肾上腺皮质大腺瘤的MRI表现

目的探讨直径在4.0cm以上肾上腺皮质大腺瘤的常规MRI及扩散加权成像(DWI)表现,以提高诊断水平。方法回顾性分析经手术病理证实的15例肾上腺皮质腺瘤(≥4cm)的常规MRI表现、DWI特点及病理学表现,并与其他肿瘤进行鉴别。结果常规MRI表现:15例中,12例信号不均匀,T2WI压脂像以等高或较高信号为主,6例在梯度回波反相位上瘤体内见斑片状局灶性的信号减低区,3例在T1WI预扫见斑片状高信号区,增强扫描7例(约46.7%)呈"慢进不出"型,5例(约33.3%)呈"慢进快出"型;2例(约13.3%)呈"快进慢出"型,1例呈延迟期明显强化。实质期或延迟期肿瘤均见环形强化的完整包膜,8例见强化的纤维分隔。DWI特点:肿瘤实质扩散受限,DWI上呈高信号,表观弥散系数(ADC)图上呈低信号,平均ADC值为0.993×10-3 mm2/s,低于大多数肾上腺良性肿瘤。结论肾上腺皮质大腺瘤的病理成分复杂多样,结合其常规MRI表现和DWI特点有助于其术前定性诊断及鉴别诊断。     

胚胎发育不良性神经上皮瘤的MRI表现特征

目的 探讨胚胎发育不良性神经上皮瘤（DNT）的MRI表现特征。方法 对经手术病理证实的6例DNT的MRI材料进行回顾性分析，总结DNT的MRI表现特征。结果 6例患者的肿瘤均局限于皮层或以皮层为主，呈三角形假囊肿样，T1WI呈低信号，T2WI呈高信号；T2水抑制像上边缘和分隔呈高信号，其他部分呈等偏低信号；扩散加权像（DWI）上呈低或等偏低信号，表观扩散系数（ADC）图呈ADC值升高；MR波谱测定肿瘤胆碱（Cho）峰和肌酸（Cr）峰改变不明显，N-乙酰天门冬氨酸（NAA）较正常参照侧降低，但降低不明显；增强无强化；瘤体夹杂细条索状等信号分隔；无瘤周水肿，无占位效应；肿瘤邻近的颅骨内板发育不良。结论 胚胎发育不良性神经上皮瘤MRI表现较具特征性，有助于术前正确诊断。     

幕上原始神经外胚叶瘤的影像学表现

目的 探讨幕上原始神经外胚叶瘤（SPNET）的MRI及CT特征。方法 回顾性分析10例经手术病理证实的SPNET的MRI及CT表现。结果 SPNET的影像学表现有以下特点；（1）肿瘤呈类圆形，边界清楚，病灶周围无水肿或水肿较轻，且大部分位于中线附近及侧脑室旁，少数位于皮层下；（2）MRI示肿瘤实质T1WI呈稍低或等倍，T2WI呈等信号，与脑灰质信号相等，增强较明显。（3）CT示肿瘤实质呈稍高密度，影像学表现与髓母细胞瘤相似。（4）中线附近的肿瘤为实体结构。无囊变；囊变明显的肿瘤多们于皮质下。（5）部分肿瘤内有出血或钙化，有的可见到脑脊液扩散灶。结论 SPNET影像学表现有一定特征。结合其影像学表现及临床症状有助于与其他肿瘤区分。     

弥散MRI诊断颅内表皮样囊肿的价值

目的:探讨磁共振弥散加权成像(DWI)及表观弥散系数(ADC)图诊断颅内表皮样囊肿的价值.材料和方法:分析19例表皮样囊肿常规MRI和DWI的信号特征,定量测定表皮样囊肿、正常脑实质和脑脊液的ADC值.结果:17例表皮样囊肿T1WI、T2WI呈等或稍高于脑脊液信号,2例T1WI呈高低混杂信号.肿瘤边缘弧线形增强或不增强.19例肿瘤DWI呈明显高于脑实质和脑脊液信号,肿瘤较脑脊液的平均ADC值显著减低,较脑实质的平均ADC值显著增高.结论:DWI优于常规MRI发现颅内表皮样囊肿,DWI上表皮样囊肿的高信号可能是肿瘤组织的T2余辉效应所致.     

