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1.
Methodological consensus on clinical proton MRS of the brain: Review and recommendations.
Wilson, M, Andronesi, O, Barker, PB, Bartha, R, Bizzi, A, Bolan, PJ, Brindle, KM, Choi, IY, Cudalbu, C, Dydak, U, et al
Magnetic resonance in medicine. 2019;(2):527-550
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Abstract
Proton MRS (1 H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption has been slow for several reasons, and technical challenges toward obtaining reliable good-quality results have been identified as a contributing factor. Considerable progress has been made by the research community to address many of these challenges, and in this paper a consensus is presented on deficiencies in widely available MRS methodology and validated improvements that are currently in routine use at several clinical research institutions. In particular, the localization error for the PRESS localization sequence was found to be unacceptably high at 3 T, and use of the semi-adiabatic localization by adiabatic selective refocusing sequence is a recommended solution. Incorporation of simulated metabolite basis sets into analysis routines is recommended for reliably capturing the full spectral detail available from short TE acquisitions. In addition, the importance of achieving a highly homogenous static magnetic field (B0 ) in the acquisition region is emphasized, and the limitations of current methods and hardware are discussed. Most recommendations require only software improvements, greatly enhancing the capabilities of clinical MRS on existing hardware. Implementation of these recommendations should strengthen current clinical applications and advance progress toward developing and validating new MRS biomarkers for clinical use.
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2.
Magnetic resonance thermometry and its biological applications - Physical principles and practical considerations.
Odéen, H, Parker, DL
Progress in nuclear magnetic resonance spectroscopy. 2019;:34-61
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Abstract
Most parameters that influence the magnetic resonance imaging (MRI) signal experience a temperature dependence. The fact that MRI can be used for non-invasive measurements of temperature and temperature change deep inside the human body has been known for over 30 years. Today, MR temperature imaging is widely used to monitor and evaluate thermal therapies such as radio frequency, microwave, laser, and focused ultrasound therapy. In this paper we cover the physical principles underlying the biological applications of MR temperature imaging and discuss practical considerations and remaining challenges. For biological tissue, the MR signal of interest comes mostly from hydrogen protons of water molecules but also from protons in, e.g., adipose tissue and various metabolites. Most of the discussed methods, such as those using the proton resonance frequency (PRF) shift, T1, T2, and diffusion only measure temperature change, but measurements of absolute temperatures are also possible using spectroscopic imaging methods (taking advantage of various metabolite signals as internal references) or various types of contrast agents. Currently, the PRF method is the most used clinically due to good sensitivity, excellent linearity with temperature, and because it is largely independent of tissue type. Because the PRF method does not work in adipose tissues, T1- and T2-based methods have recently gained interest for monitoring temperature change in areas with high fat content such as the breast and abdomen. Absolute temperature measurement methods using spectroscopic imaging and contrast agents often offer too low spatial and temporal resolution for accurate monitoring of ablative thermal procedures, but have shown great promise in monitoring the slower and usually less spatially localized temperature change observed during hyperthermia procedures. Much of the current research effort for ablative procedures is aimed at providing faster measurements, larger field-of-view coverage, simultaneous monitoring in aqueous and adipose tissues, and more motion-insensitive acquisitions for better precision measurements in organs such as the heart, liver, and kidneys. For hyperthermia applications, larger coverage, motion insensitivity, and simultaneous aqueous and adipose monitoring are also important, but great effort is also aimed at solving the problem of long-term field drift which gets interpreted as temperature change when using the PRF method.
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T2* Mapping Techniques: Iron Overload Assessment and Other Potential Clinical Applications.
Menacho, K, Abdel-Gadir, A, Moon, JC, Fernandes, JL
Magnetic resonance imaging clinics of North America. 2019;(3):439-451
Abstract
T2* mapping techniques has evolved significantly since their introduction in the early 2000s and a significant amount of evidence has been gathered to support their clinical routine use for iron overload assessment. This article focuses on the most important aspects of how to perform T2* imaging, from acquisition, to postprocessing, to analyzing the data with clinical concentration. Newer techniques have made T2* mapping more robust and accurate, allowing a broader use of this technique for noncontrast ischemia imaging based on blood oxygen levels, in addition to evaluation of intramyocardial hemorrhage and microvascular obstruction.
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4.
Quantitative pancreatic MRI: a pathology-based review.
Chouhan, MD, Firmin, L, Read, S, Amin, Z, Taylor, SA
The British journal of radiology. 2019;(1099):20180941
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Abstract
MRI plays an important role in the clinical management of pancreatic disorders and interpretation is reliant on qualitative assessment of anatomy. Conventional sequences capturing pancreatic structure can however be adapted to yield quantitative measures which provide more diagnostic information, with a view to increasing diagnostic accuracy, improving patient stratification, providing robust non-invasive outcome measures for therapeutic trials and ultimately personalizing patient care. In this review, we evaluate the use of established techniques such as secretin-enhanced MR cholangiopancreatography, diffusion-weighted imaging, T 1, T 2* and fat fraction mapping, but also more experimental methods such as MR elastography and arterial spin labelling, and their application to the assessment of diffuse pancreatic disease (including chronic, acute and autoimmune pancreatitis/IgG4 disease, metabolic disease and iron deposition disorders) and cystic/solid focal pancreatic masses. Finally, we explore some of the broader challenges to their implementation and future directions in this promising area.
