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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  [2336 journals]
  • Automated assessment of thigh composition using machine learning for Dixon
           magnetic resonance images
    • Authors: Yu Xin Yang; Mei Sian Chong; Laura Tay; Suzanne Yew; Audrey Yeo; Cher Heng Tan
      Pages: 723 - 731
      Abstract: Objectives To develop and validate a machine learning based automated segmentation method that jointly analyzes the four contrasts provided by Dixon MRI technique for improved thigh composition segmentation accuracy. Materials and methods The automatic detection of body composition is formulized as a three-class classification issue. Each image voxel in the training dataset is assigned with a correct label. A voxel classifier is trained and subsequently used to predict unseen data. Morphological operations are finally applied to generate volumetric segmented images for different structures. We applied this algorithm on datasets of (1) four contrast images, (2) water and fat images, and (3) unsuppressed images acquired from 190 subjects. Results The proposed method using four contrasts achieved most accurate and robust segmentation compared to the use of combined fat and water images and the use of unsuppressed image, average Dice coefficients of 0.94 ± 0.03, 0.96 ± 0.03, 0.80 ± 0.03, and 0.97 ± 0.01 has been achieved to bone region, subcutaneous adipose tissue (SAT), inter-muscular adipose tissue (IMAT), and muscle respectively. Conclusion Our proposed method based on machine learning produces accurate tissue quantification and showed an effective use of large information provided by the four contrast images from Dixon MRI.
      PubDate: 2016-10-01
      DOI: 10.1007/s10334-016-0547-2
      Issue No: Vol. 29, No. 5 (2016)
  • Coronary MR angiography at 3T: fat suppression versus water-fat separation
    • Authors: Maryam Nezafat; Markus Henningsson; David P. Ripley; Nathalie Dedieu; Gerald Greil; John P. Greenwood; Peter Börnert; Sven Plein; René M. Botnar
      Pages: 733 - 738
      Abstract: Objectives To compare Dixon water-fat suppression with spectral pre-saturation with inversion recovery (SPIR) at 3T for coronary magnetic resonance angiography (MRA) and to demonstrate the feasibility of fat suppressed coronary MRA at 3T without administration of a contrast agent. Materials and methods Coronary MRA with Dixon water-fat separation or with SPIR fat suppression was compared on a 3T scanner equipped with a 32-channel cardiac receiver coil. Eight healthy volunteers were examined. Contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), right coronary artery (RCA), and left anterior descending (LAD) coronary artery sharpness and length were measured and statistically compared. Two experienced cardiologists graded the visual image quality of reformatted Dixon and SPIR images (1: poor quality to 5: excellent quality). Results Coronary MRA images in healthy volunteers showed improved contrast with the Dixon technique compared to SPIR (CNR blood-fat: Dixon = 14.9 ± 2.9 and SPIR = 13.9 ± 2.1; p = 0.08, CNR blood-myocardium: Dixon = 10.2 ± 2.7 and SPIR = 9.11 ± 2.6; p = 0.1). The Dixon method led to similar fat suppression (fat SNR with Dixon: 2.1 ± 0.5 vs. SPIR: 2.4 ± 1.2, p = 0.3), but resulted in significantly increased SNR of blood (blood SNR with Dixon: 19.9 ± 4.5 vs. SPIR: 15.5 ± 3.1, p < 0.05). This means the residual fat signal is slightly lower with the Dixon compared to the SIPR technique (although not significant), while the SNR of blood is significantly higher with the Dixon technique. Vessel sharpness of the RCA was similar for Dixon and SPIR (57 ± 7 % vs. 56 ± 9 %, p = 0.2), while the RCA visualized vessel length was increased compared to SPIR fat suppression (107 ± 21 vs. 101 ± 21 mm, p < 0.001). For the LAD, vessel sharpness (50 ± 13 % vs. 50 ± 7 %, p = 0.4) and vessel length (92 ± 46 vs. 90 ± 47 mm, p = 0.4) were similar with both techniques. Consequently, the Dixon technique resulted in an improved visual score of the coronary arteries in the water fat separated images of healthy subjects (RCA: 4.6 ± 0.5 vs. 4.1 ± 0.7, p = 0.01, LAD: 4.1 ± 0.7 vs. 3.5 ± 0.8, p = 0.007). Conclusions Dixon water-fat separation can significantly improve coronary artery image quality without the use of a contrast agent at 3T.
