Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics.

PURPOSE: We compare the performance of eight parallel transmit (pTx) body arrays with up to 32 channels and a standard birdcage design. Excitation uniformity, local specific absorption rate (SAR), global SAR, and power metrics are analyzed in the torso at 3 T for radiofrequency (RF)-shimming and 2-spoke excitations. METHODS: We used a fast cosimulation strategy for field calculation in the presence of coupling between transmit channels. We designed spoke pulses using magnitude least squares optimization with explicit constraint of SAR and power and compared the performance of the different pTx coils using the L-curve method. RESULTS: PTx arrays outperformed the conventional birdcage coil in all metrics except peak and average power efficiency. The presence of coupling exacerbated this power efficiency problem. At constant excitation fidelity, the pTx array with 24 channels arranged in three z-rows could decrease local SAR more than 4-fold (2-fold) for RF-shimming (2-spoke) compared to the birdcage coil for pulses of equal duration. Multi-row pTx coils had a marked performance advantage compared to single row designs, especially for coronal imaging. CONCLUSION: PTx coils can simultaneously improve the excitation uniformity and reduce SAR compared to a birdcage coil when SAR metrics are explicitly constrained in the pulse design.

Comparison of RF body coils for MRI at 3 T: a simulation study using parallel transmission on various anatomical targets.

The performance of multichannel transmit coil layouts and parallel transmission (pTx) RF pulse design was evaluated with respect to transmit B1 (B1 (+)) homogeneity and specific absorption rate (SAR) at 3 T for a whole body coil. Five specific coils were modeled and compared: a 32-rung birdcage body coil (driven either in a fixed quadrature mode or a two-channel transmit mode), two single-ring stripline arrays (with either 8 or 16 elements), and two multi-ring stripline arrays (with two or three identical rings, stacked in the z axis and each comprising eight azimuthally distributed elements). Three anatomical targets were considered, each defined by a 3D volume representative of a meaningful region of interest (ROI) in routine clinical applications. For a given anatomical target, global or local SAR controlled pTx pulses were designed to homogenize RF excitation within the ROI. At the B1 (+) homogeneity achieved by the quadrature driven birdcage design, pTx pulses with multichannel transmit coils achieved up to about eightfold reduction in local and global SAR. When used for imaging head and cervical spine or imaging thoracic spine, the double-ring array outperformed all coils, including the single-ring arrays. While the advantage of the double-ring array became much less pronounced for pelvic imaging, with a substantially larger ROI, the pTx approach still provided significant gains over the quadrature birdcage coil. For all design scenarios, using the three-ring array did not necessarily improve the RF performance. Our results suggest that pTx pulses with multichannel transmit coils can reduce local and global SAR substantially for body coils while attaining improved B1 (+) homogeneity, particularly for a "z-stacked" double-ring design with coil elements arranged on two transaxial rings.

Regional conditions shape the food-energy-land nexus of low-carbon indoor farming.

Modern greenhouses and vertical farming projects promise increased food output per unit area relative to open-field farming. However, their high energy consumption calls for a low-carbon power supply such as solar photovoltaic and wind, which adds to cost and overall land footprint. Here we use geospatial and mathematical modelling to compare open-field and two indoor farming methods for vegetable production in nine city-regions chosen globally with varying land availability, climatic conditions and population density. We find that renewable electricity supply is more costly for greenhouses per unit energy demand satisfied, which is due to the greater fluctuation in their energy demand profile. However, greenhouses have a lower energy demand per unit food output, which makes them the least land-intensive option in most of the analysed regions. Our results challenge the land-savings claims of vertical farming compared with open-field production. We also show that regionalizing vegetable supply is feasible in most regions and give recommendations based on the regional context.

Making Healthy, Sustainable Diets Accessible and Achievable: A New Framework for Assessing the Nutrition, Environmental, and Equity Impacts of Packaged Foods.

