Functional MR Imaging Techniques Research Articles

Assessment of Hypoxia in Breast Cancer: Emerging Functional MR Imaging and Spectroscopy Techniques and Clinical Applications.

Breast cancer is one of the most prevalent forms of cancer affecting women worldwide. Hypoxia, a condition characterized by insufficient oxygen supply in tumor tissues, is closely associated with tumor aggressiveness, resistance to therapy, and poor clinical outcomes. Accurate assessment of tumor hypoxia can guide treatment decisions, predict therapy response, and contribute to the development of targeted therapeutic interventions. Over the years, functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy (MRS) techniques have emerged as promising noninvasive imaging options for evaluating hypoxia in cancer. Such techniques include blood oxygen level-dependent (BOLD) MRI, oxygen-enhanced MRI (OE) MRI, chemical exchange saturation transfer (CEST) MRI, and proton MRS (1H-MRS). These may help overcome the limitations of the routinely used dynamic contrast-enhanced (DCE) MRI and diffusion-weighted imaging (DWI) techniques, contributing to better diagnosis and understanding of the biological features of breast cancer. This review aims to provide a comprehensive overview of the emerging functional MRI and MRS techniques for assessing hypoxia in breast cancer, along with their evolving clinical applications. The integration of these techniques in clinical practice holds promising implications for breast cancer management. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 1.

Essential Practical Steps for MRI of the Kidney in Experimental Research.

Magnetic resonance imaging (MRI) is an emerging method to obtain valuable functional and structural information about the kidney noninvasively. Before performing specialized MR measurements for probing tissue structure and function, some essential practical steps are needed, which are common for most applications. Here we describe in a step-by-step manner how to (1) achieve the double-oblique slice orientation coronal-to-the-kidney, (2) adapt the scan protocol for avoiding aortic flow artifacts and covering both kidneys, (3) perform localized shimming on the kidney, and (4) check perfusion in the large renal blood vessels using time-of-flight (TOF) angiography. The procedures are tailored to preclinical MRI but conceptionally are also applicable to human MRI.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter explains the initial and essential MRI steps that precede specific functional and structural MR imaging techniques (T1- and T2*-mapping, DWI , ASL , etc.), which are described in separate chapters.

Basic concepts and applications of functional magnetic resonance imaging for radiotherapy of prostate cancer.

Recently, the interest to integrate magnetic resonance imaging (MRI) in radiotherapy for prostate cancer has increased considerably. MRI can contribute in all steps of the radiotherapy workflow from diagnosis, staging, and target definition to treatment follow-up. Of particular interest is the ability of MRI to provide a wide range of functional measures. The complexity of MRI as an imaging modality combined with the growing interest of the application to prostate cancer radiotherapy, emphasize the need for dedicated education within the radiation oncology community. In this context, an overview of the most common as well as a few upcoming functional MR imaging techniques is presented: the basic methodology and measurement is described, the link between the functional measures and the underlying biology is established, and finally relevant applications of functional MRI useful for prostate cancer radiotherapy are given.

Temporal Evolution of a Chronic Expanding Organizing Hematoma on MRI, Including Functional MR Imaging Techniques: a Case Report

Temporal Evolution of a Chronic Expanding Organizing Hematoma on MRI, Including Functional MR Imaging Techniques: a Case Report

Functional MR imaging in gynecologic malignancies: current status and future perspectives.

Using functional MR imaging techniques, we can approach the functional assessment of gynecologic malignancies. Among them, diffusion-weighted imaging (DWI) and dynamic contrast-enhanced MR imaging (DCE-MRI) are two important techniques. This article provides an overview of functional MR imaging techniques, focusing DWI and DCE-MRI on clinical application in gynecologic malignancies. Functional MR imaging techniques play an important role in detection, characterization, staging, treatment response, and outcome prediction, as well as providing conventional morphologic imaging. Familiarity with the characteristics and imaging features of functional MR imaging in gynecologic malignancies will facilitate prompt and accurate diagnosis and treatment.