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Manganese Oxide Nanoparticles As MRI Contrast Agents In Tumor Multimodal Imaging And Therapy.
Cai, X, Zhu, Q, Zeng, Y, Zeng, Q, Chen, X, Zhan, Y
International journal of nanomedicine. 2019;:8321-8344
Abstract
Contrast agents (CAs) play a crucial role in high-quality magnetic resonance imaging (MRI) applications. At present, as a result of the Gd-based CAs which are associated with renal fibrosis as well as the inherent dark imaging characteristics of superparamagnetic iron oxide nanoparticles, Mn-based CAs which have a good biocompatibility and bright images are considered ideal for MRI. In addition, manganese oxide nanoparticles (MONs, such as MnO, MnO2, Mn3O4, and MnOx) have attracted attention as T1-weighted magnetic resonance CAs due to the short circulation time of Mn(II) ion chelate and the size-controlled circulation time of colloidal nanoparticles. In this review, recent advances in the use of MONs as MRI contrast agents for tumor detection and diagnosis are reported, as are the advances in in vivo toxicity, distribution and tumor microenvironment-responsive enhanced tumor chemotherapy and radiotherapy as well as photothermal and photodynamic therapies.
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Evaluation of Response to Stereotactic Radiosurgery in Brain Metastases Using Multiparametric Magnetic Resonance Imaging and a Review of the Literature.
Sawlani, V, Davies, N, Patel, M, Flintham, R, Fong, C, Heyes, G, Cruickshank, G, Steven, N, Peet, A, Hartley, A, et al
Clinical oncology (Royal College of Radiologists (Great Britain)). 2019;(1):41-49
Abstract
AIMS: Following stereotactic radiosurgery (SRS), brain metastases initially increase in size in up to a third of cases, suggesting treatment failure. Current imaging using structural magnetic resonance imaging (MRI) cannot differentiate between tumour recurrence and SRS-induced changes, creating difficulties with patient management. Combining multiparametric MRI techniques, which assess tissue physiological and metabolic information, has shown promise in answering this clinical question. MATERIALS AND METHODS Multiparametric MRI techniques, including spectroscopy, diffusion and perfusion imaging, were used for the differentiation of radiation-related changes and tumour recurrence after SRS for intracranial metastases in six cases. All patients presented with enlargement of the treated lesion, an increase in perilesional brain oedema and aggravation or appearance of neurological signs and symptoms from 7 to 29 weeks after primary treatment. RESULTS Multiparametric imaging helped to differentiate features of tumour progression (n = 4) from radiation-related changes (n = 2). A low apparent diffusion coefficient (ADC) <1000 × 10-6 mm2/s, high relative cerebral blood volume (rCBV) ratio > 2.1, high choline:creatine (Cho:Cr) ratio > 1.8 suggested tumour recurrence. A high ADC > 1000 × 10-6 mm2/s, low rCBV ratio < 2.1, Cho:Cr ratio < 1.8 suggested SRS-induced radiation changes. Multiparametric MRI diagnosis was confirmed by histology or radiological and clinical follow-up. CONCLUSION Multiparametric MRI was helpful in the early identification of radiation-related changes and tumour recurrence and may be useful for monitoring treatment changes in intracranial neoplasms after SRS treatment.
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Superior mesenteric artery syndrome: a radiographic review.
Warncke, ES, Gursahaney, DL, Mascolo, M, Dee, E
Abdominal radiology (New York). 2019;(9):3188-3194
Abstract
PURPOSE To provide a review of the etiology, clinical presentation, and imaging findings of superior mesenteric artery (SMA) syndrome. METHODS A literature review of 24 relevant articles regarding SMA syndrome was performed. RESULTS Clinicians and radiologists with a high index of suspicion based on symptomatology may pursue radiologic investigation in the form of upper gastrointestinal (GI) series and contrast-enhanced abdominal computed tomography (CT). Magnetic resonance imaging (MRI) and ultrasound (US) are less commonly utilized modalities in the work-up of SMA syndrome, but provide imaging alternatives without the use of ionizing radiation. Imaging can assist in diagnosis by demonstrating characteristic findings of reduced aortomesenteric angle, reduced aortomesenteric distance, gastroduodenal distention, bowel caliber narrowing at the takeoff of the superior mesenteric artery from the aorta, as well as delayed gastric emptying or positional obstruction observed with real time with fluoroscopy. CONCLUSION SMA syndrome is a rare disease that can go unrecognized and undiagnosed, exacerbating weight loss in an already significantly malnourished patient population. The diagnosis of SMA syndrome must be based on clinical symptomatology correlated with radiographic information. Once diagnosed, SMA syndrome can be safely treated by conservative measures although occasionally requires invasive intervention in the form of enteral tube placement, percutaneous jejunostomy tube placement, total parenteral nutrition, ligament of Treitz lysis, or duodenojejunostomy.
