乳腺癌MR动态增强扫描定量分析及其临床应用

对于乳腺癌的检出,乳腺MR成像被认为是一种具有高敏感性和较高特异性的检查方式.动态增强MRI定量分析可以通过Ktrans、kep、ve等多种参数的应用,量化评价肿瘤组织的血管内皮通透性和血流量.其较半定量分析能更为准确、客观地诊断肿瘤的良恶性及评价治疗疗效.就应用动态增强MRI定量分析乳腺癌的现状及目前所存在的问题作一综述.     

前交叉韧带损伤影像学研究进展

常规MRI对于诊断前交叉韧带(ACL)损伤具有一定的局限性.本文主要介绍定量分析技术在ACL损伤诊断中的应用进展,这些技术包括扩散加权成像(DWI)、扩散张量成像(DTI)及双能量CT(DECT),并探讨常规MRI和三维MRI在诊断ACL损伤中的价值.     

定量MRI在乳腺癌诊断中的研究进展

MRI已经成为诊断乳腺癌较为敏感的无创性检查技术,定量MRI包括动态增强MRI(DCE-MRI)、扩散加权成像(DWI)、体素内不相干运动DWI(IVIM-DWI)、合成MRI(SyMRI)、氢质子MR波谱成像(¹H-MRS)、MR弹性成像(MRE)、血氧水平依赖MRI(BOLD-MRI)等,可以对乳腺癌进行定量分析,从而有助于诊疗策略制定、预后判断及疗效评价。就定量MRI在乳腺癌诊断中的研究进展予以综述。     

肾细胞癌的MRI研究进展

肾细胞癌是最常见的成人肾脏恶性肿瘤。近年来，多种功能MRI成像技术（如扩散加权成像、灌注加权成像等）、多参数MRI联合分析以及影像组学等新兴影像处理技术被证实在肾细胞癌的诊断中具有较大的价值。目前，研究热点多集中于良恶性肿瘤的鉴别、组织学亚型的区分、肿瘤分期、预测核分级及判断预后。就MRI新技术及图像处理技术在肾细胞癌中的研究进展予以综述。     

定量MRI诊断直肠癌淋巴结转移的研究进展

评估直肠癌淋巴结转移对治疗和预后至关重要。常规MRI诊断直肠癌淋巴结转移主要依据淋巴结的短径和形态学特征,诊断效能较低。定量MRI包括动态增强MRI（DCE-MRI）、动态磁敏感增强MRI（DSC-MRI）、单指数模型扩散加权成像（DWI）、扩散峰度成像（DKI）、体素内不相干运动扩散加权成像（IVIM-DWI）等,可以对直肠癌淋巴结及原发灶进行定量分析,从而有助于诊断淋巴结转移。就常规MRI及定量MRI诊断直肠癌淋巴结转移的研究进展予以综述。     

胃CT灌注成像的研究进展

灌注成像（perfusion imaging）是指通过影像学设备直观显示活体组织的灌注过程和作定量或半定量分析的方法,主要包括单光子发射断层成像（SPECT）、正电子发射断层成像（PET）以及CT和MRI灌注成像等.     

磁共振成像在肾移植后的应用和进展

随着肾移植手术成功率的不断提高,其术后监测日益引起人们的关注,而目前用于肾移植术后监测的各种检查存在着诸多不尽人意之处.磁共振成像(MRI)具有良好的软组织对比、多层面成像能力及无创等特点,在肾移植术后监测方面具有很大的潜能.常规MRI已为大家所熟悉,钆增强MRI可以有效地评价肾脏形态、灌注及功能;磁共振血管成像(MRA)在肾移植病人这一特殊人群中已经开展,初步结果很令人满意;磁共振尿路成像(MRU)在肾移植病人应用的早期资料表明尿路显影良好,与普通人群的MRU成像质量无明显差异;其它几种磁共振方法均各有优势,相信随着MRI的发展,也会逐步进入肾移植病人这一特殊人群,成为肾移植术后MRI监测的一种有效手段.     

3.0T MRI BOLD成像技术在评价正常大鼠肾脏氧含量的实验研究

目的 探讨3.0T MRI BOLD成像技术在评估正常大鼠肾脏氧代谢的价值.方法 29只SD大鼠麻醉后行3.0T MRI 常规及BOLD序列扫描,分别测量大鼠左右肾脏皮质、外髓及内髓的T2*值,从而计算R2*值(=1/ T2*值).结果 正常大鼠左右肾脏皮质R2*值分别为(28.84±3.11)s-1及(30.20±3.48) s-1;外髓R2*值分别为(32.77±3.07) s-1及(31.76±2.73) s-1;内髓R2*值分别为(28.37±2.80) s-1及(29.54±2.42) s-1.结论 磁共振BOLD成像技术可监测肾脏皮髓质氧代谢变化情况,从而评估肾脏疾病的功能损害程度.     