There is a growing global consensus among food system experts that diets and how we source our foods must change. The sustainable nutrition community continues exploring the environmental impact and dietary value of foods. Packaged foods have been largely ignored within the dialogue, and if they are addressed, existing frameworks tend to label them all as "ultraprocessed" and uniformly discourage their consumption. This approach lacks the nuance needed to holistically evaluate packaged foods within recommended dietary patterns. Additionally, there is considerable diversity of opinion within the literature on these topics, especially on how best to improve nutrition security in populations most at risk of diet-related chronic disease. In support of addressing these challenges, 8 sustainability and nutrition experts were convened by Clif Bar & Company for a facilitated discussion on the urgent need to drive adoption of healthy, sustainable diets; the crucial role that certain packaged foods can play in helping make such diets achievable and accessible; and the need for actionable guidance around how to recommend and choose packaged foods that consider human, societal, and planetary health. This article summarizes the meeting discussion, which informed the development of a proposed framework based on guiding principles for defining sustainable, nutritious packaged foods across key nutrition, environmental, economic, and sociocultural well-being indicators. Although additional research is needed to substantiate specific metrics in order to operationalize the framework, it is intended to be a foundation from which to build and refine as science and measurement capabilities advance, and an important step toward broader adoption of healthy, sustainable diets.

BRN2 is a non-canonical melanoma tumor-suppressor.

While the major drivers of melanoma initiation, including activation of NRAS/BRAF and loss of PTEN or CDKN2A, have been identified, the role of key transcription factors that impose altered transcriptional states in response to deregulated signaling is not well understood. The POU domain transcription factor BRN2 is a key regulator of melanoma invasion, yet its role in melanoma initiation remains unknown. Here, in a BrafV600E PtenF/+ context, we show that BRN2 haplo-insufficiency promotes melanoma initiation and metastasis. However, metastatic colonization is less efficient in the absence of Brn2. Mechanistically, BRN2 directly induces PTEN expression and in consequence represses PI3K signaling. Moreover, MITF, a BRN2 target, represses PTEN transcription. Collectively, our results suggest that on a PTEN heterozygous background somatic deletion of one BRN2 allele and temporal regulation of the other allele elicits melanoma initiation and progression.

Genetic Heterogeneity of MET-Aberrant NSCLC and Its Impact on the Outcome of Immunotherapy.

INTRODUCTION: Robust data on the outcome of MET-aberrant NSCLC with nontargeted therapies are limited, especially in consideration of the heterogeneity of MET-amplified tumors (METamp). METHODS: A total of 337 tumor specimens of patients with MET-altered Union for International Cancer Control stage IIIB/IV NSCLC were analyzed using next-generation sequencing, fluorescence in situ hybridization, and immunohistochemistry. The evaluation focused on the type of MET aberration, co-occurring mutations, programmed death-ligand 1 expression, and overall survival (OS). RESULTS: METamp tumors (n = 278) had a high frequency of co-occurring mutations (>80% for all amplification levels), whereas 57.6% of the 59 patients with MET gene and exon 14 (METex14) tumors had no additional mutations. In the METamp tumors, with increasing gene copy number (GCN), the frequency of inactivating TP53 mutations increased (GCN < 4: 58.2%; GCN ≥ 10: 76.5%), whereas the frequency of KRAS mutations decreased (GCN < 4: 43.2%; GCN ≥ 10: 11.8%). A total of 10.1% of all the METamp tumors with a GCN ≥ 10 had a significant worse OS (4.0 mo; 95% CI: 1.9-6.0) compared with the tumors with GCN < 10 (12.0 mo; 95% confidence interval [CI]: 9.4-14.6). In the METamp NSCLC, OS with immune checkpoint inhibitor (ICI) therapy was significantly better compared with chemotherapy with 19.0 months (95% CI: 15.8-22.2) versus 8.0 months (95% CI: 5.8-10.2, p < 0.0001). No significant difference in median OS was found between ICI therapy and chemotherapy in the patients with METex14 (p = 0.147). CONCLUSIONS: METex14, METamp GCN ≥ 10, and METamp GCN < 10 represent the subgroups of MET-dysregulated NSCLC with distinct molecular and clinical features. The patients with METex14 do not seem to benefit from immunotherapy in contrast to the patients with METamp, which is of particular relevance for the prognostically poor METamp GCN ≥ 10 subgroup.

