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In vivo imaging of extracellular pH using 1H MRSI
R van Sluis1, Z M Bhujwalla, N Raghunand
1Department of Biochemistry, The University of Arizona, Tucson, USA.
Abstract:
Tumor pH is physiologically important since it influences a number of processes relevant to tumorigenesis and therapy. Hence, knowledge of localized pH within tumors would contribute to understanding these processes. The destructiveness, poor spatial resolution, and poor signal-to-noise ratio (SNR) of current technologies (e.g., microelectrodes, 31P magnetic resonance spectroscopy) have limited such studies. An extrinsic chemical extracellular pH (pHe) probe is described that is used in combination with 1H magnetic resonance spectroscopic imaging to yield pHe maps with a spatial resolution of 1 x 1 x 4 mm3. The principle of the technique is demonstrated on a phantom. Further data are shown to demonstrate its application in vivo, and results agree with previously reported pH values. The accuracy of the reported pH measurements is <0.1 pH units, as derived from a detailed analysis of the errors associated with the technique, the description of which is included.
Insights
This study introduces a novel chemical probe for mapping tumor extracellular pH (pHe) using 1H magnetic resonance spectroscopic imaging, offering improved spatial resolution for cancer research.
Area of Science:
- Biomedical Imaging
- Oncology
- Biochemistry
Background:
- Tumor pH significantly impacts cancer development and treatment efficacy.
- Current methods for measuring tumor pH have limitations in accuracy and spatial resolution.
Purpose of the Study:
- To develop and validate a new technique for mapping extracellular pH (pHe) in tumors.
- To overcome the limitations of existing technologies for localized pH measurement.
Main Methods:
- Utilized an extrinsic chemical extracellular pH (pHe) probe.
- Combined the probe with 1H magnetic resonance spectroscopic imaging.
- Achieved a spatial resolution of 1 x 1 x 4 mm³ for pHe mapping.
Main Results:
- Demonstrated the technique's principle on a phantom.
- Successfully applied the method in vivo, yielding results consistent with prior studies.
- Reported pH measurements with an accuracy of less than 0.1 pH units.
Conclusions:
- The developed technique provides accurate and high-resolution tumor extracellular pH mapping.
- This advancement aids in understanding tumor biology and therapeutic responses.
- Offers a superior alternative to existing methods for in vivo pH assessment.