Craniocervical artery dissection: MR imaging and MR angiographic findings

Dissection of the carotid and vertebral arteries is a not so uncommon cause of stroke and has to be considered as a differential diagnosis especially in younger patients. Therapeutic and prognostic implications are different from those in extracranial atherosclerotic disease. Dissection results from hemorrhage into the vessel wall usually between the layers of the media. Digital subtraction angiography (DSA) depicts the resulting luminal compromise that may reveal some typical, but not specific, findings. The same is true for non-invasive angiographic techniques such as time-of-flight magnetic resonance angiography (MRA) and computed tomography angiography (CTA), which have shown accurate results compared with DSA. The main advantage of these techniques is the direct visualization of the vessel wall confirming the intramural hematoma. This is achieved best with MR imaging due to the high signal of blood degradation products on T1- and T2-weighted images. Therefore, MRI in combination with MRA is presently the method of choice for initial diagnosis and follow-up of craniocervical artery dissection (CCAD). In some questionable cases, CTA is a non-invasive alternative that is independent of flow phenomena. Received: 4 May 1998; Revision received: 8 September 1998; Accepted: 10 November 1998     

MR microscopy of hyaline cartilage: current status

Cartilage degenerative diseases, such as osteoarthritis, affect million of people. Magnetic resonance imaging is presently the most accurate imaging modality in evaluating the state of hyaline cartilage; however, clinical MRI does not accurately reveal early degenerative alterations in cartilage, due mainly to low spatial resolution. Magnetic resonance microscopy (MRM, or microMRI) appears exceptionally well suited to the in vitro or ex vivo study of this heterogeneous tissue, due to its high spatial resolution; however, despite this, further studies are necessary to evaluate the potential of MRM in the detection of early cartilage damage. Herein we briefly review the current applications of MRM in the study of hyaline cartilage. In particular, we review the MR appearance of hyaline cartilage on high-resolution images, the different MRM techniques used to image normal and enzymatically or chemically degraded cartilage and the potential use of contrast agents. The future directions and the relevance of MRM findings for a better understanding of cartilage physiology in health and disease are also discussed.     

Cranial fasciitis in an adult: CT and MR imaging findings

Cranial fasciitis is a rare bone lesion in childhood. We report the first case in an adult, with CT and MR imaging, and suggest some diagnostic keys. Received: 5 August 1998; Revision received: 6 November 1998; Accepted: 25 November 1998     

MR imaging of non-squamous vaginal tumors

We reviewed the MR images and pathologic findings of five cases of primary vaginal neoplasms of non-squamous origin. Histologic types consisted one case each of adenocarcinoma, adenosarcoma, melanoma, lymphoma, and neurilemoma. Magnetic resonance imaging was found useful for evaluating the type and the extension of vaginal tumors. Received: 8 April 1998; Revision received: 6 November 1998; Accepted: 27 January 1999     

Current Status of Optical Imaging for Evaluating Lymph Nodes and Lymphatic System

Optical imaging techniques use visual and near infrared rays. Despite their considerably poor penetration depth, they are widely used due to their safe and intuitive properties and potential for intraoperative usage. Optical imaging techniques have been actively investigated for clinical imaging of lymph nodes and lymphatic system. This article summarizes a variety of optical tracers and techniques used for lymph node and lymphatic imaging, and reviews their clinical applications. Emerging new optical imaging techniques and their potential are also described.     

MR urography: examination techniques and clinical applications

Modern MR urography is performed on the basis of two different imaging strategies, which can be used complementarily to cover almost all aspects in the diagnosis of upper urinary tract diseases. The first technique utilizes unenhanced, heavily T2-weighted pulse sequences to obtain static-fluid images of the urinary tract. T2-weighted MR urograms have proved to be excellent in the visualization of the markedly dilated urinary tract, even if the renal excretory function is quiescent. Static-fluid MR urography is less suitable for imaging of disorders that occur in the nondilated collecting system. The second MR urography technique is analogous to the methodology of conventional intravenous pyelography and is, therefore, designated as excretory MR urography. For this purpose, a non-nephrotoxic gadolinium chelate is intravenously administered and after its renal excretion, the gadolinium-enhanced urine is visualized using fast T1-weighted gradient-echo sequences. The combination of gadolinium and low-dose furosemide (5–10 mg) is the key for achieving a uniform distribution of the contrast material inside the entire urinary tract and, secondly, to avoid high endoluminal gadolinium concentrations, which cause signal loss of the urine due to T2^* effects. Gadolinium excretory MR urography allows to obtain high-quality images of both nondilated and obstructed urinary tracts in patients with normal or moderately impaired renal function. This article reviews the principles of T2- and T1-weighted MR urography in detail and informs how to use these techniques safely in potential clinical applications such as chronic urolithiasis, intrinsic and extrinsic tumor diseases, and congenital anomalies. Magnetic resonance urography performed in combination with standard MR imaging offers a potential to reduce the need for invasive retrograde pyelography. Although the economic aspect is still problematic, it is obvious that MR urography will continue to increase its role in clinical uroradiology. Received: 7 July 2000 Revised: 21 August 2000 Accepted: 21 August 2000     

