MR imaging and MR spectroscopic imaging of prostate cancer

The primary indication for prostate MR and MR spectroscopic imaging is evaluating men with newly diagnosed prostate cancer who are deciding whether to undergo surgery or radiotherapy. Other applications of MR and MR spectroscopic imaging in prostate cancer are not defined fully. Areas of research include volumetric localization of prostate cancer, in vivo MR spectroscopic imaging at high field strength, in vitro MR spectroscopic imaging at very high field strength, novel spectroscopic markers of malignancy,and interventional MR guidance of biopsy and therapy. MR spectroscopic imaging remains a relatively novel technique, and successful implementation is demanding. Nonetheless, only MR and MR spectroscopic imaging allow structural and metabolic evaluation of prostate cancer location, aggressiveness, and stage, and MR imaging provides clinically and therapeutically relevant information on prostatic and periprostatic anatomy.     

心包横窦MRI所见与断面解剖对照研究

目的：探讨正常心包横窦的ＭＲＩ表现。材料与方法：选用正常成人胸部连续断层切片解剖标本４例。收集无心包病变患者ＭＲＩ例,结合解剖所见,分析ＭＲＩ上横窦的形态,大小和毗邻关系,横窦分为前垂直部、中间水平部及后垂直部。     

MR imaging of the bladder

MR imaging is a useful modality for evaluating diseases of the bladder. MR imaging can detect and stage bladder cancer by determining the presence and depth of muscle invasion.Direct multiplanar imaging and superb soft-tissue contrast make MR imaging an ideal modality for evaluating less common neoplastic diseases of the bladder, such as urachal carcinoma, and tumors that develop within bladder diverticula. Dynamic breath-held fast T2-weighted imaging can evaluate for cystocele and other components of pelvic floor relaxation.     

MR imaging of the gallbladder

T2-weighted imaging and MRCP, which have high sensitivity to edema and fluid, are paramount in the evaluation of certain gallbladder diseases, such as cholelithiasis, cholecystitis, adenomyomatosis, and cystic duct abnormalities. Dynamic gadolinium-enhanced MR imaging has the potential to differentiate among the many nonspecific-appearing lesions involving the gallbladder. MR imaging may not yet replace ultrasound as the workhorse of acute gallbladder imaging. Currently, MRCP is an ideal complementary study to inconclusive sonographic studies and can help plan surgical intervention in the setting of acute cholecystitis. Further investigation of hepatobiliary contrast agents, however, may reveal that MR imaging may be considered as first-line imaging in the acute setting.     

MR imaging of the breast

The results of clinical investigation suggest that MR imaging can provide clinically important information that cannot be obtained with conventional imaging methods, and that this modality will, in the future, be an invaluable adjunctive breast imaging tool, just as breast imaging is today. MR imaging as a method to detect, diagnose, and stage breast cancer remains in the investigational stage, but is emerging as perhaps the most promising imaging modality for breast cancer detection.     

MR imaging of the pancreas

MR imaging is a valuable tool in the assessment of the full spectrum of pancreatic diseases. MR imaging techniques are sensitive for the evaluation of pancreatic disorders in the following settings: (1) TI-weighted fat-suppressed and dynamic gadolinium-enhanced SGE imaging for the detection of chronic pancreatitis, ductal adeno-carcinoma, and islet-cell tumors; (2) T2-weighted fat-suppressed imaging and T2-weighted breath-hold imaging for the detection of islet-cell tumors;and (3) precontrast breath-hold SGE imaging for the detection of acute pancreatitis. Relatively specific morphologic and signal intensity features permit characterization of acute pancreatitis,chronic pancreatitis, ductal adenocarcinoma, insulinoma, gastrinoma, glucagonoma, microcystic cystadenoma, macrocystic cystadenoma, and solid and papillary epithelial neoplasm. MR imaging is effective as a problem-solving modality because it distinguishes chronic pancreatitis from normal pancreas and chronic pancreatitis with focal enlargement from pancreatic cancer in the majority of cases.MR imaging studies should be considered in the following settings: (1) in patients with elevated serum creatinine, allergy to iodine contrast, or other contraindications for iodine contrast administration; (2) in patients with prior CT imaging who have focal enlargement of the pancreas with no definable mass; (3) in patients in whom clinical history is worrisome for malignancy and in whom findings on CT imaging are equivocal or difficult to interpret; and (4) in situations requiring distinction between chronic pancreatitis with focal enlargement and pancreatic cancer. Patients with biochemical evidence of islet-cell tumors should be examined by MR imaging as the first-line imaging modality because of the high sensitivity of MR imaging for detecting the presence of islet-cell tumors and determining the presence of metastatic disease.     