功能MRI在评价对比剂诱导急性肾损伤中的研究进展

对比剂诱导急性肾损伤（CI-AKI）是注射碘对比剂后严重的并发症之一,早期诊断和治疗可以改善或延缓肾损伤。目前多种功能MRI（fMRI）技术可用于肾损伤后肾脏微循环和病理生理学的评估,包括扩散加权成像（DWI）、体素内不相干运动（IVIM）成像、扩散张量成像（DTI）、扩散峰度成像（DKI）、血氧水平依赖（BOLD）成像、动脉自旋标记（ASL）成像等。这些技术不但可以对肾功能损害进行定量分析,还可以在肾损伤的早期诊断和监测方面提供更多信息。就CI-AKI的发病机制及fMRI评价CI-AKI的研究现状做一综述。     

MRI中T_1W WATS/FFE序列在肾脏疾病中的应用价值

目的:探讨MRI中T1加权选择水激励梯度回波成像(T1W/WATS/FFE)序列在肾脏疾病检查中的应用价值。方法:对临床拟诊和CT及超声检查后诊断为肾脏病变的211例患者,应用MRI中T1W/WATS/FFE序列进行扫描,分析该序列在肾脏疾病成像中的特点。结果:显示正常肾脏28例。肾脏病变183例,其中良性病变166例,恶性肿瘤17例。肾脏显示分为良好、一般、差三种,肾脏显示良好207例,一般2例,差2例。结论:MRI中T1W/WATS/FFE序列能很好地显示肾脏的结构,与周围组织和器官及病变对比度增加,扫描速度快成像时间短,图像质量高,能够满足临床的诊断要求。     

Renal cancer staging: Comparison of contrast-enhanced CT and gadolinium-enhanced fat-suppressed spin-echo and gradient-echo MR imaging

Fifty-three consecutive patients with 61 solid or complex non-fat-containing renal masses compatible with renal cancer were examined with contrast-enhanced computed tomography (CT) and magnetic resonance (MR) imaging with pre- and postcontrast FLASH (fast low-angle shot) and fat-suppressed spin-echo sequences. CT and MR imaging were performed within a 1-month interval. CT and MR images were prospectively interpreted. Tumor detection and staging were determined in all patients. CT and MR imaging enabled detection of 54 and 58 of 61 renal tumors, respectively. CT and MR imaging showed 34 and 35 of 38 histologically proved renal tumors, respectively, in 31 patients. Tumor size on CT and MR images demonstrated good correlation and correlated well with the size of pathologic specimens of 34 of 38 resected tumors detected with CT and MR imaging (r =.99). Of the 31 tumors in 31 patients who underwent surgical resection, 24 were correctly staged with CT and 29 with MR imaging. CT and MR imaging both enabled correct staging of four of five additional tumors with biopsy proof of tumor stage. A moderate difference in staging was observed between CT and MR imaging (P =.05). CT showed 13 and MR imaging 15 of 15 tumor thrombi. CT and MR imaging both showed 11 of 11 cases of adenopathy. The results suggest that MR imaging is moderately better than CT for the detection and staging of renal cancer.     

MR-Bildgebung der Nieren Neue Ansätze in der Diagnostik*

AIM: New diagnostic strategies for evaluation of the kidney by fast MR imaging techniques. MATERIAL AND METHODS: A comprehensive morphologic and functional evaluation of the kidney is proposed using fast MR imaging of renal morphology, multiphase 3D gadolinium MR angiography, MR urography and MR flow measurements. A single MR examination is designed to grade renovascular disease and assess the hemodynamic and functional significance, detect and characterize renal lesions and evaluate the urinary tract. RESULTS: The combined analysis of morphologic and functional data allows reliable assessment of renal artery stenosis, benign and malignant renal masses and diseases of the renal collecting system and ureters, as well as congenital abnormalities in good agreement to the results of conventional imaging modalities. The improved tissue contrast and additional functional information compensates for the disadvantage of a lower spatial resolution. CONCLUSION: Combined morphologic and functional MR examination represents a reliable, non-invasive and cost-effective alternative imaging modality for comprehensive diagnostic evaluation of renal disease.     

