False-positive positron-emission tomography-CT of a Teflon granuloma in the parapharyngeal space occurring after treatment for a patulous eustachian tube.

This report presents a 55-year-old woman who underwent 2 Teflon injections in 1971 for a patulous eustachian tube. The patient returned in 2006 with a bloody left otorrhea. A positron-emission tomography-CT scan demonstrated a 2-cm hypermetabolic parapharyngeal mass, initially interpreted as a skull base tumor. Repeat neck CT confirmed a 2-cm hyperattenuated left parapharyngeal granulomatous mass. This is the first reported case of a Teflon granuloma presenting as a false-positive parapharyngeal mass.

Narrow, duplicated internal auditory canal.

A narrow internal auditory canal (IAC) constitutes a relative contraindication to cochlear implantation because it is associated with aplasia or hypoplasia of the vestibulocochlear nerve or its cochlear branch. We report an unusual case of a narrow, duplicated IAC, divided by a bony septum into a superior relatively large portion and an inferior stenotic portion, in which we could identify only the facial nerve. This case adds support to the association between a narrow IAC and aplasia or hypoplasia of the vestibulocochlear nerve. The normal facial nerve argues against the hypothesis that the narrow IAC is the result of a primary bony defect which inhibits the growth of the vestibulocochlear nerve.

Diagnosis of endolymphatic hydrops in vivo with magnetic resonance imaging.

HYPOTHESIS: High-resolution magnetic resonance imaging (MRI) at 1.5 T preferentially enhances the perilymph over endolymph after administration of contrast with gadodiamide, which allows for differentiation of the membranous labyrinth. Furthermore, this imaging allows for the detection of endolymphatic hydrops. BACKGROUND: Endolymphatic hydrops is believed to be associated with a number of ear diseases, including Ménière's disease. Although the pathologic changes of overaccumulation of endolymph in the inner ear are obvious on postmortem histologic examination of the temporal bone, they have yet to be observed in a living organism. Previous attempts to visualize this condition with high-resolution contrast-enhanced computed tomographic imaging and MRI have been unsuccessful. METHODS: Healthy pigmented guinea pigs underwent a unilateral surgical ablation of the endolymphatic sac to create endolymphatic hydrops in the ear. High-resolution temporal bone imaging was performed by use of a 1.5-T MRI system. Two-dimensional images were acquired by a spin-echo technique with and without contrast enhancement by gadodiamide. RESULTS: T1-weighted gadodiamide contrast-enhanced MRI of the midmodiolar level of the cochlea demonstrated that the perilymph appeared to be preferentially enhanced relative to the endolymph, resulting in a clear distinction between the scalae of the inner ear. The contrast-enhanced T1-weighted MRI of the midmodiolar level of the hydropic cochlea demonstrated a significantly enlarged scala media in comparison with the normal cochlea in the same animal. CONCLUSION: The demonstration of endolymphatic hydrops has been possible for the first time in vivo by the use of a standard 1.5-T MRI system. This research has important clinical implications: Specifically, this technique may allow for the noninvasive diagnosis of Ménière's disease.

Localized two-dimensional shift correlated MR spectroscopy of human brain.

A two-dimensional (2D) chemical shift correlated MR spectroscopic (COSY) sequence integrated into a new volume localization technique (90 degrees -180 degrees -90 degrees ) is proposed for whole-body MR spectroscopy (MRS). Using the product operator formalism, a theoretical calculation of the volume localization as well as the coherence transfer efficiencies in 2D MRS is presented. Phantom model solutions were used to test and optimize the efficiency of the proposed sequence. A combination of different MRI transmit/receive RF coils was used: a head MRI coil and a 3" surface coil receive combined with a body coil transmit. The J cross-peaks due to N-acetyl aspartate (NAA), glutamate/glutamine (Glx), myo-inositol (mI), creatine (Cr), choline (Ch), aspartate (Asp), gamma-aminobutyrate (GABA), taurine (Tau), glutathione (GSH), threonine (Thr), and macromolecules (MM) were identified. The cross-peak intensities excited by the proposed 2D sequence were asymmetric with respect to the diagonal peaks. Localized COSY (L-COSY) spectra of cerebral prefrontal and occipital gray/white matter regions in 15 healthy controls are presented. Magn Reson Med 46:58-67, 2001.

