Diffusion Coefficient Measurements Research Articles

Diffusion-Weighted Imaging of the Abdomen: Correction for Gradient Nonlinearity Bias in Apparent Diffusion Coefficient.

Gradient nonlinearity (GNL) introduces spatial nonuniformity bias in apparent diffusion coefficient (ADC) measurements, especially at large offsets from the magnet isocenter. To investigate the effects of GNL in abdominal ADC measurements and to develop an ADC bias correction procedure. Retrospective. Two homemade ultrapure water phantoms/25 patients with histologically confirmed pancreatic ductal adenocarcinoma (PDAC). A 3.0 T/diffusion-weighted imaging (DWI) with single-shot echo-planar imaging sequence. ADC bias was computed in the three orthogonal directions at different offset locations. The spatial-dependent correctors of ADC bias were generated from the ADCs of phantom 1. The ADCs were estimated before and after corrections for the phantom 1 with both the proposed approach and the theoretical GNL correction method. For the patients, ADCs were measured in abdominal tissues including left and right liver lobes, PDAC, spleen, bilateral kidneys, and bilateral paraspinal muscles. Friedman tests and Wilcoxon tests. The ADC bias measured by phantom 1 was 9.7% and 12.6% higher in the right-left and anterior-posterior directions and 9.2% lower in the superior-inferior direction at the 150 mm offsets from the magnetic isocenter. The corrected vs. the uncorrected ADCs measurements (median: 2.20× 10-3 mm2 /sec for both the proposed method and the theoretical GNL method vs. 2.31× 10-3 mm2 /sec, respectively) and their relative ADC errors (0.014, 0.016, and 0.054, respectively) were lower in the phantom 1. The relative ADC errors substantially decreased after correction in the phantom 2 (median: 0.048 and -0.008, respectively). The ADCs of all the abdominal tissues were lower after correction except for the left liver lobes (P=0.13). GNL bias in abdominal ADC can be measured by a DWI phantom. The proposed correction procedure was successfully applied for the bias correction in abdominal ADC. 3. Stage 1.

Manifestations of static and dynamic heterogeneity in single molecule translational measurements in glassy systems.

Rotational-translational decoupling in systems near Tg, in which translational diffusion is apparently enhanced relative to rotation, has been observed in ensemble and single molecule experiments and has been linked to dynamic heterogeneity. Here, simulations of single molecules experiencing homogeneous diffusion and static and dynamic heterogeneous diffusion are performed to clarify the contributions of heterogeneity to such enhanced translational diffusion. Results show that time-limited trajectories broaden the distribution of diffusion coefficients in the presence of homogeneous diffusion but not when physically reasonable degrees of static heterogeneity are present. When dynamic heterogeneity is introduced, measured diffusion coefficients uniformly increase relative to input diffusion coefficients, and the widths of output distributions decrease, providing support for the idea that dynamic heterogeneity can drive apparent translational enhancement. Among simulations with dynamic heterogeneity, when the frequency of dynamic exchange is correlated with the initial diffusion coefficient, the measured diffusion coefficient behavior as a function of observation time matches that seen experimentally, the only set of simulations explored in which this occurs. Taken together with experimental results, this suggests that enhanced translational diffusion in glassy systems occurs through dynamic exchange consistent with wide underlying distributions of diffusion coefficients and exchange coupled to local spatiotemporal dynamics.

