1110 Improved real-time cine with the use of a 32-channel cardiac array and Karhunen-Loeve Transform filter

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this record.Leader-member exchange (LMX) theory proposes that leaders develop different quality relationships with those they manage and this is predictive of work performance. While LMX quality has been viewed as univalent (ranging from low to high quality), this paper proposes that it can also be bivalent in nature (i.e., coexisting positive and negative thoughts towards the relationship), which we refer to as LMX ambivalence. A survey measure of LMX ambivalence is developed, and through three validation and two main studies, it is shown to have construct, discriminant, and incremental predictive validity beyond that of LMX quality. Hypotheses concerning LMX ambivalence and task performance are tested in two main studies and show that (1) LMX ambivalence is negatively related to performance regardless of LMX quality, (2) high levels of perceived support from the organization (Study 1) or coworkers (Study 2) nullify the negative association between LMX ambivalence and performance, and (3) high LMX ambivalence leads to more negative affect and in turn lower task performance, but only when coworker support is low (Study 2). These results show the importance of viewing LMX quality not only in terms of its absolute level (low vs. high quality) but also as a bivalent construct where both positive and negative cognitions can coexist. They also demonstrate the value of social support in buffering the negative effects of LMX ambivalence. Furthermore, our findings extend a central tenet of LMX theory by implying that LMX quality varies not only within groups (i.e., LMX differentiation) but also within leader-follower dyads

Free Breathing Real-Time Cardiac Cine Imaging With Improved Spatial Resolution at 3 T

Objectives: The aim of this study was to evaluate free-breathing single-shot real-time cine imaging for functional cardiac imaging at 3 +/- with increased spatial resolution. Special emphasis of this study was placed on the influence of parallel imaging techniques. Materials and Methods: Gradient echo phantom images were acquired with GRAPPA and modified SENSE reconstruction using both integrated and separate reference scans as well as TGRAPPA and TSENSE. In vivo measurements were performed for GRAPPA reconstruction with an integrated and a separate reference scan, as well as TGRAPPA using balanced steady-state free precession protocols. Three clinical protocols, rtLRInt (T-res = 51.3 milliseconds; voxel, 2.5 x 5.0 x 10 mm(3)), rtMRSep (T-res = 48.8 milliseconds; voxel, 1.9 x 3.1 x 10 mm(3)), and rtHRSep ((Tres) = 48.3 milliseconds; voxel, 1.6 x 2.6 x 10 mm(3)), were investigated on 20 volunteers using GRAPPA reconstruction with internal as well as separate reference scans. End-diastolic volume, end-systolic volume, ejection fraction, peak ejection rate, peak filling rate, and myocardial mass were evaluated for the left ventricle and compared with an electrocardiogram-triggered segmented readout cine protocol used as standard of reference. All studies were performed at 3 T. Results: Phantom and in vivo data demonstrate that the combination of GRAPPA reconstruction with a separate reference scan provides an optimal compromise of image quality as well as spatial and temporal resolution. Functional values (P values) for the standard of reference, rtLRInt, rtMRSep, and rtHRSep end-diastolic volume were 141 +/- 24 mL, 138 +/- 21 mL, 138 +/- 19 mL, and 128 +/- 33 mL, respectively (P = 0.7, 0.7, 0.4); end-systolic volume, 55 +/- 15 mL, 61 +/- 14 mL, 58 +/- 12 mL, and 55 +/- 20 mL, respectively (P = 0.23, 0.43, 0.62); ejection fraction, 61% +/- 5%, 57% +/- 5%, 58% +/- 4%, and 56% +/- 8%, respectively (P = 0.01, 0.11, 0.06); peak ejection rate, 481 +/- 73 mL/s, 425 +/- 62 mL/s, 434 +/- 67 mL/s, and 381 +/- 86 mL/s, respectively (P = 0.03, 0.04, 0.01); peak filling rate, 555 +/- 80 mL/s, 480 +/- 70 mL/s, 500 +/- 70 mL/s, and 438 +/- 108 mL/s, respectively (P = 0.007, 0.05, 0.004); and myocardial mass, 137 +/- 26 g, 141 T 25 g, 141 +/- 23 g, and 130 +/- 31 g, respectively (P = 0.62, 0.54, 0.99). Conclusions: Using a separate reference scan and high acceleration factors up to R = 6, single-shot real-time cardiac imaging offers adequate temporal and spatial resolution for accurate assessment of global left ventricular function in free breathing with short examination times

