1.5T DWI在肺内良、恶性病变鉴别诊断中最适b值的探讨

目的:探讨1.5TDWI对肺内良、恶性病变的鉴别诊断价值及b值的优化。方法:搜集40例经病理/临床证实的肺内良、恶性病变患者(恶性病变23例,良性病变17例)的影像及临床资料,40例均经MSCT检查发现肺部病变,并行常规T1WI、T2WI以及多b值DWI(b=0,300,600,1000s/mm2)检查,测量3组b值测得的ADC值,分析不同b值对图像质量、信噪比(SNR)、对比噪声比(CNR)的影响,根据受试者工作特征(ROC)曲线评价不同b值下ADC值鉴别肺部良、恶性病变的诊断效能;并比较同一b值下良、恶性病变ADC值的差异。结果:随着b值的增加,DWI图像信号逐渐增高,ADC、SNR及CNR值逐渐下降;b值为300和600s/mm2两组图像SNR值差异无统计学意义(P>0.05),b值为300与1000s/mm2以及600与1000s/mm2两组SNR值差异均具有统计学意义(P均<0.05);CNR值在两两组间的差异均具有统计学意义(P均<0.05)。b值为300、600和1000s/mm2时,ROC的曲线下面积(AUC)分别为0.78、0.83和0.81,且均具有诊断意义(AUC均>0.5),当b=600s/mm2时,诊断效能最高。在同一b值下,恶性病变图像信号高于良性病变,且ADC值低于良性病变(P均<0.05)。结论:1.5T DWI多b值胸部扫描有助于鉴别肺内良、恶性病变,当b=600s/mm2时,对肺良、恶性病变的鉴别诊断效能最高。     

扩散加权成像在大肠癌中的初步应用

探讨不同b值DWI对大肠癌的显像能力,确定大肠癌DWI成像的合理b值;并探讨ADC值与大肠癌分化程度及T分期关系,为临床治疗提供进一步的依据。对30例经结肠镜证实的大肠癌患者术前应用1.5T磁共振行MRI常规和多b值(400、600、800、1000、1200s/mm2)扩散加权成像。测量不同b值及T2肿瘤区域组织、正常肠壁的信号强度值及背景噪声的信号强度值,计算不同图像中ADC值、信噪比及对比噪声比等数据,并进行统计学分析;对所有经手术病理证实的30例患者进行病理分级和T分期,比较不同b值时不同分化程度及不同T分期肿瘤的ADC值,并进行统计学分析。扩散图像中肿瘤与正常肠壁的对比噪声比(CNR),随着b值的升高而下降,b值400～1200s/mm2时DWI图像的CNR均高于T2图像;b值1000s/mm2时DWI图像的CNR高于b值1200s/mm2,差异有统计学意义(P<0.05),随着b值的升高,肿瘤的SNR逐渐下降,b值400～800s/mm2时DWI的SNR与T2图像相比(P<0.05),差异有统计学意义,b=1200s/mm2时DWI图像的SNR低于T2图像;随着b值的升高,肿瘤区域ADC值逐渐变小,当b值≤800s/mm2时各组间相比,差异有统计学意义(F=12.863,P<0.05)。不同b值时不同分化程度的肿瘤ADC值比较(F=3.473,P<0.05),差异有统计学意义,存在于高分化和中分化、低分化间;随着分化程度降低,肿瘤ADC值逐渐降低。不同T分期肿瘤ADC值各组间比较P<0.05,无统计学意义。综上所述:①当b=1000s/mm2,不仅可以得到大肠癌DWI图像的良好显示,而且可以使所测量ADC值更准确。②随着b值升高,肿瘤区域ADC值逐渐降低,大肠癌ADC值与癌组织的恶性度相关,随着癌组织分化程度的降低,病灶ADC值越来越小。ADC值可以作为大肠癌诊断和评价预后的指标。     

