Limited cone-beam computed tomography imaging of the middle ear: a comparison with multislice helical computed tomography

Assessment of subjective image quality, contrast to noise ratio and modulation transfer function in the middle ear using a novel full body cone beam computed tomography device

BACKGROUND

Multi slice computed tomography (MSCT) is the most common used method in middle ear imaging. However, MSCT lacks the ability to distinguish the ossicular chain microstructures in detail resulting in poorer diagnostic outcomes. Novel cone beam computed tomography (CBCT) devices' image resolution is, on the other hand, better than MSCT resolution. The aim of this study was to optimize imaging parameters of a novel full body CBCT device to obtain optimal contrast to noise ratio (CNR) with low effective dose, and to optimize its clinical usability.

METHODS

Imaging of five anonymous excised human cadaver temporal bones, the acquisition of the effective doses and the CNR measurements were performed for images acquired on using Planmed XFI® full body CBCT device (Planmed Oy, Helsinki, Finland) with a voxel size of 75 µm. All images acquired from the specimens using 10 different imaging protocols varying from their tube current exposure time product (mAs) and tube voltage (kVp) were analyzed for eight anatomical landmarks and evaluated by three evaluators.

RESULTS

With the exception of protocol with 90 kVp 100 mAs, all other protocols used are competent to image the finest structures. With a moderate effective dose (86.5 µSv), protocol with 90 kV 450 mAs was chosen the best protocol used in this study. A significant correlation between CNR and clinical image quality of the protocols was observed in linear regression model. Using the optimized imaging parameters, we were able to distinguish even the most delicate middle ear structures in 2D images and produce accurate 3D reconstructions.

CONCLUSIONS

In this ex vivo experiment, the new Planmed XFI® full body CBCT device produced excellent 2D resolution and easily created 3D reconstructions in middle ear imaging with moderate effective doses. This device would be suitable for middle ear diagnostics and for e.g., preoperative planning. Furthermore, the results of this study can be used to optimize the effective dose by selecting appropriate exposure parameters depending on the diagnostic task.

Insight in to the Awareness of CBCT as an Imaging Modality in the Diagnosis and Management of ENT Disorders: A Cross Sectional Study

The advent of Cone-beam computed tomography (CBCT), has revolutionized 3D imaging in dentistry. CBCT has enormous potential to be used as an alternative imaging modality by Otolaryngologists. But their knowledge regarding CBCT is limited. The study aims to evaluate the awareness of CBCT as an imaging modality among Ear, nose and Throat (ENT) practitioners. The validated questionnaire was sent by email and the participants were asked to fill the google form through the link provided to record the responses. The participants were asked to answer 25 multiple choice questions regarding the general information and practice related to CBCT imaging. Data was evaluated according to the descriptive statistics and the Chi-square test was used to determine the test of significance. The response rate for this study was 84.4%. The mean age of the participants was 44.9 ± 11.3. 69% of the respondents were academicians,14.2% had exclusive clinical practice, and 16.8% had both clinical and academic exposure. Among the study population, 76.8% had never advised CBCT in their practice. Only 10.3% of the study participants were aware of the potential of CBCT in ENT disorders. The mean knowledge, attitude and practice scores were very low regarding the applications of CBCT. Most of the study participants advised CBCT for maxillofacial fractures (78.1%) and was statistically significant p < 0.05. The knowledge about various advantages and clinical applications of CBCT among Otolaryngologists is limited. However, continuing medical education and inclusion in the medical curriculum will increase the scope and awareness about CBCT among ENT fraternity.

Evaluation of morphological variations of petrotympanic fissure using computed tomography imaging of the temporal bone

PURPOSE

Petrotympanic fissure (PF) is important for both dentists and otolaryngologists to know the temporal anatomy well especially for pre-surgical radiological evaluations. Computed tomography (CT) is indispensable method for temporal bone imaging. The purpose of this study was to evaluate PF morphology and position using CT.

METHODS

CT scans of 300 patients (600 PFs) were retrospectively evaluated. PF types were recorded by dividing into 3 groups (Type 1,2 and 3). Length of the mandibular fossa (MF) and PF, vertical diameter (VD) of the PF at the MF level, midpoint and tympanic cavity (TC) level were measured. PF position types were subdivided as low, midline and high.

RESULTS

Type 1, 2 and 3 was found in 18.7%, 51.5% and 29.8% of the cases, respectively. The mean length of the MF and PF was 18.33 mm and 3.77 mm, respectively. The mean VD of the PF at the MF level, midpoint and TC level was 1.71, 0.98 and 0.97 mm, respectively. The low, midline and high position of PF was observed 14.5%, 54.3% and 31.2% of the cases, respectively.

