Miho Sasaki

Salivary gland ultrasonography: can it be an alternative to sialography as an imaging modality for Sjögren's syndrome?

Objectives Salivary ultrasonography (US) was evaluated as an alternative imaging modality to sialography for Sjögrens syndrome (SS). Methods Parotid sialography and parotid and submandibular US were performed in 360 patients (188 with SS and 172 non-SS) who were suspected of SS and had fulfilled the American-European criteria (AEC) for SS or had received ≥3 of the objective examinations that were considered minimal requirements for classifying non-SS and had undergone both the imaging examinations. The glands were considered positive for SS if they exhibited peripheral sialoectatic changes on sialography and/or hypoechoic areas, echogenic streaks and/or irregular gland margins on US. The images obtained were independently rated as SS-positive or SS-negative by three radiologists in a blind fashion and the final decision was made by consensus. Interobserver and intermodality agreement was evaluated using κ values for sialography and parotid and/or submandibular US. Results Average κ values for the interobserver agreement were 0.81, 0.80 and 0.82 in sialography, parotid and submandibular US, respectively, indicating very good or good agreement. The κ value for intermodality agreement between sialography and parotid US was 0.81 and between sialography and submandibular US was 0.76, indicating very good and good agreement, respectively. The diagnostic ability of parotid US was significantly lower than that of sialography (p<0.001, McNemar test). However, the diagnostic ability of submandibular US was comparable to that of sialography (p=0.153). Conclusions Submandibular US is a promising technique that can be used as a practical alternative to sialography in the classification of SS.

Apparent diffusion coefficient mapping for sinonasal diseases: differentiation of benign and malignant lesions.

Because CT and conventional MR imaging findings of sinonasal lesions overlap considerably, these authors decided to evaluate the utility of diffusion-weighted imaging in differentiating these lesions. They obtained apparent diffusion coefficient values in 61 proved lesions (19 benign, 28 malignant, and 14 inflammatory). As expected, ADC values of malignant lesions were much lower than those of the other 2 types. Additionally, the higher the percentage area of the tumor that had low ADC, the greater was the chance of it being malignant. If 78% of lesion area had low ADC, the ability to differentiate between malignant and benign reached a 94% specificity. ADCs could also differentiate lymphoma from other malignant tumors. Conclusions: ADC mapping may be an effective MR imaging tool for the differentiation of benign/inflammatory lesions from malignant tumors in the sinonasal area. BACKGROUND AND PURPOSE: CT and MR imaging features of benign and malignant sinonasal lesions are often nonspecific. Therefore, we evaluated the ADC-based differentiation of these lesions. MATERIALS AND METHODS: We retrospectively assessed ADCs of 61 patients with histologically proved sinonasal tumors and tumorlike lesions: 19 benign lesions, 28 malignant tumors, and 14 inflammatory lesions. Overall ADCs and percentages of total tumor area with extremely low, low, intermediate, or high ADCs (ADC mapping) were determined by using 2 b-values (500 and 1000 s/mm2). RESULTS: ADCs of malignant tumors (0.87 ± 0.32 × 10−3 mm2/s) were significantly lower than those of benign (1.35 ± 0.29 × 10−3 mm2/s, P < .0001) and inflammatory (1.50 ± 0.50 × 10−3 mm2/s, P = .0002) lesions. On ADC mapping, percentages of total tumor area within malignant tumors having extremely low or low ADCs were significantly (P < .0001) greater than those within benign and inflammatory lesions. Cutoff points for ADC mapping (≥78% of tumor areas having extremely low or low ADCs) effectively differentiated benign or inflammatory lesions and malignant tumors with 75% sensitivity, 94% specificity, 85% accuracy, and 91% positive and 82% negative predictive values, respectively. ADCs also effectively discriminated lymphomas and SCCs from other malignant tumors. CONCLUSIONS: ADC mapping may be an effective MR imaging tool for the differentiation of benign/inflammatory lesions from malignant tumors in the sinonasal area.

