Time-signal Curve Research Articles

Research on measuring method of shot exit time for muzzle vibration analysis

The measurement of shot exit time is very important to measuring data analysis of muzzle vibration. Optoelectronic method, which is based on the optical-electrical conversion theory and timed with the muzzle flame, is a general method of measuring the shot exit time for the major caliber gun. However, it has not been identified that the shot exit time corresponds to which characteristic point in the voltage pulse time signal curve obtained by the optoelectronic method. In this paper, by combining the high speed digital photography and the optoelectronic method, both the triggering time signal of the high speed digital photography and the voltage signal output by the optoelectronic sensor were obtained simultaneously. Then by comparing the voltage time curve of the optoelectronic sensor with the photographs obtained by the digital photography, the relationship between the characteristic points in the signal curve and the shot exit time was identified. It has been shown that, the voltage pulse beginning time is the same with the muzzle flame beginning, which is later than the time when the projectile band leaves from muzzle.

Study of kinetics of 19F-MRI using a fluorinated imaging agent (19FIT) on a 3T clinical MRI system.

To use 19F imaging tracer (19FIT-27) to evaluate kinetics in major organs. Kinetics studies using proton MRI are difficult because of low concentration of 19FIT-27 protons relative to background water protons. Because there is no background source of 19F NMR in a biological body, 19F may be an ideal nucleus to directly trace 19FIT-27. However, there are several challenges for reliable 19F MR imaging and spectroscopy, particularly with clinical whole-body MRI systems, which include low concentrations and long 19F T1. We performed a dynamic 19F MRI study on mice at a 3T whole-body MRI system using a homemade transmit/receive (Tx/Rx) switch and a Tx/Rx volume RF coil. We used a newly developed fluorine imaging agent, which has 27 identical fluorine atoms with identical chemical shift, a relatively short T1, and high hydrophilicity. Basic kinetics parameters were estimated from the 19F signal-time curve. Resultant fluorine images show fairly high spatial (3 × 3 × 3mm3) and temporal resolutions. Biodistribution and kinetics of 19FIT-27 are obtained via 19F images for major uptake organs. Whole-body dynamic 19F MRI of newly developed 19FIT-27 in mice was obtained with fairly high spatial and temporal resolutions on a 3T clinical MRI system. The present study demonstrates the feasibility of 19F MRI using our newly developed compound to investigate major organ kinetics.

Precontrast T1 signal measurements of normal pituitary and microadenoma: A retrospective analysis through DCE MRI signal time curves.

Background:The dynamic contrast enhanced magnetic resonance imaging (DCE MRI) has currently become the most utilized technique for the detection of pituitary microadenoma. However, owing to differential enhancement of normal pituitary, high rate of false positivity remains a concern in its interpretation.Purpose:Our aim was to assess the utility of precontrast T1 signal intensity ratio (SIR) of the lesions suspected on DCE MRI, in prediction of presence of microadenoma.Materials and Methods:We retrospectively reviewed MRI of 23 patients referred for DCE MRI of pituitary (group 1, 15 patients with diagnosis of pituitary microadenoma; and group 2, patients not clinically labeled as microadenoma). STC were plotted and T1-SIR at t = 0 s was obtained at the suspicious zone of differential enhancement (SIR T) and normal pituitary (SIR P). SIR difference (SIR P − SIR T) and relative SIR difference (SIR P − SIR T/SIR P) were calculated for each patient and was compared between the two groups.Results:Mean T1 SIR is lower in patients with microadenoma than those without (P = 0.065). SIR difference and relative SIR difference was higher in patients with microadenoma (P = 0.003 and 0.005, respectively). Receiver-operated characteristic curve analysis demonstrated that a cut-off of 26 and 0.107 for SIR difference and relative SIR difference, respectively, could diagnose microadenoma with 100% specificity and reasonable sensitivities.Conclusion:The baseline precontrast T1 SIR evaluation of the lesion suspected to be microadenoma on DCE MRI, derived through STC curve, can increase diagnostic confidence in diagnosis of microadenoma.

DCE-MRI and parametric imaging in monitoring response to neoadjuvant chemotherapy in breast carcinoma: a preliminary report.

