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Purpose: Tensor-valued diffusion encoding can probe more specific features of tissue microstructure than what is available by conventional diffusion weighting. In this work, we investigate the technical feasibility of tensor-valued diffusion encoding at high b-values with q-space trajectory imaging (QTI) analysis, in the human heart in vivo. Methods: Ten healthy volunteers were scanned on a 3T scanner. We designed time-optimal gradient waveforms for tensor-valued diffusion encoding (linear and planar) with second-order motion compensation. Data were analyzed with QTI. Normal values and repeatability were investigated for the mean diffusivity (MD), fractional anisotropy (FA), microscopic FA (μFA), isotropic, anisotropic and total mean kurtosis (MKi, MKa, and MKt), and orientation coherence (Cc). A phantom, consisting of two fiber blocks at adjustable angles, was used to evaluate sensitivity of parameters to orientation dispersion and diffusion time. Results: QTI data in the left ventricular myocardium were MD = 1.62 ± 0.07 μm2/ms, FA = 0.31 ± 0.03, μFA = 0.43 ± 0.07, MKa = 0.20 ± 0.07, MKi = 0.13 ± 0.03, MKt = 0.33 ± 0.09, and Cc = 0.56 ± 0.22 (mean ± SD across subjects). Phantom experiments showed that FA depends on orientation dispersion, whereas μFA was insensitive to this effect. Conclusion: We demonstrated the first tensor-valued diffusion encoding and QTI analysis in the heart in vivo, along with first measurements of myocardial μFA, MKi, MKa, and Cc. The methodology is technically feasible and provides promising novel biomarkers for myocardial tissue characterization.

Purpose Rapid acquisition scheme and parameter estimation method are proposed to acquire distortion-free spin- and stimulated-echo signals and combine the signals with a physics-driven unsupervised network to estimate T-1, T-2, and proton density (M-0) parameter maps, along with B-0 and B-1 information from the acquired signals. Theory and Methods An imaging sequence with three 90 degrees RF pulses is utilized to acquire spin- and stimulated-echo signals. We utilize blip-up/-down acquisition to eliminate geometric distortion incurred by the effects of B-0 inhomogeneity on rapid EPI acquisitions. For multislice imaging, echo-shifting is applied to utilize dead time between the second and third RF pulses to encode information from additional slice positions. To estimate parameter maps from the spin- and stimulated-echo signals with high fidelity, 2 estimation methods, analytic fitting and a novel unsupervised deep neural network method, are developed. Results The proposed acquisition provided distortion-free T-1, T-2, relative proton density (M0), B-0, and B-1 maps with high fidelity both in phantom and in vivo brain experiments. From the rapidly acquired spin- and stimulated-echo signals, analytic fitting and the network-based method were able to estimate T-1, T-2, M-0, B-0, and B-1 maps with high accuracy. Network estimates demonstrated noise robustness owing to the fact that the convolutional layers take information into account from spatially adjacent voxels. Conclusion The proposed acquisition/reconstruction technique enabled whole-brain acquisition of coregistered, distortion-free, T-1, T-2, M-0, B-0, and B-1 maps at 1 x 1 x 5 mm(3) resolution in 50 s. The proposed unsupervised neural network provided noise-robust parameter estimates from this rapid acquisition.

Purpose To implement a free-breathing sequence for simultaneous quantification of T 1 , T 2 , and T 2 ∗ for comprehensive tissue characterization of the myocardium in a single scan using a multi-gradient-echo readout with saturation and T 2 preparation pulses. Methods In the proposed Saturation And T 2 -prepared Relaxometry with Navigator-gating (SATURN) technique, a series of multi-gradient-echo (GRE) images with different magnetization preparations was acquired during free breathing. A total of 35 images were acquired in 26.5 ± 14.9 seconds using multiple saturation times and T 2 preparation durations and with imaging at 5 echo times. Bloch simulations and phantom experiments were used to validate a 5-parameter fit model for accurate relaxometry. Free-breathing simultaneous T 1 , T 2 , and T 2 ∗ measurements were performed in 10 healthy volunteers and 2 patients using SATURN at 3T and quantitatively compared to conventional single-parameter methods such as SASHA for T 1 , T 2 -prepared bSSFP, and multi-GRE for T 2 ∗ . Results Simulations confirmed accurate fitting with the 5-parameter model. Phantom measurements showed good agreement with the reference methods in the relevant range for in vivo measurements. Compared to single-parameter methods comparable accuracy was achieved. SATURN produced in vivo parameter maps that were visually comparable to single-parameter methods. No significant difference between T 1 , T 2 , and T 2 ∗ times acquired with SATURN and single-parameter methods was shown in quantitative measurements (SATURN T 1 = 1573 ± 86 ms , T 2 = 33.2 ± 3.6 ms , T 2 ∗ = 25.3 ± 6.1 ms ; conventional methods: T 1 = 1544 ± 107 ms , T 2 = 33.2 ± 3.6 ms , T 2 ∗ = 23.8 ± 5.5 ms ; P > . 2 ) CONCLUSION: SATURN enables simultaneous quantification of T 1 , T 2 , and T 2 ∗ in the myocardium for comprehensive tissue characterization with co-registered maps, in a single scan with good agreement to single-parameter methods.

