Magnetic resonance (MR) acquisitions of the torso are frequently affected by respiratory motion with detrimental effects on signal quality. The motion of organs inside the body is typically decoupled ...from surface motion and is best captured using rapid MR imaging (MRI). We propose a pipeline for prospective motion correction of the target organ using MR image navigators providing absolute motion estimates in millimeters. Our method is designed to feature multi-nuclear interleaving for non-proton MR acquisitions and to tolerate local transmit coils with inhomogeneous field and sensitivity distributions. OpenCV object tracking was introduced for rapid estimation of in-plane displacements in 2D MR images. A full three-dimensional translation vector was derived by combining displacements from slices of multiple and arbitrary orientations. The pipeline was implemented on 3 T and 7 T MR scanners and tested in phantoms and volunteers. Fast motion handling was achieved with low-resolution 2D MR image navigators and direct implementation of OpenCV into the MR scanner's reconstruction pipeline. Motion-phantom measurements demonstrate high tracking precision and accuracy with minor processing latency. The feasibility of the pipeline for reliable in-vivo motion extraction was shown on heart and kidney data. Organ motion was manually assessed by independent operators to quantify tracking performance. Object tracking performed convincingly on 7774 navigator images from phantom scans and different organs in volunteers. In particular the kernelized correlation filter (KCF) achieved similar accuracy (74%) as scored from inter-operator comparison (82%) while processing at a rate of over 100 frames per second. We conclude that fast 2D MR navigator images and computer vision object tracking can be used for accurate and rapid prospective motion correction. This and the modular structure of the pipeline allows for the proposed method to be used in imaging of moving organs and in challenging applications like cardiac magnetic resonance spectroscopy (MRS) or magnetic resonance imaging (MRI) guided radiotherapy.
Functional renal magnetic resonance imaging (MRI) has seen a number of recent advances, and techniques are now available that can generate quantitative imaging biomarkers with the potential to ...improve the management of kidney disease. Such biomarkers are sensitive to changes in renal blood flow, tissue perfusion, oxygenation and microstructure (including inflammation and fibrosis), processes that are important in a range of renal diseases including chronic kidney disease. However, several challenges remain to move these techniques towards clinical adoption, from technical validation through biological and clinical validation, to demonstration of cost-effectiveness and regulatory qualification. To address these challenges, the European Cooperation in Science and Technology Action PARENCHIMA was initiated in early 2017. PARENCHIMA is a multidisciplinary pan-European network with an overarching aim of eliminating the main barriers to the broader evaluation, commercial exploitation and clinical use of renal MRI biomarkers. This position paper lays out PARENCHIMA's vision on key clinical questions that MRI must address to become more widely used in patients with kidney disease, first within research settings and ultimately in clinical practice. We then present a series of practical recommendations to accelerate the study and translation of these techniques.
Liver cancer is the sixth most commonly occurring cancer globally, and the main histological type is hepatocellular carcinoma. This type of neoplasia has a poor prognosis due to a high rate of ...recurrence and intrahepatic metastasis, which are closely are closely associated with the angiogenic process. Vascular endothelial growth factor (VEGF), which is under the control of hypoxia inducible factor-1α (HIF-1α), stimulates the proliferation of endothelial cells and increases cell permeability, promoting the growth, spread and metastasis of tumors. Melatonin, the main hormone secreted by the pineal gland, may have a significant role in tumor suppression and has demonstrated antiangiogenic and antimetastatic effects. The aim of the present study was to analyze the cell viability, migration and invasion, as well as the expression of proangiogenic proteins VEGF and HIF-1α, in HepG2 hepatocarcinoma cells, following treatment with melatonin. Cells were cultured and cell viability was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The expression of proangiogenic proteins VEGF and HIF-1α, under conditions of normoxia and hypoxia, was verified using immunocytochemistry and quantified by densitometry. The analysis of the processes of cell migration and invasion was performed in a Boyden chamber. The MTT assay revealed a reduction in cell viability (P=0.018) following treatment with 1 mM melatonin for 24 h. The expression of proangiogenic proteins VEGF and HIF-1α was reduced in cells treated with 1 mM melatonin for 24 h in normoxic (P<0.001) and hypoxic (P<0.001) conditions, compared with the control group and with induced hypoxia alone. The rate of cell migration and invasion was additionally reduced in cells treated with 1 mM melatonin for 48 h when compared with the control group (P=0.496). The results of the present study suggest that melatonin may have an antiproliferative, antiangiogenic and antimetastatic role in hepatocarcinoma cells and may present a novel therapeutic option for the treatment of liver cancer.
