Magnetic Resonance Imaging R2 Research Articles

Iron deposition in ovarian endometriosis evaluated by magnetic resonance imaging R2* correlates with ovarian function

Research questionDoes iron overload in patients with endometriosis affect ovarian function? Can a method be developed to visually reflect this? DesignMagnetic resonance imaging (MRI) R2* was used to evaluate the correlation between iron deposition of ovarian and anti-Müllerian hormone (AMH) in patients with endometriosis. All patients underwent T2* MRI scanning. Serum AMH levels were measured preoperatively. The area of focal iron deposition, iron content of the cystic fluid and AMH levels between the endometriosis and control groups were compared using non-parametric tests. The effects of iron overload on AMH secretion in mouse ovarian granulosa cells were investigated by adding different concentrations of ferric citrate to the medium. ResultsA significant difference was found between endometriosis and control groups in area of iron deposition (P < 0.0001), cystic fluid iron content (P < 0.0001), R2* of lesions (P < 0.0001) and R2* of the cystic fluid (P < 0.0001). Negative correlations were found between serum AMH levels and R2* of cystic lesions in patients with endometriosis aged 18–35 years (rs = –0.6484, P < 0.0001), and between serum AMH levels and R2* of cystic fluid (rs = –0.5074, P = 0.0050). Transcription level (P < 0.0005) and secretion level (P < 0.005) of AMH significantly decreased with the increase in iron exposure. ConclusionIron deposits can impair ovarian function, which is reflected in MRI R2*. Serum AMH levels and R2* of cystic lesions or fluid in patients aged 18–35 years had a negative correlation with endometriosis. R2* can be used to reflect the changes of ovarian function caused by iron deposition.

MAGNETIC RESONANCE IMAGING R2* AS A METHOD TO MONITOR IRON OVERLOAD IN PATIENTS UNDERGOING THERAPEUTIC PHLEBOTOMY FOR HEREDITARY HEMOCHROMATOSIS

: to determine if there was a reduction in liver iron overload due to therapeutic phlebotomy as a treatment for iron overload in patients with hereditary hemochromatosis. : Through a retrospective observational study, we analyzed Magnetic Resonance imaging (MRI) R2* of 5 patients, before and after phlebotomy treatment, who are in medical follow-up for hereditary hemochromatosis. Data were collected from a hospital database and included patients with the diagnosis of hereditary hemochromatosis, with two MRI R2* (one before and one after treatment with phlebotomy), and with serum ferritin and transferrin saturation (TS) data collected in a period next to each MRI. The mean number of phlebotomies between MRIs was seven for each patient. The mean interval between MRIs was 25.6 months (maximum of 66 and minimum of 12). On the first MRI, four patients presented liver iron overload (80%) and 1 did not (20%); the iron overload was severe in all four patients. On the second MRI, all patients with iron overload in the first showed a large reduction to mild overload in the deposits. The only patient who did not have it continued without an iron deposit in the liver. No patient had pancreatic iron deposits at the first or second MRI. One patient initially presented a splenic deposit (20%), which was not evidenced in the second. One liver (20%) had mild hepatic steatosis at the first MRI, which remained mild at the second. No patient developed steatosis during the study period. The mean serum ferritin on the first MRI period was 521.1 (minimum of 139 and maximum of 1000); over the second MRI, the average was 218.4 (minimum of 83 and maximum of 401). All patients showed a reduction in serum ferritin between images. The average reduction was 46.8% (minimum of 5.0% and maximum of 86.5%). The average TS in the first MRI period was 38.35% (minimum of 23% and maximum of 53%) and in the second, 37.47% (minimum of 25% and maximum of 42%). Three patients (60%) had an increase in TS, despite a decrease in serum ferritin. All patients had values within the normal range for ALT and AST in the study period. : Liver iron overload is one of the most serious complications of hereditary hemochromatosis since it is one of the main iron storage organs and the first one to show iron overload. It mayslowly lead to irreversible hepatic damage, such as cirrhosis, or even hepatocellular carcinoma, in addition to multiple organ complications. Measurement of the liver concentration of iron may guide physicians to have better decisions regarding when to initiate or stop therapeutic phlebotomy as a therapy in hereditary hemochromatosis. MRI R2* can be used for detection and quantification of liver iron content, being proposed as a non-invasive method to guide therapy. However, the exact correlation between liver iron content, number, and interval of phlebotomies prescribed, and laboratory findings are not yet well established. : Periodic phlebotomy demonstrated to be an efficient way to reduce body overload, especially liver deposits, as seen in MRI R2* images. In agreement with the literature, the liver accumulates iron before other abdominal organs, such as the pancreas and spleen. Serum ferritin appears to be a better marker for liver iron overload reduction in patients undergoing phlebotomy for hereditary hemochromatosis than transferrin saturation.

