دانلود کتاب MRI بالینی پیشرفته کلیه

Quantitative MRI techniques reveal promising markers for renal disease and could provide additional insights into kidney pathology characterization and disease progression in patients. The interest in renal MRI-derived biomarkers is driven by the potential to quantify morphological, microstructural, hemo­dynamic, and metabolic changes noninvasively and across the entire kidney parenchyma. Radiologists generally evaluate signal using intensity descrip­tors such as “hyperintense” or “hypointense” and use the expected signal appearance of various tissues and associated pathologies to render a differen­tial diagnosis. However, this subjective analysis of relatively “weighted” images is only a fraction of the tissue property information that could be provided by MRI techniques. The very concept of “weighting” can start to break down when more than one tissue is being compared. In addition, limita­tions of current MRI technologies include variable image acquisition across scanners, limited reproducibility of images, and known inter-reader variabil­ity in image interpretation. Quantitative MRI provides a unique and discrete analysis of tissue parameters and holds promise in addressing some of these limitations. To date, the most common quantitative MRI properties used in clinical practice are diffusion-weighted imaging, fat fraction (FF) mapping, and perfusion mapping. Quantification and mapping of T1 and T2 relaxation times, which affect all MR signals, are not commonly performed given the additional significant scan time that would be required. In the past decade, it has become increasingly apparent that the biophysical quantities measurable by MRI can have a utility beyond generating image contrast. In particular, these biophysical quantities such as T1, T2, and T2* are sensitive to tissue type and should enable them to characterize changes “within” tissues caused by aging, disease, or intervention. This is a compelling hypothesis in the con­text of renal medicine because a range of MRI techniques is sensitive to the pathophysiological changes associated with the progression of renal disease. In that sense, MRI may open up a novel source of noninvasive biomarkers to inform about pathogenesis, improve predictions of disease progression, and evaluate treatment effects. These quantitative MR techniques could aid in a deeper understanding of the function and composition of a patient’s renal tis­sue, which could provide a more accurate and earlier assessment of renal disease and facilitate earlier interventions to halt or slow down renal disease progression.

Despite considerable research effort and unique quantitative information available on clinical MRI scanners, integration of quantitative MRI methods into clinical practice has been limited. There are multiple reasons for this, including the fact that acquisition parameters and data analysis protocols have not yet been standardized. Other factors are limited vendor support, dif­ficulties in interpretation, limited perceived “added-value” above conven­tional MRI, and lack of additional reimbursement. This book is intended to address some of these issues. It gives the reader a solid basis for understand­ing both the techniques and the applications of quantitative MRI biomarkers in kidney imaging.

We have now entered an era in which it is possible to obtain rapid quantita­tive measurements of numerous physiologically relevant tissue properties—diffusion, perfusion, fat content, iron content, blood oxygen level, tissue elasticity, T1, T2, etc. Each property has found scientific and clinical utility in various applications. With the advancement of the computing power of mod­ern MRI scanners, the images can be post-processed and quantitative maps be generated on the scanner console, ready for review as soon as the acquisition is complete. Such quantitative MRI methods in kidney imaging are vital because they are relatively unbiased as compared with qualitative descriptions.