BACKGROUND AND OBJECTIVES To determine the efficacy of targeted fluorescent biomarkers and multiphoton imaging to characterize early changes in ovarian tissue with the onset of cancer. STUDY DESIGN/MATERIALS AND METHODS A transgenic TgMISIIR-TAg mouse was used as an animal model for ovarian cancer. Mice were injected with fluorescent dyes to bind to the folate receptor α, matrix metalloproteinases, and integrins. Half of the mice were treated with 4-vinylcyclohexene diepoxide (VCD) to simulate menopause. Widefield fluorescence imaging (WFI) and multiphoton imaging of the ovaries and oviducts were conducted at 4 and 8 weeks of age. The fluorescence signal magnitude was quantified, and texture features were derived from multiphoton imaging. Linear discriminant analysis was then used to classify mouse groups. RESULTS Imaging features from both fluorescence imaging and multiphoton imaging show significant changes (P

A key advantage of cardiac magnetic resonance (CMR) imaging over other cardiac imaging modalities is the ability to perform detailed tissue characterization. CMR techniques continue to evolve, with advanced imaging sequences being developed to provide a reproducible, quantitative method of tissue interrogation. The T1 mapping technique, a pixel-by-pixel method of quantifying T1 relaxation time of soft tissues, has been shown to be promising for characterization of diseased myocardium in a wide variety of cardiomyopathies. In this review, we describe the basic principles and common techniques for T1 mapping and its use for native T1 , postcontrast T1 , and extracellular volume mapping. We will review a wide range of clinical applications of the technique that can be used for identification and quantification of myocardial edema, fibrosis, and infiltrative diseases with illustrative clinical examples. In addition, we will explore the current limitations of the technique and describe some areas of ongoing development. Level of Evidence: 5 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:1336-1356.

Purpose To present a stimulated-echo based mapping (STEM) approach for simultaneous T1 , T2 , and ADC mapping. Methods Diffusion-weighted stimulated-echo images with various combinations of mixing time (TM), TE, and b-value were acquired to enable simultaneous mapping of T1 , T2 , and ADC. The proposed STEM method was performed by densely sampling the TM-TE-b space in a phantom and in brain and prostate of healthy volunteers. T1 , T2 , and ADC from STEM were compared to reference mapping methods. Additionally, protocol optimization was performed to enable rapid STEM acquisition within 2 min by sparsely sampling the TM-TE-b space. The T1 , T2 , and ADC measurements from rapid acquisitions were compared to the densely sampled STEM for evaluation. Finally, a patient with biopsy-proven high-risk prostate cancer was imaged to demonstrate the ability of STEM to differentiate cancer and healthy tissues. Results Relative to the reference measurements, densely sampled STEM provided accurate quantitative T1 , T2 , and ADC mapping in phantoms (R2 = 0.999, slope between 0.97-1.03), as well as in brain and prostate. Further, the T1 , T2 , and ADC measurements from the optimized rapid STEM acquisitions agreed closely with densely sampled STEM. Finally, STEM showed decreased T2 and ADC in prostate cancer compared to healthy prostate tissue. Conclusion STEM provides accurate simultaneous mapping of T1 , T2 , and ADC. This method may enable rapid and accurate multi-parametric tissue characterization for clinical and research applications.

Background Diminished signal intensity of uterine fibroids in T2 -weighted images is routinely used as a qualitative marker of fibroid hypoperfusion. However, quantitative classification of fibroid perfusion with intravoxel incoherent motion (IVIM) model-based metrics is not yet clinically accepted. Purpose To investigate the influence of T2 correction on the estimation of IVIM model parameters for characterizing uterine fibroid tissue. Study type Prospective. Population Fourteen women with 41 fibroids (12 Type I and 29 Type II, per Funaki classification) underwent diffusion-weighted imaging and T2 mapping. Field strength Diffusion-weighted images (b values: 0, 20, 40, 60, 100, 200, 400, 600, 800, 1000 s/mm2 ) and T2 maps were obtained at 1.5T. Assessment The effect of uterine fibroid T2 variation on IVIM model parameters (diffusion coefficient, perfusion coefficient, and perfusion volume fraction) were numerically modeled and experimentally evaluated without (D, D*, f) and with (Dc , D c * , fc ) T2 correction. The relationship of T2 with D and the T2 -corrected perfusion volume fraction (fc ) was also examined. Statistical test D-values and f-values estimated with and without T2 correction were compared by using a two-tailed Student's t-test. Results Type II fibroids had higher D and f than Type I fibroids, but the differences were not significant (Type I vs. Type II, D: 0.83 ± 0.20 vs. 0.80 ± 0.25 mm2 /s, P = 0.78; f: 23.64 ± 4.87% vs. 25.27 ± 7.46%, P = 0.49). For Type I and Type II fibroids, fc was lower than f, and fc of Type II fibroids was significantly higher than that of Type I fibroids (Type I vs. Type II, fc : 7.80 ± 1.88% vs. 11.82 ± 4.13%, P = 0.003). Both D and fc exponentially increased with the increase of fibroid T2 as functions: D c ( T 2 ) = - 1.52 × 10 - 3 ⋅ e - 3.42 T 2 290 + 1.84 × 10 - 3 and f c ( T 2 ) = - 0.2336 ⋅ e - 3.217 T 2 290 + 0.2269 , respectively. D asymptotically approached 1.79 × 10-3 mm2 /s, and fc approached 21.74%. Data conclusion T2 correction is important when using IVIM-based models to characterize uterine fibroid tissue. Level of evidence 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;48:994-1001.