Magnetic resonance imaging R2* sequences can better detect microstructural cartilage changes than T2 mapping in cynomolgus monkeys with limited knee kinematics: preliminary imaging findings

BackgroundThe difference between MRI (Magnetic resonance imaging)-R2* and T2 mapping sequences regarding their superiority in the detection of microstructural cartilage changes in knees with limited ROM (range of motion) was unknown.MethodsTwenty male cynomolgus monkeys (mean age: 10.65 ± 0.97 years) underwent knee ROM evaluations and were divided into three groups: Group A (n = 10), with similar left and right knee ROM; Group B (n = 5), with left knee ROM superior to right; and Group C (n = 5), with left knee ROM inferior to right. Twenty-eight ROIs (regions of interest) in the cartilage of the lateral (L) and medial (M) femoral trochlea (FT), anterior (A)/central (C)/posterior (P) femoral condyle (FC) and tibial plateau (TP) of both knees were identified in each monkey. The corresponding ROI values in R2* and T2 mapping sequences were recorded for analysis. One-way ANOVA, Chi-square tests and Pearson’s correlation analysis were used for statistical analyses.ResultsAmong the total 1120 ROIs, significant differences in R2* values among the three groups existed in two ROIs: cartilage of the right MPTP (F = 5.216, P = 0.017) and left MAFC (F = 4.919, P = 0.021). However, the T2 mapping values of all ROIs were similar among the three groups. Microstructural cartilage changes occurred more frequently in the medial (40 ROIs) than in the lateral (0 ROIs) knee compartment (χ2 = 43.077, P < 0.001). The Group B cartilage R2* value of the right MPTP increased with the difference in bilateral knee ROM (r = 0.913, P = 0.030).ConclusionsIn knees with limited ROM, MRI-R2* sequence is superior to T2 mapping in the detection of microstructural cartilage changes, which the medial knee compartment was more susceptible to. Cartilage R2* values tend to increase with the amount of knee ROM loss.

MO399: Remodel: A Mechanistic Trial Evaluating the Effects of Semaglutide on the Kidneys In People With Type 2 Diabetes and Chronic Kidney Disease

Abstract BACKGROUND AND AIMS Approximately 40% of people with type 2 diabetes (T2D) develop chronic kidney disease (CKD) and, despite current treatment, T2D is the most common cause of progression to kidney failure. This situation underscores the need for additional pharmacotherapeutic options. Analyses of cardiovascular outcomes trials suggest that glucagon-like peptide-1 receptor agonists (GLP-1RAs), such as semaglutide, lower albuminuria and attenuate estimated glomerular filtration rate (eGFR) decline in people with T2D. Previous analyses suggest that GLP-1RAs reduce hypoxia and inflammation and, thereby, have a mode of action on the kidneys that is distinct from other treatments, such as sodium-glucose cotransporter-2 (SGCT-2) inhibitors and renin–angiotensin–aldosterone system (RAAS) blockers. Furthermore, the primary benefit of semaglutide appears to be in people with an eGFR &amp;lt; 60 mL/min/1.73 m2, a group in which there is a significant residual risk of progression and a consequent unmet need for effective treatment. To gain further insights on the kidney-protective mechanism of action of semaglutide, the REMODEL trial is integrating investigative functional kidney magnetic resonance imaging (MRI) and kidney biopsies; recent developments in these techniques permit elucidation of the mechanisms underlying kidney protection with current therapies. Mechanistic findings of the REMODEL trial will complement those of the ongoing FLOW clinical trial, which is designed to evaluate clinical outcomes in people with T2D and CKD treated with once-weekly (OW) subcutaneous semaglutide. METHOD REMODEL (NCT04865770) is a 52-week, multicentre, international clinical trial (Figure 1). Primary endpoints are MRI-based and include change from baseline to week 52 in kidney oxygenation (measured with BOLD MRI R2*), global kidney perfusion (phase-contrast MRI) and kidney inflammation (T1 Mapping MRI). Secondary endpoints evaluated from kidney biopsies in a nested cohort (n ∼ 45) include change from baseline to week 52 in intrarenal mRNA expression, assessed by single-nucleus transcriptomics and glomerular basement membrane width, assessed by morphometry. Other secondary endpoints include the apparent diffusion coefficient (estimating renal fibrosis; evaluated with diffusion-weighted MRI), natriuresis, albumin excretion rate and creatinine clearance. MRI outcomes will also be evaluated at week 4 to identify potential early effects of semaglutide in the kidney. Examples of MRI and kidney biopsy single-cell gene expression profile data from participants with CKD are shown in Figure 2 (data not from REMODEL). Safety will be assessed throughout the trial. RESULTS REMODEL was initiated in April 2021 and is being conducted in Canada, France, Italy, Poland, South Africa, Spain and USA. CONCLUSION REMODEL will investigate the effect of the GLP-1RA semaglutide on inflammatory and hypoxia-related pathways in the kidney. The combination of MRI and tissue-level interrogation with biopsies will complement standard laboratory findings, enabling the identification of cells and pathways involved in kidney disease and protection. The trial will provide valuable mechanistic insights on the use of OW semaglutide in people with T2D and CKD and may stimulate the development of a precision medicine approach to the management of such individuals. In addition, REMODEL will complement the findings of the FLOW trial.

