Assessment of Lymph Node Metastases by Contrast-Enhanced MR Imaging in a Head and Neck Cancer Model

OBJECTIVE: We wanted to investigate the accuracy of contrast-enhanced MR imaging for the detection of lymph node metastases in a head and neck cancer rabbit model. MATERIALS AND METHODS: The metastatic lymph node model we used was created by inoculating VX2 tumors into the auricles of six New Zealand White rabbits. T1-weighted MR images were obtained before and after injecting gadopentetate dimeglumine at three weeks after tumor cell inoculation. The sizes, signal intensity ratios (i.e., the postcontrast signal intensities of the affected nodes relative to the adjacent muscle) and the enhancement patterns of 36 regional lymph nodes (parotid and caudal mandibular nodes) were evaluated on MR images and then compared with the histopathologic findings. RESULTS: No statistical difference was found between the sizes of 12 metastatic (10.5+/-3.2 mm) and 24 hyperplastic (8.0+/-3.6 mm) lymph nodes (p > 0.05). On the contrast-enhanced T1-weighted MR images, nine metastatic and four hyperplastic lymph nodes had peripheral high and central low signal intensity, whereas three metastatic and 20 hyperplastic lymph nodes had homogeneous high signal intensity. Using a signal intensity ratio less than one as a diagnostic criterion for a metastatic lymph node, the sensitivity, specificity and positive and negative predictive values of the enhanced MR images were 75% (9/12), 83% (20/24), 69% (9/13) and 87% (20/23), respectively, with areas under receiver-operating-characteristic curve values of 0.81. CONCLUSION: This experimental study confirms that metastatic and hyperplastic lymph nodes can be differentiated using MR images on the basis of the contrast uptake patterns, but that they cannot be differentiated using any particular size criteria.

MR Imaging of Solitary Fibrous Tumors in the Head and Neck

OBJECTIVE: Solitary fibrous tumor (SFT) is a very rare tumor. The purpose of this study is to determine the MR imaging features of SFT in the intracranial and extracranial head and neck regions. MATERIALS AND METHODS: We retrospectively reviewed six MR images and two CT images of six histologically proven cases of SFT that occurred in four men and two women, and their ages ranged from 46 to 59 years. These imaging findings were correlated with the microscopic findings of their surgical specimens. RESULTS: Six SFTs arose in the meninges (the petrous ridge and the pituitary fossa), the parotid gland, the parapharyngeal space, the buccal space and the maxillary sinus. On the MR images, SFTs in the intracranial and extracranial head and neck regions were mostly isointense to the muscle on the T1-weighted images, they were hyperintense on the T2-weighted images and they all had intense enhancement. On the T1- and T2-weighted images, hypointense lines were observed within in five SFTs. On the CT images, the SFTs were hypodense to the muscle on the unenhanced images and they were heterogeneously enhanced on the contrast-enhanced images. An exceptional case of pituitary SFT was hypointense on the T2-weighted images and it was hyperdense on the unenhanced CT images, which correlated with the increased collagenous component and the cellular compactness. CONCLUSION: The imaging features of SFT are nonspecific; however, SFT should be included in the differential diagnosis of masses involving the intracranial and extracranial head and neck regions.

Inflammatory Pseudotumor of the Extraorbital Head and Neck: CT and MR Imaging Findings

PURPOSE: To determine the MR and CT imaging findings of inflammatory pseudotumor of the extraorbital head and neck. MATERIALS AND METHODS: We reviewed the MR (n=10) and CT (n=9) imaging studies of 11 patients with this condition (M:F=5:6, age range: 35-75 years), analysing each case in terms of location, occupying space, signal intensity, intracranial involvement, degree of contrast enhancement and adjacent bone change. Follow-up images were obtained in nine cases, and the response of each patient to steroid treatment was reviewed. RESULTS: Lesions involved the masticator space (n=8), the buccal space (n=6), the nasopharynx (n=5), the paranasal sinus (n=4), the parapharyngeal space (n=3), the prevertebral space (n=2), the orbit (n=2), the carotid space (n=2), the paravertebral space (n=1), parotid space (n=1), and the oral cavity (n=1). In ten of eleven cases, there was adjacent bone change. In three cases, the cavernous sinus was involved, and in two, the dura. One case involved both of them. At T2-weighted imaging, the lesions showed hypointensity in nine of ten cases; in four of nine, signal intensity was markedly low, and in no case was it diffusely high. In five of nine cases, the mass decreased in size after steroid therapy. CONCLUSION: Inflammatory pseudotumor showed iso-to hypointensity at T2-weighted imaging. Lymphadenopathy was not apparent.