Free Breathing Real-Time Cardiac Cine Imaging With Improved Spatial Resolution at 3 T

Objectives: The aim of this study was to evaluate free-breathing single-shot real-time cine imaging for functional cardiac imaging at 3 +/- with increased spatial resolution. Special emphasis of this study was placed on the influence of parallel imaging techniques. Materials and Methods: Gradient echo phantom images were acquired with GRAPPA and modified SENSE reconstruction using both integrated and separate reference scans as well as TGRAPPA and TSENSE. In vivo measurements were performed for GRAPPA reconstruction with an integrated and a separate reference scan, as well as TGRAPPA using balanced steady-state free precession protocols. Three clinical protocols, rtLRInt (T-res = 51.3 milliseconds; voxel, 2.5 x 5.0 x 10 mm(3)), rtMRSep (T-res = 48.8 milliseconds; voxel, 1.9 x 3.1 x 10 mm(3)), and rtHRSep ((Tres) = 48.3 milliseconds; voxel, 1.6 x 2.6 x 10 mm(3)), were investigated on 20 volunteers using GRAPPA reconstruction with internal as well as separate reference scans. End-diastolic volume, end-systolic volume, ejection fraction, peak ejection rate, peak filling rate, and myocardial mass were evaluated for the left ventricle and compared with an electrocardiogram-triggered segmented readout cine protocol used as standard of reference. All studies were performed at 3 T. Results: Phantom and in vivo data demonstrate that the combination of GRAPPA reconstruction with a separate reference scan provides an optimal compromise of image quality as well as spatial and temporal resolution. Functional values (P values) for the standard of reference, rtLRInt, rtMRSep, and rtHRSep end-diastolic volume were 141 +/- 24 mL, 138 +/- 21 mL, 138 +/- 19 mL, and 128 +/- 33 mL, respectively (P = 0.7, 0.7, 0.4); end-systolic volume, 55 +/- 15 mL, 61 +/- 14 mL, 58 +/- 12 mL, and 55 +/- 20 mL, respectively (P = 0.23, 0.43, 0.62); ejection fraction, 61% +/- 5%, 57% +/- 5%, 58% +/- 4%, and 56% +/- 8%, respectively (P = 0.01, 0.11, 0.06); peak ejection rate, 481 +/- 73 mL/s, 425 +/- 62 mL/s, 434 +/- 67 mL/s, and 381 +/- 86 mL/s, respectively (P = 0.03, 0.04, 0.01); peak filling rate, 555 +/- 80 mL/s, 480 +/- 70 mL/s, 500 +/- 70 mL/s, and 438 +/- 108 mL/s, respectively (P = 0.007, 0.05, 0.004); and myocardial mass, 137 +/- 26 g, 141 T 25 g, 141 +/- 23 g, and 130 +/- 31 g, respectively (P = 0.62, 0.54, 0.99). Conclusions: Using a separate reference scan and high acceleration factors up to R = 6, single-shot real-time cardiac imaging offers adequate temporal and spatial resolution for accurate assessment of global left ventricular function in free breathing with short examination times

Using a whole-body 31P birdcage transmit coil and 16-element receive array for human cardiac metabolic imaging at 7T.