DWI及ADC值鉴别后颅窝实质型血管母细胞瘤与其它富血供肿瘤的价值

目的：探讨磁共振扩散加权成像（DWI）及表观扩散系数（ADC）在鉴别后颅窝实质型血管母细胞瘤与其它富血供肿瘤中的应用价值。方法：经手术病理证实的15例后颅窝实质型血管母细胞瘤患者和28例其它富血供肿瘤（包括髓母细胞瘤5例,脑膜瘤5例,听神经瘤4例,室管膜瘤3例,转移瘤3例,淋巴瘤3例,间变型少突胶质细胞瘤1例,毛细胞型星形细胞瘤1例,间变性星形细胞瘤1例,胶质母细胞瘤1例,脉络膜乳头状瘤1例）患者,术前行 MRI平扫、增强扫描和D WI检查,评估所有肿瘤病灶的D WI信号并测量ADC值,采用独立样本t检验对两组结果进行比较,并绘制受试者工作特征（ROC）曲线,评价ADC值对后颅窝实质型血管母细胞瘤的诊断效能。结果：1 5例后颅窝实质型血管母细胞瘤中,13例于DWI上呈低信号,2例呈等信号,平均ADC值为（2．06±0．46）×10－3mm2／s;28例后颅窝其它富血供肿瘤中,18例于DWI上呈高信号,6例呈等信号,4例呈低信号,平均ADC 值为（0．97±0．28）×10－3mm2／s;两组中肿瘤的ADC值差异有统计学意义（t＝8．373,P＝0．000）;ROC曲线下面积为0．979（P＝0．000）,以ADC 值1．520×10－3mm2／s 作为阈值,诊断后颅窝实质型血管母细胞瘤的敏感度和特异度分别为93．3％和92．9％。结论：DWI及ADC 值有助于鉴别后颅窝实质型血管母细胞瘤与其它富血供肿瘤,在实质型血管母细胞瘤的 MRI检查中,DWI应作为一种重要的鉴别手段而纳入常规。     

睾丸精原细胞瘤MRI表现

目的 分析睾丸精原细胞瘤的MRI影像表现,以提高睾丸精原细胞瘤的诊断水平.方法 回顾性分析经手术病理证实的14例睾丸精原细胞瘤MRI表现.结果 睾丸精原细胞瘤MRI表现呈团块状或结节状,边界清晰,T2WI呈均匀短T2信号,其内可见低信号分隔,扩散加权成像(DWI)扩散受限呈高信号,表观扩散系数(ADC)图呈低信号,增强后病变实质呈轻度强化,分隔强化较实质相对明显,时间-信号强度曲线(TIC)为缓慢上升型.结论 睾丸精原细胞瘤MRI表现具有一定特征性,对病变诊断具有重要诊断价值.     

MRI常规扫描结合DWI对髓母细胞瘤的诊断价值

目的 :评价MRI常规扫描结合DWI对髓母细胞瘤的诊断价值。方法 :搜集经手术病理证实的髓母细胞瘤 2 3例 ,均行MRI常规扫描 ,7例行DWI。结果 :髓母细胞瘤常见于小脑蚓部 (1 5例 ,占 6 5 .2 %) ,易囊变 (1 9例 ,82 .6 %) ,4例出现转移 (1 7.4 %)。瘤体T1 WI呈等或稍低信号 ,T2 WI等或稍高信号 ,注射Gd DTPA后呈中等至明显强化。肿瘤实性部分DWI呈略高信号 ,ADC图呈略低信号。坏死囊变部分与脑脊液信号相仿。瘤周水肿DWI呈等及稍高信号 ,ADC图呈稍高及高信号。结论 :常规MRI结合DWI对髓母细胞瘤的诊断和鉴别诊断有重要价值。     

