Magnetic Resonance Imaging (MRI) is among the most important medical imaging techniques available today. There is an installed base of approximately 15,000 MRI scanners worldwide. Each of these ...scanners is capable of running many different "pulse sequences", which are governed by physics and engineering principles, and implemented by software programs that control the MRI hardware. To utilize an MRI scanner to the fullest extent, a conceptual understanding of its pulse sequences is crucial. This book offers a complete guide that can help the scientists, engineers, clinicians, and technologists in the field of MRI understand and better employ their scanner.
·Explains pulse sequences, their components, and the associated image reconstruction methods commonly used in MRI·Provides self-contained sections for individual techniques·Can be used as a quick reference guide or as a resource for deeper study·Includes both non-mathematical and mathematical descriptions ·Contains numerous figures, tables, references, and worked example problems
The origin of modern science is often located in Europe and the West. This Euro/West-centrism relegates emergent practices elsewhere to the periphery, undergirding analyses of contemporary ...transnational science and technology with traditional but now untenable hierarchical categories. In this book, Amit Prasad examines features of transnationality in science and technology through a study of MRI research and development in the United States, Britain, and India. In an analysis that is both theoretically nuanced and empirically robust, Prasad unravels the entangled genealogies of MRI research, practice, and culture in these three countries. Prasad follows sociotechnical trails in relation to five aspects of MRI research: invention, industrial development, market, history, and culture. He first examines the well-known dispute between American scientists Paul Lauterbur and Raymond Damadian over the invention of MRI, then describes the post-invention emergence of the technology, as the center of MRI research shifted from Britain to the U.S; the marketing of the MRI and the transformation of MRI research into a corporate-powered "Big Science"; and MRI research in India, beginning with work in India's nuclear magnetic resonance (NMR) laboratories in the 1940s. Finally, he explores the different dominant technocultures in each of the three countries, analyzing scientific cultures as shifting products of transnational histories rather than static products of national scientific identities and cultures. Prasad's analysis offers not only an innovative contribution to current debates within science and technology studies but also an original postcolonial perspective on the history of cutting-edge medical technology.
Over the past decade, updated definitions for the different stages of prostate cancer and risk for distant disease, along with the advent of new therapies, have remarkably changed the management of ...patients. The two expectations from imaging are accurate staging and appropriate assessment of disease response to therapies. Modern, next‐generation imaging (NGI) modalities, including whole‐body magnetic resonance imaging (WB‐MRI) and nuclear medicine (most often prostate‐specific membrane antigen PSMA positron emission tomography PET/computed tomography CT) bring added value to these imaging tasks. WB‐MRI has proven its superiority over bone scintigraphy (BS) and CT for the detection of distant metastasis, also providing reliable evaluations of disease response to treatment. Comparison of the effectiveness of WB‐MRI and molecular nuclear imaging techniques with regard to indications and the definition of their respective/complementary roles in clinical practice is ongoing. This paper illustrates the evolution of WB‐MRI imaging protocols, defines the current state‐of‐the art, and highlights the latest developments and future challenges. The paper presents and discusses WB‐MRI indications in the care pathway of men with prostate cancer in specific key situations: response assessment of metastatic disease, “all in one” cancer staging, and oligometastatic disease.