Basic concepts of MR imaging, diffusion MR imaging, and diffusion tensor imaging

MR image contrast is based on intrinsic tissue properties and specific pulse sequences and parameter adjustments. A growing number of MRI imaging applications are based on diffusion properties of water. To better understand MRI diffusion-weighted imaging, a brief overview of MR physics is presented in this article followed by physics of the evolving techniques of diffusion MR imaging and diffusion tensor imaging.     

Neonatal MR imaging

Recently, MR imaging has become the technique of choice in evaluating neonatal central nervous system diseases. It is the only imaging technique that can discriminate myelinated from neonatal unmyelinated white matter; it offers the highest sensitivity in detecting acute anoxic injury of the neonatal brain; and with proper coils and sequences, it can exquisitely depict neonatal brain anatomy and locate pathology, offering a robust and reliable tool in the prognostic assessment of neonatal central nervous system disease.     

Fetal MR imaging

Ultrasonography is the primary prenatal screening modality used in the evaluation of the fetus and the maternal pelvis. However, fetal MR imaging plays a complementary role to prenatal ultrasound in the evaluation of the fetus with suspected abnormalities. MR imaging's role includes confirming or excluding possible lesions, defining their full extent, aiding in their characterization, and demonstrating other associated abnormalities. As newer techniques such as diffusion imaging, MR spectroscopy, and functional studies are used more widely, it is hoped that additional information will be made available by this modality to physicians evaluating and taking care of fetuses.     

Functional MR imaging

Functional MR (fMR) imaging offers unprecedented spatial and temporal resolution of brain cognition. The impact of this technology on neuroscience research is just now being explored. This article discusses blood oxygenation level-dependent-based fMR imaging. Topics include the origin of the MR-based signal, data acquisition and sequence dependence, and paradigm design issues--issues that need to be fully understood to properly design and interpret the fMR imaging experiment.     

Intrabiliary MR imaging

The goal of this research is to illustrate the potential role of interventional MR imaging ina clinical setting. As shown by this study, IBMR is feasible, is well tolerated, and positively affects patient management. IBMR allowed for significantly decreased field of view and high in-plane resolution and provided contrast between the biliary lumen and adjacent structures with high diagnostic accuracy. This technique enabled clinicians not only to improve imaging of the biliary tree but also to make a more accurate diagnosis. Based on this pilot work, there are several potential avenues of further expansion for IBMR. For example, enhanced imaging of the biliary tree may allow for monitoring of new biliary treatment regimens such as photodynamic therapy or molecular targeting. In addition, this technique may also foster development of innovative new percutaneous procedures that may eventually treat some biliary disorders under MR imaging guidance.     

Intraoperative MR imaging

Intraoperative MR imaging has become a safe and effective technology that has revolutionized the way neurosurgery is performed. Benefits include the ability to update data sets for navigational systems, to monitor tumor resections, to adjust the approach to intracranial lesions, and to guide functional and drug or cell delivery procedures. Use of this technique can help avoid inadvertent injury of important anatomic and vascular structures. In addition, complications such as ischemia or hemorrhage can be detected early. Intraoperative MR imaging is particularly useful for ensuring that brain biopsies yield diagnostic tissue and for assessing the completeness of tumor resection. As is true for any new technology, the benefits of intraoperative MR imaging must be examined carefully to guarantee appropriate use. Many neurosurgical procedures do not require real-time image guidance and can be performed safely using current surgical techniques, including microsurgical methods and frameless and frame-based stereotaxy. Other tumor resections, tumor biopsies, and surgical and interventional procedures distinctly benefit from the sophisticated information provided by intraoperative imaging techniques. In surgery for low-grade gliomas, intraoperative MR imaging has found general acceptance, whereas its usefulness to monitor the resection of high-grade gliomas remains controversial. The economic issues related to intraoperative MR imaging cannot be overlooked. The acquisition of an intraoperative MR imaging system is associated with considerable expense, and its performance increases the cost of equipment and the operating time. Despite these additional expenses, intraoperative MR imaging can lead to a potential overall cost reduction in the treatment of certain patients if long-term cure can be achieved, repeat resection can be avoided, or procedure-associated morbidity can be reduced. Although intraoperative MR imaging techniques hold tremendous potential, the definition of their appropriate role in the delivery of successful and cost-effective medical care awaits further study.     