Staging and follow-up of high-grade malignant salivary gland tumours: The role of traditional versus functional imaging approaches – A review

Following up on the Consensus Conference on high-grade malignant salivary gland tumours (HGMSGT) in adult patients in Brescia, Italia, in October 2014, we review the current imaging modalities for diagnosing and staging these rare tumours. The advantages of functional MR imaging techniques such as diffusion weighted imaging (DWI) and dynamic contrast-enhanced MR imaging (DCEMRI) in comparison with traditional MRI will be outlined. The limited role of (18)FDG-PET CT and fMRI will be addressed. Finally, in view of new experimental treatment options, we will discuss the role of imaging during follow-up.

Imagerie du cancer de la prostate : IRM et imagerie nucléaire

Multiparametric magnetic resonance imaging (mp-MRI) and Tomography with Emission of Positons are increasingly used in prostate cancer. A systematic review of the scientific literature was performed in the Medline database (PubMed), using different associations of the following keywords: MRI, PET MRI, prostate cancer. Accuracy in the detection of prostate cancer is improved by the combined use of standard T2-weighted MR imaging and advanced functional MR imaging techniques such as diffusion-weighted imaging and dynamic contrast-enhanced imaging. Multiparametric MR imaging provides the highest accuracy in detection, localization, and staging of prostate cancer. This accurate assessment is a prerequisite for optimal clinical management and therapy selection. Another recent advancement in the field is MR imaging guidance for targeted prostate biopsy, which is an alternative to the current standard of transrectal ultrasonography-guided systematic biopsy. Prostate MRI plays also an important role in tumor detection when there is clinical or biochemical suspicion of residual or recurrent disease after treatment. The emergence of new technologies such as Tomography with Emission of Positons (TEP) after injection of 18F-choline, allows to improve the staging of prostate cancer (nodes status, sentinel node and occult metastases) and thus to change the management, especially when relapse. The first results with modern imaging are already very promising, and numerous prospects are expected, either by improving technologies (parametric fusion of PET and MRI) or the appearance of new tracers more sensitive and more specific than the choline. Bone scan still retains an important place especially since its realization is now coupled with a tomographic study merged with a low dose scanner, thereby remarkably improving its diagnostic performance.

“Cystic”‐appearing soft tissue masses: What is the role of anatomic, functional, and metabolic MR imaging techniques in their characterization?

Although conventional MR imaging with contrast-enhanced T1-weighted sequences is of paramount importance for evaluating soft tissue masses, noncontrast MR sequences have emerged that facilitate their characterization. In this article, the utility and pitfalls of conventional MR imaging with T1-weighted, fluid-sensitive, and contrast-enhanced sequences will be discussed, along with that of functional (diffusion weighted imaging) and metabolic (proton MR spectroscopy) non-contrast-enhanced techniques for the purpose of soft tissue mass characterization. In particular, we discuss the application of these techniques to differentiating neoplastic or inflammatory masses that have high fluid content from benign cysts, as this distinction is a common pitfall of conventional sequences.

Plasticity of the Injured Human Spinal Cord: Insights Revealed by Spinal Cord Functional MRI

IntroductionWhile numerous studies have documented evidence for plasticity of the human brain there is little evidence that the human spinal cord can change after injury. Here, we employ a novel spinal fMRI design where we stimulate normal and abnormal sensory dermatomes in persons with traumatic spinal cord injury and perform a connectivity analysis to understand how spinal networks process information.MethodsSpinal fMRI data was collected at 3 Tesla at two institutions from 38 individuals using the standard SEEP functional MR imaging techniques. Thermal stimulation was applied to four dermatomes in an interleaved timing pattern during each fMRI acquisition. SCI patients were stimulated in dermatomes both above (normal sensation) and below the level of their injury. Sub-group analysis was performed on healthy controls (n = 20), complete SCI (n = 3), incomplete SCI (n = 9) and SCI patients who recovered full function (n = 6).ResultsPatients with chronic incomplete SCI, when stimulated in a dermatome of normal sensation, showed an increased number of active voxels relative to controls (p = 0.025). There was an inverse relationship between the degree of sensory impairment and the number of active voxels in the region of the spinal cord corresponding to that dermatome of abnormal sensation (R2 = 0.93, p<0.001). Lastly, a connectivity analysis demonstrated a significantly increased number of intraspinal connections in incomplete SCI patients relative to controls suggesting altered processing of afferent sensory signals.ConclusionsIn this work we demonstrate the use of spinal fMRI to investigate changes in spinal processing of somatosensory information in the human spinal cord. We provide evidence for plasticity of the human spinal cord after traumatic injury based on an increase in the average number of active voxels in dermatomes of normal sensation in chronic SCI patients and an increased number of intraspinal connections in incomplete SCI patients relative to healthy controls.