Assessment of Liver Fibrosis by Transient Elastography in Children and Young Adults With Sickle Cell Disease With and Without Iron Overload.

Transfusion-associated iron overload may cause liver fibrosis. We compared transient elastography (TE) and aspartate aminotransferase-platelet ratio index (APRI), noninvasive markers for hepatic fibrosis, to liver histology in children and young adults with sickle cell disease (SCD) who were iron overloaded (cohort 1). Age-matched subjects with SCD but without iron overload (cohort 2) were enrolled for APRI and TE assessments. Nineteen subjects ages 10 to 21 years were transfused for a mean of 9.67 years, had a mean serum ferritin of 4899±2849 ng/mL, and a liver iron concentration of 15.56±10.12 mg/g dry liver weight by R2-magnetic resonance imaging. Mean APRI was 0.33±0.13 in cohort 1 and 0.27±0.10 in cohort 2. The mean liver stiffness measures (LSM) in cohort 1, assessed by TE, was 8.46±3.95 kPa, ranging from 3.5 to 14.6 kPa (expected normal <7 kPa). Cohort 2 had a mean LSM of 5.72±1.74 kPa (4.6 to 8.7 kPa). There was a good correlation between LSM and histologic fibrosis (t value 6.94, P<0.0001). There was no significant correlation between APRI and histologic fibrosis and between APRI and LSM. A high LSM suggests liver fibrosis in children and adults with SCD with iron overload and may merit histologic confirmation especially if persistent.

Imaging‐Guided Targeted Drug Delivery using Stimuli‐Sensitive Theranostic Nanoparticles: Characterization and In Vivo Trafficking Patterns

Purpose : In type 1 diabetes (T1D), the existing delivery systems for insulin all suffer from the inability to regulate insulin without patient intervention. A major unmet medical need is to develop innovative strategy, which would increase the efficacy of immune therapeutics but also, reduce their toxicity. Targeted drug carriers using polymeric nanoparticles (NP) holds particular promise to enhance the delivery of immunoregulatory agents to treat T1D. The aim of this study was to synthesize and characterize the in vivo trafficking patterns of stimuli-responsive, thermosensitive, immunoregulatory-carriers for potential use in image-guided targeted delivery and on site controlled release. Methods : A number of metal nanoparticles with hyperthermia magnetic (HMNs) properties made out of Gd-Zn-Fe were fabricated that intrinsically have the ability to self-regulate their heating level to the desired therapeutic range, Curie temperature (Tc). Production of particles of uniform size and shape was ensured by constant reaction kinetics and efficient physical and chemical reactions in solution. The particles morphology was examined using electron microscopy. The size distribution was evaluated using Malvern Nanosizer device. Magnetic resonance imaging (MRI) relaxivities of HMNs were measured over a range of 25-45°C. Non-targeted and MECA79-targeted HMNs were engineered using self-assembly nanoprecipitation method. Targeted trafficking of MECA79-HMNs in skin transplanted NOD mice with distinctive lymphatic draining to the draining lymph nodes (DLN) was evaluated. To be able to image the particles, particles were coated with IRDye 800CW. Using iBox, live fluorescence imaging was carried out 8 days post transplantation (24 hours post IV administration). Results : The temperature of HMN (with Tc 38-40°C) rose only up to the Tc when the particles were subjected to an oscillating magnetic field, and further increasing the intensity of the field did not increase heating beyond their Tc. Increasing Gd ratio modulated Tc linearly with amount of Gd-substituted Zn Ferrite particles (Figure 1A). NPs TEM micrograph showed a dispersion of spherical particles with a narrow size distribution (Figure 1B). MRI relaxivities, R1 and R2, showed linear increase of the relaxation rate. Twenty-four hours post IV administration, there was a significant increase in the trafficking of MECA79 conjugated particles as compared to the non-targeted NPs to the DLN in the skin transplanted NOD mice (Figure 2). Conclusion : Nanomedicine's application of ITS to T1D remains to be developed. While there are a number of delivery approaches that target the LN, virtually all of them rely on passive lymphatic absorption (i.e., intradermal injection). Data presented here represent major achievements to establish for the first time systemic delivery of particles to specific sites in diabetic mice. These experiments serve the basis for developing more of multifunctional NPs.

