Search

Edema of the quadriceps fat pad (QFP) in MR imaging has been described as a distinct finding associated with anterior knee pain, its etiology, however, remains under debate. The aim of this study was to investigate a potential relationship between QFP edema, alterations of the quadriceps tendon (QT) and other anterior knee structures.800 consecutive, clinically indicated MRI exams of the knee at 3T were retrospectively analyzed for the absence or presence of QFP edema. If present, QFP edema was determined visually by three independent readers and classified into 3 grades (A to C); concomitant alterations of the QT were classified into 5 grades (1 to 5). Furthermore, QT thickness, femoropatellar cartilage degeneration and parameters of patellar instability were determined. 20 MRI studies of healthy individuals served as control group. For statistical analysis Kruskal-Wallis test, one-way ANOVA and Fleiss kappa were used.153 of 800 patients (19%) presented with various degrees of QFP edema. Analysis showed significantly higher grades of QT alterations in patients with intermediate (grade B) and intensive (grade C) QFP edema (p .001) compared to controls and also significantly different grades of QT alterations in patients with mild and intermediate compared to those with intensive QFP edema (p .001). Increased mean QT thickness was found in patients with intermediate and intensive QFP edema compared to controls (p .05).Our study suggests that QFP edema shows an association with QT alterations and QT thickness.

In diffusion-weighted magnetic resonance imaging (DWI), the intensity of the acquired magnetic resonance signal depends on the self-diffusion of the excited spins, i.e., on the microscopic stochastic Brownian molecular motion. Since the extent and orientation of molecular motion is influenced by the microscopic structure and organization of biological tissues, DWI can depict various pathological changes of organs or tissues. While DWI of the brain can be considered an established technique since the mid-1990s, significantly fewer studies have been published about DWI in body imaging, mainly because of the relatively low robustness of conventional DWI methods in non-neurological applications. Consequently, the image quality in such applications was rather limited. This situation, however, improved considerably in recent years due to better hardware as well as new pulse sequences, and several new applications of DWI (e.g., in the abdominal organs, in musculoskeletal applications, or in whole-body protocols) have been described. Unfortunately, DWI of the body is complicated by frequently low signal-to-noise ratios due to shorter transversal (T2) relaxation times and by strong variations of susceptibility. The latter result in severe distortion artifacts when standard echo-planar DWI techniques are applied. Hence, several alternative (non-echo-planar) diffusion-weighting pulse sequence types were proposed and evaluated for DWI applications in the body. In this review article, first the basics of molecular diffusion and of diffusion-weighted MRI are introduced and then several specific MRI techniques, which have been used for DWI of the body, are described. Finally, protocol recommendations for different DWI applications in the body are provided.

The advent of whole-body MRI (WB-MRI) has introduced tumor imaging with a systemic approach compared to established sequential, multi-modal diagnostic algorithms. Hardware innovations, such as the introduction of multi-receiver channel whole-body scanners at 1.5 T and recently 3 T, combined with acquisition acceleration techniques, have made high resolution WB-MRI clinically feasible. Now, a dedicated assessment of individual organs with various soft tissue contrast, spatial resolution and contrast media dynamics can be combined with whole-body anatomic coverage in a multi-planar imaging approach. More flexible protocols, e.g. including T1-weighted TSE- and STIR-imaging, dedicated lung imaging or dynamic contrast-enhanced studies of the abdomen can be performed within less than 45 min. For initial tumor staging PET-CT as a competing whole-body modality in oncologic imaging has proved more accurate for the definition of T-stage and lymph node assessment, using the additional metabolic information of PET for the assessment of tumor viability and therapy response. However, new applications, such as MR-whole-body diffusion imaging, may significantly increase sensitivity in near future. WB-MRI has shown advantages for the detection of distant metastatic disease, especially from tumors frequently spreading to the liver or brain and it is especially useful as a radiation-free alternative for the surveillance of tumor patients with multiple follow-up exams. Furthermore, it has been introduced as a whole-body bone marrow screening application. Within this context WB-MRI is highly accurate for the detection of skeletal metastases and staging of hematologic diseases, such as multiple myeloma or lymphoma. This article summarizes recent developments and applications of WB-MRI and highlights its performance within the scope of systemic oncologic staging and surveillance.