NMR investigation of counterion binding to undecyl LL-leucinevalanate micelles

NMR spectroscopy was used to investigate the binding of cationic counterions to anionic micelles formed by undecyl LL-leucinevalaninate (und-LV). Amino acid-based surfactants like und-LV are green alternatives to commercial surfactants. Monomeric and polymeric forms of und-LV micelles have also been used as chiral selectors in capillary electrophoresis (CE) separations. The counterions investigated were Na+, the tetraethylammonium ion, L-Lysine, 1,4-diaminobutane, 1,6-diaminohexane, and cis and trans isomers of 1,2-diaminocyclohexane and 1,4-diaminocyclohexane. NMR measurements of counterion and micelle diffusion coefficients were used to calculate micelle radii and the mole fraction of counterion molecules bound to the micelles. Two-dimensional NMR experiments were used to investigate the structures of the counterion: micelle complexes. The mole fraction of bound counterions did not change with pH in solutions containing Na+ or tetraethylammonium counterions. With all other counterions, however, the mole fraction of micelle-bound counterions was higher below pH 10 when counterions had a + 1 or +2 charge, and lower above pH 10–10.5 when the counterions were neutral or zwitterionic. Changes in micelle radii with pH and two-dimensional NMR experiments suggested that L-Lysine, 1,4-diaminobutane, and 1,6-diaminohexane bound parallel to the micelle surface with their amine functional groups interacting with different surfactant monomers. In contrast, the diaminocyclohexane isomers were found to bind perpendicular to the micelle surface. The mole fractions of micelle-bound cis-1,4-diaminocyclohexane and trans-1,4-diaminocyclohexane were very similar to one another. However, with 1,2-cyclohexanediamine, at low pH the mole fraction of micelle-bound counterions was larger for the cis isomer than for the trans isomer.

Evidence for growing structural correlation length in colloidal supercooled liquids.

Using video microscopy, we measure the long-time diffusion coefficients of colloidal particles at different concentrations. The measured diffusion coefficients start to deviate from theoretical predictions based on random collision models upon entering the supercooled regime. The theoretical diffusion relation is recovered by assigning an effective mass proportional to the size of structurally correlated clusters to the diffusing particles, providing an indirect method to probe the growth of static correlation length scales approaching the glass transition. This method is tested and validated in the crystallization of mono-disperse colloids in quasi-two-dimensional experiments. The correlation length obtained for a binary colloidal liquid increases by a power law toward a critical packing fraction of ∼0.79. The system relaxation time exhibits a power-law dependence on the correlation length in agreement with dynamical facilitation theories.

A novel methodology for measurement of the diffusion coefficient between CO2 and oil based on quantification of the oil droplet swelling behavior

Accurate and fast determination of the diffusion coefficient of the CO2/oil system is essential in CO2 enhanced oil recovery (CO2-EOR) and CO2 geological sequestration practices. In this work, a novel methodology is proposed and demonstrated on measuring the diffusion coefficient of the immiscible CO2/oil binary systems based on quantification of the oil droplet swelling behavior. Five oil samples, including n-decane, n-dodecane, n-tetradecane, n-hexadecane and liquid paraffin, are employed as the oil phase and the diffusion coefficient for each CO2/oil system were determined. After validation of the methodology based on good agreements between the measurement and the reported results for both the pure component oil and the synthetic oil, the diffusion characteristics of the CO2/oil systems are scrutinized in the pressure range 2–10 MPa and the temperature range 26.9–82.1 ℃. The measurement results clearly show the elevated system pressure could lead to stronger diffusion processes between the CO2 and the oil phase, while the temperature impacts on the diffusion process are more complex due to the synergistic effects of CO2 density and the oil viscosity. Performed in the state-of-the-art drop shape analyzer within a short measurement period, it is expected the proposed methodology could provide an efficient supplementary for diffusion coefficient measurements of the CO2/oil binary systems.

Electrochemical Measurement of Interfacial Distribution and Diffusion Coefficients of Electroactive Species for Ion-Exchange Membranes: Application to Br2/Br- Redox Couple.

