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Journal Cover Magnetic Resonance Materials in Physics, Biology and Medicine
  [SJR: 0.787]   [H-I: 46]   [2 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0968-5243 - ISSN (Online) 1352-8661
   Published by Springer-Verlag Homepage  [2335 journals]
  • Non-gadolinium dynamic angiography of the neurovasculature using arterial
           spin labeling MRI: preliminary experience in children
    • Authors: Houchun H. Hu; Amber L. Pokorney; Niccolo Stefani; Jonathan M. Chia; Jeffrey H. Miller
      Pages: 107 - 112
      Abstract: Objective We demonstrate the potential clinical utility of a 4D non-gadolinium dynamic angiography technique based on arterial spin-labeling called contrast inherent inflow enhanced multi-phase angiography (CINEMA) in pediatric patients. Materials and Methods CINEMA was qualitatively compared to conventional time-of-flight (TOF) angiography in a cohort of 31 pediatric patients at 3 Tesla. Results CINEMA data were successfully acquired and reconstructed in all patients with no image artifacts. There were no cases where CINEMA was rated inferior to TOF in depicting intracranial vessel conspicuity. In 19 cases, CINEMA was rated equivalent to TOF and in the 12 remaining cases CINEMA was rated superior to TOF. Conclusion There is a steadily rising concern in adults and children over the potential effects of intracranial deposition of gadolinium. CINEMA is therefore a viable alternative in dynamic neurovascular imaging.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0589-5
      Issue No: Vol. 30, No. 2 (2017)
       
  • A comparison of fitting algorithms for diffusion-weighted MRI data
           analysis using an intravoxel incoherent motion model
    • Authors: Roberta Fusco; Mario Sansone; Antonella Petrillo
      Pages: 113 - 120
      Abstract: Object The objective of this study is to propose a modified VARiable PROjection (VARPRO) algorithm specifically tailored for fitting the intravoxel incoherent motion (IVIM) model to diffusion-weighted magnetic resonance imaging (DW-MRI) data from locally advanced rectal cancer (LARC). Materials and methods The proposed algorithm is compared with classical non-linear least squares (NLLS) analysis using the Levenberg-Marquardt (LM) algorithm and with two recently proposed algorithms for ‘segmented’ analysis. These latter two comprise two consecutive steps: first, a subset of parameters is estimated using a portion of data; second, the remaining parameters are estimated using the whole data and the previous estimates. The comparison between the algorithms was based on the \(R^2\) goodness-of-fit measure: performance analysis was carried out on real data obtained by DW-MRI on 40 LARC patients. Results The performance of the proposed algorithm was higher than that of LM in 64 % of cases; ‘segmented’ methods were poorer than our algorithm in 100 % of cases. Conclusion The proposed modified VARPRO algorithm can lead to better fit of the IVIM model to LARC DW-MRI data compared to other techniques.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0591-y
      Issue No: Vol. 30, No. 2 (2017)
       
  • Reproducibility of locus coeruleus and substantia nigra imaging with
           neuromelanin sensitive MRI
    • Authors: Jason Langley; Daniel E. Huddleston; Christine J. Liu; Xiaoping Hu
      Pages: 121 - 125
      Abstract: Objectives The purpose of this study was to assess the reproducibility of substantia nigra pars compacta (SNpc) and locus coeruleus (LC) delineation and measurement with neuromelanin-sensitive MRI. Materials and methods Eleven subjects underwent two neuromelanin-sensitive MRI scans. SNpc and LC volumes were extracted for each scan. Reproducibility of volume and magnetization transfer contrast measurements in SNpc and LC was assessed using intraclass correlation coefficients (ICC) and dice similarity coefficients (DSC). Results SNpc and LC volume measurements showed excellent reproducibility (SNpc-ICC: 0.94, p < 0.001; LC-ICC: 0.96, p < 0.001). SNpc and LC were accurately delineated between scans (SNpc-DSC: 0.80 ± 0.03; LC-DSC: 0.63 ± 0.07). Conclusion Neuromelanin-sensitive MRI can consistently delineate SNpc and LC.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0590-z
      Issue No: Vol. 30, No. 2 (2017)
       
