Low‐power NMR volume selection by slicing z magnetization

A novel method for reducing the rf power requirements of selective pulses employed for z magnetization slice inversion in localized NMR spectroscopy is presented. Following slice preparation by the use of frequency‐incremented sine pulses, the slice gradient is reduced, which narrows the frequency width of the slice. This allows the use of relatively low‐power selective inversion pulses, an important consideration for in vivo applications. © Academic Press, Inc

Crypt stem cells as the cells-of-origin of intestinal cancer

Intestinal cancer is initiated by Wnt- pathway- activating mutations in genes such as adenomatous polyposis coli ( APC). As in most cancers, the cell of origin has remained elusive. In a previously established Lgr5 ( leucine- rich- repeat containing G- protein-coupled receptor 5) knockin mouse model, a tamoxifen- inducible Cre recombinase is expressed in long- lived intestinal stem cells(1). Here we show that deletion of Apc in these stem cells leads to their transformation within days. Transformed stem cells remain located at crypt bottoms, while fuelling a growing microadenoma. These microadenomas show unimpeded growth and develop into macroscopic adenomas within 3-5 weeks. The distribution of Lgr5(+) cells within stem- cell- derived adenomas indicates that a stem cell/ progenitor cell hierarchy is maintained in early neoplastic lesions. When Apc is deleted in short- lived transit- amplifying cells using a different cre mouse, the growth of the induced microadenomas rapidly stalls. Even after 30 weeks, large adenomas are very rare in these mice. We conclude that stem- cell- specific loss of Apc results in progressively growing neoplasia

Image-guided spine surgery: state of the art and future directions

Navigation technology is a widely available tool in spine surgery and has become a part of clinical routine in many centers. The issue of where and when navigation technology should be used is still an issue of debate. It is the aim of this study to give an overview on the current knowledge concerning the technical capabilities of image-guided approaches and to discuss possible future directions of research and implementation of this technique. Based on a Medline search total of 1,462 publications published until October 2008 were retrieved. The abstracts were scanned manually for relevance to the topics of navigated spine surgery in the cervical spine, the thoracic spine, the lumbar spine, as well as ventral spine surgery, radiation exposure, tumor surgery and cost-effectivity in navigated spine surgery. Papers not contributing to these subjects were deleted resulting in 276 papers that were included in the analysis. Image-guided approaches have been investigated and partially implemented into clinical routine in virtually any field of spine surgery. However, the data available is mostly limited to small clinical series, case reports or retrospective studies. Only two RCTs and one metaanalysis have been retrieved. Concerning the most popular application of image-guided approaches, pedicle screw insertion, the evidence of clinical benefit in the most critical areas, e.g. the thoracic spine, is still lacking. In many other areas of spine surgery, e.g. ventral spine surgery or tumor surgery, image-guided approaches are still in an experimental stage. The technical development of image-guided techniques has reached a high level as the accuracies that can be achieved technically meet the anatomical demands. However, there is evidence that the interaction between the surgeon (‘human factor’) and the navigation system is a source of inaccuracy. It is concluded that more effort needs to be spend to understand this interaction