直肠癌3.0T磁共振扩散加权成像中b值的选择

目的:选择直肠癌3.0T磁共振扩散加权成像(DWI)的合适b值,以利于DWI对直肠癌病灶的检出.方法:对63例直肠癌患者行多b值DWI检查(b值为300、600、900、1200、1500、1800、2100 s/mm2)及常规MRI平扫(T2 WI、T1 WI).测量不同b值时直肠癌的ADC值;计算直肠癌的信噪比(SNR)及膀胱的信号强度比(SIR);根据HE染色病理图片记录直肠癌的细胞密度,并进行统计学分析.结果:随着b值的增大,直肠癌ADC值及SNR呈逐渐降低趋势,差异有统计学意义(P＜0.05).当b值≤1200 s/mm2时,DWI图像中直肠癌SNR均高于T2 WI图像(P＜0.05).各不同b值的DWI图像中膀胱SIR均低于T2WI图像(P＜0.05),随着b值的增大膀胱SIR逐渐减低,当b值≥1200 s/mm2时,膀胱SIR明显减低接近于1.不同b值时直肠癌ADC值与细胞密度之间均呈负相关(P＜0.05),b=1200 s/mm2时,其相关度最高(r=-0.76,P＜0.05).结论:直肠癌3.0T磁共振扩散加权成像中的合适b值应为1200 s/mm2.     

3.0 T MR颈段脊髓DWI优化b值的初步研究

目的 应用3.0T磁共振采用不同扩散敏感系数(b值)对颈段脊髓行扩散加权成像(DWI)检查,优选最佳b值.方法 49例行颈段脊髓DWI检查,采用单次激发自旋回波平面成像序列,b值分别取400、600、800、1000s/mm2,测量颈段脊髓表观扩散系数(ADC)值并分析各组DWI图像及ADC图像质量,对比不同b值对成像效果的影响.结果 49例受检者均获得较满意的DWI和ADC图像.随着b值由400 s/mm2升高至1000 s/mm2,脊髓与脑脊液信噪比逐渐降低,脊髓脑脊液对比噪声比b值为600 s/mm2时最高,此后逐渐降低,且ADC参考范围较稳定.结论 b值为600 s/mm2时,颈段脊髓DWI图像质量最好,可以获得较满意的DWI及ADC图像.     

肺恶性肿瘤和实性良性病变扩散加权成像技术初探

目的 探讨相控阵线圈联合并行采集空间敏感度编码技术(ASSET) 扩散加权成像(DWI)用于检查肺内恶性肿瘤和实性良性病变的可行性,并优化DWI检查扫描参数.方法 12例肺良性病变和50例肺恶性肿瘤(共66个病灶)被纳入研究,其中最初就诊的12例构成不同DWI方案实验组(组1),全部62例病例构成b值实验组(组2).组1采用4种不同DWI扫描方案:A,ASSET+自由呼吸+4NEX;B,ASSET+自由呼吸+1NEX;C,ASSET+屏气+1NEX;D,常规DWI+屏气+1NEX;比较各方案的信噪比(SNR)和对比噪声比(CNR),从中选出最佳扫描方案.组2应用筛选出的最佳扫描方案行不同b值(200、300、500、700和1 000 s/mm2)DWI检查,比较各b值组的SNR、CNR、ADC值以及ADC值对肺良恶性病变的鉴别诊断效能,从中选出最佳b值.结果 组1内4种扫描方案SNR和CNR差异均有统计学意义(P均为0.000),且方案A最大.组2中,不同b值组间SNR差异有统计学意义(P=0.000),而CNR差异无统计学意义(P>0.05);良性病变组和恶性病变组ADC值均随b值增加而逐渐变小,差异有统计学意义(P=0.039,P=0.000);从200～1 000 s/mm2不同b值的4组的ROC曲线下面积(Az)分别为0.608、0.537、0.785、0.583、0.576,均有诊断意义(Az>0.5),b取500 s/mm2时获得的ADC值的诊断效能最大,此时ADC值鉴别良恶性病变的最佳阈值为1.400×10-3 mm2/s,敏感度和特异度分别为83.3%和74.1%.结论 在1.5 T MR设备上,采用相控阵线圈和ASSET技术对肺恶性肿瘤和良性实性病变行DWI检查切实可行;在自由呼吸状态下采用b值为500 s/mm2、激励次数(NEX)为4时能够获得满意的胸部DWI影像.     

