Magnetic resonance imaging features of aortic diseases

The usefulness of magnetic resonance imaging (MRI) for aortic diseases is discussed, with special attention given to the MRI features of aortic dissection and Takayasu arteritis. Computed tomography (CT) and MRI provide excellent visualization of vessels and their relationship to surrounding structures; however, CT depicts the vessel lumen optimally only when contrast enhancement is used. MRI, with its inherent multiplanar imaging capability, is well suited for evaluation of the thoracic and abdominal aorta and can be used with or without contrast enhancement. Basic technical considerations in cardiac imaging, which include conventional spin-echo, fast spin-echo, cine gradient, and echo-planar imaging, with time-of-flight and phase-contrast methods, are discussed and applied to aortic aneurysm, aortic dissection, and Takayasu arteritis. The diagnostic capacity of spin-echo MRI in patients with suspected aortic dissection is enhanced when it is combined with cine MRI. Despite the ability of CT and MRI to demonstrate luminal and mural changes of aortic abnormalities, conventional angiography still may be necessary at first admission for selected patients in the late occlusive phase to provide additional information on the degree and extent of the arteritis. CT angiography and MR angiography are promising imaging techniques that will overcome difficulties in visualizing distal branch vessel lesions and obviate the need for conventional angiography in the near future.     

Magnetic resonance imaging of renal disease: recent developments and future applications

Magnetic resonance imaging (MRI) offers the ability to non-invasively assess parenchymal and vascular renal disease. Indications for renal MRI include the evaluation of renal masses, urinary obstruction and infection, renal vasculature, and the health of transplant kidneys. The potential of MR angiography to replace invasive conventional x-ray angiography has been recognized for many years. Recent developments in MRI resulting from fast MR systems with faster gradients, new surface coil designs and the latest sequence developments coupled with innovative contrast agent administration strategies have prompted substantial progress of MRI in the diagnosis of renal disease. The goal of this article is to present the current state of MRI in diagnosing renal disease, with an emphasis on the latest developments in the evaluation of renal vascular disease.     

Whole Body MR Angiography Screening

Lack of side effects, diagnostic accuracy and recent improvements in technology qualify magnetic resonance imaging for preventive cardiovascular imaging. The purpose of this study was to assess the feasibility of a comprehensive contrast-enhanced three-dimensional whole-body MR (magnetic resonance) angiography examination technique using a rolling table platform system with a 1.5-T MR system. The examination yielded diagnostic image quality in 5312 out of 5400 (98.3%) evaluated vascular segments in 180 consecutive patients with peripheral vascular disease. Besides the proved peripheral vascular disease, additional relevant vascular disease was found in 65 vessel segments in 42 patients: carotid artery stenosis (n = 21), subclavian artery stenosis (n = 5), renal artery stenosis (n = 27) abdominal aortic aneurysm (n = 7), aortic dissection (n = 5). In 20 patients additional imaging studies confirmed the results of whole-body MRA without false positive or false negative findings. The described whole-body MR angiography protocol appears well suited for comprehensive evaluation of the arterial system beyond the peripheral vasculature.     

Computed tomography of renal masses

Computed tomography (CT) has provided a valuable imaging modality for the study of renal masses. Simple cysts are the most common of renal masses, and they are usually readily differentiated by CT from the wide variety of solid tumors that affect the kidneys. This article describes the CT technique which is used for evaluation of renal masses; the CT appearances of such renal tumors as renal cell carcinoma, renal pelvic carcinoma, lymphoma, oncocytoma, and angiomyolipoma and the use of CT in the staging of malignant renal tumors. The CT findings in various renal cystic diseases are also described. The role of CT for evaluating renal masses in relation to such other imaging techniques as sonography and angiography is discussed.     

