Practical data acquisition method for human brain tumor amide proton transfer (APT) imaging

TLDR

Amide proton transfer (APT) imaging is a CEST MRI technique that detects amide protons of endogenous proteins, and early studies showed promise for tumor delineation but were limited by B0 inhomogeneity and low signal‑to‑noise ratio. The authors aim to provide a practical six‑offset APT acquisition scheme, combined with a separately acquired CEST spectrum, to generate B0‑corrected human brain APT images with adequate SNR within a clinically relevant timeframe. The method uses a six‑offset APT data acquisition protocol and an additional CEST spectrum to correct B0 inhomogeneity and produce high‑quality images in a short scan time. In nine 3T brain‑tumor patients, APT intensities were significantly higher in high‑grade tumor cores compared to contralateral white matter, indistinguishable in low‑grade tumors, and extended beyond the core into peripheral zones, suggesting improved delineation of heterogeneous cancer areas. Published in Magn Reson Med 60:842–849 (2008); © 2008 Wiley‑Liss, Inc.

Abstract

Abstract Amide proton transfer (APT) imaging is a type of chemical exchange–dependent saturation transfer (CEST) magnetic resonance imaging (MRI) in which amide protons of endogenous mobile proteins and peptides in tissue are detected. Initial studies have shown promising results for distinguishing tumor from surrounding brain in patients, but these data were hampered by magnetic field inhomogeneity and a low signal‐to‐noise ratio (SNR). Here a practical six‐offset APT data acquisition scheme is presented that, together with a separately acquired CEST spectrum, can provide B 0 ‐inhomogeneity corrected human brain APT images of sufficient SNR within a clinically relevant time frame. Data from nine brain tumor patients at 3T shows that APT intensities were significantly higher in the tumor core, as assigned by gadolinium‐enhancement, than in contralateral normal‐appearing white matter (CNAWM) in patients with high‐grade tumors. Conversely, APT intensities in tumor were indistinguishable from CNAWM in patients with low‐grade tumors. In high‐grade tumors, regions of increased APT extended outside of the core into peripheral zones, indicating the potential of this technique for more accurate delineation of the heterogeneous areas of brain cancers. Magn Reson Med 60:842–849, 2008. © 2008 Wiley‐Liss, Inc.