MRI findings of pilocytic astrocytoma

目的:探讨毛细胞性星形细胞瘤(PA)的MRI表现.方法:回顾分析经手术病理证实的14例PA的MRI表现.所有患者术前均行MRI平扫、增强扫描(其中9例行动态增强扫描)及DWI检查(b=1000s/mm2),8例行1 H-MRS、5例行磁敏感加权成像( SWI)检查.结果:14例中11例为单发,呈类圆形,其中8例位于幕下,3例位于幕上;3例为多发,呈不规则形,其中2例位于幕上,1例同时累及幕上及幕下.14例中病灶为囊性4例,T1WI呈低信号,T2WI呈高信号,3例囊壁明显强化,1例无强化;呈囊实性9例,囊性部分T1WI呈低信号、T2WI呈高信号、均无强化,实性部分T1WI呈等信号或稍低信号、T2WI呈等信号或稍高信号,8例明显强化、1例轻度强化;实性1例,T1WI及T2WI均呈等信号,无强化.时间-信号强度曲线6例为流入型,3例为平台型.11例无瘤周水肿,2例有轻度瘤周水肿,1例有明显瘤周水肿.DWI示病变囊性部分呈低信号,实质部分呈高信号,ADC均值为2.437×103 mm2/s.8例1 H-MRS均提示与对侧正常组织比较,肿瘤的NAA峰及NAA/Cr降低,Cho峰及Cho/Cr增高.5例SWI示病变内均可见异常血管.结论:PA的MRI表现具有一定特征性,MRI可为临床提供较为准确的诊断信息.     

多发性胶质母细胞瘤MRI表现(附4例报告)

目的探讨4例经手术病理证实的多发性胶质母细胞瘤患者的MRI表现,并结合文献讨论其病理特点。资料与方法 4例经手术病理证实的多发性胶质母细胞瘤患者术前均行快速自旋回波(TSE)序列T1WI、T2WI、液体衰减反转恢复序列(FLAIR)、扩散加权成像(DWI)以及增强扫描,分析其病理特点与MRI表现。结果多发性胶质母细胞瘤的MRI表现主要为脑实质内大小不等,形态不一,伴不同程度的瘤周水肿和占位效应的多发病灶;T1WI呈低信号,T2WI呈混杂信号,FLAIR呈高信号、DWI呈不同程度弥散受限;增强扫描主病灶多呈典型的花环状强化,子病灶多根据转移时间的早晚呈结节状或不规则环形强化。结论多发性胶质母细胞瘤MRI多表现为脑实质内多发占位,病变形态不一,呈多种类型、不同程度的强化。     

毛细胞性星形细胞瘤的MRI表现

目的:探讨毛细胞性星形细胞瘤(PA)的MRI表现。方法:回顾分析经手术病理证实的14例PA的MRI表现。所有患者术前均行MRI平扫、增强扫描(其中9例行动态增强扫描)及DWI检查(b=1000s/mm2),8例行1 H-MRS、5例行磁敏感加权成像(SWI)检查。结果:14例中11例为单发,呈类圆形,其中8例位于幕下,3例位于幕上;3例为多发,呈不规则形,其中2例位于幕上,1例同时累及幕上及幕下。14例中病灶为囊性4例,T1WI呈低信号,T2WI呈高信号,3例囊壁明显强化,1例无强化;呈囊实性9例,囊性部分T1WI呈低信号、T2WI呈高信号、均无强化,实性部分T1WI呈等信号或稍低信号、T2WI呈等信号或稍高信号,8例明显强化、1例轻度强化;实性1例,T1WI及T2WI均呈等信号,无强化。时间-信号强度曲线6例为流入型,3例为平台型。11例无瘤周水肿,2例有轻度瘤周水肿,1例有明显瘤周水肿。DWI示病变囊性部分呈低信号,实质部分呈高信号,ADC均值为2.437×103 mm2/s。8例1 H-MRS均提示与对侧正常组织比较,肿瘤的NAA峰及NAA/Cr降低,Cho峰及Cho/Cr增高。5例SWI示病变内均可见异常血管。结论:PA的MRI表现具有一定特征性,MRI可为临床提供较为准确的诊断信息。     

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.