Motion-resolved fat-fraction mapping with whole-heart free-running multiecho GRE and pilot tone.

To develop a free-running 3D radial whole-heart multiecho gradient echo (ME-GRE) framework for cardiac- and respiratory-motion-resolved fat fraction (FF) quantification. (N <sub>TE</sub> = 8) readouts optimized for water-fat separation and quantification were integrated within a continuous non-electrocardiogram-triggered free-breathing 3D radial GRE acquisition. Motion resolution was achieved with pilot tone (PT) navigation, and the extracted cardiac and respiratory signals were compared to those obtained with self-gating (SG). After extra-dimensional golden-angle radial sparse parallel-based image reconstruction, FF, R <sub>2</sub> *, and B <sub>0</sub> maps, as well as fat and water images were generated with a maximum-likelihood fitting algorithm. The framework was tested in a fat-water phantom and in 10 healthy volunteers at 1.5 T using N <sub>TE</sub> = 4 and N <sub>TE</sub> = 8 echoes. The separated images and maps were compared with a standard free-breathing electrocardiogram (ECG)-triggered acquisition. The method was validated in vivo, and physiological motion was resolved over all collected echoes. Across volunteers, PT provided respiratory and cardiac signals in agreement (r = 0.91 and r = 0.72) with SG of the first echo, and a higher correlation to the ECG (0.1% of missed triggers for PT vs. 5.9% for SG). The framework enabled pericardial fat imaging and quantification throughout the cardiac cycle, revealing a decrease in FF at end-systole by 11.4% ± 3.1% across volunteers (p < 0.0001). Motion-resolved end-diastolic 3D FF maps showed good correlation with ECG-triggered measurements (FF bias of -1.06%). A significant difference in free-running FF measured with N <sub>TE</sub> = 4 and N <sub>TE</sub> = 8 was found (p < 0.0001 in sub-cutaneous fat and p < 0.01 in pericardial fat). Free-running fat fraction mapping was validated at 1.5 T, enabling ME-GRE-based fat quantification with N <sub>TE</sub> = 8 echoes in 6:15 min

Natively fat-suppressed 5D whole-heart MRI with a radial free-running fast-interrupted steady-state (FISS) sequence at 1.5T and 3T.

To implement, optimize, and test fast interrupted steady-state (FISS) for natively fat-suppressed free-running 5D whole-heart MRI at 1.5 tesla (T) and 3T. FISS was implemented for fully self-gated free-running cardiac- and respiratory-motion-resolved radial imaging of the heart at 1.5T and 3T. Numerical simulations and phantom scans were performed to compare fat suppression characteristics and to determine parameter ranges (number of readouts [NR] per FISS module and TR) for effective fat suppression. Subsequently, free-running FISS data were collected in 10 healthy volunteers and images were reconstructed with compressed sensing. All acquisitions were compared with a continuous balanced steady-state free precession version of the same sequence, and both fat suppression and scan times were analyzed. Simulations demonstrate a variable width and location of suppression bands in FISS that were dependent on TR and NR. For a fat suppression bandwidth of 100 Hz and NR ≤ 8, simulations demonstrated that a TR between 2.2 ms and 3.0 ms is required at 1.5T, whereas a range of 3.0 ms to 3.5 ms applies at 3T. Fat signal increases with NR. These findings were corroborated in phantom experiments. In volunteers, fat SNR was significantly decreased using FISS compared with balanced steady-state free precession (P < 0.05) at both field strengths. After protocol optimization, high-resolution (1.1 mm <sup>3</sup> ) 5D whole-heart free-running FISS can be performed with effective fat suppression in under 8 min at 1.5T and 3T at a modest scan time increase compared to balanced steady-state free precession. An optimal FISS parameter range was determined enabling natively fat-suppressed 5D whole-heart free-running MRI with a single continuous scan at 1.5T and 3T, demonstrating potential for cardiac imaging and noncontrast angiography

Isozymatic and morphological diversity in the races of maize of Mexico

To determine the relationships and genetic diversity among the Mexican races of maize, 209 accessions representing 59 races were analyzed for 21 enzyme systems encoded by 37 loci; 154 out of the 209 accessions were grown in multiple locations and seasons in Mexico and 47 morphological characters were measured. A very high level of variation among and within the Mexican races was found. However; more than 65% of the alleles found in the accessions studied are rare, occurring at frequencies below 0.01. In addition, some populations have low levels of genetic diversity and have values of genetic differentiation similar to selfing crops. Most of the accessions with low values of genetic diversity are specialty varieties