The aim of the study was to evaluate the diagnostic accuracy of multi-slice-computed tomography (MDCT) for the detection of vertebral metastases in comparison to magnetic resonance imaging (MRI).In a retrospective analysis, 639 vertebral bodies of 41 patients with various histologically confirmed primary malignancies were analysed. The MDCT-images were acquired on a 16/64-row-MDCT scanner (Siemens Somatom Sensation 16/64). MRI was performed on 1.5 T scanners (SIEMENS Symphony/Sonata). The MDCT- and MRI-images were evaluated separately by two experienced radiologists in a consensus reading. The combination of MDCT and MRI in an expert reading including follow-up examinations and/or histology as well as clinical data served as the gold standard.201/639 vertebral bodies were defined as metastatically affected by the gold standard. In MDCT 133/201 lesions, in MRI 198/201 lesions were detected. 68 vertebral bodies were false negative in MDCT, whereas 3 false negatives were found in MRI. 3 false positive results were obtained in MDCT, 5 in MRI. Sensitivity was significantly lower for MDCT (66.2%) than for MRI (98.5%) (p0.0001). Specificity was not significantly different for both methods (MDCT: 99.3%; MRI: 98.9%). The diagnostic accuracy resulted in 88.8% for MDCT and 98.7% for MRI.Although 16/64-row-MDCT provides excellent image quality and a high spatial resolution in the assessment of bony structures, metastatic lesions without significant bone destruction may be missed. The diagnostic accuracy of MRI proved to be significantly superior to 16/64-row-MDCT for the detection of osseous metastases.

In diffusion-weighted magnetic resonance imaging (DWI), the observed MRI signal intensity is attenuated by the self-diffusion of water molecules. DWI provides information about the microscopic structure and organization of a biological tissue, since the extent and orientation of molecular motion is influenced by these tissue properties. The most common method to measure perfusion in the body using MRI is T1-weighted dynamic contrast enhancement (DCE-MRI). The analysis of DCE-MRI data allows determining the perfusion and permeability of a biological tissue. DWI as well as DCE-MRI are established techniques in MRI of the brain, while significantly fewer studies have been published in body imaging. In recent years, both techniques have been applied successfully in healthy bone marrow as well as for the characterization of bone marrow alterations or lesions; e.g., DWI has been used in particular for the differentiation of benign and malignant vertebral compression fractures. In this review article, firstly a short introduction to diffusion-weighted and dynamic contrast-enhanced MRI is given. Non-quantitative and quantitative approaches for the analysis of DWI and semiquantitative and quantitative approaches for the analysis of DCE-MRI are introduced. Afterwards a detailed overview of the results of both techniques in healthy bone marrow and their applications for the diagnosis of various bone-marrow pathologies, like osteoporosis, bone tumors, and vertebral compression fractures are described.

To evaluate the potential and to analyze parameter correlations of combined quantitative diffusion-weighted MRI (DWI) and high-temporal-resolution dynamic contrast-enhanced MRI (DCE-MRI) in vertebral bone marrow (vBM) of patients with osteoporosis and acute vertebral compression fractures, providing additional information for a better understanding of the physiological background of parameter changes.20 patients with acute osteoporotic fractures were examined with DWI and DCE-MRI at 1.5 T. DCE-MRI was performed with a 2D saturation-recovery turbo-FLASH sequence, acquiring 300 dynamics with a temporal resolution of 1 s. For DWI measurements, a DW HASTE sequence with b-values from 100 to 600 s/mm² was applied. In each patient, ROIs were drawn manually in the fractures and in normal appearing vertebrae. For DCE-MRI, the concentration-time curves of these ROIs were analyzed using a two-compartment tracer-kinetic model in the lesions, providing separate estimates of perfusion and permeability, and a one-compartment model in normal vBM, providing only a mixed representation of perfusion and permeability in terms of a mixed flow parameter K(trans) and the extracellular volume (ECV). In the case of DWI, attenuation curves were fitted to a monoexponential decay model to determine the apparent diffusion coefficient (ADC).Mean perfusion parameters and ADCs were significantly (p0.001) different in the fractures compared to adjacent normal appearing vertebrae (K(trans): 7.81 mL/100 mL/min vs. 14.61 mL/100 mL/min, ECV: 52.84 mL/100 mL vs. 4.61 mL/100 mL, ADC: 1.71×10⁻³ mm²/s vs. 0.57×10⁻³ mm²/s). ADCs showed a significant correlation with the ECV.The quantitative analysis of DWI and DCE-MRI could distinguish osteoporotic fractures from normal appearing vertebrae. A significant correlation found between ECV and ADCs might be able to explain the cause for the increased diffusivity in osteoporotic fractures. Since the other perfusion parameters do not correlate with the ADC, they provide additional pathophysiological information not accessible with DWI.

