Prognostic value of magnetic resonance imaging in the management of fistula-in-ano

PURPOSE: Magnetic resonance imaging of fistula-in-ano has been shown to predict surgical anatomy accurately and identify complex features. In addition, fistula complexity has been correlated with poor outcome after surgical intervention. We investigated whether preoperative magnetic resonance imaging could predict clinical outcome after surgery for fistulous disease better than clinical examination under anesthetic. METHODS: Seventy patients with clinically suspected fistula-in-ano underwent preoperative dynamic contrast-enhanced magnetic resonance imaging before surgical exploration. Outcome was assessed at a minimum of one year after surgical exploration and correlated in a blinded fashion with the surgical and magnetic resonance grading of the severity of the fistulous disease. RESULTS: Of 70 patients, 12 were not operated on and 6 were lost to follow-up, making 52 patients eligible for analysis. Assessment by dynamic contrast-enhanced magnetic resonance imaging more accurately predicted outcome than the findings at initial surgical exploration. Dynamic contrast-enhanced magnetic resonance imaging had a sensitivity of 81 percent, specificity of 73 percent, and positive predictive value of 75 percent; surgery had a sensitivity of 77 percent, specificity of 46 percent, and positive predictive value of 59 percent. Surgical assessment of apparent disease severity bore no relation to final outcome. Dynamic contrast-enhanced magnetic resonance imaging could accurately predict whether patients were likely to have a satisfactory or unsatisfactory outcome after surgery. CONCLUSION: Dynamic contrast-enhanced magnetic resonance imaging better predicts clinical outcome of patients with fistula-in-ano than initial surgical exploration.Study performed at St. James's University Hospital, Leeds, United Kingdom.     

心脏磁共振对肥厚型心肌病应用价值的研究

肥厚型心肌病(HCM)是最常见的遗传性心肌病,在普通人群中其发病率为1/500,HCM临床表现多样,主要发病机制是心肌细胞肥厚、排列紊乱、心肌纤维化及胶原沉积以及不稳定的心电活动容易导致恶性心律失常所致。近年来心脏磁共振(CMR)被广泛应用于HCM的诊断以及与其他疾病的鉴别诊断,CMR不仅能够准确评估心室功能、心室壁厚度,并且钆延迟强化(LGE)能够无创检测心肌纤维化及瘢痕。重要的是越来越多的研究证明LGE与HCM等多种心血管病的发生相关,并可以预测其发生。本文将回顾相关文献,总结CMR对HCM的应用价值,使CMR更好的应用于临床。     

Three-dimensional cardiac magnetic resonance imaging

Evaluation of time-varying cardiac structure and function is challenging because of the three-dimensional (3-D) anatomy and time-varying (4-D) behavior of the heart. Historically, contrast angiography has served as the cornerstone of cardiac diagnosis because of its excellent spatial and temporal resolution. However, magnetic resonance (MR) imaging is now increasingly applied because of the wide variety of available MR imaging and data acquisition techniques, including spin-echo, gradient-echo, wall motion techniques, 1H 31P spectroscopy, and, most recently, echo-planar imaging. Planar 2-D MR imaging is used to characterize many aspects of cardiac structure and function, including anatomic relationships, valvular heart disease, ischemic heart disease, and congenital abnormalities, among others. The development of imaging display and data postprocessing analysis techniques have paralleled the growth of these image and data acquisition schemes and, increasingly, an emphasis has been placed on defining structure and function in 3-D, or even 4-D. Three-dimensional reconstructions of the heart have commonly relied on conventional planar MR image acquisition techniques; a 3-D volume of data is then created from stacked 2-D images. Surface reconstruction and graphical rendering techniques are used to generate representations of the heart that depict 3-D and 4-D cardiac structure and function. These techniques have been used both clinically and experimentally in a variety of settings, including ischemic heart disease, MR coronary angiography, and congenital heart disease.     

Future prospects in cardiac magnetic resonance imaging

To appreciate the impact that key developments will have on the future of cardiovascular magnetic resonance (CMR) imaging, it is instructive to consider its present status. CMR has passed the threshold of being used primarily by innovators, and is now in the early adopter stage. To reach this threshold has taken many years, but its adoption by early majority users is expected to accelerate the growth of CMR. A number of factors govern its natural growth potential, including physician education and credentialing, scanner availability, technology, and reimbursement policies. The intrinsic dimensional accuracy of CMR, coupled with its high level of reproducibility, make it ideal for inclusion in trials, potentially with dramatic reductions in trial duration and the number of subjects required. Clinically, there are a number of applications for which CMR is widely regarded as being the diagnostic test of choice. Software and hardware developments that speed up the basic CMR procedure are being incorporated into scanners, extending the functionality of routine applications such as flow imaging and tag visualization. Exciting areas that are close to routine application include coronary artery imaging, and evaluation of myocardial perfusion and viability status.     

