【作者】 李亮；

【导师】 王良；

【作者基本信息】 华中科技大学 ， 影像医学与核医学， 2015， 博士

【摘要】 第一部分读出方向分段采样EPI模体实验及在正常前列腺DWI的初步应用目的：单次激发平面回波(Single-shot echo planner imaging, SS-EPI)是临床上DWI最为常用的成像方法。该技术在DWI相位编码方向上极易导致图像扭曲、解剖变形、空间分辨率和信噪比(SNR)降低。读出方向分段采样平面回波(Readout-segmented echo planner imaging, RS-EPI)是近年来研发出来的多次激发EPI序列的一种,它可以有效减少图像变形和磁敏感伪影。本研究旨在通过模体实验和正常人体的前列腺RS-EPI弥散成像研究,证实该技术在前列腺DWI检查中的初步临床应用。材料与方法：采用美国模体实验室研制的Magphan SMR100核磁共振性能检测模体。扫描常规SS-EPI、高分辨率SS-EPI及RS-EPI三种DWI成像方法,分别在模体中测量SNR、空间分辨率、几何变形、对比分辨率4个指标。在体实验部分,应用3.0T磁共振扫描仪对10名健康志愿者的前列腺进行以上三种DWI技术扫描,进行定性和定量评估图像质量。前列腺外周带和移行带定量评估参数包括SNR和表观弥散系数(Apparent diffusion coefficient, ADC)。模体研究和在体前列腺研究中,SS-EPI和RS-EPI组间比较均采用配对Wilcoxon秩和检验。结果：模体实验表明,RS-EPI弥散成像在SNR、空间分辨率、几何变形、对比分辨率等4个方面全面优于常规SS-EPI和高分辨率SS-EPI(P均<0.05)。在SS-EPI中,随着矩阵和扫描时间的提高,几何变形并没有得到抑制。在体的研究发现,RS-EPI弥散成像的图像质量要高于常规SS-EPI和高分辨率SS-EPI(P均<0.05)。正常前列腺的SNR和ADC在三者DWI方法中的比较并没有统计学差异(P均>0.05)。结论：RS-EPI可以有效抑制弥散加权成像的磁敏感伪影,减少解剖变形,在体研究也证明了该技术在正常前列腺DWI应用的初步可行性,并为接下来的前列腺疾病谱研究奠定了实验理论基础。第二部分读出方向分段采样EPI在前列腺疾病DWI中的临床可行性研究目的：常规DWI成像速度快,但在特殊部位检查中,如前列腺区域,受磁敏感伪影的影响较大,且随着磁共振场强的增加而愈发严重。RS-EPI可以有效抑制弥散加权成像的磁敏感伪影,减少解剖变形。但该技术在前列腺疾病的临床应用国内外还少有报道,本研究旨在将RS-EPI弥散成像应用于前列腺疾病的临床检查中,通过与常规SS-EPI的对比,明确该技术在前列腺DWI成像质量方面的优势。材料与方法：2013年5月至2015年1月期间来我院申请前列腺MRI检查者共478人。经严格筛选后,252例原发性前列腺疾病患者进行了常规MRI检查,并加做DWI扫描,包括常规SS-EPI和RS-EPI两种方法。由2名泌尿生殖系统放射影像医生采用Likert5分法,分别对两者的DWI图像锐利度、解剖变形、病灶对比度、可见度、细节显示和总的图像质量6个指标进行定性评估。定量测量两者DWI病灶的对比噪声比(Contrast-to-noise ratio,CNR)和ADC值。两位阅片者评分间的一致性采用κ检验和Bowker对称性检验。常规SS-EPI和RS-EPI两组间比较采用配对Wilcoxon秩和检验或配对t检验。结果：2位阅片者在评价图像锐利度、解剖变形、病灶对比度、可见度、细节显示和总的图像质量的κ值分别是0.76、0.79、0.52、0.55、0.63、0.65。Bowker对称性检验的P值均大于0.05。常规SS-EPI前列腺弥散成像在这6个方面的评分为2.88±0.62、2.94±0.62、3.32±0.79、3.02±0.71、3.08±0.53、3.12±0.72。RS-EPI的评分是4.24±0.80、4.38±0.64、3.72±0.73、3.96±0.61、4.20±0.76、4.16±0.68。RS-EPI前列腺弥散成像的图像质量要高于常规SS-EPI：P均<0.05)。两者的CNR部分存在统计学差异(P<0.05),而ADC在两者DWI方法中的比较并无显著差异(P均>0.05)。结论：RS-EPI在前列腺疾病弥散成像检查中的临床应用是可行的。与常规SS-EPI序列相比,该技术可以显著减少因磁敏感伪影而导致的前列腺区域图像变形和图像模糊,从而得到高分辨率高质量的前列腺DWI图像,并为将来的前列腺疾病精确病理对照研究提供可靠的影像学依据,值得大力宣传及推广。第三部分读出方向分段采样EPI在前列腺癌DWI中的临床应用价值目的：DWI可以提供组织内水分子运动的信息,从而反映正常和异常组织内病生理结构的变化。国内外大量研究均报道,DWI在前列腺癌的诊断、定位、分期、靶向穿刺以及术后疗效评估等方面的重要价值。RS-EPI作为一种全新的DWI成像技术,它可以有效抑制常规SS-EPI所产生的磁敏感伪影,得到高分辨率无变形的DWI图像。本研究旨在将RS-EPI序列应用于前列腺癌DWI检查中,探讨其对DWI图像质量及定量测量参数的影响。材料与方法：2013年5月至2015年1月期间来我院行前列腺MRI检查者共252例。回顾性分析前列腺癌患者共58例,均经穿刺或手术(根治或电切)病理证实。病理结果在MRI检查后1月内获得,所有患者在MRI检查前均未进行过穿刺、冷冻、手术、内分泌及放化疗等治疗。前列腺MRI检查包括常规T2WI、高分辨率SS-EPI和RS-EPI弥散成像。由2名泌尿生殖系统放射影像医生采用Likert5分法,分别对两者的DWI图像锐利度、解剖变形、病灶对比度、可见度、细节显示和总的图像质量6个指标进行定性评估。定量测量两者DWI癌灶的SNR、对比度、CNR和ADC值。对比两种不同DWI技术在前列腺癌临床扫描中的图像质量差异。高分辨率SS-EPI和RS-EPI两组间比较采用配对Wilcoxon秩和检验。两种DWI测量参数的相关性检验采用Pearson相关分析的方法。结果：RS-EPI前列腺癌弥散成像在解剖变形、病灶对比度、可见度以及总的图像质量明显优于高分辨率SS-EPI(P<0.05),而在锐利度和解剖细节显示2方面无统计学差异(P>0.05)。两者的SNR、对比度均存在统计学差异(P<0.05)。而在CNR和ADC值对比中,无差异(P>0.05)。两种DWI成像技术测量SNR、病灶对比度、CNR及ADC均呈正相关,相关系数r分别为0.712、0.823、0.625、0.872,均具有统计学意义(P<0.05)。结论：RS-EPI在前列腺癌弥散成像中的总图像质量要优于高分辨率SS-EPI.该技术可以有效减少前列腺癌DWI图像变形和图像模糊,提高小病灶的显示率,为将来新型磁共振DWI引导下的精确病理穿刺奠定了基础,对于前列腺癌的早期诊断及鉴别具有较高的指导意义,应用前景广阔。更多还原