CONCLUSION

Length of the MF and PF in males was significantly higher than females. VD of the PF at the MF level in Type 1 and Type 3 was significantly higher than type 2. In type 1,VD of the PF at the midpoint was significantly higher than type 2 and type 3. VD of the PF at the TC level in Type 1 and Type 3 was significantly higher than type 2.

Cone-Beam CT Compared to Multi-Slice CT for the Diagnostic Analysis of Conductive Hearing Loss: A Feasibility Study

OBJECTIVES

Multislice computed tomography (MSCT) is commonly used as a diagnostic tool for patients with a conductive hearing loss. Recent studies indicate that cone-beam computed tomography (CBCT) may be used as a low-radiation dose alternative for temporal bone imaging. This study compares image quality and radiation dose between CBCT and MSCT when assessing anatomical landmarks related to conductive hearing loss.

MATERIALS AND METHODS

Five human cadaver heads (10 ears) were imaged on the NewTom 5G CBCT and the Discovery CT750 HD MSCT. Visibility of 16 anatomical landmarks of the middle and inner ear was assessed by two observers on a 4-point Likert scale. Furthermore, effective radiation dose was compared, and contrast-to-noise ratio and spatial resolution were measured with a phantom head.

RESULTS

Image quality of CBCT was assessed as superior to MSCT. Effective radiation dose of the high-resolution CBCT protocol was 30.5% of the clinical MSCT dose. High-resolution CBCT was reported as having a higher spatial resolution and superior contrast-to-noise perception in comparison with MSCT.

CONCLUSION

High-resolution CBCT was evaluated as superior to MSCT in the assessment of structures related to conductive hearing loss. Furthermore, CBCT imaging resulted in a considerably lower effective radiation dose.

Quantification of Joint Space Width Difference on Radiography Via Phase-Only Correlation (POC) Analysis: a Phantom Study Comparing with Various Tomographical Modalities Using Conventional Margin-Contouring

Several visual scoring methods are currently used to assess progression of rheumatoid arthritis (RA) on radiography. However, they are limited by its subjectivity and insufficient sensitivity. We have developed an original measurement system which uses a technique called phase-only correlation (POC). The purpose of this study is to validate the system by using a phantom simulating the joint of RA patients.A micrometer measurement apparatus that can adjust arbitrary joint space width (JSW) in a phantom joint was developed to define true JSW. The phantom was scanned with radiography, 320 multi detector CT (MDCT), high-resolution peripheral quantitative CT (HR-pQCT), cone beam CT (CBCT), and tomosynthesis. The width was adjusted to the average size of a women's metacarpophalangeal joint, from 1.2 to 2.2 mm with increments of 0.1 mm and 0.01 mm. Radiographical images were analyzed by the POC-based system and manual method, and images from various tomographical modalities were measured via the automatic margin detection method. Correlation coefficients between true JSW difference and measured JSW difference were all strong at 0.1 mm intervals with radiography (POC-based system and manual method), CBCT, 320MDCT, HR-pQCT, and tomosynthesis. At 0.01 mm intervals, radiography (POC-based system), 320MDCT, and HR-pQCT had strong correlations, while radiography (manual method) and CBCT had low correlations, and tomosynthesis had no statistically significant correlation. The smallest detectable changes for radiography (POC-based system), radiography (manual method), 320MDCT, HR-pQCT, CBCT, and tomosynthesis were 0.020 mm, 0.041 mm, 0.076 mm, 0.077 mm, 0.057 mm, and 0.087 mm, respectively. We conclude that radiography analyzed with the POC-based system might sensitively detect minute joint space changes of the finger joint.

Intratympanic application of triamcinolone in sudden hearing loss-radiologic anatomy in cone beam CT and its' correlation to clinical outcome

PURPOSE

To evaluate temporal bone cone-beam CT in patients with idiopathic sudden sensorineural hearing loss (ISSNHL) being treated with primary and secondary intratympanic (IT) triamcinolone and to possibly correlate these results to the clinical outcome.

METHODS

Retrospective analysis of patients treated with IT triamcinolone for ISSNHL at our department in 2018. Pre- and post-therapeutic audiologic examinations included four-tone average (FTA) at 0.5, 1, 2 and 3 kHz. Using a clinical questionnaire, pre-therapeutic CBCT scans were re-evaluated looking at items, which might interfere with adequate drug diffusion into the inner ear (e.g. bony overhangs or secondary membranes at the round or oval window).