Evaluation of Liver Iron Content by Magnetic Resonance Imaging in Children with Acute Lymphoblastic Leukemia after Cessation of Treatment

Objective:There are a limited number of studies evaluating iron overload in childhood leukemia by magnetic resonance imaging (MRI). The aim of this study was to determine liver iron content (LIC) by MRI in children with acute lymphoblastic leukemia (ALL) who had completed treatment and to compare those values with serum iron parameters.Materials and Methods:A total of 30 patients between the ages of 7 and 18 who had completed ALL treatment were included in the study. Serum iron parameters (serum iron, serum ferritin [SF], and total iron-binding capacity) and liver function tests were studied. R2 MRI was performed for determining LIC.Results:Normal LIC was detected in 22 (63.4%) of the cases. Seven (23.3%) had mild and 1 (3.3%) had moderate liver iron deposition. In contrast, severe iron overload was not detected in any of the cases. LIC levels were correlated with the numbers of packed red blood cell (pRBC) transfusions (r=0.637, p<0.001), pRBC transfusion volume (r=0.449, p<0.013), SF levels (r=0.561, p=0.001), and transferrin saturation (r=0.353, p=0.044). In addition, a positive correlation was found between the number of pRBC transfusions and SF levels (r=0.595, p<0.001).Conclusion: We showed that the frequency of liver iron deposition was low and clinically less significant after the end of treatment in childhood ALL patients. LIC was demonstrated to be related to SF and transfusion history. These findings support that SF and transfusion history may be used as references for monitoring iron accumulation or identifying cases for further examinations such as MRI.

Positron emission tomography/computed tomography using 2-deoxy-2-fluoro-18-fluoro-D-glucose peri-tumoral halo uptake layer method outperforms magnetic resonance imaging and ultrasound methods in tumor size measurement of breast cancer.

As a non-invasive method, positron emission tomography (PET)/computed tomography (CT) using 2-deoxy-2-fluoro-18-fluoro-D-glucose (18F-FDG) is applied as a useful modality in the diagnosis of breast cancer. By evaluating glucose metabolism, this method can also be used in staging, restaging and post-therapeutic response evaluation. To evaluate the reliability of the 18F-FDG PET/CT-based peri-tumoral halo uptake layer (PHL) method for assessing tumor size, a total of 79 female patients with breast cancer who underwent 18F-FDG PET/CT, breast ultrasound and magnetic resonance imaging (MRI) evaluations were included in the present study. Upon examination by two independent nuclear medicine radiologists, tumor sizes were estimated by 18F-FDG PET/CT using margins defined as the inner line of the PHL. Pathological tumor sizes were evaluated on the direction of largest diameter indicated by previous imaging examination, which were also utilized as final standards. Statistical analysis of the results suggested that 18F-FDG PET/CT had a more linear correlation with pathology compared with breast ultrasound (r2=0.89 vs. 0.73) and MRI (r2=0.89 vs. 0.69) in terms of tumor size estimation, including a significantly lower bias in size difference relative to pathology. 18F-FDG PET/CT also exhibited improved performance compared with breast ultrasound and MRI in T stage assessment. These results indicated that the 18F-FDG PET/CT-based PHL method was superior to breast ultrasound and MRI, and that it provides sufficient reliability and high accuracy for measuring tumor size in patients with breast cancer.

Measurement of the liver iron concentration in transfusional iron overload by MRI R2* and by high-transition-temperature superconducting magnetic susceptometry

PurposeTo compare measurement of the liver iron concentration in patients with transfusional iron overload by magnetic resonance imaging (MRI), using R2*, and by magnetic susceptometry, using a new high-transitiontemperature (high-Tc; operating at 77 K, cooled by liquid nitrogen) superconducting magnetic susceptometer. MethodsIn 28 patients with transfusional iron overload, 43 measurements of the liver iron concentration were made by both R2* and high-Tc magnetic susceptometry. ResultsMeasurements of the liver iron concentration by R2* and high-Tc magnetic susceptometry were significantly correlated when comparing all patients (Pearson's r = 0.91, p < 0.0001) and those with results by susceptometry >7 mg Fe/g liver, dry weight (r = 0.93, p = 0.006). In lower ranges of liver iron, no significant correlations between the two methods were found (0 to <3.2 mg Fe/g liver, dry weight: r = 0.2, p = 0.37; 3.2 to 7 mg Fe/g liver, dry weight: r = 0.41; p = 0.14). ConclusionThe lack of linear correlation between R2* and magnetic susceptibility measurements of the liver iron concentration with minimal or modest iron overload may be due to the effects of fibrosis and other cellular pathology that interfere with R2* but do not appreciably alter magnetic susceptibility.

Magnetic Heating Stimulated Cargo Release with Dose Control using Multifunctional MR and Thermosensitive Liposome.

