[Improvement of CT spatial resolution brings about enormous changes in the diagnosis and treatment of otological diseases].

CT examination of temporal bone is of great value in the diagnosis and treatment of otological diseases, and improvement in spatial resolution is an inevitable demand to enhance diagnostic efficiency. In the past 40 years, the spatial resolution of temporal bone CT has been continuously improved, making great contribution to improving the diagnosis and treatment level of otological diseases. The newly reported 10 µm otology CT device has greatly improved the ability to visualize fine structures and occult lesions of temporal bone key area and effectively reduced radiation dose, therefore it is expected to bring new changes to diagnosis and treatment of otological diseases.

[Analysis of the anatomical features of vestibular nerve canal based on 10 µm otology CT].

Objective: To analysis the anatomical features of normal vestibular nerve canal based on 10 µm otology CT. Methods: Sixty-seven patients (103 ears) underwent 10 µm otology CT examinations in Department of Radiology, Beijing Friendship Hospital, Capital Medical University from September 2020 to March 2021 were retrospectively recruited. There were 24 males and 43 females, aged from 18 to 70 (40±17) years. According to the morphology of the inferior vestibular nerve canal, it can be divided into four types as follows: uniform straight type, curved type, ampullary type and direct connection. The anatomical variables of the superior vestibular nerve canal (external orifice, isthmus and internal orifice widths, canal length, angle with labyrinthine segment of the facial nerve) and inferior vestibular nerve canal (widths of the externaland internal orifice, canal length, angles with long axis of the vestibule and the modiolus) between the different sides, genders and canal morphologies were analyzed and compared, respectively. Results: 100% superior vestibular nerve canals and 75.7% (78/103) inferior vestibular nerve canals are clearly depicted by otology CT. The left-side ear presented with larger internal orifice diameter of the superior vestibular neve canal [(1.46±0.47) mm vs (1.31±0.41) mm], and a smaller angle between the inferior vestibular neve canal and the modiolus [(41.6±16.9)° vs (51.6±21.0)°] than the right-side ear (all P<0.05, respectively), respectively. Compared to females, males demonstrated larger internal orifice of the superior vestibular nerve canal [(1.55±0.37) mm vs (1.28±0.36) mm, P<0.05]. The uniform straight type of the inferior vestibular nerve canal was the most common type (62.1%, 64/103), followed by the direct connection (19.4%, 20/103), and the ampullary type was the least common type (4.9%, 5/103). There were significant differences in external diameter and angles with the long axis of the vestibule and the modiolus between the four morphologies of the superior vestibular nerve canal (all P<0.05, respectively). Conclusion: Ten µm otology CT is capable of depicting normal vestibular nerve canal clearly. Quantitative measurement of the normal vestibular nerve canal can provide references for the imaging diagnosis and preoperative evaluation of lesions in this area.

[Analysis of spatial location of the malleus in patients with chronic otitis media based on 10 µm otology CT].

Objective: To assess the changes of the spatial location of the malleus in patients with chronic otitis media (COM) using 10 µm otology CT. Methods: Forty-five patients with COM (COM group, 45 ears) and 55 patients without external and middle ear disease (control group, 89 ears), who underwent 10 µm otology CT examination in Department of Radiology, Beijing Friendship Hospital, Capital Medical University from October 2020 to March 2021, were retrospectively collected during the same period. In the COM group, there are 20 males and 25 females, aged from 20 to 78 (40±14) years. In the control group, 29 were males and 26 were females, with age of 19 to 57 (32±11) years. The shortest distance between the malleus head and the upper wall, the distance between the outer edge of the malleus neck and the scutum, the distance between the outer edge of the malleus neck and the pars flaccida of the tympanic membrane, the shortest distance between the malleus head and the anterior wall, the shortest distance between the anterior process and the anterolateral wall, the shortest distance between the tip of the malleus handle and the promontory, and the shortest distance between the malleus head and the tympanic segment of the facial nerve were measured and compared between the two groups. Results: Compared with the control group, the head-upper wall distance (M (Q1, Q3)) (0.81 (0.48, 1.21) mm vs 0.57 (0.33, 0.90) mm) and the neck-scutum distance (1.79 (1.54, 2.13) mm vs 1.65 (1.48, 1.83) mm) were larger in the COM group (all P<0.05), and the neck-tympanic membrane distance (1.32 (1.15, 1.49) mm vs 1.45 (1.31, 1.59) mm) and the handle-promontory distance (1.56 (1.33, 2.09) mm vs 2.10 (1.74, 2.43) mm) were reduced in the COM group (all P<0.05, respectively). The neck-tympanic membrane distance on the left was larger than those on the right in the COM group (1.39 (1.19, 1.51) mm vs 1.21 (0.87, 1.31) mm, P<0.05). Conclusion: There are changes in the relative position of the malleus in patients with COM, which are helpful for further understanding the imaging manifestations in patients with COM.