A novel method has been proposed for rapid determination of principal transmembrane transport parameters for solute electroactive co-ions/molecules, in relation to the crossover problem in power sources. It is based on direct measurements of current for the electrode, separated from solution by an ion-exchange membrane, under voltammetric and chronoamperometric regimes. An electroactive reagent is initially distributed within the membrane/solution space under equilibrium. Then, potential change induces its transformation into the product at the electrode under the diffusion-limited regime. For the chronoamperometric experiment, the electrode potential steps backward after the current stabilization, thus inducing an opposite redox transformation. Novel analytical solutions for nonstationary concentrations and current have been derived for such two-stage regime. The comparison of theoretical predictions with experimental data for the Br2/Br- redox couple (where only Br- is initially present) has provided the diffusion coefficients of the Br- and Br2 species inside the membrane, D(Br-) = (2.98 ± 0.27) 10-6 cm2/s and D(Br2) = (1.10 ± 0.07) 10-6 cm2/s, and the distribution coefficient of the Br- species at the membrane/solution boundary, K(Br-) = 0.190 ± 0.005, for various HBr additions (0.125-0.75 M) to aqueous 2 M H2SO4 solution. This possibility to determine transport characteristics of two electroactive species, the initial solute component and its redox product, within a single experiment, represents a unique feature of this study.

Luciferase‐free Luciferin Electrochemiluminescence

AbstractLuciferin is one of Nature's most widespread luminophores, and enzymes that catalyze luciferin luminescence are the basis of successful commercial “glow” assays for gene expression and metabolic ATP formation. Herein we report an electrochemical method to promote firefly's luciferin luminescence in the absence of its natural biocatalyst—luciferase. We have gained experimental and computational insights on the mechanism of the enzyme‐free luciferin electrochemiluminescence, demonstrated its spectral tuning from green to red by means of electrolyte engineering, proven that the colour change does not require, as still debated, a keto/enol isomerization of the light emitter, and gained evidence of the electrostatic‐assisted stabilization of the charge‐transfer excited state by double layer electric fields. Luciferin's electrochemiluminescence, as well as the in situ generation of fluorescent oxyluciferin, are applied towards an optical measurement of diffusion coefficients.

Prospective Assessment of Diffusion-Weighted-MRI as a Biomarker of Treatment Response and Disease Control in Head and Neck Cancer

<h3>Purpose/Objective(s)</h3> To determine diffusion-weighted MRI (DWI) parameters associated with tumor response and local control (LC) in head and neck (HNC) patients treated with definitive radiation therapy (RT). <h3>Materials/Methods</h3> Eighty-seven HNC patients enrolled in an active prospective imaging study at MD Anderson Cancer Center were included in the analysis. Patients had MRIs prior to, at mid-RT, and post-treatment completion. Inclusion criteria include adult with histologic evidence of malignant head and neck neoplasm indicated for curative-intent treatment with RT with/without chemotherapy; good performance status (ECOG score 0-2); and with no contraindications to MRI. Patients were scanned using a full-body MRI scanner with two large four-channel flex phased-array coils. We used fat-suppressed T2-weighted turbo spin echo for tumor segmentation which was co-registered to respective DWIs for extraction of apparent diffusion coefficient (ADC) measurements. Sequence parameters were (TR/TE (ms); pixel size/slice thickness (mm); b-values (s/mm2)): T2-weighted (5280/80; 0.5/2; N/A), BLADE (5900/50; 2/4; 0 & 800), RESOLVE (9380/63; 2/4; 0 & 800). Treatment response was assessed at mid-RT and at 8-12 weeks post-RT using RECIST 1.1 criteria and was defined as: complete response (CR) vs non-complete response (non-CR). Pre-RT ADC was correlated with RT response (CR vs non-CR) at mid- and post-RT time points. Mann-Whitney test was used to compare ADC values between the mid-treatment CR group and the non-CR group. Recursive partitioning analysis (RPA) was done to identify ADC threshold associated with relapse. <h3>Results</h3> Fifty-nine patients with grossly visible primary tumor volume prior to RT start were included in this analysis. Patients' disease and treatment criteria are shown in Table 1. Pre-treatment ADC was not correlated with tumor response or oncologic outcomes (P>0.05). For patients with CR at the end of RT, there was a significant increase in mean ADC at mid-RT compared to baseline ((1.8 ± 0.29) × 10^–3 mm²/s <i>vs</i> (1.37 ± 0.22) × 10^–3 mm²/s, <i>p</i> <0.0001). However, patients with no-CR had no statistically significant increase (p>0.05). Median follow-up was 32 months. Patients with ≤106% delta ADC at mid-RT had significantly worse local control at 2-year compared to patients with higher delta ADC (48% vs 96%, <i>p</i> <0.0001). <h3>Conclusion</h3> Delta ADC changes is a strong predictor of local recurrence in head and neck cancer patients. Multi-institutional data is needed for validation of our results.

