Quantitative evaluation of the relaxivity effects of iodine on GD‐DTPA enhanced MR arthrography

Abstract

Purpose:To quantify the effect of iodine on the gadolinium (Gd) contrast-enhanced signal in MR arthrography. Materials and Methods:Saline solutions of Gd contrast agent (0 -1 mmol/liter) were mixed with iodinated contrast agent (0 -185 mmol/liter). The T1 and T2 relaxation constants of these solutions were measured at 1.5T. Different types of commonly used iodinated contrast agents as well as sodium iodide (NaI) solutions were also analyzed.Results: Iodine caused significant T2 shortening and some T1 shortening in Gd contrast solutions. Both contrast agents independently obeyed the standard relaxation relation, and their mixture obeyed a modified version of this relation. The side chains in various iodine molecules and their viscosities affected the relaxation properties differently. For various spinecho (SE) sequences, the signal from synovial fluid containing different concentrations of the two contrast agents was calculated. The T2-weighted signal appeared to be most affected by the increase in iodine concentrations. In the absence of Gd contrast, all SE sequences showed an initial increase in signal from iodine contrast. Conclusion:A generalized relation for the relaxivities of Gd contrast in the presence of iodine was established. The side chains of iodine contrast were found to alter the relaxivities of Gd contrast. Imaging with proton density (PD)-weighted SE with only iodine contrast agent was found to be feasible.

MRI Appearance of Intracerebral Iodinated Contrast Agents: Is It Possible to Distinguish Extravasated Contrast Agent from Hemorrhage?

“…Our results confirm that iodinated contrast agents in fact cause visually distinctive T1 and T2 shortening in phantom models (On-line Fig 2). 5,6 Nevertheless, our data and data from the literature also imply that this effect is negligible when contrast agents are diluted. 5 In accordance with the results from the phantom models, even pure iopamidol that was injected directly into the brain parenchyma in an ex vivo animal model did not cause visually distinctive signal changes on T1 SE, T2 TSE, and T2 * GRE imaging (Figure).…”

“…However, it has been shown in phantom models that T1 and T2 shortening caused by iodinated contrast agents may theoretically mimic the appearance of intracellular methemoglobin, which is present in early subacute intracerebral hematomas within 3-7 days after hemorrhage. 5,6 Because many MR imaging examinations are performed within this time period, the differentiation between hemorrhage and extravasated contrast agent may thus be complicated. Our results confirm that iodinated contrast agents in fact cause visually distinctive T1 and T2 shortening in phantom models (On-line Fig 2).…”

“…However, it has been shown in phantom models that at a field strength of 1.5T, side chains of iodinated contrast agents cause T1 and T2 shortening, which theoretically may mimic the imaging characteristics of intracellular methemoglobin present in early subacute intracerebral hemorrhage. 5,6 Furthermore, the influence of iodinated contrast agents on susceptibility and T2*WI sequences, which are commonly used in hemorrhage diagnosis, has not been investigated yet, to our knowledge. Hence, we examined the influence of 2 common iodinated contrast agents on magnetic susceptibility and T1, T2, and T2 * relaxation in a phantom model and an ex vivo animal model to elucidate whether iodinated contrast agents can be distinguished from blood on MR imaging.…”

The Role of Dual Energy CT in Evaluating Hemorrhagic Complications at Different Stages After Thrombectomy

“…Commonly, the issue can be resolved with a repeated CT examination within 1-3 days (12,15), which may postpone antithrombotic therapy or anticoagulation. Although iodine can affect several magnetic resonance sequences (16), hemosiderin-sensitive sequences can be used since it is unlikely that iodine could mimic hemorrhage on magnetic resonance imaging (17). By contrast, DECT is a simple and fast solution differentiating hemorrhage and contrast staining, avoiding the delayed time for a repeat examination and the limitations of magnetic resonance, such as contraindications and limited resource issues (7).…”

Fast MR arthrography using VIBE sequences to evaluate the rotator cuff

“…CT arthrography using multidetector arrays can provide precise answers to all pre-operative questions (location and extent of the tear, position of the retracted tendon, and muscle atrophy), but MR arthrography seems to be the method of choice for the pre-operative workup of suspected rotator cuff pathology [19]. On the other hand, the use of large quantities of iodine for MR arthrography is not advocated because the presence of iodine in gadolinium-enhanced synovial fluid may produce a pronounced signal reduction on MR imaging [8,20]. Currently in our department, we have decreased the amount of iodine injection to a few drops to verify needle tip position using fluoroscopy [21]; however, it cancels the option to switch to CT arthrography in patients that are unable to lie still in the MR unit.…”