Ultrasound tissue characterization (UTC) is an imaging tool used to quantify tendon structural integrity. UTC has quantified Achilles tendon (AT) acute response to load in athletes; however, AT response to cumulative load over a season is unknown. The purpose of this study was to evaluate AT response across a four-month competitive season in collegiate cross-country (XC) runners. Participants (n=21; male=9, female=12; age=19.8±1.2 years; height=171.9±8.9 cm; weight=60.2±8.5 kg) were imaged using the UTC device with a 10-MHz linear-array transducer mounted in a tracking device. The device captures images at 0.2 mm intervals along the AT. UTC algorithms quantified the stability of pixel brightness over every 17 contiguous transverse images into four echo types (I-IV). A total of 168 scans (n=21, bilateral limbs) were performed monthly across the four-month season (Aug=M1, Sep=M2, Oct=M3, Nov=M4). Echo-type percentages (%) were calculated from each scan. Generalized estimating equations (GEE) linear regression models evaluated echo-type % change (β) over the season (M1=reference). Type I increased from M1 to M4 (β=9.10, P

3D printing facilitates the creation of accurate physical models of patient-specific anatomy from medical imaging datasets. While the majority of models to date are created from computed tomography (CT) data, there is increasing interest in creating models from other datasets, such as ultrasound and magnetic resonance imaging (MRI). MRI, in particular, holds great potential for 3D printing, given its excellent tissue characterization and lack of ionizing radiation. There are, however, challenges to 3D printing from MRI data as well. Here we review the basics of 3D printing, explore the current strengths and weaknesses of printing from MRI data as they pertain to model accuracy, and discuss considerations in the design of MRI sequences for 3D printing. Finally, we explore the future of 3D printing and MRI, including creative applications and new materials. Level of Evidence: 5 J. Magn. Reson. Imaging 2016.

Introduction We assess the ability of low-dose hybrid iterative reconstruction (IR) and ‘pure’ model-based IR (MBIR) images to maintain accurate Hounsfield unit (HU)-determined tissue characterization. Methods Standard-protocol (SP) and low-dose modified-protocol (MP) CTs were contemporaneously acquired in 34 Crohn's disease patients referred for CT. SP image reconstruction was via the manufacturer's recommendations (60% FBP, filtered back projection; 40% ASiR, Adaptive Statistical iterative Reconstruction; SP-ASiR40). MP data sets underwent four reconstructions (100% FBP; 40% ASiR; 70% ASiR; MBIR). Three observers measured tissue volumes using HU thresholds for fat, soft tissue and bone/contrast on each data set. Analysis was via SPSS. Results Inter-observer agreement was strong for 1530 datapoints (rs > 0.9). MP-MBIR tissue volume measurement was superior to other MP reconstructions and closely correlated with the reference SP-ASiR40 images for all tissue types. MP-MBIR superiority was most marked for fat volume calculation – close SP-ASiR40 and MP-MBIR Bland–Altman plot correlation was seen with the lowest average difference (336 cm3) when compared with other MP reconstructions. Conclusions Hounsfield unit-determined tissue volume calculations from MP-MBIR images resulted in values comparable to SP-ASiR40 calculations and values that are superior to MP-ASiR images. Accuracy of estimation of volume of tissues (e.g. fat) using segmentation software on low-dose CT images appears optimal when reconstructed with pure IR.

Recently, ultrasound tissue characterization (UTC) was introduced as a reliable method for quantification of tendon structure. Despite increasing publications on the use of UTC, it is striking that there is a lack of normative data in active adolescents. Therefore, the aim of this study was to provide normative values of the Achilles tendon as quantified by UTC. Seventy physiotherapy students (26 male and 44 female students) with no history of Achilles tendon injuries were recruited. The Achilles tendons were scanned with UTC to characterize tendon structure. This study demonstrated that Achilles tendons of active, healthy adolescents contained 54.6% echo type I, 42.8% echo type II, 2.2% echo type III, and 0.3% echo type IV at midportion. The comparison between insertion and midportion of the tendon showed more echo type II at insertion (P

In this study non-negative matrix factorization (NMF) was hierarchically applied to simulated and in vivo three-dimensional 3 T MRSI data of the prostate to extract patterns for tumour and benign tissue and to visualize their spatial distribution. Our studies show that the hierarchical scheme provides more reliable tissue patterns than those obtained by performing only one NMF level. We compared the performance of three different NMF implementations in terms of pattern detection accuracy and efficiency when embedded into the same kind of hierarchical scheme. The simulation and in vivo results show that the three implementations perform similarly, although one of them is more robust and better pinpoints the most aggressive tumour voxel(s) in the dataset. Furthermore, they are able to detect tumour and benign tissue patterns even in spectra with lipid artefacts. Copyright © 2016 John Wiley & Sons, Ltd.

Purpose The goal of this study was to characterize the accuracy and precision of cardiac T2 mapping as a function of different factors including low signal-to-noise ratio (SNR), imaging in systole, and off-resonance frequencies. Methods Bloch equation and Monte Carlo simulations were used to determine the influence of SNR and the choice of T2 preparation echo time (TET2prep) increments on the accuracy and precision of high-resolution radial cardiac T2 mapping at 3.0 T. Healthy volunteers were scanned to establish the difference in precision and inter- and intraobserver variability between T2 mapping in diastole and systole, as well as the effect of SNR and off-resonance frequencies on the accuracy of T2 maps. Results The simulations demonstrated that a TET2prep increment of ∼0.75 times the T2 value of interest optimally increases the precision of the T2 fit. Systolic T2 maps were found to have a higher precision (P = 0.002), but similar inter- and intraobserver variability compared with diastolic T2 maps, whereas off-resonance frequencies beyond ± 100 Hz cause a significant decrease in both accuracy and precision (P

