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Use of Ferrum in MRI of lung parenchyma and pulmonary embolism
S Vinitski1, M L Thakur, P M Consigny
1Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA 19107-5244.
Abstract:
MRI of lung parenchyma and pulmonary embolism (PE) remains challenging. "Ferrum," a ferric hydroxide sucrose complex used clinically for iron deficiency anemia for more than 40 years, was investigated as a negative MRI contrast agent in five rabbits bearing experimental PE as well as in five normal volunteers. Clots were prepared by spontaneous coagulation of 0.1 ml In-111 labeled autologous red blood cells and introduced through the jugular vein. Scintigraphic imaging permitted anatomical localization of PE in vivo and thereby served as a control for MR imaging. MRI was performed on a 1.5 T GE Signa scanner before and after induction of PE, and before and after the injection of Ferrum. T1-weighted images were obtained continuously for up to 90 min using varying doses of Ferrum. In five normal human volunteers, a single dose of 100 mg each was administered. T1- and T2-weighted spin-echo and gradient-echo images of lung parenchyma were repeatedly obtained before and after agent administration. In rabbit, Ferrum remained in circulation for several hours where it shortened both T1 and T2 of blood, improving the contrast between PE and lung parenchyma (i.e., intravascular compartment). A dose of 3 mg/kg was enough to increase the contrast-to-noise ratio (CNR) between PE and lung parenchyma by almost three fold, substantially improving lesion detectability. CNR increased up to five-fold when the dose was increased up to 20 mg/kg at which point CNR reached a plateau. In humans, T2-weighted spin-echo sequence appeared to be most sensitive to changes in signal-to-noise ratio (SNR) of normal lung parenchyma. Within 60 min after injection of 100 mg of iron, SNR dropped by 34% (p < .025). However, 24 hr later, SNR returned to almost normal. Ferrum increased the contrast between PE and lung parenchyma in the rabbit and decreased the parenchymal SNR in humans in nontoxic doses. These results suggest that Ferrum is worthy of further investigation of PE imaging in humans.
Insights
Ferrum, an iron deficiency anemia treatment, shows promise as a negative MRI contrast agent for pulmonary embolism (PE) detection. It improved contrast between PE and lung tissue in rabbits, warranting further human trials.
Area of Science:
- Radiology
- Medical Imaging
- Pharmacology
Background:
- Magnetic Resonance Imaging (MRI) of lung parenchyma and pulmonary embolism (PE) presents diagnostic challenges.
- Existing contrast agents have limitations for visualizing PE within lung tissue.
Purpose of the Study:
- To investigate Ferrum, an iron sucrose complex, as a negative MRI contrast agent for enhanced PE detection.
- To evaluate the safety and efficacy of Ferrum in animal models and human volunteers.
Main Methods:
- Experimental PE was induced in rabbits; MRI was performed before and after Ferrum administration at varying doses.
- Normal human volunteers received a single dose of Ferrum, with serial MRI scans of lung parenchyma.
- T1- and T2-weighted spin-echo and gradient-echo sequences were utilized.
Main Results:
- In rabbits, Ferrum shortened T1 and T2 relaxation times, significantly improving contrast between PE and lung parenchyma, with optimal CNR at 20 mg/kg.
- In humans, Ferrum reduced lung parenchyma signal-to-noise ratio (SNR) by 34% within 60 minutes on T2-weighted images, with recovery within 24 hours.
- The agent was administered in non-toxic doses.
Conclusions:
- Ferrum effectively enhances contrast for PE detection in rabbits by altering blood T1 and T2 relaxation times.
- Ferrum demonstrates a transient, non-toxic effect on human lung parenchyma SNR, suggesting its potential utility.
- Further investigation of Ferrum for human PE imaging is warranted.