T1 Relaxivities of Gadolinium-Based Magnetic Resonance Contrast Agents in Human Whole Blood at 1.5, 3, and 7 T

Abstract

OBJECTIVES Calculation of accurate T1 relaxivity (r1) values for gadolinium-based magnetic resonance contrast agents (GBCAs) is a complex process. As such, often referenced r1 values for the GBCAs at 1.5 T, 3 T, and 7 T are based on measurements obtained in media that are not clinically relevant, derived from only a small number of concentrations, or available for only a limited number of GBCAs. This study derives the r1 values of the 8 commercially available GBCAs in human whole blood at 1.5 T, 3 T, and 7 T. MATERIALS AND METHODS Eight GBCAs were serially diluted in human whole blood, at 7 concentrations from 0.0625 to 4 mM. A custom-built phantom held the dilutions in air-tight cylindrical tubes maintained at 37 ± 0.5°C by a heat-circulating system. Images were acquired using inversion recovery sequences with inversion times from 30 milliseconds to 10 seconds at 1.5 T and 3 T as well as 60 milliseconds to 5 seconds at 7 T. A custom MATLAB program was used to automate signal intensity measurements from the images acquired of the phantom. SigmaPlot was used to calculate T1 relaxation times and, finally, r1. RESULTS Measured r1 values in units of s[BULLET OPERATOR]mM at 1.5 T (3 T/7 T) were 3.9 ± 0.2 (3.4 ± 0.4/2.8 ± 0.4) for Gd-DOTA, 4.6 ± 0.2 (4.5 ± 0.3/4.2 ± 0.3) for Gd-DO3A-butrol, 4.3 ± 0.4 (3.8 ± 0.2/3.1 ± 0.4) for Gd-DTPA, 6.2 ± 0.5 (5.4 ± 0.3/4.7 ± 0.1) for Gd-BOPTA, 4.5 ± 0.1 (3.9 ± 0.2/3.7 ± 0.2) for Gd-DTPA-BMA, 4.4 ± 0.2 (4.2 ± 0.2/4.3 ± 0.2) for Gd-DTPA-BMEA, 7.2 ± 0.2 (5.5 ± 0.3/4.9 ± 0.1) for Gd-EOB-DTPA, and 4.4 ± 0.6 (3.5 ± 0.6/3.4 ± 0.1) for Gd-HP-DO3A. The agents can be stratified by relaxivity, with a significant additional dependency on field strength. CONCLUSIONS This report quantifies, for the first time, T1 relaxivity for all 8 gadolinium chelates in common clinical use worldwide, at current relevant field strengths, in human whole blood at physiological temperature (37°C). The measured r1 values differ to a small degree from previously published values, where such comparisons exist, with the current r1 measurements being that most relevant to clinical practice. The macrocyclic agents, with the exception of Gd-DO3A-butrol, have slightly lower r1 values when compared with the 2 much less stable linear agents, Gd-DTPA-BMA and Gd-DTPA-BMEA. The 2 agents with hepatobiliary excretion, Gd-EOB-DTPA and Gd-BOPTA, have, at 1.5 and 3 T, substantially higher r1 values than all other agents.

The Benefits of High Relaxivity for Brain Tumor Imaging: Results of a Multicenter Intraindividual Crossover Comparison of Gadobenate Dimeglumine with Gadoterate Meglumine (The BENEFIT Study)

“…(1.596 versus 1.541), respectively, for gadobutrol versus gadoterate, which reflect a difference in r1 relaxivity of ϳ18% based on values determined by Shen et al 5 In a comparison of gadobenate and gadobutrol, Siedl et al 4 reported differences in percentage lesion enhancement and LBR of 21.8%-24.7% and 21.4%-25.0%, respectively, which reflect a greater difference in r1 relaxivity of ϳ35%. In this study, we determined larger differences in percentage lesion enhancement and LBR of 27.6%-31.7% and 29.2%-38.1%, respectively, for equivalent doses of gadobenate and gadoterate, which reflect the still greater difference in r1 relaxivity of ϳ59%.…”

“…5 That differences in r1 relaxivity reflect differences in diagnostic efficacy is borne out by evidence from numerous large-scale intraindividual crossover studies. [1][2][3][4][8][9][10][11] These studies have shown that differences in SI enhancement and imaging performance reflect differences in r1 relaxivity and that the magnitude of the differences in SI enhancement a Comparisons based on the number of patients with both postdose T1SE images assessed and technically adequate: n ϭ 96 for reader 1, n ϭ 94 for reader 2, and n ϭ 95 for reader 3.…”

“…tion) can be ascribed to the higher r1 relaxivity of gadobenate in vivo, 5 which translates into greater signal-intensity (SI) enhancement on T1-weighted images. An early study in 23 patients suggested that 0.1-mmol/kg gadobenate may provide superior contrast enhancement compared with 0.1-mmol/kg gadoterate meglumine (Dotarem; Guerbet, Aulnay-sous-Bois, France), another gadolinium-based contrast agent (GBCA) with lower r1 relaxivity.…”

Clinical utility of gadobenate dimeglumine in contrast-enhanced MRI of the breast: a review

“…26 The results of all these intra-individual crossover studies [23][24][25][26] can be ascribed to the greater r1 relaxivity of gadobenate dimeglumine compared to gadopentetate dimeglumine (6.2 L/mmols -1 vs 4.2 L/mmols -1 at 1.5 T). 21 Since r1 relaxivity is the single most important para meter defining contrast efficacy in terms of signal intensity enhancement, similar superiority for gadobenate dimeglumine can be anticipated for intra-individual comparisons of this agent with other GBCAs that have r1 relaxivity values similar to that of gadopentetate dimeglumine.…”

“…19 The extent to which a GBCA shortens the relaxation times depends on the relaxivity of the agent. GBCAs have different structures and physicochemical properties but most have similar r1 relaxivity values of 3.9-4.6 L/mmols -1 at 1.5 T. 21 Of the GBCAs available for breast imaging gadobenate dimeglumine (MultiHance ® ; Bracco imaging, Milan, Italy) has a markedly higher r1 relaxivity in vivo of 6.2 L/mmols -1 at 1.5 T. Several studies have demonstrated an association between the use of contrast agents with higher r1 relaxivity and stronger contrast enhancement in comparison to contrast agents with lower r1 relaxivity. For most clinical applications, the stronger enhancement has been shown to be associated with a clinically relevant gain in diagnostic performance.…”