DEVELOPMENT OF TIME-TEMPERATURE INDICATOR FROM RED PALM OIL AND MAIZE OIL BLENDING

Time-temperature indicator could be used to monitor temperature changes during storage and distribution. The time-temperature indicator with red palm oil and maize oil was evaluated to find the diffusion prediction model and the right oil blending proportion based on activation energy. This research was performed in two stages. Stage 1 was production of red palm oil and maize oil blending in five ratios: A1 (70:30), A2 (60:40), A3 (50:50), A4 (40:60), A5 (30:70) (%v/v). Stage 2 was measurement of diffusion rate, coefficient, kinetics and activation energy in photo paper medium at 4, 29, 37, 44 and 51 °C. The result showed that increasing the temperature could increase diffusion rate and coefficient. The A5 blending proportion had 36.7961 kJ/mol energy activation which were in range of commercial time-temperature indicator (34-50 kJ/mol). The diffusion prediction model was Ln D = -4425.8 – 3.1187.

Effect of ionomer swelling and capillary condensation of water on porous characteristics in cathode catalyst layers of polymer electrolyte membrane fuel cells under humidified conditions

Reducing oxygen diffusion resistance in the cathode catalyst layer of polymer electrolyte fuel cells under humidified conditions is essential for reducing the cost of expensive platinum catalysts. We designed an ionomer swelling model that reproduces isotherm adsorption and oxygen diffusion coefficient measurements, to elucidate the effect of pore blockage due to ionomer swelling and capillary condensation on the decrease in oxygen diffusivity. Coupled simulations of ionomer swelling, capillary condensation, and oxygen diffusion are performed using this model, and the water and swelled ionomer distributions at each relative humidity are elucidated. When the humidity is low, ionomer swelling is dominant for the oxygen diffusivity reduction, whereas when the humidity is high, both ionomer swelling and capillary condensation affect them.

ANALYSIS OF THE CORRELATIONAL RELATIONSHIP BETWEEN THE RESULTS OF ULTRASOUND ELASTOGRAPHY AND THE VALUES OF THE MEASURED DIFFUSION COEFFICIENT IN ASSESSING UTERINE AND ADNEXAL STRUCTURES IN REPRODUCTIVE AGE WOMEN

The purpose of the study. To study the correlational relationship between the results obtained by examining the uterus and ovaries in healthy women of reproductive age using shear wave ultrasound elastography with elastometry and magnetic resonance imaging (MRI) and assessment of the measured diffusion coefficient (MDC) of diffusion-weighted images (DWI). Materials and methods. The study group consisted of 45 healthy women of reproductive age (the average age was 32.9±3.1 years). All of them underwent ultrasound examination with the technology of two-dimensional shear wave elastography with elastometry (Aixplorer, Supersonic Imagine, France) according to the method developed and implemented by us. The MRI of uterine and ovarian structures was performed using the DWI protocol (Excelart Vantage Atlas magnetic resonance tomograph, Toshiba, Japan, 1.5 T), the myometrium and the uterine mucosa in the body and cervix, ovaries were evaluated. In the automatic mode, the MDC of unaltered structures in the uterine body and cervix and their appendages was calculated in the area of interest on ADC-maps. The degree of correlational relationship between the results of ultrasound elastography with elastometry and magnetic resonance tomography with an estimate of the measured diffusion coefficient was calculated. Results. Correlation analysis of the relationship between rigidity and the MDC of uterine and adnexal structures showed a direct inverse relationship between these values and a high degree of connection by Cheddock scale (p = 0.000000). At this, lesser MDC values (mm2 /s) of similar structures of the organs under study corresponded to large quantitative values of the Young's elasticity modulus (kPa) of all uterine and ovarian structures. Conclusion. The obtained data make it possible to optimize the diagnostic algorithm and to supplement the standard protocols for ultrasound and magnetic resonance imaging studies of gynecological organs using two-dimensional shear wave elastography with elastometry and magnetic resonance tomography with an assessment of the measured diffusion coefficient of diffusion-weighted images.