PurposeNeoadjuvant chemotherapy is recommended in patients with locally advanced breast cancer. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) enables evaluation of the tumour neovasculature that occurs prior to any volume change, which helps identify early treatment failures and allows prompt implementation of second-line therapy.Material and methodsWe conducted a prospective study in 14 patients with histopathologically proven breast cancer. DCE-MRI data were acquired using multisection, T1-weighted, 3D vibe sequences with fat suppression before, during, and after IV bolus injection (0.1 mmol/kg body weight, Gadoversetamide, Optimark). Post-processing of dynamic contrast perfusion data was done with the vendor’s Tissue 4D software to generate various dynamic contrast parameters, i.e. Ktrans, Kep, Ve, initial area under the time signal curve (IAUC), apparent diffusion coefficient (ADC), and enhancement curve. Patients underwent MRI examinations at baseline, and then after two cycles, and finally at completion of chemotherapy.ResultsBased on Sataloff criteria for pathological responses, four patients out of 14 were responders, and 10 were non-responders. At the 2nd MRI examination, IAUC was significantly smaller in responders than in non-responders (p = 0.023). When the results of the first and second MRI examinations were compared, Kep decreased from baseline to the second MRI (p = 0.03) in non-responders and in responders (p = 0.04). This change was statistically significant in both groups. The ADC values increased significantly in responders from baseline to the third MRI (p = 0.012).ConclusionsIn our study, IAUC and ADC were the only parameters that reliably differentiated responders from non-responders after two and three cycles of chemotherapy.

Direct estimation of 17 O MR images (DIESIS) for quantification of oxygen metabolism in the human brain with partial volume correction.

To provide a data post-processing method that corrects for partial volume effects (PVE) and fast decay in dynamic 17 O MRI for the mapping of cerebral metabolic rates of oxygen consumption (CMRO2 ). CMRO2 is altered in neurodegenerative diseases and tumors and can be measured after 17 O gas inhalation using dynamic 17 O MRI. CMRO2 quantification is difficult because of PVE. To correct for PVE, a direct estimation of the MR images (DIESIS) method is proposed and used in 4 dynamic 17 O MRI data sets of a healthy volunteer acquired on a 3T MRI system. With DIESIS, 17 O MR signal time curves in selected regions were directly estimated based on parcellation of a coregistered 1 H MPRAGE image. Profile likelihood analysis of the DIESIS method showed identifiability of CMRO2 . In white matter (WM), DIESES reduced CMRO2 from 0.97 ± 0.25 µmol/gtissue /min with Kaiser-Bessel gridding reconstruction to 0.85 ± 0.21 µmol/gtissue /min, whereas in gray matter (GM) it increases from 1.3 ± 0.31 µmol/gtissue /min to 1.86 ± 0.36 µmol/gtissue /min; both values are closer to the literature values from the 15 O-PET studies. DIESIS provided an increased separation of CMRO2 values in GM and WM brain regions and corrected for partial volume effects in 17 O-MRI inhalation experiments. DIESIS could also be applied to more heterogeneous tissues such as glioblastomas if subregions of the tumor can be represented as additional parcels.

Abstract WMP22: Temporal Similarity Perfusion Mapping, An Effective CTP Analysis Method Without Transit Delay Sensitivity

Introduction: Studies investigating the value of CT perfusion (CTP) imaging in treatment decision or outcome prediction of acute stroke patients have found conflicting results. This may be attributed to variable accuracy and reliability across the different deconvolution algorithms. The aim of this study was to introduce a new, standardized and model-free method, based on similarities in signal time-curves (Pearson’s correlation coefficient) and to increase robustness of CTP analysis and perfusion deficit detection. Methods: Acute stroke patients from the Dutch Acute Stroke Study were included. CTP data acquired at admission was analyzed using a deconvolution method (Philips Brain Perfusion software) and with TSP. Acute CTP and follow-up non-contrast images after 3 days were interpreted by experienced and inexperienced raters for presence of perfusion deficits, intra-rater and inter-rater agreement. Results: 65 patients (68±13 years) were included. Example images are shown in the Figure. A perfusion deficit was detected in 56 patients on the MTT deconvolution maps; TSP detected 54 of these perfusion deficits. The agreement of MTT, TTP and TSP with the presence of ischemia on follow-up was comparable, but noticeably lower for CBV. CBV had the best relationship with final infarct volume (R 2 =0.77, p<0.001), closely followed by TSP (R 2 =0.63, p<0.001). Inter-rater agreement of experienced readers was comparable across maps. Intra-rater agreement of an inexperienced reader was higher for TSP than for CBV/MTT (kappa’s of 0.79-0.84 versus 0.63-0.7). Conclusion: TSP offers a very fast, automated, non-proprietary, analysis of CTP data. TSP maps are highly comparable to deconvolution maps, but easier to interpret for inexperienced readers. The relationship of TSP perfusion deficit volume with final infarct volume is comparable to CBV. This suggests that TSP might be a valuable alternative to deconvolution-derived maps, which are known to be prone to tracer delays.