Magnetic resonance elastography (MRE) is a non-invasive method to quantify biomechanical properties of human tissues. It has potential in diagnosis and monitoring of kidney disease, if established in ...clinical practice. The interplay of flow and volume changes in renal vessels, tubule, urinary collection system and interstitium is complex, but physiological ranges of
viscoelastic properties during fasting and hydration have never been investigated in all gross anatomical segments simultaneously.
Ten healthy volunteers underwent two imaging sessions, one following a 12-hour fasting period and the second after a drinking challenge of >10 mL per kg body weight (60-75 min before the second examination). High-resolution renal MRE was performed using a novel driver with rotating eccentric mass placed at the posterior-lateral wall to couple waves (50 Hz) to the kidney. The biomechanical parameters, shear wave speed (c
in m/s), storage modulus (G
in kPa), loss modulus (G
in kPa), phase angle
and attenuation (α in 1/mm) were derived. Accurate separation of gross anatomical segments was applied in post-processing (whole kidney, cortex, medulla, sinus, vessel).
High-quality shear waves coupled into all gross anatomical segments of the kidney (mean shear wave displacement: 163 ± 47 μm, mean contamination of second upper harmonics <23%, curl/divergence: 4.3 ± 0.8). Regardless of the hydration state, median G
of the cortex and medulla (0.68 ± 0.11 kPa) was significantly higher than that of the sinus and vessels (0.48 ± 0.06 kPa), and consistently, significant differences were found in c
,
, and G
(all
< 0.001). The viscoelastic parameters of cortex and medulla were not significantly different. After hydration sinus exhibited a small but significant reduction in median G
by -0.02 ± 0.04 kPa (
= 0.01), and, consequently, the cortico-sinusoidal-difference in G
increased by 0.04 ± 0.07 kPa (
= 0.05). Only upon hydration, the attenuation in vessels became lower (0.084 ± 0.013 1/mm) and differed significantly from the whole kidney (0.095 ± 0.007 1/mm,
= 0.01).
High-resolution renal MRE with an innovative driver and well-defined 3D segmentation can resolve all renal segments, especially when including the sinus in the analysis. Even after a prolonged hydration period the approach is sensitive to small hydration-related changes in the sinus and in the cortico-sinusoidal-difference.
Quality assurance (QA) in magnetic resonance imaging (MRI) requires test objects. ‘Phantoms’ provided by MR manufacturers are homogeneously filled spheres or cylinders, and commercially available ...products are often too small for abdominal imaging, particularly for enlarged polycystic kidneys. Here we present the design, manufacturing and testing of a dedicated, yet versatile, abdominal MRI phantom, that can be reproduced with relatively low costs. The phantom mimics a human abdomen in size and shape and comprises seven test fluids, representing various tissue types at 3 T. The conductivity and permittivity of the test fluids match the average abdomen and kidney with a relative permittivity (ε) 65 and 72 as well as conductivity 0.6 and 0.7 S/m, respectively. The T
1
and T
2
relaxation times cover healthy average abdomen and kidney tissue values (T
1(abd)
: 856 ms and T
1(kid)
: 1,106 ms; T
2(abd)
: 52 ms and T
2(kid)
: 67 ms), intermediate (T
1
: 1,183 ms and 1,271 ms; T
2
: 128 and 189 ms), and disease values for (polycystic) kidney (T
1
: 1,428 ms, 1,561 ms and 1763 ms; T
2
: 319 ms, 424 and 647 ms). T
1
and T
2
relaxation times were stable over 73 weeks. Our reasonably priced, durable and reproducible abdominal phantom enables single and multi-center QA for future collaborative studies aiming for various challenges around abdominal and, particularly, kidney imaging.
Background
Phase‐contrast (PC) MRI is a feasible and valid noninvasive technique to measure renal artery blood flow, showing potential to support diagnosis and monitoring of renal diseases. However, ...the variability in measured renal blood flow values across studies is large, most likely due to differences in PC‐MRI acquisition and processing. Standardized acquisition and processing protocols are therefore needed to minimize this variability and maximize the potential of renal PC‐MRI as a clinically useful tool.