Utility of the Diffusion Weighted Sequence in Gynecological Imaging: Review Article.

Simple SummaryDiffusion weighted imaging (DWI) is a magnetic resonance imaging sequence with diverse clinical applications in malignant and nonmalignant gynecological conditions. It provides vital supplemental information in the diagnosis and management of various gynecological conditions. Radiologists should be aware of fundamental concepts, clinical applications and pitfalls of DWI. Additionally we briefly discuss potential scope of newer advanced techniques based on DWI including diffusion tensor imaging and diffusion-weighted whole-body imaging with background signal suppression.Functional imaging with diffusion-weighted imaging (DWI) is a complementary tool to conventional diagnostic magnetic resonance imaging sequences. It is being increasingly investigated to predict tumor response and assess tumor recurrence. We elucidate the specific technical modifications of DWI preferred for gynecological imaging, including the different b-values and planes for image acquisition. Additionally, we discuss the problems and potential pitfalls encountered during DWI interpretation and ways to overcome them. DWI has a wide range of clinical applications in malignant and non-malignant gynecological conditions. It provides supplemental information helpful in diagnosing and managing tubo-ovarian abscess, uterine fibroids, endometriosis, adnexal torsion, and dermoid. Similarly, DWI has diverse applications in gynecological oncology in diagnosis, staging, detection of recurrent disease, and tumor response assessment. Quantitative evaluation with apparent diffusion coefficient (ADC) measurement is being increasingly evaluated for correlation with various tumor parameters in managing gynecological malignancies aiding in preoperative treatment planning. Newer advanced DWI techniques of diffusion tensor imaging (DTI) and whole body DWI with background suppression (DWIBS) and their potential uses in pelvic nerve mapping, preoperative planning, and fertility-preserving surgeries are briefly discussed.

Deep-learned estimation of uncertainty in measurements of apparent diffusion coefficient from whole-body diffusion-weighted MRI

PurposeTo use deep learning to calculate the uncertainty in apparent diffusion coefficient (σADC) voxel-wise measurements to clinically impact the monitoring of treatment response and improve the quality of ADC maps. Materials and methodsWe use a uniquely designed diffusion-weighted imaging (DWI) acquisition protocol that provides gold-standard measurements of σADC to train a deep learning model on two separate cohorts: 16 patients with prostate cancer and 28 patients with mesothelioma. Our network was trained with a novel cost function, which incorporates a perception metric and a b-value regularisation term, on ADC maps calculated by combinations of 2 or 3 b-values (e.g. 50/600/900, 50/900, 50/600, 600/900 s/mm2). We compare the accuracy of the deep-learning based approach for estimation of σADC with gold-standard measurements. ResultsThe model accurately predicted the σADC for every b-value combination in both cohorts. Mean values of σADC within areas of active disease deviated from those measured by the gold-standard by 4.3% (range, 2.87–6.13%) for the prostate and 3.7% (range, 3.06–4.54%) for the mesothelioma cohort. We also showed that the model can easily be adapted for a different DWI protocol and field-of-view with only a few images (as little as a single patient) using transfer learning. ConclusionDeep learning produces maps of σADC from standard clinical diffusion-weighted images (DWI) when 2 or more b-values are available.