Abstract Background Increasing evidence supports the use of magnetic resonance imaging (MRI)-ultrasound fusion–targeted prostate biopsy (MRF-TB) to improve the detection of clinically significant ...prostate cancer (PCa) while limiting detection of indolent disease compared to systematic 12-core biopsy (SB). Objective To compare MRF-TB and SB results and investigate the relationship between biopsy outcomes and prebiopsy MRI. Design, setting, and participants Retrospective analysis of a prospectively acquired cohort of men presenting for prostate biopsy over a 26-mo period. A total of 601 of 803 consecutively eligible men were included. Interventions All men were offered prebiopsy MRI and assigned a maximum MRI suspicion score (mSS). Men with an MRI abnormality underwent combined MRF-TB and SB. Outcomes Detection rates for all PCa and high-grade PCa (Gleason score GS ≥7) were compared using the McNemar test. Results and limitations MRF-TB detected fewer GS 6 PCas (75 vs 121; p < 0.001) and more GS ≥7 PCas (158 vs 117; p < 0.001) than SB. Higher mSS was associated with higher detection of GS ≥7 PCa ( p < 0.001) but was not correlated with detection of GS 6 PCa. Prediction of GS ≥7 disease by mSS varied according to biopsy history. Compared to SB, MRF-TB identified more GS ≥7 PCas in men with no prior biopsy (88 vs 72; p = 0.012), in men with a prior negative biopsy (28 vs 16; p = 0.010), and in men with a prior cancer diagnosis (42 vs 29; p = 0.043). MRF-TB detected fewer GS 6 PCas in men with no prior biopsy (32 vs 60; p < 0.001) and men with prior cancer (30 vs 46; p = 0.034). Limitations include the retrospective design and the potential for selection bias given a referral population. Conclusions MRF-TB detects more high-grade PCas than SB while limiting detection of GS 6 PCa in men presenting for prostate biopsy. These findings suggest that prebiopsy multiparametric MRI and MRF-TB should be considered for all men undergoing prostate biopsy. In addition, mSS in conjunction with biopsy indications may ultimately help in identifying men at low risk of high-grade cancer for whom prostate biopsy may not be warranted. Patient summary We examined how magnetic resonance imaging (MRI)-targeted prostate biopsy compares to traditional systematic biopsy in detecting prostate cancer among men with suspicion of prostate cancer. We found that MRI-targeted biopsy detected more high-grade cancers than systematic biopsy, and that MRI performed before biopsy can predict the risk of high-grade cancer.
If magnetic resonance imaging (MRI) is to compete with computed tomography for evaluation of patients with acute ischemic stroke, there is a need for further improvements in acquisition speed.
...Inclusion criteria for this prospective, single institutional study were symptoms of acute ischemic stroke within 24 hours onset, National Institutes of Health Stroke Scale ≥3, and absence of MRI contraindications. A combination of echo-planar imaging (EPI) and a parallel acquisition technique were used on a 3T magnetic resonance (MR) scanner to accelerate the acquisition time. Image analysis was performed independently by 2 neuroradiologists.
A total of 62 patients met inclusion criteria. A repeat MRI scan was performed in 22 patients resulting in a total of 84 MRIs available for analysis. Diagnostic image quality was achieved in 100% of diffusion-weighted imaging, 100% EPI-fluid attenuation inversion recovery imaging, 98% EPI-gradient recalled echo, 90% neck MR angiography and 96% of brain MR angiography, and 94% of dynamic susceptibility contrast perfusion scans with interobserver agreements (k) ranging from 0.64 to 0.84. Fifty-nine patients (95%) had acute infarction. There was good interobserver agreement for EPI-fluid attenuation inversion recovery imaging findings (k=0.78; 95% confidence interval, 0.66-0.87) and for detection of mismatch classification using dynamic susceptibility contrast-Tmax (k=0.92; 95% confidence interval, 0.87-0.94). Thirteen acute intracranial hemorrhages were detected on EPI-gradient recalled echo by both observers. A total of 68 and 72 segmental arterial stenoses were detected on contrast-enhanced MR angiography of the neck and brain with k=0.93, 95% confidence interval, 0.84 to 0.96 and 0.87, 95% confidence interval, 0.80 to 0.90, respectively.
A 6-minute multimodal MR protocol with good diagnostic quality is feasible for the evaluation of patients with acute ischemic stroke and can result in significant reduction in scan time rivaling that of the multimodal computed tomographic protocol.