MR imaging of the adrenal neoplasms

The most commonly encountered adrenal mass is the non-hyperfunctioning adrenal adenoma. Chemical-shift MR imaging can detect and characterize these adrenal masses as benign but cannot distinguish between hypersecreting and nonhypersecreting adrenal adenomas. Because of its direct multiplanar capability and superb soft tissue contrast, MR imaging can detect and potentially characterize other adrenal neoplasms.     

MR imaging of the thoracic inlet

The borders of the thoracic inlet define an oblique plane that angles downward from the spine anteriorly to the first ribs. It is therefore best to consider the thoracic inlet as a region or "zone" which extends a short distance above and below this plane to include the lower portion of the infrahyoid neck and the upper portion of the superior mediastinum. MRs multiplanar imaging capability allows the thoracic inlet to be subdivided into four distinct zones; visceral, neurovascular, pulmonary, and spinal. The first section of this article reviews the normal anatomy of each zone and the sequence protocol for imaging of the brachial plexus. The second section discusses differential diagnoses relevant to each zone. Pathologic processes are also presented.     

骨梗死的MRI诊断

目的：探讨骨梗死的MRI表现。方法：回顾分析5例经MRI诊断的骨梗死,均由临床和手术证实。其中3例行X线检查未见明显异常后行MRI检查。结果：5例行MRI检查的骨梗死中共累及9个部位的骨骼,股骨下段5个,胫骨上段4个。MR上均呈“地图板块”样改变,T1WI上中心呈等骨髓信号,边缘呈花边样低信号,T2WI上中心呈等高混杂信号,边缘呈内高外低的2层信号者7个,呈花边样高信号者2个。结论：MRI是检查诊断骨梗死最佳方法,可以发现早期病变,明显优于X线检查。     

Functional MR imaging of the uterus

Recent developments in MR imaging techniques have enabled the functional assessment of the uterus. Cine MR imaging is a useful tool for evaluating uterine kinematic functions derived from myometrial contractility, and for investigating the alteration of uterine contractility in a variety of conditions and gynecologic disorders. Diffusion-weighted imaging can demonstrate abnormal signal in pathologic foci based on differences in molecular diffusion, and could provide useful information in evaluating malignant conditions. Dynamic contrast-enhanced MR imaging has the potential to improve tumor detection and local staging, and quantitative information may be useful for both monitoring therapeutic effects and predicting outcome. These state-of-the-art functional MR imaging techniques are beneficial for elucidating various uterine conditions when used appropriately, and the findings further provide the basis of future MR imaging investigations.     

High-resolution MR imaging of the breast

Investigation into the use of MRI as a breast imaging tool is ongoing. Several studies have shown that MRI is a very accurate imaging method for the identification of implant failure in the symptomatic patient with augmented breasts. In this clinical setting, MRI may be the study of choice. Imaging techniques, and the MRI appearance of normal and abnormal implants, are described. The use of MRI for the detection of breast cancer is not as straightforward. Preliminary results suggest that this technique can be used as an adjunct to mammography for the detection and diagnosis of breast cancer. However, it is premature to draw firm conclusions regarding the role that MRI should play in the management of women with breast disease because of the wide variability of imaging techniques, protocols, and patient populations in the studies reported to date. In this overview, the current state of MR imaging of the breast is discussed. Technical requirements are described, and potential clinical applications—including the differentiation of benign from malignant lesions, breast cancer staging, detection of recurrence after breast conservation therapy, and detection of cancer in patients presenting with positive axillary lymph nodes with an unknown primary—are reviewed. Many of these potential clinical applications will require an accurate MR-guided biopsy system, and the implementation of such a system as well as its inherent limitations are discussed.     

MR imaging of the adrenal glands

MR imaging is used commonly for imaging the adrenal glands. Its high-contrast resolution and multiplanar imaging capability enables the detection and characterization of many adrenal masses. The advent of chemical-shift imaging revolutionized the role of MR imaging in characterizing adrenal masses. In this article, the authors discuss the range of MR appearances of common and uncommon adrenal masses, focusing on the nonfunctioning incidentally discovered mass and its characterization methods. MR imaging is continuously improving. The increasing use of higher strength magnets and the introduction of newer coils, sequences, and techniques will help detect and characterize very small adrenal masses, quantify their fat content, and provide exquisite morphologic images of the gland and its vascular supply.