a marginal intrinsic signal‐to‐noise ratio penalty, and the full acceleration is attainable at fixed echo time, as is required for many echo planar imaging applications. Furthermore, for some implementations SMS techniques can reduce radiofrequency (RF) power deposition. In this review the current state of the art of SMS imaging is presented. In the Introduction, a historical overview is given of the history of SMS excitation in MRI. The following section on RF pulses gives both the theoretical background and practical application. The section on encoding and reconstruction shows how the collapsed multislice images can be disentangled by means of the transmitter pulse phase, gradient pulses, and most importantly using multichannel receiver coils. The relationship between classic parallel imaging techniques and SMS reconstruction methods is explored. The subsequent section describes the practical implementation, including the acquisition of reference data, and slice cross‐talk. Published applications of SMS imaging are then reviewed, and the article concludes with an outlook and perspective of SMS imaging. Magn Reson Med 75:63–81, 2016. © 2015 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance.     

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.