RESULTS

Thirty-one patients were included. Twenty-four (77%; group A) had experienced ineffective systemic steroid therapy before and seven (23%; group B) received primary IT injections. Four group A-patients (21%) and two group B-patients (33%) showed a post-therapeutic FTA improvement of more than 15 dB HL. Bony overhangs at the round window niche (RWN) were present in seven cases (26%), a secondary membrane at the RWN in four (15%) and soft tissue in eight (30%) cases, respectively.

CONCLUSION

Most patients present radiological findings in CBCT imaging, which might interfere with drug diffusion through the RW membrane. Interestingly, soft or bony tissue obstructing the RWN or the OWN was found in 50% of patients, who showed improvement of hearing. We conclude that radiologic 'tiny' findings are either clinically irrelevant or improvement in hearing is independent from intratympanic drug delivery.

[Overview of modern methods for the diagnosis of exudative otitis media]

Modern methods for diagnosis of exudative otitis media (EOM) have great potential, however, the problem of diagnosis of EOM is still relevant. The article describes the methods of modern diagnostics that are widely used in the daily practice of an otolaryngologist. The basic principles, advantages and disadvantages of generally accepted diagnostic methods for EOM are presented. The method of optical coherence tomography (OCT) is described as a method of studying biological tissues, which is used in many fields of medicine. Information is provided on the possibilities of OCT in the diagnosis of diseases of the ENT organs and, in particular, of the middle ear. The results of studies of the tympanic cavity structures in various inflammatory conditions, the possibilities of intrasurgery use of OCT, as well as the possibilities and perspectives of introducing OCT into the practice of an otorhinolaryngologist in the diagnosis of exudative otitis media are described.

Ultrahigh-resolution CT scan of the temporal bone

OBJECTIVE

Ultrahigh-resolution CT (U-HRCT) provides better spatial resolution than conventional multi-detector row CT (ConvCT) and could be expected to identify microstructures with its 0.25-mm collimation, 1792 channels and 160 detector rows, 0.4 × 0.5 mm focus size, and a 1024 matrix. The aim of the study was to evaluate key anatomic structures in temporal bone using U-HRCT comparing it to ConvCT.

MATERIALS AND METHODS

A total of 30 patients (14 males and 16 females; age range, 8-82 years; median 49 years) underwent both U-HRCT and ConvCT. All CT images were obtained with 0.5 mm section thickness and a 512 × 512 matrix, and field of view of 80 mm. Transverse scans were acquired in a plane parallel to the orbitomeatal plane in the helical mode with 120 kV. Images of the 30 temporal bones of unaffected side were reviewed by two independent neuroradiologists who rated the visibility of key anatomic structures for both U-HRCT and ConvCT. The ratings between U-HRCT and ConvCT were compared using Wilcoxon matched-pairs signed rank test. The interobserver agreement on the rating of stapedius tendon was evaluated using weighted κ statistics.

RESULTS

Excellent interobserver agreement was shown for U-HRCT (κ = 0.920), whereas good agreement was obtained for ConvCT (κ = 0.733). According to both observers, stapedius tendon was more clearly visualized using U-HRCT than ConvCT (p < 0.0001). All other anatomic structures were well visualized using both CT scanners.

CONCLUSION

The anatomy of temporal bone is more conspicuous on U-HRCT than on ConvCT because of its ultra-high-resolution detector. U-HRCT may provide beneficial information for determining surgical indication or procedures.

An Investigation of the Morphology of the Petrotympanic Fissure Using Cone-Beam Computed Tomography

Objectives

The purpose of the present study was: a) to examine the visibility and morphology of the petrotympanic fissure on cone-beam computed tomography images, and b) to investigate whether the petrotympanic fissure morphology is significantly affected by gender and age, or not.

Material and Methods

Using Newtom VGi (QR Verona, Italy), 106 cone-beam computed tomography examinations (212 temporomandibular joint areas) of both genders were retrospectively and randomly selected. Two observers examined the images and subsequently classified by consensus the petrotympanic fissure morphology into the following three types: type 1 - widely open; type 2 - narrow middle; type 3 - very narrow/closed.

Results

The petrotympanic fissure morphology was assessed as type 1, type 2, and type 3 in 85 (40.1%), 72 (34.0%), and 55 (25.9%) cases, respectively. No significant difference was found between left and right petrotympanic fissure morphology (Kappa = 0.37; P < 0.001). Furthermore, no significant difference was found between genders, specifically P = 0.264 and P = 0.211 for the right and left petrotympanic fissure morphology, respectively. However, the ordinal logistic regression analysis showed that males tend to have narrower petrotympanic fissures, in particular OR = 1.58 for right and OR = 1.5 for left petrotympanic fissure.