      PubDate: 2016-10-01
      DOI: 10.1007/s10334-016-0550-7
      Issue No: Vol. 29, No. 5 (2016)
  • Scan time minimization in hepatic diffusion-weighted imaging: evaluation
           of the simultaneous multislice acceleration technique with different
           acceleration factors and gradient preparation schemes
    • Authors: Jana Taron; Petros Martirosian; Nina F. Schwenzer; Michael Erb; Thomas Kuestner; Jakob Weiß; Ahmed Othman; Mike Notohamiprodjo; Konstantin Nikolaou; Christina Schraml
      Pages: 739 - 749
      Abstract: Objective To evaluate simultaneous multislice (sms) accelerated diffusion-weighted imaging (DWI) of the liver in comparison to conventional sequences. Materials and methods Ten volunteers underwent DWI of the liver at 1.5 T. Four different sms-accelerated sequences with monopolar and bipolar gradient preparation (MP, BP) and acceleration factors 2 and 3 (sms2-DWI, sms3-DWI) were compared to conventional DWI (c-DWI). Image quality criteria rated on a 5-point Likert scale (5 = excellent), image quality sum scores (maximum 120), and ADC were compared using Friedman test and Dunn-Bonferroni post hoc test. Bland–Altman plots were calculated for ADC comparison. p values <0.05 were considered significant. Results Sms2-DWI offered scan time minimization of 67 % without significant difference in image quality (sum score: sms2-DWI MP/BP: 97 ± 8/92 ± 9; c-DWI MP/BP: 99 ± 8/97 ± 8). Sms3-DWI offered slight additional scan time minimization with significantly inferior image quality (sum score: sms3-DWI MP/BP: 75 ± 14/69 ± 14; p < 0.001). MP preparation provided slightly higher image quality in sms-DWI without statistical significance. ADC in sms-DWI were significantly lower (sms2-DWI MP 1.01 × 10−3 mm2/s; c-DWI MP 1.20 × 10−3 mm2/s; p < 0.001). Conclusion Sms2-DWI provides considerable scan time minimization without significant shortcomings in image quality. Sms3-DWI provides significantly inferior image quality without further scan time minimization. Potentially lower ADC in sms-DWI should be considered in clinical routine.
      PubDate: 2016-10-01
      DOI: 10.1007/s10334-016-0553-4
      Issue No: Vol. 29, No. 5 (2016)
  • Intravoxel incoherent motion analysis of abdominal organs: computation of
           reference parameters in a large cohort of C57Bl/6 mice and correlation to
           microvessel density
    • Authors: Christian Eberhardt; Moritz C. Wurnig; Andrea Wirsching; Cristina Rossi; Markus Rottmar; Pinar S. Özbay; Lukas Filli; Mickael Lesurtel; Andreas Boss
      Pages: 751 - 763
      Abstract: Objective Diffusion-weighted magnetic resonance imaging (DW-MRI) combined with intravoxel incoherent motion (IVIM) analysis may be applied for assessment of organ lesions, diffuse parenchymal pathologies, and therapy monitoring. The aim of this study was to determine IVIM reference parameters of abdominal organs for translational research in a large cohort of C57Bl/6 laboratory mice. Materials and methods Anesthetized mice (n = 29) were measured in a 4.7 T small-animal MR scanner with a diffusion-weighted echo-planar imaging sequence at the \(b\) -values 0, 13, 24, 55, 107, 260, 514, 767, 1020 s/mm2. IVIM analysis was conducted on the liver, spleen, renal medulla and cortex, pancreas, and small bowel with computation of the true tissue diffusion coefficient \(D_{\text{t}}\) , the perfusion fraction \(f_{\text{p}}\) , and the pseudodiffusion coefficient \(D_{\text{p}}\) . Microvessel density (MVD) was assessed by immunohistochemistry (IHC) against panendothelial cell antigen CD31. Results Mean values of the different organs [ \(D_{\text{t}}\) (10−3 mm2/s); \(f_{\text{p}}\) (%); \(D_{\text{p}}\) (10−3 mm2/s); MVD (MV/mm2)]: liver 1.15 ± 0.14; 14.77 ± 6.15; 50.28 ± 33.21, 2008.48 ± 419.43, spleen 0.55 ± 0.12; 9.89 ± 5.69; 24.46 ± 17.31; n.d., renal medulla 1.50 ± 0.20; 14.63 ± 4.07; 35.50 ± 18.01; 1231.88 ± 290.61, renal cortex 1.34 ± 0.18; 10.83 ± 3.70; 16.74 ± 6.74; 810.09 ± 193.50, pancreas 1.23 ± 0.22; 20.12 ± 7.46; 29.35 ± 17.82, 591.15 ± 86.25 and small bowel 1.06 ± 0.13; 16.48 ± 3.63; 15.31 ± 7.00; 420.50 ± 168.42. Unlike \(D_{\text{t}}\) and \(f_{\text{p}}\) , \(D_{\text{p}}\) correlates significantly with MVD (r = 0.90, p = 0.037). Conclusion This systematic evaluation of murine abdominal organs with IVIM and MVD analysis allowed to establish reference parameters for future DW-MRI translational research studies on small-animal disease models.
