title: Iodine potassium iodide improves the contrast-to-noise ratio of micro-computed tomography images of the human middle ear.
abstract: High-resolution imaging of middle-ear geometry is necessary for finite-element modeling. Although micro-computed tomography (microCT) is widely used because of its ability to image bony structures of the middle ear, it is difficult to visualize soft tissues - including the tympanic membrane and the suspensory ligaments/tendons - because of lack of contrast. The objective of this research is to quantitatively evaluate the efficacy of iodine potassium iodide (IKI) solution as a contrast agent. Six human temporal bones were used in this experiment, which were obtained in right-left pairs, from three cadaveric heads. All bones were fixed using formaldehyde. Three bones (one from each pair) were stained in IKI solution for 2 days, whereas the other three were not stained. Samples were scanned using a microCT system at a resolution of 20 μm. Eight soft tissues in the middle ear were segmented: anterior mallear ligament, incudomallear joint, lateral mallear ligament, posterior incudal ligament, stapedial annular ligament, stapedius muscle, tympanic membrane and tensor tympani muscle. Contrast-to-noise ratios (CNRs) of each soft tissue were calculated for each temporal bone. Combined CNRs of the soft tissues in unstained samples were 6.1 ± 3.0, whereas they were 8.1 ± 2.7 in stained samples. Results from Welch's t-test indicate significant difference between the two groups at a 95% confidence interval. Results for paired t-tests for each of the individual soft tissues also indicated significant improvement of contrast in all tissues after staining. Relatively large soft tissues in the middle ear such as the tympanic membrane and the tensor tympani muscle were impacted by staining more than smaller tissues such as the stapedial annular ligament. The increase in contrast with IKI solution confirms its potential application in automatic segmentation of the middle-ear soft tissues.
authors.affiliation: Biomedical Engineering Graduate Program, Western University, London, Ontario, Canada.
authors.forename: S A
authors.initials: SA
authors.lastname: Rohani
authors.affiliation: Department of Medical Biophysics, Western University, London, Ontario, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Ghomashchi
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Umoh
authors.affiliation: Biomedical Engineering Graduate Program, Western University, London, Ontario, Canada.|Department of Medical Biophysics, Western University, London, Ontario, Canada.|Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada.
authors.forename: D W
authors.initials: DW
authors.lastname: Holdsworth
authors.affiliation: Department of Otolaryngology - Head & Neck Surgery, Western University, London, Ontario, Canada.
authors.forename: S K
authors.initials: SK
authors.lastname: Agrawal
authors.affiliation: Biomedical Engineering Graduate Program, Western University, London, Ontario, Canada.|Department of Medical Biophysics, Western University, London, Ontario, Canada.|Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada.|Department of Otolaryngology - Head & Neck Surgery, Western University, London, Ontario, Canada.|Department of Electrical & Computer Engineering, Western University, London, Ontario, Canada.
authors.forename: H M
authors.initials: HM
authors.lastname: Ladak
mesh_terms: D000328:Adult; D003287:Contrast Media; D004432:Ear, Middle / Q000000981:diagnostic imaging*; D006801:Humans; D017613:Iodine Compounds; D011856:Radiographic Image Enhancement; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D003287:Contrast Media; D017613:Iodine Compounds; C439385:iodine potassium iodide
keywords: Contrast; iodine potassium iodide; micro-computed tomography; middle ear