Conclusions

The current study lends support to the conclusion that an enhanced multi-planar cone-beam computed tomography yields a clear depiction of the petrotympanic fissure's morphological characteristics. We have found that the morphology is neither gender nor age-related.

Additive value of "otosclerosis-weighted" images for the CT diagnosis of fenestral otosclerosis

Background Otosclerotic foci are usually seen as minute low-density lesions and this may be attributed to relatively low sensitivity on visual assessment using computed tomography (CT). Otosclerotic foci can be detected by using the accurate region of interest (ROI) setting, while small ROI settings by less-experienced radiologists may result in false negative findings. Purpose To evaluate the diagnostic ability of our proposed method ("otosclerosis-weighted" imaging [OWI]), which is based on reversing the density, compared with conventional CT (CCT) imaging alone. Material and Methods Temporal bone CTs of consecutive patients with otosclerosis were analyzed. Gender- and age-matched control participants were also included. All CT images were obtained using a 64-detector row scanner. OWI was obtained by extracting the temporal bone region using the threshold technique and reversing the density (black to white). Four independent radiologists took part in two reading sessions. In the first session, the observers read only CCT imaging. In the second session, they read OWI along with the CCT imaging. Sensitivity was assessed for the four readers. Results Thirty temporal bones of 25 patients with otosclerosis (3 men, 22 women; mean age, 53.9 ± 9.0 years) and 30 temporal bones of 30 control participants (4 men, 26 women; mean age, 44.0 ± 16.2 years) were included. For all observers, reading with a combination of the two methods was associated with a higher sensitivity (63.3-80.0%) than with conventional CT images alone (30.0-60.0%; P < 0.05, each). Conclusion Application of our proposed method based on threshold value may help detect foci of fenestral otosclerosis.

Accuracy of biomarkers obtained from cone beam computed tomography in assessing the internal trabecular structure of the mandibular condyle

OBJECTIVE

The aim of this study was to validate the ability of cone beam computed tomography (CBCT) to measure condylar internal trabecular bone structure and bone texture parameters accurately.

STUDY DESIGN

Sixteen resected condyles of individuals undergoing temporomandibular joint replacement were collected and used as samples. These condyles were then radiographically imaged by using clinically oriented dental CBCT and research oriented micro-computed tomography (micro-CT). The CBCT scans were then compared with the gold standard micro-CT scans in terms of 21 bone imaging parameters. Descriptive histologic investigation of the specimens was also performed.

RESULTS

Significant correlations were found for several imaging parameters between the CBCT and micro-CT images, including trabecular thickness (r = 0.92), trabecular separation (r = 0.78), bone volume (r = 0.90), bone surface area (r = 0.79), and degree of anisotropy measurements (r = 0.77).

CONCLUSIONS

Measurements of trabecular thickness, trabecular separation, bone volume, bone surface area, and degree of anisotropy obtained from high-resolution dental CBCT images may be suitable bone imaging biomarkers that can be utilized clinically and in future research.

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.

Predicting Trabecular Bone Stiffness from Clinical Cone-Beam CT and HR-pQCT Data; an In Vitro Study Using Finite Element Analysis

Stiffness and shear moduli of human trabecular bone may be analyzed in vivo by finite element (FE) analysis from image data obtained by clinical imaging equipment such as high resolution peripheral quantitative computed tomography (HR-pQCT). In clinical practice today, this is done in the peripheral skeleton like the wrist and heel. In this cadaveric bone study, fourteen bone specimens from the wrist were imaged by two dental cone beam computed tomography (CBCT) devices and one HR-pQCT device as well as by dual energy X-ray absorptiometry (DXA). Histomorphometric measurements from micro-CT data were used as gold standard. The image processing was done with an in-house developed code based on the automated region growing (ARG) algorithm. Evaluation of how well stiffness (Young’s modulus E3) and minimum shear modulus from the 12, 13, or 23 could be predicted from the CBCT and HR-pQCT imaging data was studied and compared to FE analysis from the micro-CT imaging data. Strong correlations were found between the clinical machines and micro-CT regarding trabecular bone structure parameters, such as bone volume over total volume, trabecular thickness, trabecular number and trabecular nodes (varying from 0.79 to 0.96). The two CBCT devices as well as the HR-pQCT showed the ability to predict stiffness and shear, with adjusted R²-values between 0.78 and 0.92, based on data derived through our in-house developed code based on the ARG algorithm. These findings indicate that clinically used CBCT may be a feasible method for clinical studies of bone structure and mechanical properties in future osteoporosis research.