MR Imaging of Neoplastic Central Nervous System Lesions: Review and Recommendations for Current Practice

MR imaging is the preferred technique for the diagnosis, treatment planning, and monitoring of patients with neoplastic CNS lesions. Conventional MR imaging, with gadolinium-based contrast enhancement, is increasingly combined with advanced, functional MR imaging techniques to offer morphologic, metabolic, and physiologic information. This article provides updated recommendations to neuroradiologists, neuro-oncologists, neurosurgeons, and radiation oncologists on the practical applications of MR imaging of neoplastic CNS lesions in adults, with particular focus on gliomas, based on a review of the clinical trial evidence and personal experiences shared at a recent international meeting of experts in neuroradiology, neuro-oncology, neurosurgery, and radio-oncology.

Functional MR study of hepatic fibrosis

The accurate diagnosis and staging of hepatic fibrosis is crucial for treatment and prognosis of liver disease. The current gold standard is liver biopsy, but it cannot be used in population-based screening, and has well known drawbacks if used for monitoring of disease progression or treatment results. Functional MR, as a non-invasive method, is increasingly used in hepatic fibrosis and became the current hot spot. Most recently available functional MR imaging techniques including diffusion weighted imaging, perfusion weighted imaging and MR spectroscopy can detect cirrhosis or fibrosis reasonably accurately. However, to date only MR elastography has been able to stage fibrosis or diagnose mild disease. MR diffusion weighted appears next most promising.

The role of functional magnetic resonance imaging in brain surgery

New functional neuroimaging techniques are changing our understanding of the human brain, and there is now convincing evidence to move away from the classic and clinical static concepts of functional topography. In a modern neurocognitive view, functions are thought to be represented in dynamic large-scale networks. The authors review the current (limited) role of functional MR imaging in brain surgery and the possibilities of new functional MR imaging techniques for research and neurosurgical practice. A critique of current clinical gold standard techniques (electrocortical stimulation and the Wada test) is given.

MR imaging of the prostate in clinical practice

Magnetic resonance imaging (MRI) is the imaging tool of choice in the evaluation of prostate cancer. The main applications of MR imaging in the management of prostate cancer are: (1) to guide targeted biopsy when prostate cancer is clinically suspected and previous ultrasound-guided biopsy results are negative; (2) to localize and stage prostate cancer and provide a roadmap for treatment planning; and (3) to detect residual or locally recurrent cancer after treatment. Other MR techniques such as proton MR spectroscopic imaging (MRSI), diffusion-weighted imaging (DWI), and contrast-enhanced MRI (CE-MRI) complement conventional MR imaging by providing metabolic and functional information that can improve the accuracy of prostate cancer detection and characterization. In everyday clinical practice, and to account for patient comfort, MR imaging studies are limited to 1 h. To obtain consistently high-quality images, a well-designed protocol is necessary. Routine MR imaging can be supplemented by other MR techniques such as MRSI, DWI or CE-MRI depending on the expertise available and the clinical questions that need to be answered. This review summarizes the role of MR imaging in the management of prostate cancer and describes practical approaches to implementing anatomic, metabolic and functional MR imaging techniques in the clinic.

