肝脓肿的MRI平扫及动态增强信号特征分析

目的：探讨肝脓肿的MRI平扫及动态增强扫描信号特点。方法：对临床及手术病理证实的21例肝脓肿患者MRI平扫及增强后动态扫描资料进行回顾性分析。结果：21例中,单发肝脓肿13例,多发8例,共39个主病灶,15个伴多发子灶。39个主病灶中,＂簇样征＂3个,蜂窝网格状、花边样征24个,＂环靶征＂12个。平扫示主病灶T1WI间隔及壁呈等低信号、脓腔低信号,T2WI间隔及壁略高信号、内脓腔呈更高信号;子病灶中央见点状T1WI低、T2WI高信号;20个主病灶周围见片状或肝段性T2WI高信号。增强后动态扫描：①动脉期肝脓肿27个主病灶分隔及边缘轻度强化,12个主病灶壁轻度强化、其中10个壁边缘明显强化;②门脉期分隔或/和壁强化逐渐明显、壁边缘持续强化,边界更加清晰;③延迟期（1～5min）分隔或/和壁持续强化。30min延迟扫描8个主病灶,壁内层仍见强化,壁边缘强化减退;④子病灶环边缘动脉期轻度强化、门脉期及延迟期强化逐渐明显;⑤主、子病灶坏死脓腔均无强化;⑥28个主病灶周围见片状或肝段性动脉期一过性强化。结论：MRI平扫及动态增强扫描能较好的显示肝脓肿的发生、演变、发展及转归过程,反映肝脓肿的特征表现。     

肝腺瘤的螺旋CT表现

目的探讨肝腺瘤的螺旋CT表现。方法结合文献回顾性分析临床病理确诊的9例10个肝腺瘤的螺旋CT平扫和增强三期扫描(动脉期、门脉期和延迟期)的表现。结果9例10个肝腺瘤的平扫及增强螺旋CT表现如下:病变边界光滑清晰,无明显分叶。位于肝右叶7个,左叶3个。平扫呈等密度1个,均匀略低密度4个,不均匀低密度2个,混杂密度3个。4个病灶周围环以低密度假包膜,包膜完全2个,不完全2个。2个病灶诊断为急性出血,1个为亚急性出血,4个病灶中心可见坏死,2个病灶内可见脂肪变性。增强扫描:动脉期病灶除出血、坏死和脂肪变性部分呈均匀明显强化8个,有2个病灶肿瘤实质部分呈不均匀强化。门脉期和延迟期病灶呈等密度或略低密度。4个病灶周围包膜平扫和动脉期呈低密度,门脉期或延迟期呈轻度强化。结论螺旋CT特别是三期增强扫描对肝腺瘤的定性诊断及鉴别诊断有重要意义。     

肝脏局灶性结节增生的MRI征象分析

目的:探讨肝局灶性结节增生(FNH)的典型及不典型MRI表现及与病理特点的相关性,提高FNH诊断的准确性。方法:回顾性分析33例(共40个病灶)经手术病理证实的FNH的MRI平扫和增强表现。结果:28例为单发,5例为多发病灶。40个病灶在T1WI呈等或稍低信号,在T2WI呈等或稍低信号,增强扫描动脉期31个病灶(94%)明显强化,门脉期及延迟期呈稍高或等信号;1例动脉期未见明显强化,门脉期及延迟期可见强化;1例动脉期边缘明显强化,门脉期及延迟期逐渐强化。12个病灶(30%)中心可见纤维瘢痕,11个延迟期强化,1个未见明显强化。3个病灶(8%)边缘见假包膜,延迟期可见强化。结论:MRI能较好地反映FNH内部组织学情况及血供特点,充分认识FNH的典型征象及不典型表现能帮助我们准备地做出诊断,从而避免不必要的活检及手术。     

肝腺瘤的综合影像诊断

目的：描述肝腺瘤的超声（US），CT和MRI表现与病理基础，探讨综合影像对肝腺瘤的诊断价值。方法：回顾性分析经手术切除，病理症实的6例肝腺瘤的US，CT和MRI表现，并与病理所见对照。结果：6例肝腺瘤均为单发肿块，1例术前综合影像诊断为肝腺瘤，4例误诊为肝癌，例误诊为肝局灶结节性增生。US：6例呈稍低或低回声，4例有低回声晕，彩色多普勒显示6例肿块内有较丰富的门脉样血流和低速动脉样血流，CT：6例为稍低或低密度，4例有假包膜，4例动脉期，门脉期均轻度强化，1例动脉期中度强化，门脉期轻度强化，MRI：T1WI和T2WI上，6例表现为以高信号为主的混杂信号，用脂肪抑制后T1WI上的高信号无变化；2例动脉期显著强化，门脉期和延迟期轻度强化，3例动脉期，门脉期和延迟基匀轻度强化。6例均有假包膜，且在门脉期或延迟期现轻度强化。结论：肝腺瘤的综合影像表现缺乏特性性。对有假包膜和混杂高信号（用脂肪抑制后T1WI上的高信号无变化）的多血供肿块应考虑到肝腺瘤的诊断。     