Structural disorganization in the tendon is associated with tendinopathy, with little research investigating whether disorganization overwhelms the overall structural integrity of the tendon. This study investigated the mean cross-sectional area (CSA) of aligned fibrillar structure as detected by ultrasound tissue characterization (UTC) in the pathological and normal Achilles and patellar tendons. Ninety-one participants had their Achilles and/or patellar tendons scanned using UTC to capture a three-dimensional image of the tendon and allow a semi-quantification of the echopattern. The mean CSA of aligned fibrillar structure (echo type I + II) and disorganized structure (echo type III + IV) was calculated based on UTC algorithms. Each tendon was classified as either pathological or normal based solely on gray-scale ultrasound. The mean CSA of aligned fibrillar structure was significantly greater (P ≤ 0.001) in the pathological tendon compared with the normal tendon, despite the pathological tendon containing greater amounts of disorganized structure (P ≤ 0.001). A significant relationship was observed between the mean CSA of disorganized structure and anteroposterior diameter of the Achilles (R(2) = 0.587) and patellar (R(2) = 0.559) tendons. This study is the first to show that pathological tendons have sufficient levels of aligned fibrillar structure. Pathological tendons may compensate for areas of disorganization by increasing in tendon thickness.

Atherosclerosis is among the most widespread cardiovascular diseases and one of the leading cause of death in the Western World. Characterization of arterial tissue in atherosclerotic condition is extremely interesting from the diagnostic point of view, especially for what is concerning collagen content and organization because collagen plays a crucial role in plaque vulnerability. Routinely used diagnostic methods, such as histopathological examination, are limited to morphological analysis of the examined tissues, whereas an exhaustive characterization requires immune-histochemical examination and a morpho-functional approach. Non-linear microscopy techniques offer the potential for providing morpho-functional information on the examined tissues in a label-free way. In this study, we employed combined SHG and FLIM microscopy for characterizing collagen organization in both normal arterial wall and within atherosclerotic plaques. Image pattern analysis of SHG images allowed characterizing collagen organization in different tissue regions. In addition, the analysis of collagen fluorescence decay contributed to the characterization of the samples on the basis of collagen fluorescence lifetime. Different values of collagen fiber mean size, collagen distribution, collagen anisotropy and collagen fluorescence lifetime were found in normal arterial wall and within plaque depositions, prospectively allowing for automated classification of atherosclerotic lesions and plaque vulnerability. The presented method represents a promising diagnostic tool for evaluating atherosclerotic tissue and has the potential to find a stable place in clinical setting as well as to be applied in vivo in the near future.

Most solid lesions in the female pelvis appearing hyperintense on T2-weighted images should be interpreted as malignant. In contrast, if the solid lesions in the female pelvis appear hypointense on T2-weighted images they may be benign. The characteristic imaging features of hyperintense solid lesions in the female pelvis on T2-weighted images are well known, but various unusual causes and imaging features of hypointense solid lesions in the female pelvis on T2-weighted images can be particularly misleading. Therefore, careful assessment of hypointense solid lesions in the female pelvis on T2-weighted images is warranted. In this article, we demonstrate a variety of hypointense solid lesions in the female pelvis on T2-weighted images. Familiarity with the clinical setting and imaging features of hypointense solid lesions in the female pelvis on T2-weighted images will facilitate prompt, accurate diagnosis and treatment.

Purpose To evaluate the role of magnetic resonance (MR) diffusion-weighted imaging (DWI) in discriminating lacrimal masses, including neoplastic and nonneoplastic entities. Materials and Methods Forty-four patients with lacrimal masses underwent conventional MRI and DWI. The apparent diffusion coefficient (ADC) values of each mass and the ipsilateral temporal lobe were measured and the ratios of the lesion to temporal lobe ADC were calculated. Results Pleomorphic adenomas had significantly higher ADC values (1.37 ± 0.22 × 10−3 mm2/sec) and ADC ratios (1.85 ± 0.34) than malignant tumors (1.03 ± 0.19 × 10−3 mm2/sec, 1.37 ± 0.27) (P < 0.001), inflammatory pseudotumors (0.9 ± 0.08 × 10−3 mm2/sec, 1.19 ± 0.07) (P < 0.01), reactive lymphoid hyperplasias (RLHs) (0.6 ± 0.06 × 10−3 mm2/sec, 0.79 ± 0.07) (P < 0.001), and lymphomas (0.55 ± 0.06 × 10−3 mm2/sec, 0.74 ± 0.08) (P < 0.001). RLHs and lymphomas had significantly lower ADC values and ADC ratios than malignant tumors (P < 0.05) and inflammatory pseudotumors (P < 0.05). An ADC value of less than 1.14 × 10−3 mm2/sec and an ADC ratio of less than 1.6 were optimal for differentiating malignant tumors from benign tumors (sensitivity: 80 and 90%, specificity: 100 and 88.9%, respectively). An ADC value of less than 0.76 × 10−3 mm2/sec and an ADC ratio of less than 1.0 were optimal for distinguishing lymphoproliferative disorders from inflammatory pseudotumors (sensitivity: 100%, specificity: 100% for both). Conclusion DWI can help differentiate lacrimal masses and provides a potential clinical tool for noninvasive tissue characterization. J. Magn. Reson. Imaging 2014;40:641–648. © 2013 Wiley Periodicals, Inc.