Abstract Background A significant proportion of prostate cancers (PCas) are missed by conventional transrectal ultrasound-guided biopsy (TRUS-GB). It remains unclear whether the combined approach ...using targeted magnetic resonance imaging (MRI)-ultrasound fusion–guided biopsy (FUS-GB) and systematic TRUS-GB is superior to targeted MRI-guided in-bore biopsy (IB-GB) for PCa detection. Objective To compare PCa detection between IB-GB alone and FUS-GB + TRUS-GB in patients with at least one negative TRUS-GB and prostate-specific antigen ≥4 ng/ml. Design, setting, and participants Patients were prospectively randomized after multiparametric prostate MRI to IB-GB (arm A) or FUS-GB + TRUS-GB (arm B) from November 2011 to July 2014. Outcome measurements and statistical analysis The study was powered at 80% to demonstrate an overall PCa detection rate of ≥60% in arm B compared to 40% in arm A. Secondary endpoints were the distribution of highest Gleason scores, the rate of detection of significant PCa (Gleason ≥7), the number of biopsy cores to detect one (significant) PCa, the positivity rate for biopsy cores, and tumor involvement per biopsy core. Results and limitations The study was halted after interim analysis because the primary endpoint was not met. The trial enrolled 267 patients, of whom 210 were analyzed (106 randomized to arm A and 104 to arm B). PCa detection was 37% in arm A and 39% in arm B (95% confidence interval for difference, –16% to 11%; p = 0.7). Detection rates for significant PCa (29% vs 32%; p = 0.7) and the highest percentage tumor involvement per biopsy core (48% vs 42%; p = 0.4) were similar between the arms. The mean number of cores was 5.6 versus 17 ( p < 0.001). A limitation is the limited number of patients because of early cessation of accrual. Conclusions This trial failed to identify an important improvement in detection rate for the combined biopsy approach over MRI-targeted biopsy alone. A prospective comparison between MRI-targeted biopsy alone and systematic TRUS-GB is justified. Patient summary Our randomized study showed similar prostate cancer detection rates between targeted prostate biopsy guided by magnetic resonance imaging and the combination of targeted biopsy and systematic transrectal ultrasound-guided prostate biopsy. An important improvement in detection rates using the combined biopsy approach can be excluded.
.2661 Preamble This document was developed by the American College of Cardiology Foundation (ACCF) Task Force on Clinical Expert Consensus Documents (ECDs) and cosponsored by the American College of ...Radiology (ACR), American Heart Association (AHA), North American Society for Cardiovascular Imaging (NASCI), and the Society for Cardiovascular Magnetic Resonance (SCMR), to provide a perspective on the current state of cardiovascular magnetic resonance (CMR). Often the topic is the subject of ongoing investigation. ...the reader should view the ECD as the best attempt of the ACCF and document cosponsors to inform and guide clinical practice in areas where rigorous evidence may not be available or the evidence to date is not widely accepted. ...some topics covered by ECDs will be addressed subsequently by the ACCF/AHA Practice Guidelines Committee. Peer Reviewer Representation Consultant Speaker Ownership/Partnership/Principal Research Institutional, Organizational, or Other Financial Benefit Expert Witness Dr. James C. Carr Official Reviewer--North American Society for Cardiovascular Imaging None None None None None None Dr. Michael G. Del Core Official Reviewer--ACCF Board of Governors None None None None None None Dr. Andre Duerinckx Official Reviewer--American College of Radiology None None None Philips Medical Systems Schering-Plough None None Dr. Mark J. Eisenberg Official Reviewer--ACCF Task Force on Clinical Expert Consensus Documents None None None None None None Dr. Victor A. Ferrari Official Reviewer-- Society for Cardiovascular Magnetic Resonance Imaging None None None None None None Dr. Gautham Reddy Official Reviewer--American College of Radiology None None None None None None Dr. Orlando Simonetti Official Reviewer--North American Society for Cardiovascular Imaging None None * Siemens Healthcare None None None Dr. James E. Udelson Official Reviewer--ACCF Board of Trustees; American Heart Association None None None None None None Dr. Sanjay Kaul Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents None None None None None None Dr. Debabrata Mukherjee Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents None None None None None None Dr. Robert S. Rosenson Content Reviewer--ACCF Task Force on Clinical Expert Consensus Documents Abbott Anthera AstraZeneca* Daiichi Sankyo LipoScience* Roche None LipoScience* None Grain Board None Dr. Jonathan W. Weinsaft Content Reviewer--*Individual None None None Lantheus Medical Imaging None None * This table represents the relevant relationships with industry and other entities that were disclosed by reviewers at the time of peer review. A person is deemed to have a significant interest in a business if the interest represents ownership of 5% or more of the voting stock or share of the business entity, or ownership of $10 000 or more of the fair market value of the business entity; or if funds received by the person from the business entity exceed 5% of the person's gross income for the previous year.