不同b值扩散加权MRI诊断肝脏局灶性病变的初步研究

目的:探讨不同b值磁共振扩散加权成像(DWI)系列分析及表观扩散系数(ADC)值对肝脏常见局灶性病变定性诊断的价值.方法:对45例肝脏常见局灶性病变(15例肝癌,18例肝血管瘤,12例肝囊肿)行不同b值DWI (b=600 s/mm2,1000 s/mm2,2000 s/mm2),观察病灶DWI信号强度连续变化并计测表观扩散系数(ADC)值.结果:肝癌不同b值DWI均表现为高信号,随b值增加,病灶信号强度无显著性改变(P＞0.05);肝血管瘤DWI (b=600 s/mm2)表现为高信号,DWI (b=1000 s/mm2,2000 s/mm2)表现为高或等信号,随b值增加,病灶信号强度降低(P＜0.05);肝囊肿DWI (b=600)表现为高、等或低信号,DWI (b=1000 s/mm2,2000 s/mm2)表现为低信号,随b值增加,囊肿信号强度降低(P＜0.05).随b值增加,肝癌、肝血管瘤、肝囊肿的ADC值均逐渐降低(P＜0.05).结论:不同b值DWI系列分析可能鉴别诊断肝脏常见局灶性病变.     

直肠癌MR扩散加权成像的b值选取及其应用价值

目的:探讨扩散加权成像在直肠癌中的应用价值及最佳b值的选择.方法:45例直肠癌行高分辨率MRT2WI及DWI检查,DWI采用单次激发自旋回波-平面回波技术(SE-EPI),选择b值为500、800、1000、1200s/mm2,评价直肠癌的显示情况,计算肿瘤的信噪比(SNR)及肿瘤与肠周脂肪、肌肉的对比噪声比(CNR),对不同b值的图像质量进行统计分析.另20例同时行自由呼吸薄层DWI扫描,b值为1000 s/mm2,行冠状面最大强度投影(MIP)及多平面重组(MPR),将图像反转及彩色化,评价其对肿瘤的显示情况.结果:在不同b值时,所有直肠癌均表现为高信号,与正常肠壁对比高于T2WI . MIP及MPR的反转图像及彩色化图像,病灶与背景产生鲜明对比,清楚直观的显示肿瘤.肿瘤的信号、SNR及肿瘤与肠周脂肪、肌肉及水的CNR随着b值的增加而下降,但与正常肠壁的对比更明显(42/45).b=500 s/mm2高信号的正常小肠显示较多,对21例直肠上段癌的判断存在一定的困难,而b≥800 s/mm2正常组织结构显示少,基本不影响肿瘤的显示.b值为800 s/mm2与1000s/mm2时SNR及所有CNR差异均无显著性意义,余各组间的SNR及CNR间差异均有显著性意义.结论:DWI对直肠癌显示敏感性高,b值选择800和1000s/mm2较理想.     

食管癌扩散加权成像的b值选取及其在恶性程度评估中的应用

目的:探讨食管癌扩散加权成像的最佳b值及ADC值在预测食管癌恶性程度中的价值.方法:对45例经病理证实的食管癌患者行常规MRI及多b值DWI扫描,分别采用b值500、800和1000s/mm2.结果:随着b值的升高,DWI图像上食管癌病变的信号噪声比(SNR)、对比噪声比(CNR)逐渐下降(SNR分别为55.79±27.74、42.05±22.74、30.38±17.30;CNR分别为31.85±19.82、22.35±13.57和17.35±14.49).经受试者工作特征(ROC)曲线分析,各b值下病变的ADC值均可作为评估肿瘤分化程度的有效指标,但以选取b值为500 s/mm2时诊断效能最高,曲线下面积最大(AUC=0.902),ADC值的最佳阈值为1.72×10 3 mm2/s.结论:使用b值为500 s/mm2的DWI检查有利于食管癌病变的检出.DWI及ADC值在一定程度上能够反映肿瘤的分化情况,有助于食管癌的术前评估.     