  • Dynamic DTI (dDTI) shows differing temporal activation patterns in
           post-exercise skeletal muscles
    • Authors: Conrad Rockel; Alireza Akbari; Dinesh A. Kumbhare; Michael D. Noseworthy
      Pages: 127 - 138
      Abstract: Object To assess post-exercise recovery of human calf muscles using dynamic diffusion tensor imaging (dDTI). Materials and methods DTI data (6 directions, b = 0 and 400 s/mm2) were acquired every 35 s from seven healthy men using a 3T MRI, prior to (4 volumes) and immediately following exercise (13 volumes, ~7.5 min). Exercise consisted of 5-min in-bore repetitive dorsiflexion-eversion foot motion with 0.78 kg resistance. Diffusion tensors calculated at each time point produced maps of mean diffusivity (MD), fractional anisotropy (FA), radial diffusivity (RD), and signal at b = 0 s/mm2 (S0). Region-of-interest (ROI) analysis was performed on five calf muscles: tibialis anterior (ATIB), extensor digitorum longus (EDL) peroneus longus (PER), soleus (SOL), and lateral gastrocnemius (LG). Results Active muscles (ATIB, EDL, PER) showed significantly elevated initial MD post-exercise, while predicted inactive muscles (SOL, LG) did not (p < 0.0001). The EDL showed a greater initial increase in MD (1.90 × 10−4mm2/s) than ATIB (1.03 × 10−4mm2/s) or PER (8.79 × 10−5 mm2/s) (p = 7.40 × 10−4), and remained significantly elevated across more time points than ATIB or PER. Significant increases were observed in post-exercise EDL S0 relative to other muscles across the majority of time points (p < 0.01 to p < 0.001). Conclusions dDTI can be used to differentiate exercise-induced changes between muscles. These differences are suggested to be related to differences in fiber composition.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0587-7
      Issue No: Vol. 30, No. 2 (2017)
       
  • Comparison of T1-weighted 2D TSE, 3D SPGR, and two-point 3D Dixon MRI for
           automated segmentation of visceral adipose tissue at 3 Tesla
    • Authors: Faezeh Fallah; Jürgen Machann; Petros Martirosian; Fabian Bamberg; Fritz Schick; Bin Yang
      Pages: 139 - 151
      Abstract: Objectives To evaluate and compare conventional T1-weighted 2D turbo spin echo (TSE), T1-weighted 3D volumetric interpolated breath-hold examination (VIBE), and two-point 3D Dixon-VIBE sequences for automatic segmentation of visceral adipose tissue (VAT) volume at 3 Tesla by measuring and compensating for errors arising from intensity nonuniformity (INU) and partial volume effects (PVE). Materials and methods The body trunks of 28 volunteers with body mass index values ranging from 18 to 41.2 kg/m2 (30.02 ± 6.63 kg/m2) were scanned at 3 Tesla using three imaging techniques. Automatic methods were applied to reduce INU and PVE and to segment VAT. The automatically segmented VAT volumes obtained from all acquisitions were then statistically and objectively evaluated against the manually segmented (reference) VAT volumes. Results Comparing the reference volumes with the VAT volumes automatically segmented over the uncorrected images showed that INU led to an average relative volume difference of −59.22 ± 11.59, 2.21 ± 47.04, and −43.05 ± 5.01 % for the TSE, VIBE, and Dixon images, respectively, while PVE led to average differences of −34.85 ± 19.85, −15.13 ± 11.04, and −33.79 ± 20.38 %. After signal correction, differences of −2.72 ± 6.60, 34.02 ± 36.99, and −2.23 ± 7.58 % were obtained between the reference and the automatically segmented volumes. A paired-sample two-tailed t test revealed no significant difference between the reference and automatically segmented VAT volumes of the corrected TSE (p = 0.614) and Dixon (p = 0.969) images, but showed a significant VAT overestimation using the corrected VIBE images. Conclusion Under similar imaging conditions and spatial resolution, automatically segmented VAT volumes obtained from the corrected TSE and Dixon images agreed with each other and with the reference volumes. These results demonstrate the efficacy of the signal correction methods and the similar accuracy of TSE and Dixon imaging for automatic volumetry of VAT at 3 Tesla.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0588-6
      Issue No: Vol. 30, No. 2 (2017)
       
