Antti Aarnisalo

Limited Cone-Beam Computed Tomography Imaging of the Middle Ear: A Comparison with Multislice Helical Computed Tomography

Purpose: To determine the applicability of cone-beam computed tomography (CBCT) in otological imaging, and to compare its accuracy with the routinely used multislice helical CT (MSCT) for imaging of the middle- and inner-ear areas. Material and Methods: Thirteen unoperated human cadaver temporal bones were imaged with CBCT and MSCT. Sixteen landmarks of the middle and adjacent inner ear were evaluated and compared for their conspicuity according to a modified Likert scale. Total scores and scores for subgroups including landmarks of specific clinical interest were also compared. Results: No significant differences were found between the imaging techniques or subgroups when scores of individual structures were compared. While the middle ear itself was visible in all cases with CBCT, parts of the inner ear were “cut off” in four cases due to the limited field of view. For the same reason, the evaluation of the whole mastoid was not possible with CBCT. The cochlear and vestibular aqueducts were not visualized in either CT techniques. The contrast-to-noise ratio was more than 50% lower in CBCT than in MSCT, but still adequate for diagnostic task. Conclusion: CBCT proved to be at least as accurate as routinely used MSCT in revealing the clinically and surgically important middle-ear structures. The results show that high-quality imaging of the middle ear is possible with the current CBCT device.

MR Imaging Features of Acute Mastoiditis and Their Clinical Relevance

BACKGROUND AND PURPOSE: MR imaging is often used for detecting intracranial complications of acute mastoiditis, whereas the intratemporal appearance of mastoiditis has been overlooked. The aim of this study was to assess the imaging features caused by acute mastoiditis in MR imaging and their clinical relevance. MATERIALS AND METHODS: Medical records and MR imaging findings of 31 patients with acute mastoiditis (21 adults, 10 children) were analyzed retrospectively. The degree of opacification in the temporal bone, signal and enhancement characteristics, bone destruction, and the presence of complications were correlated with clinical history and outcome data, with pediatric and adult patients compared. RESULTS: Most patients had ≥50% of the tympanic cavity and 100% of the mastoid antrum and air cells opacified. Compared with CSF, they also showed intramastoid signal changes in T1 spin-echo, T2 TSE, CISS, and DWI sequences; and intramastoid, outer periosteal, and perimastoid dural enhancement. The most common complications in MR imaging were intratemporal abscess (23%), subperiosteal abscess (19%), and labyrinth involvement (16%). Children had a significantly higher prevalence of total opacification of the tympanic cavity (80% versus 19%) and mastoid air cells (90% versus 21%), intense intramastoid enhancement (90% versus 33%), outer cortical bone destruction (70% versus 10%), subperiosteal abscess (50% versus 5%), and perimastoid meningeal enhancement (80% versus 33%). CONCLUSIONS: Acute mastoiditis causes several intra- and extratemporal changes on MR imaging. Total opacification of the tympanic cavity and the mastoid, intense intramastoid enhancement, perimastoid dural enhancement, bone erosion, and extracranial complications are more frequent in children.

HOX-GFP and WOX-GFP lentivirus vectors for inner ear gene transfer.

Conclusion. GFP transgene was expressed in the lining cells of the perilymphatic space. Lentivirus vectors are safe and cause only minimal inflammatory reaction. Transgene products can be delivered into the perilymph by utilizing lentivirus vectors. Objectives. To analyze the efficiency and safety of lentiviral vectors HOX-GFP and WOX-GFP in intracochlear gene transfer. Materials and methods. Lentivirus vectors were tested for their transduction efficiency in vivo in CD-1 mice. Half of the animals were pretreated with kanamycin. Lentivirus vector or saline (1 µl) was injected into the inner ear. All the animals were sacrificed 14 days after the surgery and the cochleae and selected organs were analyzed immunohistochemically. Results. HOX-GFP and WOX-GFP expression was restricted to the lining cells of the scala tympani and scala vestibuli. No GFP expression was seen in the organ of Corti or the spiral ganglion. Aminoglycoside treatment had no effect on the expression of these vectors. The distant spread of lentivirus vectors was minimal; only the liver of one animal showed some GFP expression. Inflammatory reaction caused by these vectors was mild. Few inflammatory cells were found in the perilymphatic space of the cochlea and in the vestibular organ.

