Digital Volume Tomography: Radiologic Examinations of the Temporal Bone

Evaluation of the Morphometry of the Stylomastoid Foramen in the Turkish Population: A Retrospective Study Using Cone-Beam Computed Tomography (CBCT)

Objectives  This study aimed to investigate the morphometric features of the stylomastoid foramen (SMF) and the facial canal in the Turkish population using cone-beam computed tomography (CBCT) retrospectively. Methods  The randomly selected 479 patients aged from 8 to 87 years were examined, and a total of 958 CBCT images of the SMF and facial canal (FC) were analyzed. The diameter of the SMF and FC at the mastoid segment and their relation to age, gender, and side were evaluated. Statistical analyses were performed using Kolmogorov-Smirnov, one-way analysis of variance, Student's t -test, chi-squared test, Tukey's honestly significant difference, and Fisher-Freeman-Halton exact test. p -Values < 0.05 were accepted as statistically significant at the 95% confidence interval. Results  The mean age of the patients was 40.49 ± 19.73 years. The mean diameter of the right SMF was 2.24 ± 0.58 and 2.50 ± 0.63 mm in females and males. The mean diameter of the left SMF was 2.25 ± 0.56 and 2.44 ± 0.62 mm in females and males. The mean diameter of the right FC was 1.60 ± 0.35 and 1.70 ± 0.34 mm in females and males. The mean diameter of left FC was 1.55 ± 0.35 and 1.66 ± 0.33 mm in females and males. A statistically significant difference was found between the age groups in terms of the mean SMF and FC diameter on both sides ( p  < 0.05). Conclusion  Information obtained from this study regarding the morphometric features of the SMF and thereby FC may assist surgeons in treatment plans and reduce the risk of neurosurgical complications.

The morphometric analysis of mastoid foramen and mastoid emissary canal on cone-beam computed tomography (CBCT)

PURPOSE

The purpose of this retrospective study was to assess the prevalence and morphometric features of the mastoid foramen (MF) and mastoid emissary canal (MEC) using cone-beam computed tomography (CBCT), as well as their relationship with age, sex, and side.

METHODS

CBCT scans of 500 patients aged 8-87 years were examined retrospectively. The presence and number of MF, mean diameter of the MEC and MF, MF location, and the distance between MF and asterion were all examined. The collected data were subjected to appropriate statistical analysis. P values < 0.05 were accepted as statistically significant at a 95% confidence interval.

RESULTS

The study included 472 patients. MF was present in 82% and absent bilaterally in 18% of the 472 patients. The prevalence of MF was 67.8% on the right side and 65.7% on the left. The mean diameter of the MF was 3.39 ± 1.48 mm and the number of the MF ranged from zero to four. The mean diameter of the MEC was 2.05 ± 1.06 mm and the distance between MF and asterion was 22,46 ± 5,18 mm. 52.4% of the MF was observed on the occipito-mastoid suture.

CONCLUSION

To prevent surgical complications, particularly those that concern the temporal and mastoid areas, radiologists should report the results of the preoperative examination of the morphometry of the MF and MEC. CBCT imaging is a reliable diagnostic method that can be used to evaluate the MEC and MF before surgical procedures.

Titanium and Platinum-Fluoroplastic Stapes Prostheses Visualization on Cone Beam Computed Tomography and High-Resolution Computed Tomography

Objective: The aim of this study was to evaluate whether stapes prostheses can be visualized with less metal artifacts and therefore more accurately on cone beam computed tomography in comparison to computed tomography imaging. Recent studies have shown that cone beam computed tomography has advantages when imaging metal artifacts. Patients with hearing loss or vertigo, who have undergone stapedotomy, often present a challenge for otologic surgeons. Imaging studies can deliver crucial additional information. Methods: A retrospective analysis of imaging studies and clinical data in a tertiary care center were carried out. Forty-one patients with forty-five implanted ears were evaluated in the study. All included patients had been implanted with a platinum-fluoroplastic (n = 19) or titanium (n = 26) piston and subsequently had undergone imaging months or years after surgery for various reasons. Patients underwent computed tomography or cone beam computed tomography of the temporal bone depending on availability. Piston visualization, prosthesis length, vestibular intrusion and audiologic results were compared between the groups. Piston position on imaging studies were compared to intraoperative findings. Results: Functional length measurements of all prostheses were carried out with a mean error of -0.17 mm (±0.20). Platinum-fluoroplastic protheses were significantly underestimated in length compared to titanium prostheses. To analyze the material-dependent difference in the measurement errors of the imaging techniques the interaction was tested in an ANOVA model and showed no statistically significant result (p = 0.24). The blinded neuroradiologist viewed two implants, both platinum-fluoroplastic pistons, as located outside of the vestibule due to an underestimation of the prothesis length and the missing radiodensity of the lower end of the prosthesis. Conclusion: Surgeons and radiologists should be aware of the different types and radiologic features of stapes prostheses and the missing radiodensity of some protheses parts. Cone beam computed tomography is an imaging alternative with a potential advantage of reduced radiation in patients after stapes surgery suffering from vertigo or hearing loss to evaluate piston position.