MR imaging of renal function

MR imaging is the only single noninvasive test that can potentially provide a complete picture of renal status with minimal risk to the patient, simultaneously improving diagnosis while lowering medical costs by virtue of its being a single test. The strengths of MR imaging lie in its high spatial and temporal resolution and its lack of exposure to ionizing radiation and nephrotoxic contrast agents. This article reviews the use of MR imaging for quantification of renal functional parameters and its application to clinical problems, such as RVD, hydronephrosis, and renal transplantation. Although advances in both the technical and clinical aspects of functional renal MR imaging have been made, much remains to be done. The preliminary results reported in the many studies reviewed are exciting, but these techniques need to be validated against accepted standards where such standards exist. In addition, and perhaps more important, the effects of these new diagnostic methods on patient outcomes must be studied. Finally, further progress in image processing and analysis must be made to make functional renal MR imaging truly practical. With these advances, one can expect functional renal MR imaging to play an ever-expanding and influential role in the care and management of the patient with renal disease.     

Gadolinium-enhanced MR imaging of renal masses.

Preliminary reports indicate that gadolinium-enhanced magnetic resonance (MR) imaging is highly accurate for diagnosis of renal masses. The authors demonstrate the clinical utility of MR imaging for evaluating renal masses in 26 patients for whom contrast material-enhanced computed tomography (CT) was contraindicated or inadequate for diagnosis or staging. Nine patients had complex cysts, one had a perinephric hematoma, and 16 had a solid mass (three of which were benign). All patients underwent MR imaging before and after administration of gadopentetate dimeglumine. Multiple imaging techniques and sequences were used. All tumors and no cysts enhanced with gadolinium. Even though the three benign tumors enhanced, two were differentiated from renal carcinoma on the basis of other imaging features. Unenhanced MR imaging was accurate in staging of renal carcinomas, and use of gadolinium did not improve staging accuracy. Gadolinium-enhanced MR imaging is indicated when results of CT and sonography are indeterminate for malignancy and when contrast-enhanced CT is contraindicated because of renal failure or adverse reaction to iodinated contrast material. In this latter instance, MR imaging is useful for both diagnosis and staging.     

Diffusion-weighted MR imaging of native and transplanted kidneys

Applications of diffusion-weighted (DW) magnetic resonance (MR) imaging outside the brain have gained increasing importance in recent years. Owing to technical improvements in MR imaging units and faster sequences, the need for noninvasive imaging without contrast medium administration, mainly in patients with renal insufficiency, can be met successfully by applying this technique. DW MR imaging is quantified by the apparent diffusion coefficient (ADC), which provides information on diffusion and perfusion simultaneously. By using a biexponential fitting process of the DW MR imaging data, these two entities can be separated, because this type of fitting process can serve as an estimate of both the perfusion fraction and the true diffusion coefficient. DW MR imaging can be applied for functional evaluation of the kidneys in patients with acute or chronic renal failure. Impairment of renal function is accompanied by a decreased ADC. Acute ureteral obstruction leads to perfusion and diffusion changes in the affected kidney, and renal artery stenosis results in a decreased ADC. In patients with pyelonephritis, diffuse or focal changes in signal intensity are seen on the high-b-value images, with increased signal intensity corresponding to low signal intensity on the ADC map. The feasibility and reproducibility of DW MR imaging in patients with transplanted kidneys have already been demonstrated, and initial results seem to be promising for the assessment of allograft deterioration. Overall, performance of renal DW MR imaging, presuming that measurements are of high quality, will further boost this modality, particularly for early detection of diffuse renal conditions, as well as more accurate characterization of focal renal lesions.     

Clinical use of urinary tract magnetic resonance imaging

MR imaging should not be used to evaluate the majority of the lesions described herein but should be reserved for specific clinical situations. The detection and differential diagnosis of adrenal masses is a legitimate application of this technique. The staging of renal tumors in patients in whom CT fails to do so may be accomplished by MR imaging. Establishment of patency of the renal veins and of surgical shunts involving these veins may be performed by MR imaging if Doppler ultrasonography proves unsatisfactory. MR imaging may differentiate between stable retroperitoneal fibrosis and malignant disease in patients in whom this differential is a problem. Hematomas may be distinguished from nonhemorrhagic fluid collections anywhere in the abdomen or pelvis. In selected patients, the local extent of certain bladder tumors may be evaluated by MR imaging when CT and biopsy fail to do so. In testicular disease, MR imaging may aid in the differential diagnosis of abnormalities that are not sufficiently characterized by ultrasonography, and MR imaging may detect undescended testes in some patients in whom ultrasonography fails to do so. In the future, wider application of fast scanning with bolus administration of soluble paramagnetic contrast agents may refine the differential diagnosis of adrenal masses and aid in the detection of renal masses. MR angiographic techniques ultimately may constitute a screening procedure for renal arteriostenosis. A subset of patients with prostate carcinoma may prove to benefit from local staging of the disease by MR imaging.     