Purpose To investigate the feasibility of improving MRI R2* mapping by filtering the images before curve-fitting. Methods Pixel-by-pixel curve-fitting for the quantification of MRI relaxometry remains a challenge for low signal-to-noise ratio images. By computing the weighted mean of spatially adjacent pixels, the low-pass Gaussian (LPG) filter can suppress the noise but at the expense of blurring. By assigning high weights to pixels with similar neighborhood patches, the nonlocal means (NLM) algorithm can reduce noise while retaining intrinsic signals, however, its potential has not been explored in pixel-by-pixel MRI relaxometry, and in this study, we aimed to investigate the impact of the LPG and the NLM filtering on decay signals and MRI R2* mapping. These two filtering methods were compared on both simulated and in vivo data. Results Both LPG and NLM algorithms produces R2* maps with decreased root-mean-square-errors. The LPG filter blurs edges of R2* maps while the NLM algorithm preserves details well. The NLM consistently yields R2* mapping with smaller errors than the LPG filtering in all cases. Conclusion Pixel-by-pixel fitting can skew MRI relaxometry. The NLM outperforms the conventional LPG filter and has the potential to provide more accurate pixel-by-pixel MRI relaxometry for improved tissue characterization. Magn Reson Med 72:260–268, 2014. © 2013 Wiley Periodicals, Inc.

Purpose Quantitative mapping of the native T1 of the heart using the modified look-locker inversion recovery (MOLLI) technique provides high quality diagnostic information without requiring contrast agents. Previous work has considered the effects of T2 relaxation on MOLLI T1 measurements, finding that the T1 measured by MOLLI is biased, and that Saturation-recovery single-Shot Acquisition generates a more precise T1. However, despite detailed experiments and simulation the exact relaxation times observed in vivo remain unexplained, but might be due to magnetization transfer (MT). Methods We used an MT simulation based on the Bloch-McConnell equations to evaluate the most common MOLLI and saturation-recovery single-shot acquisition sequence variants. Results For myocardial tissue we find that the T1 measured by saturation-recovery single-shot acquisition is insensitive to MT and T2, whereas MT reduces the T1 measured by MOLLI (>10%) in addition to the effects due to T2 relaxation. Conclusions The consequences of this T1 underestimation by MOLLI are relevant. Increases in the actual T1 and T2 and decreases in MT will all result in an increase in T1 measured by MOLLI. Myocardial infarction demonstrates increased native T1 and T2 and decreased MT, indicating that these biases enhance the sensitivity of MOLLI to detect this and possibly other cardiovascular disease states. Magn Reson Med 70:664–670, 2013. © 2013 Wiley Periodicals, Inc.

Objectives To investigate differences in tissue characterization using three-dimensional sonographic mean gray value (MGV) between retrocervical and rectosigmoid deeply infiltrating endometriosis, and to assess intra- and interobserver concordance in MGV quantification. Methods In this retrospective study, stored ultrasound volumes from 50 premenopausal women (mean age, 32 years) with 57 histologically confirmed nodules of deep endometriosis were retrieved from our database for analysis. A single experienced operator had acquired all volumes. For each nodule, the MGV was evaluated using Virtual Organ Computer-aided AnaLysis (VOCAL) software with semiautomated sphere-sampling (1 cm3) from the central part of the nodule. In these patients the MGV was also quantified from the myometrium of the fundal part of the uterus. In addition, two observers calculated the MGV in a subset of 24 volumes in order to quantify inter- and intraobserver agreement using intraclass correlation coefficients (ICC). Results Mean MGV was significantly higher in rectosigmoid nodules (n = 34) than in nodules with a retrocervical location (n = 23) (23.863 vs 17.705; P 0.95). Conclusions Retrocervical and rectosigmoid endometriotic nodules display significantly different MGVs. Measurement of MGV is highly reproducible and its clinical value in the diagnosis and assessment of distribution of deep endometriosis should be assessed in future studies. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.

Purpose The diffusion tensor model assumes Gaussian diffusion and is widely applied in cardiac diffusion MRI. However, diffusion in biological tissue deviates from a Gaussian profile as a result of hindrance and restriction from cell and tissue microstructure, and may be quantified better by non-Gaussian modeling. The aim of this study was to investigate non-Gaussian diffusion in healthy and hypertrophic hearts. Methods Thirteen rat hearts (five healthy, four sham, four hypertrophic) were imaged ex vivo. Diffusion-weighted images were acquired at b-values up to 10,000 s/mm2. Models of diffusion were fit to the data and ranked based on the Akaike information criterion. Results The diffusion tensor was ranked best at b-values up to 2000 s/mm2 but reflected the signal poorly in the high b-value regime, in which the best model was a non-Gaussian “beta distribution” model. Although there was considerable overlap in apparent diffusivities between the healthy, sham, and hypertrophic hearts, diffusion kurtosis and skewness in the hypertrophic hearts were more than 20% higher in the sheetlet and sheetlet-normal directions. Conclusion Non-Gaussian diffusion models have a higher sensitivity for the detection of hypertrophy compared with the Gaussian model. In particular, diffusion kurtosis may serve as a useful biomarker for characterization of disease and remodeling in the heart. Magn Reson Med, 2016. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Background Secure grasping and effective manipulation of delicate large organs during robotic surgery operations needs especially designed instruments that can enclose a large amount of tissue and feed back the pinch forces. Methods A large organ triple-jaw grasper was instrumented using practical force sensory and actuating systems. A force tracking scheme was proposed to facilitate auto-grasping of large organs during robotic teleoperation surgery. An on-site force commanding/reflecting mechanism was also implemented to use the device as an independent hand-held robotic instrument. The efficacy of the robotic grasper was examined in phantom tests. Results The instrument grasped large soft objects effectively and safely with accurately measured and controlled pinch forces. Furthermore, it could characterize the overall mechanical behavior of the grasping objects. Conclusions The instrument designed provides a potential solution for the safe and effective grasping and manipulation of large abdominal organs, either as a hand-held device, or in a teleoperation framework. Copyright © 2012 John Wiley & Sons, Ltd.