With the proliferation of multi-site neuroimaging studies, there is a greater need for handling non-biological variance introduced by differences in MRI scanners and acquisition protocols. Such ...unwanted sources of variation, which we refer to as “scanner effects”, can hinder the detection of imaging features associated with clinical covariates of interest and cause spurious findings. In this paper, we investigate scanner effects in two large multi-site studies on cortical thickness measurements across a total of 11 scanners. We propose a set of tools for visualizing and identifying scanner effects that are generalizable to other modalities. We then propose to use ComBat, a technique adopted from the genomics literature and recently applied to diffusion tensor imaging data, to combine and harmonize cortical thickness values across scanners. We show that ComBat removes unwanted sources of scan variability while simultaneously increasing the power and reproducibility of subsequent statistical analyses. We also show that ComBat is useful for combining imaging data with the goal of studying life-span trajectories in the brain.
•Cortical thickness (CT) measurements are highly scanner specific.•Identifying scanner effects is crucial for inference and biomarker development.•We propose to use ComBat to harmonize cortical thickness values across scanners.
Vibration-controlled transient elastography (VCTE), point shear wave elastography (pSWE), 2-dimensional shear wave elastography (2DSWE), magnetic resonance elastography (MRE), and magnetic resonance ...imaging (MRI) have been proposed as non-invasive tests for patients with non-alcoholic fatty liver disease (NAFLD). This study evaluated their diagnostic accuracy for liver fibrosis and non-alcoholic steatohepatitis (NASH).
PubMED/MEDLINE, EMBASE and the Cochrane Library were searched for studies examining the diagnostic accuracy of these index tests, against histology as the reference standard, in adult patients with NAFLD. Two authors independently screened and assessed methodological quality of studies and extracted data. Summary estimates of sensitivity, specificity and area under the curve (sAUC) were calculated for fibrosis stages and NASH, using a random effects bivariate logit-normal model.
We included 82 studies (14,609 patients). Meta-analysis for diagnosing fibrosis stages was possible in 53 VCTE, 11 MRE, 12 pSWE and 4 2DSWE studies, and for diagnosing NASH in 4 MRE studies. sAUC for diagnosis of significant fibrosis were: 0.83 for VCTE, 0.91 for MRE, 0.86 for pSWE and 0.75 for 2DSWE. sAUC for diagnosis of advanced fibrosis were: 0.85 for VCTE, 0.92 for MRE, 0.89 for pSWE and 0.72 for 2DSWE. sAUC for diagnosis of cirrhosis were: 0.89 for VCTE, 0.90 for MRE, 0.90 for pSWE and 0.88 for 2DSWE. MRE had sAUC of 0.83 for diagnosis of NASH. Three (4%) studies reported intention-to-diagnose analyses and 15 (18%) studies reported diagnostic accuracy against pre-specified cut-offs.
When elastography index tests are acquired successfully, they have acceptable diagnostic accuracy for advanced fibrosis and cirrhosis. The potential clinical impact of these index tests cannot be assessed fully as intention-to-diagnose analyses and validation of pre-specified thresholds are lacking.
Non-invasive tests that measure liver stiffness or use magnetic resonance imaging (MRI) have been suggested as alternatives to liver biopsy for assessing the severity of liver scarring (fibrosis) and fatty inflammation (steatohepatitis) in patients with non-alcoholic fatty liver disease (NAFLD). In this study, we summarise the results of previously published studies on how accurately these non-invasive tests can diagnose liver fibrosis and inflammation, using liver biopsy as the reference. We found that some techniques that measure liver stiffness had a good performance for the diagnosis of severe liver scarring.
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•This is the largest systematic review of imaging/elastography biomarkers in NAFLD.•Meta-analysis of 1 MR elastography and 3 ultrasound techniques.•Elastography may help in fibrosis evaluation in those with NAFLD and valid readings.•Clinical utility of these tests cannot be assessed fully as intention-to-diagnose analyses and validation of pre-specified cut-offs are lacking.
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