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.

Cone beam CT dose reduction in prostate radiotherapy using Likert scale methods

OBJECTIVE

To use a Likert scale method to optimize image quality (IQ) for cone beam CT (CBCT) soft-tissue matching for image-guided radiotherapy of the prostate.

METHODS

23 males with local/locally advanced prostate cancer had the CBCT IQ assessed using a 4-point Likert scale (4 = excellent, no artefacts; 3 = good, few artefacts; 2 = poor, just able to match; 1 = unsatisfactory, not able to match) at three levels of exposure. The lateral separations of the subjects were also measured. The Friedman test and Wilcoxon signed-rank tests were used to determine if the IQ was associated with the exposure level. We used the point-biserial correlation and a χ(2) test to investigate the relationship between the separation and IQ.

RESULTS

The Friedman test showed that the IQ was related to exposure (p = 2 × 10(-7)) and the Wilcoxon signed-rank test demonstrated that the IQ decreased as exposure decreased (all p-values <0.005). We did not find a correlation between the IQ and the separation (correlation coefficient 0.045), but for separations <35 cm, it was possible to use the lowest exposure parameters studied.

CONCLUSION

We can reduce exposure factors to 80% of those supplied with the system without hindering the matching process for all patients. For patients with lateral separations <35 cm, the exposure factors can be reduced further to 64% of the original values.

ADVANCES IN KNOWLEDGE

Likert scales are a useful tool for measuring IQ in the optimization of CBCT IQ for soft-tissue matching in radiotherapy image guidance applications.

The presence of calcifications along the course of internal carotid artery in Greek and Brazilian populations: a comparative and retrospective cone beam CT data analysis

OBJECTIVES

We aimed to retrospectively compare the prevalence of soft tissue calcifications (STCs) depicted incidentally along the extra- and intracranial course of the internal carotid artery (ICA) on cone beam computed tomography examinations in 2 different populations (Greeks and Brazilians).

METHODS

The cohort consisted of examinations of 232 Greeks and 174 Brazilians, for a total of 406 patients. The scans were evaluated for the presence of STCs along the course of the ICA, with data analyzed in each ethnic group according to gender and age criteria.

RESULTS

In total, 355 STCs were recorded; 78 (22.0% of all STCs) and 58 (16.3%) were extracranials, and 128 (36.1%) and 91 (25.6%) were intracranials for Greeks and Brazilians, respectively. The χ(2) test indicated no statistical differences between Greeks and Brazilians in the occurrence of STCs; however, their prevalence differed between genders in those populations. The presence of lesions, both extra- and intracranially, was found to increase with age (P < .05). The odds ratios were estimated at 2.23 (95% CI, 1.81-2.74) and 3.26 (95% CI, 2.56-4.16) for extracranial and intracranial lesions, respectively, with increasing age.

CONCLUSIONS

We found an equal distribution for both extra- and intracranial STCs among Greeks and Brazilians. The prevalence of lesions differed between genders within both populations. Aging was found to be a risk factor for STCs, as the odds ratio increased significantly.

Imaging innovations in temporal bone disorders

The development of new imaging techniques coupled with new treatment algorithms has created new possibilities in treating temporal bone diseases. This article provides an overview of recent imaging innovations that can be applied to temporal bone diseases. Topics covered include the role of magnetic resonance (MR) diffusion-weighted imaging in cholesteatomas and skull base epidermoids, whole-body molecular imaging in paragangliomas of the jugular foramen, and MR arterial spin labeling perfusion for dural arteriovenous fistulas and arteriovenous malformations.

Extra- and intra-cranial arterial calcifications in adults depicted as incidental findings on cone beam CT images

OBJECTIVE

The aim of this study was to evaluate, retrospectively, the gender- and age-related prevalence of incidentally found calcifications, depicted within the course of the extra- and intra-cranial portion of internal carotid artery (ICA), in cone beam computed tomography (CBCT) examinations in adults, and to assess their clinical significance.

MATERIALS AND METHODS

Out of a pull of 700 CBCT examinations a total of 484 CBCT scans of adult patients were finally selected according to a set of pre-defined criteria. These were evaluated for arterial calcifications presence within the ICAs course according to gender and age criteria.

RESULTS

In total, 492 calcifications were detected: 211 (42.88%) extra-cranial and 281 (57.11%) intra-cranial. Those were recorded in 150 scans (30.99%) and 161 scans (33.26%), respectively. Calcifications, with either extra- or intra-cranial allocation, were found more frequent in males than in females (all p-values < 0.05); also patients who presented with positive findings were older than those without findings (all p-values < 0.05). Furthermore, calcification presence with either extra- or intra-cranial allocation increases with age (all p-values < 0.05).