Intravascular imaging plays a key role in the identification of mechanisms of acute coronary syndromes Post processing IVUS algorithms (IMAP-IVUS and VH-IVUS) for tissue characterization have not been widely adopted due to current limitations Future development will allow easier, faster, and more accurate identification of vulnerable plaques, ultimately allowing prognostication of various interventions.

Background Currently, most of mitral valve annuloplasty surgeries are performed by using open heart surgery. However, if such operation would be performed by using minimally invasive surgery via catheter-based techniques (CBT), it offers various advantages for both surgeons and patients. Methods Two piezoresistive force sensors are used in the structure of the tactile sensor, which can easily be miniaturized and integrated into surgical catheters. The tactile sensor was fabricated and tested to characterize different elastomers, as the phantom of cardiac tissues. Based on a developed finite element analysis (FEA) of the elastomers, the interaction between the sensor and those materials were modelled to validate the output of the sensor. Results The results of the mechanical and psychophysical tests confirm the capability of the proposed sensor to measure the relative hardness/softness of different soft tissues. Conclusions The proposed tactile sensor will help surgeons to characterize different types of cardiac tissues and would facilitate the use of CBT to perform mitral valve annuloplasty. Copyright © 2011 John Wiley & Sons, Ltd.

A fast and robust methodology for in vivo T2 mapping is presented. The approach is based on the partially spoiled steady state free precession technique recently proposed by Bieri et al. (Magn Reson Med 2011). The accuracy of this method was demonstrated in simulations and phantom experiments. Variations in skeletal muscle T2 relaxation time have been correlated with cell damage and inflammatory response. Nonetheless, the lack of easily implementable, fast, accurate and reproducible methods has hampered the adoption of T2 measurement as a noninvasive tool for skeletal muscle characterization. The applicability of the partially spoiled steady state free precession method for tissue characterization in muscle disease is illustrated in this work by several examples. Quantitative MRI, in particular T2 mapping based on partially spoiled steady state free precession acquisitions, might provide objective markers of muscle damage and degenerative changes, and an alternative to serial muscle biopsies. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.

Tissue‐depolarization and linear‐retardance are the main polarization characteristics of interest for bulk tissue characterization, and are normally interpreted from Mueller polarimetry. Stokes polarimetry can be conducted using simpler instrumentation and in a shorter time. Here, we use Stokes polarimetric imaging with circularly polarized illumination to assess the circular‐depolarization and linear‐retardance properties of tissue. Results obtained were compared with Mueller polarimetry in transmission and reflection geometry, respectively. It is found that circular‐depolarization obtained from these 2 methods is very similar in both geometries, and that linear‐retardance is highly quantitatively similar for transmission geometry and qualitatively similar for reflection geometry. The majority of tissue circular‐depolarization and linear‐retardance image information (represented by local image contrast features) obtained from Mueller polarimetry is well preserved from Stokes polarimetry in both geometries. These findings can be referred to for further understanding tissue Stokes polarimetric data, and for further application of Stokes polarimetry under the circumstances where short acquisition time or low optical system complexity is a priority, such as polarimetric endoscopy and microscopy.

Summary Single voxel magnetic resonance spectroscopy (MRS) has been the standard in human breast tumour studies published to date. This method is hampered by the impossibility to study tissue heterogeneity or compare the metabolite signals in breast lesion directly to those in unaffected tissue. Multivoxel MRS studies, frequently referred to as spectroscopic imaging, while potentially allowing for truly quantitative tissue characterization, have up to now also been far from quantitative with, for example, the signal-to-noise ratio of the choline (Cho) signal serving as a measure of tumour activity. Demonstrated in this study is that in a standard clinical setting with a regular 1.5 T MR scanner, it is possible to perform quantitative multivoxel MRS. Using a pre-measurement to map the distributions of water and fat, and literature values for the T1 and T2 relaxation times of Cho and water in fibroglandular breast tissue and tumours, one can determine the concentrations of Cho in different tumour compartments and surrounding tissues in two brief multivoxel MRS measurements. Quantitative diagnostic and follow-up studies of focal breast pathology are now possible.

We analyze localized textural consistencies in high-resolution X-ray (computed tomography) CT scans of coronary arteries to identify the appearance of diagnostically relevant changes in tissue. For the efficient and accurate processing of CT volume data, we use fast wavelet algorithms associated with three-dimensional isotropic multiresolution wavelets that implement a redundant, frame-based image encoding without directional preference. Our algorithm identifies textural consistencies by correlating coefficients in the wavelet representation.