  • Can MRI T 1 be used to detect early changes in 5xFAD Alzheimer’s
           mouse brain'
    • Authors: Nicholas G. Spencer; David P. Lovell; Kay Elderfield; Brian Austen; Franklyn A. Howe
      Pages: 153 - 163
      Abstract: Objectives In the present study, we have tested whether MRI T1 relaxation time is a sensitive marker to detect early stages of amyloidosis and gliosis in the young 5xFAD transgenic mouse, a well-established animal model for Alzheimer’s disease. Materials and methods 5xFAD and wild-type mice were imaged in a 4.7 T Varian horizontal bore MRI system to generate T1 quantitative maps using the spin-echo multi-slice sequence. Following immunostaining for glial fibrillary acidic protein, Iba-1, and amyloid-β, T1 and area fraction of staining were quantified in the posterior parietal and primary somatosensory cortex and corpus callosum. Results In comparison with age-matched wild-type mice, we observed first signs of amyloidosis in 2.5-month-old 5xFAD mice, and development of gliosis in 5-month-old 5xFAD mice. In contrast, MRI T1 relaxation times of young, i.e., 2.5- and 5-month-old, 5xFAD mice were not significantly different to those of age-matched wild-type controls. Furthermore, although disease progression was detectable by increased amyloid-β load in the brain of 5-month-old 5xFAD mice compared with 2.5-month-old 5xFAD mice, MRI T1 relaxation time did not change. Conclusions In summary, our data suggest that MRI T1 relaxation time is neither a sensitive measure of disease onset nor progression at early stages in the 5xFAD mouse transgenic mouse model.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0593-9
      Issue No: Vol. 30, No. 2 (2017)
       
  • Insight into the labeling mechanism of acceleration selective arterial
           spin labeling
    • Authors: Sophie Schmid; Esben T. Petersen; Matthias J. P. Van Osch
      Pages: 165 - 174
      Abstract: Objectives Acceleration selective arterial spin labeling (AccASL) is a spatially non-selective labeling technique, used in traditional ASL methods, which labels spins based on their flow acceleration rather than spatial localization. The exact origin of the AccASL signal within the vasculature is not completely understood. To obtain more insight into this, the acceleration selective module was performed followed by a velocity selective module, which is used in velocity selective arterial spin labeling (VS-ASL). Materials and methods Nine healthy volunteers were scanned with various combinations of the control and label conditions in both the acceleration and velocity selective module. The cut-off acceleration (0.59 m/s2) or velocity (2 cm/s) was kept constant in one module, while it was varied over a large range in the other module. With the right subtractions this resulted in AccASL, VS-ASL, combined AccASL and VS-ASL signal, and signal from one module with crushing from the other. Results The label created with AccASL has an overlap of approximately 50% in the vascular region with VS-ASL, but also originates from smaller vessels closer to the capillaries. Conclusion AccASL is able to label spins both in the macro- and meso-vasculature, as well as in the microvasculature.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0596-6
      Issue No: Vol. 30, No. 2 (2017)
       