肝腺瘤的影像学诊断

目的探讨影像学(US、CT、MRI及DSA)诊断肝腺瘤的价值。方法回顾性分析经手术、病理证实的11例肝腺瘤的影像学表现,其中11例行US和CT检查(有1例行CT灌注成像,CTP),5例行MRI扫描,4例行DSA检查,并与手术病理所见对照。结果11例肝腺瘤均为单发肿块,无肝硬化背景,直径2.0～10.0cm。影像学表现:US检查,10例呈稍低或不均匀稍强回声,边界清晰,6例见低回声晕,彩色多普勒显示肿块内有较丰富的血流;CT检查,10例为稍低或等密度,8/10例动脉期全瘤明显强化,门脉期轻度强化,延迟期呈等密度,1例平扫和延迟期呈等密度,动脉期中度强化,门脉期轻度强化,误诊为血管瘤。1/11例CT灌注成像(CTP)检查,肝动脉灌注量(HAP)=1.08ml/(min.ml),门静脉灌注量(PVP)=0.19ml/(min.ml),肝动脉灌注指数(HPI)=0.85,各参数值与肝癌均有明显不同;MRI检查,5例肝腺瘤均能显示完整包膜,T1WI上2例稍高于肝脏信号,1例呈等信号,2例为稍低信号,T2WI上5例均表现为以稍高信号为主的混杂信号,脂肪抑制像(STIR)1例呈略低信号,4例信号与T2WI相似,行增强扫描的4例病灶动脉期显著强化,门脉期强化减退,平衡期呈等信号。DSA检查,3/4例病灶见粗细不均的异常血管影,实质期可见肿瘤染色表现。结论肝腺瘤的US和DSA表现均缺乏特异性,CT、MRI则具有一定的特点。CTP对肝腺瘤可能具有诊断和鉴别诊断价值。     

MRI表现及ADC值对肝腺瘤的诊断意义

目的：探讨MRI检查对肝腺瘤的诊断价值。方法：回顾性分析经病理证实的15例肝腺瘤患者的MRI表现、ADC值的观测和术前或活检前的诊断,并与病理结果进行对照。结果：14例患者术前诊断考虑肝腺瘤,1例考虑肝腺瘤或局灶性结节样增生（FNH）。15例中1例为多发（9个病灶）,2例为2个病灶,其余12例均为单发,共25个病灶;T,WI上22个病灶呈低或稍低信号,3个病灶呈稍高信号;T2WI上15个病灶呈高信号,10个病灶呈低信号;DWI示16个病灶呈稍高信号,9个病灶呈等信号;双回波序列上24个病灶内有不同程度的脂质成分;6个病灶有瘤内出血。Gd-DTPA增强扫描：动脉期25个病灶呈中度到明显强化;门脉期18个病灶呈稍低信号,7个病灶呈稍高信号;延迟扫描18个病灶呈低信号,7个病灶呈等信号;9个病灶可见假包膜样强化,16例未见明确假包膜样强化。DWI扫描测量17个病灶[12例单发病灶、2例2个病灶及1例多发病灶（测量最大病灶）]的ADC值为（1．696±0．243）×10^-3mm^2／s,周围正常肝实质ADC值为（1．345±0．243）×10^-3mm^2／s,病灶与周围正常肝实质ADC值的比值〉1。结论：MRI检查及ADC值测量为肝腺瘤的无创性诊断提供了更准确的依据。     

原发性肝神经内分泌癌的影像表现

目的 探讨原发性肝神经内分泌癌的CT和MRI表现,提高影像诊断水平.方法 回顾性分析经手术病理证实的6例肝原发性神经内分泌癌患者资料,术前4例行CT平扫及增强扫描,2例行MR平扫及增强扫描.结果6例中肿瘤呈多发1例,表现为1个大肿瘤伴周围多个小结节灶,其余5例均为单发.CT平扫除1例病灶周边可见点状钙化外,均表现为肝内低密度占位,病灶中央见较大范围的不规则更低密度区,边界清晰.肿瘤在MR T1WI表现为不均匀低信号,T2WI表现为略高信号.增强扫描实质部分表现为早期轻中度持续强化,但强化程度有所下降,也可表现为门静脉期和延迟期呈轻度强化,中心更低密度或信号区多无明显强化;周围肝内血管呈受压推移改变,腹腔及后腹膜均未见明显肿大的淋巴结.结论CT和MRI能显示原发性肝神经内分泌癌的特征,在该病的诊断和鉴别诊断中有一定价值.     