Functional magnetic resonance imaging in renal artery stenosis

Renal artery stenosis (RAS) is the leading cause of secondary hypertension. Magnetic resonance (MR) imaging and in particular MR angiography have evolved into important diagnostic tools for the detection and grading of RAS due to the lack of ionizing radiation and nephrotoxic contrast agent. This review describes state-of-the-art MR angiographic techniques and introduces the reader to current concepts of RAS grading with MR angiography. We compare MR angiography with conventional angiography and intravascular ultrasound as a standard of reference. The technical basis of functional imaging techniques such as arterial spin labeling perfusion measurements, contrast-enhanced perfusion measurements, and MR flow measurements are explained. Their value for the grading and detection of RAS and for the differentiation of renovascular from renal parenchymal disease is discussed. An overview about imaging during and after interventional therapy of RAS and an introduction to the current understanding of prediction of successful interventional therapy finishes this review.     

Magnetic resonance. Principles and applications

Magnetic resonance is a unique, noninvasive imaging modality which allows direct, multiplanar imaging and the possibility of obtaining biochemical information in vivo. Presently, MR appears most applicable to the evaluation of central nervous system abnormalities. The high sensitivity of MR in the evaluation of intracranial pathology suggests that it may eventually replace CT for many suspected diseases, if future investigations are able to improve its specificity. As previously noted, MR may be more diagnostic than other radiologic studies in the evaluation of suspected Chiari malformation, syringomyelia, congenital abnormalities, tumors of the spinal axis, and disc space infection. In the chest, MR appears to be more accurate than CT in the determination of the extent of mediastinal tumor, but at present cannot replace CT because of the lack of experience in imaging parenchymal nodules and benign diseases. MR of the breast is promising, but the size of the lesion may prove to be a limiting factor with magnetic field strengths commonly being utilized. There are inherent difficulties in the evaluation of cardiac disease with MR, but it offers a noninvasive method of investigating congenital heart disease and may provide valuable information in suspected myocardial ischemia and altered cardiac function. MR provides a new method of evaluating the vascular system, both in terms of providing anatomic information on large and medium-sized vessels and flow analysis. In the abdomen, MR appears to be most sensitive in the evaluation of suspected hepatic masses, but as with the brain, greater specificity will be needed to replace CT. At the present time, MR offers no distinct advantage over conventional imaging modalities in the evaluation of pancreatic disease, it maybe more accurate than CT in the staging of renal cell carcinoma. Larger studies are needed to determine the role of MR in the investigation of retroperitoneal adenopathy and adrenal abnormalities. In the pelvis, MR offers the hope of earlier diagnosis of prostatic carcinoma and may replace CT for staging of prostatic carcinoma and transitional cell carcinoma of the bladder. Limited MR experience with benign disease of the female pelvis suggests that it is currently more accurately evaluated with ultrasound. MR appears to be highly sensitive and specific for the diagnosis of avascular necrosis and may provide an early clue in suspected osteomyelitis. Finally, in vivo MR spectroscopy may provide unique metabolic information that was unobtainable prior to the advent of magnetic resonance, if this proves to be technically feasible.     

Renal involvement of polyarteritis nodosa: CT and MR findings

Background  To evaluate the imaging findings in patients with renal involvement of Polyarteritis nodosa (PN) to diagnose as early as possible. Materials and methods  Four patients diagnosed as having PN participated in the present study. Two patients underwent abdominal dynamic CT, one underwent only pre- and post-contrast CT, and the remaining patient underwent only noncontrast CT and MR imaging, including dynamic contrast study. Results  The common findings of CT and MR imaging were diffuse enlargement, multiple small wedge-shaped less-enhanced areas on dynamic contrast study, and indistinctness of the margin between the cortex and medulla on equilibrium-phase CT. Renal arteriogram showed multiple microaneurysms on arterial phase image in all four cases, and PN was diagnosed. The common CT and MR findings of renal involvement of PN mimicked those of pyelonephritis, when microaneurysms were not demonstrated. Conclusion  The differentiation between PN and pyelonephritis on CT and MR imaging is difficult. Therefore, the radiologist should be familiar with the imaging findings of renal involvement of PN. When PN is suspected, angiography should be performed as early as possible to make a definite diagnosis.     

