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Counting small hypointense spots confounds the quantification of functional islet mass based on islet MRI
1Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
Abstract:
Iron-containing fragmented islets or free iron released from dying cells could confound the interpretation of MRI of iron nanoparticle-labeled islets. Exclusion of small hypointense spots could be a useful strategy to avoid such artifact. We investigated whether this strategy could improve the estimation of functioning islet mass after islet transplantation. Using a rat syngeneic intraportal islet transplantation model, we quantitatively assessed the relationships between total area, number of hypointense spots on MRI that belong to each size quartile and glycemic control of the recipients. The total area of hypointense spots on MRI was greater in the recipients that achieved diabetes reversal (p = 0.002), whereas the total number of hypointense spots was not different (p = 0.757). Exclusion of small hypointense spots improved the association between the number of hypointense spots and the blood glucose level of the recipients (p < 0.001). Ex-vivo imaging and histologic study confirmed that some small hypointense spots represent the phagocytosed free iron. Exclusion of small hypointense spots improved the quantification of the functional islet mass based on islet MRI. This would be a useful principle in the development of an algorithm to estimate functioning islet mass based on islet MRI.
Insights
Excluding small spots on MRI scans improves the assessment of transplanted islet function. This method helps accurately quantify functioning islet mass after islet transplantation for better diabetes management.
Area of Science:
- Biomedical Imaging
- Transplantation Biology
- Metabolic Disease Research
Background:
- Magnetic Resonance Imaging (MRI) using iron nanoparticles is used to monitor islet grafts.
- Artifacts from free iron or fragmented islets can hinder accurate interpretation of MRI scans.
- Improving the quantification of functioning islet mass is crucial for assessing transplant success.
Purpose of the Study:
- To evaluate if excluding small hypointense spots on MRI improves the estimation of functioning islet mass post-transplantation.
- To investigate the relationship between MRI findings and glycemic control in islet transplant recipients.
Main Methods:
- Utilized a rat syngeneic intraportal islet transplantation model.
- Quantitatively assessed MRI hypointense spots (total area, number per quartile) and correlated with recipient glycemic control.
- Performed ex-vivo imaging and histology to identify the source of small hypointense spots.
Main Results:
- Total area of hypointense spots was significantly larger in recipients with diabetes reversal (p = 0.002).
- Excluding small hypointense spots significantly improved the correlation between the number of spots and blood glucose levels (p < 0.001).
- Histology confirmed that small hypointense spots can represent phagocytosed free iron, an artifact.
Conclusions:
- Excluding small hypointense spots enhances the accuracy of quantifying functional islet mass using MRI.
- This strategy offers a valuable principle for developing algorithms to estimate islet graft function.
- Improved MRI interpretation can lead to better monitoring and management of islet transplantation outcomes.
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