Evaluating Tumors and Tumorlike Lesions of the Nasal Cavity, the Paranasal Sinuses, and the Adjacent Skull Base With Diffusion-Weighted MRI

Detection of bone metastases using diffusion weighted magnetic resonance imaging: comparison with (11)C-methionine PET and bone scintigraphy

PURPOSE

We evaluated the ability of diffusion-weighted imaging (DWI) to detect bone metastasis by comparing the results obtained using this modality with those obtained using (11)C-methionine (MET) positron emission tomography (PET) and bone scintigraphy.

MATERIALS AND METHODS

This retrospective study involved 29 patients with bone metastasis. DWI was obtained using a single-shot echo planar imaging (EPI) sequence with fat suppression using a short inversion time inversion recovery sequence. The detection capabilities of DWI for bone metastases were compared with those of whole body MET PET (in 19 patients) and 99mTc-methylene diphosphonate bone scintigraphy (in 15 patients).

RESULTS

Among the 19 patients who were diagnosed using DWI and PET, the PET identified 39 bone metastases, while the DWI identified 60 metastases out of 69 metastases revealed with conventional magnetic resonance imaging (MRI). Among the 15 patients who were diagnosed using DWI and bone scintigraphy, the bone scintigraphy identified 18 bone metastases, while the DWI identified 72 metastases out of 78 metastases revealed with conventional MRI. The overall bone metastasis detection rates were 56.5% for PET, 23.1% for bone scintigraphy and 92.3% for DWI.

CONCLUSION

DWI is a very sensitive method for detecting bone metastasis and is superior to MET PET and bone scintigraphy in terms of its detection capabilities.

Superior clinical impact of FDG-PET compared to MRI for the follow-up of a patient with sacral lymphoma

The assessment of residual tumors after treatment of malignant lymphoma (ML) is often difficult. Here we report a case of non-Hodgkin's lymphoma with a huge sacral tumor. After chemotherapy and following radiation therapy, a residual mass was detected on magnetic resonance imaging (MRI). However, a hypermetabolic lesion in the sacrum disappeared on (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) and clinically the patient was considered to achieve complete remission. Seven months after the completion of radiation therapy, a new tumor-like lesion in the sacrum developed on MRI, but hypermetabolic lesions were not detected on (18)F-FDG-PET. Recurrence of lymphoma was denied by open biopsy of the lesion. (18)F-FDG-PET has been of widespread use not only for staging but for post-treatment assessment of ML. Although MRI is a standard imaging tool for the assessment of bone involvement of ML, there have been few reports documenting the results of comparative studies on the usefulness of (18)F-FDG-PET and MRI for the evaluation of residual mass in bone involvement of ML. The present case suggests that (18)F-FDG-PET is superior to MRI not only in the evaluation of a residual mass but in the judgment of recurrence after treatment of such patients.

Diffusion-weighted imaging in head and neck cancers

This article reviews the utility of diffusion-weighted imaging (DWI) in the diagnosis, prognosis and monitoring of treatment response in tumors arising in the head and neck region. The apparent diffusion coefficient (ADC) value, determined from DWI, can help in cancer staging and detection of subcentimeter nodal metastasis. The ADC value also discriminates carcinomas from lymphomas, benign lesions from malignant tumors and tumor necrosis from abscesses. Low pretreatment ADC values typically predict a favorable response to chemoradiation therapy. These promising reports indicate the potential of DWI as a potential biomarker for diagnosis and monitoring of treatment response in head and neck cancers. In view of the overlapping ADC values between different salivary gland tumors, care should be taken when interpreting these results and other imaging parameters should be considered for a better diagnosis. Susceptibility and motion-induced artifacts may sometimes degrade DWI image quality; however, novel techniques are being developed to overcome these drawbacks.

Robust estimation of the apparent diffusion coefficient (ADC) in heterogeneous solid tumors

The least-squares algorithm is known to bias apparent diffusion coefficient (ADC) values estimated from magnitude MR data, although this effect is commonly assumed to be negligible. In this study the effect of this bias on tumor ADC estimates was evaluated in vivo and was shown to introduce a consistent and significant underestimation of ADC, relative to those given by a robust maximum likelihood approach (on average, a 23.4 +/- 12% underestimation). Monte Carlo simulations revealed that the magnitude of the bias increased with ADC and decreasing signal-to-noise ratio (SNR). In vivo, this resulted in a much-reduced ability to resolve necrotic regions from surrounding viable tumor tissue compared with a maximum likelihood approach. This has significant implications for the evaluation of diffusion MR data in vivo, in particular in heterogeneous tumor tissue, when evaluating bi- and multiexponential tumor diffusion models for the modeling of data acquired with larger b-values (b > 1000 s/mm(2)) and for data with modest SNR. Use of a robust approach to modeling magnitude MR data from tumors is therefore recommended over the least-squares approach when evaluating data from heterogeneous tumors.