[Application of 10 µm otology CT on evaluation of isolated malleus fixation in patients with conductive hearing loss].

Objective: To evaluate the application of 10 µm otology CT on evaluation of isolated malleus fixation (IMF) in patients with conductive hearing loss. Methods: A total of 19 patients (25 sides) with idiopathic hearing loss, including 8 males and 11 females, aged between 4 to 50 years, who underwent 10 µm otology CT examination in Department of Radiology, Beijing Friendship Hospital, Capital Medical University from October 2020 to July 2021, were retrospectively collected. For those patients with idiopathic hearing loss, there were 5 cases (6 sides), including 2 males and 3 females, with an average age of 18-70 [65(20,68)] years, with bony connection between malleus and tympanum wall. Eighteen sex-and age-matched cases with normal hearing group, including 6 males and 12 females, with an average age of 20-68 (39±14) years, as the ratio of 1∶3, were included as the controls. The distances of the tegmen tympani between malleus head and horizontal semicircular canal, as well the distances between malleus head and horizontal semicircular canal were retrospectively measured and further compared between the two groups. Results: The incidence of IMF in patients with idiopathic conductive hearing loss without other etiologies was 24.0% (6/25). The specificity of 10 µm otology CT in diagnosing IMF was 100%. The distances of tegmen tympani between horizontal semicircular canal and malleus head in IMF patients were significantly smaller compared with the controls [-0.65(-1.21, -0.35) mm vs 1.34(0.04, 1.68) mm;0.92(0.51, 1.49) mm vs 2.82(1.76, 3.53) mm](both P<0.05, respectively). There was no significant difference in distances between malleus head and horizontal semicircular canal [-1.30 (-1.90, -0.46)mm vs -0.42 (-1.15, 0.05),P=0.057]. Conclusions: IMF is not uncommon in conductive hearing loss without other causes, which can be clearly shown by 10 µm otology CT. Its occurrence is related to the local downward shift of tegmen tympani above the malleus, without upwards displacement of the malleus.

[Study on the relationship between the morphology of the isthmus of the vestibular aqueduct and Meniere's disease based on 10 µm otology CT].

Objective: To evaluate the morphology of isthmus of the vestibular aqueduct (VA) and its relationship with the occurrence, course of Meniere's disease (MD) and the degree of hearing loss based on 10 µm otology CT. Methods: A total of 13 patients with MD in Beijing Friendship Hospital, Capital Medical University from October 2020 to July 2021, including 4 males and 9 females, age from 16 to 77 (56±16) years, were prospectively enrolled. All patients underwent 10 µm otology CT examination. The included lesion side was the MD affected group (14 sides), and the non-lesion side was the MD healthy group (12 sides). According to the 1∶2 side, 16 sex-and side matched cases (28 sides) without external and middle ear disease were included in the control group, including 4 males and 12 females, age from 16 to 77 (56±14) years. The horizontal semicircular canal showed on the largest plane was considered as the standard cross-section, and continuous observation was made on this image. According to the display type of isthmus of the VA, it was divided into Ⅰ to Ⅳ grades. Kruskal Wallis test was used to compare the morphological differences of VA isthmus among the affected group, the healthy group and the control group. The degree of hearing impairment was assessed by pure tone audiometry (PTA) results, which were divided into normal/mild/moderate/moderately severe/severe/extremely severe hearing impairment. Spearman correlation analysis was used to compare the correlation between the morphological rating of VA isthmus on the affected side and age, course of disease and the results of pure tone audiometry (PTA). Results: The proportions of VA isthmic morphology GRADE Ⅰ,Ⅱ,Ⅲ,Ⅳ in the MD affected group were 28.6% (4/14), 42.9% (6/14), 21.4% (3/14), 7.1% (1/14), those in the MD healthy group were 0 (0/12), 33.3% (4/12), 33.3% (4/12), 33.3% (4/12), and those in the control group were 0 (0/28), 7.1% (2/28), 64.2% (18/28), 28.6% (8/28). The VA isthmus scores [M (Q1, Q3)] of MD affected group was lower than that of MD healthy group [2 (1, 3) vs 3 (2, 4)] and control group [2 (1, 3) vs 3 (3, 4)] (all P<0.05, respectively). The morphology of the VA isthmus on the affected side of MD was negatively correlated with age (r=-0.81, P=0.002), and there was no correlation with the course of disease and degree of hearing impairment (r=-0.40, r=-0.26; all P>0.05, respectively). Conclusion: The stenosis of the VA isthmus in MD was a possible anatomical factor for the occurrence of MD.