Magnetic resonance imaging--guided fine-needle aspiration biopsies of retropharyngeal lesions.

OBJECTIVE: The retropharyngeal space is a deep neck space susceptible to a host of disease processes. Surgical access to this space is technically difficult and associated with potential morbidity. An image-guided fine-needle aspiration (FNA) biopsy, if proven accurate and safe, would be of great benefit as an alternative diagnostic approach to this space. This study reports on the use of magnetic resonance imaging (MRI)--guided FNA for diagnostic evaluation of retropharyngeal lesions. Technical details of needle systems, approach to this space, and reliability of this method are described. STUDY DESIGN: This is a prospective study of 14 patients with retropharyngeal lesions who underwent MRI-guided FNA biopsy at the University of California at Los Angeles Center for the Health Sciences between October 1989 and October 1998. METHODS: A 0.2-tesla open magnet was used to obtain magnetic resonance images of each retropharyngeal lesion. After standard skin preparation a coaxial needle system was used to reach and sample the lesion. In most instances, the specimen was immediately stained and examined by a cytopathologist for adequacy before removing the patient from the scanner. RESULTS: Eleven of 14 (78%) patients had diagnostic aspirations; only 2 of these 11 patients required additional surgical biopsy for more specific histological characterization of their lesions before definitive treatment recommendations were given. All aspiration procedures were well tolerated and without any complications. CONCLUSION: We have demonstrated that MRI-guided approach to the retropharynx is feasible, safe, and sensitive enough to obviate the need for open biopsies in a large percentage of patients.

Fenestration surgery for otosclerosis: CT findings of an old surgical procedure.

Numerous attempts to deal surgically with otosclerosis were made before the current method of stapedectomy with stapes prosthesis was established. We report a case with unique CT findings of a patient who underwent fenestration surgery for otosclerosis in the early 1940s. Recognition of this old surgical procedure on the imaging scans may avoid misdiagnosis of labyrinthine fistulae or middle and inner ear malformations.

MRI-guided needle localization in the head and neck using contemporaneous imaging in an open configuration system.

BACKGROUND: MRI-guided procedures have previously been limited by technical difficulties, including the need for MRI-compatible instruments, slow image acquisition time, and the closed nature of conventional MRI scanners. The development of open configuration MRI systems with in-room, contemporaneous imaging has greatly increased the potential for MRI-guided interventional procedures. We evaluate our clinical experience applying this technology to the head and neck. METHODS: An open design 0.2T magnet combined with an in-room monitor was used for 24 MRI-guided needle localization procedures in the head and neck. Success of the procedures was based on the ability to accurately position the instrument in the target region to allow biopsy or treatment. RESULTS: In all 24 cases placement of the instrument within the target tissue was successful. CONCLUSION: MRI-guided needle-localization procedures in an open design magnet with in-room, contemporaneous image monitoring offer advantages over previous conventional interventional MRI systems by allowing interactive guidance with near real-time imaging feedback. As a result, procedure time is reduced and accuracy of instrument positioning is increased.

Midline destructive lesions of the sinonasal tract: simplified terminology based on histopathologic criteria.