Rationale: Magnetic resonance imaging (MRI) is one of the most widely used diagnostic tools in the clinic. In this setting, real-time monitoring of therapy and tumor site would give the clinicians a handle to observe therapeutic response and to quantify drug amount to optimize the treatment. In this work, we developed a liposome-based cargo (cancer drugs) delivery strategy that could simultaneously monitor the real-time alternating magnetic field-induced cargo release from the change in MRI relaxation parameter R1 and the location and condition of liposome from the change in R2. The tumor site can then be monitored during the cargo release because liposomes would passively target the tumor site through the enhanced permeability and retention (EPR) effect. Physical insights from the experimental results and corresponding Monte Carlo spin dynamics simulations were also discussed.Methods: Superparamagnetic iron oxide (SPIO) nanoparticles, diethylenetriaminepentaacetic acid gadolinium(III) (Gd(III)-DTPA), and a model cancer drug (fluorescein) were co-loaded in PEGylated thermosensitive liposomes. The liposomes were characterized by transmission electron cryo-microscopy (cryoTEM), dynamic light scattering (DLS), and inductively coupled plasma optical emission spectrometry (ICP-OES). Alternating magnetic field (AMF) was used to create controlled mild hyperthermia (39-42°C) and facilitate controlled cargo (fluorescein) release from the thermosensitive liposomes. MRI relaxation parameters, R1 and R2, were measured at room temperature. The temporal variation in R1 was used to obtain the temporal profile of cargo release. Due to their similar sizes, both the gadolinium and cargo (model cancer drug fluorescein) would come out of the liposomes together as a result of heating. The temporal variation in R2 was used to monitor SPIO nanoparticles to enhance the tumor contrast. Monte Carlo spin dynamics simulations were performed by solving the Bloch equations and modeling SPIO nanoparticles as magnetized impenetrable spheres.Results: TEM images and DLS measurements showed the diameter of the liposome nanoparticle ~ 200 nm. AMF heating showed effective release of the model drug. It was found that R1 increased linearly by about 70% and then saturated as the cargo release process was completed, while R2 remained approximately constant with an initial 7%-drop and then recovered. The linear increase in R1 is consistent with the expected linear cargo release with time upon AMF heating. Monte Carlo spin dynamics simulations suggest that the initial temporal fluctuation of R2 is due to the plausible changes of SPIO aggregation and the slow non-recoverable degradation of liposomal membrane that increases water permeability with time by the heating process. The simulations show an order of magnitude increase in R2 at higher water permeability.Conclusion: We have performed MR parameter study of the release of a cargo (model cancer drug, fluorescein) by magnetic heating from thermosensitive multifunctional liposomes loaded with dual contrast agents. The size of the liposome nanoparticles loaded with model cancer drug (fluorescein), gadolinium chelate, and SPIO nanoparticles was appropriate for a variety of cancer therapies. A careful and detailed analysis with theoretical explanation and simulation was carried out to investigate the correlation between MRI relaxation parameters, R1 and R2, and different cargo release fractions. We have quantified the cargo release using R1, which shows a linear relation between each other. This result provides a strong basis for the dosage control of drug delivered. On the other hand, the fairly stable R2 with almost constant value suggests that it could be used to monitor the position and condition of the liposomal site, as SPIO nanoparticles mostly remained in the aqueous core of the liposome. Because our synthesized SPIO-encapsulated liposomes could be targeted to tumor site passively by the EPR effect, or actively through magnetofection, this study provides a solid ground for developing MR cancer theranostics in combination of this nanostructure and AMF heating strategy. Furthermore, our simulation results predict a sharp increase in R2 during the AMF heating, which opens up the exciting possibility of high-resolution, high-contrast real-time imaging of the liposomal site during the drug release process, provided AMF heating could be incorporated into an MRI setup. Our use of the clinically approved materials, along with confirmation by theoretical simulations, make this technique a promising candidate for translational MR cancer theranostics.

Aortic stiffness in families with inherited non-syndromic thoracic aortic disease

Background. In families with an inherited form of non-syndromic thoracic aortic disease (TAAD), aortic diameter alone is not a reliable marker for disease occurrence or progression. To identify other parameters of aortic function, we studied aortic stiffness in families with TAAD. We also compared diameter measurements obtained by transthoracic echocardiography (TTE) and magnetic resonance imaging (MRI). Methods. Seven families, including 116 individuals, with non-syndromic TAAD, were studied. The aortic diameter was measured by TTE and MRI. Aortic stiffness was assessed as local distensibility in the ascending aorta and as regional and global pulse wave velocity (PWV). Individuals with a dilated thoracic aorta (n = 21) were compared with those without aortic dilatation (n = 95). Results. Ascending aortic diameter measured by TTE strongly correlated with the diameter measured by MRI (r2 = 0.93). The individuals with dilated aortas were older than those without dilatation (49 vs 37 years old). Ascending aortic diameter increased and distensibility decreased with increasing age; while, PWV increased with age and diameter. Some young subjects without aortic dilatation showed increased aortic stiffness. Individuals with a dilated thoracic aorta had significantly higher PWV and lower distensibility, measured by MRI than individuals without dilatation. Conclusions. Diameters measured with TTE agree with those measured by MRI. Aortic stiffness might be a complementary marker for aortic disease and progression when used with aortic diameter, especially in young individuals.