Leiomyoma of the sinonasal cavity: CT and MRI findings

AIM

To determine the computed tomography (CT) and magnetic resonance imaging (MRI) features of leiomyoma of the sinonasal cavity.

MATERIALS AND METHODS

Six patients with histology-proven leiomyomas in the sinonasal cavity were retrospectively reviewed. All six patients underwent CT and three patients also underwent MRI. The following imaging features were reviewed: size, margin, CT attenuation, MRI signal intensity, and lesion extent. In addition, the time-intensity curve (TIC) of dynamic contrast-enhanced (DCE) MRI and diffusion-weighted imaging (DWI) were analysed in two patients.

RESULTS

All leiomyomas had well-defined margins. The mean size was 36 mm (range 20-51 mm). On unenhanced CT, the lesions appeared isodense to cerebral grey matter in four (67%) and slightly hypodense in two (33%) patients. Leiomyomas appeared isointense On T1-weighted imaging (WI) and slightly hyperintense on T2WI in three patients. The lesions showed moderate contrast enhancement. Two patients underwent DCE MRI, and the TIC showed a rapidly enhancing and slow washout pattern. The mean apparent diffusion coefficient (ADC) value were 1.66x10(-3) mm(2)/s and 1.78x10(-3) mm(2)/s for the two lesions, respectively.

CONCLUSIONS

Well-defined, homogeneous, expansile masses without bony erosion are typical features of leiomyoma. Althrough rare, this entity should be included in the differential diagnosis of benign tumours in this region.

Assessment of nasal and paranasal sinus masses by diffusion-weighted MR imaging

PURPOSE

To assess nasal and paranasal sinus masses by diffusion-weighted echoplanar magnetic resonance imaging (MRI).

PATIENTS AND METHODS

This prospective study included 55 consecutive patients (34 males, 21 females; aged 14-64 years, mean 39 years) with nasal and paranasal sinus masses. All underwent diffusion-weighted MRI using single-shot echoplanar imaging (EPI) with a b factor of 0.500 and 1000 s/mm2. Apparent diffusion coefficient (ADC) maps were constructed, allowing ADC values of the mass to be calculated and correlated with histopathological findings.

RESULTS

The mean ADC value of nasal and paranasal sinus malignant lesions (1.10+/-0.25x10(-3) mm2/s) was significantly different (P=0.001) from that of benign lesions (1.78+/-0.41x10(-3) mm2/s). Also, there was a significant ADC difference between carcinoma and sarcoma (P=0.01) as well as between well differentiated and poorly differentiated malignancies (P=0.005). Using an ADC value of 1.53x10(-3) mm2/s as the threshold value for differentiating malignant from benign lesions, the best result obtained had an accuracy of 93%, sensitivity of 94%, specificity of 92%, a positive predictive value of 92% and negative predictive value of 94%. However, the use of 0.97x10(-3) mm2/s and 1.16x10(-3) mm2/s as threshold values to differentiate carcinomas from sarcomas and poorly differentiated malignancy, respectively, gave the best results.

CONCLUSION

The ADC value is a non-invasive imaging parameter that can be used to assess nasal and paranasal sinus masses, as it can help in the differentiation of malignant tumors from benign lesions, and in the characterization and grading of malignancies.

Head and neck squamous cell carcinoma: value of diffusion-weighted MR imaging for nodal staging

PURPOSE

To evaluate diffusion-weighted (DW) magnetic resonance (MR) imaging, as compared with turbo spin-echo MR imaging, for the detection of nodal metastases in head and neck squamous cell carcinoma (HNSCC).

MATERIALS AND METHODS

The study was approved by the ethics committee, and patients gave written informed consent. Before undergoing surgery, 33 consecutive patients underwent 1.5-T MR imaging, including DW imaging performed with a wide range of b values (0-1000 sec/mm(2)). The apparent diffusion coefficients (ADCs) of lymph nodes 4 mm or greater in short-axis diameter depicted on images obtained with b values of 0 and 1000 sec/mm(2) were calculated. After topographic correlation, the lymph nodes were evaluated microscopically with prekeratin immunostaining. The optimal ADC thresholds for discriminating between metastatic and benign lymph nodes were determined. The sensitivity, specificity, and accuracy of DW imaging were calculated separately-on per-lymph-node and per-neck-level bases-for all lymph nodes and for supracentimeter and subcentimeter lymph nodes and were compared with corresponding turbo spin-echo MR imaging values.