Volume-rendered computed tomography images of the surgical field for endolymphatic sac surgery

PURPOSE

Identification of the endolymphatic sac has failed occasionally. Postoperative complications have also rarely been reported. Given a safer and more reliable surgery, preoperative anatomical assessments are valuable, however, the vestibular aqueduct has seldom been seen with multi-planar reconstruction (MPR) computed tomography (CT) images yet. Our study aimed to determine the significance and utility of volume-rendered (VR) CT images of the surgical field for identifying the vestibular aqueduct, compared with MPR CT images.

SUBJECTS AND METHODS

14 patients with Meniere's disease who underwent endolymphatic sac surgery between 2008 and 2011. Location and size of the vestibular aqueduct were assessed using VR and MPR CT images, independently.

RESULTS

Accuracy of identifying the location differed significantly between VR and MPR CT images (rate of total correct evaluations: 100% by VR CT images vs 75% by MPR CT images, p = 0.02). Size was correctly identified in cases with a small endolymphatic sac using VR CT images (rate of total correct evaluations for size of the vestibular aqueduct: 100% by VR CT vs 57% by MPR CT, p = 0.046). VR CT images also demonstrated clearly the relationship between the endolymphatic sac and high jugular bulb. In two cases, the endolymphatic sac was identified by VR images, not by MPR images.

CONCLUSION

Accurate information about the location and size of vestibular aqueduct can allow sac surgeons to identify a tiny endolymphatic sac more easily and certainly, and also aids surgical trainees to learn sac surgery safely.

The gray scale value of ear tissues undergoing volume-rendering high-resolution cone-beam computed tomography

OBJECTIVE

When the thresholds for VR reconstruction from multi-slice CT images are changed, problems develop when assessing pathologies in the absence of standardized thresholds. The advantages of CBCT include lower radiation exposure compared with other techniques and better visualization of small ear structures. However, a disadvantage is that the scanner provides unstandardized gray scale values, thus not CT numbers (Hounsfield units, HU).

METHODS

We analyzed 88 sets of volume data obtained from temporal bones. The gray scale values were measured in aerated areas (two sites), along the ossicular chain (four sites) and in a bone area (one site) in the external and middle ears, and in soft tissue areas (five sites) and bone areas (two sites) in the inner ear.

RESULTS

The standard male and female gray scale values were 2448-2970 and 2585-3091 for the aerated areas, 3248-4945 and 3359-5223 for the ossicular chains, 3368-4109 and 3371-4147 for soft tissues, and 4790-5776 and 5044-5959 for bone, respectively. Sex significantly affected the values (p<0.05). Significant differences between aerated areas and ossicular chains, and between soft tissues and bone, were evident (all p<0.0001).

CONCLUSION

Volume-rendering (VR) images obtained by cone-beam computed tomography (CBCT) can be standardized simply by using fixed thresholds.

Flat Panel Angiography in the Cross-Sectional Imaging of the Temporal Bone: Assessment of Image Quality and Radiation Dose Compared with a 64-Section Multisection CT Scanner

BACKGROUND AND PURPOSE

Cross-sectional imaging of the temporal bone is challenging because of the complexity and small dimensions of the anatomic structures. We evaluated the role of flat panel angiography in the cross-sectional imaging of the temporal bone by comparing its image quality and radiation dose with a 64-section multisection CT scanner.