Imaging Optimization of Temporal Bones With Cochlear Implant Using a High-resolution Cone Beam CT and the Corresponding Effective Dose.

Objective: To evaluate the impact of tube voltage, tube current, pulse number, and magnification factor on the image quality of a novel experimental set-up and the corresponding radiation. Materials and Methods: Six human temporal bones with cochlear implant were imaged using various tube voltages, tube currents, pulse numbers, and magnification. The effect of radiation was evaluated using a metaloxide semiconductor field-effect transistor (MOSFET) dosimeter device on an anthropomorphic RANDO RAN102 male head phantom. A copper and aluminum combination filter was used for hardware filtration. Results: Overall, 900 frames, 11 mA, and 88 kV provided the best image quality. In temporal bones imaged with the optimized parameters, the cochlea, osseous spiral lamina, modiolus, stapes, round window niche, and oval window landmarks were demonstrated with anatomic structures still fully assessable in all parts and acceptable image quality. The most dominant contributor to the effective dose was bone marrow (36%-37 %) followed by brain (34%-36%), remainder tissues (12%), extra-thoracic airways (7%), and oral mucosa (5%). Conclusions: By increasing the number of frames, the image quality of the inner ear details obtained using the novel cone-beam computed tomography improved.

Comparison of bacterial adherence to polylactides, silicone, and titanium

Conclusions: Less bacterial adherence occurred on uncoated polylactide and silicone than on uncoated titanium surfaces. Albumin coating was an effective method to inhibit bacterial adherence to all these surfaces. As regards bacterial adherence, polylactides are at least as safe implant materials as silicone and titanium. Objectives: We compared adherence of Staphylococcus aureus and Pseudomonas aeruginosa to four implant materials and studied the inhibitory effect of albumin on adherence. The aims were to discover any differences between materials and to study the effectiveness of albumin coating. Materials and methods: Eight plates of polylactide A and B, silicone, and titanium were exposed to S. aureus and P. aeruginosa. Four of these plates were uncoated and four were coated with albumin. A total of 64 plates were included in the study. The bacteria were stained with acridine orange, and 10 photomicrographs of each plate allowed quantification of the surface area covered with bacteria. Results: The most adherence occurred on titanium without coating. Albumin coating of the surface significantly reduced bacterial adherence to each material. Differences between materials with albumin coating were relatively small. Of the bacteria, P. aeruginosa had the greater capacity to adhere to a surface.

Imaging cochlear implantation with round window insertion in human temporal bones and cochlear morphological variation using high-resolution cone beam CT.

Abstract Conclusions: The present experimental set-up of high spatial resolution cone-beam computed tomography (CBCT) showed advantages of demonstrating the critical landmarks of the cochlea in identifying the position of intracochlear electrode contacts and has the potential for clinical application in cochlear implant (CI) surgery. Objective: To evaluate a newly developed CBCT system in defining CI electrode array in human temporal bone and cochlear morphological variation. Methods: Standard electrode, flexible tip electrode (Flex28), and an experimental electrode array with 36 contacts from MED-EL were implanted into the cochleae of six human temporal bones through an atraumatic round window membrane insertion. The cochleae were imaged with 900 frames using an experimental set-up based on a CBCT scanner installed with Superior SXR 130-15-0.5 X-ray tube in combination with filtration of copper and aluminum. Results: In all temporal bones, the landmarks of the cochlea, modiolus, osseous spiral lamina, round window niche, and stapes were demonstrated at an average level of 3.4–4.5. The contacts of electrode arrays were clearly shown to locate in the scala tympani. There was a linear correlation between the ‘A’ value and cochlea height, and between the A value and actual electrode insertion length for the first 360° insertion depth.

Auditory localization by subjects with unilateral tinnitus

Tinnitus is associated with changes in neural activity. How such alterations impact the localization ability of subjects with tinnitus remains largely unexplored. In this study, subjects with self-reported unilateral tinnitus were compared to subjects with matching hearing loss at high frequencies and to normal-hearing subjects in horizontal and vertical plane localization tasks. Subjects were asked to localize a pink noise source either alone or over background noise. Results showed some degree of difference between subjects with tinnitus and subjects with normal hearing in horizontal plane localization, which was exacerbated by background noise. However, this difference could be explained by different hearing sensitivities between groups. In vertical plane localization there was no difference between groups in the binaural listening condition, but in monaural listening the tinnitus group localized significantly worse with the tinnitus ear. This effect remained when accounting for differences in hearing sensitivity. It is concluded that tinnitus may degrade auditory localization ability, but this effect is for the most part due to the associated levels of hearing loss. More detailed studies are needed to fully disentangle the effects of hearing loss and tinnitus.

