Armin Michael Nagel¹, Michael Bock¹, Christian Hartmann², Lars Gerigk¹, Jan-Oliver Neumann², Marc-André Weber², Martin Bendszus², Alexander Radbruch², Wolfgang Wick², Heinz-Peter Schlemmer¹, Wolfhard Semmler¹, and Armin Biller^2
1German Cancer Research Center, Heidelberg, Germany, ²University Hospital Heidelberg, Germany

In this work 16 patients suffering from different brain tumors (14 WHO grade I – IV and 2 metastases) were examined, to evaluate if relaxation-weighted ²³Na-MRI can provide information for tumor grading. All glioblastomas (WHO grade IV) showed higher signal intensities in relaxation-weighted imaging than the WHO grad I - III tumors. Regression analysis yielded a positive correlation between the relaxation-weighted ²³Na-MRI signal and the MIB-1 proliferation rate, a histological tumor marker. No correlation was found for the total ²³Na-signal.

Fernando Emilio Boada¹, Mary Phillips², Yongxian Qian³, and David Kupfer^2
1Radiology and Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States, ²Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States, ³Radiology, University of Pittsburgh, Pittsburgh, PA, United States

We demonstrate an imaging protocol for concurrent, in vivo, mapping of brain lithium and sodium concentration and present evidence that brain sodium concentration is normal on lithium-treated, euthymic, bipolar disorder subjects.

Friedrich Wetterling^1,2, Lindsay Gallagher³, William Holmes³, I. Mhairi MacRae³, and Andrew J. Fagan^1,4
1School of Physics, University of Dublin, Dublin, Ireland, ²Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Germany, ³Glasgow Experimental MRI Centre, University of Glasgow, Glasgow, United Kingdom, ⁴Centre for Advanced Medical Imaging, St. James's Hospital, Dublin, Ireland

The validity of the perfusion-diffusion mismatch in acute stroke diagnosis has been challenged recently, and an alternative approach to identifying penumbral tissue is desirable. A custom-built dual-tuned surface coil was used to obtain high-quality 1H-DWI and 23Na images in the acute phase of a rat stroke (n=6). The mismatch between the perfusion deficit and ischaemic damage determined from histology was used to define core and penumbral tissue regions at ~5hrs after stroke. The 23Na signal evolved differently in both regions, supporting the hypothesis that under-perfused regions which have not yet exhibited an increase in 23Na signal above normal levels indicate penumbral tissue.

Friedrich Wetterling¹, Andre Rennings², Raffi Kalayciyan¹, Dominique M. Corteville¹, Simon Konstandin¹, and Lothar R. Schad^1
1Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Germany, ²General and Theoretical Electrical Engineering, University of Duisburg-Essen, Duisburg, Germany

An asymmetric birdcage resonator was integrated into the 3T MRI system and tested in conjunction with a receive-only surface coil for human Na MRI. An up to date unseen B1 homogeneity was demonstrated by the possibility to acquire the world-wide first whole body 23Na image of a male human being. Furthermore, a two-fold SNR benefit of the dual resonator system over a state-of-the-art double-tuned 1H/23Na quadrature birdcage resonator was measured on the example of a human brain scan.

Florian Martin Meise¹, Jens Groebner¹, Armin M. Nagel¹, Reiner Umathum¹, Helmut Stark², Stefan H. Hoffmann¹, Wolfhard Semmler¹, and Michael Bock^1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Stark Contrast GmbH - MR Coils Research, Erlangen, Germany

In this study we designed a ¹⁷O phased array coil (¹⁷O-PA) with 30 ¹⁷O receive elements and a ¹⁷O transmit coil for ¹⁷O brain imaging at 7Tesla. The improvement in imaging quality achieved by a ¹⁷O phased array coil system can then be used in future patient studies to improve the image resolution or to shorten scan times during inhalation of the ¹⁷O-gas.