Purpose To compare the diagnostic accuracy for the detection of tumor recurrence in breast cancer patients using whole-body-MRI (WB-MRI) at 1.5 or 3 T compared to FDG–PET–CT. Materials and methods Thirty-three female patients with breast cancer and suspicion of recurrence underwent FDG–PET–CT and WB-MRI. Coronal T1w-TSE- and STIR-sequences, HASTE-imaging of the lungs, contrast-enhanced T1w- and T2w-TSE-sequences of the liver, brain and abdomen were performed, using a WB-MRI-scanner at 1.5 (n = 23) or 3 T (n = 10). Presence of local recurrence, lymph node involvement and distant metastatic disease was assessed using clinical and radiological follow-up as a standard of reference. Results Tumor recurrence was found in 20 of 33 patients. Overall 186 malignant foci were detected with WB-MRI and PET–CT. Both modalities revealed two recurrent tumors of the breast. PET–CT detected more lymph node metastases (n = 21) than WB-MRI (n = 16). WB-MRI was more precise in the detection of distant metastases (n = 154 versus n = 147). Sensitivity was 93% (172/186) and 91% (170/186) for WB-MRI and PET–CT, specificity was 86% (66/77) and 90% (69/77), respectively. Examination times for WB-MRI at 1.5 and 3 T were 51 and 43 min, respectively, examination time for PET–CT was 103 min. Conclusion WB-MRI and PET–CT are useful for the detection of tumor recurrence in the follow-up of breast cancer. WB-MRI is highly sensitive to distant metastatic disease. PET–CT is more sensitive in detecting lymph node involvement. Tumor screening with WB-MRI is feasible at 1.5 and 3 T, scan time is further reduced at 3 T with identical resolution.

In clinical routine, multimodality algorithms, including X-ray, computed tomography, scintigraphy and MRI, are used in case of suspected bone marrow malignancy. Skeletal scintigraphy is widely used to asses metastatic disease to the bone, CT is the technique of choice to assess criteria of osseous destruction and bone stability. MRI is the only imaging technique that allows direct visualization of bone marrow and its components with high spatial resolution. The combination of unenhanced T1-weighted-spin echo- and turbo-STIR-sequences have shown to be most useful for the detection of bone marrow abnormalities and are able to discriminate benign from malignant bone marrow changes. Originally, whole-body MRI bone marrow screening was performed in sequential scanning techniques of five body levels with time consuming coil rearrangement and repositioning of the patient. The introduction of a rolling platform mounted on top of a conventional MRI examination table facilitated whole-body MR imaging and, with the use of fast gradient echo, T1-weighted and STIR-imaging techniques, for the first time allowed whole-body imaging within less than one hour. With the development of parallel imaging techniques (PAT) in combination with global matrix coil concepts, acquisition time could be reduced substantially without compromises in spatial resolution, enabling the implementation of more complex and flexible examination protocols. Whole-body MRI represents a new alternative to the stepwise multimodality concept for the detection of metastatic disease, multiple myeloma and lymphoma of the bone with high diagnostic accuracy.

Diffusion-weighted magnetic resonance imaging (DWI) is an imaging technique which is sensitive to random water movements in spatial scales far below those typically accessible by magnetic resonance imaging (MRI). This property makes DWI a powerful tool for diagnosis of diseases which involve alterations in water mobility, such as acute stroke. In bone marrow, DWI has been proven to be a highly useful method for the differential diagnosis of benign and malignant compression fractures. Unfortunately, the application of DWI sequences to the bone marrow frequently suffers from artifacts, which in some cases seriously restrict the diagnostic utility of the image. This requires the introduction of additional correction techniques, or even the development of new sequences. Thus, the selection of an adequate imaging technique for DWI of the bone marrow is a very important issue. In this article the most important sequences for DWI of the bone marrow are reviewed. Special attention is paid to the problems associated with these sequences, as well as their possible solutions.