Minocycline Effects on Intracerebral Hemorrhage-Induced Iron Overload in Aged Rats

Brain iron overload is a key factor causing brain injury after intracerebral hemorrhage (ICH). This study quantified brain iron levels after ICH with magnetic resonance imaging R2* mapping. The effect of minocycline on iron overload and ICH-induced brain injury in aged rats was also determined. Aged (18 months old) male Fischer 344 rats had an intracerebral injection of autologous blood or saline, and brain iron levels were measured by magnetic resonance imaging R2* mapping. Some ICH rats were treated with minocycline or vehicle. The rats were euthanized at days 7 and 28 after ICH, and brains were used for immunohistochemistry and Western blot analyses. Magnetic resonance imaging (T2-weighted, T2* gradient-echo, and R2* mapping) sequences were performed at different time points. ICH-induced brain iron overload in the perihematomal area could be quantified by R2* mapping. Minocycline treatment reduced brain iron accumulation, T2* lesion volume, iron-handling protein upregulation, neuronal cell death, and neurological deficits (P<0.05). Magnetic resonance imaging R2* mapping is a reliable and noninvasive method, which can quantitatively measure brain iron levels after ICH. Minocycline reduced ICH-related perihematomal iron accumulation and brain injury in aged rats.

Improved liver R2* mapping by pixel-wise curve fitting with adaptive neighborhood regularization.

To improve liver R2* mapping by incorporating adaptive neighborhood regularization into pixel-wise curve fitting. Magnetic resonance imaging R2* mapping remains challenging because of the serial images with low signal-to-noise ratio. In this study, we proposed to exploit the neighboring pixels as regularization terms and adaptively determine the regularization parameters according to the interpixel signal similarity. The proposed algorithm, called the pixel-wise curve fitting with adaptive neighborhood regularization (PCANR), was compared with the conventional nonlinear least squares (NLS) and nonlocal means filter-based NLS algorithms on simulated, phantom, and in vivo data. Visually, the PCANR algorithm generates R2* maps with significantly reduced noise and well-preserved tiny structures. Quantitatively, the PCANR algorithm produces R2* maps with lower root mean square errors at varying R2* values and signal-to-noise-ratio levels compared with the NLS and nonlocal means filter-based NLS algorithms. For the high R2* values under low signal-to-noise-ratio levels, the PCANR algorithm outperforms the NLS and nonlocal means filter-based NLS algorithms in the accuracy and precision, in terms of mean and standard deviation of R2* measurements in selected region of interests, respectively. The PCANR algorithm can reduce the effect of noise on liver R2* mapping, and the improved measurement precision will benefit the assessment of hepatic iron in clinical practice. Magn Reson Med 80:792-801, 2018. © 2018 International Society for Magnetic Resonance in Medicine.

Relationship between liver iron concentration determined by R2-MRI, serum ferritin, and liver enzymes in patients with thalassemia intermedia

BackgroundIron overload is a risk factor affecting all patients with thalassemia intermedia (TI). We aimed to determine whether there is a relationship of serum ferritin (SF) and alanine aminotransferase (ALT) with liver iron concentration (LIC) determined by R2 magnetic resonance imaging (R2-MRI), to estimate the most relevant degree of iron overload and best time to chelate in patients with TI.MethodsIn this cross-sectional study, 119 patients with TI (mean age years) were randomly selected and compared with 120 patients who had a diagnosis of thalassemia major (TM). Correlations of LIC, as determined by R2-MRI, with SF and ALT levels, were assessed in all participants. A P-value <0.05 was considered statistically significant.ResultsSF and LIC levels were lower in patients with TI than in those with TM; only ferritin values were significant. We found a statistically significant relationship between SF and LIC, with cut-off estimates of SF in patients with TI who had splenectomy and those who entered puberty spontaneously (916 and 940 ng/mL, respectively) with LIC >5 mg Fe/g dry weight (P<0.0001). A significant relationship was also found for patients with TI who had elevated ALT level (63.5 U/L), of 3.15 times the upper normal laboratory limit, using a cut-off for LIC ≥5 mg Fe/g dry weight.ConclusionWe determined the cut-off values for ALT and SF indicating the best time to start iron chelation therapy in patients with TI, and found significant correlations among iron overload, SF, and ALT.

Utility of Transient Elastography in Estimating Hepatic Iron Concentration in Comparison to Magnetic Resonance Imaging in Patients Who are Transfusion-Dependent: A Canadian Center Experience

Transfusion-dependent hereditary anemias such as β-thalassemia (β-thal), predispose patients to iron overload and its numerous clinical sequelae. Accurate assessment of overall iron status and prompt initiation of chelation therapy to prevent irreversible end-organ damage can be achieved using magnetic resonance imaging (MRI) to measure liver iron concentration (LIC) as a surrogate marker of total body iron; however, its access may be associated with long wait times and delay in treatment. We report an observational cohort study at a single tertiary care center assessing the theoretical role of transient elastography (TE), which measures liver stiffness, in estimating LIC compared to other established diagnostic measures. While regression analyses confirm a moderate correlation between LIC per R2 MRI and serum ferritin level (pooled estimate of correlation = 0.55), there was no significant correlation between TE reading and LIC based on R2 MRI (pooled estimate of correlation = −0.06), and only a weak correlation was observed with serum ferritin level (pooled estimate of correlation = 0.45). These results suggest TE may not be sensitive enough to detect subtle changes in the hepatic parenchymal stiffness associated with liver iron deposition.