【Abstract】 Part Ⅰ Readout-Segmented Echo-Planar Imaging for Diffusion-Weighted Imaging: Phantom Experiment and Preliminary Application in Normal ProstateObjective:Single-shot echo-planar imaging (SS-EPI) is currently the sequence used most routinely for clinical studies in DWI. However, susceptibility artifacts and image blur can be severe, particularly at3T, due to the long EPI readout and corresponding low bandwidth per pixel in the phase-encoding direction. Readout-segmented echo-planar imaging (RS-EPI) has been suggested as an alternative to SS-EPI for diffusion-weighted imaging (DWI) with reduced distortion. The purpose of the current study is to evaluate the performance of RS-EPI DWI in phantom experiment and compare it with the SS-EPI method in normal prostate.Materials and Methods:A MRI phantom called Magphan SMR100(Pat No:5165050) developed by U.S.A. phantom laboratory was tested. The phantom was scanned at3T with conventional SS-EPI, high resolution and RS-EPI. Imaging studies were evaluated for signal-to-noise ratio (SNR), spatial resolution, geometric distortion and contrast resolution. Qualitative and quantitative evaluation of image quality at3T in10healthy volunteers were obtained using above three different prostate DWI. quantitative assessment parameters include SNR and apparent diffusion coefficient (ADC) were also measured in peripheral zone and transition zone. A paired Wilcoxon rank sum test was used for statistical analysis in phantom experiment and in vivo prostate study.Results:In phantom experiment, SNR, spatial resolution, geometric distortion, and contrast resolution were rated significantly better by both readers for RS-EPI technique (P<0.05for all parameters). In the SS-EPI, as the matrix and scan time increasing, geometric distortion has not been suppressed. In vivo prostate study, RS-EPI reduced significantly geometric distortions and blurring, and improved image quality in the volunteers, compared to SS-EPI (P<0.05). There were no statistically significant difference in ADC and SNR between the two methods (P>0.05).Conclusion:RS-EPI DWI can effectively suppress magnetic susceptibility artifacts, reduce anatomical distortions. RS-EPI is a feasible technique in the normal prostate DWI for producing high-resolution DWI and subsequent in prostate disease lay theoretical foundation. Part Ⅱ Clinical Feasibility of Readout-Segmented Echo-Planar Imaging for Diffusion-Weighted Imaging in Prostate Disease at3TObjective:Conventional DW imaging speed is very fast, but in particular parts of the examination, such as the prostate, is affected by magnetic susceptibility artifacts. With increasing field strength, these effects are even more prominent. RS-EPI DWI can effectively suppress magnetic susceptibility artifacts and reduce anatomical distortion. However, the clinical application of this technology in prostate disease is rarely reported. The purpose of this study was to demonstrate the feasibility of the RS-EPI technique in DWI of the prostate