2 Milisievert Low Dose Dedicated Breast CT with Iterative Model Reconstruction Technique in Evaluation of Breast Mass: Feasibility Study in Comparison with MRI

Objective To investigate the feasibility of low dose dedicated computed tomography (CT) with IMR technique compared with magnetic resonance imaging (MRI) in preoperative evaluation of breast cancer. Methods Dedicated CT and breast MRI were performed in 21 patients with diagnosed breast mass for preoperative evaluation. A dedicated protocol combined with chest diagnostic CT and dynamic scans of breast was developed with the use of IMR technique as well as optimization of scan parameters to ensure acceptable radiation dose. Image quality evaluations of CT images were performed using a five-point scale. The number, site and size (maximum diameter) of breast lesion were recorded respectively in CT and MRI images. The enhancement patterns of breast lesion were classified to 3 types (washout, plateau, and persistence) according to time intensity curve derived from CT and time signal curve derived from MRI, respectively. Pearson’s correlation, Bland-Altman analysis, and Cohen’s kappa test were used for statistical assessment. Results The mean effective radiation dose of dedicated breast CT, with the image quality diagnostic acceptable for evaluation of breast lesion and pulmonary structures, was (2.15±0.39) mSv, which was no more than a routine chest diagnostic CT. Results of breast lesion number and lesion site obtained by CT and MRI was consistent, with a total of 24 lesions detected in 21 patients. The mean lesion size was (26.5±12.1) mm in CT and (26.1±12.9) mm in MR, respectively. CT showed an excellent correlation with MRI for lesion size (r=0.99, n=24, p<0.0001). Limits of agreement determined by Bland-Altman analysis for lesion extent was (-3.0mm, 3.8mm). Good agreement was observed between CT and MRI for lesion enhancement patterns (kappa value = 0.936, p=0.000). Conclusion Dedicated breast CT imaging with acceptable radiation dose enabled diagnostic image quality and showed good agreement with breast MR imaging in preoperative evaluation of breast cancer.

High-resolution hyperpolarized metabolic imaging of the rat heart using k-t PCA and k-t SPARSE.

The purpose of this work was to increase the resolution of hyperpolarized metabolic imaging of the rat heart with accelerated imaging using k–t principal component analysis (k–t PCA) and k–t compressed sensing (k–t SPARSE). Fully sampled in vivo datasets were acquired from six healthy rats after the injection of hyperpolarized [1‐13C]pyruvate. Data were retrospectively undersampled and reconstructed with either k–t PCA or k–t SPARSE. Errors of signal–time curves of pyruvate, lactate and bicarbonate were determined to compare the two reconstruction algorithms for different undersampling factors R. Prospectively undersampled imaging at 1 × 1 × 3.5‐mm3 resolution was performed with both methods in the same animals and compared with the fully sampled acquisition. k–t SPARSE was found to perform better at R &lt; 3, but was outperformed by k–t PCA at R ≥ 4. Prospectively undersampled data were successfully reconstructed with both k–t PCA and k–t SPARSE in all subjects. No significant difference between the undersampled and fully sampled data was found in terms of signal‐to‐noise ratio (SNR) performance and metabolic quantification. Accelerated imaging with both k–t PCA and k–t SPARSE allows an increase in resolution, thereby reducing the intravoxel dephasing of hyperpolarized metabolic imaging of the rat heart.