Efficacy of Diffusion-Weighted Imaging for the Differentiation between Lymphomas and Carcinomas of the Nasopharynx and Oropharynx: Correlations of Apparent Diffusion Coefficients and Histologic Features

BACKGROUND AND PURPOSE: ADCs may help distinguish benign from malignant head and neck diseases. We sought to evaluate the effectiveness of ADC for differentiating between carcinomas and lymphomas of the nasopharynx and oropharynx. MATERIALS AND METHODS: We retrospectively compared the ADCs between 24 histologically proved lymphomas and 32 carcinomas, including 8 NPCs and 7 lymphomas of the nasopharynx, and 24 SCCs and 17 lymphomas of the oropharynx. ADCs were determined on tumor-by-tumor (overall ADCs) and pixel-by-pixel (ADC mapping) bases by using 2 b-values (500 and 1000 s/mm2). RESULTS: Lymphomas and oropharyngeal SCCs had unique histologic features in terms of keratinization, cell attenuation, stromal areas, and necrosis and had distinctive ADCs (0.503 ± 0.099 × 10−3 mm2/s for lymphomas and 0.842 ± 0.164 × 10−3 mm2/s for SCCs). However, NPCs and lymphomas were similar in terms of these histologic features, exhibiting comparable ADCs (0.567 ± 0.057 × 10−3 mm2/s for NPCs and 0.528 ± 0.094 × 10−3 mm2/s for lymphomas). Poorly and moderately differentiated SCCs with homogeneous T2 signals were indistinguishable from lymphomas on conventional MR images; however, ADCs of these SCC subtypes were significantly larger than those of lymphomas. ADC mapping profiles with respect to percentage of tumor areas of extremely low, intermediate, and high ADC levels were well-correlated with the histologic features of lymphomas, NPCs, and different types of SCCs. CONCLUSIONS: The effectiveness of ADC-based differentiation between lymphomas and carcinomas of the nasopharynx and oropharynx depends on their histologic characteristics.

Multiparametric MR Imaging of Sinonasal Diseases: Time-Signal Intensity Curve– and Apparent Diffusion Coefficient–Based Differentiation between Benign and Malignant Lesions

BACKGROUND AND PURPOSE: The sinonasal region is a platform for a broad spectrum of benign and malignant diseases, and image-based differentiation between benign and malignant diseases in this area is often difficult. Here, we evaluated multiparametric MR imaging with combined use of TICs and ADCs for the differentiation between benign and malignant sinonasal tumors and tumorlike diseases. MATERIALS AND METHODS: TICs obtained from dynamic contrast-enhanced MR imaging and ADCs were analyzed on a lesion-by-lesion (overall TIC and ADC) and pixel-by-pixel (TIC and ADC mapping) basis in patients with benign (n = 21) or malignant (n = 23) sinonasal tumors and tumorlike diseases. The TICs were semiautomatically classified into 5 distinctive patterns (flat, slow uptake, rapid uptake with low washout ratio, rapid uptake with high washout ratio, and miscellaneous). ADCs were determined by using b-values of 500 and 1000 s/mm2. RESULTS: Malignant sinonasal tumors had small (<25%) areas of the type 1 flat TIC profile as determined by pixel-by-pixel TIC analysis and large (≥50%) areas of low or extremely low ADCs (≤1.2 × 10−3 mm2/s) as determined by ADC mapping. Consequently, stepwise classification on the basis of TICs and ADCs successfully (at 100% accuracy) discriminated malignant from benign sinonasal diseases in the present patient cohort. CONCLUSIONS: Multiparametric MR imaging by using TICs and ADCs may help differentiate benign and malignant sinonasal diseases.