MATERIALS AND METHODS

We retrospectively collected 29 multisection CT and 29 flat panel angiography images of normal whole-head temporal bones. Image quality was assessed by 2 neuroradiologists, who rated the visualization of 30 anatomic structures with a 3-point ordinal scale. The radiation dose was assessed with an anthropomorphic phantom.

RESULTS

Flat panel angiography showed better image quality than multisection CT in depicting the anterior and posterior crura of the stapes, the footplate of the stapes, the stapedius muscle, and the anterior ligament of the malleus (P < .05). In contrast, multisection CT showed better image quality than flat panel angiography in assessing the tympanic membrane, the bone marrow of the malleus and incus, the tendon of the tensor tympani, the interscalar septum, and the modiolus of the cochlea (P < .05). Flat panel angiography had a significantly higher overall image quality rating than multisection CT (P = .035). A reduction of the effective dose of approximately 40% was demonstrated for flat panel angiography compared with multisection CT.

CONCLUSIONS

Flat panel angiography shows strengths and weaknesses compared with multisection CT. It is more susceptible to artifacts, but due to the higher spatial resolution, it shows equal or higher image quality in assessing some bony structures of diagnostic interest. The lower radiation dose is an additional advantage of flat panel angiography.

A retrospective, semi-quantitative image quality analysis of cone beam computed tomography (CBCT) and MSCT in the diagnosis of distal radius fractures

OBJECTIVE

To compare image quality and diagnostic validity of CBCT and MSCT for distal radius fractures.

METHODS

35 CBCT and 33 MSCT scans were retrospectively reviewed with a visual grading scale regarding the depiction of cortical bone, trabecular bone, articular surfaces, and soft tissue. The extent and type of artefacts was analyzed. Agreement on AO classification and measurement of cortical disruption and length of the fracture gap was determined. Fracture reduction was evaluated in post-treatment x-rays. Statistical analysis was performed with visual grading characteristics (VGC), chi square tests, and Kendall's coefficient of concordance.

RESULTS

CBCT performed significantly worse for cortical bone, articular surfaces, and especially soft tissue. Trabecular bone showed no significant difference. Significantly more CBCT images showed artefacts. Physics-based artefacts were the most common. CBCT scans also showed motion artefacts. There was no significant difference in agreement on AO classification. The agreement on measurements was substantial for both modalities. Slightly more fractures that had undergone MSCT imaging showed adequate reduction.

CONCLUSION

This initial study of an orthopaedic extremity CBCT scanner showed that the image quality of a CBCT scanner remains inferior for most structures at standard settings. Diagnostic validity of both modalities for distal radius fractures seems similar.

KEY POINTS

• Subjectively, CBCT remains inferior to MSCT in depicting most structures. • Similar diagnostic validity for CBCT and MSCT imaging of distal radius fractures. • CBCT is a possible alternative to MSCT in musculoskeletal imaging. • Visual grading characteristics (VGC) analysis proves useful in analyzing visual grading scales.

Direct comparison of conventional radiography and cone-beam CT in small bone and joint trauma

OBJECTIVE

To compare the diagnostic value of cone-beam computed tomography (CBCT) and conventional radiography (CR) after acute small bone or joint trauma.

MATERIALS AND METHODS

Between March 2013 and January 2014, 231 patients with recent small bone or joint trauma underwent CR and subsequent CBCT. CR and CBCT examinations were independently assessed by two readers, blinded to the result of the other modality. The total number of fractures as well as the number of complex fractures were compared, and inter- and intraobserver agreement for CBCT was calculated. In addition, radiation doses and evaluation times for both modalities were noted and statistically compared.

RESULTS

Fracture detection on CBCT increased by 35% and 37% for reader 1 and reader 2, respectively, and identification of complex fractures increased by 236% and 185%. Interobserver agreement for CBCT was almost perfect, as was intraobserver agreement for reader 1. The intraobserver agreement for reader 2 was substantial. Radiation doses and evaluation time were significantly higher for CBCT.

CONCLUSION

CBCT detects significantly more small bone and joint fractures, in particular complex fractures, than CR. In the majority of cases, the clinical implication of the additionally detected fractures is limited, but in some patients (e.g., fracture-dislocations), the management is significantly influenced by these findings. As the radiation dose for CBCT substantially exceeds that of CR, we suggest adhering to CR as the first-line examination after small bone and joint trauma and keeping CBCT for patients with clinical-radiographic discordance or suspected complex fractures in need of further (preoperative) assessment.