PURPOSE: Cardiac phosphorus magnetic resonance spectroscopy (31P-MRS) provides unique insight into the mechanisms of heart failure. Yet, clinical applications have been hindered by the restricted sensitivity of the surface radiofrequency-coils normally used. These permit the analysis of spectra only from the interventricular septum, or large volumes of myocardium, which may not be meaningful in focal disease. Löring et al. recently presented a prototype whole-body (52 cm diameter) transmit/receive birdcage coil for 31P at 7T. We now present a new, easily-removable, whole-body 31P transmit radiofrequency-coil built into a patient-bed extension combined with a 16-element receive array for cardiac 31P-MRS. MATERIALS AND METHODS: A fully-removable (55 cm diameter) birdcage transmit coil was combined with a 16-element receive array on a Magnetom 7T scanner (Siemens, Germany). Electro-magnetic field simulations and phantom tests of the setup were performed. In vivo maps of B1+, metabolite signals, and saturation-band efficiency were acquired across the torsos of eight volunteers. RESULTS: The combined (volume-transmit, local receive array) setup increased signal-to-noise ratio 2.6-fold 10 cm below the array (depth of the interventricular septum) compared to using the birdcage coil in transceiver mode. The simulated coefficient of variation for B1+ of the whole-body coil across the heart was 46.7% (surface coil 129.0%); and the in vivo measured value was 38.4%. Metabolite images of 2,3-diphosphoglycerate clearly resolved the ventricular blood pools, and muscle tissue was visible in phosphocreatine (PCr) maps. Amplitude-modulated saturation bands achieved 71±4% suppression of phosphocreatine PCr in chest-wall muscles. Subjects reported they were comfortable. CONCLUSION: This easy-to-assemble, volume-transmit, local receive array coil combination significantly improves the homogeneity and field-of-view for metabolic imaging of the human heart at 7T

Combined 23 Na and 13 C imaging at 3.0 Tesla using a single‐tuned large FOV birdcage coil

Purpose: An unmet need in carbon‐13 (13C)‐MRI is a transmit system that provides uniform excitation across a large FOV and can accommodate patients of wide‐ranging body habitus. Due to the small difference between the resonant frequencies, sodium‐23 (23Na) coil developments can inform 13C coil design while being simpler to assess due to the higher naturally abundant 23Na signal. Here we present a removable 23Na birdcage, which also allows operation as a 13C abdominal coil. Methods: We demonstrate a quadrature‐driven 4‐rung 23Na birdcage coil of 50 cm in length for both 23Na and 13C abdominal imaging. The coil transmit efficiencies and B 1 + maps were compared to a linearly driven 13C Helmholtz‐based (clamshell) coil. SNR was investigated with 23Na and 13C data using an 8‐channel 13C receive array within the 23Na birdcage. Results: The 23Na birdcage longitudinal FOV was > 40 cm, whereas the 13C clamshell was < 32 cm. The transmit efficiency of the birdcage at the 23Na frequency was 0.65 µT/sqrt(W), similar to the clamshell for 13C. However, the coefficient of variation of 23Na‐ B 1 + was 16%, nearly half that with the 13C clamshell. The 8‐channel 13C receive array combined with the 23Na birdcage coil generated a greater than twofold increase in 23Na‐SNR from the central abdomen compared with the birdcage alone. Discussion: This 23Na birdcage coil has a larger FOV and improved B 1 + uniformity when compared to the widely used clamshell coil design while also providing similar transmit efficiency. The coil has the potential to be used for both 23Na and 13C imaging

Hyperpolarized 13C-MRI of Tumor Metabolism Demonstrates Early Metabolic Response to Neoadjuvant Chemotherapy in Breast Cancer