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A potential cause of adolescent onset Dyke-Davidoff-Masson syndrome: A case report.
Li, Y, Zhang, T, Li, B, Li, J, Wang, L, Jiang, Z
Medicine. 2019;(51):e18075
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Abstract
RATIONALE Dyke-Davidoff-Masson syndrome (DDMS) is a rare syndrome commonly occurring in children and characterized by cerebral hemiatrophy, hypertrophy of the skull, epilepsy, and mental retardation. However, few have been reported in China, especially in teenagers. This case investigated its possible cause and explored a relative effective solution. PATIENT CONCERNS A 24-year-old female came to department having experienced recurrent seizures for 12 years. DIAGNOSIS DDMS was diagnosed from its manifestations, biochemistry indexes, and imaging (computed tomography angiography, magnetic resonance venography, and so on). INTERVENTIONS Several drugs are used to treat the disease, including valproate, carbamazepine, topiramate, and ginkgo biloba extract. OUTCOMES Under the medicine treatment of magnesium valproate with carbamazepine, the patient experienced partial seizures approximately once per month that lasted 30 to 60 seconds each without any complications observed during a follow-up period of 24 months. CONCLUSION The imaging and clinical features of DDMS in this teenager were similar to those in classic infantile-onset cases. A potential cause of the disease could be brain trauma, which impaired the middle cerebral artery and reduced cerebral blood supply, leading to epilepsy and hemiatrophy. LESSONS It was concluded early diagnosis and pharmacotherapy are the keys to preventing intellectual decline in DDMS patients. Moreover, the combination of magnesium valproate and carbamazepine could significantly reduce the frequency and duration of seizures, despite not eliminating them completely.
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Uncommon Intraluminal Tumors of the Gallbladder and Biliary Tract: Spectrum of Imaging Appearances.
Chatterjee, A, Lopes Vendrami, C, Nikolaidis, P, Mittal, PK, Bandy, AJ, Menias, CO, Hammond, NA, Yaghmai, V, Yang, GY, Miller, FH
Radiographics : a review publication of the Radiological Society of North America, Inc. 2019;(2):388-412
Abstract
Intraluminal pathologic conditions of the bile ducts and gallbladder are common, most frequently consisting of calculi and adenocarcinoma. In recent years, intraductal papillary neoplasm of the bile ducts (IPN-B), which is analogous to intraductal papillary mucinous neoplasm of the pancreas, has been recognized as a distinct pathologic entity and a precursor lesion to adenocarcinoma of the bile ducts. Intraductal tubulopapillary neoplasm (ITPN) of the bile duct was subsequently described as a distinct pathologic entity. With increased awareness and advances in imaging techniques, these lesions are diagnosed with increased frequency at preoperative imaging. A similar neoplasm in the gallbladder is referred to as intracholecystic papillary neoplasm. These lesions are often diagnosed at a preinvasive stage and have a better prognosis than invasive cholangiocarcinoma when treated with curative resection, underscoring the importance of an accurate imaging diagnosis. The most common causes of polypoid lesions of the gallbladder are cholesterol polyps and adenomyomatosis. These lesions need to be differentiated from the less common but clinically important adenocarcinoma of the gallbladder. Imaging is crucial to identify polyps that are at high risk for malignancy so that the appropriate management choice between imaging follow-up and cholecystectomy can be made by the treating physicians. Other less common gallbladder tumors, such as gallbladder adenomas, lymphoma, and metastases to the gallbladder, can manifest as intraluminal tumors; and awareness of these lesions is also important. In this article, the recent literature is reviewed; and the imaging appearances, histopathologic findings, and management of uncommon intraluminal tumors of the bile ducts and gallbladder and their mimics are discussed. ©RSNA, 2019.
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Iron-Containing Abdominal Pathologies: Exploiting Magnetic Susceptibility Artifact on Dual-Echo Gradient-Echo Magnetic Resonance Imaging.
Thomas, AJ, Morani, AC, Liu, PS, Weadock, WJ, Hussain, HK, Elsayes, KM
Journal of computer assisted tomography. 2019;(2):165-175
Abstract
A multitude of pathologic entities involve abnormal iron deposition in the abdomen. These lesions demonstrate decreased signal on longer magnetic resonance sequences with longer echo time due to T2* effect. Dual-echo gradient-echo sequences demonstrate increased susceptibility artifact with longer echo sequences. In this article, the spectrum of iron-containing abdominal pathologies is illustrated, with their characteristic distributions. Included is a brief discussion of the physics of magnetic resonance imaging of iron-containing lesions.