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In vitro evaluation of MR hypointensity in Aspergillus colonies
D W Fellows1, V D King, T Conturo
1Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins Medical Institutions, Baltimore, MD 21205.
Purpose:
To demonstrate that paramagnetic elements in fungal colonies can cause hypointensity in MR images.
Methods:
Aspergillus fumigatus grown in vitro was imaged with CT and MR at the time of initial inoculation and 5 days later. CT and MR images, T2 values, scanning electron microscopy, energy-dispersive analysis, and furnace atomic absorption spectrometry were performed.
Results:
After 5 days of growth, MR images of A fumigatus revealed curvilinear hypointensities on T2-weighted images corresponding to the fungal growth. Gradient-echo images revealed two distinct components of hypointensity with different calculated T2 values. Phase-angle-difference images revealed a phase shift characteristic of magnetic-susceptibility paramagnetic effects, which corresponded to the hypointense regions on gradient-echo images. Energy-dispersive analysis and furnace atomic absorption spectrometry confirmed the presence of paramagnetic elements.
Conclusion:
It was shown that in vitro A fumigatus concentrates metal elements contained within the nutrient broth. These focal collections of calculated T2 values are caused at least partly by magnetic susceptibility effects.