Approaches for the optimization of MR protocols in clinical hybrid PET/MRI studies

Magnetic resonance imaging (MRI) is the examination method of choice for the diagnosis of a variety of diseases. MRI allows us to obtain not only anatomical information but also identification of physiological and functional parameters such as networks in the brain and tumor cellularity, which plays an increasing role in oncologic imaging, as well as blood flow and tissue perfusion. However, in many cases such as in epilepsy, degenerative neurological diseases and oncological processes, additional metabolic and molecular information obtained by PET can provide essential complementary information for better diagnosis. The combined information obtained from MRI and PET acquired in a single imaging session allows a more accurate localization of pathological findings and better assessment of the underlying physiopathology, thus providing a more powerful diagnostic tool. Two hundred and twenty-one patients were scanned from April 2011 to January 2012 on a Philips Ingenuity TF PET/MRI system. The purpose of this review article is to provide an overview of the techniques used for the optimization of different protocols performed in our hospital by specialists in the following fields: neuroradiology, head and neck, breast, and prostate imaging. This paper also discusses the different problems encountered, such as the length of studies, motion artifacts, and accuracy of image fusion including physical and technical aspects, and the proposed solution

Diagnostic des lésions ischémiques avec un scanner double-énergie après thrombectomie mécanique

Les accidents cérébraux ischémiques sont une cause importante de morbidité et de mortalité. La cause la plus fréquente est la maladie thromboembolique. Le traitement actuel comporte la lyse intraveineuse ou intra-artérielle et dans certains cas la thrombectomie mécanique. Une des complications du traitement est la transformation hémorragique. Cette complication est difficile à détecter dans les suites immédiates de la thrombectomie mécanique car il existe une rupture de la barrière hémato-encéphalique avec une extravasation de produit de contraste utilisé pendant le geste, ce contraste hyperdense au scanner est impossible à distinguer d'une hémorragie. Le scanner double-énergie permet de différencier entre ces deux entités et permet également une meilleure détection de l'ischémie ce qui traduit un facteur pronostic important

X-Ray Versus Magnetic Resonance Imaging in Diabetic Foot Osteomyelitis: A Clinical Comparison

OBJECTIVE Radiographic imaging is an important diagnostic tool in diabetic foot osteomyelitis (DFO). It is unknown whether DFO cases diagnosed with conventional X-ray versus positive Magnetic Resonance Imaging (MRI) differ regarding epidemiology and treatment outcome. Theoretically, signs of inflammation on MRI without bone lesions might be easier to treat and predominate among selected clinical variables. METHODS Our clinical pathway for diabetic foot infections discourages the use of MRI for the diagnosis of DFO. We compared the epidemiology and therapy of non-amputated DFO with positive features on conventional X-ray, MRI, or both. Radiology specialists interpreted the images. The intraoperative aspect of bone during amputation and the results of bone cultures were considered gold standard for DFO diagnosis. RESULTS We prospectively followed 390 DFO episodes in 186 adult patients for a median of 2.9 years and performed 318 conventional X-rays (median costs 100 Swiss Francs; 100 US$) and 47 (47/390; 12$). Among them, 18 episodes were associated with positive MRI findings but lacked bone lesions on X-ray. After debridement, the median duration of systemic antibiotics was 28 days for MRI-only episodes and 30 days for X-ray-positive cases (Wilcoxon-ranksum-test; p=0.26). The corresponding median numbers of surgical debridements were 1 and 1; and remission was achieved in 25% and 27%, respectively. In multivariate logistic regression analysis, MRI-only episodes did not alter remission rate (odds ratio 0.5, 95%CI 0.1-5.2). CONCLUSIONS According to our clinical pathway, DFO episodes with positive MRI findings only did not differ epidemiologically and did not influence the choice of therapy nor remission rate

The role of imaging in cancer patients : challenges and perspectives

Imaging in the medical field has grown in importance over the past decades with the development of sophisticated cross-sectional imaging techniques including computed tomography (CT), magnetic resonance imaging (MRI) and hybrid imaging techniques (PET-CT and PET-MR). It has also become primordial in the initial diagnosis and staging of cancer patients and in the evaluation of treatment response. The most widely used technique is CT as it is a robust imaging method which provides whole body information in a short acquisition time and is readily accessible. The main disadvantage of this imaging method is that it relies on X-rays and is the main source of radiation exposure due to medical imaging in the general population. This thesis will firstly describe different methods that have been developed and are currently employed for dose reduction in CT and will then go on to outline the role of alternative imaging techniques including whole body MRI and PET-MR in cancer patients. Finally, future perspectives in the field of cancer imaging will be discussed with emphasis on quantitative image texture analysis and artificial intelligence

