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A strongly T2*-weighted, three-dimensional (3D) PSIF (time-reversed FISP [fast imaging with steady-state precession]) gradient-echo magnetic resonance (MR) sequence, with postprocessing of the 3D data set with a maximum-intensity projection (MIP) algorithm, produced x-ray myelography-equivalent images. The method was tested in 10 healthy volunteers to optimize sequence parameters and was evaluated in 30 patients with proven lumbar disk disease. MIP myelograms, unlike two-dimensional MR images, could not show the pathologic disks themselves but clearly demonstrated the effect on the thecal sac, giving a clear overall view of its geometry and dimensions, especially when displayed in a cine loop. All 28 medial and mediolateral disk herniations could be visualized, whereas only three of eight intraforminal disk herniations were seen on MR myelograms.

The purpose of this study was to investigate by CT the origin of radiodense maxillary sinus concretions and whether CT densitometry is effective in the prediction of maxillary sinus aspergillosis and in the differentiation of the origin of these concretions. In a prospective study in 21 patients with radiodense maxillary sinus concretions detected by radiography, a preoperative CT study of the paranasal sinuses and the concretions was undertaken. Additional scans of the upper alveolar ridge were also performed. Radiological findings were compared with clinical symptoms and with CT findings, especially CT densitometry of the sinus concretions and dental root-filling material. All patients underwent a functional Caldwell-Luc operation; histological and microbiological examinations were performed. Fifteen of the 21 patients (71.4%) with radiodense concretions had a histological and microbiological diagnosis of sinus aspergillosis. The sinus concretions had CT densities higher than 2000 HU (Hounsfield units) in 15 patients and lower than 2000 HU in 6. fourteen of 15 patients (93.3%) with concretions having CT densities higher than 2000 HU had a postoperative diagnosis of maxillary sinus aspergillosis. The mean CT density of the sinus concretions in patients with maxillary sinus aspergillosis was 2868 HU (range 1870-3070 HU), and in patients without aspergillosis was 778 HU (range 228-2644 HU). The mean CT density of the dental root-filling material was 2866 HU (range 2156-3070 HU). Paranasal sinus CT with CT densitometry of a sinus concretion has a higher accuracy than standard radiography and clinical findings in the prediction of maxillary sinus aspergillosis (93.3% vs 71.4%). CT densitometry helps to confirm the dental origin of maxillary sinus concretions and to explain a possible dental pathogenesis of maxillary sinus aspergillosis.

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