disease and to compare the image quality of RS-EPI DWI of the prostate with conventional SS-EPI diffusion images on a3T clinical scanner.Materials and Methods:A total of478adult patients apply for prostate MRI examination in our hospital between May2013and January2015. After rigorous screening,252cases of primary prostate disease patients underwent conventional MRI, and a plus DWI scans, including conventional SS-EPI and RS-EPI in two ways. Two genitourinary observers (blinded to which sequence was reviewed) evaluated the DW images acquired on the252patients by using RS-EPI and conventional SS-EPI, scoring them in terms of sharpness, distortion level, lesion contrast, lesion conspicuity, detailed anatomical visualization and overall image quality on a5-point Likert scale (1, nondiagnostic;5, excellent). Lesion contrast noise ratio (CNR) and ADC values were calculated. Agreement between two readers was assessed with weighted κ and exact Bowker test of symmetry. Differences in image quality and image parameters between conventional SS-EPI and RS-EPI were compared using the Wilcoxon rank sum test or paired t test.Results:The κ value were0.76,0.79,0.52,0.55,0.63,0.65for image sharpness, anatomical distortion, imaging contrast, lesion conspicuity, detailed anatomical visualization and overall image quality (all P<0.05), indicating moderate to substantial agreement between the two observers. Bowker test of symmetry P values were greater than0.05. The mean Likert scores for conventional SS-EPI and RS-EPI were as follows:image sharpness,2.88±0.62and4.24±0.80; distortion level,2.94±0.62and4.38±0.64; contrast,3.32±0.79and3.72±0.73; lesion conspicuity,3.02±0.71and3.96±0.61; detailed anatomical visualization,3.08±0.53and4.20±0.76; and overall image quality,3.12±0.72and4.16±0.68, respectively. RS-EPI DWI requires significantly better image quality and reduces susceptibility artifacts than conventional SS-EPI (all P<0.05). The conventional SS-EPI was superior to RS-EPI in CNR (P<0.05), whereas there were no significant differences in ADC between SS-EPI and RS-EPI (P>0.05).Conclusion:RS-EPI is a feasible technique in the prostate for producing high-resolution DW images with reduced geometric distortion and reduced blurring and offers potentially superior image quality compared to conventional SS-EPI technique at3T. This technique could provide reliable imaging evidence for future accurate prostatic disease-pathology control studies, should be vigorously publicity and promotion. Part Ⅲ Clinical Application of Readout-Segmented Echo-Planar Imaging for Diffusion-Weighted Imaging in Prostate Cancer at3TObjective:DWI is based on the random motion characteristics of water molecules and it enables investigation of the architecture of the biological environment. In the prostate study, DWI is widely used for differentiating malignant from benign prostatic tissues, and assessing cancer staging, biological potential, treatment planning, therapy response and