Fungal sinusitis: diagnosis with CT and MR imaging.

TLDR

The hypointense T2‑weighted MR signal in fungal sinusitis is attributed to iron, manganese, and calcium deposits within the fungal concretion. In a cohort of 293 chronic sinusitis patients, 25 were pathologically confirmed fungal sinusitis, 19 met the CT criterion (12 % false‑positive/negative rates), and all 7 patients who underwent MR imaging displayed markedly hypointense T2‑weighted signals, indicating MR is more characteristic than CT, while elemental analysis revealed elevated iron and manganese in the fungal concretion.

Abstract

Of 293 patients who underwent computed tomography (CT), surgery, and pathologic examination for chronic sinusitis, 25 had a diagnosis of fungal sinusitis at pathologic examination. Of these, 22 had foci of increased attenuation at CT (in four patients the mean representative CT number [Hounsfied unit] was 122.2 HU [SD, 8.2 HU]), and three did not. Of the 22, 19 patients (76%) met the CT criterion of this study (there was a 12% false-positive and a 12% false-negative diagnostic rate). Six of the 19 patients and one additional patient underwent magnetic resonance (MR) imaging, and all demonstrated remarkably hypointense signal characteristics on T2-weighted images. The findings at MR imaging therefore appear more characteristic of fungal sinusitis than the findings at CT. Furnace atomic absorption spectrometry showed increased concentrations of iron and manganese in mycetoma compared with their concentrations in bacterially infected mucus. This finding and the presence of calcium in the fungal concretion may explain the hypointense T2-weighted signal on MR images.