MR imaging of the thoracic aorta

MR imaging has been incorporated into the diagnostic algorithm for suspected thoracic aortic pathology, challenging CT and invasive catheter angiography as investigations of choice. Techniques, including spin echo, 3-D steady-state free precession, cardiac cine imaging, phase-contrast flow quantification, and high-resolution contrast-enhanced magnetic resonance angiography, are poised to trump other single competitive modalities. The proliferation of 3-tesla systems has advanced the performance of magnetic resonance, aided by parallel imaging techniques, multiarray surface coils, and powerful gradient coils. This article considers the current status of MR imaging in evaluation of the thoracic aorta, with reference to common clinical indications in clinical practice.     

MR imaging of pulmonary and mediastinal malignancies

The primary goal of performing cross-sectional imaging of the chest in the radiologic evaluation of lung cancer is to obtain information about the character and magnitude of the neoplasm. Patient prognosis and therapy decisions depend directly on identifying the size and full extent of the tumor. The ideal imaging modality therefore should provide reliable information that can be used to assist in accurately staging the malignancy. Traditionally, CT scanning has been used exclusively as part of the preoperative evaluation of primary lung carcinomas. Recent advances in CT scanning technology have greatly improved image acquisition times and image quality and consequently have enhanced the role of CT imaging in the evaluation of bronchogenic carcinomas. Single-breath CT acquisitions of the chest can now be accomplished in a matter of seconds. These rapid acquisitions improve image quality by decreasing respiratory motion, while enhancing patient compliance and throughput. Clearly, CT scanning has matured into an efficient and accurate diagnostic tool to stage primary lung malignancies noninvasively. In its present state of development, MR imaging has one distinct disadvantage that makes it significantly less attractive as a routine lung cancer examination, namely the inability to produce images of the lung that are high in spatial resolution. Also, the sensitivity and specificity of MR imaging, which are similar to those of CT scanning in identifying mediastinal and hilar metastases, offer no clinical advantages. Longer image acquisition times and time constraints force most MR imaging examinations to be abbreviated and limited in coverage. As a result, the necessary exclusion of important anatomic areas routinely visualized by CT scanning may limit the diagnostic power of MR imaging. Finally, MR imaging requires greater physician supervision than CT scanning to direct imaging and to maintain examination quality and thoroughness. Although MR imaging can contribute significantly to the radiologic evaluation of patients with lung cancer, its role is somewhat limited, and it is most useful as a complement to CT scanning. The additional versatility offered by pulse sequences that take advantage of the intrinsic relaxation of tissues greatly facilitates identification of tumor, particularly when local invasion is present. By virtue of the short T1 value of fat, MR imaging may improve the detection of mediastinal disease, particularly in cases in which the sensitivity of CT scanning cannot be optimized because of allergies to contrast or renal insufficiency. MR imaging is superior to CT scanning in demonstrating musculoskeletal anatomy and the neurovascular structures of the neck and mediastinum. Although MR imaging has a potential usefulness in the radiographic evaluation of lung carcinoma, technical shortcomings relegate this modality to a role that is primarily complementary to CT scanning. With time, technological improvements will undoubtedly redefine the role of MR imaging in the radiographic evaluation and staging of bronchogenic carcinomas.     

高机械指数灰阶谐波超声造影评价肾动脉狭窄的初步研究

目的 评价高机械指数实时灰阶谐波超声造影诊断肾动脉狭窄的临床价值.方法 怀疑肾动脉狭窄者21例,包括3例肾移植术后患者,行常规彩色多普勒超声和谐波造影检查.使用SonoVue造影剂,机械指数设置在1.0左右.超声检查结果与X线血管造影、CT血管成像、磁共振血管成像检查结果相对照.结果 常规超声诊断肾动脉狭窄的敏感性、特异性、阳性预测值、阴性预测值及准确性分别为85.7%,57.1%,80.0%,66.7%及76.2%;结合谐波造影可分别提高到100%,66.7%,88.2%,100%及90.5%.结论 高机械指数谐波超声造影能够明显提高肾动脉与周围组织的回声对比,直观显示肾动脉的流道变化,有助于对肾动脉狭窄的诊断.     