Iron Overload Status in Patients with Non-Transfusion-Dependent Thalassemia in China

▪Background: Non-transfusion-dependent thalassemia (NTDT) is a genetic disorder most commonly including beta-thalassemia intermedia (Beta-TI), HbE/Beta thalassemia (HbE/Beta thalassemia), and hemoglobin H disease (HbH disease). NTDT patients can be at risk of iron overload due to increased intestinal iron absorption triggered by chronic anemia, ineffective erythropoiesis and, possibly, decreased serum hepcidin. Despite NTDT is popular in southern China, there is little data evaluating iron overload in Chinese patients. This study aimed at investigating the occurrence, prevalence and severity of iron overload in Chinese population with NTDT.Methods: We evaluated the serum ferritin (SF), liver iron concentration (LIC) and cardiac T2* in 158 NTDT patients (83 with HbH disease, 45 with Beta-TI and 30 with HbE/Beta thalassemia) in China. The median age was 22 years old. The main characteristics of these patients along with the main results of the study were summarized in Table 1. Blood samples were obtained for the assessment of hemoglobin (Hb) and serum ferritin (SF) levels. LIC was assessed by using validated R2 magnetic resonance imaging [MRI] (FerriScan®). Cardiac iron level was measured by MRI T2*. Patients were scanned with MRI 1.5 T (Siemens Avanto, Germany). The study was performed at the First Affiliated Hospital of Guangxi Medical University. LIC < 3mg Fe/g dw and cardiac T2* > 20ms was considered normal. Abnormal LIC can be divided into mild: 3-7mg Fe/g dw, moderate: 7-15mg Fe/g dw, severe: >15mg Fe/g dw. All patients or parents/guardians provided their written informed consent to participate in this study. The study was approved by the Medical Ethics Committee of the First Affiliated Hospital of Guangxi Medical University.Results: The median SF level of 158 NTDT patients was 1,037(27.0-19,704) ng/ ml. LIC was detected in 155 patients (98.1%) and the median LIC value was 8.9(0.6-43) mg Fe/g dw. There were 15 patients (60%) (8 with HbH disease, 5 with Beta-TI and 2 with HbE/Beta thalassemia)<10 years old found liver iron overload. The youngest patient with liver iron overload was 5 years old with 5.6mg Fe/g dw in LIC. Cardiac T2*was assessed in 111 patients (70.2%) and the median cardiac T2* was 32.8(7.5-75.1)ms. The 7 patients (4.4%) (4 with HbH disease and 3 with Beta-TI) had cardiac T2*=<20ms. There was a significant correlation between LIC and SF (r=0.809, p<0.001). No correlation between LIC and Hb, cardiac T2* values can be verified.There was a significant correlation between LIC and age (r=0.497, p<0.001)(Fig 1). The levels of LIC in patients > 30-year old group are significantly higher than those in other groups (Fig 2).The patients with Beta-TI and HbE/Beta thalassemia showed a statistically significant lower Hb and higher values of SF and LIC than those of HbH disease patients.Conclusions: Chinese NTDT patients have a high prevalence of iron overload. The iron overload in patients with Beta-TI and HbE/Beta thalassemia are more serious than those in HbH disease patients. The age of patient is a risk factor of iron overload in NTDT patient. Patients > 30 years old have a high burden of iron overload. Our data shows that the first assessment of MRI LIC should be performed as early as 5 years old. [Display omitted] [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Characterizing active and inactive brown adipose tissue in adult humans using PET-CT and MR imaging.

Activated brown adipose tissue (BAT) plays an important role in thermogenesis and whole body metabolism in mammals. Positron emission tomography (PET)-computed tomography (CT) imaging has identified depots of BAT in adult humans, igniting scientific interest. The purpose of this study is to characterize both active and inactive supraclavicular BAT in adults and compare the values to those of subcutaneous white adipose tissue (WAT). We obtained [(18)F]fluorodeoxyglucose ([(18)F]FDG) PET-CT and magnetic resonance imaging (MRI) scans of 25 healthy adults. Unlike [(18)F]FDG PET, which can detect only active BAT, MRI is capable of detecting both active and inactive BAT. The MRI-derived fat signal fraction (FSF) of active BAT was significantly lower than that of inactive BAT (means ± SD; 60.2 ± 7.6 vs. 62.4 ± 6.8%, respectively). This change in tissue morphology was also reflected as a significant increase in Hounsfield units (HU; -69.4 ± 11.5 vs. -74.5 ± 9.7 HU, respectively). Additionally, the CT HU, MRI FSF, and MRI R2* values are significantly different between BAT and WAT, regardless of the activation status of BAT. To the best of our knowledge, this is the first study to quantify PET-CT and MRI FSF measurements and utilize a semiautomated algorithm to identify inactive and active BAT in the same adult subjects. Our findings support the use of these metrics to characterize and distinguish between BAT and WAT and lay the foundation for future MRI analysis with the hope that some day MRI-based delineation of BAT can stand on its own.