Purpose: To compare hyperpolarized carbon-13 (13C)-MRI with dynamic contrast-enhanced MRI (DCE-MRI) for detecting early treatment response in breast cancer. Materials and Methods: In this institutional review board-approved prospective study, one woman with triple-negative breast cancer (age 49) underwent 13C-MRI following injection of hyperpolarized [1-13C]pyruvate and DCE-MRI at 3 T at baseline and after a single cycle of neoadjuvant therapy. The 13C-lactate/13C-pyruvate ratio derived from hyperpolarized 13C-MRI and the pharmacokinetic parameters Ktrans and kep derived from DCE-MRI were compared, before and after treatment. Results: Exchange of the 13C-label between injected hyperpolarized [1-13C]pyruvate and the endogenous lactate pool was demonstrated, catalyzed by the enzyme lactate dehydrogenase. After one cycle of neoadjuvant chemotherapy, a 34% reduction in the 13C-lactate/13C-pyruvate ratio was shown to correctly identify the patient as a responder to therapy, which was subsequently confirmed by a complete pathologic response. However, DCE-MRI showed an increase in the pharmacokinetic parameters Ktrans (132%) and kep (31%), which could be incorrectly interpreted as a poor response to treatment. Conclusion: Hyperpolarized 13C-MRI successfully identified response in breast cancer after a single cycle of neoadjuvant chemotherapy and may improve response prediction when used in conjunction with multiparametric proton MRI.This work was supported by a Wellcome Trust Strategic Award, Cancer Research UK (CRUK; Grants C8742/A18097, C19212/ A16628, C19212/A911376, and C197/A16465), the Austrian Science Fund (Grant J4025-B26), the CRUK Cambridge Centre, the CRUK & Engineering and Physical Sciences Research Council Cancer Imaging Centre in Cambridge and Manchester, the Mark Foundation for Cancer Research and Cancer Research UK Cambridge Centre (Grant C9685/A25177), CRUK National Cancer Imaging Translational Accelerator Award, Addenbrooke’s Charitable Trust, the National Institute for Health Research Cambridge Biomedical Research Centre, Cambridge Experimental Cancer Medicine Centre, and Cambridge University Hospitals National Health Service Foundation Trust

Imaging breast cancer using hyperpolarized carbon-13 MRI.

Our purpose is to investigate the feasibility of imaging tumor metabolism in breast cancer patients using 13C magnetic resonance spectroscopic imaging (MRSI) of hyperpolarized 13C label exchange between injected [1-13C]pyruvate and the endogenous tumor lactate pool. Treatment-naïve breast cancer patients were recruited: four triple-negative grade 3 cancers; two invasive ductal carcinomas that were estrogen and progesterone receptor-positive (ER/PR+) and HER2/neu-negative (HER2-), one grade 2 and one grade 3; and one grade 2 ER/PR+ HER2- invasive lobular carcinoma (ILC). Dynamic 13C MRSI was performed following injection of hyperpolarized [1-13C]pyruvate. Expression of lactate dehydrogenase A (LDHA), which catalyzes 13C label exchange between pyruvate and lactate, hypoxia-inducible factor-1 (HIF1α), and the monocarboxylate transporters MCT1 and MCT4 were quantified using immunohistochemistry and RNA sequencing. We have demonstrated the feasibility and safety of hyperpolarized 13C MRI in early breast cancer. Both intertumoral and intratumoral heterogeneity of the hyperpolarized pyruvate and lactate signals were observed. The lactate-to-pyruvate signal ratio (LAC/PYR) ranged from 0.021 to 0.473 across the tumor subtypes (mean ± SD: 0.145 ± 0.164), and a lactate signal was observed in all of the grade 3 tumors. The LAC/PYR was significantly correlated with tumor volume (R = 0.903, P = 0.005) and MCT 1 (R = 0.85, P = 0.032) and HIF1α expression (R = 0.83, P = 0.043). Imaging of hyperpolarized [1-13C]pyruvate metabolism in breast cancer is feasible and demonstrated significant intertumoral and intratumoral metabolic heterogeneity, where lactate labeling correlated with MCT1 expression and hypoxia

Iterative Learning for Machine Tools Using a Convex Optimisation Approach

Dynamic, quasi-static and motion control deviations lead to nonlinear but systematic tracking errors. It is shown that these errors can be reduced significantly by adjusting the set points using an optimization based iterative learning approach. This method uses either values obtained from internal encoders or alternatively tool center point measurements. The approach is presented, discussed and validated using simulation and measurement results.ISSN:2212-827