[Analysis of the imaging characteristics of otosclerosis based on 10 µm otology CT].

Objective: To evaluate the imaging features of otosclerosis based on10 µm otology CT. Methods: Data of 27 patients with otosclerosis (51 sides) in Beijing Friendship Hospital, Capital Medical University from October 2020 to July 2021 were retrospectively collected, including 9 males and 18 females age ffrom 22 to 70 (42±12) years. All patients underwent 10 µm otology CT examination and surgical treatment. The types, amounts and involved sites of otosclerosis were analyzed and the sensitivity of 10 µm otology CT in diagnosing otosclerosis were evaluated. Results: Fenestral type accounted for 49.0% (25/51 sides), and diffuse type accounted for 51.0% (26/51 sides),and he retrofenestral type without fenestral lesion was not seen. Single lesions accounted for 45.1% (23/51 sides) and multiple lesions accounted for 54.9% (28/51 sides). The incidence of involvement of the fissula ante fenestram and annular ligaments were both 100%. The incidence of involvement of stapes footplate, vestibule, cochlea, round window, inner auditory canal wall, facial nerve canal, stapes muscle and semicircular canal was 60.8% (31 sides), 33.3% (17/51 sides), 21.6% (11/51 sides), 17.6% (9/51 sides), 13.7% (7/51 sides), 9.8% (5/51 sides), 7.8% (4/51 sides) and 5.9% (3/51 sides), respectively. The sensitivity of 10 µm otology CT in diagnosis of otosclerosis was 100%. Conclusion: 10 µm otology CT can fully display the imaging features of otosclerosis, and has the potential to be an effective routine method for otosclerosis.

[Experimental comparison of temporal bone imaging protocol optimization between 10 µm otology CT and multi-slice CT].

Objective: To evaluate different protocol optimization strategies for temporal bone between10 µm otology CT and multi-slice CT (MSCT). Methods: Ten adult skull specimens (20-sides temporal bones) were prospectively enrolled. From October to November 2020, the temporal bones were scanned under four different imaging conditions using 10 µm otology CT (90 kV, 120 mAs; 90 kV, 140 mAs; 100 kV, 120 mAs; 100 kV, 140 mAs) and MSCT (120 kV, 220 mAs; 120 kV, 310 mAs; 140 kV, 160 mAs; 140 kV, 220 mAs), respectively. The image quality was subjectively scored using 5-grade scores, and the contrast noise ratio (CNR) of the image was measured. The absorbed dose of tissues and organs under different imaging conditions was measured by thermoluminescence dosimeter, and the effective dose was calculated. The figure of merit (FOM) is defined as the ratio of the square of the mean CNR to the effective dose. χ2 test was used to compare the difference of subjective scores of different scanning parameter groups, and paired t test was used to analyze and compare the difference of image CNR of different scanning parameter groups. The image quality, radiation dose and FOM of the combination of recommended parameters of the two devices were analyzed and compared. Results: For 10 µm otology CT, under 100 kV condition, the CNR of 140 mAs group was better than that of 120 mAs group (11.27±1.85 vs 10.26±1.38, P<0.001). There was no significant difference in subjective scores between the two groups [5.00 (4.00, 5.00) vs 5.00 (4.25, 5.00), P=0.264]. For MSCT, under 120 kV condition, the subjective scores and CNR of 310 mAs group were better than those of 220 mAs at 120 kV [4.00(3.00, 4.00) vs 3.00(3.00, 3.00),P=0.002;5.24±0.62 vs 4.60±0.62,P<0.001]. According to the principle of image quality-radiation dose optimization, the combination of 100 kV with 120 mAs and 120 kV with 310 mAs are recommended for 10 µm otology CT and MSCT, respectively. The subjective scores and CNR of 10 µm otology CT images were better than those of MSCT (5.00 (4.25, 5.00) vs 4.00 (3.00, 4.00), 10.26±1.38 vs 5.48±0.22, P<0.001). The effective dose was 1/3 of that of MSCT (82.99 µSv vs 252.56 µSv), and the FOM was 11.16 times of that of MSCT (1 268.44 mSv-1 vs 113.71 mSv-1). Conclusion: The temporal bone image quality of newly developed 10 µm otology CT is significantly better than that of MSCT, and its effective dose is lower than that of MSCT, which has more accurate and safer application potential.