1.5TMR乳腺扩散加权成像b值的优化

目的 通过分析水模、正常乳腺腺体、乳腺良性及恶性病变的ADC值及图像信噪比(SNR)随b值的变化规律,探讨1.5 TMR乳腺DWI合理的b值取值范围.方法 对32例经病理证实的乳腺病变(恶性18例,良性14例)及对侧正常腺体进行乳腺MR检查,采用EPI-DWI序列;b值分别采用0、50、100、200、400、600、800、1000、1200、1400、1600、1800、2000、2200、2400、2600 s/mm2.测量不同b值下水模、正常乳腺腺体、乳腺良性及恶性病变的平均ADC值和图像SNR,采用Pearson相关分析法分析不同b值时的变化规律.结果 DWI的SNR均随b值的增加逐渐下降,二者呈负相关(r=-0.802,P＜0.01),乳腺良、恶性病变的ADC值均随着b值的增加而下降(r=-0.923和-0.855,P＜0.01);当b值取800～1000 s/mm2时,恶性病变与良性病变和正常腺体之间的ADC值差异最大(0.7×10-3mm2/s);当b值＞1400 s/mm2,差异逐渐减小.结论 取b值800～ 1000 s/mm2时,既能取得良好的图像质量,又能有效地鉴别乳腺良、恶性病变,是1.5 TMR乳腺DWI最合理的b值取值范围.     

乳腺良恶性病变的3.0T磁共振扩散加权成像鉴别诊断及b值优化

目的:探讨3.0T扩散加权成像(DWI)在乳腺良恶性病变鉴别诊断中的诊断价值并对b值使用进行优化。方法:34例患者共20个良性和16个恶性乳腺病灶纳入研究,同期20例正常乳腺受检者列为对照组。采用3.0T MR行乳腺DWI成像检查,b值分别取0,750 s/mm2,1000 s/mm2,1250 s/mm2。比较不同b值DWI图像质量,测量病灶的对比噪声比(CNR)以及表观扩散系数(ADC)值,以病理诊断为金标准,计算诊断乳腺癌的敏感度、特异度及准确性,绘制受试者工作特征曲线(ROC)并进行比较。结果:不同b值时DWI图像主观质量评分没有统计学差异(F=3.02,P=0.0516>0.05)。b=750 s/mm2时病灶的CNR明显优于b=1000s/mm2及1250s/mm2时(P值为0.004及0.000),而b=1000s/mm2与1250s/mm2之间没有统计学差异(P=0.800>0.05)。相同b值时,正常乳腺组织的平均ADC值>乳腺良性病变>乳腺恶性病变(P均=0.000)。以各b值恶性病变平均ADC值95%可信区间的上限作为界定乳腺癌ADC的阈值,则b=750 s/mm2、1000 s/mm2、1250s/mm2时,ADC阈值分别为1.33×10-3mm2/s、1.25×10-3mm2/s、1.16×10-3mm2/s。以上述阈值判断乳腺癌的敏感度、特异度及准确性分别为81.25%、87.5%、85.71%,81.25%、77.5%、78.57%及81.25%、82.5%、82.14%。三个b值的ROC曲线下面积无显著性差异(P=0.1925>0.05)。结论:乳腺的3.0T DWI中,以b=750s/mm2时病灶CNR最高,值得推荐应用。应用DWI鉴别乳腺良恶性病变时,需要结合ADC值判断。     

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 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.     

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).     

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.