Cone beam CT: non-dental applications.

Initially cone beam CT was almost exclusively used to perform dental radiology. However, the first generation CBCT systems were later increasingly used to study sinuses, facial and nose fractures, temporomandibular joints etc. 3D-cephalometric head and neck studies became possible once CBCT systems were available that allowed scanning of the complete head. For this purpose a double rotation technique with stitching of the resulting two data sets was needed. CBCT systems on which the rotation could be stopped were needed to perform dynamic swallow or pharyngography studies. The advent of more powerful high-end CBCT systems led the way to temporal bone and skull base imaging. Finally, high-end "supine" CBCT systems using a "gantry" made small joint musculoskeletal imaging possible. These non-dental CBCT studies gradually replaced conventional X-rays and CT/MDCT studies because they allowed imaging with higher resolution, lower radiation dose and less metal artifacts. In this paper the most important non-dental CBCT indications will be discussed.

Jugular bulb diverticulum dehiscence towards the vestibular aqueduct in a patient with otosclerosis.

OBJECTIVES: To demonstrate the need for computed tomography imaging of the temporal bone before considering revision stapes surgery in patients with recurrent or residual conductive hearing loss. CASE REPORT: We report the case of a high-riding jugular bulb with an associated jugular bulb diverticulum, which was dehiscent towards the vestibular aqueduct, in a patient with confirmed otosclerosis who did not experience hearing improvement after stapedotomy. CONCLUSION: This case demonstrates the usefulness of temporal bone computed tomography in the evaluation of patients with otosclerosis in whom stapedotomy has not improved hearing. In such patients, revision surgery to address residual hearing loss would eventually prove unnecessary and avoidable.

[Sudden onset vertigo: imaging work-up]. / Exploration radiologique d'un vertige aigu.

Vertigo and dysequilibrium are a frequent cause of medical consultation. Clinical evaluation is essential. Some cases of vertigo are diagnosed clinically while others require imaging, sometimes emergently (suspected stroke). MRI is the imaging modality of choice to assess the labyrinth (labyrinthitis? labyrinthine hemorrhage?), internal auditory canal (vestibular schwannoma? other tumor?…) and brain parenchyma including all structures of the auditory pathways: vestibular nuclei, vestibulocerebellar tract, tracts involved with ocular motricity, vestibular cortex… Multiple central etiologies exist: stroke, multiple sclerosis, tumor… However, some etiologies are best depicted with CT, especially lesions of the labyrinth: cholesteatoma, trauma, suspected dehiscence of the superior semicircular canal, suspected labyrinthine fistula… Finally, imaging may be negative (Benign Paroxysmal Positional Vertigo, Meniere's disease, vestibular neuritis, migraine…), merely reducing the differential diagnosis.

Diffusion-weighted magnetic resonance imaging of the temporal bone.

This paper summarizes the value of diffusion-weighted magnetic resonance imaging in the evaluation of temporal bone pathology. It highlights the use of different types of diffusion-weighted magnetic resonance imaging in the different types of cholesteatoma, prior to first stage surgery and prior to second look surgery. The value of diffusion-weighted magnetic resonance imaging in the evaluation of pathology of the apex of the petrous bone and the cerebellopontine angle is also discussed.

[Diffusion-weighted MR imaging of the head and neck]. / Les applications de la diffusion en imagerie: tête et cou.

Diffusion weighted MR imaging is increasingly being used for the imaging of head and neck pathology. This imaging technique now replaces CT and conventional MR imaging for the initial diagnosis of cholesteatoma and detection of recurrent disease. Diffusion weighted imaging has also proven to be valuable for additional head and neck pathologies and currently has three main indications: detection and characterization of tumors, regional tumor staging, and prediction of tumor response to treatment and follow-up. In the recent months, several publications have discussed the use of diffusion weighted imaging for head and neck pathology and this technique has become virtually indispensable for the MR imaging evaluation of the head and neck.

Long-term follow up after bony mastoid and epitympanic obliteration: radiological findings.