local recurrence. As a new imaging technology, RS-EPI can effectively suppress DWI susceptibility artifacts produced by conventional SS-EPI to obtain high-resolution images without distortion. The purpose of this study was to implement RS-EPI DWI on a clinical scanner at3.0T for prostate cancer imaging and to explore its impact on the image quality and quantitative measurement parameters.Materials and Methods:A total of252clinical patients underwent3.0T prostate MRI examination in our hospital between May2013and January2015. Fifty-eight patients with prostate cancer which were confirmed by biopsy or surgery (radical or TURP) pathology were retrospectively analyzed. Pathological findings were obtained within one month after the MRI examination. All patients had not received any treatment for prostate cancer (i.e., androgen ablation, radiotherapy, chemotherapy, radical surgery, cryosurgery). Images were obtained using RS-EPI and high resolution SS-EPI with an identical scanning time, acceleration factor, target resolution, and image post-processing procedure. Two genitourinary observers (blinded to which sequence was reviewed) evaluated the DW images acquired on the58patients by using RS-EPI and high resolution SS-EPI, scoring them in terms of sharpness, distortion level, lesion contrast, lesion conspicuity, detailed anatomical visualization and overall image quality on a5-point Likert scale (1, nondiagnostic;5, excellent). SNR, contrast, CNR and ADC values of tumors were calculated. Image quality differences were compared between two different DWI techniques in prostate cancer clinical scanning. Differences in image quality and image parameters between conventional SS-EPI and RS-EPI were compared using the Wilcoxon rank sum test. The relationship between parameters measured in two different DWI methods was analyzed by the method of Pearson correlation test.Results:RS-EPI was superior to high resolution SS-EPI in distortion level, lesion contrast, visibility and overall image quality(all P<0.05), whereas there were no significant differences in sharpness and anatomical details between RS-EPI and high resolution SS-EPI (P>0.05). There were significant differences in SNR and contrast between the two DWI techniques (P<0.05), but no differences in CNR and ADC (P>0.05). The comparison of SNR, lesion contrast, CNR and ADC between the two DWI techniques showed a positive correlation (r=0.712,0.823,0.625,0.872), were statistically significant (P<0.05).Conclusion:RS-EPI diffusion imaging is superior to the high-resolution SS-EPI in the aspect of overall image quality in prostate cancer DW MR imaging. This technology can effectively reduce prostate DWI image distortion and blurring, increase the rate of small lesions display. RS-EPI DWI is a robust tool to delineate the lesion contour and may accurately define the target for biopsy, has a higher significance application prospects for the early diagnosis and identification of prostate cancer.更多还原