[Analysis of the performance of a multi-view fusion and active contour constraint based deep learning algorithm for ossicles segmentation on 10 µm otology CT].

Objective: To explore the performance of a deep learning algorithm that combined multi-view fusion with active contour constrained for ossicles segmentation on the 10 µm otology CT images. Methods: The 10 µm otology CT image data from 79 cases (56 cases were from volunteers and 23 cases were from specimens) were retrospectively collected in the Radiology Department of Beijing Friendship Hospital from October 2019 to December 2020. An annotation of malleus, incus, and stapes were conducted. Then the datasets were established and were divided into training set (n=55), validation set (n=8), and test set (n=16). Using the rapid localization of the region of interest combined with the precise segmentation algorithm, the malleus, incus and stapes were segmented and fused from three perspectives of coronal, sagittal and cross-sectional views. Besides, an active contour loss was designed simultaneously for the segmentation of stapes. Dice similarity coefficient (DSC) was used as the objective evaluation metric for the evaluation of the segmentation results. The inter group DSC of the proposed method was compared with that of the basic method and other methods. Results: The average DSC values of the multi-view fusion segmentation algorithm for malleus, incus and stapes reached up to 94.2%±2.7%, 94.6%±2.6% and 76.0%±5.5%, respectively. After adopting the constraint of active contour loss method, the average DSC of stapes was improved (76.4%±5.4% vs 76.0%±5.5%). The visualization results also demonstrated that the segmentation results of the stapes were more complete. Conclusions: Multi-view fusion algorithm based on 10 µm otology CT images can realize accurate segmentation of malleus and incus. Combined with the constraint of active contour loss method, the segmentation accuracy of stapes can be further improved.

[A study of quantitative measurement of singular nerve canal with cone-beam computed tomography].

Objective: To explore the feasibility of cone beam computed tomography (CBCT) in quantitatively assessing singular nerve canal and to propose a method to locate singular nerve canal in CBCT imaging. Methods: Eight cadaveric heads were scanned using CBCT and images of 16 temporal bones were obtained.The diameters of three points of singular nerve canal were measured which included the internal auditory canal aperture, the central turning area, and the aperture of ampulla of the posterior semicircular canal.The length of singular canal was measured.The distances from the three points to the inner edge of round window were measured.The best oblique axial plane to display the whole course of singular canal was adjusted and the angle between this plane and the lateral semicircular canal was measured.Two independent sample t-test was used to compare the left and right measurements. Results: The mean diameters of the three points were(0.98±0.51), (0.36±0.05) and(0.38±0.06) mm respectively.The mean length of singular nerve canal was(4.16±0.87) mm.The mean angle was 19.1°±10.2°.2D and 3D location graphs of singular nerve canal were made with the distance between the three points on singular nerve canal and the medial end of the round window.There was no significant statistical difference between left and right side in all the measurement (all P>0.05). Conclusion: CBCT can clearly display the whole course of singular nerve canal.Measurement can be done on CBCT images, and the specific location of singular nerve canal can be determined, which are important for surgery.

[Comparative study on the display ability of CBCT and MSCT in vestibular aqueduct].

Objective: To compare the ability and visibility of cone-beam CT and MSCT in showing vestibular aqueduct. Methods: An experimental anatomical study which from June 2017 to August 2017 was performed on 76 temporal bones from 38 human cadavers with unknown clinical history. They all underwent CBCT and MSCT and all images were unified and standardized. The standard position was oblique sagital reconstruction.The length of the vestibular aqueduct, the midpoint and the external aperture width were measured on the standard position. The internal aperture, isthmus and proximal portion of the vestibular aqueduct on the images of the two kinds of equipment were evaluated. The measurement results of the two devices and image quality of the vestibular aqueduct were compared. Results: There was no significant statistical difference between the results of the measurement of CBCT and MSCT(P>0.05). In CBCT images, the total display rate of internal aperture was 77.6%(59/76), and the clearly display rate was 81.4%(48/59). The total display rate of the proximal portion of vestibular aqueduct was 57.0%(45/79), and the clearly display rate was 60.0%(27/45). The total display rate of isthmus of vestibular aqueduct was 59.2%(45/76), and the clearly display rate was 60.0%(27/45). In MSCT images, the total display rate of was 46.1%(35/76), and the clearly display rate was 60.0%(21/35). The total display rate of 5 of the proximal portion of vestibular aqueduct was 56.6%(43/76), the clearly display rate was 46.5%(20/43). The total display rate of isthmus of vestibular aqueduct was 68.4%(52/76), and the clear display rate 36.5%(19/52). There was significant statistical difference between the CBCT and the MSCT (P<0.05) in displaying of internal aperture of vestibular aqueduct. Conclusion: Compared with MSCT, the image of vestibular aqueduct obtained by CBCT can meet the diagnostic requirements and CBCT have better visibility in showing some subtle structures of vestibular aqueduct than MSCT.