OBJECTIVE: The canal wall up bony obliteration technique lowers the incidence of recurrent cholesteatoma, but carries the potential risk of obliterating residual cholesteatoma. The objective of this study was to report long-term follow-up radiological findings after performing a canal wall up bony obliteration technique procedure, in order to detect residual and/or recurrent cholesteatoma. PATIENTS: Fifty-one patients presenting with a cholesteatoma or a troublesome cavity were operated upon using the canal wall up bony obliteration technique, and were evaluated by follow-up imaging a mean of 76.4 months post-operatively (range, 53.8-113.6 months). INTERVENTION: All patients were evaluated with high resolution computed tomography and magnetic resonance imaging (including delayed contrast, T1-weighted imaging and non-echo-planar, diffusion-weighted imaging). RESULTS: Imaging revealed the presence of one residual, one recurrent and one congenital petrosal apex cholesteatoma. On high resolution computed tomography, completely obliterated mastoid filled with bone was observed in 74.5 per cent (38/51) of patients, and an aerated middle-ear cavity in 64.7 per cent (33/51). High resolution computed tomography clearly detected any associated soft tissue present in the middle-ear cavity (18/51) and in the obliterated mastoids (13/51), but could not characterise this tissue. Non-echo-planar, diffusion-weighted magnetic resonance imaging clearly identified all three cholesteatomas, and differentiated them from other associated soft tissues. No cholesteatoma was found within the obliterated mastoids. CONCLUSION: Long-term follow up indicated that the canal wall up bony obliteration technique is a safe method with which to treat primary and recurrent cholesteatoma and to reconstruct unstable cavities. Soft tissue was found quite often in the middle ear and obliterated mastoids. High resolution computed tomography identified its presence but could not further characterise it. However, non-echo-planar, diffusion-weighted magnetic resonance imaging succeeded in differentiating soft tissues, enabling detection of residual or recurrent cholesteatoma after a canal wall up bony obliteration technique procedure.

Magnetic resonance imaging of cholesteatoma: an update.

OBJECTIVE: To report on the value and limitations of new MRI techniques in pre- and post-operative MRI of cholesteatoma. The current value of magnetic resonance imaging (MRI) in diagnosing congenital, acquired, and post-operative recurrent or residual cholesteatoma is described. METHODOLOGY AND RESULTS: High resolution computed tomography (HRCT) is still considered the imaging modality of choice for detecting acquired or congenital middle ear cholesteatoma. However, MRI may provide additional information on the delineation and extension of cholesteatoma and on potential complications. Detecting post-operative residual or recurrent cholesteatoma with HRCT was shown to be inaccurate due to the technique's low sensitivity and specificity. CONCLUSIONS: Recently, improvements in MRI techniques have led to a more accurate diagnoses of cholesteatoma using delayed contrast enhanced T1-weighted imaging and diffusion-weighted imaging.

Imaging of intralabyrinthine schwannomas: a retrospective study of 52 cases with emphasis on lesion growth.

BACKGROUND AND PURPOSE: Only a few case reports and small series of intralabyrinthine schwannomas (ILSs) have been reported. The purpose of this study was to assess prevalence, MR characteristics, location, clinical management, and growth potential/patterns of ILSs in the largest series reported. MATERIALS AND METHODS: Lesion localization, MR characteristics, lesion growth, and clinical management were reviewed in 52 patients diagnosed with an ILS between February 1991 and August 2007 in 2 referral centers. The number of ILSs and vestibulocochlear schwannomas in the cerebellopontine angle/internal auditory canal was compared to assess the prevalence. RESULTS: ILSs most frequently originate intracochlearly, are hyperintense on unenhanced T1-weighted images, enhance strongly after gadolinium administration, and are sharply circumscribed and hypointense on thin heavily T2-weighted 3D images. The scala tympani is more frequently or more extensively involved than the scala vestibuli. Follow-up MR imaging, available in 27 patients, showed growth in 59% of subjects. Growth was seen from the scala tympani into the scala vestibuli and from the scala vestibuli to the saccule and vice versa. Twelve lesions were resected, and the diagnosis of ILS histopathologically confirmed. CONCLUSION: ILSs can account for up to 10% of all vestibulocochlear schwannomas in centers specializing in temporal bone imaging, grow in more than 50%, and are most frequently found intracochlearly, often anteriorly between the basal and second turn. Cochlear ILSs most often originate in the scala tympani and only later grow into the scala vestibuli. Growth can occur from the cochlea into the vestibule or vice versa through the anatomic open connection between the perilymphatic spaces in the scala vestibuli and around the saccule.