Intravoxel Incoherent Motion Imaging of Masticatory Muscles: Pilot Study for the Assessment of Perfusion and Diffusion During Clenching

OBJECTIVE The purpose of this study was to evaluate intravoxel incoherent motion (IVIM) imaging for assessing perfusion and diffusion of masticatory muscles during clenching. SUBJECTS AND METHODS A prospective study was performed to assess the perfusion and diffusion of masticatory muscles during clenching. The masseter and medial pterygoid muscles participate in clenching, and the lateral pterygoids do not. IVIM parameters (microvascular volume fraction, f; pure diffusion coefficient, D; and perfusion-related incoherent microcirculation, D*) were determined on both the clenching and the balancing sides in 24 volunteers. The Wilcoxon test was used to compare the IVIM parameters at rest and during clenching. RESULTS The f and D* values of the masseters significantly increased on the clenching side (f = 0.17 ± 0.10 vs 0.29 ± 0.11, p < 0.001; D* = 21.3 ± 18.5 × 10(-3) mm(2)/s vs 42.1 ± 33.3 × 10(-3) mm(2)/s, p = 0.0008). However, the D values did not change during clenching (1.26 ± 0.23 × 10(-3) mm(2) vs 1.21 ± 0.35 × 10(-3) mm(2)). The f values of the medial pterygoids also increased on the clenching side (0.20 ± 0.09 vs 0.30 ± 0.09, p < 0.001). On the balancing side, the f values of the masseters (0.19 ± 0.12 vs 0.30 ± 0.12, p < 0.001) and medial pterygoids (0.20 ± 0.09 vs 0.29 ± 0.11, p = 0.0007) significantly increased during clenching. In contrast, the IVIM values of the lateral pterygoids did not change. CONCLUSION IVIM imaging may be useful for assessing perfusion and diffusion of the masticatory muscles.

Simple and Reliable Determination of Intravoxel Incoherent Motion Parameters for the Differential Diagnosis of Head and Neck Tumors

Intravoxel incoherent motion (IVIM) imaging can characterize diffusion and perfusion of normal and diseased tissues, and IVIM parameters are authentically determined by using cumbersome least-squares method. We evaluated a simple technique for the determination of IVIM parameters using geometric analysis of the multiexponential signal decay curve as an alternative to the least-squares method for the diagnosis of head and neck tumors. Pure diffusion coefficients (D), microvascular volume fraction (f), perfusion-related incoherent microcirculation (D*), and perfusion parameter that is heavily weighted towards extravascular space (P) were determined geometrically (Geo D, Geo f, and Geo P) or by least-squares method (Fit D, Fit f, and Fit D*) in normal structures and 105 head and neck tumors. The IVIM parameters were compared for their levels and diagnostic abilities between the 2 techniques. The IVIM parameters were not able to determine in 14 tumors with the least-squares method alone and in 4 tumors with the geometric and least-squares methods. The geometric IVIM values were significantly different (p<0.001) from Fit values (+2±4% and −7±24% for D and f values, respectively). Geo D and Fit D differentiated between lymphomas and SCCs with similar efficacy (78% and 80% accuracy, respectively). Stepwise approaches using combinations of Geo D and Geo P, Geo D and Geo f, or Fit D and Fit D* differentiated between pleomorphic adenomas, Warthin tumors, and malignant salivary gland tumors with the same efficacy (91% accuracy = 21/23). However, a stepwise differentiation using Fit D and Fit f was less effective (83% accuracy = 19/23). Considering cumbersome procedures with the least squares method compared with the geometric method, we concluded that the geometric determination of IVIM parameters can be an alternative to least-squares method in the diagnosis of head and neck tumors.

Multiparametric MR imaging for differentiating between benign and malignant thyroid nodules: Initial experience in 23 patients

To evaluate multiparametric MR imaging with combined use of apparent diffusion coefficients (ADCs) and time‐signal intensity curves (TICs) for discriminating malignant thyroid nodules from benign ones.

Length of intact plasma membrane determines the diffusion properties of cellular water.