[Feasibility study of cone-beam CT in displaying facial nerve canal].

Objective: To evaluate the image clarity of cone-beam computed tomography (CBCT) in displaying facial nerve canal and to investigate the feasibility of CBCT to display facial nerve canal and whether there are some advantages compared with MSCT. Methods: Eight cadaveric heads were scanned using CBCT and MSCT and images of 16 temporal bones of each scanner were obtained.The imaging clarity of facial nerve canal of the two scanners was scored.Wilcoxon test was used to assess the difference of the two methods.P<0.05 was considered statistically significant. The defects of the wall of facial nerve canal were also observed in the images of both scanners. Results: Sixteen structures of facial nerve canal were evaluated, including the wall of labyrinthine segment, the anterior, medial, lateral, superior, inferior wall of the first genu, the lateral, inferior wall of the anterior part of tympanic segment, the lateral, inferior wall of the posterior part of tympanic segment, the medial and superior wall of tympanic segment, the lateral, inferior, superior, medial wall of the second genu and the wall of mastoid segment.The clarity of thirteen structures showed no differences between the two scanners (P>0.05). The clarity of three structures showed significant differences between CBCT and MSCT (P<0.05), which included the superior wall of the first genu, the posterior part of the lateral wall and the anterior part of the inferior wall of tympanic segment, and the scores of CBCT were higher than MSCT.The most frequent region of defect was in the anterior part of inferior wall of tympanic segment (14/16), followed by the inferior wall of labyrinthine segment (9/16) and the superior wall of tympanic segment (6/16). Conclusion: Compared with MSCT, CBCT could also gain quite good imaging clarity for displaying facial nerve canal. The display effect of some fine structures, such as the lateral wall of tympanic segment, is better in the images of CBCT than in those of MSCT.

[Dosimetry of cone-beam computed tomography and multi-slice computed tomography scanning for temporal bone].

Objective: To compare the effective radiation dose levels of cone-beam computed tomography (CBCT) with those of multi-slice computed tomography (MSCT) when scanning for the temporal bone. Methods: The absorbed doses of CBCT and MSCT scanners were detected using thermoluminescent dosimeters (TLDs) that were placed in a head and neck phantom and a RGD-3D dose reader.Then the effective doses were calculated and expressed according to the International Commission on Radiation Protection (ICRP) 2007 guidelines. Results: Three-dimensional images about temporal bone can obtained by both CBCT and MSCT scanners in this study.The effective dose value of CBCT scanning for bilateral and unilateral temporal bone was 164.1 µSv (bone marrow: 32.1 µSv; thyroid gland: 10.6 µSv; salivary glands: 31.0 µSv), and 98.1 µSv (bone marrow: 17.4 µSv; thyroid gland: 6.2 µSv; salivary glands: 16.1 µSv), respectively.The dose of MSCT scanning for bilateral temporal bone was 714.6 µSv (bone marrow: 95.1 µSv; thyroid gland: 127.8 µSv; salivary glands: 135.7 µSv). Conclusions: When scanning for the temporal regions, the dose levels for CBCT are lower than those for MSCT.Dose levels reduction for CBCT could be obtained when smaller regions were scanned.

[Effect of intracerebroventricular neurotensin injection on blood pressure in rat].

Injection of neurotensin (NT) (10 and 20 micrograms/rat) into the lateral cerebroventricle (icv) could induce a rise or a drop of blood pressure and a slowing down of heart rate in urethane anaesthetized male rats (1.2 g/kg). The central pressor and depressor response to NT could be respectively blocked by pretreatment with alpha 1-receptor blocker prazosin (1.5 micrograms/3 microliters, icv) and M receptor blocker atropine (2.5 micrograms/3 microliters, icv). No significant changes in central cardiovascular responses to NT were observed following pretreatment with either H1 receptor blocker chlorpheniramin (50 micrograms/3 microliters, icv) or H2 receptor blocker cimetidine (250 micrograms/3 microliters, icv). In view of the above results it appears that NT, catecholamine and acetylcholine are all involved in central regulation of blood pressure.