Hybrid PET/MRI as a tool to detect brown adipose tissue: Proof of principle

The purpose of this study was to assess the performance of (18)F-FDG hybrid PET/MRI to detect and localise the presence of metabolically active brown adipose tissue (BAT)

Imaging of autoimmune epilepsies

Epilepsy due to an autoimmune disease is a recently recognized entity. Among the best-known diseases are paraneoplastic limbic encephalitis, limbic encephalitis associated with voltage-gated potassium channels (VGKC)) antibody glutamic acid decarboxylase antacid, antireceptor antibodies N-methyl-D-aspartate, Rasmussen and Hashimoto encephalitis. More efficient imaging technics and immunologic laboratory analyses have allowed us to deepen our knowledge concerning these diseases that are most common in adults. In this article we will describe the most common imagery findings and the most appropriate methods of image analysis

Spinal Vascular Imaging: Technique

In this chapter, the principal imaging techniques of vascular pathologies of the spine and spinal cord are described, including computed tomography angiography (CTA), magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and digital subtraction angiography (DSA) as well as the technical protocols, the different vascular patterns to recognize, and the clinical indications where these techniques can be applied. MRI is the technique of choice for the firstline approach of vascular lesions and their follow-up. It is the only non-radiating technique that allows visualization of the spinal cord and spinal vessels. It also permits the differential diagnosis with other nonvascular diseases. Currently, DSA is used mainly for therapeutic purposes and for detailed analysis particularly in small vascular malformations. Finally, the advantages of each technique will be illustrated with clinical examples

New patterns of magnetic resonance images in high-grade glioma patients treated with bevacizumab (Avastin®)

Objectives: To identify new magnetic resonance imaging (MRI) patterns in patients with high-grade glioma treated with bevacizumab (Avastin®). Methods: The retrospective study was approved by the institutional review board. An extended case series of 27 patients (19 men, 8 women) with age range of 22–76 years and an average age 52 years were studied by 1.5T/3T MRI (Siemens scanner Erlangen, Germany). Protocol included axial T1-wi spin echo (SE), axial T2-wi fast SE, three-dimensional fluid-attenuated inversion recovery (3D FLAIR), axial diffusion tensor imaging, axial T2-wi gradient echo (GE), dynamic-susceptibility contrast T2-perfusion, axial T1-wi post-gadolinium (Gd) (0.2 ml/kg of body weight) and 3D T1-wi (weighted) GE post-Gd. Evaluation comprised oedema or low-grade tumour infiltration using FLAIR sequences, perfusion using relative cerebral blood volume (rCBV) and enhancement using T1-wi post-medium contrast images. Results: At baseline, the study included 27 patients, of which 14 patients were excluded and 13 patients analysed. One patient under treatment showed persistent hyperperfusion, three mixed perfusion, six hypoperfusion and three normal perfusion. FLAIR sequences were used in oedema analysis. When treated, 10 patients showed decrease in perilesional oedema, 1 showed increase in perilesional oedema and 2 had stability in perilesionnal oedema. Lesion enhancement was analysed using axial T1-wi SE post-Gd images; 12 patients showed decrease and 1 patient showed stability in lesion enhancement. Conclusions: Bevacizumab (Avastin) alters the process of angiogenesis resulting in different perfusion patterns in patients with disease progression that must be known in order to avoid erroneous interpretation

Three-Dimensional MR Imaging of the Brachial Plexus

Pathologic conditions of the brachial plexus often result in serious and disabling complications. With the increasing availability and use of new and powerful MRI sequences and coils, understanding and assessment of the complex anatomy and pathology of the brachial plexus have been greatly facilitated. These new technical developments have led to an improved assessment of brachial plexus lesions, thereby improving patient care. In this article we describe various MRI techniques for the evaluation of the brachial plexus obtained at 1.5 T and 3 T, and we explain differences and similarities between sequences and protocols performed on MRI equipment from different vendors. The main characteristics of pathologic conditions affecting the brachial plexus are discussed and illustrated, as well as their differential diagnoses, with an emphasis on key imaging findings and relevance for patient management. Pitfalls related to suboptimal technique and image interpretation are also addressed