Iopamidol as a responsive MRI‐chemical exchange saturation transfer contrast agent for pH mapping of kidneys: In vivo studies in mice at 7 T

Abstract

.) is a clinically approved X-Ray contrast agent used in the last 30 years for a wide variety of diagnostic applications with a very good clinical acceptance. Iopamidol contains two types of amide functionalities that can be exploited for the generation of chemical exchange saturation transfer effect. The exchange rate of the two amide proton pools is markedly pH-dependent. Thus, a ratiometric method for pH assessment has been set-up based on the comparison of the saturation transfer effects induced by selective irradiation of the two resonances. This ratiometric approach allows to rule out the concentration effect of the contrast agent and provides accurate pH measurements in the 5.5-7.4 range. Upon injection of Iopamidol into healthy mice, it has been possible to acquire pH maps of kidney regions. Furthermore, it has been also shown that the proposed method is able to report about pH-changes induced in control mice fed with acidified or basified water for a period of a week before image acquisition. Magn Reson Med 65:202-211,

Myelography Iodinated Contrast Media. I. Unraveling the Atropisomerism Properties in Solution

“…In fact, cis secondary amides should present intense signals at around 1440−1450 cm −1 , arising from basically uncoupled N−H deformations, while no Amide II modes above 1500 cm −1 are expected for these forms. 15,16 It is interesting to note that the presence of two distinct bands assigned to the nonequivalent amide groups (namely, the anilido moiety and the two equivalent amide groups in positions 3 and 5) is in agreement with the NMR study of Longo et al, 19 who reported a different rate of proton exchange for the two types of N−H groups.…”

In Vitro and In Vivo Assessment of Nonionic Iodinated Radiographic Molecules as Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Tumor Perfusion Agents

“…[8][9][10][11][12][13] Notably, iodinated agents such as iopamidol and iopromide, containing 2 nonequivalent groups of amide protons, allow the setup of a ratiometric procedure for in vivo pH mapping in different tissues and pathological models. [14][15][16][17][18] Recently, a radio frequency (RF) power-based ratiometric approach has been proposed for agents containing a single exchangeable proton pool for measuring in vivo tumor extracellular pH with the same accuracy as with iopamidol. 19 It is important to note that pH imaging with iodinated agents has been successfully demonstrated in a human volunteer with a 3 T MR scanner.…”

CHAPTER 6. Recent Developments of Contrast Agents, CEST and Low Fields

“…39 Iopamidol (Isovue s -Bracco Imaging, Italy) is characterized by the presence of two types of functionalities that may be exploited for the generation of CEST effect (Figure 6.4). 40 The exchange rate of the two amide mobile proton pools is markedly pH-dependent. Thus, a ratiometric method for pH assessment has been set up based on the comparison of the saturation transfer effects induced by selective Recent Developments of Contrast Agents, CEST and Low Fields irradiation of the two resonances.…”