Imaging of the opacified middle ear.

Middle ear opacification on imaging studies performed in a non-traumatic setting mostly reflects chronic inflammatory/infectious disease. In some of these patients an underlying cholesteatoma will be found. High-resolution computed tomography examinations and magnetic resonance imaging are often used in the work-out of the disease. High-resolution computed tomography of the opacified middle ear serves to describe the status of the ossicular chain, and its suspensory apparatus, as well as the status of the tympanic and mastoid wall. When ossicular erosions are visualized, the probability of a present cholesteatoma is about 90%. Whereas high-resolution computed tomography is not able to differentiate cholesteatoma from other types of opacification, magnetic resonance imaging is. The combined use of delayed post-Gd T1-weighted images and non-EPI based DWI seems to be the actual best option on this matter.

Cervical ectopic thymus presenting as a painless neck mass in a child.

Ectopic cervical thymus is an uncommon entity to be considered in the differential diagnosis of neck masses in infants and children. The sonographic appearance of a hyporeflective mass with characteristic internal linear hyperreflections situated along the path of the thymopharyngeal duct should suggest diagnosis. On MRI, signal intensities differ significantly from other more common neck mass lesions in children such as a branchiogenic cyst, hemangioma and lymphangioma. Diagnosis can be confirmed by performing a sonographically guided thru-cut biopsy.

Arachnoid granulations of the posterior temporal bone wall: imaging appearance and differential diagnosis.

Arachnoid granulations are rarely seen on high-resolution CT (HRCT) at the posterior temporal bone wall, where they appear as erosions, without bone spicules and often with a lobulated surface. Differential diagnosis includes endolymphatic sac tumor, paraganglioma, chordoma, and chondromatous and metastatic tumors. MR imaging can confirm the diagnosis because arachnoid granulations behave like CSF without gadolinium enhancement. This report aims to illustrate the appearance and differentiation of temporal bone arachnoid granulations on HRCT and MR imaging.

Single-shot, turbo spin-echo, diffusion-weighted imaging versus spin-echo-planar, diffusion-weighted imaging in the detection of acquired middle ear cholesteatoma.

Diagnosis of acquired middle ear cholesteatoma on MR imaging is mostly done on late postgadolinium T1-weighted MR images and/or echo-planar (EPI) diffusion-weighted (DWI) MR images. We describe the appearance of a case of a complicated attical middle ear cholesteatoma on single-shot (SS) turbo spin-echo (TSE) DWI compared with EPI-DWI. This case suggests a higher reliability of SS TSE-DWI in the diagnosis of acquired middle ear cholesteatoma.

Tumors and tumor-like lesions of the jaw: radiolucent lesions.

Radiolucent lesions within the jaws represent a whole variety of lesions. Generally, they can be classified into two categories. The first category comprises well circumscribed lesions, either unilocular, multilobular or multilocular. They may be further subdivided into odontogenic or nonodontogenic lesions. The key feature that distinguishes these two subgroups is the relationship with the underlying dentition. Poorly circumscribed radiolucent lesions are the second category and consist of acute infectious disease and primary or metastatic malignancies. Although many of these lesions may present with non-specific imaging characteristics, careful analysis of a combination of imaging parameters may suggest a presumptive diagnosis. This article discusses the imaging features on different imaging techniques that may be useful in the characterization of these lesions.

Tumors and tumor-like lesions of the jaw mixed and radiopaque lesions.

Radiopaque lesions and lesions of mixed radioopacity are far less frequent than their radiolucent counterparts. Included in this spectrum are infectious and metastatic disease, inherited and developmental disorders and rare tumoral lesions. This article deals with the imaging features that may assist in the (differential) diagnosis of these lesions. in many instances, the radiological characterization is typical (osteoma, enostoma, fibrous dysplasia, Paget disease...), obviating the need for further invasive histological confirmation. Other lesions may share overlapping clinical, radiological and pathological features. In these cases, correlation of histopathological diagnosis with clinical findings and imaging features is of utmost importance for a correct diagnosis.