Advances in MR spectroscopy of the prostate

Commercial MR imaging/magnetic resonance spectroscopic imaging (MRSI) packages for staging prostate cancer on 1.5-T MR scanners are now available. The technology is becoming mature enough to begin assessing its clinical utility in selecting, planning, and following prostate cancer therapy. Before therapy, 1.5-T MR imaging/MRSI has the potential to improve the local evaluation of prostate cancer presence and volume and has a significant incremental benefit in the prediction of pathologic stage when added to clinical nomograms. After therapy, two metabolic biomarkers of effective and ineffective therapy have been identified and are being validated with 10-year outcomes. Accuracy can be improved by performing MR imaging/MRSI at higher magnetic field strengths, using more sensitive hyperpolarized (13)C MRSI techniques and through the addition of other functional MR techniques.     

直肠表面线圈MRI对前列腺癌的诊断价值

目的探讨直肠表面线圈MRI对前列腺癌的鉴别诊断及分期的价值.方法 20例临床疑诊为前列腺癌的患者,分别用直肠表面线圈及体线圈进行多个轴位的TSE T1、T2及脂肪抑制序列扫描,比较两种检查方法对前列腺癌诊断及分期价值.结果直肠表面线圈MRI对前列腺癌检查的准确性(85.0%)、敏感性(85.7%)、特异性(83.3%)、阳性预测值(92.3%)均高于体线圈MRI扫描检查.结论用直肠表面线圈MRI可获得高分辨率的前列腺图像,提高对前列腺癌早期诊断率;结合体线圈,可提高对前列腺癌分期的准确性.     

Prostate cancer detection: magnetic resonance (MR) spectroscopic imaging

Magnetic resonance spectroscopic imaging (MRSI) represents a noninvasive technique to extend the diagnostic evaluation of prostatic cancer, beyond the morphologic information provided by MR imaging throughout the detection of cellular metabolites (choline and citrate). MRSI combined with the anatomical information provided by MRI can improve the assessment cancer location and extent within the prostate, extracapsular spread and cancer aggressiveness; both before and after treatment. We review the performance of MRI with MRSI and the role in the detection, localization, staging and management of the patient pre- and posttherapy for prostate cancer.     

Diffusion and perfusion MR imaging of the prostate

Conventional anatomic MR imaging has evolved to a superior modality in the evaluation of prostate carcinoma and is now a widely established technique in the detection and staging of this disease, aiding in clinical decision making on treatment and therapy evaluation. Recent improvements in functional MR techniques, such as diffusion-weighted MR imaging and dynamic contrast-enhanced MR imaging, have greatly increased the impact of MR imaging in prostate cancer. The combination of T2-weighted imaging, diffusion-weighted MR imaging, and dynamic contrast-enhanced MR imaging may overcome the limitations of conventional T2-weighted MR imaging of the prostate and may be able accurately to detect, localize, stage, and grade prostate carcinoma and guide biopsies.     

MR imaging of the prostate and bladder

Magnetic resonance imaging has become an important imaging modality for the male pelvis. Its unparalleled ability to depict soft tissue structures and highlight pathology have made it the best method for determining the extent of many disease processes. This article reviews the use of MR to evaluate diseases of the prostate gland and bladder. In both, the major indication for imaging is the local staging of cancer, and MR is currently the best imaging modality. This article will discuss the critical clinical issues concerning prostate cancer and neoplasms of the bladder, and the contribution of MR imaging.     

MR imaging of prostate cancer

MR imaging technology is continually evolving and improving. Endorectal MR imaging provides excellent anatomic detail and is the most accurate imaging modality for staging prostate cancer with the ability to affect therapy and cure in many men. Failure to detect microscopic disease and microscopic capsular invasion remain significant weaknesses. MR spectroscopy has great potential for improving the sensitivity and specificity of MR imaging and expanding its diagnostic and staging usefulness.     

