Echo Planar Time-Resolved Imaging (EPTI) with Subspace Reconstruction and Optimized Spatiotemporal Encoding

Purpose: To develop new encoding and reconstruction techniques for fast multi-contrast quantitative imaging. Methods: The recently proposed Echo Planar Time-resolved Imaging (EPTI) technique can achieve fast distortion- and blurring-free multi-contrast quantitative imaging. In this work, a subspace reconstruction framework is developed to improve the reconstruction accuracy of EPTI at high encoding accelerations. The number of unknowns in the reconstruction is significantly reduced by modeling the temporal signal evolutions using low-rank subspace. As part of the proposed reconstruction approach, a B0-update algorithm and a shot-to-shot B0 variation correction method are developed to enable the reconstruction of high-resolution tissue phase images and to mitigate artifacts from shot-to-shot phase variations. Moreover, the EPTI concept is extended to 3D k-space for 3D GE-EPTI, where a new temporal-variant of CAIPI encoding is proposed to further improve performance. Results: The effectiveness of the proposed subspace reconstruction was demonstrated first in 2D GESE EPTI, where the reconstruction achieved higher accuracy when compared to conventional B0-informed GRAPPA. For 3D GE-EPTI, a retrospective undersampling experiment demonstrates that the new temporal-variant CAIPI encoding can achieve up to 72x acceleration with close to 2x reduction in reconstruction error when compared to conventional spatiotemporal-CAIPI encoding. In a prospective undersampling experiment, high-quality whole-brain T2* and QSM maps at 1 mm isotropic resolution was acquired in 52 seconds at 3T using 3D GE-EPTI with temporal-variant CAIPI encoding. Conclusion: The proposed subspace reconstruction and optimized temporal-variant CAIPI encoding can further improve the performance of EPTI for fast quantitative mapping

Wilson-Donaldson Stoneware Kiln Site (41DN19)

In July 1998, personnel from Archeological & Environmental Consultants volunteered one day to assist the Denton County Historical Commission in their investigation of the 1850-1880 Wilson-Donaldson stoneware kiln (41DN19) near Sharon Lake, Bryant Branch, and Hickory Creek in the upper Trinity River basin a few miles south-southeast of Denton, Texas. This is one of a number of 19th century stoneware potteries making saltglazed and natural clay slip vessels in Denton County, including the Cranston Pottery (41DN16), Roark Pottery (41DN18), Lambert Pottery (41DN74), and Serran Pottery (41DN75), all sites listed on the National register of Historic Places. The kiln and associated archaeological deposits were in an area being proposed for private development, and it was considered imperative that as much archaeological information be gathered from the site before it was disturbed or destroyed; subsequently, the main kiln at the site (Feature 1) was dismantled—hopefully to be reconstructed in the future—while the remainder of the archaeological deposits were destroyed and removed. During our short foray to the site, we produced a map of the various features at the site, including stoneware kilns, sherd waster piles, clay pits, and traces of structural remains in the vicinity of the other features. Drawings of the plan and vertical profile of Feature 1 were also completed at that time, along with surface collections of stoneware sherds from several features, supplemented with a few shovel tests to assess the character of the archaeological deposits and the excavation of a single 50 x 50 cm unit in the Feature 3 waster pile. In our work, we limited the recovery of artifacts to diagnostic rim sherds from the different vessel forms represented at the kiln, as well to any identified kiln furniture. The stoneware sherds at the Wilson-Donaldson kiln are almost exclusively exterior salt-glazed jars, jugs, churns, and bowls. About 61 percent of the sherds we collected are from ca. 1840-1860 salt-glazed vessels that have a dry interior surface. Interior and exterior salt-glazed sherds are rare (3 percent) in the assemblage, but they are associated with pre-1860 stoneware manufacture. Thirty-six percent are sherds from saltglazed vessels with a natural clay slip interior. It is likely that these vessels were made between 1860-1880, based on Lebo’s (1987:Tables 8-9 and 8- 10) seriation of stoneware interior and exterior glaze types and combinations. One sherd (0.5 percent) has a natural clay slip on both interior and exterior surfaces, and is most likely from a vessel made between 1860-1880, although examples are known from pre-1860 contexts. The Wilson-Donaldson kiln also manufactured clay elbow pipes along with stoneware vessels. None were recovered in our limited work at the site

Diffusion MR Tractography of the Heart

Histological studies have shown that the myocardium consists of an array of crossing helical fiber tracts. Changes in myocardial fiber architecture occur in ischemic heart disease and heart failure, and can be imaged non-destructively with diffusion-encoded MR. Several diffusion-encoding schemes have been developed, ranging from scalar measurements of mean diffusivity to a 6-dimensional imaging technique known as diffusion spectrum imaging or DSI. The properties of DSI make it particularly suited to the generation of 3-dimensional tractograms of myofiber architecture. In this article we review the physical basis of diffusion-tractography in the myocardium and the attributes of the available techniques, placing particular emphasis on DSI. The application of DSI in ischemic heart disease is reviewed, and the requisites for widespread clinical translation of diffusion MR tractography in the heart are discussed