Diagnostic imaging modalities in head and neck disease

BACKGROUND

Because of the complex anatomy of the head and neck region, conventional projection radiography alone is unreliable and carries a high risk of misdiagnosis. The poor risk-benefit ratio of conventional radiography has led to their replacement by tomographic imaging for nearly all studies in this region.

METHOD

This review is based on pertinent articles retrieved by a selective search in the PubMed database (January 1980 to May 2013) as well as on the relevant guidelines from Germany and abroad.

RESULTS

The indication for diagnostic imaging in the anatomically complex head and neck region should be established for a specific type of imaging study on the basis of a thorough clinical examination. Conventional films, though easy to obtain, often cannot answer the diagnostic question and may yield confusing information leading to misdiagnosis. Computed tomography (CT) has the best risk-benefit profile and a high diagnostic value, but low-dose protocols have not yet been put into use in all centers. Magnetic resonance imaging (MRI) is best for bone and soft-tissue diagnosis, but consumes more resources. Digital volume tomography (DVT) is another type of three-dimensional, sectional imaging with high local resolution; the associated radiation exposure and image quality are generally both low, but may vary depending on the apparatus used. DVT cannot be used to evaluate the soft tissues. Ultrasonography can be used to evaluate superficial structures in the head and neck region; nuclear imaging can be used to evaluate thyroid disease and cancer.

CONCLUSION

Inflammatory, traumatic, and neoplastic diseases of the head and neck are best evaluated with cross-sectional imaging (CT, MRI) in accordance with current guidelines. Conventional x-rays should, in general, only be used for dental evaluation, with rare exceptions.

Radiographic evaluation of bone density around immediately loaded implants

Understanding the changes in bone density after insertion of dental implants and their relation to immediate loading is essential to achieving improvements in their survival rate. Histological investigations of the bone bed in humans are limited, which in turn hampers opportunities to deepen knowledge about the remodelling process around dental implants. The aim of the present study was to follow the change in bone density by measuring the grey values of cone beam computed tomography (CBCT) at different periods subsequent to implant insertion. The CBCTs of 20 individual immediately loaded implants were evaluated at three time points: prior to surgery, one month following, and six months after the operation. The grey values were measured at different regions around the implants. Reduction in the grey values was observed with respect to the reference values after one month and six months from implant insertion in the apical, middle, and cervical regions. No correlation was detected either between the change in grey values and drilling method or with the measured primary and secondary stabilities by Osstell ISQ instrument. Cone beam computed tomography can be used as a qualitative method to support clinical follow up and monitor the changes in bone density around implants in critical cases.

Differences of radiological artefacts in cochlear implantation in temporal bone and complete head

OBJECTIVES

Accurate radiological evaluation of cochlear implants is essential for improvement of devices and techniques and also for assessing the position of the electrodes within the cochlea. Radiological study of implants has focused on isolated temporal bones. Previous studies showed relevant sizes of artefacts (dimensions of the radiological image compared with the actual dimensions of the electrode) in visualization of cochlear implants in computed tomography and cone beam computed tomography (CBCT). In this study, we aimed to obtain CBCT images of cochlear electrodes in isolated temporal bones and in whole heads and to assess the differences in image quality between the two.

METHODS

Cochlear electrodes were implanted in three complete human heads. Radiological examinations were performed using a single CBCT scanner with varying x-ray tube currents, voltages, and rotation angles. The temporal bones were then removed and the same radiological examinations were repeated, with and without the receiver coils. Artefacts from a basal electrode (electrode 9) and an apical electrode (electrode 2) were calculated. These were compared with each other by measuring the diameter of the image of the electrode (electrode inclusive of imaging artefacts) and with the real electrode diameters from the manufacturer's data. Additionally, the radiological diameters (inclusive of artefact) of the electrodes were compared to the cross-sectional diameters of the basal and apical coils of the cochlea at the locations of these two electrodes.

RESULTS

In comparison to the real electrode diameters, radiological artefact proportions of 51-58% for electrode 9 and 56-61% for electrode 2 were calculated. The differences between whole head images (group 1) and temporal bone images with and without the receiver coil (groups 2 and 3) were highly significant for each protocol (P < 0.001).