Molecular imaging of vulnerable plaque by cardiac magnetic resonance imaging

Coronary atherosclerosis is known to be the major cause for morbidity and mortality in the industrial world. In Europe, every year approximately 600,000 persons die from coronary artery disease, a majority of them without any prior symptoms. Plaque rupture, mostly of noncalcified vulnerable plaques, is supposed to play a major role in this setting, and noninvasive techniques are mandatory to stratify the individual risk for experiencing an acute coronary event. During the last decade, magnetic resonance imaging has gained importance as a noninvasive imaging technique in cardiology. Continuous technical improvements enabled a rapidly expanding field of application, and recently noninvasive imaging of plaques has been introduced. In addition to morphological characterization, functional imaging of plaques has gained interest for a more specific risk assessment. This article summarizes pathophysiological aspects of the concept of vulnerable plaque, technical requirements for noninvasive plaque imaging, and characterization with magnetic resonance imaging.     

Clinical applications of feature-tracking cardiac magnetic resonance imaging

Cardiovascular diseases represent the leading cause of mortality and morbidity in the western world. Assessment of cardiac function is pivotal for early diagnosis of primitive myocardial disorders, identification of cardiac involvement in systemic diseases, detection of drug-related cardiac toxicity as well as risk stratification and monitor of treatment effects in patients with heart failure of various etiology. Determination of ejection fraction with different imaging modalities currently represents the gold standard for evaluation of cardiac function. However, in the last few years, cardiovascular magnetic resonance feature tracking techniques has emerged as a more accurate tool for quantitative evaluation of cardiovascular function with several parameters including strain, strain-rate, torsion and mechanical dispersion. This imaging modality allows precise quantification of ventricular and atrial mechanics by directly evaluating myocardial fiber deformation. The purpose of this article is to review the basic principles, current clinical applications and future perspectives of cardiovascular magnetic resonance myocardial feature tracking, highlighting its prognostic implications.     

The future of real-time cardiac magnetic resonance imaging

Dynamic changes in cardiac structure and function are usually examined by real-time imaging techniques such as angiography or echocardiography. MRI has many advantages compared with these established cardiac imaging modalities. However, system hardware and software limitations have limited cardiac MRI to gated acquisitions that are lengthy and often result in failed acquisitions and examinations. Recently, MRI has evolved into a technique capable of imaging dynamic processes in real time. Improvements in hardware, pulse sequences, and image reconstruction algorithms have enabled real-time cardiac MRI with high spatial resolution, high temporal resolution, and various types of image contrast without requiring cardiac gating or breath-holding. This article provides an overview of current capability and highlights key technical and clinical advances. The future prospects of real-time cardiac MRI will depend on 1) the development of techniques that further improve signal to noise ratio, contrast, spatial resolution, and temporal resolution, without introducing artifacts; 2) the development of software infrastructure that facilitates rapid interactive examination; and 3) the development and validation of several new clinical assessments.     

Three-dimensional magnetic resonance imaging of congenital cardiac anomalies

We describe a new method of three-dimensional magnetic resonance imaging of the heart that has been used to produce high quality diagnostic images in 274 patients with congenital cardiac disease, ranging in age from 1 day to 66 years. Using a steady state free precession gradient echo technique and parallel imaging, rapid acquisition of the entire cardiac volume is possible during 8 to 15 sequential breath-holds, each lasting between 8 and 15 s. We obtained high-resolution images, with a resolution of 1 mm3, at between 3 and 10 phases of the cardiac cycle. While images of diagnostic quality were obtained in all cases, in 52 patients there was some degradation due to various factors. Children under 8 years were ventilated, and ventilation was suspended for the breath-holds. For patients breathing spontaneously a novel respiratory navigator technique was developed, using a navigator echo placed over the right hemidiaphragm. This was used successfully in 20 patients, and reduced the misalignment of images obtained during different breath-holds. Images were analysed using multi-planar reformatting and volume rendering. Image processing took approximately five minutes for each study. End-diastolic images were processed for all patients. Systolic images were also processed in selected cases. Further improvements in parallel imaging should reduce imaging times further, so that it is possible to obtain the full volume image in a single breath-hold. This will enable imaging of complex anatomy to be obtained using a standard imaging protocol that does not require the operator to understand the cardiac malformation, making the magnetic resonance imaging of congenital cardiac disease faster and more effective.