Characteristics and international comparability of the Finnish matrix sentence test in cochlear implant recipients

Objectives: The first Finnish sentence-based speech test in noise—the Finnish matrix sentence test—was recently developed. The aim of this study was to determine the characteristics of the new test with respect to test-retest reliability, speech recognition curve, and international comparability in Finnish cochlear implant (CI) recipients. Design: The speech reception thresholds (SRT) were measured by means of an adaptive test procedure and compared with the results of the traditional Finnish word test. Additional measurements for concurrent slope and SRT estimation were conducted to determine the speech recognition curve and to check the test-retest reliability. Study sample: The measurements were performed on 78 Finnish CI recipients. In a subset of 25 patients, additional measurements for test-retest reliability and slope determination were performed. Results: The mean SRT was − 3.5 ± 1.7 dB SNR, with only a weak correlation with the Finnish word test. Test-retest reliability was within ± 1 dB and the mean slope of the speech recognition curve was 14.6 ± 3.6 %/dB. The rehabilitation results were similar to the results published for the German matrix test. Conclusions: The Finnish matrix test was found to be suitable and efficient in CI recipients with similar characteristics as the German matrix test.

Label-free visualization of cholesteatoma in the mastoid and tympanic membrane using CARS microscopy☆

Objective The present study aimed to evaluate the possibility of using coherent anti-Stokes Raman spectroscopy (CARS) microscopy to determine the specific molecular morphology of cholesteatoma by detecting the natural vibrational contrast of the chemical bonds without any staining. Materials and methods Specimens from the mastoid and tympanic membrane with and without cholesteatoma were analyzed using CARS microscopy, two-photon excited fluorescence (TPEF) microscopy, and the second harmonic generation (SHG) microscopy. Results In cholesteatoma tissues from the mastoid, a strong resonant signal at 2845 cm−1 was observed by CARS, which indicated the detection of the CH2 hydro-carbon lipid bonds that do not generate visible signals at 2940 cm−1 suggestive of CH3 bonds in amino acids. A strong resonant signal at 2940 cm−1 appeared in an area of the same specimen, which also generated abundant signals by TPEF and SHG microscopy at 817 nm, which was suggestive of collagen. In the tympanic membrane specimen with cholesteatoma, a strong resonant signal with corrugated morphology was detected, which indicated the presence of lipids. A strong signal was detected in the tympanic membrane with chronic otitis media using TPEF/SHG at 817 nm, which indicated collagen enrichment. The CARS and TPEF/SHG images were in accordance with the histology results. Conclusion These results suggest the need to develop a novel CARS microendoscope that can be used in combination with TPEF/SHG to distinguish cholesteatoma from inflammatory tissues.

The development and evaluation of the Finnish digit triplet test

Abstract Objectives: The aim of the study was to develop a reliable and easily accessible screening test for primary detection of hearing impairment. Methods: Digits 0–9 were used to form quasirandom digit triplets. First, digit specific intelligibility functions and speech recognition thresholds (SRTs) were determined. To homogenize the test material digits with steep intelligibility function slopes were chosen and level correction up to ±2u2009dB were applied to the digits as needed. Evaluation measurements were performed to check for systematic differences in intelligibility between the test lists and to obtain normative reference function for normal-hearing listeners. Results: The mean SRT and the final slope of the test lists were −10.8u2009±u20090.1u2009dB signal-to-noise ratio (SNR) and 21.7u2009±u20091.8%/dB, respectively (measurements at constant level; inter-list variability). The mean SRT and slope of the test subjects were −10.8u2009±u20090.5u2009dB SNR and 23.4u2009±u20095.2%/dB (measurements at constant level; inter-subject variability). The mean SRT for normal-hearing young adults for a single adaptive measurement is −9.8u2009±u20090.9u2009dB SNR. Conclusion: The Finnish digit triplet test is the first self-screening hearing test in the Finnish language. It was developed according to current standards, and it provides reliable and internationally comparable speech intelligibility measurements.