BACKGROUND AND PURPOSE: Destructive lesions of the sinonasal tract, lacking a discernible etiology and referred to as midline destructive disease, have been pathologically classified in accordance with a variety of confusing terms. Development of new pathologic concepts and immunohistochemical techniques has provided a fresh understanding of these lesions, and, as a result, they can be unified into two distinct pathologic groups: Wegener's granulomatosis and non-Hodgkin's T-cell lymphoma. METHODS: We retrospectively reviewed the imaging studies and pathologic specimens of seven patients with prior diagnoses included in the midline destructive disease group. The specimens were reviewed by an oral pathologist using currently accepted pathologic criteria and the newly available immunohistochemical markers CD20, CD45, and CD45RO. Lesions were classified as non-Hodgkin's T-cell lymphomas when positive for CD45 and CD45RO and negative for CD20, and as Wegener's granulomatosis in the presence of noncaseating multinucleated giant cell granulomas and necrotizing vasculitis. RESULTS: Three of the lesions were reclassified as Wegener's granulomatosis and four as T-cell lymphomas after applying these pathologic criteria. There were no distinguishing imaging findings between Wegener's granulomatosis and non-Hodgkin's T-cell lymphoma. CONCLUSION: The current pathologic classification for midline destructive disease should be incorporated into the radiologic lexicon and the use of terms from the old classification system, such as idiopathic midline granuloma and lethal midline granuloma, should be abandoned and no longer be used in radiologic reports.

Chondroid tumors of the larynx: computed tomography findings.

PURPOSE: Chondromas and chondrosarcomas of the larynx are rare cartilaginous tumors making up less than 1% of all laryngeal tumors. Patients typically present with symptoms of hoarseness, dysphagia, or dyspnea. The most common location in the larynx for these tumors is the cricoid cartilage. Radiographically, these lesions are typically hypodense, well-circumscribed masses containing mottled calcifications with smooth walls centered within the cartilage. MATERIALS AND METHODS: We present 6 cases of chondroid tumors of the larynx. RESULTS: One patient had a chondroma, 4 patients had low-grade chondrosarcomas, and 1 patient had an intermediate-grade chondrosarcoma. Two partial laryngeal resections and 4 total laryngectomies were performed. CONCLUSIONS: In most cases of chondroma or chondrosarcoma of the larynx, conservative surgery should be attempted, but total laryngectomy may be required for large or recurrent lesions.

MRI of thermally denatured blood: methemoglobin formation and relaxation effects.

Focal regions of T1-shortening have been observed in magnetic resonance imaging (MRI)-monitored thermal ablations of perfused tissues. The aims of this study were two-fold: to find evidence for heat-induced conversion of hemoglobin (Hb) to methemoglobin (mHb), and to investigate the effects of heat treatment of in-vitro blood components upon their MR relaxation times. Spectrophotometric studies were performed to confirm the heat-induced formation of methemoglobin. Preparations of whole and fractionated blood, previously submitted to elevated temperatures of 40 degrees C to 80 degrees C, were imaged and the relaxation times were calculated. Optical absorption spectra of samples containing free Hb, heated to 60 degrees C, showed increased light absorption at 630 nm, evident of mHb presence. Short T1 values in whole blood (1.13 s) and packed red blood cell (0.65 s) compartments, heated at 60 degrees C, compared to their baseline values (1.62 s and 0.83 s, respectively), were attributed to mHb formation. In relation to MRI-guided thermal interventions, these results suggest a possible explanation for observation of hyperintense regions on T1-weighted images.

MR-guided procedures using contemporaneous imaging frameless stereotaxis in an open-configuration system.

Frameless MR-guided procedures have had limited application using conventional closed magnets, due largely to the technical difficulties involved. As a result of in-room MR image-monitoring capabilities, new open-design magnets now allow frameless stereotaxis using contemporaneous imaging to guide more invasive procedures. We evaluate our clinical experience with this new technique. An open-design 0.2 T magnet (Siemens OPEN) combined with an in-room monitor was used for 33 frameless MR-guided procedures (aspiration cytology, biopsy, and/or treatment) in a variety of locations in the head, neck, spine, brain, pelvis, and abdomen. Success of the procedure was based on the ability to accurately position the instrument in the target region to allow biopsy and/or treatment. The open-design magnet allowed the physician to directly access the patient for frameless stereotaxis as the procedure was performed. The in-room monitor provided contemporaneous imaging feedback during the procedure for successful placement of the instrument in the target region. Twenty-eight biopsy and five treatment procedures were performed. In all cases the technique resulted in successful placement of the instrument within the target tissue to complete the procedure. MR-guided procedures using contemporaneous imaging frameless stereotaxis are possible in an open-design magnet with in-room image monitoring and offer exciting possibilities for further development.