Effects of sampling frequency on the accuracy of phenomenological and pharmacokinetic parameters derived from dynamic contrast enhanced MRI data

The sampling frequencies (fs) at which dynamic contrast enhanced (DCE) MRI data are acquired is known to affects the accuracy of derived parameters. Phenomenological parameters empirically characterise the shape and structure of the signal-time curves, whereas pharmacokinetic approaches estimate physiologically relevant parameters from the concentration-time curves, such as the volume-transfer constant (Ktrans) and the extravascular-extracellular fractional volume (ve). Both of these approaches have shown promise in the detection of prostate cancer, however to date a method has been lacking to quantitatively compare MR-measured to known ‘ground truth’ parameter values. In the present work, a newly developed anthropomorphic DCE-MRI prostate phantom was utilised to this end. Precisely known ‘healthy’ and ‘tumorous’ curves were measured using a 3T scanner (Philips, Netherlands) and 32-channel detector coil (3D-SPGR, TR/TE = 4.3/1.4 ms, α = 10°, FOV = 224 × 224 × 80 mm3, voxels = 1 × 1 × 4 mm3) at fs = 0.5, 0.26, 0.19, 0.12, 0.061, and 0.041 Hz. Phenomenological analysis revealed that wash-in was measured with the lowest errors ( 15%) at fs ⩾ 0.12 Hz, whereas wash-out gave comparatively higher errors (up to 27%) across this same range of fs. Lowest errors in time-to-peak ( 11%) were measured using fs = 2 s and 8.1 s. Pharmacokinetic analysis using the Tofts model gave errors in Ktrans and ve values 14% and 10%, for acquisitions with fs ⩾ 0.12 Hz and fs ⩾ 0.061 respectively, with errors increasing dramatically (up to 172%) with fs 0.061 Hz. Quantitative phantom-based approaches, such as the one used herein, offers the prospect of a standardisation in the way DCE-MRI is performed in the prostate, and possibly a wider acceptance of the technique for routine clinical use. Acknowledgement This work is funded by Irish Cancer Society Research Scholarship CRS13KNI (supported by Movember).

Fast dynamic ventilation MRI of hyperpolarized 129Xe using spiral imaging

PurposeTo develop and optimize a rapid dynamic hyperpolarized 129Xe ventilation (DXeV) MRI protocol and investigate the feasibility of capturing pulmonary signal‐time curves in human lungs.Theory and MethodsSpiral k‐space trajectories were designed with the number of interleaves N int = 1, 2, 4, and 8 corresponding to voxel sizes of 8 mm, 5 mm, 4 mm, and 2.5 mm, respectively, for field of view = 15 cm. DXeV images were acquired from a gas‐flow phantom to investigate the ability of N int = 1, 2, 4, and 8 to capture signal‐time curves. A finite element model was constructed to investigate gas‐flow dynamics corroborating the experimental signal‐time curves. DXeV images were also carried out in six subjects (three healthy and three chronic obstructive pulmonary disease subjects).ResultsDXeV images and numerical modelling of signal‐time curves permitted the quantification of temporal and spatial resolutions for different numbers of spiral interleaves. The two‐interleaved spiral (N int = 2) was found to be the most time‐efficient to obtain DXeV images and signal‐time curves of whole lungs with a temporal resolution of 624 ms for 13 slices. Signal‐time curves were well matched in three healthy volunteers. The Spearman's correlations of chronic obstructive pulmonary disease subjects were statistically different from three healthy subjects (P < 0.05).ConclusionThe N int = 2 spiral demonstrates the successful acquisition of DXeV images and signal‐time curves in healthy subjects and chronic obstructive pulmonary disease patients. Magn Reson Med 79:2597–2606, 2018. © 2017 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.

Evaluation of diffusion kurtosis imaging in the differential diagnosis of breast lesions