CONCLUSION

Significant calcification frequencies were found within the ICA's course, in CBCT scans. Moreover, an increased incidence of either extra- or intra-cranial presence of these depictions and its relation to age and gender was documented.

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.

Trabecular bone histomorphometric measurements and contrast-to-noise ratio in CBCT

OBJECTIVES

The aim of this study was to evaluate how imaging parameters at clinical dental CBCT affect the accuracy in quantifying trabecular bone structures, contrast-to-noise ratio (CNR) and radiation dose.

METHODS

15 radius samples were examined using CBCT (Accuitomo FPD; J. Morita Mfg., Kyoto, Japan). Nine imaging protocols were used, differing in current, voltage, rotation degree, voxel size, imaging area and rotation time. Radiation doses were measured using a kerma area product-meter. After segmentation, six bone structure parameters and CNRs were quantified. Micro-CT (μCT) images with an isotropic resolution of 20 μm were used as a gold standard.

RESULTS

Structure parameters obtained by CBCT were strongly correlated to those by μCT, with correlation coefficients >0.90 for all studied parameters. Bone volume and trabecular thickness were not affected by changes in imaging parameters. Increased tube current from 5 to 8 mA, decreased isotropic voxel size from 125 to 80 μm and decreased rotation angle from 360° to 180° affected correlations for trabecular termini negatively. Decreasing rotation degree also weakened correlations for trabecular separation and trabecular number at 80 μm voxel size. Changes in the rotation degree and tube current affected CNR significantly. The radiation dose varied between 269 and 1153 mGy cm(2).

CONCLUSIONS

Trabecular bone structure can be accurately quantified by clinical dental CBCT in vitro, and the obtained structure parameters are strongly related to those obtained by μCT. A fair CNR and strong correlations can be obtained with a low radiation dose, indicating the possibility for monitoring trabecular bone structure also in vivo.

Imaging for evaluation of cholesteatoma: current concepts and future directions

PURPOSE OF REVIEW

To examine the rationale and utility of imaging in patients with known or suspected cholesteatoma, with emphasis on high-resolution computed tomography (HRCT) and diffusion-weighted MRI (DW-MRI).

RECENT FINDINGS

The initial diagnosis of cholesteatoma is largely based on patient history and clinical findings. HRCT scan can be a useful adjunct to define the presence of pathologic soft tissue in the temporal bone, and the extent of bony erosion, and inform the otologic surgeon about expected findings at the time of surgery. Although MRI has not traditionally been used in the evaluation of cholesteatoma given its poor resolution of bone anatomy, recent advances in DW-MRI sequences allow for high sensitivity and specificity in identifying the presence of cholesteatoma. More specifically, non-echo-planar DW-MRI is superior in the detection of residual or recurrent cholesteatoma compared to delayed-contrast MRI and echo-planar DW-MRI.

SUMMARY

HRCT and DW-MRI offer complementary anatomic information that can be used effectively in the management of cholesteatoma. DW-MRI imaging has proven to be a reliable method for detecting residual or recurrent cholesteatomas down to 3 mm in size, and allows radiologic differentiation between cholesteatoma and other soft tissue. As more centers implement DW-MRI imaging for detecting residual or recurrent cholesteatoma, there will likely be less need for second-look surgery, thereby potentially decreasing associated morbidity and surgical costs.

Is electrode-modiolus distance a prognostic factor for hearing performances after cochlear implant surgery?

The aim of this study was to evaluate electrode array position in relation to cochlear anatomy and its influence on hearing performance in cochlear implantees. Twenty-two patients (25 ears) with Med-El cochlear implants were included in this retrospective study. A negative correlation was observed between electrode-modiolus distance (EMD) at the cochlear base and monosyllabic word discrimination 6 months after implantation. We found no correlation between EMD and hearing outcome at 12 months. The insertion depth/cochlear perimeter ratio appeared to negatively influence the EMD at the base. Indeed, deep insertions in small cochleae appeared to yield smaller EMD and better hearing performance. This observation supports the idea of preplanning the surgery by adapting the electrode array to the length of the available scala tympani.