Measurements of binary diffusion coefficient for platinum(II) acetylacetonate in high temperature supercritical carbon dioxide by the chromatographic impulse response method

Infinite dilution binary diffusion coefficients D12 and retention factors k for platinum(II) acetylacetonate in high temperature supercritical carbon dioxide (scCO2), at temperatures from (323.3–454.2) K and pressures from (11.0–25.0) MPa, were measured by the chromatographic impulse response method. Although diffusion coefficients for various compounds up to 353 K in scCO2 reported in the literature were well represented by the hydrodynamic equation, the present data deviated more from the equation as the CO2 viscosity decreased. The deviating D12 data corresponded to the gas-like scCO2 region whose conditions were situated below the density fluctuation ridge line on the pressure (or density) − temperature phase diagram, as observed for Cr(acac)3 measured in the authors’ previous study. All the present D12 data and those previously measured below 343 K over the entire region from gas-like to liquid-like scCO2 were well represented by the Schmidt number correlation over the temperature range from 308.2 K to 454.2 K with an average relative deviation (ARD) of 6.5% for 109 measurement conditions. The retention factors measured in the present study were correlated with CO2 density, with temperature dependent constants having an ARD of 4.4% for 47 measurement conditions.

Measurement of the molecular diffusion coefficient and the effective longitudinal diffusion under supercritical fluid chromatography conditions in packed bed columns

The improvement of supercritical fluid chromatography (SFC) instrumentation enhanced its reliability and utility over the past decade. The further development of high speed and high resolution separations is however obstructed by the lack of accurate models for axial dispersion in SFC. This work is a first step to tackle this by developing more reliable methods to measure molecular (Dmol) and longitudinal diffusion (Deff) in SFC, as these affect all aspects of separation efficiency. In the present contribution, we report on an improved method, to enable more flexible, reliable and accurate measurements of Dmol in SFC using commercial instrumentation. A two-column variant of the stopped-flow experiment is proposed as an adapted set-up for measuring the effective longitudinal diffusion coefficient Deff in SFC-conditions. Using the set-ups for a number of test-compounds, it has been found that Deff, and the coefficients describing its constituent sub-processes (cf. particle diffusion Dpart and surface diffusion γsDs), all vary in a linearly proportional way with the bulk diffusion coefficient Dmol within a high degree of accuracy. It has also been found that Deff decreases much more sharply with increasing retention factor compared to LC. By applying the effective medium theory, it was found that the relative surface diffusion coefficient γsDs/Dmol decreases strongly with retention factor for the investigated solutes and column, in contrary to what is typically observed in reversed phase liquid chromatography. Results indicate that this might be related to a change in retention behavior of the analytes. Obviously, more analytes and conditions need to be explored to complete this picture and the extend range of applicability of these observations.

Impact of Adding Mean Apparent Diffusion Coefficient (ADCmean) Measurements to O-RADS MRI Scoring For Adnexal Lesions Characterization: A Combined O-RADS MRI/ADCmean Approach

Evaluate the impact of adding mean apparent diffusion coefficient (ADCmean) measurements to the Ovarian-Adnexal Imaging Reporting and Data System MRI (O-RADS MRI) scoring for adnexal lesion characterization using a combined O-RADS MRI/ADCmean reading approach. This prospective study included 90 women who underwent pelvic MRI for adnexal lesions diagnosis and characterization. Two readers scored the adnexal lesions using the O-RADS MRI scoring independently and in consensus. A third reader calculated ADCmean measurements. The final diagnoses were determined by histo-pathology (n = 77) or follow-up imaging (n = 13). Areas under the curves (AUCs) and diagnostic performance metrics were calculated for the O-RADS MRI scoring, ADCmean, and combined O-RADS MRI/ADCmean thresholds. P-value <0.05 was significant. 116 adnexal lesions (71 benign, 45 malignant) were analyzed. The optimal thresholds to predict malignant adnexal lesions were O-RADS MRI score >3 and ADCmean value ≤1.08×10-3 mm2/s (AUC 0.926 and 0.823; sensitivity 97.7% and 95.5%; specificity 87.3% and 68%; positive predictive value (PPV) 83% and 66.2%; positive likelihood ratio (PLR) 7.7 and 3.08, respectively). Compared to the O-RADS MRI scoring, a combined threshold of O-RADS MRI >3/ADCmean ≤1.08×10-3 mm2/s, yielded a reduction of false positives, a significant increase in the specificity (97.1%, p=0.005), PPV (95.4%, p=0.002), and PLR (33.1, p <0.0001), and non-significant change in the AUC (0.953, p=0.252), and sensitivity (93.3%, p=0.467). The diagnostic performance of O-RADS MRI scoring to characterize adnexal lesions could be improved by adding the ADCmean values through reducing false positives, increasing specificity, and maintaining good sensitivity.