DISCUSSION AND CONCLUSION

These results indicate that it is not possible reliably to determine the exact intracochlear positions of electrodes using CBCT. Imaging of isolated temporal bones produced significantly greater artefacts than imaging of the whole head. Evaluations of image quality based only on results for isolated temporal bones are not transferable to clinical situations, and should be assessed critically.

Width of the normal facial canal measured by high-resolution cone-beam computed tomography

CONCLUSIONS

In the facial canal, discrepancies between left and right side measurements at each point may be useful in the assessment and diagnosis of facial canal-related pathologies.

OBJECTIVES

This study was performed to obtain accurate and high-resolution images of the normal facial canal and measure its widths on cross-sections of the canal at anatomically and clinically important sites using high-resolution cone-beam computed tomography (CBCT).

METHODS

CBCT volume data of bilateral temporal bones were obtained from 28 healthy adult volunteers. The widths of the bony facial canals were measured at the meatal foramen, the cochleariform process, the stapes, the pyramidal eminence, and the point of emergence of the chorda tympani in the vertical segment.

RESULTS

The widths of the facial canal at each point were similar bilaterally (r = 0.54-0.85, p < 0.01), but showed regional differences and site-specific variations. The narrowest of the five sites was the level of the meatal foramen (p < 0.05), as reported previously. The second narrowest site was the level of the stapes (p < 0.01) followed in order by the level of the cochleariform process, the pyramidal eminence, and the point of emergence of the chorda tympanis (p < 0.01).

Visualisation of the Bonebridge by means of CT and CBCT

Background

With the Bonebridge, a new bone-anchored hearing aid has been available since March 2012. The objective of the study was to analyse the visualisation of the implant itself as well as its impact on the representation of the bony structures of the petrosal bone in CT, MRI and cone beam CT (CBCT).

Methods

The Bonebridge was implanted unilaterally in two completely prepared human heads. The radiological imaging by means of CBCT, 64-slice CT, 1.5-T and 3.0-T MRI was conducted both preoperatively and postoperatively. The images were subsequently evaluated from both the ENT medical and nd radiological perspectives.

Results

As anticipated, no visualisation of the implant or of the petrosal bones could be realised on MRI because of the interactive technology and the magnet artefact. In contrast, an excellent evaluability of the implant itself as well as of the surrounding neurovascular structures (sinus sigmoideus, skull base, middle ear, inner ear, inner auditory canal) was exhibited in both the CT and in the CBCT.

Conclusion

The Bonebridge can be excellently imaged with the radiological imaging technologies of CT and CBCT. In the process, CBCT shows discrete advantages in comparison with CT. No relevant restrictions in image quality in the evaluation of the bony structures of the petrosal bones could be seen.

Imaging of ancient Egyptian mummies' temporal bones with digital volume tomography

The radiographic imaging of ancient Egyptian mummies has always been of great interest. Computed tomography is the method of choice to demonstrate bony pathologies with high quality. As digital volume tomography (DVT) is an extension of panoramic tomography with a very high resolution, its qualities were evaluated by examination of temporal bones of Egyptian mummy skulls. Ten Egyptian mummy skulls from the Zoological Collection Marburg, estimated 1,700-5,000 years of age, from Abydos, Philae, Theben-West and Sakkarah, were examined by DVT (3D Accuitomo, Morita, Japan). Through a rotation 360° of the X-ray source around the region of interest, a cylinder of 3 × 4 cm was captured as a three-dimensional volume. The gained data were analyzed with the help of special software on a PC. The angles of the axial, coronal and sagittal sections were arbitrarily changed to represent single structures with high resolution of 0.125 mm to analyze specific anatomical structures. In all skulls, conditions of the temporal bone and its anatomical structures were evaluated and normal as well as pathological findings evaluated in detail. The analysis of special landmarks such as the ossicular chain, cochlea, external, and internal auditory canal, facial nerve canal, and semicircular canals showed an intact ossicular chain in six temporal bones, while only isolated and dislocated ossicles were found in eight temporal bones. Besides one dehiscence of the superior semicircular canal in one temporal bone which might have led to vertigo and deafness at lifetime, all other findings were normal. Fragments of foreign bodies additionally found in the labyrinth, external ear canal and intracranially were attributed to postmortem damage. Digital volume tomography extends the imaging possibilities of CT for paleoradiological evaluation of temporal bones. With its high resolution, geometric accuracy, reconstruction capabilities, rapidness, and comparably low costs, even small bony pathologies are precisely demonstrated in a limited area. Investigations of larger numbers of specimen might reveal further details of ancient history for further interdisciplinary investigation of anthropologists, Egyptiologists, otolaryngologists, and radiologists.