Objective To evaluate the role of the diffusion kurtosis imaging(DKI)in the differential diagnosis of breast lesions. Methods Seventy five breast lesions (32 benign and 43 malignant) in 72 patients confirmed by histopathology were studied. All patients underwent 3.0 T MR examinations, including T1WI, T2WI, T2WI-spectral adiabatic inversion recovery, 4b diffusion-weighted imaging, and dynamic contrast-enhanced MR imaging(DCE-MRI). Data were post-processed by mono-exponential and diffusion kurtosis models for quantitation of ADC, apparent diffusion for non-Gaussian distribution(D), and apparent kurtosis coefficient(K). All breast lesions were described with the classification by breast imaging report and data system(BI-RADS). Lesions with BI-RADS class 4B or above were rated as malignancy. Independent sample t test was used to compare the ADC, D, and K value differences between benign and malignant lesions. ROC analysis was performed to assess the role of ADC, D, K value, and BI-RADS in the differential diagnosis of breast lesions. The morphological characteristics, time-signal curve(TIC)type, and other differences between benign and malignant lesions were analyzed with Chi-square test. Results ADC and D values were significantly lower in malignant than in benign lesions(P<0.01). Conversely, K value was significantly higher in malignant lesions than in benign ones(P<0.01). The shape of the benign and malignant breast lesions, edge, enhancement mode, TIC, and BI-RADS classification difference had statistical significance(P<0.05, respectively). The areas under the ROC curve of ADC, D, K, DCE-MRI, and DCE-MRI combined with K value were 0.857, 0.884, 0.949, 0.806, and 0.958, respectively. DCE-MRI combined with K value had the highest diagnosis efficiency. At a cutoff value of K= 0.856, the sensitivity and specificity were 83.7% and 93.8%, respectively. Conclusions DKI model showed higher diagnostic efficiency than that of traditional DWI model. DCE-MRI combined with K value can increase the diagnostic efficiency in breast lesions. Key words: Breast neoplasms; Magnetic resonance imaging; Comparative study

Role of High-Resolution Dynamic Contrast-Enhanced MRI with Golden-Angle Radial Sparse Parallel Reconstruction to Identify the Normal Pituitary Gland in Patients with Macroadenomas.

Preoperative localization of the pituitary gland with imaging in patients with macroadenomas has been inadequately explored. The pituitary gland enhancing more avidly than a macroadenoma has been described in the literature. Taking advantage of this differential enhancement pattern, our aim was to evaluate the role of high-resolution dynamic MR imaging with golden-angle radial sparse parallel reconstruction in localizing the pituitary gland in patients undergoing trans-sphenoidal resection of a macroadenoma. A retrospective study was performed in 17 patients who underwent trans-sphenoidal surgery for pituitary macroadenoma. Radial volumetric interpolated brain examination sequences with golden-angle radial sparse parallel technique were obtained. Using an ROI-based method to obtain signal-time curves and permeability measures, 3 separate readers identified the normal pituitary gland distinct from the macroadenoma. The readers' localizations were then compared with the intraoperative location of the gland. Statistical analyses were performed to assess the interobserver agreement and correlation with operative findings. The normal pituitary gland was found to have steeper enhancement-time curves as well as higher peak enhancement values compared with the macroadenoma (P < .001). Interobserver agreement was almost perfect in all 3 planes (κ = 0.89). In the 14 cases in which the gland was clearly identified intraoperatively, the correlation between the readers' localization and the true location derived from surgery was also nearly perfect (κ = 0.95). This study confirms our ability to consistently and accurately identify the normal pituitary gland in patients with macroadenomas with the golden-angle radial sparse parallel technique with quantitative permeability measurements and enhancement-time curves.

CT and MRI features of aggressive angiomyxoma

Objective To analyze the imaging features of aggressive angiomyxoma (AAM) on CT and MRI. Methods Seven patients with pathologically confirmed AAM had CT and/or MRI examination within 1 week prior to surgery. Six patients had multi-slice helical CT scanning while four of the six patients had multi-phase contrast enhancement. Five patients had MR scanning with contrast administration covering the chest, mid-abdomen or pelvis. The imaging and pathological findings were retrospectively reviewed. Results (1) CT presentations: pre-contrast CT images revealed isodensity (1 case), heterogeneous density (5 cases), cystic degeneration (2 cases) and mural nodule (2 cases). Contrast CT images showed homogeneous and gradual enhancement (1 case), heterogeneous and progressive enhancement (3 cases), whorl sign (3 cases) and opacification of small vessels (3 cases). (2) On MR images, five cases showed high or slightly high signal on T2WI; three cases presented with whorl sign; two cases had cystic degenerations. Iso-signal or low-signal was shown at T1WI in all five cases. DWI demonstrated high or mildly high signal in five cases. At contrast images, a whole-lesion homogeneous and gradual enhancement was present in one case. Four cases revealed progressive and expanding enhancement, where whorl sign and gradual enhancement were present in three cases. A progressive ascending pattern of time-signal curve was delineated in three cases. (3) Microscopically, the tumor comprises of poorly-defined satellite or spindle cells with sparse cytoplasm and varied sizes of vessels, which distribute among stroma with rich collagen fibre and myxoid. Those components were heterogeneous to congregate compact cell cluster. The stroma in four cases was abundant in collagen fibre that was aligned with myxoid stroma and tumor cell alternately. Conclusion AAM exhibits characteristic CT and MRI features. The imaging features correlated well with pathological findings. Key words: Myxoma; Tomography,X-ray computed; Magnetic resonance imaging; Pathology