  • Magnetic resonance imaging detection of multiple ischemic injury produced
           in an adult rat model of minor stroke followed by mild transient cerebral
           ischemia
    • Authors: Ursula I. Tuor; Min Qiao
      Pages: 175 - 188
      Abstract: Objectives To determine whether cumulative brain damage produced adjacent to a minor stroke that is followed by a mild transient ischemia is detectable with MRI and histology, and whether acute or chronic recovery between insults influences this damage. Materials and methods A minor photothrombotic (PT) stroke was followed acutely (1–2 days) or chronically (7 days) by a mild transient middle cerebral artery occlusion (tMCAO). MRI was performed after each insult, followed by final histology. Results The initial PT produced small hyperintense T2 and DW infarct lesions and peri-lesion regions of scattered necrosis and modestly increased T2. Following tMCAO, in a slice and a region adjacent to the PT, a region of T2 augmentation was observed when recovery between insults was acute but not chronic. Within the PT slice, a modest region of exacerbated T2 change proximate to the PT was also observed in the chronic group. Corresponding histological changes within regions of augmented T2 included increased vacuolation and cell death. Conclusion Within regions adjacent to an experimental minor stroke, a recurrence of a mild transient cerebral ischemia augmented T2 above increases produced by tMCAO alone, reflecting increased damage in this region. Exacerbation appeared broader with acute versus chronic recovery between insults.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0597-5
      Issue No: Vol. 30, No. 2 (2017)
       
  • Accelerating multi-echo water-fat MRI with a joint locally low-rank and
           spatial sparsity-promoting reconstruction
    • Authors: Felix Lugauer; Dominik Nickel; Jens Wetzl; Berthold Kiefer; Joachim Hornegger; Andreas Maier
      Pages: 189 - 202
      Abstract: Objectives Our aim was to demonstrate the benefits of using locally low-rank (LLR) regularization for the compressed sensing reconstruction of highly-accelerated quantitative water-fat MRI, and to validate fat fraction (FF) and \({R_2^*}\) relaxation against reference parallel imaging in the abdomen. Materials and methods Reconstructions using spatial sparsity regularization (SSR) were compared to reconstructions with LLR and the combination of both (LLR+SSR) for up to seven fold accelerated 3-D bipolar multi-echo GRE imaging. For ten volunteers, the agreement with the reference was assessed in FF and \({R_2^*}\) maps. Results LLR regularization showed superior noise and artifact suppression compared to reconstructions using SSR. Remaining residual artifacts were further reduced in combination with SSR. Correlation with the reference was excellent for FF with \(R^2\) = 0.99 (all methods) and good for \({R_2^*}\) with \(R^2\) = [0.93, 0.96, 0.95] for SSR, LLR and LLR+SSR. The linear regression gave slope and bias (%) of (0.99, 0.50), (1.01, 0.19) and (1.01, 0.10), and the hepatic FF/ \({R_2^*}\) standard deviation was 3.5%/12.1 s \(^{-1}\) , 1.9%/6.4 s \(^{-1}\) and 1.8%/6.3 s \(^{-1}\) for SSR, LLR and LLR+SSR, indicating the least bias and highest SNR for LLR+SSR. Conclusion A novel reconstruction using both spatial and spectral regularization allows obtaining accurate FF and \({R_2^*}\) maps for prospectively highly accelerated acquisitions.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0595-7
      Issue No: Vol. 30, No. 2 (2017)
       
  • K -space data processing for magnetic resonance elastography (MRE)
    • Authors: Nadège Corbin; Elodie Breton; Michel de Mathelin; Jonathan Vappou
      Pages: 203 - 213
      Abstract: Objective Magnetic resonance elastography (MRE) requires substantial data processing based on phase image reconstruction, wave enhancement, and inverse problem solving. The objective of this study is to propose a new, fast MRE method based on MR raw data processing, particularly adapted to applications requiring fast MRE measurement or high elastogram update rate. Materials and methods The proposed method allows measuring tissue elasticity directly from raw data without prior phase image reconstruction and without phase unwrapping. Experimental feasibility is assessed both in a gelatin phantom and in the liver of a porcine model in vivo. Elastograms are reconstructed with the raw MRE method and compared to those obtained using conventional MRE. In a third experiment, changes in elasticity are monitored in real-time in a gelatin phantom during its solidification by using both conventional MRE and raw MRE. Results The raw MRE method shows promising results by providing similar elasticity values to the ones obtained with conventional MRE methods while decreasing the number of processing steps and circumventing the delicate step of phase unwrapping. Limitations of the proposed method are the influence of the magnitude on the elastogram and the requirement for a minimum number of phase offsets. Conclusion This study demonstrates the feasibility of directly reconstructing elastograms from raw data.
      PubDate: 2017-04-01
      DOI: 10.1007/s10334-016-0594-8
      Issue No: Vol. 30, No. 2 (2017)
       