      PubDate: 2016-10-01
      DOI: 10.1007/s10334-016-0540-9
      Issue No: Vol. 29, No. 5 (2016)
  • Glioma vessel abnormality quantification using time-of-flight MR
    • Authors: Maddalena Strumia; Wilfried Reichardt; Ori Staszewski; Dieter Henrik Heiland; Astrid Weyerbrock; Irina Mader; Michael Bock
      Pages: 765 - 775
      Abstract: Objectives To differentiate between abnormal tumor vessels and regular brain vasculature using new quantitative measures in time-of-flight (TOF) MR angiography (MRA) data. Materials and methods In this work time-of-flight (TOF) MR angiography data are acquired in 11 glioma patients to quantify vessel abnormality. Brain vessels are first segmented with a new algorithm, efficient monte-carlo image-analysis for the location of vascular entity (EMILOVE), and are then characterized in three brain regions: tumor, normal-appearing contralateral brain, and the total brain volume without the tumor. For characterization local vessel orientation angles and the dot product between local orientation vectors are calculated and averaged in the 3 regions. Additionally, correlation with histological and genetic markers is performed. Results Both the local vessel orientation angles and the dot product show a statistically significant difference (p < 0.005) between tumor vessels and normal brain vasculature. Furthermore, the connection to both histology and the gene expression of the tumor can be found—here, the measures were compared to the proliferation marker Ki-67 [MIB] and genome-wide expression analysis. The results in a subgroup indicate that the dot product measure may be correlated with activated genetic pathways. Conclusion It is possible to define a measure of vessel abnormality based on local vessel orientation angles which can differentiate between normal brain vasculature and glioblastoma vessels.
      PubDate: 2016-10-01
      DOI: 10.1007/s10334-016-0558-z
      Issue No: Vol. 29, No. 5 (2016)
  • A novel alternative to classify tissues from T 1 and T 2 relaxation times
           for prostate MRI
    • Authors: Jorge Zavala Bojorquez; Stéphanie Bricq; François Brunotte; Paul M. Walker; Alain Lalande
      Pages: 777 - 788
      Abstract: Objective To segment and classify the different attenuation regions from MRI at the pelvis level using the T 1 and T 2 relaxation times and anatomical knowledge as a first step towards the creation of PET/MR attenuation maps. Materials and methods Relaxation times were calculated by fitting the pixel-wise intensities of acquired T 1- and T 2-weighted images from eight men with inversion-recovery and multi-echo multi-slice spin-echo sequences. A decision binary tree based on relaxation times was implemented to segment and classify fat, muscle, prostate, and air (within the body). Connected component analysis and an anatomical knowledge-based procedure were implemented to localize the background and bone. Results Relaxation times at 3 T are reported for fat (T 1 = 385 ms, T 2 = 121 ms), muscle (T 1 = 1295 ms, T 2 = 40 ms), and prostate (T 1 = 1700 ms, T 2 = 80 ms). The relaxation times allowed the segmentation–classification of fat, prostate, muscle, and air, and combined with anatomical knowledge, they allowed classification of bone. The good segmentation–classification of prostate [mean Dice similarity score (mDSC) = 0.70] suggests a viable implementation in oncology and that of fat (mDSC = 0.99), muscle (mDSC = 0.99), and bone (mDSCs = 0.78) advocates for its implementation in PET/MR attenuation correction. Conclusion Our method allows the segmentation and classification of the attenuation-relevant structures required for the generation of the attenuation map of PET/MR systems in prostate imaging: air, background, bone, fat, muscle, and prostate.