Effect of preoperative chemoradiation in addition to preoperative chemotherapy: a randomised trial in stage III non-small-cell lung cancer.

BACKGROUND: Preoperative chemotherapy improves survival in patients with stage III non-small-cell lung cancer (NSCLC) amenable to resection. We aimed to assess the additional effect of preoperative chemoradiation on tumour resection, pathological response, and survival in these patients. METHODS: Between Oct 1, 1995, and July 1, 2003, patients with stage IIIA-IIIB NSCLC and invasive mediastinal assessment from 26 participating institutions of the German Lung Cancer Cooperative Group (GLCCG) were randomly assigned to one of two treatment groups. The intervention group were scheduled to receive three cycles of cisplatin and etoposide, followed by twice-daily radiation with concurrent carboplatin and vindesine, and then surgical resection (those with positive resection margins or unresectable disease were offered further twice-daily radiotherapy). The control group were scheduled to receive three cycles of cisplatin and etoposide, followed by surgery, and then further radiotherapy. The primary endpoint was median progression-free survival (PFS) in patients eligible for treatment after randomisation. Secondary endpoints in patients eligible for treatment after randomisation were overall survival (OS) and the proportion of patients undergoing surgery. Secondary endpoints in patients with tumour resection were the proportion with negative resection margins, the proportion with complete resection, the proportion with histopathological response, and the proportion with mediastinal downstaging. Additionally, exploratory (not prespecified) post-hoc analyses in terms of PFS and OS were done on patients not amenable to resection and on further subgroups of patients undergoing resection. Analyses were by intention to treat. This trial is registered on the ClinicalTrials.gov website, number NCT 00176137. FINDINGS: 558 patients were randomly assigned. 34 patients did not meet inclusion criteria and were excluded. Of 524 eligible patients, 142 of 264 (54%) in the interventional group and 154 of 260 (59%) in the control group underwent surgery; 98 of 264 (37%) and 84 of 260 (32%) underwent complete resection. In patients with complete resection, the proportion of those with mediastinal downstaging (45 of 98 [46%] and 24 of 84 [29%], p=0.02) and pathological response (59 of 98 [60%] and 17 of 84 [20%], p<0.0001) favoured the interventional group. However, there was no difference in PFS (primary endpoint) between treatment groups-either in eligible patients (median PFS 9.5 months, range 1.0-117.0 [95% CI 8.3-11.2] vs 10.0 months, range 1.0-111.0 [8.9-11.5], 5-year PFS 16% [11-21] vs 14% [10-19], hazard ratio (HR) 0.99 [0.81-1.19], p=0.87), in those undergoing tumour resection, or in patients with complete resection. In both groups, 35% of patients undergoing surgery received a pneumonectomy (50/142 vs 54/154). In patients receiving a pneumonectomy, treatment-related mortality increased in the interventional group compared with the control group (7/50 [14%] vs 3/54 [6%]). INTERPRETATION: In patients with stage III NSCLC amenable to surgery, preoperative chemoradiation in addition to chemotherapy increases pathological response and mediastinal downstaging, but does not improve survival. After induction with chemoradiation, pneumonectomy should be avoided. FUNDING: German Cancer Aid (Bonn, Germany).

Lifestyle interventions in Muslim patients with metabolic syndrome-a feasibility study.

Obesity, metabolic syndrome, and type-2 diabetes mellitus are common in Muslim patients living in Germany, most of whom are of Turkish origin. Lifestyle interventions must be tailored to religion and ethnicity. We tested the body weight-reducing effect of a 30% calorie-reduced intake diet, adjusted to individual energy expenditure, eating habits, and food preferences in a Turkish-background cohort. Eighty subjects were randomized to activity advice only or to a step-count device to monitor and document physical activity before and after the 12-week intervention. Fifty-three patients completed the study. Lifestyle interventions were effective in these Muslim subjects. Body weight was reduced by 6%; activity monitoring provided a modestly increased effect to 8%. Blood glucose, HbA1c, triglycerides and cholesterol improved also substantially. Subjects receiving metformin could reduce their dosage. Our data show that Muslim Turkish patients respond to interventions if these are tailored to their needs.

