Article

Advances in ultra-high field MRI for the clinical management of patients with brain tumors

Department of Radiology and Biomedical Imaging, University of California, San Francisco, California 94158-2330, USA.
Current opinion in neurology (Impact Factor: 5.73). 10/2011; 24(6):605-15. DOI: 10.1097/WCO.0b013e32834cd495
Source: PubMed

ABSTRACT The last 5 years have seen the number of ultra-high field (UHF; 7 T and beyond) MRI scanners nearly double. Benefits include improved specificity, better sensitivity for signal-starved compounds, and the ability to detect, quantify, and monitor tumor activity and treatment effects. This is especially important in the current climate in which new treatments alter established markers of tumor and the surrounding environment, confounding traditional response criteria.
Intra-tumoral heterogeneity and dramatic improvement in spatial localization have been observed with 7 and 8 T high-resolution T2-weighted and T2*-weighted imaging. This depiction of lesions that were not readily detected at lower field improved the classification of glioma. Sub-millimeter visualization of microvasculature has facilitated the detection of microbleeds associated with long-term effects of radiation. New metabolic markers seen at UHF may also assist in distinguishing tumor progression from treatment effect.
Although progress has been limited by technical challenges, initial experience has demonstrated the promise of 7-T MRI in advancing existing paradigms for diagnosing, monitoring, and managing patients with brain tumors. The success of these systems will depend upon what new information can be gained by UHF, rather than simply improving the quality of the current lower field standard.

0 Followers
 · 
129 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose To improve the radiofrequency (RF) field strength and uniformity in a local imaging region, individual RF transmitting phases were controlled in surface coil elements in a 7T transceive array coil; the RF field distribution was compared with the conventional in-phase approach at 7 T. Methods Optimal RF transmitting phases in the individual coil elements in a four-channel transceive array coil were numerically calculated using the electromagnetic (EM) field solver to obtain uniform RF field in a local imaging region. In 7 T phantom experiments, the RF field uniformity and mean SNR were evaluated on gradient echo images. In addition, a flip angle map was obtained by the double angle method. Results Experimental results clearly show that the EM calculation yielded an improved RF field strength and uniformity in the specific imaging region along the center of the coil array when the RF transmitting phase offset was 180° between the left and right rows of surface coil elements. In a 7 T experiment, B1 field uniformity and mean SNR with this phase offset were better than the other cases and the FA map showed a more focused and symmetric distribution as compared to other cases. Conclusions Even though the RF field distribution in the transceive array coil is still strongly affected by dielectric properties at 7 T, the 180° phase offset between the left and right rows of the coil elements gave the highest magnetic flux density in the specific imaging.
    12/2013; 2(4). DOI:10.1007/s13534-012-0075-6
  • [Show abstract] [Hide abstract]
    ABSTRACT: Die Einführung der Hochfeld-MRT ermöglicht in der neuroonkologischen Bildgebung bereits im Bereich der T1- und T2-gewichteten Bildgebung eine bessere Darstellung der Tumorstrukturen. Insbesondere aber die suszeptibilitätsgewichtete Bildgebung (SWI) und die Time-of-flight(TOF)-Angiographie profitieren in erhöhtem Maße von der hohen Feldstärke. Die durch die Hochfeldtechnologie mögliche Darstellung der Tumorgefäße in der MRT kann potenziell für das Monitoring antiangiogener Therapien genutzt werden. Zerebrale Metastasen können mit Hilfe der Hochfeldtechnologie potenziell früher entdeckt werden. Weiterhin ermöglicht die Hochfeldtechnologie die Anwendung neuer Techniken wie beispielsweise der Natriumbildgebung, welche einen weiteren Erkenntnisgewinn im Bereich der Tumorpathophysiologie erwarten lassen.
    Der Radiologe 05/2013; 53(5). DOI:10.1007/s00117-012-2347-7 · 0.41 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Well calibrated core–shell multifunctional nanoparticles for biomedical applications were synthesized by a multistep soft chemistry route. The core is composed of Gd(OH)CO3·H2O spheres prepared via a urea-based homogeneous precipitation technique, while the shell is a homogeneous thin silica layer embedded with the fluorescent dye rhodamine B (RhB) prepared via a modified Stöber process. The hybrid core–shell nanoparticles show a paramagnetic behavior with a specific saturation magnetization of 2.8 emu g−1. The nuclear magnetic resonance relaxation measurements reveal that these systems could be used as T1 and T2 magnetic resonance imaging (MRI) contrast agents. Also, the resulting core–shell nanoparticles are fluorescent due to the presence of RhB entrapped inside the silica shell. When incubated with the human cervical carcinoma (HeLa) cells the core–shell composite particles exhibit bright intracellular fluorescence, indicating their capability for optical imaging in biology. Furthermore, the incorporation of organic dyes inside the silica matrix yields outstanding advantages such as significantly improved photostability of the dye and reduced cytotoxicity due to the protection of biocompatible silica shell. These features demonstrate that the magnetofluorescent core–shell nanoparticles prepared in our work have the potential to serve as a versatile imaging tool for smart detection or diagnosis in future biomedical engineering.
    Journal of Materials Chemistry 01/2012; 22(38-38). DOI:10.1039/C2JM34508K · 7.44 Impact Factor
Show more