      PubDate: 2016-10-01
      DOI: 10.1007/s10334-016-0562-3
      Issue No: Vol. 29, No. 5 (2016)
  • 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
      PubDate: 2016-10-12
      DOI: 10.1007/s10334-016-0592-x
  • Reproducibility of locus coeruleus and substantia nigra imaging with
           neuromelanin sensitive MRI
    • Authors: Jason Langley; Daniel E. Huddleston; Christine J. Liu; Xiaoping Hu
      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: 2016-09-29
      DOI: 10.1007/s10334-016-0590-z
  • A comparison of fitting algorithms for diffusion-weighted MRI data
           analysis using an intravoxel incoherent motion model
    • Authors: Roberta Fusco; Mario Sansone; Antonella Petrillo
      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: 2016-09-26
      DOI: 10.1007/s10334-016-0591-y
  • 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
      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: 2016-09-16
      DOI: 10.1007/s10334-016-0588-6
  • Dynamic DTI (dDTI) shows differing temporal activation patterns in
           post-exercise skeletal muscles
    • Authors: Conrad Rockel; Alireza Akbari; Dinesh A. Kumbhare; Michael D. Noseworthy
      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: 2016-09-13
      DOI: 10.1007/s10334-016-0587-7
  • 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
      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: 2016-09-13
      DOI: 10.1007/s10334-016-0589-5
  • 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
      Abstract: Objectives A new microfabrication method to produce low profile radio frequency (RF) resonant markers on catheter shafts was developed. A semi-active RF resonant marker incorporating a solenoid and a plate capacitor was constructed on the distal shaft of a 5 Fr guiding catheter. The resulting device can be used for interventional cardiovascular MRI procedures. Materials and methods Unlike current semi-active device visualization techniques that require rigid and bulky analog circuit components (capacitor and solenoid), we fabricated a low profile RF resonant marker directly on guiding the catheter surface by thin film metal deposition and electroplating processes using a modified physical vapor deposition system. Results The increase of the overall device profile thickness caused by the semi-active RF resonant marker (130 µm thick) was lowered by a factor of 4.6 compared with using the thinnest commercial non-magnetic and rigid circuit components (600 µm thick). Moreover, adequate visibility performance of the RF resonant marker in different orientations and overall RF safety were confirmed through in vitro experiments under MRI successfully. Conclusion The developed RF resonant marker on a clinical grade 5 Fr guiding catheter will enable several interventional congenital heart disease treatment procedures under MRI.
      PubDate: 2016-09-07
      DOI: 10.1007/s10334-016-0586-8
  • ESMRMB 2016, 33rd Annual Scientific Meeting, Vienna, AT, September 29 -
           October 1: Author Index
    • PubDate: 2016-09-01
      DOI: 10.1007/s10334-016-0572-1
  • ESMRMB 2016, 33rd Annual Scientific Meeting, Vienna, AT, September
           29–October 1: Abstracts, Friday
    • PubDate: 2016-09-01
      DOI: 10.1007/s10334-016-0569-9
  • ESMRMB 2016, 33rd Annual Scientific Meeting, Vienna, AT, September
           29–October 1: Abstracts, Thursday
    • PubDate: 2016-09-01
      DOI: 10.1007/s10334-016-0568-x
  • ESMRMB 2016, 33rd Annual Scientific Meeting, Vienna, AT, September 29 –
           October 1: Abstracts, Saturday
    • PubDate: 2016-09-01
      DOI: 10.1007/s10334-016-0570-3
  • ESMRMB 2016, 33rd Annual Scientific Meeting, Vienna, AT, September 29 –
           October 1: ePoster / Paper Poster / Clinical Review Poster / Software
    • PubDate: 2016-09-01
      DOI: 10.1007/s10334-016-0571-2
  • Comparison of two quantitative proton density mapping methods in multiple
    • Authors: René-Maxime Gracien; Sarah C. Reitz; Marlies Wagner; Christoph Mayer; Steffen Volz; Stephanie-Michelle Hof; Vinzenz Fleischer; Amgad Droby; Helmuth Steinmetz; Sergiu Groppa; Elke Hattingen; Johannes C. Klein; Ralf Deichmann
      Abstract: Objective Proton density (PD) mapping requires correction for the receive profile (RP), which is frequently performed via bias-field correction. An alternative RP-mapping method utilizes a comparison of uncorrected PD-maps and a value ρ(T1) directly derived from T1-maps via the Fatouros equation. This may be problematic in multiple sclerosis (MS), if respective parameters are only valid for healthy brain tissue. We aimed to investigate whether the alternative method yields correct PD values in MS patients. Materials/methods PD mapping was performed on 27 patients with relapsing-remitting MS and 27 healthy controls, utilizing both methods, yielding reference PD values (PDref, bias-field method) and PDalt (alternative method). Results PDalt-values closely matched PDref, both for patients and controls. In contrast, ρ(T1) differed by up to 3 % from PDref, and the voxel-wise correlation between PDref and ρ(T1) was reduced in a patient subgroup with a higher degree of disability. Still, discrepancies between ρ(T1) and PDref were almost identical across different tissue types, thus translating into a scaling factor, which cancelled out during normalization to 100 % in CSF, yielding a good agreement between PDalt and PDref. Conclusion RP correction utilizing the auxiliary parameter ρ(T1) derived via the Fatouros equation provides accurate PD results in MS patients, in spite of discrepancies between ρ(T1) and actual PD values.
      PubDate: 2016-08-20
      DOI: 10.1007/s10334-016-0585-9
  • 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
      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: 2016-08-20
      DOI: 10.1007/s10334-016-0581-0
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