CT 和MR三维血管成像技术对于TIPSS的价值

目的 探讨CT血管造影及MR血管造影对门脉高压患者TIPSS治疗的价值。方法 TIPSS术前10例患者进行了三维MR血管造影，2例用MR团注技术测量门脉血流速度。60例进行了三维CT血管造影。所有病例经临床和DSA证实为肝硬化门脉高压，其中，68例行TIPSS治疗。MR血管造影使用西门子1．5T MR机，CT血管造影使用GE High Speed CT／i扫描机。结果 MR血管造影：10例患者均可见门静脉主干及其肝内分支扩张，但其中2例有布加综合征的表现。3例患者可见侧支循环及静脉曲张，表现为胃左静脉丛和左肾静脉曲张、脾肾分流。应用MR“团块追踪”技术测量了2例门脉主干的血流速度，分别为11．8cm／s和10．6cm/s。CT血管造影：准确地显示了60例患者的肝动静脉解剖、门脉主干扩张及其小血管分支，以及19例侧支循环及曲张血管。结论 CT血管造影和MR血管造影是一种无创性的检查方法，可充分显示肝静脉和门静脉解剖及变异，为TIPSS术前提供了重要信息。CT血管造影的空间分辨率优于MR血管造影。     

MR imaging of the adrenal glands and kidneys

MR imaging of the adrenal glands and kidneys can completely and accurately assess these organs for a variety of abnormalities. One of the major strengths of MR imaging of the adrenal glands is the ability of chemical shift imaging to determine the presence of intracellular lipid, thus enabling distinction of benign adrenal adenomas from other adrenal masses. The multiplanar imaging capability of MR can assist in determining the origin of large retroperitoneal masses. MR imaging of the kidneys has many applications, including staging of renal cell carcinomas and evaluating the renal vasculature. Gadolinium is a safe and non-nephrotoxic contrast agent that can be used to evaluate the kidneys in patients with renal compromise. The many advances and current research being performed in the rapidly expanding field of abdominal MR make performing these cases both exciting and challenging.     

泌尿系统结石MSCT、MRU成像的对比分析

目的 本研究应用MSCT、MRU对泌尿系统结石进行成像,评价两种检查方法的优劣,进一步提高影像的诊断准确性.方法 采用多层螺旋MSCT及高场MRI对泌尿系统疾病患者进行检查,应用工作站后处理方法进行图像处理,各由两位影像专家进行图像分析.结果 本研究共收集78例患者,78例结石患者均经MSCT检查,其中60例经MR检查.MSCT平扫对结石显示的敏感度为100%,特异度为100%,MRU对结石显示的敏感度为96%,特异度为90%.MSCT 2.5 mm层厚重建图像显示小结石总数与5 mm层厚扫描图像相比,有明显统计学差异(P=0.000),MR对小结石均未能良好显示.MSCT、MRU两者总体图像质量无显著差异(P=0.53).厚层MRU图像质量优于多层薄层MIP重建MRU重建图像(P=0.041).结论 MSCT平扫薄层重建对于显示小结石具有明显的优势.MRU无电离辐射,适用于婴幼儿或孕妇患者.MSCT、MRU扫描范围大,均适用于多病灶患者的检查,结合原始图像,可以全面评价患者泌尿道疾病.     

