What Radiologist Should Know about MRI Translational Forces and Hazard: An Ex-Vivo Simulation of Retained Metallic
Ali Kanj1, Ibrahim Ghosn2, Assaad Mohanna3
1Radiology Department, Hammoud Hospital University Medical Center, Saida, Lebanon.
Background:
In a country immersed in endless rounds of wars, retained metallic foreign bodies remain a significant dilemma in the daily practice of every Lebanese radiologist. When a shrapnel's hazard is of concern, the decision between performing or refusing a justified MRI exam is not always straightforward. In this small trial, we aimed to better understand the shrapnel's MRI safety by mimicking our daily practice.
Methods:
Five shrapnel with an incremental increase in their long axis were put in an animal flesh and then introduced into a 3 T magnetic field. The behavior of each shrapnel was concretely assessed by performing before and after magnetic field exposure CT acquisitions.
Results:
Translation along the z-axis ranged from 0.9 mm to 2.8 mm. Torque angle ranged between 2.8 and 54 degrees with an average of 15.62 degrees.
Conclusions:
Shrapnel's movements in the magnetic field are not negligible during the acute phase of injury where there is no reinforcing fibroblastic reaction and invite us to reconsider the MRI safety of these metallic foreign bodies. Standard radiographs may be sufficient, but a targeted CT scan may be of better value for a confident decision for assessment of shrapnel position near viscera and major vessels.
Insights
Metallic foreign bodies from war pose an MRI safety dilemma. This study found shrapnel movement in MRI scans is significant, questioning their safety, especially in acute injury phases.
Area of Science:
- Medical Imaging
- Radiology
- Biomedical Engineering
Background:
- Retained metallic foreign bodies, often shrapnel, are a common challenge for radiologists in war-torn regions.
- Deciding on MRI safety for patients with shrapnel is complex due to potential risks.
- This study addresses the practical dilemma of MRI compatibility with shrapnel.
Purpose of the Study:
- To evaluate the magnetic field safety of retained shrapnel.
- To understand the behavior of shrapnel within a 3 Tesla (3T) MRI environment.
- To inform clinical decisions regarding MRI examinations in patients with metallic foreign bodies.
Main Methods:
- Five shrapnel of varying sizes were embedded in animal tissue.
- The tissue samples were exposed to a 3T magnetic field.
- Computed tomography (CT) scans were performed before and after exposure to assess shrapnel displacement and rotation.
Main Results:
- Shrapnel exhibited translation along the z-axis, ranging from 0.9 mm to 2.8 mm.
- Observed torque angles varied from 2.8 to 54 degrees, averaging 15.62 degrees.
- These movements indicate a non-negligible response to the magnetic field.
Conclusions:
- Shrapnel movement in MRI scans is significant, particularly in the acute injury phase before tissue encapsulation.
- The findings challenge the assumption of MRI safety for metallic foreign bodies.
- Targeted CT scans may be more valuable than standard radiographs for assessing shrapnel proximity to critical structures.
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