Acute changes in liver tumour perfusion measured non-invasively with arterial spin labelling.

Background:Non-invasive measures of tumour vascular perfusion are desirable, in order to assess response to vascular targeting (or modifying) therapies. In this study, hepatic arterial spin labelling (ASL) magnetic resonance imaging (MRI) was investigated to measure acute changes in perfusion of colorectal cancer in the liver, in response to vascular disruption therapy with OXi4503.Methods:SW1222 and LS174T tumours were established in the liver of MF1 nu/nu mice via intrasplenic injection. Perfusion and R2* MRI measurements were acquired with an Agilent 9.4T horizontal bore scanner, before and at 90 min after 40 mg kg−1 OXi4503.Results:A significant decrease in SW1222 tumour perfusion was observed (−43±33%, P<0.005). LS174T tumours had a significantly lower baseline level of perfusion. Intrinsic susceptibility MRI showed a significant increase in R2* in LS174T tumours (28±25%, P<0.05). An association was found between the change in tumour perfusion and the proximity to large vessels, with pre-treatment blood flow predictive of subsequent response. Histological evaluation confirmed the onset of necrosis and evidence of heterogeneous response between tumour deposits.Conclusions:Hepatic ASL-MRI can detect acute response to targeted tumour vascular disruption entirely non-invasively. Hepatic ASL of liver tumours has potential for use in a clinical setting.

Increased R2* in the Caudate Nucleus of Asymptomatic Welders.

Welding has been associated with neurobehavioral disorders. Welding fumes contain several metals including copper (Cu), manganese (Mn), and iron (Fe) that may interact to influence welding-related neurotoxicity. Although welding-related airborne Fe levels are about 10-fold higher than Mn, previous studies have focused on Mn and its accumulation in the basal ganglia. This study examined differences in the apparent transverse relaxation rates [R2* (1/T2*), estimate of Fe accumulation] in the basal ganglia (caudate nucleus, putamen, and globus pallidus) between welders and controls, and the dose-response relationship between estimated Fe exposure and R2* values. Occupational questionnaires estimated recent and lifetime Fe exposure, and blood Fe levels and brain magnetic resonance imaging (MRI) were obtained. Complete exposure and MRI R2* and R1 (1/T1: measure to estimate Mn accumulation) data from 42 subjects with welding exposure and 29 controls were analyzed. Welders had significantly greater exposure metrics and higher whole-blood Fe levels compared with controls. R2* in the caudate nucleus was significantly higher in welders after controlling for age, body mass index, respirator use, caudate R1, and blood metals of Cu and Mn, whereas there was no difference in R1 values in the basal ganglia between groups. The R2* in the caudate nucleus was positively correlated with whole-blood Fe concentration. This study provides the first evidence of higher R2* in the caudate nucleus of welders, which is suggestive of increased Fe accumulation in this area. Further studies are needed to replicate the findings and determine the neurobehavioral relevance.

SPIO-labeled Yttrium Microspheres for MR Imaging Quantification of Transcatheter Intrahepatic Delivery in a Rodent Model

To investigate the qualitative and quantitative impacts of labeling yttrium microspheres with increasing amounts of superparamagnetic iron oxide (SPIO) material for magnetic resonance (MR) imaging in phantom and rodent models. Animal model studies were approved by the institutional Animal Care and Use Committee. The r2* relaxivity for each of four microsphere SPIO compositions was determined from 32 phantoms constructed with agarose gel and in eight concentrations from each of the four compositions. Intrahepatic transcatheter infusion procedures were performed in rats by using each of the four compositions before MR imaging to visualize distributions within the liver. For quantitative studies, doses of 5, 10, 15, or 20 mg 2% SPIO-labeled yttrium microspheres were infused into 24 rats (six rats per group). MR imaging R2* measurements were used to quantify the dose delivered to each liver. Pearson correlation, analysis of variance, and intraclass correlation analyses were performed to compare MR imaging measurements in phantoms and animal models. Increased r2* relaxivity was observed with incremental increases of SPIO microsphere content. R2* measurements of the 2% SPIO-labeled yttrium microsphere concentration were well correlated with known phantom concentrations (R(2) = 1.00, P < .001) over a broader linear range than observed for the other three compositions. Microspheres were heterogeneously distributed within each liver; increasing microsphere SPIO content produced marked signal voids. R2*-based measurements of 2% SPIO-labeled yttrium microsphere delivery were well correlated with infused dose (intraclass correlation coefficient, 0.98; P < .001). MR imaging R2* measurements of yttrium microspheres labeled with 2% SPIO can quantitatively depict in vivo intrahepatic biodistribution in a rat model.