泌尿系统结石MSCT、MRU成像的对比分析

目的 本研究应用MSCT、MRU对泌尿系统结石进行成像,评价两种检查方法的优劣,进一步提高影像的诊断准确性.方法 采用多层螺旋MSCT及高场MRI对泌尿系统疾病患者进行检查,应用工作站后处理方法进行图像处理,各由两位影像专家进行图像分析.结果 本研究共收集78例患者,78例结石患者均经MSCT检查,其中60例经MR检查.MSCT平扫对结石显示的敏感度为100%,特异度为100%,MRU对结石显示的敏感度为96%,特异度为90%.MSCT 2.5 mm层厚重建图像显示小结石总数与5 mm层厚扫描图像相比,有明显统计学差异(P=0.000),MR对小结石均未能良好显示.MSCT、MRU两者总体图像质量无显著差异(P=0.53).厚层MRU图像质量优于多层薄层MIP重建MRU重建图像(P=0.041).结论 MSCT平扫薄层重建对于显示小结石具有明显的优势.MRU无电离辐射,适用于婴幼儿或孕妇患者.MSCT、MRU扫描范围大,均适用于多病灶患者的检查,结合原始图像,可以全面评价患者泌尿道疾病.     

泌尿系统结石MSCT,MRU成像的对比分析

目的本研究应用MSCT、MRU对泌尿系统结石进行成像，评价两种检查方法的优劣，进一步提高影像的诊断准确性。方法采用多层螺旋MSCT及高场MRI对泌尿系统疾病患者进行检查，应用工作站后处理方法进行图像处理，各由两位影像专家进行图像分析。结果本研究共收集78例患者，78例结石患者均经MSCT检查，其中60例经MR检查。MSCT平扫对结石显示的敏感度为100％，特异度为100％，MRU对结石显示的敏感度为96％，特异度为90％。MSCT2．5mm层厚重建图像显示小结石总数与5mm层厚扫描图像相比，有明显统计学差异（P=0．000），MR对小结石均未能良好显示。MSCT、MRU两者总体图像质量无显著差异（P=0．53）。厚层MRU图像质量优于多层薄层MIP重建MRU重建图像（P=0．041）。结论MSCT平扫薄层重建对于显示小结石具有明显的优势。MRU无电离辐射，适用于婴幼儿或孕妇患者。MSCT、MRU扫描范围大，均适用于多病灶患者的检查，结合原始图像，可以全面评价患者泌尿道疾病。     

Magnetic resonance imaging of coronary artery occlusions in the navigator technique

Non-invasive assessment of coronary arteries is possible with magnetic resonance imaging (MRI). Respiratory gated MR coronary angiography is a new imaging technique that permits reconstruction of the coronary arteries based on a three-dimensional (3D) data set obtained from the free-breathing patient. In this study, respiratory gated MR angiography (MRA) was performed to assess coronary artery occlusions. MRI was performed in 25 patients who had been referred for conventional coronary angiography because of suspected coronary artery disease. Coronary artery occlusion was evaluated in the proximal and middle vessel segments after multiplanar coronary reconstruction of the MR images. Five patients were excluded from the study; in the remaining 20 patients 120 coronary artery segments were analyzed. Good image quality could be obtained for 85% of the segments. Eighteen of the 24 occlusions were confirmed by MRI, the overall sensitivity was 75% and the specificity was 100%. The best results were found in the proximal left anterior descending (LAD) and descending parts of the right coronary artery (RCA), where all occlusions were confirmed. These results showed that coronary artery occlusions can be detected in the proximal and middle LAD and RCA using 3D respiratory gated MRA. Further technical improvements, especially in spatial resolution, are necessary before MRA can become a reliable diagnostic tool in the non-invasive evaluation of coronary arteries.     

心血管磁共振成像临床应用和新进展

近年来由于MRI的进展,现已成为医学成像技术的主要组成部分,心血管MRI已广泛、有效地应用于心脏、大血管、内脏和外周血管成像及诊治工作.本文简要叙述心血管MRI临床应用概况,如对胸主动脉疾患、缺血性心脏病、心肌病、心脏肿瘤、先心病、心包疾患和心脏瓣膜病的诊断评价等.重点讨论一些新进展,如MR心肌灌注成像和心肌存活的评价;MR冠脉造影和斑块成像;深静脉血栓和肺栓塞的MR诊断以及MR血管造影对腹主-髂股-下肢动脉狭窄性病变的诊断及效果分析.     