Non-destructive characterization of proton diffusion coefficient within live electroactive biofilm

As the foundation stone of bioelectrochemical systems (BESs), the maintenance of electroactive biofilm with good metabolic activity is essential to achieve high and stable performance. Since proton transport has significant impacts on the biofilm metabolic activity through the microenvironment pH, the investigation of proton transfer properties interior the biofilms is crucial for enhancing BES performance. Herein, the proton transport in electroactive biofilms is explored by in situ microelectrode measurements. It achieves a methodological innovation for measuring the diffusion coefficient in live biofilm under non-destructive conditions. The non-destructive measurement of diffusion coefficients in situ not only bring the results more closely to reality, but also enriches the knowledge of biochemical processes occurring and physicochemical information. Combined with the mass transport and electricity production mathematical model, it is demonstrated that the accumulation of protons in biofilm is a key factor in inhibiting the electricity generation. The efficient characterization of proton transfer interior the biofilm provides a realistic guidance for the construction high performance BES.

Role of apparent diffusion coefficient measurement in differentiating histological subtypes of brain metastasis of lung cancer

SUMMARYOBJECTIVE:The aim of this study was to investigate the role of apparent diffusion coefficient of diffusion-weighted imaging in differentiating histological subtypes of brain metastasis of lung cancer.METHODS:Diffusion-weighted imaging of 158 patients (mean age: 61.2±10.68 years) with brain metastasis of lung cancer (36 small cell lung cancer and 122 non-small cell lung cancer) were retrospectively evaluated. The minimum and mean apparent diffusion coefficient values of the metastasis, apparent diffusion coefficient of edema around the metastasis, and apparent diffusion coefficient of contralateral brain parenchyma were measured. Normalized apparent diffusion coefficient was calculated by proportioning the mean apparent diffusion coefficient of the metastasis to the apparent diffusion coefficient of the contralateral brain parenchyma. Minimum and mean apparent diffusion coefficient of the metastasis, apparent diffusion coefficient of edema around metastasis, and normalized apparent diffusion coefficient were compared between small cell lung cancer and non-small cell lung cancer metastases.RESULTS:Minimum apparent diffusion coefficient, mean apparent diffusion coefficient, and normalized apparent diffusion coefficient values of small cell lung cancer metastases (0.43±0.19×10−3mm2/s, 0.63±0.20×10−3mm2/s, and 0.81 [0.55–1.44], respectively) were significantly lower than those of non-small cell lung cancer metastases (0.71±0.26×10−3mm2/s, 0.93±0.29×10−3mm2/s, and 1.30 [0.60–3.20], respectively; p<0.001). Mean apparent diffusion coefficient of edema of small cell lung cancer metastases (1.21±0.28×10−3mm2/s) was significantly lower than that of non-small cell lung cancer metastases (1.39±0.26×10−3mm2/s, p=0.020). The best cutoff values of minimum apparent diffusion coefficient, mean apparent diffusion coefficient, normalized apparent diffusion coefficient, and apparent diffusion coefficient of edema for the differentiation of small cell lung cancer and non-small cell lung cancer were found to be 0.56×10−3mm2/s, 0.82×10−3mm2/s, 1.085, and 1.21×10−3mm2/s, respectively. The area under the receiver operating characteristic curve, sensitivity, and specificity values were, respectively, 0.812, 80.6, and 73.8% for minimum apparent diffusion coefficient; 0.825, 91.7, and 61.5% for mean apparent diffusion coefficient; 0.845, 80.6, and 73.8% for normalized apparent diffusion coefficient; and 0.698, 75.0, and 67.7% for apparent diffusion coefficient of edema.CONCLUSIONS:Minimum apparent diffusion coefficient, mean apparent diffusion coefficient, normalized apparent diffusion coefficient, and apparent diffusion coefficient of edema around metastasis can differentiate histological subtypes of brain metastasis of lung cancer.