Renal artery velocity mapping with MR imaging

An MR phase imaging sequence with a very short echo time was used to assess blood velocity and flow at the renal artery bifurcation. Cardiac-gated MR imaging data were obtained in six healthy subjects in sagittal planes adjacent to the abdominal aorta and transverse planes above and below the renal artery bifurcation. Average renal artery flow rate was 23.8 ±9 mL/sec. A strong individual variability was found for the velocity profiles in the abdominal aorta during end-systolic regurgitation. Flow rate was also determined in three patients with reduced renal artery blood flow. Two patients received therapy with percutaneous transluminal angioplasty. The successful outcome was documented with MR imaging. A reliable assessment of renal artery flow with MR phase imaging is feasible. Measurement of the velocity profiles yields valuable insights in the complicated flow regime at the renal artery bifurcation.     

Imaging end-stage kidney disease in adults. Low-field MR imaging with magnetization transfer vs. ultrasonography

Purpose: To 1) assess the potential of magnetization transfer (MT)-weighted MR imaging to improve the often poor visibility of native kidneys in patients with a renal transplant; and 2) compare low-field MR imaging and ultrasonography (US) for imaging these fibrotic kidney remnants.Material and Methods: Seventy-two native kidneys of 36 patients were prospectively evaluated with US and MR. In low-field (0.1 T) MR imaging, T1-, T2- and MT-weighted sequences were used. MT-weighted images were compared with T2-weighted images in their ability to delineate the kidneys from their surroundings whereas US and MR were compared for detection of renal cysts and possible solid tumors.Results: MT-weighted images proved superior to conventional T2-weighted images in producing contrast between the kidney remnants and their fatty surroundings. Although US revealed a few small renal cysts that were not seen at MR images, no statistical difference was found between the two modalities in this respect.Conclusion: MT imaging, due to its unique protein-specific signal depression, offers significantly improved visualization and delineation of end-stage kidneys. US, because its better availability and cost-benefit ratio, remains the method-of-choice compared to low-field MR imaging in detecting cysts in multicystic kidneys. MR investigation is helpful in selected patients and may be used as an alternative.     

Kidneys in infants and children: evaluation with MR

Magnetic resonance (MR) imaging was performed in 58 children aged 1 day to 17 years. In 43 patients with suspected renal abnormalities, the results of MR were compared with those obtained by ultrasonography, computed tomography, or excretory urography. The remaining 15 children with no known renal disease were initially imaged to define the appearance on MR images of the normal kidneys according to the child's age. The signal intensity from hilar adipose tissue increased with age; corticomedullary differentiation was best seen in younger children. Compared with other imaging modalities, MR added useful information in evaluating the complications associated with renal failure and in patients with renal neoplasms. The use of MR in children with possible renal disease is limited, and the modality should be used as an adjunct to renal ultrasonography in a carefully selected group of patients.     

Magnetic resonance imaging in the assessment of urologic disease: an all-in-one approach

The aim of this study was to evaluate an “all-in-one” MR procedure to examine the kidneys, the renal vascular supply and renal perfusion, and the urinary tract. In 64 patients (58 with urologic disease and 6 healthy volunteers), MR was performed including: (a) T1- and T2-weighted imaging; (b) 3D contrast-enhanced MR angiography (MRA), including the renal arteries, renal veins, as well as renal perfusion; and (c) 3D contrast-enhanced MR urography (MRU) in the coronal and sagittal plane. For the latter, low- and high-resolution images were compared. Prior to gadolinium injection, 0.1 mg/kg body weight of furosemide was administered intravenously. The results were compared with correlative imaging modalities (ultrasonography, intravenous urography, CT), ureterorenoscopy and/or surgical–pathologic findings. Visualization of the renal parenchyma, the vascular supply, and the collecting system was adequate in all cases, both in nondilated and in dilated systems and irrespective of the renal function. One infiltrating urothelial cancer was missed; there was one false-positive urothelial malignancy. Different MR techniques can be combined to establish an all-in-one imaging modality in the assessment of diseases which affect the kidneys and urinary tracts. Continuous refinement of the applied MR techniques and further improvements in spatial resolution is needed to expand the actual imaging possibilities and to create new tracts and challenges in the MR evaluation of urologic disease. Received: 27 September 1999; Revised: 20 January 2000; Accepted: 22 May 2000