Intravoxel incoherent motion diffusion-weighted imaging as an adjunct to dynamic contrast-enhanced MRI to improve accuracy of the differential diagnosis of benign and malignant breast lesions

PurposeTo investigate the value of use of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) as an adjunct to dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to distinguish benign from malignant breast lesions. Materials and methodsRetrospective analysis of data pertaining to 117 patients with breast lesions who underwent DCE-MRI and IVIM-DWI examination with 3.0T MRI was conducted. A total of 128 lesions were pathologically confirmed (47 benign and 81 malignant). Between-group differences in DCE-MRI parameters (Morphology, enhancement pattern, maximum slope of increase (MSI) and time–signal curve (TIC) type) and IVIM-DWI parameters (f value, D value and D* value) were assessed. Multivariate logistic regression was performed to identify variables that distinguished benign from malignant breast lesions. The diagnostic performance of DCE-MRI and DCE-MRI plus IVIM-DWI, to distinguish benign from malignant breast lesions, was evaluated using pathology results as the gold standard. ResultsLesion morphology, MSI, and TIC type (P<0.05), but not the enhancement pattern (P>0.05), were significantly different between the benign and malignant groups. The f (8.53±2.14) and D* (7.64±2.07) values in the malignant group were significantly higher than those in the benign group (7.68±1.97 and 6.83±2.13, respectively), while the D value (0.99±0.22) was significantly lower than that (1.34±0.17) in the benign group (P<0.05 for all). On logistic regression analysis, the sensitivity, specificity and accuracy of DCE-MRI were 90.1%, 70.2% and 82.8% respectively; the corresponding figures for the combination of IVIM-DWI and DCE-MRI were 88.8%, 85.1%, and 87.5%respectively. ConclusionIVIM-DWI method as an adjunct to DCE-MRI can improve the specificity and accuracy in differential diagnosis of benign and malignant lesions of breast.

High-resolution dynamic CE-MRA of the thorax enabled by iterative TWIST reconstruction.

To evaluate the clinical benefit of using a new iterative reconstruction technique fully integrated on a standard clinical scanner and reconstruction system using a TWIST acquisition for high-resolution dynamic three-dimensional contrast-enhanced MR angiography (CE-MRA). Low-dose, high-resolution TWIST datasets of 11 patients were reconstructed using both standard GRAPPA-based reconstruction for reference and iterative reconstruction, which reduces the temporal footprint of reconstructed images. Image quality of both techniques was assessed by two experienced readers, as well as quantitatively evaluated using a time-signal curve analysis. Image quality scores consistently and significantly improved by using iterative reconstruction compared with the standard approach. Most notably, the delineation of small to mid-size vasculature improved from a mean Likert score between "nondiagnostic" and "poor" for standard to between "good" and "excellent" for iterative reconstruction. The full width at half maximum of the contrast agent bolus computed from the time-signal curve was also reduced by iterative reconstruction, allowing for more precise bolus timing. Iterative reconstruction can substantially improve high-resolution dynamic CE-MRA image quality, most notably in small to mid-size vasculature. Dynamic CE-MRA with iterative reconstruction could become an alternative to conventional static 3D CE-MRA, thus simplifying the clinical workflow. Magn Reson Med 77:833-840, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Associations between muscle perfusion and symptoms in knee osteoarthritis: a cross sectional study