Results from the 2004 Michigan Farm-to-School Survey.

The purpose of this study was to investigate Michigan school food service directors' interest in, and opportunities and barriers to, implementing a farm-to-school program. Farm-to-school may be a timely and innovative approach to improving the school food environment and helping food service directors meet their nutrition goals for school meals. Health and agriculture advocates have recognized the importance of farm-to-school in addressing health issues and creating opportunities for farmers and rural communities. Research subjects were 664 food service directors representing school districts across Michigan. Respondents (n = 383) reported a high degree of interest in sourcing food from local producers (73% reported being very interested or interested). Interest was significantly augmented (83%) when respondents were asked to assume that these foods were available through current vendors. Interest was independent of free/reduced lunch participation rate or school district location (rural, suburban, urban location). Food service directors expressed diverse motivations for their interest in farm-to-school, including supporting the local economy and community; accessing fresher, higher-quality food; and potentially increasing students' fruit and vegetable consumption. The most frequently reported barriers and concerns included cost, federal and state procurement regulations, reliable supply, seasonality of fruits and vegetables, and food safety. Michigan school food service directors appear ready to make linkages with local agriculture. However, there is need to address the concerns and barriers through education; inclusion of community partners, such as current vendors; funding; and state and federal policies that support local purchasing.

Alignment of Healthy Dietary Patterns and Environmental Sustainability: A Systematic Review.

To support food security for current and future generations, there is a need to understand the relation between sustainable diets and the health of a population. In recent years, a number of studies have investigated and compared different dietary patterns to better understand which foods and eating patterns have less of an environmental impact while meeting nutritional needs and promoting health. This systematic review (SR) of population-level dietary patterns and food sustainability extends and updates the SR that was conducted by the 2015 US Dietary Guidelines Advisory Committee, an expert committee commissioned by the federal government to inform dietary guidance as it relates to the committee's original conclusions. In the original SR, 15 studies met the criteria for inclusion; since then, an additional 8 studies have been identified and included. The relations between dietary intake patterns and both health and environmental outcomes were compared across studies, with methodologies that included modeling, life cycle assessment, and land use analysis. Across studies, consistent evidence indicated that a dietary pattern higher in plant-based foods (e.g., vegetables, fruits, legumes, seeds, nuts, whole grains) and lower in animal-based foods (especially red meat), as well as lower in total energy, is both healthier and associated with a lesser impact on the environment. This dietary pattern differs from current average consumption patterns in the United States. Our updated SR confirms and strengthens the conclusions of the original US Dietary Guidelines Advisory Committee SR, which found that adherence to several well-characterized dietary patterns, including vegetarian (with variations) diets, dietary guidelines-related diets, Mediterranean-style diets, the Dietary Approaches to Stop Hypertension (DASH) diet, and other sustainable diet scenarios, promotes greater health and has a less negative impact on the environment than current average dietary intakes.

Metabolic reprogramming during neuronal differentiation from aerobic glycolysis to neuronal oxidative phosphorylation.

How metabolism is reprogrammed during neuronal differentiation is unknown. We found that the loss of hexokinase (HK2) and lactate dehydrogenase (LDHA) expression, together with a switch in pyruvate kinase gene splicing from PKM2 to PKM1, marks the transition from aerobic glycolysis in neural progenitor cells (NPC) to neuronal oxidative phosphorylation. The protein levels of c-MYC and N-MYC, transcriptional activators of the HK2 and LDHA genes, decrease dramatically. Constitutive expression of HK2 and LDHA during differentiation leads to neuronal cell death, indicating that the shut-off aerobic glycolysis is essential for neuronal survival. The metabolic regulators PGC-1α and ERRγ increase significantly upon neuronal differentiation to sustain the transcription of metabolic and mitochondrial genes, whose levels are unchanged compared to NPCs, revealing distinct transcriptional regulation of metabolic genes in the proliferation and post-mitotic differentiation states. Mitochondrial mass increases proportionally with neuronal mass growth, indicating an unknown mechanism linking mitochondrial biogenesis to cell size.

