Non-gaussian analysis of diffusion-weighted MR imaging in head and neck squamous cell carcinoma: A feasibility study.

BACKGROUND AND PURPOSE: Water in biological structures often displays non-Gaussian diffusion behavior. The objective of this study was to test the feasibility of non-Gaussian fitting by using the kurtosis model of the signal intensity decay curves obtained from DWI by using an extended range of b-values in studies of phantoms and HNSCC. MATERIALS AND METHODS: Seventeen patients with HNSCC underwent DWI by using 6 b-factors (0, 50-1500 s/mm(2)) at 1.5T. Monoexponential (yielding ADC(mono)) and non-Gaussian kurtosis (yielding apparent diffusion coefficient D(app) and apparent kurtosis coefficient K(app)) fits were performed on a voxel-by-voxel basis in selected regions of interest (primary tumors, metastatic lymph nodes, and spinal cord). DWI studies were also performed on phantoms containing either water or homogenized asparagus. To determine whether the kurtosis model provided a significantly better fit than did the monoexponential model, an F test was performed. Spearman correlation coefficients were calculated to assess correlations between K(app) and D(app). RESULTS: The kurtosis model fit the experimental data points significantly better than did the monoexponential model (P < .05). D(app) was approximately twice the value of ADC(mono) (eg, in neck nodal metastases D(app) was 1.54 and ADC(mono) was 0.84). K(app) showed a weak Spearman correlation with D(app) in a homogenized asparagus phantom and for 44% of tumor lesions. CONCLUSIONS: The use of kurtosis modeling to fit DWI data acquired by using an extended b-value range in HNSCC is feasible and yields a significantly better fit of the data than does monoexponential modeling. It also provides an additional parameter, K(app), potentially with added value.

Extraosseous chordoma of the nasopharynx.

BACKGROUND AND PURPOSE: Chordoma is a relatively rare tumor of the skull base and sacrum thought to originate from embryonic remnants of the notochord. Chordomas arising from the skull base/clivus are typically locally aggressive with lytic bone destruction. When chordomas occur in an extraosseous location, they may mimic other lesions of the nasopharynx. We present 5 cases of primarily extraosseous chordoma involving the nasopharynx in an effort to improve the preoperative diagnosis of this rare tumor. In addition, we review regional notochordal embryology to explain this variant tumor location. MATERIALS AND METHODS: We reviewed the clinical and imaging data of 5 pathologically proved cases of extraosseous chordoma of the nasopharynx seen or reviewed at our institution during the last decade. All cases had both CT and MR imaging. The study had institutional review board approval. RESULTS: The primary clinical complaint in the 5 patients with extraosseous nasopharyngeal chordoma was nasal obstruction. The extraosseous chordomas were centered in the nasopharynx. Bony lytic changes along the anterior surface of the clivus were seen on 5 of 5 CT studies. A midline sinus tract was seen in 3 of 5 patients. MR imaging showed heterogeneous hyperintense T2 signal intensity (5/5). CONCLUSIONS: Extraosseous nasopharyngeal chordoma is a rare but important lesion to be considered in the differential diagnosis of nasopharyngeal masses. When a midline nasopharyngeal mass is found with an associated clival sinus tract, extraosseous chordoma moves to the top of the differential diagnosis list. Complete removal of the soft-tissue tumor and the clival sinus tract is the treatment of choice in such cases.

Normal and opacified middle ears: CT appearance of the stapes and incudostapedial joint.

PURPOSE: To establish the computed tomographic (CT) visibility of the incudostapedial joint and of the stapes superstructure in normal and opacified middle ears. MATERIALS AND METHODS: Two independent observers reviewed CT studies with 1-mm section thickness of the temporal bone in 75 normal ears and in 33 opacified middle ears (13 of which had definitive proof of disease) to establish the rate of visualization of the stapes and incudostapedial joint. RESULTS: In normal ears, both the stapes crura and the continuity between the incus and stapes were seen in almost 100% of cases, whereas the actual incudostapedial joint was identified in 86% (86 observations) and 67% (67 observations) of cases in the axial and coronal planes, respectively. The position of the incudostapedial joint was below footplate level on the axial images and mostly at or anterior to the midportion of the foot-plate on the coronal images. In 13 clinically confirmed diseased middle ears, the status of the stapes superstructure in all cases and that of the incus in 11 cases was correctly predicted with CT. CONCLUSION: It is now possible to visualize routinely the incudostapedial joint and stapes superstructure at CT. Absence of these structures in an opacified middle ear strongly indicates abnormality.

CT of the normal suspensory ligaments of the ossicles in the middle ear.

PURPOSE: To establish the range of normal variation in the CT appearance of the middle ear ligaments and the stapedius tendon as an aid in detecting abnormal changes in these structures. METHODS: CT scans of the temporal bone in 75 normal middle ears, obtained with 1-mm-thick sections, were reviewed by two observers, who rated the visibility of the structures of interest on a scale of 1 to 5. RESULTS: The anterior, superior, and lateral malleal ligaments and the medial and lateral parts of the posterior incudal ligament were seen in 68%, 46%, 95%, 26%, and 34% of the ears, respectively. The stapedius tendon was seen in 27% of the cases. When visible, the ligaments were judged to be complete in 90% to 100% of the ears and the stapedius tendon was complete in 65% of cases. Their width varied considerably. Interobserver variability was high for most observations. CONCLUSION: CT scans are more likely to show the malleal than the incudal ligaments. Although the interobserver agreement was statistically significant for most study parameters, the percentage of agreement above that expected by chance was low. When seen, the ligaments usually appeared complete. Understanding the normal range of appearance may help identify abnormalities of the ligaments and tendons of the middle ear.