To investigate the association between muscle perfusion in the peri-articular knee muscles assessed by dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) and symptoms in patients with knee osteoarthritis (KOA). In a cross-sectional setting, muscle perfusion was quantified by DCE-MRI in KOA. Regions of interest (ROI) were drawn around the peri-articular muscles, summed and averaged into one single "Total Muscle Volume" volume of interest (VOI). Symptoms were assessed via the Knee injury and Osteoarthritis Outcome Score (KOOS) (0: worst; 100: best). DCE-MRI and clinical data were analyzed in 94 patients. The typical participant was a woman with a mean age of 65 years, and a body mass index (BMI) of 32 kg/m(2). Reduced multiple regression models analyzing the association between KOOS and DCE-MRI perfusion variables of Total Muscle Volume showed a statistically significant association between Nvoxel% and KOOS pain (0.41 (SE 0.14); P = 0.0048). Nvoxel% was defined as the proportion of highly perfused voxels; i.e., the voxels that show an early and rapid increase on the signal intensity vs time curves, reach a plateau state (plateau pattern) and then showing a relatively rapid decline (washout pattern) relative to the total number of voxels within the muscle VOI. More widespread perfusion in the peri-articular knee muscles was associated with less pain in patients with KOA. These results give rise to investigations of the effects of exercise on muscle perfusion and its possible mediating role in the causal pathway between exercise and pain improvements in the conservative management of KOA.

High-Resolution DCE-MRI of the Pituitary Gland Using Radial k-Space Acquisition with Compressed Sensing Reconstruction.

The pituitary gland is located outside of the blood-brain barrier. Dynamic T1 weighted contrast enhanced sequence is considered to be the gold standard to evaluate this region. However, it does not allow assessment of intrinsic permeability properties of the gland. Our aim was to demonstrate the utility of radial volumetric interpolated brain examination with the golden-angle radial sparse parallel technique to evaluate permeability characteristics of the individual components (anterior and posterior gland and the median eminence) of the pituitary gland and areas of differential enhancement and to optimize the study acquisition time. A retrospective study was performed in 52 patients (group 1, 25 patients with normal pituitary glands; and group 2, 27 patients with a known diagnosis of microadenoma). Radial volumetric interpolated brain examination sequences with golden-angle radial sparse parallel technique were evaluated with an ROI-based method to obtain signal-time curves and permeability measures of individual normal structures within the pituitary gland and areas of differential enhancement. Statistical analyses were performed to assess differences in the permeability parameters of these individual regions and optimize the study acquisition time. Signal-time curves from the posterior pituitary gland and median eminence demonstrated a faster wash-in and time of maximum enhancement with a lower peak of enhancement compared with the anterior pituitary gland (P < .005). Time-optimization analysis demonstrated that 120 seconds is ideal for dynamic pituitary gland evaluation. In the absence of a clinical history, differences in the signal-time curves allow easy distinction between a simple cyst and a microadenoma. This retrospective study confirms the ability of the golden-angle radial sparse parallel technique to evaluate the permeability characteristics of the pituitary gland and establishes 120 seconds as the ideal acquisition time for dynamic pituitary gland imaging.

Relationship between intravoxel incoherent motion diffusion-weighted MRI and dynamic contrast-enhanced MRI in tissue perfusion of cervical cancers.

To investigate the relationship between intravoxel incoherent motion (IVIM) diffusion-weighted magnetic resonance imaging (MRI) and dynamic contrast-enhanced MRI (DCE-MRI) in cervical cancer perfusion. Prospective newly diagnosed cervical cancer patients underwent diffusion-weighted MRI (13 b-values: 1-1000 s/mm(2) ) and DCE-MRI. The IVIM perfusion parameters, perfusion fraction (f), pseudodiffusion coefficient (D*), and flow-related parameter (fD*), were derived from a biexponential decay model. DCE-MRI was analyzed with a pharmacokinetic model and signal-time curve to derive the amplitude factor (A), estimated volume transfer constant between blood plasma, and the extravascular extracellular space (est K(trans) ), maximum relative enhancement (MaxRE), and area under the signal-time curve (AUC). Spearman's rank correlation coefficient (r) evaluated the correlative relationships. The f = 13.51% ± 1.76%, D* = 71.72 ± 7.55 × 10(-3) mm(2) /s, fD* = 9.64 ± 1.28 × 10(-3) mm(2) /s, A = 1.41 ± 0.43, est K(trans) = 0.19 ± 0.06 s(-1) , MaxRE of 120.02 ± 21.07%, and AUC 212,393 ± 54,423 was found in 25 cervical cancer patients. Statistically significant positive correlations were found between fD* and est K(trans) (r = 0.42, P = 0.038), fD* and A (r = 0.50, P = 0.011), fD* and MaxRE (r = 0.52, P = 0.008), f and AUC (r = 0.58, P = 0.003). The IVIM perfusion parameters showed moderate to good correlations with quantitative and semiquantitative perfusion parameters derived from DCE-MRI in cervical cancer.