肝脏上皮样血管内皮瘤的CT和MRI表现

目的 总结肝脏上皮样血管内皮瘤(HEHE)的CT和MRI表现.方法 搜集经手术或穿刺活检后病理证实的HEHE 11例,所有的病例均行CT检查,其中5例行CT平扫及双期增强扫描(动脉期+门静脉期),其他6例行CT平扫及三期增强扫描(动脉期+门静脉期+延迟期).11例中有5例加做MRI平扫及动态增强扫描.回顾性分析病变的生长方式、分布特点、密度(信号)特点、强化方式及邻近组织情况.结果 11例均表现为肝内多发病灶,大部分病灶位于肝包膜下,根据生长方式分为三型:结节型(5例),匍匐生长型(1例)和混合型(5例).CT平扫,病灶均呈低密度,直径＞2 cm的病灶内见类圆形更低密度.MRI平扫:病灶呈T1WI低信号、T2WI高信号,直径＞2 cm的病灶信号不均匀(T1WI内见更低信号,T2WI内见更高信号).其他影像学征象包括“棒棒糖征”(6例)、包膜退缩征(6例).增强扫描:病灶直径＜1 cm的表现为轻度较均匀强化;病灶直径为1～2 cm主要表现为轻度较均匀强化;病灶直径＞2 cm的多为不均匀渐进性强化.结论 HEHE的CT和MRI表现具有一定的特征性,其强化方式与病灶的大小相关.     

肝脏孤立性坏死结节的CT、MRI表现与病理对照研究

目的:探讨肝脏孤立性坏死结节(SNN)的CT、MRI表现及其分型诊断价值和病理基础.方法:分析经临床和病理证实的肝孤立性坏死结节29例(所有病例均行MR检查,其中15例行CT检查),探讨SNN的CT、MRI表现及其分型诊断价值和病理基础.结果:①单纯凝固性坏死型(14例),T1WI、T2WI上均呈低或低-等信号,增强扫描病灶内凝固性坏死无强化,周围包膜呈延迟强化.其中8例行CT检查,CT平扫呈低或等密度,增强扫描无强化,5例可见包膜呈延迟期环形强化.②伴液化性坏死型(5例),T1WI上呈低信号,较大病灶内可见更低信号;T2WI上病灶呈低-等信号,其内液化性坏死呈点片状更高信号;增强后病灶无强化,周围包膜呈轻-中度强化.CT检查3例,CT平扫呈低或等密度,增强扫描无强化,2例周围包膜呈延迟期环形强化.CT不能反映病灶内液化性坏死.③多结节融合型(10例),T1WI呈低信号,其内可见低-等信号分隔;T2WI病灶以等-稍高信号为主,其内可见等或略高信号分隔,其中6例合并液化性坏死还可见裂隙状高信号.增强扫描病灶无强化,其内分隔及周围包膜呈轻-中度强化.CT检查4例,其中3例为低或等密度融合结节,增强扫描内部分隔及周围包膜呈延迟期强化.CT不能显示内部液化性坏死和病灶全部分隔.结论:CT、MRI能较好反映肝脏孤立性坏死结节的分型及各型的病理特征,MRI在多结节融合型和伴液化坏死型的诊断价值明显优于CT.     

混合型肝脏血管平滑肌脂肪瘤的CT和MRI诊断

目的 探讨肝脏血管平滑肌脂肪瘤(hepatic angiomyolipoma,HAML)CT和MRI的诊断价值.资料与方法回顾性分析经病理证实的8例肝脏HAML的CT和MRI表现.8例均行CT平扫和多时相动态增强扫描,其中4例同时行MRI平扫和多时相动态增强扫描.结果 8例均为单发混合型HAML,CT平扫均表现为低于周围正常肝组织的混杂低密度,灶内含有不同程度的脂肪密度,CT值-40～40HU.4例MRI平扫表现为稍长T1(含短T1)、稍长T2混杂信号,T1WI上高信号在使用脂肪抑制技术后完全消失.CT与MRI多时相动态增强扫描显示动脉期病灶均呈显著不均匀强化,门静脉期6例CT、3例MRI病灶呈持续或渐进性中重度强化,高于周围正常肝实质,2例CT、1例MRI病灶轻中度强化;3例HAML见假包膜,且在门静脉期及延迟期有轻度强化.结论 CT和MRI能显示混合型HAML的特征性表现并可在术前做出准确诊断.     

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).     

Temporal resolution improvement in dynamic imaging

In some dynamic imaging applications, only a fraction, 1/n, of the field of view (FOV) may show considerable change during the motion cycle. A method is presented that improves the temporal resolution for a dynamic region by a factor, n, while maintaining spatial resolution at a cost of √n in signal-to-noise ratio (SNR). Temporal resolution is improved, or alternatively, total imaging time is reduced by reducing the number of phase encodes acquired for each temporal frame by 1/n. To eliminate aliasing, a representation of the signal from the static outer portion of the FOV is constructed using all the raw data. The k-space data derived from this representation is subtracted from the original data sets, and the differences correspond to the dynamic portion of the FOV. Improved resolution results are presented in phantom studies, and in vivo phase contrast quantitative flow imaging.