  • Influence of spatial resolution and contrast agent dosage on myocardial T1
           relaxation times
    • Authors: Edyta Blaszczyk; Agnieszka Töpper; Luisa Schmacht; Felix Wanke; Andreas Greiser; Jeanette Schulz-Menger; Florian von Knobelsdorff-Brenkenhoff
      Pages: 85 - 91
      Abstract: Objective Our aim was to study the influence of small variations in spatial resolution and contrast agent dosage on myocardial T1 relaxation time. Materials and methods Twenty-nine healthy volunteers underwent cardiovascular magnetic resonance at 3T twice, including a modified look-locker inversion recovery (MOLLI) technique—3(3)3(3)5—for T1 mapping. Native T1 was assessed in three spatial resolutions (voxel size 1.4 × 1.4 × 6, 1.6 × 1.6 × 6, 1.7 × 1.7 × 6 mm3), and postcontrast T1 after 0.1 and 0.2 mmol/kg gadobutrol. Partition coefficient was calculated based on myocardial and blood T1. T1 analysis was done per segment, per slice, and for the whole heart. Results Native T1 values did not differ with varying spatial resolution per segment (p = 0.116–0.980), per slice (basal: p = 0.772; middle: p = 0.639; apex: p = 0.276), and globally (p = 0.191). Postcontrast T1 values were significantly lower with higher contrast agent dosage (p < 0.001). The global partition coefficient was 0.43 ± 0.3 for 0.2 and 0.1 mmol gadobutrol (p = 0.079). Conclusion Related to the tested MOLLI technique at 3T, very small variations in spatial resolution (voxel sizes between 1.4 × 1.4 × 6 and 1.7 × 1.7 × 6 mm3) remained without effect on the native T1 relaxation times. Postcontrast T1 values were naturally shorter with higher contrast agent dosage while the partition coefficient remained constant. Further studies are necessary to test whether these conclusions hold true for larger matrix sizes and in larger cohorts.
      PubDate: 2017-02-01
      DOI: 10.1007/s10334-016-0581-0
      Issue No: Vol. 30, No. 1 (2017)
       
  • Erratum to: Thin film based semi-active resonant marker design for low
           profile interventional cardiovascular MRI devices
    • Authors: Engin Baysoy; Dursun Korel Yildirim; Cagla Ozsoy; Senol Mutlu; Ozgur Kocaturk
      Pages: 103 - 105
      PubDate: 2017-02-01
      DOI: 10.1007/s10334-016-0592-x
      Issue No: Vol. 30, No. 1 (2017)
       
  • Combined quantification of fatty infiltration, T 1 -relaxation times and T
           2 *-relaxation times in normal-appearing skeletal muscle of controls and
           dystrophic patients
    • Authors: Benjamin Leporq; Arnaud Le Troter; Yann Le Fur; Emmanuelle Salort-Campana; Maxime Guye; Olivier Beuf; Shahram Attarian; David Bendahan
      Abstract: Objectives To evaluate the combination of a fat–water separation method with an automated segmentation algorithm to quantify the intermuscular fatty-infiltrated fraction, the relaxation times, and the microscopic fatty infiltration in the normal-appearing muscle. Materials and methods MR acquisitions were performed at 1.5T in seven patients with facio-scapulo-humeral dystrophy and eight controls. Disease severity was assessed using commonly used scales for the upper and lower limbs. The fat–water separation method provided proton density fat fraction (PDFF) and relaxation times maps (T 2* and T 1). The segmentation algorithm distinguished adipose tissue and normal-appearing muscle from the T 2* map and combined active contours, a clustering analysis, and a morphological closing process to calculate the index of fatty infiltration (IFI) in the muscle compartment defined as the relative amount of pixels with the ratio between the number of pixels within IMAT and the total number of pixels (IMAT + normal appearing muscle). Results In patients, relaxation times were longer and a larger fatty infiltration has been quantified in the normal-appearing muscle. T 2* and PDFF distributions were broader. The relaxation times were correlated to the Vignos scale whereas the microscopic fatty infiltration was linked to the Medwin-Gardner-Walton scale. The IFI was linked to a composite clinical severity scale gathering the whole set of scales. Conclusion The MRI indices quantified within the normal-appearing muscle could be considered as potential biomarkers of dystrophies and quantitatively illustrate tissue alterations such as inflammation and fatty infiltration.
      PubDate: 2017-03-22
      DOI: 10.1007/s10334-017-0616-1
       