Bone structure and perfusion quantification of bone marrow edema pattern in the wrist of patients with rheumatoid arthritis: a multimodality study.

To quantify bone structure and perfusion parameters in regions of bone marrow edema pattern (BMEP), non-edematous bone marrow (NBM), and pannus tissue areas in the wrists of patients with rheumatoid arthritis (RA) using 3-Tesla (3T) magnetic resonance imaging (MRI), and high resolution peripheral quantitative computed tomography (HR-pQCT). Sixteen subjects fulfilling American College of Rheumatology classification were imaged using a HR-pQCT system and a 3T MRI scanner with an 8-channel wrist coil. Coronal T2-weighted and dynamic contrast-enhanced (DCE-MRI) images were acquired. BMEP and pannus tissue areas were segmented semiautomatically in T2-weighted images. NBM areas were placed at a similar distance from the joint space as BMEP regions. MR and HR-pQCT images were registered, and bone variables were calculated within the BMEP and NBM regions. Perfusion parameters in BMEP, pannus tissue, and NBM regions were calculated based on the signal-time curve obtained from DCE-MRI. Eighteen BMEP areas were segmented, 15 of them presented proximal to pannus-filled erosions. Significant increases in bone density and trabecular thickness and number were observed in all BMEP regions compared to NMB (p < 0.05). Significantly elevated perfusion measures were observed in both BMEP and pannus tissue regions compared to NBM (p < 0.05). BMEP regions showed significantly increased bone density and structures as well as perfusion measures, suggesting bone remodeling and active inflammation. Combining MRI and HR-pQCT provides a powerful multimodality approach for understanding BMEP and erosions, and for potentially identifying novel imaging markers for disease progression in RA.

Direct 17O MRI with partial volume correction: first experiences in a glioblastoma patient

In tumor cells the energy production is shifted from aerobic to anaerobic metabolization of glucose, which makes the cerebral metabolic rate of oxygen consumption (CMRO2) a diagnostic parameter for tissue viability. Direct oxygen-17 ((17)O) MRI during inhalation of (17)O gas allows for a non-invasive determination of the CMRO2. However, the low spatial resolution and the fast transverse relaxation of (17)O lead to partial volume effects that severely bias the quantification of signal intensities. The aim of this work was to determine the CMRO2 in a tumor patient by (17)O MRI in combination with a partial volume correction (PVC) scheme. Direct (17)O MRI was performed in a glioblastoma patient (F, 51 years) prior to surgery at 7 T. The 'geometric transfer matrix' algorithm for volume of interest based PVC was adapted to (17)O MRI to recover the true signal intensities. We determined the CMRO2 values of gray matter (GM), white matter (WM), cerebrospinal fluid (CSF) and the tumor areas of the contrast enhancing rim (CE), the necrotic center (NE), and the perifocal edema (PE) using a three-phase metabolic model. Large differences in the signal increase during (17)O2 inhalation were obtained ranging from less than 2% in the tumor center up to more than 20% in GM areas. After PVC of the signal time curves, we determined CMRO2 values of 0.67 ± 0.08 μmol/g/min (WM), 3.57 ± 0.67 μmol/g/min (GM), 0.35 ± 0.09 μmol/g/min (CE), and 0.42 ± 0.05 μmol/g/min (PE). In CSF and NE no oxygen uptake (i.e. CMRO2 = 0) was determined from the corrected signals, well in accordance with the underlying physiology in these regions. The results show that PVC has a strong effect on the resulting CMRO2 values obtained by (17)O MRI. We found substantial differences-especially in GM tissue-between corrected and non-corrected CMRO2 values. Additionally, we demonstrated the feasibility of CMRO2 assessment in a glioblastoma patient by (17)O MRI.