title: A comparison of iopromide and iopamidol, two acidoCEST MRI contrast media that measure tumor extracellular pH.
abstract: Acidosis within tumor and kidney tissues has previously been quantitatively measured using a molecular imaging technique known as acidoCEST MRI. The previous studies used iopromide and iopamidol, two iodinated contrast agents that are approved for clinical CT diagnoses and have been repurposed for acidoCEST MRI studies. We aimed to compare the performance of the two agents for measuring pH by optimizing image acquisition conditions, correlating pH with a ratio of CEST effects from an agent, and evaluating the effects of concentration, endogenous T1 relaxation time and temperature on the pH-CEST ratio correlation for each agent. These results showed that the two agents had similar performance characteristics, although iopromide produced a pH measurement with a higher dynamic range while iopamidol produced a more precise pH measurement. We then compared the performance of the two agents to measure in vivo extracellular pH (pHe) within xenograft tumor models of Raji lymphoma and MCF-7 breast cancer. Our results showed that the pHe values measured with each agent were not significantly different. Also, iopromide consistently measured a greater region of the tumor relative to iopamidol in both tumor models. Therefore, an iodinated contrast agent for acidoCEST MRI should be selected based on the measurement properties needed for a specific biomedical study and the pharmacokinetic properties of a specific tumor model.
authors.affiliation: Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA.
authors.forename: Brianna F
authors.initials: BF
authors.lastname: Moon
authors.affiliation: Biomedical Engineering Graduate Interdisciplinary Program, University of Arizona, Tucson, AZ, USA.
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Jones
authors.affiliation: Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA.
authors.forename: Liu Qi
authors.initials: LQ
authors.lastname: Chen
authors.affiliation: Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA.
authors.forename: Peilu
authors.initials: P
authors.lastname: Liu
authors.affiliation: Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Randtke
authors.affiliation: Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Howison
authors.affiliation: Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA.|Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA.|Department of Medical Imaging, University of Arizona, Tucson, AZ, USA.|University of Arizona Cancer Center, University of Arizona, Tucson, AZ, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Pagel
mesh_terms: D000138:Acidosis / Q000473:pathology; D000818:Animals; D002138:Calibration; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000737:chemistry*; D019008:Drug Resistance, Neoplasm / Q000502:physiology; D045604:Extracellular Fluid / Q000737:chemistry; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007472:Iohexol / Q000031:analogs & derivatives* / Q000737:chemistry; D007479:Iopamidol / Q000737:chemistry*; D007668:Kidney / Q000473:pathology; D061986:MCF-7 Cells; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D016513:Mice, SCID; D057054:Molecular Imaging; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000473:pathology; D014183:Transplantation, Heterologous; D059016:Tumor Microenvironment / Q000502:physiology*
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide; D007479:Iopamidol
keywords: CEST MRI; iopamidol; iopromide; tumor acidosis