  • What are the true volumes of SEGA tumors' Reliability of planimetric
           and popular semi-automated image segmentation methods
    • Authors: Konrad Stawiski; Joanna Trelińska; Dobromiła Baranska; Iwona Dachowska; Katarzyna Kotulska; Sergiusz Jóźwiak; Wojciech Fendler; Wojciech Młynarski
      Abstract: Objective To evaluate the reliability of the standard planimetric methodology of volumetric analysis and three different open-source semi-automated approaches of brain tumor segmentation. Materials and methods The volumes of subependymal giant cell astrocytomas (SEGA) examined by 30 MRI studies of 10 patients from a previous everolimus-related trial (EMINENTS study) were estimated using four methods: planimetric method (modified MacDonald ellipsoid method), ITK-Snap (pixel clustering, geodesic active contours, region competition methods), 3D Slicer (level-set thresholding), and NIRFast (k-means clustering, Markov random fields). The methods were compared, and a trial simulation was performed to determine how the choice of approach could influence the final decision about progression or response. Results Intraclass correlation coefficient was high (0.95; 95% CI 0.91–0.98). The planimetric method always overestimated the size of the tumor, while virtually no mean difference was found between ITK-Snap and 3D Slicer (P = 0.99). NIRFast underestimated the volume and presented a proportional bias. During the trial simulation, a moderate level of agreement between all the methods (kappa 0.57–0.71, P < 0.002) was noted. Conclusion Semi-automated segmentation can ease oncological follow-up but the moderate level of agreement between segmentation methods suggests that the reference standard volumetric method for SEGA tumors should be revised and chosen carefully, as the selection of volumetry tool may influence the conclusion about tumor progression or response.
      PubDate: 2017-03-20
      DOI: 10.1007/s10334-017-0614-3
       
  • Long T2 suppression in native lung 3-D imaging using k-space reordered
           inversion recovery dual-echo ultrashort echo time MRI
    • Authors: Neville D. Gai; Ashkan A. Malayeri; David A. Bluemke
      Abstract: Objective Long T2 species can interfere with visualization of short T2 tissue imaging. For example, visualization of lung parenchyma can be hindered by breathing artifacts primarily from fat in the chest wall. The purpose of this work was to design and evaluate a scheme for long T2 species suppression in lung parenchyma imaging using 3-D inversion recovery double-echo ultrashort echo time imaging with a k-space reordering scheme for artifact suppression. Materials and methods A hyperbolic secant (HS) pulse was evaluated for different tissues (T1/T2). Bloch simulations were performed with the inversion pulse followed by segmented UTE acquisition. Point spread function (PSF) was simulated for a standard interleaved acquisition order and a modulo 2 forward-reverse acquisition order. Phantom and in vivo images (eight volunteers) were acquired with both acquisition orders. Contrast to noise ratio (CNR) was evaluated in in vivo images prior to and after introduction of the long T2 suppression scheme. Results The PSF as well as phantom and in vivo images demonstrated reduction in artifacts arising from k-space modulation after using the reordering scheme. CNR measured between lung and fat and lung and muscle increased from −114 and −148.5 to +12.5 and 2.8 after use of the IR-DUTE sequence. Paired t test between the CNRs obtained from UTE and IR-DUTE showed significant positive change (p < 0.001 for lung-fat CNR and p = 0.03 for lung-muscle CNR). Conclusion Full 3-D lung parenchyma imaging with improved positive contrast between lung and other long T2 tissue types can be achieved robustly in a clinically feasible time using IR-DUTE with image subtraction when segmented radial acquisition with k-space reordering is employed.
      PubDate: 2017-03-10
      DOI: 10.1007/s10334-017-0613-4
       