MRI: Evaluating the Application of FOCUS-MUSE Diffusion-Weighted Imaging in the Pancreas in Comparison With FOCUS, MUSE, and Single-Shot DWIs.

Diffusion-weighted imaging (DWI) is a useful technique to detect pancreatic lesion. In DWIs, field-of-view optimized and constrained undistorted single-shot (FOCUS) can improve the spatial resolution and multiplexed sensitivity-encoding (MUSE) can gain a high signal-to-noise ratio (SNR). Based on the advantage of FOCUS and MUSE, a new DWI sequence-named FOCUS-MUSE DWI (FOCUS combined with MUSE)-was developed to delineate the pancreas. To investigate the reliability of FOCUS-MUSE DWI compared to FOCUS, MUSE and single-shot (SS) DWI via the systematical evaluation of the apparent diffusion coefficient (ADC) measurements, SNR and image quality. Prospective. A total of 33 healthy volunteers and 9 patients with pancreatic lesion. A 3.0 T scanner. FOCUS-MUSE DWI, FOCUS DWI, MUSE DWI, SS DWI. For volunteers, ADC and SNR were measured by two readers in the pancreatic head, body, and tail. For all subjects, the diagnostic image quality score was assessed by three other readers on above four DWIs. Paired-sample T-test, intraclass correlation (ICC), Bland-Altman method, Friedman test, Dunn-Bonferroni post hoc test and kappa coefficient. A significance level of 0.05 was used. FOCUS-MUSE DWI had the best intersession repeatability of ADC measurements (head: 59.53, body: 101.64, tail: 42.30) among the four DWIs, and also maintained the significantly highest SNR (reader 1 [head: 19.68 ± 3.23, body: 23.42 ± 5.00, tail: 28.85 ± 4.96], reader 2 [head: 19.93 ± 3.52, body: 23.02 ± 5.69, tail: 29.77 ± 6.33]) except for MUSE DWI. Furthermore, it significantly achieved better image quality in volunteers (median value: 4 score) and 9 patients (most in 4 score). FOCUS-MUSE DWI improved the reliability of pancreatic images with the most stable ADC measurement, best image quality score and sufficient SNR among four DWIs. 2 TECHNICAL EFFICACY: Stage 2.

Diffusion-weighted and gadolinium-enhanced dynamic MRI in parotid gland tumors.

To evaluate the value of diffusion-weighted imaging and dynamic contrast-enhanced MRI for the diagnosis of parotid gland tumors. Retrospective review of patients with surgically treated parotid tumors between January 2009 and June 2020, who underwent a preoperative parotid gland MRI including standard morphological sequences, diffusion-weighted echoplanar imaging with apparent diffusion coefficient measurement and T1-weighted gadolinium-enhanced dynamic MRI sequences with Fat Saturation. The lesion was classified between malignant vs benign and precisions regarding its histological type were given when possible. Imaging findings were compared with pathology results. Inclusion of 133 patients (mean age: 53years). Multiparametric MRI had a sensitivity of 90.3%, a specificity of 77.5%, an overall accuracy of 80.5%, a positive predictive value of 54.9% and a negative predictive value of 96.3% to differentiate benign parotid tumor from malignant ones. Specificity (85.5%) and positive predictive value (67.6%) were improved for cases, where anatomical and functional MRI characteristics were conclusive and consistent with clinical findings. Combining diffusion-weighted and gadolinium-enhanced dynamic sequences, in addition to morphological ones enables high (> 90%) sensitivity to detect malignant parotid gland tumors. It also gives the possibility to characterize pleomorphic adenomas and Warthin tumors and to avoid fine-needle aspiration in cases of typical imaging presentation and reassuring clinical findings.