An autopsy case of otogenic intracranial abscess and meningitis with Bezold's abscess: evaluation of inflammatory bone destruction by postmortem cone-beam CT

The deceased was an unidentified young male found unconscious on a walkway. On autopsy, outer and inner fistulae of the left temporal bone, subcutaneous abscess in the left side of the neck and head, and an intracranial abscess were noted. A portion of the left temporal bone was removed and scanned by cone-beam computed tomography (CT) (normally used for dentistry applications) to evaluate the lesion. The cone-beam CT image revealed roughening of the bone wall and hypolucency of the mastoid air cells, consistent with an inflammatory bone lesion. According to autopsy and imaging findings, the cause of death was diagnosed as intracranial abscess with Bezold's abscess secondary to left mastoiditis as a complication of otitis media. Although determining the histopathology of bone specimens is time-consuming and costly work, we believe that use of cone-beam CT for hard tissue specimens can be useful in forensic practice.

Cone beam breast CT with a high pitch (75 μm), thick (500 μm) scintillator CMOS flat panel detector: visibility of simulated microcalcifications

PURPOSE

To measure and investigate the improvement of microcalcification (MC) visibility in cone beam breast CT with a high pitch (75 μm), thick (500 μm) scintillator CMOS/CsI flat panel detector (Dexela 2923, Perkin Elmer).

METHODS

Aluminum wires and calcium carbonate grains of various sizes were embedded in a paraffin cylinder to simulate imaging of calcifications in a breast. Phantoms were imaged with a benchtop experimental cone beam CT system at various exposure levels. In addition to the Dexela detector, a high pitch (50 μm), thin (150 μm) scintillator CMOS/CsI flat panel detector (C7921CA-09, Hamamatsu Corporation, Hamamatsu City, Japan) and a widely used low pitch (194 μm), thick (600 μm) scintillator aSi/CsI flat panel detector (PaxScan 4030CB, Varian Medical Systems) were also used in scanning for comparison. The images were independently reviewed by six readers (imaging physicists). The MC visibility was quantified as the fraction of visible MCs and measured as a function of the estimated mean glandular dose (MGD) level for various MC sizes and detectors. The modulation transfer functions (MTFs) and detective quantum efficiencies (DQEs) were also measured and compared for the three detectors used.

RESULTS

The authors have demonstrated that the use of a high pitch (75 μm) CMOS detector coupled with a thick (500 μm) CsI scintillator helped make the smaller 150-160, 160-180, and 180-200 μm MC groups more visible at MGDs up to 10.8, 9, and 10.8 mGy, respectively. It also made the larger 200-212 and 212-224 μm MC groups more visible at MGDs up to 7.2 mGy. No performance improvement was observed for 224-250 μm or larger size groups. With the higher spatial resolution of the Dexela detector based system, the apparent dimensions and shapes of MCs were more accurately rendered. The results show that with the aforementioned detector, a 73% visibility could be achieved in imaging 160-180 μm MCs as compared to 28% visibility achieved by the low pitch (194 μm) aSi/CsI flat panel detector. The measurements confirm that the Hamamatsu detector has the highest MTF, followed by the Dexel detector, and then the Varian detector. However, the Dexela detector, with its thick (500 μm) CsI scintillator and low noise level, has the highest DQE at all frequencies, followed by the Varian detector, and then the Hamamatsu detector. The findings on the MC visibility correlated well with the differences in MTFs, noise power spectra, and DQEs measured for these three detectors.

CONCLUSIONS

The authors have demonstrated that the use of the CMOS type Dexela detector with its high pitch (75 μm) and thick (500 μm) CsI scintillator could help improve the MC visibility. However, the improvement depended on the exposure level and the MC size. For imaging larger MCs or scanning at high exposure levels, there was little advantage in using the Dexela detector as compared to the aSi type Varian detector. These findings correlate well with the higher measured DQEs of the Dexela detector, especially at higher frequencies.

Dosimetry and image quality of four dental cone beam computed tomography scanners compared with multislice computed tomography scanners

OBJECTIVES

The aim of this study was to evaluate the radiation dose and image quality of four dental cone beam CT (CBCT) scanners, and to compare them with those of two multislice CT (MSCT) scanners.

METHODS

Tissue doses were measured using a tissue-equivalent anthropomorphic RANDO Head Phantom((R)) with thermoluminescence dosemeters (TLD). An RSVP Head Phantom(TM) with a specially designed cylindrical insert was used for comparison of image quality and absorbed dose. Image quality was evaluated in the form of contrast-to-noise ratio (CNR) and modulation transfer function (MTF).