The purpose of this review is to discuss the principles of ultrasound tissue characterization. We describe gray scale analysis, backscatter techniques, real-time backscatter imaging, enhancement of abnormal tissue properties with contrast agents or liposomes, and use of acoustic microscopy. Ultrasound tissue characterization offers the promise of direct identification of abnormalities of the myocardium without relying on indirect manifestations such as abnormalities in cardiac function. (ECHOCARDIOGRAPHY, Volume 8, January 1991)

In cardiac amyloidosis an interstitial deposition of amyloid fibrils causes concentric thickening of the atrial and ventricular walls. We describe the results of tissue characterization of the myocardium by T1 quantification and MRI findings in a patient with cardiac amyloidosis. The T1 time of the myocardium was elevated compared to that in individuals without amyloidosis. The T1 time of the myocardium was 1387 +/- 63 msec (mean value obtained from four measurements +/- standard deviation [SD]) in the patient with cardiac amyloidosis, while the reference value obtained from the myocardium of 10 individuals without known myocardial disease was 1083 +/- 33 msec (mean value +/- SD). In combination with other MR findings suggestive of amyloidosis, such as homogeneous thickening of the ventricular and atrial walls, thickening of the valve leaflets, restrictive filling pattern, and reduction of systolic function, T1 quantification may increase diagnostic confidence.

Objective. The purpose of this study was to investigate the value of integrated backscatter (IBS) of kidneys in acute organophosphorus compound poisoning in rabbits. Methods. Eighteen rabbits were poisoned by dimethyl dichlorovinyl phosphate to establish animal models. Sonographic examinations were performed before (To) and after (T 1 -T 9 ) the rabbits were poisoned. The echo and size of kidneys were evaluated by 2-dimensional gray scale sonography. Changes of the renal cortex and medulla were analyzed quantitatively with IBS. Results. No change of the cortex echo was found before and after poisoning. A significant change of the volume of kidneys on both sides began at T 6 compared with that at To (P

Rapid MR elastography (MRE) techniques using spatially-selective excitations to reduce acquisition times to a few seconds or less were devised and tested. The techniques included reduced field of view (rFOV) MRE and 1D MRE (beam MRE) using 2D spatially selective RF excitations for gradient-echo (GRE) applications and intersecting 90° and 180° slice-selective excitations for spin-echo (SE) applications. It was shown that scan times could be reduced by a factor of 8 using rFOV MRE, and by 64 using beam MRE, while still obtaining stiffness estimates comparable to full-FOV MRE. Results were shown in gel phantom experiments as well as in the case of a preserved postmortem breast tissue specimen with a stiff lesion. These methods can be used to more rapidly interrogate regions of interest (ROIs) in tissue to quickly obtain information about the viscoelastic properties of that tissue. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc.

Summary Intracranial abscesses and metastases are common lesions that might not be differentiated on routine MRI alone. In vivo proton spectroscopy and diffusion-weighted imaging have been used as complementary investigations for improved tissue characterization. In the present report we illustrate the role of mucin and its contribution to signal characteristics on diffusion-weighted imaging in a metastatic mucinous adenocarcinoma.

We are investigating the utility of a new ultrasonic tissue characterization technique, specifically two-dimensional (2-D) spectrum analysis of radio-frequency backscatter signals, which promises to provide quantitative measures of the physical properties of tissue microstructures. Previously successful 1-D spectrum analysis is expanded to 2-D to more fully characterize diagnostically significant features of biological tissue. Two new spectral functions, radially integrated spectral power (RISP) and angularly integrated spectral power (AISP), are defined to quantitatively characterize tissue properties. This new approach is applied to the diagnosis of in vivo ocular melanomas. Our initial results indicate that 2-D spectrum analysis can provide significant new information on tissue anisotropy that are not apparent in 1-D spectra. Acoustic scattering models are applied to relate the 2-D spectral parameters to the physical properties (e.g., size and shape) of biological tissues.

Purpose To assess the possibility of differentiating between completely hyalinized leiomyomas and ordinary leiomyomas by using diffusion-weighted (DW) magnetic resonance imaging (MRI) (DWI) employing very small b-factors (b = 1.51 and 55.3 seconds/mm2) in comparison with three-phase dynamic MRI. Materials and Methods The subjects were 25 patients with 52 histopathologically confirmed uterine leiomyomas. All leiomyomas were divided into two histopathologic subtypes (5 completely hyalinized leiomyomas and 47 ordinary leiomyomas). For each leiomyoma, the enhancement index (EI) at three-phase dynamic MRI and apparent diffusion coefficient (ADC) were obtained and then compared. Results The EIs at second and third dynamic phases clearly differentiated the two types of leiomyomas without overlap of values. ADCs also clearly differentiated the two types of leiomyomas without overlap of values. Moreover, there were significant positive correlations between ADCs and EIs at all dynamic phases (r = 0.41–0.50, P < 0.01). Conclusion Not only three-phase dynamic MRI but also DWI with very small b-factors could be useful for differentiating completely hyalinized leiomyomas from ordinary leiomyomas. J. Magn. Reson. Imaging 2004;20:97–104. © 2004 Wiley-Liss, Inc.

Objective. To estimate the average scatterer properties from ultrasonic backscatter in tissues for evaluating differences between neoplastic and healthy tissues. Methods. Parametric images of 8 retired breeder rats in which spontaneous mammary tumors had developed were created by superimposing color-coded pixels related to the estimated average scatterer properties on conventional gray scale B-mode images. Results. The images showed a distinct difference between the tumors and surrounding healthy tissues. Analysis of the average scatterer diameters and acoustic concentrations showed a statistically significant difference (P