Analysis of pneumatization and neurovascular structures of the sphenoid sinus using cone-beam tomography (CBT)

BACKGROUND

The sphenoid sinus is a frequent target of paranasal sinus surgery. Because of the high risk of injuring the surrounding structures (e.g. internal carotid artery, optical nerve) a preoperative imaging is absolutely necessary.

PURPOSE

To analyze the possibilities of cone-beam computed tomography (CBCT), which is especially quite a new technique in ENT, in the evaluation of the sphenoid sinus, its surrounding structures, and the corresponding anatomical variations.

MATERIAL AND METHODS

This was a retrospective, single-centre study of 580 patients (1160 sides = cases). The Accu-I-Tomo-F17 was used. Pneumatization of sphenoid sinus, course of internal artery, course of optical nerve, and dehiscence of the bony canals were evaluated.

RESULTS

In the case of pneumatization a type I (completely missing or minimal sphenoid sinus) was found in two patients (0.3%), type II (posterior wall of sphenoid sinus is in front of the anterior wall of the sella) in 38 patients (6.6%), type III (posterior wall is between anterior and posterior wall of sella) in 332 patients (57,2%), type IVa (posterior wall is behind the posterior wall of sella without air dorsal the sella) in 104 patients (17.9%), and type IVb (similar to type IVa but with air dorsal the sella) in 104 patients (17.9%). In 1025 cases (89.5%) a smooth course of the internal carotid artery was found whereas a free course could be detected in 120 cases (10.5%). Defects of the bony canal of the optical nerve were found in 16.7% and of the internal carotid artery in 2.7% of the cases. The optical nerve showed a free course through the sphenoid in 151 cases (13.7%) and a smooth course in 1007 cases (87.0%).

CONCLUSION

CBCT could evaluate all relevant anatomic structures and answer the questions of different anatomical variants. A modified classification of the pneumatization of the sphenoid sinus could be described. Frequencies of anatomical variations are in accordance with the current literature of CT research.

Controlling the position and the dislocation of the middle ear transducer with high-resolution computed tomography and digital volume tomography: implications for the transducers' design

A minimal tip dislocation of the middle ear transducer (MET(®), Otologics Ltd) may result in poor hearing performance. Our objective was to examine if a defined MET dislocation can be diagnosed by high-resolution computed tomography (HRCT) or digital volume tomography (DVT). A human cadaver head was sequentially implanted with different MET tips (incus application) including a ceramic tip (T 1c), a titanium tip (T 1t), a new, thinner titanium tip (T 2), and a spherical titanium tip (Ts). HRCT and DVT studies were performed. Afterward, the tips were pulled back 0.5 mm, so that they were not attached to the incus. HRCT and DVT scans were repeated to identify the dislocation. Using the best plain in HRCT images, the dislocation of the transducer could be measured reliably and reproducibly in half of the cases. In particular, the precise positioning and the dislocation could be identified when T 1t and Ts were implanted, with the Ts showing the best visibility. DVT failed in recognizing the dislocation in all cases. The identification of MET tip's dislocation with HRCT depends on the shape, size, and material of the tip. This knowledge is useful for the design of the implants, as determination of the right position of the middle ear transducer may be proven important for the hearing outcome. In some cases, however, surgical exploration may still be required. Although DVT represents a promising imaging method for the otologists, it can barely help when MET dislocation is suspected.