Evaluation of sleep apnea syndrome with low-field magnetic resonance fluoroscopy

The aim of this study was to assess the upper airway status of sleep apnea syndrome (SAS) patients with low-field MR fluoroscopy. Twenty patients with clinically diagnosed SAS underwent upper airway monitoring using MR fluoroscopy for 5 min while awake and for 30 min while asleep. A 0.064-T permanent-magnet MR imaging system was used for the study. No patients required any sedative drugs because of the very small gradient noise, except in one case. No occlusion was observed while patients were awake. Nine patients showed repeated occlusion at retropalatal (Rp) pharynx, whereas 11 demonstrated both simple Rp occlusion and combined retropalato–retroglossal (Rp + Rg) occlusions (complex occlusion). The mean frequency of occlusion in complex cases was significantly higher than that in simple Rp cases (p < 0.05). Low-field MR fluoroscopy was useful in determining the occlusion level while asleep in patients with SAS because of its quiet gantry and long-term monitoring capability. The MR fluoroscopy technique should prove to be a valuable clinical tool for the diagnosis and for determining the appropriate therapy in patients with SAS. Received: 5 June 1998; Revision received: 30 November 1998; Accepted: 1 December 1998     

Imaging findings in patients with myelofibrosis

The purpose of this review is to illustrate the wide range of radiological abnormalities in myelofibrosis. Myelofibrosis, also called myeloid metaplasia, is a myeloproliferative disorder of unknown etiology. The common imaging findings in patients with myelofibrosis are osteosclerosis, hepatosplenomegaly, and lymphadenopathies. In addition, extramedullary hematopoiesis may develop in multiple sites such as chest, abdomen, pelvis, and central nervous system, simulating malignant disease. Selected plain-film, CT, and MR images in patients with myelofibrosis are shown as pictorial essay to allow ready recognition of the most common imaging abnormalities of the disease. Received: 6 August 1998; Revision received: 15 October 1998; Accepted: 20 November 1998     

Symptomatic fibrous lunato-triquetral coalition

In general, carpal coalitions are considered to be asymptomatic. Incomplete separated joints and associated changes similar to osteoarthritis and pseudoarthrosis are known as possible causes of wrist pain. We present the clinical history, plain-film, and MR imaging findings of two patients with symptomatic fibrous lunato-triquetral coalition. Conventional films disclosed a narrowed space between the lunate and triquetral bone with cysts and sclerosis similar to pseudoarthrosis. Magnetic resonance imaging showed bone marrow edema adjacent to the incomplete separated lunato-triquetral joint and Gd-DTPA enhancing fibrovascular tissue in the synovium and subarticular cysts, explaining the pain over the ulnar-sided wrist. Patients with congenital lunato-triquetral coalition may poorly tolerate stress loading or trauma, resulting in a symptomatic state similar to degenerative arthritis or pseudoarthrosis, which is demonstrated by enhanced MR imaging. Received: 17 June 1998; Revision received: 22 October 1998; Accepted: 27 October 1998     

The spectrum of imaging in Currarino triad

The aim of this study was to evaluate the spectrum of findings and the efficacy of different imaging modalities in order to formulate recommendations for diagnostic imaging of Currarino triad (ASP syndrome), including screening of relatives. The imaging films of five female patients (age range 6 weeks to 12 months) were analysed retrospectively. The studied material consisted of US and MRI of the lower spine (5 patients each), lumbosacral plain radiography (4 patients), contrast enema (4 patients), urinary US (2 patients), genitography (1 patient) and myelo-CT (1 patient). Depiction of pathological findings with different imaging modalities was reviewed and validated with special respect to their demonstrability by US. Ultrasonography detected the sacral bony defect as well as the presacral pathology (meningocele and/or tumour) and thereby gave the basic diagnosis in all of the cases. It also depicted tethered cord and urinary tract abnormalities correctly. Magnetic resonance imaging gave a more distinct visualization of pre- and intraspinal pathology with additional demonstration of intraspinal lipoma in two cases. Regarding anorectal and genital malformations, radiographic contrast agent studies had been used in all patients. Two blind-ending retrorectal fistulas, depicted by enema, were missed by MRI. Patients with congenital or early infancy obstipation, anorectal malformations and complex urinary tract malformations should have spinal and pelvic sonography first. A plain film of the sacrum is recommended in equivocal cases. The need for MRI and contrast agent studies depends on the individual pathology, whereas presently MRI has made further radiographic imaging increasingly dispensable. A screening program with lumbosacral US or plain radiography for families with Currarino triad should be obligatory. Received: 22 May 1998; Revision received: 12 November 1998; Accepted: 6 January 1999     