RESULTS

Correlation of histopathologic and radiologic findings was possible for 301 lymph nodes. The ADC derived from the signal intensity averaged across images obtained with b values of 0 and 1000 sec/mm(2) (ADC(b0-1000)) was 1.19 x 10(-3) mm(2)/sec +/- 0.22 (standard deviation) for benign lymph nodes and 0.85 x 10(-3) mm(2)/sec +/- 0.27 for malignant lymph nodes (P < .0001). With an optimal ADC(b0-1000) threshold of 0.94 x 10(-3) mm(2)/sec, 84% sensitivity, 94% specificity, and 91% accuracy for differentiation of malignant versus benign status of each lymph node and 94% sensitivity, 97% specificity, and 97% accuracy for differentiation at each neck level were achieved. Compared with turbo spin-echo imaging, DW imaging had higher sensitivity (76% vs 7%) but slightly lower specificity (94.0% vs 99.5%) for detection of subcentimeter nodal metastases.

CONCLUSION

DW imaging performed with ADC(b0-1000) values had higher accuracy than turbo spin-echo MR imaging in nodal staging, providing added value in the detection of subcentimeter nodal metastases.

Sellar lymphoma mimicking sphenoid infection presenting with cavernous sinus syndrome

Lymphomas can occur throughout the body, but are relatively rare in the sphenoid region. The clinical presentations are atypical, ranging from nasal symptoms, pituitary hormone dysfunction and neurological impairment. We report a 63-year-old female patient who suffered nasal discharge, retro-ocular pain and left lateral gaze palsy for 3 months. Cranial MRI revealed sellar and suprasellar lesions involving the clivus, cavernous sinus and sphenoid sinus. The patient was treated for chronic sphenoid sinusitis. Histopathological review for possible misdiagnosis was arranged owing to treatment failure 1 month later. The final diagnosis was primary large B-cell lymphoma, which was confirmed by immunohistochemical study and systemic survey. The symptoms of sellar lymphoma resemble those of chronic sphenoid sinusitis. MRI and hematoxylin and eosin histological examination can accurately diagnose most cases. Immunohistochemistry assay is recommended in equivocal cases and provides a more detailed tumor classification.

Technology insight: water diffusion MRI--a potential new biomarker of response to cancer therapy

Diffusion-weighted MRI (DW-MRI) is a functional imaging technique that displays information about the extent and direction of random water motion in tissues. Water movement in tissues is modified by interactions with hydrophobic cellular membranes, intracellular organelles and macromolecules. DW-MRI provides information on extracellular-space tortuosity, tissue cellularity and the integrity of cellular membranes. Images can be sensitive to large or small displacements of water, therefore, macroscopic water flows and microscopic water displacements in the extracellular space can be depicted. Preclinical and clinical data indicate a number of potential roles of DW-MRI in the characterization of malignancy, including determination of lesion aggressiveness and monitoring response to therapy. This Review outlines the biological basis of observations made on DW-MRI and describes how measurements are acquired and quantified, and discusses the interpretation of images and limitations of the technique. The strength of evidence for adoption of DW-MRI as a biomarker for the assessment of tumor response is presented.

Apparent diffusion coefficients of benign and malignant salivary gland tumors. Comparison to histopathological findings

OBJECTIVE

To evaluate the apparent diffusion coefficient (ADC) of benign and malignant salivary gland tumors in comparison to histopathological findings.

MATERIALS AND METHODS

This study included 32 patients with a wide spectrum of major salivary gland tumors (17 benign, 15 malignant). Diffusion-weighted imaging (DWI) and ADC measurements were performed in all patients. The degrees of extracellular components (myxoid and chondroid matrices, microcysts and hyalinization), were histopathologically classified as mild, moderate and conspicuous. Comparisons were made of mean ADC values between benign and malignant tumors, and among tumors showing different degrees of extracellular components.

RESULTS

Mean ADC values were 1.09+/-0.34 x 10(-3) mm(2)/s in malignant salivary gland tumors and 1.40+/-0.43 x 10(-3) mm(2)/s in benign salivary gland tumors. No significant difference in mean ADC values was found between benign and malignant tumors (P>0.05). However, mean ADC values increased with the degree of extracellular components. Mean ADC values were significantly different between mild and moderate degrees (P<0.05) of extracellular components, and between mild and conspicuous degrees (P<0.05), in both benign and malignant tumor groups.

CONCLUSION

In this study, ADC values alone did not allow differentiation between benign and malignant salivary gland tumors. Comparison with histopathological findings suggests a correlation between the amount of extracellular components and mean ADC values in salivary gland tumors.