Artifacts of the electrode in cochlea implantation and limits in analysis of deep insertion in cone beam tomography (CBT)

Until now more than 250,000 cochlea implantations have been performed worldwide. The surgical procedure is well standardized. A discussion about the kind of postoperative radiological control has started since cone beam tomography (CBT) has been established in ENT and hearing preservation operations have come more into the focus. Further research has been concentrated on the role of CBT and the insertion of the basal turn. The aim of this study was to look for the possibilities of CBT and deep insertion. The second aim was to analyze the artifacts of cochlea implants in CBT. Three human cadaver ears were implanted with a flex soft electrode of MedEl© in a standard operation procedure with round window insertion and a full insertion. Afterwards 72 CBT sets per ear were performed with different X-ray-tube currents (2-10 mA), voltages (72-90 kV), and exposure times (9 and 17 s). On each data set, the radiological diameter of the electrode 9 (basal), electrode 2 (apical), the diameter of the cable next to the electrodes 9 and 2, and the associated diameter of the cochlea next to the electrodes 9 and 2 were evaluated. Additionally, a comparison to the real diameter was done. The mean radiological diameters of the measure point at electrode 9 were: electrode = 1.19 mm; cable = 0.65 mm; cochlea = 1.77 mm. Results for measure point at electrode 2 were: electrode = 0.98 mm; cable = 0.48 mm; cochlea = 1.21 mm. The real diameters were at electrode 9 in lateral view 0.58 mm and in top view 0.63 mm and at electrode 2 in lateral view 0.36 mm and in top view 0.50 mm. Differences between the diameters of the electrode 9 and 2 were highly significant. Interestingly, the real diameter of the electrode is half in comparison to the radiological one. Also in comparison to the diameter of the cable and the associated electrode is nearly half. Nearly 50% artifact exists on radiologic evaluation of the diameter of the electrode. Varying the X-ray adjustments did not lead to optimized results. The difficulties in evaluating a cochlea electrode with CBT could be shown. The high rate of artifacts (50%) makes it extremely difficult to predict the inserted scale, especially when evaluating the intracochlear position in the medial and apical turn of the cochlea. In conclusion, until now CBT allows a relatively safe evaluation of the electrode in the basal turn, whereas in deep insertion it is not really a useful tool to answer the question of insertion trauma, implanted scale, or scale displacements.

Finger fractures imaging: accuracy of cone-beam computed tomography and multislice computed tomography

OBJECTIVE

To compare the diagnostic accuracy and radiation exposure of cone beam computed tomography (CBCT) and multislice computed tomography (MSCT) in the evaluation of finger fractures.

MATERIALS AND METHODS

In a 3-year period, 57 consecutive patients with post-traumatic fractures of the metacarpal-phalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints with involvement of the articular surface were studied by means of CBCT and MSCT. Student's t test was used to compare CBCT and MSCT accuracy in evaluating the percentage of joint surface involvement and in detecting bone fragments. The average tissue-absorbed doses of CBCT and MSCT were also compared. A value of p < 0.05 was considered statistically significant. Inter-observer agreement was calculated.

RESULTS

In all cases, CBCT allowed the percentage of articular involvement to be correctly depicted compared with MSCT, showing 100% sensitivity and specificity (p < 0.001). A total of 103 bone fragments were depicted on MSCT (mean 3.8 per patient, range 1-23). CBCT indicated 92 out of 103 fragments (89.3%) compared with MSCT (mean diameter of missed fragments 0.9 mm, range 0.6-1.3 mm), with no statistically significant difference between CBCT and MSCT (p < 0.025). Multislice CT radiation exposure was significantly higher than that of CBCT (0.18 mSv vs 0.06 mSv, p < 0.0025). Inter-observer agreement was good (overall κ = 0.89-0.96).

CONCLUSIONS

Cone beam CT may be considered a valuable imaging tool in the preoperative assessment of finger fractures, when MSCT is not available.

The value of digital volume tomography in assessing the position of cochlear implant arrays in temporal bone specimens

OBJECTIVES

Radiological evaluation of the position of cochlear implant (CI) devices is an upcoming method for quality control after CI surgery. First, results of imaging of the middle and inner ear with digital volume tomography (DVT) show considerable advantages such as exceptional image quality, thin slice thickness, and low radiation dose. The aim of this study was to evaluate whether DVT is an appropriate method for postoperative imaging of CI patients and to identify the exact position of the implant array within the cochlear by multiple measurements.

DESIGN

Thirteen formalin-fixed temporal bone specimens were implanted with a CI array and scanned in DVT. To determine the exact electrode position, these specimens were ground and stained for microscopic measurements. The measurements on grindings acted as a referee and were compared with the measurements in DVT scans. The statistical analysis between the two measurement protocols was performed using the Bland-Altman method.