The purpose of our study was to evaluate the potential value of ferumoxide-enhanced T1-weighted magnetic resonance (MR) imaging for tissue characterization of focal liver lesions when combined with T2-weighted sequences. Images were acquired within 30 minutes after the end of ferumoxide administration, when ferrite particles were not totally cleared from the intravascular compartment. Thirty-eight patients with 47 focal liver lesions underwent T1-weighted gradient-echo (TR/TE 150/4.1 msec) and T2-weighted fast spin-echo (3180-8638/90 msec) MR imaging at 1.5 T before and after intravenous administration of ferumoxides (10 micromol/kg body weight). A qualitative and quantitative analysis was performed. During the early phase after infusion of ferumoxide, blood vessels showed hypersignal intensity on T1-weighted fast low-angle shot (FLASH) images, while liver signal decreased. Hemangiomas showed both homogeneous and inhomogeneous enhancement patterns, and liver metastasis most typically showed ring enhancement. Hypervascular tumors (hepatocellular carcinomas and focal nodular hyperplasias) showed a slight degree of homogeneous enhancement. Quantitatively, the degree of enhancement and lesion-to-liver contrast on ferumoxide-enhanced images were significantly different among these tumors. Our results demonstrate that distinct enhancement patterns obtained on ferumoxide-enhanced T1-weighted MR imaging improve tissue characterization of focal liver lesions when combined with T2-weighted images.

With recent advances in the understanding of aortic diseases, both power and versatility have put magnetic resonance imaging (MRI) in the focus of diagnostic work-up in the entire spectrum of clinical aortic pathology. Technical refinements, from classic anatomic imaging to three-dimensional gadolinium-enhanced MR angiography and tissue characterization, have rendered MRI ideal for assessment of acquired disease such as aortic dissection, intramural hematoma, and aneurysm, along with postoperative follow-up evaluation, with better reliability and safety than other imaging modalities. Moreover, congenital pathology of the aorta, including aortic arch anomalies and coarctation, can be non-invasively evaluated by MRI. With spectroscopy and the advent of high-resolution intravascular coils, MRI may even provide histopathologic and potentially prognostic information unparalleled by any other method. J. Magn. Reson. Imaging 1999;10:741–750. © 1999 Wiley-Liss, Inc.

In patients with symptoms of heart failure, identifying the underlying cause of cardiomyopathy is helpful to establish the diagnosis and to guide therapy. The differential diagnosis of cardiomyopathy can be challenging based on clinical findings. We report the case of a patient who represented a clinical dilemma (cardiac sarcoidosis or ischaemic heart disease), in whom cardiovascular magnetic resonance was a clinically valuable tool to distinguish dual cardiac pathology due to its unique, non-invasive, tissue characterization capabilities.

Purpose: Deformable registration algorithms are inherently difficult to characterize in the multi-modality setting due to a significant differences in the characteristics of the different modalities (CT and MRI) as well as tissue deformations. We present a unique paradigm where this is overcome by utilizing a planning-MRI acquired within an hour of the planning-CT serving as a surrogate for quantifying MRI to CT deformation by eliminating the issues of multi-modality comparisons. Methods: For nine subjects, T2 fast-spin-echo images were acquired at two different time points, the first several weeks prior to planning (diagnostic-MRI) and the second on the same day as the planning-CT (planning-MRI). Significant effort in patient positioning and bowel/bladder preparation was undertaken to minimize distortion of the prostate in all datasets. The diagnostic-MRI was rigidly and deformably aligned to the planning-CT utilizing a commercially available deformable registration algorithm synthesized from local registrations. Additionally, the quality of rigid alignment was ranked by an imaging physicist. The distances between corresponding anatomical landmarks on rigid and deformed registrations (diagnostic-MR to planning-CT) were evaluated. Results: It was discovered that in cases where the rigid registration was of acceptable quality the deformable registration didn’t improve the alignment, this was true of all metrics employed. If the analysis is separated into cases where the rigid alignment was ranked as unacceptable the deformable registration significantly improved the alignment, 4.62mm residual error in landmarks as compared to 5.72mm residual error in rigid alignments with a p-value of 0.0008. Conclusion: This paradigm provides an ideal testing ground for MR to CT deformable registration algorithms by allowing for inter-modality comparisons of multi-modality registrations. Consistent positioning, bowel and bladder preparation may Result in higher quality rigid registrations than typically achieved which limits the impact of deformable registrations. In this study cases where significant differences exist, deformable registrations provide significant value. This work was funded by an NIH grant# 1R01CA189295-01. PI: Alan Pollack, MD PhD. “MRI IMAGING AND GENETIC SIGNATURES TO MANAGE PROSTATE CANCER OVERDIAGNOSIS”

Normal values in adults for ultrasonic tissue characterization by integrated backscatter have been reported previously and subsequently applied to patients with specific diseases. Factors influencing integrated backscatter values in a pediatric population are not clearly defined. To obtain normal values for myocardial ultrasonic integrated backscatter in a pediatric population, we studied 72 children with normal cardiac anatomy using an ultrasonic integrated backscatter imaging system. The parameters measured were at peak, nadir, and end-diastole in eight different regions with two different settings: fixed and variable. We subsequently calculated cyclic variation, the ratios of cyclic variation to end-diastole and to peak. Age ranged from 1 day to 17.4 years (median 4.4 years). More than 90% of data curves from the two regions in the left ventricular posterior wall in long-axis view had normal patterns, whereas more than 50% of curves for the other regions had abnormal patterns. Comparing the two posterior wall positions, there were no differences in cyclic variation between the two regions, with little effect of setting. Less effect of regions and settings was noted for the ratios of cyclic variation to end-diastole or peak. There was no relation between backscatter variables and age, gender, or height, and some variables correlated weakly with body surface area. The assessment of integrated backscatter in children is optimal with interrogation of the left ventricular posterior wall imaged in the long-axis view. More stable estimates are obtained when the cyclic variation is related to the peak or end-diastolic value.