Abdominal MR imaging at 3T

Body MR imaging at 3T is in its infancy, and should improve substantially over the next several years. Radiologists need to be aware of several limitations that are based on the laws of physics: Overall, the gain in SNR at 3T will be less than twofold (without protocol alteration) compared with a standard 1.5T MR system because of the increase in T'I'1 at ultra high field. Typically, the gain in SNR is greater in T2-weighted sequences than in TI-weighted sequences, because longer TRs allow for a more complete recovery of the longitudinal magnetization, and T2 is independent of Bo. Thus, for example, patients who are referred for an MR cholangiography may benefit from an ultrahigh-field MR examination. Chemical shift artifacts of the first kind are twice as large in ultrahigh-field MR imaging compared with standard 1.5T MR imaging. Conversely, chemical shift artifacts of the second kind do not increase in size, although the timing is altered. The increased difference in resonant frequency between water and fat at 3T also is advantageous because it allows for a better separation of the fat and water peak during MR spectroscopy, and allows better or faster fat suppression using chemical shift techniques, such as fat saturation or water excitation. Susceptibility artifacts are approximately twice as large by volume on 3T MR imaging. Although patients who are referred for a "colon" study may be challenging at ultrahigh field, the search for "gas" (eg, free air or pneumobilia) should be easier. Patients with metal implants should undergo an MR examination at 3T only if the metal-containing device specifically has been proved to be MR safe at this field strength. Usually, standing wave and conductivity effects are not seen in body imaging at a field strength of 1.5T. At 3T, these artifacts are most pronounced in pregnant women in the sec-ond and third trimester, because of the large amount of conductive amniotic fluid and the increased size of the abdomen. Therefore, fetal MR imaging generally should not be performed at 3T because of these artifacts and the increased safety concerns. The same holds true for patients with a large amount of ascites, who also are not well suited for an ultrahigh-field MR examination. Except as noted above, most patients can undergo an abdominal MR imaging study at 3T with a reasonable outcome in terms of image quality.     

DWI在前列腺癌诊断中的应用进展

MRI在前列腺癌的早期诊断、临床分期及侵袭性评估中有重要作用,而DWI是应用最广泛的MRI功能成像序列之一。现将DWI在前列腺癌诊断中的临床应用进展进行综述。     

MR imaging of the prostate: 1.5T versus 3T

Over the past several years, evidence supporting the use of MR imaging in the evaluation of prostate cancer has grown. Almost all this work has been performed at 1.5T. The gradual introduction of 3T scanners into clinical practice provides a potential opportunity to improve the quality and usefulness of prostate imaging. Increased signal to noise allows for imaging at higher resolution, higher temporal resolution, or higher bandwidth. Although this may improve the quality of conventional T2-weighted prostate imaging, which has been the standard sequence for detecting and localizing prostate cancer for years, the real potential for improvement at 3T involves more advanced techniques, such as spectroscopy, diffusion-weighted imaging, dynamic contrast imaging, and susceptibility imaging. This review presents the current data on 3T MR imaging of the prostate as well as the authors' impressions based on their experience at Yale-New Haven Hospital.     

Advances in pediatric MR imaging

This article describes the considerable technical achievements that have been made in MR imaging in the evaluation of pediatric patients. The latest techniques in improving signal intensity, resolution, and speed are discussed. The multitude of new options for pediatric MR imaging are illustrated, including higher field strength imaging, multi-channel coil technology coupled with parallel imaging, and new pulse sequence designs. Several future directions in the field of pediatric body and musculoskeletal imaging also are highlighted.     

Perspectives on body MR imaging at ultrahigh field

As investigators consider approaching the challenge of MR imaging at field strengths above 3T, do they follow the same paradigm, and continue to work around the same problems they have encountered thus far at 3T, or do they explore other ways of answering the clinical questions more effectively and more comprehensively? The most immediate problems of imaging at ultrahigh field strength are not unfamiliar, as many of them are still pressing issues at 3T: radiofrequency coils, B1 homogeneity, specific absorption rate, safety, B0 field homogeneity, alterations in tissue contrast, and chemical shift. In this article, these issues are briefly reviewed in terms of how they may affect image quality at field strengths beyond 3T. The authors propose various approaches to overcoming the challenges, and discuss potential applications of ultrahigh field MR imaging as it applies to specific abdominal, pelvic, peripheral vascular, and breast imaging protocols.     

New horizons in genitourinary oncologic imaging

In the management of prostate cancer, combined anatomic and metabolic imaging is already in clinical use. In daily clinical practice, fusion of magnetic resonance imaging and magnetic resonance spectroscopic imaging is improving the evaluation of cancer location, size, and extent and is simultaneously providing assessment of tumor aggressiveness. Pretreatment knowledge of these prognostic variables is essential if minimally invasive, patient-specific cancer therapy is to be achieved. This report discusses the changes that are occurring in oncologic imaging and in genitourinary oncologic imaging in particular. It presents an overview of the applications of magnetic resonance imaging and magnetic resonance spectroscopic imaging for prostate cancer that is intended to illustrate the evolution of state-of-the-art imaging in a clinical setting. It also provides a short review of molecular imaging probes from the field of ongoing prostate cancer research. It concludes with a broader discussion of the nature of molecular imaging and the benefits it offers for cancer research and clinical care, which include noninvasive, in vivo imaging of specific cellular and molecular processes, nearly simultaneous monitoring of multiple molecular events, real-time imaging of the trafficking and targeting of cells, optimal patient-specific adjustment of drug and gene therapy, and assessment of disease progression at a molecular pathologic level.     