Brachial plexus neurotization with donor phrenic nerves and its effect on pulmonary function.

OBJECT: To examine possible side effects of neurotizations in which the phrenic nerve was used, pulmonary function was analyzed pre- and postoperatively in patients with brachial plexus injury and root avulsions. METHODS: Twenty-three patients with complete brachial plexus palsy underwent neurotization of the musculocutaneous nerve, with the phrenic nerve as donor material. Patients who suffered lung contusions as part of the primary injury were excluded from this study. In 12 patients (five left-sided and seven right-sided neurotizations) pre- and postoperative functional parameters were compared and additional body plethysmography was performed more than 12 months postsurgery. Of the 23, no patient experienced pulmonary problems postoperatively. Nonetheless, pulmonary functional parameters showed a vital capacity in percent of the predicted value of 9.8 +/- 6.3% (mean +/- standard deviation [SD]) in all patients examined, which was a significant reduction (p = 0.0002). In right-sided phrenic nerve transfers this reduction was significant, at 14.3 +/- 3.3% (mean +/- SD), whereas left-sided transfers showed a nonsignificant reduction of 3.6 +/- 3.5% (mean +/- SD). The observed decrease in vital capacity (VC) correlates with the maximal inspiratory pressure (Pi(max)) as an indication of clinical significance. CONCLUSIONS: When the right phrenic nerve is used as a donor in neurotization of the musculocutaneous nerve, the patient incurs a higher risk of reduced pulmonary VC. If possible, the left phrenic nerve should be preferred. The Pi(max) has to be determined preoperatively to avoid any further decrease in the already reduced pulmonary function due to the initial injury.

Community food security: background and future directions.

Nutrition educators research, teach, and conduct outreach within the field of community food security (CFS), yet no clear consensus exists concerning what the field encompasses. Nutrition education needs to be integrated into the CFS movement for the fundamental reason that optimal health, well-being, and sustainability are at the core of both nutrition education and CFS. Establishing commonalities at the intersection of academic research, public policy development, and distinctive nongovernmental organizations expands opportunities for professional participation. Entry points for nutrition educators' participation are provided, including efforts dedicated to education, research, policy, programs and projects, and human rights.

Seven-tesla time-of-flight angiography using a 16-channel parallel transmit system with power-constrained 3-dimensional spoke radiofrequency pulse design.

OBJECTIVES: Ultrahigh magnetic fields of 7 T or higher have proven to significantly enhance the contrast in time-of-flight (TOF) imaging, one of the most commonly used non-contrast-enhanced magnetic resonance angiography techniques. Compared with lower field strength, however, the required radiofrequency (RF) power is increased at 7 T and the contrast obtained with a conventional head transmit RF coil is typically spatially heterogeneous.In this work, we addressed the contrast heterogeneity in multislab TOF acquisitions by optimizing the excitation flip angle homogeneity while constraining the RF power using 3-dimensional tailored RF pulses ("spokes") with a 16-channel parallel transmission system and a 16-channel transceiver head coil. MATERIALS AND METHODS: We investigated in simulations and in vivo experiments flip angle homogeneity and angiogram quality with a same 3-slab TOF protocol for different excitations including 1-, 2-, and 3-spoke parallel transmit RF pulses and compared the results with a circularly polarized (CP) phase setting similar to a birdcage excitation. B1 and B0 calibration maps were obtained in multiple slices, and the RF pulse for each slab was designed on the basis of 3 calibration slices located at the bottom/middle/top of each slab, respectively. By design, all excitations were computed to generate the same total RF power for the same flip angle. In 8 subjects, we quantified the excitation homogeneity and the distribution of the RF power to individual channels. In addition, we investigated the consequences of local flip angle variations at the junction between adjacent slabs as well as the impact of ΔB0 on image quality. RESULTS: The flip angle heterogeneity, expressed as the coefficient of variation, averaged over all volunteers and all slabs could be reduced from 29.4% for CP mode excitation to 14.1% for a 1-spoke excitation and to 7.3% for 2-spoke excitations. A separate detailed analysis shows only a marginal improvement for 3-spoke compared with the 2-spoke excitation. The strong improvement in flip angle homogeneity particularly impacted the junction between adjacent TOF slabs, where significant residual artifacts observed with 1-spoke excitation could be efficiently mitigated using a 2-spoke excitation with same RF power and same average flip angle. Although the total RF power is maintained at the same level than that in CP mode excitation, the energy distribution is fairly heterogeneous through the 16 transmit channels for 1- and 2-spoke excitations, with the highest energy for 1 channel being a factor of 2.4 (1 spoke) and 2.2 (2 spokes) higher than that in CP mode. In vivo experiments demonstrated the necessity for including ΔB0 spatial variations during 2-spoke RF pulse design, particularly in areas with strong local susceptibility variations such as the lower frontal lobe. CONCLUSIONS: Significant improvement in excitation fidelity leading to improved TOF contrast, particularly in the brain periphery, as well as smooth slab transitions can be achieved with 2-spoke excitation while maintaining the same excitation energy as that in CP mode. These results suggest that expanding parallel transmit methods, including the use of multidimensional spatially selective excitation, will also be very beneficial for other techniques, such as perfusion imaging.