Multidisciplinary Functional MR Imaging for Prostate Cancer

Various functional magnetic resonance (MR) imaging techniques are used for evaluating prostate cancer including diffusion-weighted imaging, dynamic contrast-enhanced MR imaging, and MR spectroscopy. These techniques provide unique information that is helpful to differentiate prostate cancer from non-cancerous tissue and have been proven to improve the diagnostic performance of MRI not only for cancer detection, but also for staging, post-treatment monitoring, and guiding prostate biopsies. However, each functional MR imaging technique also has inherent challenges. Therefore, in order to make accurate diagnoses, it is important to comprehensively understand their advantages and limitations, histologic background related with image findings, and their clinical relevance for evaluating prostate cancer. This article will review the basic principles and clinical significance of functional MR imaging for evaluating prostate cancer.     

Three-dimensional contrast-enhanced magnetic resonance angiography of the thoracic vasculature

Magnetic resonance angiography (MRA) has become a useful non-invasive imaging technique for the assessment of vascular disease. Due to limitations such as respiratory motion artefacts, saturations problems, and long acquisition times, applications of MRA in the thorax have largely been restricted to imaging of the aorta. The recent introduction of breath-hold three-dimensional (3D) contrast-enhanced MRA promises not only to enhance conventional MR protocols for aortic imaging, but to extend the clinical indications of MRI to diseases affecting other vascular structures of the thorax, most notably the pulmonary arteries. This article describes the technical aspects of contrast-enhanced 3D MRA and reviews existing and potential future clinical applications. Received 17 September 1996; Revision received 6 November 1996; Accepted 8 November 1996     

Contrast-enhanced MR angiography of abdominal vessels: Is there still a role for angiography?

The purpose of this review article is to describe recent advantages in contrast-enhanced (CE) three-dimensional (3D) magnetic resonance angiography (MRA) in comparison with other vascular imaging techniques, and to discuss their current clinical applications for the imaging of abdominal vessels. Principles and technical considerations are presented and clinical applications are reviewed for different vascular diseases. In ruptured aortic aneurysms and acute dissections CT is the method of first choice. Contrast-enhanced 3D MRA can be well used for therapeutic planning and follow-up in patients with stable disease. A comprehensive MR examination including CE 3D MRA, MR urography and MR nephrogram has the potential to replace the conventional studies for the evaluation of renal vascular disease. It is an accurate method for imaging the origins of coeliac and superior mesenteric arteries, although the image resolution is too low for reliable assessment of the inferior mesenteric artery. Contrast-enhanced 3D MRA has emerged as the method of choice for studying the portal venous system in liver transplant recipients, in patients with portal hypertension and in cases with abdominal tumours for preoperative evaluation. Additional non-invasive flow measurements are useful in monitoring portal hypertension. The abdominal veins can be well imaged using unenhanced MR techniques. Imaging may be facilitated with intravascular contrast media. Contrast-enhanced 3D MRA can replace intra-arterial DSA for diagnosis, therapy planning and follow-up in patients with abdominal vascular disease. Catheter-based arteriography will still be used for interventional procedures such as percutaneous transluminal angioplasty, stent placement and embolisation.     

Systemic mastocytosis: MRI of bone marrow involvement

Systemic mastocytosis (SM) is an abnormal proliferation of mast cells, located in different structures: skin, bone marrow, spleen, liver and lymph nodes. Magnetic resonance imaging was prospectively performed in ten patients diagnosed by bone marrow biopsy in order to describe the different patterns of bone marrow involvement. Coronal T1-weighted spin-echo images were obtained in vertebral, pelvic, humeral and femoral bones. Depending on the extension of the cell infiltration, three patterns of bone marrow involvement were used: normal/no involvement (N), non-homogeneous (NH) and homogeneous (H). All ten patients presented bone infiltration. The patterns observed were: spine (50 % NH, 50 % H), pelvis (70 % NH), humerus 100(NH) and femur 40 % (NH). T1-weighted MR imaging is a sensitive technique for detecting marrow abnormalities in patients with systemic mastocytosis. There is no correlation between percentage of mast cells in bone marrow biopsy and extent or pattern of bone marrow involvement. Received: 5 June 1998; Revision received: 23 November 1998; Accepted: 15 January 1999     