Isozymatic and morphological diversity in the races of maize of Mexico

To determine the relationships and genetic diversity among the Mexican races of maize, 209 accessions representing 59 races were analyzed for 21 enzyme systems encoded by 37 loci; 154 out of the 209 accessions were grown in multiple locations and seasons in Mexico and 47 morphological characters were measured. A very high level of variation among and within the Mexican races was found. However; more than 65% of the alleles found in the accessions studied are rare, occurring at frequencies below 0.01. In addition, some populations have low levels of genetic diversity and have values of genetic differentiation similar to selfing crops. Most of the accessions with low values of genetic diversity are specialty varieties

Racial diversity of maize in Brazil and adjacent areas

The races of southern and eastern South America are described in several of the Races of Maize Bulletins, as well as in a pioneering work by Hugh Cutler. Basically, there appear to be eight essentially distinct types of maize that have contributed to the diversity that has been collected there. These include: (1) a wide assortment of commercial races and some of the more productive Indigenous races that can be subdivided into six subgroups: (a) the commercial dent and semi-dent races of Brazil, Caingang, Morot , the Brazilian Catetos and Cristals; (b) the Cateto and Cristal Sulinos; (c) Cristalino and Dentado Comercial from Chile (d) Camelia, the lowland Bolivian Flints and Flours, and the Cateto Nortistas; (e) Canario de Ocho of Uruguay, Cateto Grande, and Moroti Precoce; (f) Tusín from Brazil. Many races of this group appear to be the most valuable for breeding programs. Seven other groups include: (2) Lenha, the Cravos, Cateto Sulino Grosso, and Choclero; (3) the introduced, commercial races, Argentino and Hickory King; (4) Cristalino Norteño, Canario de Ocho from Argentina, Dulce Golden Bantam, and Dulce Evergreen from Chile, all apparently related to U.S. Northern Flints such as Longfellow; (5) the races of the highlands of northwestern Argentina, including the Capias, Chulpi, Culli, Oke, Morocho and Harinoso Tarapaqueno from Chile; (6) Curagua and Curagua Grande from Chile; (7) Pororo and the Guaraní popcorns, Avat Piching and Avat Piching Ih ; (8) The interlocked races from the interior lowlands, Entrela♦ado, Piricinco, and the Coroicos. Araucano from Chile and Cateto Sulino Precoce from Argentina do not show clear relationships to the other races studied. This report uses morphological data, geographic data, and isozyme-allele-frequency data to characterize the relationships among previously-described races of maize from the region. Allelic variation among and within races and racial groups is utilized to attempt to infer historical relationships among maize types throughout the region

Racial diversity of maize in Brazil and adjacent areas

The races of southern and eastern South America are described in several of the Races of Maize Bulletins, as well as in a pioneering work by Hugh Cutler. Basically, there appear to be eight essentially distinct types of maize that have contributed to the diversity that has been collected there. These include: (1) a wide assortment of commercial races and some of the more productive Indigenous races that can be subdivided into six subgroups: (a) the commercial dent and semi-dent races of Brazil, Caingang, Morotí, the Brazilian Catetos and Cristals; (b) the Cateto and Cristal Sulinos; (c) Cristalino and Dentado Comercial from Chile (d) Camelia, the lowland Bolivian Flints and Flours, and the Cateto Nortistas; (e) Canario de Ocho of Uruguay, Cateto Grande, and Moroti Precoce; (f) Tusón from Brazil. Many races of this group appear to be the most valuable for breeding programs. Seven other groups include: (2) Lenha, the Cravos, Cateto Sulino Grosso, and Choclero; (3) the introduced, commercial races, Argentino and Hickory King; (4) Cristalino Norteño, Canario de Ocho from Argentina, Dulce Golden Bantam, and Dulce Evergreen from Chile, all apparently related to U.S. Northern Flints such as Longfellow; (5) the races of the highlands of northwestern Argentina, including the Capias, Chulpi, Culli, Oke, Morocho and Harinoso Tarapaqueno from Chile; (6) Curagua and Curagua Grande from Chile; (7) Pororo and the Guaraní popcorns, Avatí Pichingá and Avatí Pichingá Ihú; (8) The interlocked races from the interior lowlands, Entrelaçado, Piricinco, and the Coroicos. Araucano from Chile and Cateto Sulino Precoce from Argentina do not show clear relationships to the other races studied. This report uses morphological data, geographic data, and isozyme-allele-frequency data to characterize the relationships among previously-described races of maize from the region. Allelic variation among and within races and racial groups is utilized to attempt to infer historical relationships among maize types throughout the region