RESULTS

Using standard imaging parameters, the effective doses varied between 14 microSv and 269 microSv (International Commission on Radiation Protection (ICRP) 1990) and 27 microSv and 674 microSv (ICRP 2008) with the CBCT scanners, and between 350 microSv and 742 microSv (ICRP 1990) and 685 microSv and 1410 microSv (ICRP 2008) with the MSCT scanners. The CNR of the CBCT and MSCT scanners were 8.2-18.8 and 13.6-20.7, respectively. Low-dose MSCT protocols provided CNRs comparable with those from CBCT scanners. The 10% MTF of the CBCT scanners varied between 0.1 mm(-1) and 0.8 mm(-1), and was 0.5 mm(-1) for all the MSCT protocols examined.

CONCLUSIONS

CBCT scanners provide adequate image quality for dentomaxillofacial examinations while delivering considerably smaller effective doses to the patient. Large variations in patient dose and image quality emphasize the importance of optimizing imaging parameters in both CBCT and MSCT examinations.

Intraoperative use of cone-beam computed tomography in a cadaveric ossified cochlea model

OBJECTIVES

To describe a cadaveric temporal bone model of labyrinthitis ossificans and investigate the utility of intraoperative cone-beam computed tomography (CBCT) in the facilitating cochlear implantation.

DESIGN

Cadaveric temporal bone study.

METHODS

Five cadaveric heads had cement introduced into the 10 cochleas. CBCT and a conventional CT scan were compared to assess the extent of cochlear obliteration. The cement was drilled-out (under CBCT guidance, if required) and cochlear implant electrode arrays (from 3 different manufacturers) inserted.

RESULTS

CBCT images demonstrated temporal bone anatomy and the extent of cochlear obliteration as clearly as conventional CT in all cases. Intraoperative CBCT guided drilling and facilitated electrode placement in two of five heads (3 of 10 ears). Streak-artifact from the electrodes of two devices partially obscured image clarity.

CONCLUSIONS

The obliterated cochlear model reproduced a disease-ossified cochlear both radiographically and surgically. CBCT is useful for intraoperative imaging to facilitate electrode array placement in the obliterated or congenitally abnormal cochlea.

Conebeam CT of the head and neck, part 2: clinical applications

SUMMARY

Conebeam x-ray CT (CBCT) is being increasingly used for point-of-service head and neck and dentomaxillofacial imaging. This technique provides relatively high isotropic spatial resolution of osseous structures with a reduced radiation dose compared with conventional CT scans. In this second installment in a 2-part review, the clinical applications in the dentomaxillofacial and head and neck regions will be explored, with particular emphasis on diagnostic imaging of the sinuses, temporal bone, and craniofacial structures. Several controversies surrounding the emergence of CBCT technology will also be addressed.

Cone beam computed tomography, a low-dose imaging technique in the postoperative assessment of cochlear implantation

BACKGROUND

Cone beam computed tomography (CBCT) has become an extremely useful technique for dentomaxillofacial imaging because it provides clear images of highly contrasted structures. Previous studies evaluating the applicability of this technique in otologic imaging were very encouraging but were only performed in vitro on temporal bone specimens. The intracochlear positioning of the individual electrodes after cochlear implantation by means of CBCT has not yet been shown in vivo.

OBJECTIVE

We describe a protocol for in vivo postoperative imaging of cochlear implants by CBCT. Moreover, the effective dose was measured and compared with the effective dose used on 4- and 16-slice multislice computed tomography (MSCT) by using a RANDO-phantom.

MAIN OUTCOME MEASURE

Developing a protocol for in vivo postoperative imaging of cochlear implants by CBCT.

RESULTS

CBCT provides high-resolution and almost artifact-free multiplanar reconstruction images allowing assessment of the precise intracochlear position of the electrode and visualization of each of the individual contacts. The calculated effective dose of the used CBCT and MSCT acquisitions is 80 musv for the CBCT, 3,600 musv for the 16-slice computed tomography, and 4,800 musv for the 4-slice computed tomography.

CONCLUSION

These preliminary results suggests that, for in vivo postoperative evaluation of cochlear implants, CBCT can provide at least the same information as conventional radiography, digital radiograph, and MSCT but in a more comfortable and a much more safer way.

Conebeam CT of the head and neck, part 1: physical principles

Conebeam x-ray CT (CBCT) is a developing imaging technique designed to provide relatively low-dose high-spatial-resolution visualization of high-contrast structures in the head and neck and other anatomic areas. This first installment in a 2-part review will address the physical principles underlying CBCT imaging as it is used in dedicated head and neck scanners. Concepts related to CBCT acquisition geometry, flat panel detection, and image quality will be explored in detail. Particular emphasis will be placed on technical limitations to low-contrast detectability and radiation dose. Proposed methods of x-ray scatter reduction will also be discussed.

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.