Protocol design for high relaxivity contrast agents in MR imaging of the CNS

Numerous experimental and clinical studies have shown that the use of the high relaxivity MR contrast agent MultiHance (gadobenate dimeglumine, Gd-BOPTA; Bracco Imaging, Milan, Italy) results in improved detection, delineation and enhancement of CNS tumors compared to other available gadolinium agents. This leads not only to more confident diagnoses, but also to a substantially improved differential diagnostic process. The higher R1 and R2 relaxivities of MultiHance, deriving from the weak and transient interaction of the Gd-BOPTA contrast-effective moiety of this agent with serum albumin, help also to further optimize functional MR imaging techniques such as perfusion MRI and dynamic MR angiography. However, because the interaction between the Gd-BOPTA chelate and serum albumin affects proton relaxation times, imaging parameters need to be adapted to achieve maximum benefit from the high relaxivity of MultiHance at different magnetic field strengths. In this article we review the unique MR imaging properties of MultiHance for the assessment of brain tumors and other cerebral pathologies, and give practical information on how best to optimize MR sequence parameters to achieve the optimal contrast between normal CNS tissue and lesion.

The use of subdural grids in the management of focal malformations due to abnormal cortical development

Because of the spatial limitations of scalp electroencephalographic recordings and the lack of reproducible results using functional MR imaging techniques to map various eloquent areas of the cortex, the accurate mapping of the extent of epileptogenicity and function currently are best accomplished through invasive electrocorticographic recordings and direct cortical stimulation, respectively. The purpose of this article is to give an overview of the presurgical diagnostic tools used in patients with suspected malformations caused by abnormalities of cortical development with special emphasis on subdural electrodes. The indications and the role of invasive subdural electrode evaluation are discussed.

Functional magnetic resonance (fMR) imaging of a rat brain tumor model: implications for evaluation of tumor microvasculature and therapeutic response

Functional MR (fMR) imaging techniques based on blood oxygenation level dependent (BOLD) effects were developed and applied to a rat brain tumor model to evaluate the potential utility of the method for characterizing tumor growth and regression following treatment. Rats bearing 9L brain tumors in situ were imaged during inhalation of room air and after administration of 100% oxygen + acetazolamide (ACZ) injected 15 mg/kg intravenously. Pixel-to-pixel fMR maps of normalized signal intensity change from baseline values were calculated from T 2 weighted spin echo (SE) images acquired pre- and post- oxygen + ACZ administration. Resultant fMR maps were then compared to gross histological sections obtained from corresponding anatomical regions. Regions containing viable tumor with increased cellular density and localized foci of necrotic tumor cells consistent with hypoxia were visualized in the fMR images as regions with decreased signal intensities, indicating diminished oxyhemoglobin concentration and blood flow as compared to normal brain. Histological regions having peritumor edema, caused by increased permeability of tumor vasculature, were visualized in the fMR images as areas with markedly increased signal intensities. These results suggest that fMR imaging techniques could be further developed for use as a non-invasive tool to assess changes in tumor oxygenation/hemodynamics, and to evaluate the pharmacologic effect of anti-neoplastic drugs.

CORTICAL ACTIVATION MR STUDIES IN BRAIN DISORDERS

Principles and clinical applications of functional MR imaging activation studies are presented. The physical and physiologic basis for cerebral blood volume-, cerebral blood flow-, and oxygenation-based functional MR imaging techniques are reviewed. The methodology of blood oxygen level dependent (BOLD) functional MR imaging is emphasized. Applications to presurgical mapping of sensorimotor and language function in patients with vascular malformations, tumors, and other lesions near critical cortical areas are illustrated. Important new applications to neuropsychiatric diseases are highlighted.

FUNCTIONAL MR IMAGING IN PATIENTS WITH EPILEPSY

Recent advances in MR imaging have significantly enhanced the diagnosis and management of epilepsy. This article focuses on the expanding role of functional MR imaging in our imaging armamentarium. Diffusion, perfusion, and BOLD functional MR imaging techniques are discussed in detail with emphasis on epilepsy applications. Functional MR imaging seizure focus localization, eloquent cortex mapping, and the potential for functional MR imaging to replace Wada testing are explored. With anticipated future developments, functional MR imaging holds great promise for epilepsy patients.

Cocaine‐induced changes in time course of regional cerebral blood volume and transit time as determined by dynamic MR imaging

We examined cocaine-mediated change in regional cerebral blood volume (rCBV) and mean transit time (MTT) in central brain structures of rats using functional MR imaging techniques. Changes in MTT and rCBV in animals who had previously been given cocaine depended on the length of time between the last pretreatment injection and the acute injection and seemed to parallel cocaine-mediated changes in extracellular dopamine concentrations.