  • Influence of the cardiac cycle on pCASL: cardiac triggering of the
           end-of-labeling
    • Authors: Jasper Verbree; Matthias J. P. van Osch
      Abstract: Objective In arterial spin labeling (ASL), the cardiac cycle might adversely influence signal-stability by varying the amount of label created, labeling efficiency and/or transport times. Due to the long labeling duration in pseudo-Continuous ASL (pCASL), the blood labeled last contributes most to the ASLsignal. The present study investigated, using numerical simulations and in vivo experiments, the effect of the cardiac cycle on pCASL, thereby focusing on the end-of-labeling. Materials and methods In the in vivo experiments the end-of-labeling was timed to a specific cardiac phase while a long labeling duration of >7 s was used to isolate the influence of the lastly labeled spins on ASL-signal stability. Results Simulations showed dependence of the ASL-signal on the cardiac phase of the end-of-labeling, and that the variation in signal was more pronounced at lower heart rates. The ASL-signal variation was small (~4%), but could be effectively reduced by simulated end-of-labeling triggering. In vivo, no difference in mean CBF (p = 0.58) nor in CBF temporal-STD (p = 0.44) could be detected between triggered and non-triggered acquisitions. Conclusion Influence of the cardiac cycle on pCASL-signal stability is small and triggering the start-of-labeling and end-of-labeling can be considered not to have practical implications to improve stability.
      PubDate: 2017-03-09
      DOI: 10.1007/s10334-017-0611-6
       
  • A comparative study of the sensitivity of diffusion-related parameters
           obtained from diffusion tensor imaging, diffusional kurtosis imaging,
           q-space analysis and bi-exponential modelling in the early disease course
           (24 h) of hyperacute (6 h) ischemic stroke patients
    • Authors: Gaëtan Duchêne; Frank Peeters; André Peeters; Thierry Duprez
      Abstract: Objectives To compare the sensitivity and early temporal changes of diffusion parameters obtained from diffusion tensor imaging (DTI), diffusional kurtosis imaging (DKI), q-space analysis (QSA) and bi-exponential modelling in hyperacute stroke patients. Materials and methods A single investigational acquisition allowing the four diffusion analyses was performed on seven hyperacute stroke patients with a 3T system. The percentage change between ipsi- and contralateral regions were compared at admission and 24 h later. Two out of the seven patients were imaged every 6 h during this period. Results Kurtoses from both DKI and QSA were the most sensitive of the tested diffusion parameters in the few hours following ischemia. An early increase–maximum–decrease pattern of evolution was highlighted during the 24-h period for all parameters proportional to diffusion coefficients. A similar pattern was observed for both kurtoses in only one of two patients. Conclusion Our comparison was performed using identical diffusion encoding timings and on patients in the same stage of their condition. Although preliminary, our findings confirm those of previous studies that showed enhanced sensitivity of kurtosis. A fine time mapping of diffusion metrics in hyperacute stroke patients was presented which advocates for further investigations on larger animal or human cohorts.
      PubDate: 2017-03-06
      DOI: 10.1007/s10334-017-0612-5
       