Imaging of the renal transplant: comparison of MRI with duplex sonography

Renal transplantation is an established treatment for patients with end-stage renal disease. Many causes of graft dysfunction are treatable, making prompt detection and diagnosis of complications essential. Sensitive, noninvasive imaging procedures, which do not use iodinated contrast media, are therefore highly desirable to evaluate graft function. Duplex sonography (US) has traditionally been the initial investigation of graft dysfunction. US offers many advantages, particularly during the postoperative period, when it can be performed portably regardless of renal function and can guide percutaneous procedures. However, US lacks specificity in assessing hydronephrosis, cannot differentiate parenchymal causes of dysfunction, and may have difficulty assessing transplant vessels. Recently comprehensive magnetic resonance imaging (MRI) protocols including MR urography, gadolinium-enhanced MR angiography, and MR renography have evolved as a “one-stop” diagnostic technique in the evaluation of the entire graft and peritransplant region. Multiplanar capabilities enable MRI to identify the site of urinary obstruction and assess renal vessels in their entirety. The evolving technique of MR renography may also differentiate parenchymal causes of dysfunction. By combining these three components into a single examination, further information may be obtained regarding the graft when compared with US and other conventional studies, with improved patient convenience, less morbidity, and a potential cost saving.     

磁标记大鼠肾脏骨髓间充质干细胞移植MR成像研究

目的对移植入大鼠正常肾脏的Fe2O3-PLL标记MSCs进行MR成像并探讨其成像技术。方法分离培养大鼠骨髓MSCs,Fe2O3-PLL标记细胞。将标记和未标记细胞经左肾动脉移植入大鼠肾脏,移植后即刻,第1、3、5、8天应用MRI对移植细胞进行活体示踪并与肾脏组织切片对照。结果MSCs的Fe2O3-PLL标记率近100%。标记细胞移植后T2WI肾脏皮质区信号强度明显下降,持续至移植后第8天。组织学分析见绝大多数标记细胞分布于肾小球内。结论1.5T磁共振仪可对移植入正常肾脏的Fe2O3-PLL标记细胞进行活体成像,T2WI信号变化最明显。     

Ischemic heart disease: value of MR techniques

Background. The cardiovascular applications of magnetic resonance (MR) techniques in coronary artery disease have increased considerably in recent years. Technical advantages of MR imaging are the excellent spatial resolution, the characterization of myocardial tissue, and the potential for three-dimensional imaging. These characteristics allow the accurate assessment of left ventricular mass and volume, the differentiation of infarcted from normal tissue, and the determination of systolic wall thickening and regional wall motion abnormalities. Methods. In addition to the conventionally used spin-echo and cine-echo techniques, newer techniques such as myocardial tagging, ultrafast MR imaging and MR coronary angiography have been developed. These newer techniques allow a more accurate assessment of ventricular function (tagging), myocardial perfusion (ultrafast imaging), and evaluation of stenosis severity (MR coronary angiography). Particularly early detection and flow assessment of stenosed coronary arteries and bypasses by MR angiography would constitute a major breakthrough in cardiovascular MR imaging. Apart from the MR imaging techniques, cardiac metabolism may be well assessed using MR spectroscopy. This provides unique information on the metabolic behaviour of the myocardium under conditions stress-induced ischemia. However, the definite niche of cardiac MR spectroscopy has still to be settled. Conclusion. Currently, MR techniques allow the evaluation of anatomy and function (accepted use), perfusion and viability (development phase), and coronary angiography (experimental phase). A particular strength of MR imaging is that one single MR test may encompass cardiac anatomy, perfusion, function, metabolism and coronary angiography. The replacement of multiple diagnostic tests with one MR test may have major effects on cardiovascular healthcare economics and would outweigh the cost inherent to the MR angiography procedure.