MR imaging and MR spectroscopy in prostate cancer

Prostate cancer is the most common cancer in western men. The morbidity in Japanese men is also increasing. This article reviews MR imaging and MR spectroscopy used for the diagnosis and management of prostatic cancer. Discussion emphasizes techniques for routine MR imaging, imaging findings, and the value of MR imaging in patients with prostatic cancer. The new and promising technique of MR spectroscopy and 3T MR imaging also will be introduce.     

MR扩散功能成像诊断前列腺癌研究进展

我国前列腺癌（PCa）发病率逐年上升,严重影响男性健康。MRI是诊断PCa的常用影像学方法。随着新技术的不断发展,MR扩散功能成像已在PCa诊断及分期方面取得了较大进展。本文就MR扩散功能成像诊断PCa的研究进展进行综述。     

Cancer staging with breast MR imaging

Breast MR imaging is a useful tool for staging breast cancer patients, and staging is more accurate with MR imaging than with conventional imaging techniques. MR imaging is the preferred imaging test for the accurate staging of breast cancer before surgery and for assessment of patients with positive axillary adenopathy and negative mammogram and physical examination. There are many important questions regarding the role of MR imaging in breast cancer staging that must be addressed by future research and involvement of MR imaging of the breast in clinical trials.     

超高场MRI：脑部成像结果探讨

随着射频和线圈技术的提高,超高场磁共振近年来有了很大的发展。与常规的场强,超高场MR主要具有以下优势：（1）信噪比的显著增加保证了高分辨率和高质量的图像,从而大大提高了微小结构的检出;（2）由于磁敏感效应的增加,T2＊或磁敏感技术有了更广泛的应用,尤其是对异常的铁沉积,微小出血点和小静脉血管的检测;（3）高场T1弛豫时间的增加可以提高ASL灌注成像技术的应用;（4）信号本身的增加也可提高fMRI和MRS的分辨率等。当然,目前超高场强磁共振技术也还有一些局限性：（1）SAR的明显增加限制了采集层数并影响采集时间;（2）高场下RF磁场（B1）的不均匀性造成图像信号的不均匀;（3）增加的磁敏感效应也在颅底增加了相应的伪影等。本文对高场7T在纽约大学医疗中心脑部MR的最初临床应用结果 进行了分析。     

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.     

Synthesis and in vitro evaluation of MR molecular imaging probes using J591 mAb‐conjugated SPIONs for specific detection of prostate cancer

Carcinoma of the prostate is the most frequent diagnosed malignant tumor in men and is the second leading cause of cancer‐related death in this group. The cure rate of prostate cancer is highly dependent on the stage of disease at the diagnosis and early detection is key to designing effective treatment strategies. The objective of the present study is to make a specific MR imaging probe for targeted imaging of cancer cells. We take advantage of the fact that many types of prostate cancer cells express high levels of prostate‐specific membrane antigen (PSMA) on their cell surface. The imaging strategy is to use superparamagnetic iron oxide nanoparticles (SPIONs), attached to an antibody (J591) that binds to the extracellular domain of PSMA, to specifically enhance the contrast of PSMA‐expressing prostate cancer cells. Conjugation of mAb J591 to commercial SPIONs was achieved using a heterobifunctional linker, sulfo‐SMCC. Two types of prostate cancer cell lines were chosen for experiments: LNCaP (PSMA+) and DU145 (PSMA?). MRI and cell uptake experiments demonstrated the high potential of the synthesized nanoprobe as a specific MRI contrast agent for detection of PSMA‐expressing prostate cancer cells. Copyright © 2012 John Wiley & Sons, Ltd.     

MR imaging of lung cancer

Computed tomography of the chest is the present mainstay of cross-sectional imaging in patients with lung cancer. MR imaging, however, plays a complementary role in evaluating apical tumor and is often used as a problem-solving tool when CT findings are equivocal. New developments such as contrast-enhanced MR imaging and whole-body MR imaging may broaden the indications for this technique in the future.     

Intraoperative MR imaging

With the rapid evolution of technologic advances in neurosurgery, it is no surprise that the use of MR imaging to guide the performance of safe and effective surgical procedures is at the forefront of development. This article highlights the current capabilities of intraoperative MR-guided surgery for a variety of neurosurgical procedures and traces the evolution of the field to its present level of technical sophistication. The costs of intraoperative MR imaging and its future directions are discussed.