Computer coregistration of positron emission tomography and magnetic resonance images in head and neck cancer.

PURPOSE: Early experience has shown that positron-emission tomography (PET) is a useful technique for the detection of occult squamous cell carcinoma of the head and neck. Although highly sensitive, PET lacks definition of anatomic detail and therefore does not localize pathology precisely. To circumvent this limitation, a computerized coregistration technique has been developed at the University of California-Los Angeles to correlate PET and magnetic resonance images (MRI). This method allows accurate, precise anatomic localization of areas of heightened glucose metabolism, including subclinical tumors. MATERIALS AND METHODS: The technique uses a coregistration computer program that precisely superimposes the PET scan with the corresponding MRI image. RESULTS: Two cases are presented in which PET-MRI coregistration was used to anatomically define the areas of heightened glucose metabolism. Large tumors were selected because the precision of the method can be verified. CONCLUSION: The coregistration technique is a valuable addition to PET imaging, particularly in its ability to anatomically localize PET findings. The most important application of this technique is to facilitate the biopsy of subclinical lesions identified on PET.

Imaging of nodal metastases in the head and neck.

Therapeutic outcome of head and neck cancer is influenced strongly by the presence of nodal metastases. Sensitivity and specificity of the physical examination for the diagnosis of nodal metastasis is unsatisfactory, resulting in both false negatives and false positives of 25 to 40%. Preoperative detection of nodal metastases therefore becomes one of the important goals of imaging studies of patients with head and neck cancer. Despite several advanced techniques and the wide clinical use of MR, MR has surprisingly added little to the diagnostic accuracy of contrast-enhanced CT. Although CT and MR allow detection of abnormally enlarged nodes or necrotic nodes, neither borderline-sized nodes without necrosis nor extracapsular spread are reliably differentiated from reactive or normal nodes in patients with head and neck cancer. Lack of definitive diagnostic methods of metastatic lymph nodes is a serious shortcoming in the preoperative workup for patients with head and neck cancer. To avoid missing small metastatic nodes, a large number of patients clinically staged as N0 have undergone elective neck dissection to exclude metastases. With development of more tissue-specific imaging techniques, patients can be better characterized according to the status of nodal disease so that an appropriate therapeutic protocol can be designed for an individual case.

Phase imaging on a .2-T MR scanner: application to temperature monitoring during ablation procedures.

Proton phase shift imaging methods with keyholing were developed to rapidly monitor temperature during MR-guided radiofrequency (RF) interventional procedures on a .2-T open configuration scanner. Temperature calibration was performed on thermally controlled gel phantom and ex vivo bovine liver samples. Keyholing methods were implemented for rapid imaging and tested both in simulation experiments and in the gel phantom. Phase drifts from extraneous sources were monitored and compensated for using reference phantoms. Sequence parameters TE, TR, and flip angle (FA) were optimized for maximum temperature sensitivity and minimum noise. Reduction of phase noise from coupling of the magnetic field to external perturbations using navigator-echo-based correction schemes were also investigated. The extraneous phase drifts from the magnet could be minimized by keeping the electromagnet on continuously. Navigator echo corrected keyholed FLASH sequences (TE = 30 msec, TR = 60 msec, FA = 40 degrees, 64 x 128 matrix) were used to monitor the RF lesioning process in gel phantoms yielding images every 4 seconds with a temperature sensitivity of .015 ppm/degree C. RF ablation in the bovine tissue was monitored using navigator-echo-corrected keyholed fast low angle shot (FLASH) sequences (TE = 30 msec, TR = 100 msec, FA = 40 degrees, 128 x 256 matrix) with a temporal resolution of 13 seconds and a temperature sensitivity of .007 ppm/degree C. The results indicate that monitoring of an RF ablation procedure by mapping temperature with sufficient temporal resolution is possible using phase images of FLASH sequences on a .2-T open scanner.