Molecular diffusion in a boundary-free medium depends only on the molecular size, the temperature, and medium viscosity. However, the critical determinant of the molecular diffusion property in inhomogeneous biological tissues has not been identified. Here, using an in vitro system and a high-resolution MR imaging technique, we show that the length of the intact plasma membrane is a major determinant of water diffusion in a controlled cellular environment and that the cell perimeter length (CPL) is sufficient to estimate the apparent diffusion coefficient (ADC) of water in any cellular environment in our experimental system (ADC = −0.21 × CPL + 1.10). We used this finding to further explain the different diffusion kinetics of cells that are dying via apoptotic or non-apoptotic cell death pathways exhibiting characteristic changes in size, nuclear and cytoplasmic architectures, and membrane integrity. These results suggest that the ADC value can be used as a potential biomarker for cell death.

Arterial Spin Labeling Imaging for the Parotid Glands of Patients with Sjögren’s Syndrome

Sjögren’s syndrome (SS) is characterized by hypofunction of the salivary and lacrimal glands. The salivary function is largely dependent upon the blood supply in the glands. However, the diseased states of the gland perfusion are not well understood. The arterial spin labeling (ASL) technique allows noninvasive quantitative assessment of tissue perfusion without the need for contrast agent. Here, we prospectively compared the perfusion properties of the parotid glands between patients with SS and those with healthy glands using ASL MR imaging. We analyzed salivary blood flow (SBF) kinetics of 22 healthy parotid glands from 11 volunteers and 28 parotid glands from 14 SS patients using 3T pseudo-continuous ASL imaging. SBF was determined in resting state (base SBF) and at 3 sequential segments after gustatory stimulation. SBF kinetic profiles were characterized by base SBF level, increment ratio at the SBF peak, and the differences in segments where the peak appeared (SBF types). Base SBFs of the SS glands were significantly higher than those of healthy glands (59.2 ± 22.8 vs. 46.3 ± 9.0 mL/min/100 g, p = 0.01). SBF kinetic profiles of the SS glands also exhibited significantly later SBF peaks (p < 0.001) and higher SBF increment ratios (74 ± 49% vs. 47 ± 39%, p = 0.04) than the healthy glands. The best SBF criterion (= 51.2 mL/min/100 mg) differentiated between control subjects and SS patients with 71% sensitivity and 82% specificity. Taken together, these results showed that the SS parotid glands were mostly hyperemic and the SS gland responses to gustatory stimulation were stronger and more prolonged than those of the healthy glands. The ASL may be a promising technique for assessing the diseased salivary gland vascularization of SS patients.

Comparison between ultrasonography and MR imaging for discriminating squamous cell carcinoma nodes with extranodal spread in the neck

OBJECTIVE To compare the diagnostic ability of ultrasonography (US) and MR imaging for discriminating squamous cell carcinoma (SCC) nodes with extranodal spread (ENS) in the neck. METHODS US and MR imaging was retrospectively evaluated for differentiating ENS-positive (n=28) from ENS-negative (n=26) SCC nodes (>10mm short-axis diameter) in 50 patients with head and neck SCCs. We assessed nodal size on US and MR images; irregular nodal margin on US; and vanishing nodal border, flare, and shaggy nodal margin signs on T1-, fat-suppressed T2-, and contrast-enhanced T1-weighted MR images, respectively. US and MR images were analyzed by 3 radiologists in consensus and the results were compared between ENS-positive and ENS-negative SCC nodes. RESULTS The nodal sizes of ENS-positive nodes (21±9 mm) were significantly larger than those of ENS-negative SCC nodes (14±4 mm) (p<0.001). Irregular nodal margins were more frequently observed in ENS-positive SCC nodes (75%) than in ENS-negative SCC nodes (12%). The vanishing nodal margin, flare, and shaggy nodal margin signs were more frequently observed in ENS-positive SCC nodes (93%, 89%, and 82%, respectively) than in ENS-negative nodes (46%, 19%, and 19%, respectively). A combination of size (≥22 mm) and imaging criteria (irregular margin or flare sign) best discriminated ENS-positive SCC nodes with 82% sensitivity, 89% specificity, and 85% accuracy for US and 89% sensitivity, 81% specificity, and 85% accuracy for MR imaging. CONCLUSION US discriminated ENS-positive from ENS-negative SCC nodes with comparable accuracy and higher specificity than MR imaging.