Partial Acquisition of Spectral Projections Accelerates Four-dimensional Spectral-spatial EPR Imaging for Mouse Tumor Models: A Feasibility Study

• Published in: Molecular imaging and biology Vol. 26; no. 3; pp. 459 - 472
• Main Authors: Oba, Misa, Taguchi, Mai, Kudo, Yohei, Yamashita, Koya, Yasui, Hironobu, Matsumoto, Shingo, Kirilyuk, Igor A., Inanami, Osamu, Hirata, Hiroshi
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2024; Springer Nature B.V
• Subjects: Adenocarcinoma; Animal models; Animals; Cell Line, Tumor; Disease Models, Animal; Electron paramagnetic resonance; Electron spin resonance; Electron Spin Resonance Spectroscopy - methods; Feasibility Studies; Humans; Image acquisition; Image degradation; Image processing; Image Processing, Computer-Assisted - methods; Image quality; Image reconstruction; Imaging; Magnetic fields; Mapping; Medicine; Medicine & Public Health; Mice; Pancreas; Pancreatic cancer; Pancreatic Neoplasms - diagnostic imaging; Pancreatic Neoplasms - pathology; Radiology; Research Article; Tumors; Xenografts; Xenotransplantation; EPR imaging; 4D Spectral-spatial imaging; Linewidth mapping; Accelerated image acquisition; EPR; Mouse xenograft model
• ISSN: 1536-1632; 1860-2002; 1860-2002
• DOI: 10.1007/s11307-024-01924-y

Purpose Our study aimed to accelerate the acquisition of four-dimensional (4D) spectral-spatial electron paramagnetic resonance (EPR) imaging for mouse tumor models. This advancement in EPR imaging should reduce the acquisition time of spectroscopic mapping while reducing quality degradation for mouse tumor models. Procedures EPR spectra under magnetic field gradients, called spectral projections, were partially measured. Additional spectral projections were later computationally synthesized from the measured spectral projections. Four-dimensional spectral-spatial images were reconstructed from the post-processed spectral projections using the algebraic reconstruction technique (ART) and assessed in terms of their image qualities. We applied this approach to a sample solution and a mouse Hs766T xenograft model of human-derived pancreatic ductal adenocarcinoma cells to demonstrate the feasibility of our concept. The nitroxyl radical imaging agent 2 H, 15 N-DCP was exogenously infused into the mouse xenograft model. Results The computation code of 4D spectral-spatial imaging was tested with numerically generated spectral projections. In the linewidth mapping of the sample solution, we achieved a relative standard uncertainty (standard deviation/| mean |) of 0.76 μT/45.38 μT = 0.017 on the peak-to-peak first-derivative EPR linewidth. The qualities of the linewidth maps and the effect of computational synthesis of spectral projections were examined. Finally, we obtained the three-dimensional linewidth map of 2 H, 15 N-DCP in a Hs766T tumor-bearing leg in vivo . Conclusion We achieved a 46.7% reduction in the acquisition time of 4D spectral-spatial EPR imaging without significantly degrading the image quality. A combination of ART and partial acquisition in three-dimensional raster magnetic field gradient settings in orthogonal coordinates is a novel approach. Our approach to 4D spectral-spatial EPR imaging can be applied to any subject, especially for samples with less variation in one direction.