Results from the 2009 Michigan farm to school survey: participation grows from 2004.

OBJECTIVE: This study investigated changes in Michigan school food service directors' farm to school (FTS) participation levels and perspectives since a 2004 survey and factors that would facilitate FTS expansion. DESIGN: Electronic survey census of all Michigan school food service directors. SETTING: Michigan kindergarten-12th grade schools. PARTICIPANTS: Food service directors of National School Lunch programs in Michigan. VARIABLES MEASURED: Survey respondents were asked about local food purchasing behaviors, interests, motivations, concerns, and barriers. ANALYSIS: Data were analyzed through descriptive statistics. Wilcoxon signed rank tests were calculated to compare 2004 and 2009 results. RESULTS: Participation in FTS was more than 3 times higher (41.5%) than in 2004 (10.6%), and the vast majority of school districts (77.0%) had taken at least 1 step to connect students with local food. Budget and cost issues were ranked higher as barriers to FTS than in 2004, but the desire to help Michigan farms had also substantially increased. Fresh and whole produce items were generally preferred for local procurement over frozen or canned items. CONCLUSIONS AND IMPLICATIONS: Education to reverse perceived limits of procurement regulations, food safety assurances, and strategies to mitigate tight school food budgets are needed to encourage FTS expansion.

Challenges and directions: an analysis of Genetic Analysis Workshop 17 data by collapsing rare variants within family data.

Recent studies suggest that the traditional case-control study design does not have sufficient power to discover rare risk variants. Two different methods-collapsing and family data-are suggested as alternatives for discovering these rare variants. Compared with common variants, rare variants have unique characteristics. In this paper, we assess the distribution of rare variants in family data. We notice that a large number of rare variants exist only in one or two families and that the association result is largely shaped by those families. Therefore we explore the possibility of integrating both the collapsing method and the family data method. This combinational approach offers a potential power boost for certain causal genes, including VEGFA, VEGFC, SIRT1, SREBF1, PIK3R3, VLDLR, PLAT, and FLT4, and thus deserves further investigation.

MRI-assisted PET motion correction for neurologic studies in an integrated MR-PET scanner.