Stefan H Hoffmann¹, Armin M Nagel¹, Florian M Meise¹, Reiner Umathum¹, and Michael Bock^1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

Cellular energy production is closely connected to the metabolization of oxygen (O₂) to water. Direct ¹⁷O-MRI can assess the in vivo H₂¹⁷O concentration metabolized from inhaled ¹⁷O gas. However, the MR-sensitivity of the ¹⁷O nucleus (I = 5/2) is poor. Information on the relaxation parameters is therefore crucial for optimizing the imaging process. In this study we measured the in vivo ¹⁷O relaxation times in the human brain (B₀ = 7T) to optimize imaging protocols for CMRO₂ measurements. Non-localized detection (T₁, T₂) was carried out in 10 healthy volunteers and 3D T₂^* determination and anatomical mapping to ¹H images was performed in one subject.

Xiao-Hong Zhu¹, James Chen², Tsang-Wei Tu², Wei Chen¹, and Sheng-Kwei Song^2
1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, 55455, United States, ²Department of Radiology, Washington University School of Medicine, St Louis, MO 63110, USA, United States

Deficits or abnormalities in cerebral oxidative metabolism and perfusion have been linked to many brain disorders and diseases. Direct measurements of the cerebral metabolic rate of oxygen (CMRO₂) and perfusion (CBF) can provide valuable information for diagnosis and treatment of the disease. An in vivo ¹⁷O MRS imaging (MRSI) approach at high/ultrahigh fields has been developed recently for non-invasive mapping of CMRO₂ and CBF in small animals such as rats and cats. However, mice provide a more popular preclinical model for studying numerous brain diseases. Imaging CMRO₂ in the mouse brain presents new challenges and opportunities for the ¹⁷O-MR based CMRO₂ imaging technique. In this study, we explored the feasibility and new utility of the ¹⁷O-MR imaging approach for studying abnormal CMRO₂ and CBF in the mouse brain with a middle cerebral artery (MCA) occlusion.

Sankaran Subramanian¹, Nallathamby Devasahayam¹, Shingo Matsumoto¹, and Murali C Krishna^1
1National Cancer Institute, National Institute of Health, Bethesda, MD, United States

Two main approaches are currently in vogue for time-domain spectroscopic EPR imaging. The first one is Single Point Imaging involving global phase encoding which gives high resolution images, where the oximetry, however, is a T2* based approach relying on apparent line widths. The second approach for EPR oximetric imaging utilizes the conventional 90°--180° Spin-Echo pulse and filtered back-projection. The image is T2-weighted but the resolution is subject to susceptibility broadening. A novel time-domain spectroscopic EPR imaging approach, that is a unique combination of the above-mentioned techniques, is presented here. It provides quantitative T2 –based oximetry combined with line-width-independent high resolution.

Lingzhi Hu¹, Junjie Chen¹, Shelton D Caruthers¹, Gregory M Lanza¹, and Samuel A Wickline^1
1Washington University, St. Louis, MO, United States

We demonstrate the application of PFC nanoemulsion as a blood oxygen pressure probe with use of a novel blood enhanced saturation recovery like (BESR) pulse sequence. Compared to the traditional Look-Locker sequence, the BESR sequence is insensitive to B1 and B0 field inhomogeneity and pulsatile in-flow effects. Compared to the traditional invasive measurement using cardiac catheter, the BESR sequence may provide a simple and rapid method for non-invasive assessment blood oxygenation in vivo.

Yosuke Otake¹, Koji Hirata¹, Yoshihisa Soutome¹, and Yoshitaka Bito^1
1Hitachi, Ltd., Central Resaerch Laboratory, Kokubunji, Tokyo, Japan

A ¹⁹F two-element phased-array coil with a transmit ¹⁹F/¹H dual-tuned linear-birdcage coil for rats was developed. In-vivo ¹⁹F imaging of the anticancer drug 5-Fluorouracil and its metabolites in tumor-bearing rats was demonstrated by using the developed coils. Time courses of 5-FU and its active-metabolite (Fnuc) distribution images were obtained in the region of the tumor by using fast spin echo with frequency-selective pulses. This study indicates that the developed ¹⁹F two-element phased-array coil will make small-animal studies possible in drug research.