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Whole-Brain Intracellular pH Mapping of Gliomas Using High-Resolution 31P MR Spectroscopic Imaging at 7.0 T
Daniel Paech1, Nina Weckesser1, Vanessa L Franke1
1From the Divisions of Radiology (D.P., N.W., K.D.H., H.P.S.) and Medical Physics in Radiology (V.L.F., J.B., S.G., P.B., M.E.L., A.K.), German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany; Faculties of Medicine (N.W., M.E.L.) and Physics and Astronomy (V.L.F., P.B., M.E.L.), University of Heidelberg, Heidelberg, Germany; and Departments of Neurology (A.W., W.W.), Neurosurgery (M.S., A.U.), and Neuroradiology (M.B.), Heidelberg University Hospital, Heidelberg, Germany.
High-resolution 7.0 Tesla 31P spectroscopic MRI quantified intracellular pH (pHi) in gliomas. Increased pHi correlated with higher Ki-67 proliferation index, suggesting potential for diagnosis and monitoring.
Area of Science:
- Neuroimaging
- Oncology
- Biophysics
Background:
- Malignant tumors often display reversed pH gradients (acidic extracellular, alkaline intracellular) compared to normal tissues.
- Intracellular pH (pHi) is a potential biomarker for tumor malignancy and proliferation.
Purpose of the Study:
- To prospectively quantify intracellular pH (pHi) in gliomas using high-resolution 7.0 Tesla 31P spectroscopic MRI.
- To correlate measured pHi values with histopathologic findings, specifically the Ki-67 proliferation index.
Main Methods:
- Twelve newly diagnosed glioma patients underwent 7.0 T 31P/1H spectroscopic MRI using a 3D chemical shift imaging sequence.
- 3D volumetric segmentations defined whole-tumor volumes (WTVs), tumor subcompartments (necrosis, enhancement, NCE T2), and normal-appearing white matter (NAWM).
- Spearman correlation assessed the association between pHi and the Ki-67 proliferation index.
Main Results:
- Mean pHi was significantly higher in the whole-tumor volume (WTV) compared to normal-appearing white matter (NAWM) (7.057 vs. 7.006, P < .001).
- In high-grade gliomas, all tumor subcompartments showed increased pHi compared to NAWM (P < .01).
- WTV pHi positively correlated with the Ki-67 proliferation index (R2 = 0.74, r = 0.78, P = .001).
Conclusions:
- 7.0 T 31P spectroscopic MRI enables high-resolution quantification of intracellular pH (pHi) in gliomas.
- Elevated pHi in gliomas is associated with tumor grade and the Ki-67 proliferation index.
- This technique shows promise as an imaging biomarker for glioma diagnosis and treatment monitoring.