UNLABELLED: Head motion is difficult to avoid in long PET studies, degrading the image quality and offsetting the benefit of using a high-resolution scanner. As a potential solution in an integrated MR-PET scanner, the simultaneously acquired MRI data can be used for motion tracking. In this work, a novel algorithm for data processing and rigid-body motion correction (MC) for the MRI-compatible BrainPET prototype scanner is described, and proof-of-principle phantom and human studies are presented. METHODS: To account for motion, the PET prompt and random coincidences and sensitivity data for postnormalization were processed in the line-of-response (LOR) space according to the MRI-derived motion estimates. The processing time on the standard BrainPET workstation is approximately 16 s for each motion estimate. After rebinning in the sinogram space, the motion corrected data were summed, and the PET volume was reconstructed using the attenuation and scatter sinograms in the reference position. The accuracy of the MC algorithm was first tested using a Hoffman phantom. Next, human volunteer studies were performed, and motion estimates were obtained using 2 high-temporal-resolution MRI-based motion-tracking techniques. RESULTS: After accounting for the misalignment between the 2 scanners, perfectly coregistered MRI and PET volumes were reproducibly obtained. The MRI output gates inserted into the PET list-mode allow the temporal correlation of the 2 datasets within 0.2 ms. The Hoffman phantom volume reconstructed by processing the PET data in the LOR space was similar to the one obtained by processing the data using the standard methods and applying the MC in the image space, demonstrating the quantitative accuracy of the procedure. In human volunteer studies, motion estimates were obtained from echo planar imaging and cloverleaf navigator sequences every 3 s and 20 ms, respectively. Motion-deblurred PET images, with excellent delineation of specific brain structures, were obtained using these 2 MRI-based estimates. CONCLUSION: An MRI-based MC algorithm was implemented for an integrated MR-PET scanner. High-temporal-resolution MRI-derived motion estimates (obtained while simultaneously acquiring anatomic or functional MRI data) can be used for PET MC. An MRI-based MC method has the potential to improve PET image quality, increasing its reliability, reproducibility, and quantitative accuracy, and to benefit many neurologic applications.

Farm-to-school programs: perspectives of school food service professionals.

OBJECTIVE: This qualitative study used a case study approach to explore the potential of farm-to-school programs to simultaneously improve children's diets and provide farmers with viable market opportunities. DESIGN: Semistructured interviews were the primary data collection strategy. SETTING: Seven farm-to-school programs in the Upper Midwest and Northeast regions of the United States. PARTICIPANTS: Seven school food service professionals, 7 farmers, and 4 food distributors recruited from 7 farm-to-school programs. PHENOMENON OF INTEREST: Interviews probed why farmers, school food service professionals, and food distributors participate in farm-to-school programs and how they characterize the opportunities and challenges to local school food procurement. ANALYSIS: Data were analyzed using thematic coding and data displays. RESULTS: School food service professionals described 3 motivators for buying locally grown food for their cafeterias: (1) "The students like it," (2) "The price is right," and (3) "We're helping our local farmer." Students' preference for locally grown food was related to food quality, influence of school staff, and relationships with farmers. Buying food directly from farmers and wholesalers was associated with lower prices and flexible specifications, and the "local feel." CONCLUSIONS AND IMPLICATIONS: Understanding school food service professionals' motivations for buying locally grown food is critical to the sustainability of farm-to-school programs.

Toward implementing an MRI-based PET attenuation-correction method for neurologic studies on the MR-PET brain prototype.

UNLABELLED: Several factors have to be considered for implementing an accurate attenuation-correction (AC) method in a combined MR-PET scanner. In this work, some of these challenges were investigated, and an AC method based entirely on the MRI data obtained with a single dedicated sequence was developed and used for neurologic studies performed with the MR-PET human brain scanner prototype. METHODS: The focus was on the problem of bone-air segmentation, selection of the linear attenuation coefficient for bone, and positioning of the radiofrequency coil. The impact of these factors on PET data quantification was studied in simulations and experimental measurements performed on the combined MR-PET scanner. A novel dual-echo ultrashort echo time (DUTE) MRI sequence was proposed for head imaging. Simultaneous MR-PET data were acquired, and the PET images reconstructed using the proposed DUTE MRI-based AC method were compared with the PET images that had been reconstructed using a CT-based AC method. RESULTS: Our data suggest that incorrectly accounting for the bone tissue attenuation can lead to large underestimations (>20%) of the radiotracer concentration in the cortex. Assigning a linear attenuation coefficient of 0.143 or 0.151 cm(-1) to bone tissue appears to give the best trade-off between bias and variability in the resulting images. Not identifying the internal air cavities introduces large overestimations (>20%) in adjacent structures. On the basis of these results, the segmented CT AC method was established as the silver standard for the segmented MRI-based AC method. For an integrated MR-PET scanner, in particular, ignoring the radiofrequency coil attenuation can cause large underestimations (i.e.,