Malignant Ve rsus Benign Lesions in the Head and Neck: The Usefulness of Magnetization Transfer Imaging

PURPOSE: To determine whether magnetization transfer ratio(MTR) helps differentiate malignant from benignlesions of the head and neck. MATERIALS AND METHODS: In 36 patients with pathologically proven head and necklesions (malignant tumor, n=22; benign tumor and inflammation, n=14), we prospectively obtained axial SE T1, TSET2, and pre-and post-MT images(2D FLASH; TR/TE/=500/12, flip angle=20 degree) using a 1.5T superconducting unit. TheMT pulse used for MT images was 7 msec gaussian, with 2 kHz off-resonance. The signal intensities of ROI oflesions, muscle, fat, and CSF were measured during pre- and post-MT imaging. MTRs and corrected MTRs(cMTRs) werecalculated and compared between benign and malignant lesions. Statistical differences were evaluated by Wilcoxonrank sum and student t test. RESULTS: Statistically significant differences were found between MTRs and cMTRs ofmalignant and benign lesions(p<0.01) and muscle (p<0.01). The differences in MTRs and cMTRs of benign andfat(p<0.01) or CSF(p<0.01) were also statistically significant. In the case of malignant tumors, mean MTR and cMTRwere greater than those of benign lesions(0.343 +/-0.024 and 0.328 +/-0.026, vs 0.228 +/-0.049 and 0.193 +/-0.047,p<0.01). Using a criterion of 0.3 for malignancy, the diagnostic sensitivity, specificity, and accuracy of MTR formalignancy are 91, 93, and 92%, respectively. Using a criterion of 0.28, the corresponding figures for cMTR 95,93, and 94%, respectively. CONCLUSION: MTR analysis of MT imaging could help to differentiate malignant andbenign lesions of the head and neck.

Magnetization Transfer Ratio in Head and Neck Lymphadenopathy

PUYPOSE: The purpose of this study was to determine whether the magnetization transfer ratio(MTR) differs between malignant and benign cervical lymphadenopathy. MATERIALS AND METHODS: Magnetization transfer ratios were obtained from 104 lymph nodes of 43 patients. Fifty-five nodes were malignant and 49 were benign. Biopsy or cervical lymph node dissection was performed in 83 nodes, while the remaining 21 were diagnosed clinically or by follow-up imaging studies. Among the 55 malignant nodes, squamous cell carcinomas accounted for 29 cases, lymphomas for 15, undifferentiated carcinomas for four, acute myelogenous leukemia for four, and melanomas for three. The 49 benign nodes comprised 21 cases of reactive hyperplasia, 12 of Kikuchi's disease, nine of acute lymphadenitis, and seven of tuberculous lymphadenitis. All scans were performed using a 1.5T Magnetom Vision(Siemens, Erlangen, Germany) with phased-array or Helmholtz-type neck coil. Scanning was performed with and without magnetization transfer pulse(MT pulse : 11.2 T, 250 Hz band-width, off-set 2.0 KHz) using FLASH 2D sequencing. The region of interest(ROI) for signal intensity(SI) measurements was sampled at the same nodes by keeping the position, shape and size of the ROI constant for the scans before and after the MT pulse was applied. SI measurements were repeated more than three times in each node and the mean value was used to calculate MTR. In this study, however, corrected MTRs(CoMTRs) were used for correction of the effect of background noise produced by magnetic field inhomogeneity. RESULTS: Mean CoMTRs of malignant and benign nodes were 0.33(SD: +/- 0.04) and 0.28(SD: +/- 0.05), respectively. This difference was statistically significant. At CoMTR 0.31, the sensitivity and specificity of malignant nodes were 83% and 75%, respectively. CONCLUSION: A CoMTR of above 0.31 suggests malignant lymphadenopathy. CoMTR is one of the MR criteria which can serve to differentiate between malignant and benign lymphadenopathy.

Primary Sinonasal Lymphoma: CT and MR Findings

PURPOSE: To evaluate the radiologic characteristics of sinonasal lymphoma, as seen on CT and MR MATERIALS AND METHODS: In eighteen patients with pathologically-proven non-hodgkin's lymphoma in the sinonasal cavity, CT andMR images were retrospectively reviewed. CT and MR findings were analyzed for tumor location, degree ofinfiltration into the adjacent structure, degree of enhancement, and the presence of bone change. Tthe last-namedwas classified as one of four types : complete destruction, segmental destruction, thinning, or sclerotic change. RESULTS: Masses in the nasal cavity (N=17) and ethomoid sinus (N=16) were most common, and the remainder wereaccounted for by maxillary sinus(N=6), sphenoid sinus(N=2), and frontal sinus(N=2), In 16 cases, the involvementof more than two sinonasal compartments was demonstrated ; the deensity of these masses was shown by precontrastCT to be similar to that of facial muscles ; affer contrast enhancement, all except one (15/16) showed homogeneousenhancement. Tumor infiltration of the adjacent structure was identified in the nasopharynx(N=9), anterior buccalspace(N=7), orbit(n=6), subcutaneous layer of the cheek(N=3), and infratemporal fossa(N=3). Direct extension ofthe tumor from the nasal fossa to the nasopharynx or anterior buccal space was demonstrated. Among 18 cases, bonechange was seen in 12, segmental destruction in eight, complete destruction in six, thinning in two, and scleroticchange in two. Four of the six cases with complete bone destruction showed hyperdense linear density within themass ; CT showed that after treatment, bony regrowth had occurred. In two cases, MRI showed intermediate signalintensity of the masses on T1WI, iso or slightly high signal intensity on T2WI, and moderate enhancement onpostcontrast T1WI. CONCLUSION: On CT, sinonasal lymphoma usually showed homogenous enhancement, extensivelyinfiltration of the adjacent structure, but no massive bone destruction. Hyperdense linear density, suggestingghost bone and seen in spite of massive bone destruction, may be a characteristic finding of sinonasal lymphoma.