Osteomyelitis: a review of currently used imaging techniques

Conventional radiographs remain the initial imaging modality involved in the diagnosis of osteomyelitis. Bone scintigraphy and its specific agents did not only eliminate the problems of inherent low sensitivity of conventional radiographs, but also increased the specificity to higher degrees. Spiral CT, on the other hand, has solved several diagnostic problems, such as osteomyelitis of the sterno-clavicular junction and hidden areas in the pelvic bones. Magnetic resonance imaging with its multiplanar capability, greater anatomic details and excellent soft tissue bone marrow contrast resolution has a significant role in surgical planning and limb preservation. Ultrasound and US-guided aspiration has recently been involved in the diagnosis and management of osteomyelitis with several advantages particularly in children. Our goal in this review is to outline the ability of various imaging techniques by comparing their strengths and weaknesses in the diagnosis of osteomyelitis. Finally, we suggest various imaging algorithms for specific clinical scenarios. Spondylitis and septic arthritis are not discussed in this review. Received: 18 May 1998; Revision received: 6 July 1998; Accepted: 28 August 1998     

Cartilage imaging: motivation,techniques, current and future significance

Cartilage repair techniques and pharmacological therapies are currently areas of major clinical interest and research, in particular to prevent and treat osteoarthritis. MR imaging-based techniques to visualize cartilage are prerequisites to guide and monitor these therapies. In this review article, standard MR imaging sequences are described, including proton density-weighted fast spin echo, spoiled gradient echo and dual echo steady state sequences. In addition, new sequences that have been developed and are currently being investigated are presented, including driven equilibrium Fourier transform and steady-state free precession-based imaging. Using high-field MR imaging at 3.0-T, visualization of cartilage and the related pathology has been improved. Volumetric quantitative cartilage MR imaging was developed as a tool to monitor the progression of osteoarthritis and to evaluate new pharmacological cartilage protective therapies. The most exciting developments, however, are in the field of cartilage matrix assessment with quantitative dGEMRIC, T2 and T1rho mapping techniques. These techniques aim at detecting cartilage damage at a stage when changes are potentially still reversible, before cartilage tissue is lost. There is currently substantial interest in these techniques from rheumatologists and orthopedists; radiologists therefore need to keep up with these developments.     

Initial experience of MR/PET in a clinical cancer center

Magentic Resonance/positron emission tomography (PET) has been introduced recently for imaging of clinical patients. This hybrid imaging technology combines the inherent strengths of MRI with its high soft‐tissue contrast and biological sequences with the inherent strengths of PET, enabling imaging of metabolism with a high sensitivity. In this article, we describe the initial experience of MR/PET in a clinical cancer center along with a review of the literature. For establishing MR/PET in a clinical setting, technical challenges, such as attenuation correction and organizational challenges, such as workflow and reimbursement, have to be overcome. The most promising initial results of MR/PET have been achieved in anatomical areas where high soft‐tissue and contrast resolution is of benefit. Head and neck cancer and pelvic imaging are potential applications of this hybrid imaging technology. In the pediatric population, MR/PET can decrease the lifetime radiation dose. MR/PET protocols tailored to different types of malignancies need to be developed. After the initial exploration phase, large multicenter trials are warranted to determine clinical indications for this exciting hybrid imaging technology and thereby opening new horizons in molecular imaging. J. Magn. Reson. Imaging 2014;39:768–780. © 2013 Wiley Periodicals, Inc .     

MR imaging of musculoskeletal trauma to the pelvis and the lower limb

Magnetic resonance imaging can be used in the trauma setting to detect fractures and associated soft tissue injuries of the musculoskeletal system. Magnetic resonance imaging complements plain radiography and CT for evaluating cancellous bone, cartilage and growth-plate injuries, and intra- and extraarticular supporting soft tissue structures. This review outlines typical applications and imaging consideration for injuries of the pelvis and lower extremity. Received: 13 March 1998; Revision received: 6 July 1998; Accepted: 10 July 1998     

MR spectroscopic imaging: Principles and recent advances

MR spectroscopic imaging (MRSI) has become a valuable tool for quantifying metabolic abnormalities in human brain, prostate, breast and other organs. It is used in routine clinical imaging, particularly for cancer assessment, and in clinical research applications. This article describes basic principles of commonly used MRSI data acquisition and analysis methods and their impact on clinical applications. It also highlights technical advances, such as parallel imaging and newer high‐speed MRSI approaches that are becoming viable alternatives to conventional MRSI methods. Although the main focus is on ¹H‐MRSI, the principles described are applicable to other MR‐compatible nuclei. This review of the state‐of‐the‐art in MRSI methodology provides a framework for critically assessing the clinical utility of MRSI and for defining future technical development that is expected to lead to increased clinical use of MRSI. Future technical development will likely focus on ultra‐high field MRI scanners, novel hyperpolarized contrast agents using metabolically active compounds, and ultra‐fast MRSI techniques because these technologies offer unprecedented sensitivity and specificity for probing tissue metabolic status and dynamics. J. Magn. Reson. Imaging 2013;37:1301–1325. © 2012 Wiley Periodicals, Inc.