Purpose
To build technical recommendations for the acquisition, processing, and analysis of renal 2D PC‐MRI data in human subjects to promote standardization of renal blood flow measurements and facilitate the comparability of results across scanners and in multicenter clinical studies.
Study Type
Systematic consensus process using a modified Delphi method.
Population
Not applicable.
Sequence Field/Strength
Renal fast gradient echo‐based 2D PC‐MRI.
Assessment
An international panel of 27 experts from Europe, the USA, Australia, and Japan with 6 (interquartile range 4–10) years of experience in 2D PC‐MRI formulated consensus statements on renal 2D PC‐MRI in two rounds of surveys. Starting from a recently published systematic review article, literature‐based and data‐driven statements regarding patient preparation, hardware, acquisition protocol, analysis steps, and data reporting were formulated.
Statistical Tests
Consensus was defined as ≥75% unanimity in response, and a clear preference was defined as 60–74% agreement among the experts.
Results
Among 60 statements, 57 (95%) achieved consensus after the second‐round survey, while the remaining three showed a clear preference. Consensus statements resulted in specific recommendations for subject preparation, 2D renal PC‐MRI data acquisition, processing, and reporting.
Data Conclusion
These recommendations might promote a widespread adoption of renal PC‐MRI, and may help foster the set‐up of multicenter studies aimed at defining reference values and building larger and more definitive evidence, and will facilitate clinical translation of PC‐MRI.
Level of Evidence
1
Technical Efficacy Stage
1
To develop technical recommendations on the acquisition and post-processing of renal longitudinal (T1) and transverse (T2) relaxation time mapping. A multidisciplinary panel consisting of 18 experts ...in the field of renal T1 and T2 mapping participated in a consensus project, which was initiated by the European Cooperation in Science and Technology Action PARENCHIMA CA16103. Consensus recommendations were formulated using a two-step modified Delphi method. The first survey consisted of 56 items on T1 mapping, of which 4 reached the pre-defined consensus threshold of 75% or higher. The second survey was expanded to include both T1 and T2 mapping, and consisted of 54 items of which 32 reached consensus. Recommendations based were formulated on hardware, patient preparation, acquisition, analysis and reporting. Consensus-based technical recommendations for renal T1 and T2 mapping were formulated. However, there was considerable lack of consensus for renal T1 and particularly renal T2 mapping, to some extent surprising considering the long history of relaxometry in MRI, highlighting key knowledge gaps that require further work. This paper should be regarded as a first step in a long-term evidence-based iterative process towards ever increasing harmonization of scan protocols across sites, to ultimately facilitate clinical implementation.
This systematic review, initiated by the European Cooperation in Science and Technology Action Magnetic Resonance Imaging Biomarkers for Chronic Kidney Disease (PARENCHIMA), focuses on potential ...clinical applications of magnetic resonance imaging in renal non-tumour disease using magnetic resonance relaxometry (MRR), specifically, the measurement of the independent quantitative magnetic resonance relaxation times T1 and T2 at 1.5 and 3Tesla (T), respectively. Healthy subjects show a distinguishable cortico-medullary differentiation (CMD) in T1 and a slight CMD in T2. Increased cortical T1 values, that is, reduced T1 CMD, were reported in acute allograft rejection (AAR) and diminished T1 CMD in chronic allograft rejection. However, ambiguous findings were reported and AAR could not be sufficiently differentiated from acute tubular necrosis and cyclosporine nephrotoxicity. Despite this, one recent quantitative study showed in renal transplants a direct correlation between fibrosis and T1 CMD. Additionally, various renal diseases, including renal transplants, showed a moderate to strong correlation between T1 CMD and renal function. Recent T2 studies observed increased values in renal transplants compared with healthy subjects and in early-stage autosomal dominant polycystic kidney disease (ADPKD), which could improve diagnosis and progression assessment compared with total kidney volume alone in early-stage ADPKD. Renal MRR is suggested to be sensitive to renal perfusion, ischaemia/oxygenation, oedema, fibrosis, hydration and comorbidities, which reduce specificity. Due to the lack of standardization in patient preparation, acquisition protocols and adequate patient selection, no widely accepted reference values are currently available. Therefore this review encourages efforts to optimize and standardize (multi-parametric) protocols to increase specificity and to tap the full potential of renal MRR in future research.
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