  • Biomarkers from in vivo molecular imaging of breast cancer: pretreatment
           18 F-FDG PET predicts patient prognosis, and pretreatment DWI-MR predicts
           response to neoadjuvant chemotherapy
    • Authors: Francesca Gallivanone; Marta Maria Panzeri; Carla Canevari; Claudio Losio; Luigi Gianolli; Francesco De Cobelli; Isabella Castiglioni
      Abstract: Objective Human cancers display intra-tumor phenotypic heterogeneity and recent research has focused on developing image processing methods extracting imaging descriptors to characterize this heterogeneity. This work assesses the role of pretreatment 18F-FDG PET and DWI-MR with respect to the prognosis and prediction of neoadjuvant chemotherapy (NAC) outcomes when image features are used to characterize primitive lesions from breast cancer (BC). Materials and methods A retrospective protocol included 38 adult women with biopsy-proven BC. Patients underwent a pre-therapy 18F-FDG PET/CT whole-body study and a pre-therapy breast multi-parametric MR study. Patients were then referred for NAC treatment and then for surgical resection, with an evaluation of the therapy response. Segmentation methods were developed in order to identify functional volumes both on 18F-FDG PET images and ADC maps. Macroscopic and histogram features were extracted from the defined functional volumes. Results Our work demonstrates that macroscopic and histogram features from 18F-FDG PET are able to biologically characterize primitive BC, and define the prognosis. In addition, histogram features from ADC maps are able to predict the response to NAC. Conclusion Our work suggests that pre-treatment 18F-FDG PET and pre-treatment DWI-MR provide useful complementary information for biological characterization and NAC response prediction in BC.
      PubDate: 2017-02-28
      DOI: 10.1007/s10334-017-0610-7
       
  • Interpretation of cardiac wall motion from cine-MRI combined with
           parametric imaging based on the Hilbert transform
    • Authors: Narjes Benameur; Enrico Gianluca Caiani; Younes Arous; Nejmeddine ben Abdallah; Tarek Kraiem
      Abstract: Object The aim of this study was to test and validate the clinical impact of parametric amplitude images obtained using the Hilbert transform on the regional interpretation of cardiac wall motion abnormalities from cine-MR images by non-expert radiologists compared with expert consensus. Materials and methods Cine-MRI short-axis images obtained in 20 patients (10 with myocardial infarction, 5 with myocarditis and 5 with normal function) were processed to compute a parametric amplitude image for each using the Hilbert transform. Two expert radiologists blindly reviewed the cine-MR images to define a gold standard for wall motion interpretation for each left ventricular sector. Two non-expert radiologists reviewed and graded the same images without and in combination with parametric images. Grades assigned to each segment in the two separate sessions were compared with the gold standard. Results According to expert interpretation, 264/320 (82.5%) segments were classified as normal and 56/320 (17.5%) were considered abnormal. The accuracy of the non-expert radiologists’ grades compared to the gold standard was significantly improved by adding parametric images (from 87.2 to 94.6%) together with sensitivity (from 64.29 to 84.4%) and specificity (from 92 to 96.9%), also resulting in reduced interobserver variability (from 12.8 to 5.6%). Conclusion The use of parametric amplitude images based on the Hilbert transform in conjunction with cine-MRI was shown to be a promising technique for improvement of the detection of left ventricular wall motion abnormalities in less expert radiologists.
      PubDate: 2017-02-20
      DOI: 10.1007/s10334-017-0609-0
       
  • Track-weighted imaging methods: extracting information from a streamlines
           tractogram
    • Authors: Fernando Calamante
      Abstract: A whole-brain streamlines data-set (so-called tractogram) generated from diffusion MRI provides a wealth of information regarding structural connectivity in the brain. Besides visualisation strategies, a number of post-processing approaches have been proposed to extract more detailed information from the tractogram. One such approach is based on exploiting the information contained in the tractogram to generate track-weighted (TW) images. In the track-weighted imaging (TWI) approach, a very large number of streamlines are often generated throughout the brain, and an image is then computed based on properties of the streamlines themselves (e.g. based on the number of streamlines in each voxel, or their average length), or based on the values of an associated image (e.g. a diffusion anisotropy map, a T2 map) measured at the coordinates of the streamlines. This review article describes various approaches used to generate TW images and discusses the flexible formalism that TWI provides to generate a range of images with very different contrast, as well as the super-resolution properties of the resulting images. It also explains how this approach provides a powerful means to study structural and functional connectivity simultaneously. Finally, a number of key issues for its practical implementation are discussed.
      PubDate: 2017-02-08
      DOI: 10.1007/s10334-017-0608-1
       
 
 
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