RESULTS

Best achievable agreement between DVT scans and histological reference was shown. Mean differences between DVT and grindings from -1.55 to -65.40 microm were calculated. All means are within the region of accuracy. General positioning of the implant into the cochlea could be verified in all specimens. The exact position of the implanted array within the cochlear scalae could be recognized correctly in 11 of 13 cases in DVT. It was possible to identify shiftings between the tympanic and vestibular scalae in all cases.

CONCLUSION

DVT seems to be a convenient technique for postoperative position control after cochlear implantation.

Digital volume tomography (DVT) as a diagnostic modality of the anterior skull base

CONCLUSION

Because of high resolution and the relatively lower costs in comparison with modern helical CT scanners, digital volume tomography (DVT) can be recommended in the diagnosis of the nasal cavity and paranasal sinuses.

OBJECTIVES

DVT is an advancement of panoramic tomography and is based on the principles of rotational tomography. It enables high resolution visualization of osseous structures. The slices can be displayed in three orthogonal planes that can be changed in angle arbitrarily. Data volumes of up to 12×17 cm can be examined with a new generation of the DVT. The aim of this study was to point out the potential of DVT in the anterior skull base.

SUBJECTS AND METHODS

DVT scans with a cylindrical size of 10 cm in diameter and 10 cm in height were performed in 23 patients. The identification of surgical key landmarks (uncinate process, middle turbinate, ethmoidal bulla, agger nasi cells, Haller cells, frontal recess, anterior ethmoidal artery in its relationship to the skull base, the cribiform plate of the sphenoidal sinus in relation to the optic nerve, and the internal carotid artery) was evaluated.

RESULTS

Display of the essential surgical key landmarks was possible in all patients.

Temporal bone imaging: comparison of flat panel volume CT and multisection CT

BACKGROUND AND PURPOSE

A recent development in radiology is the use of flat panel detectors in CT to obtain higher-resolution images. This technique is known as flat panel volume CT (fpVCT). We sought to compare the image quality and diagnostic value of 2 different flat panel detector-equipped scanners: one is a prototype fpVCT scanner, and the other is a so-called flat panel digital volume tomography (fpDVT) scanner, which is routinely used in clinical setup with current state-of-the-art multisection CT (MSCT) scanners.

MATERIALS AND METHODS

Five explanted temporal bones and 2 whole-head cadaveric specimens were scanned with fpVCT, fpDVT, and MSCT scanners. The image series were blindly evaluated by 3 trained observers who rated 38 anatomic structures with regard to their delineation/appearance.

RESULTS

Although the image quality obtained with fpVCT and fpDVT was rated significantly better compared with MSCT on isolated temporal bones, the differences were not significant when whole cadaveric heads were scanned.

CONCLUSIONS

Theoretic and practical advantages exist for flat panel detector-equipped scanners, including improved image quality. However, when imaging whole cadaveric heads, no significant difference could be demonstrated between them and standard-of-care MSCT.

Bionic ear imaging

PURPOSE

The aim of this study was to illustrate the different imaging features of middle and inner ear implants, brainstem implants and inferior colliculus implants.

MATERIALS AND METHODS

We retrospectively reviewed the computed tomography (CT) images of 468 patients with congenital or acquired transmissive or neurosensory hearing loss who underwent surgery. The implants examined were: 22 Vibrant Soundbridge implants, 5 at the long limb of the incus and 17 at the round window, 350 cochlear implants, 95 brainstem implants and 1 implant at the inferior colliculus. All patients underwent a postoperative CT scan (single or multislice scanner) and/or a Dentomaxillofacial cone-beam CT scan (CBCT) (axial and multiplanar reconstruction), and/or a plain-film radiography to visualise the correct position of the implant.

RESULTS

The CBCT scan depicts Vibrant site of implant better than plain-film radiography, with a lower radiation dose compared to CT. For cochlear implants, a single plain radiograph in the Stenvers projection can directly visualise the electrodes in the cochlea. All patients with brainstem or inferior colliculus implants underwent postoperative CT to exclude complications and the assess correct implantation, but the follow-up of these implants can be performed by plain radiography alone.

CONCLUSIONS

CT and CBCT scans are reliable and relatively fast methods for precisely determining the location of middle ear implants. CBCT is preferable to CT because of the lower radiation dose administered; a single plain-film radiograph is enough to visualise and follow-up cochlear, brainstem and inferior colliculus implants.