Evaluating the Elasticity of Metastatic Cervical Lymph Nodes in Head and Neck Squamous Cell Carcinoma Patients Using DWI-based Virtual MR Elastography

Evaluation of infrapatellar fat pad elasticity in knee osteoarthritis using IVIM-DWI-based virtual MR elastography: repeatability and reproducibility analysis

BACKGROUND

Fibrosis of the infrapatellar fat pad (IPFP) leads to changes in its stiffness, which may impact knee osteoarthritis. However, few studies have utilized virtual MR elastography to assess the variations of the IPFP. This study aimed to evaluate the value of intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI)-based virtual MR elastography (vMRE) in the IPFP by assessing the test-retest repeatability, as well as intra- and inter-observer reproducibility.

METHODS

A total of 71 subjects underwent IVIM-DWI examinations, which were conducted twice with an interval of 30-60 min using an 18-channel knee coil at 3T. Shifted apparent diffusion coefficient (sADC) was calculated from two different sets of b-values (b = 200/800 sec/mm2 and 200/1500 sec/mm2) and then converted to IVIM-DWI MRI-based virtual shear modulus (μdiff_800 and μdiff_1500). Two readers independently delineated regions of interest (ROI) within the IPFP on the vMRE stiffness map to obtain the mean and standard deviation (SD) values of μdiff. Short-term test-retest repeatability, as well as intra- and inter-observer agreement were assessed using the intra-class correlation coefficient (ICC), the coefficient of variation (CoV), and Bland-Altman limits of agreement (LoA).

RESULTS

The mean and SD values of μdiff_1500, along with the mean value of μdiff_800 exhibited excellent intra- and inter-observer reproducibility agreement (ICC ≥ 0.90 and CoV ≤ 10%, P˂ 0.001). The intra- and inter-observer ICCs for the mean values of μdiff_800 were 0.917 and 0.901, respectively, while the ICCs for the SD values of μdiff_800 were 0.870 and 0.863, with CoV exceeding 10% (P˂ 0.001). The test-retest repeatability of the average value of μdiff_1500 was excellent (ICC = 0.902; CoV = 6.8%) compared to μdiff_800 (ICC = 0.877; CoV = 15.3%). Test-retest repeatability of SD for μdiff_1500 was good (ICC = 0.803; CoV = 11.5%) in comparison to SD for μdiff_800 (ICC = 0.796; CoV = 13.5%).

CONCLUSIONS

IVIM-DWI-based vMRE demonstrated significant potential as a reliable tool for measuring tissue elasticity in the IPFP, exhibiting higher repeatability for μdiff_1500 than for μdiff_800.

Model-free parameters derived from intravoxel inherent motion combined with tumor aggressiveness indicators in predicting 5-year treatment outcome in NPC

PURPOSE

To evaluate the value of model-free parameters (virtual magnetic resonance elastography [vMRE] and signature index [S-index]) and tumor aggressiveness indicators (contralateral pharyngeal recess invasion [CPRI] and tumor growth type [TGT]) in forecasting 5-year treatment outcomes in nasopharyngeal carcinoma (NPC).

MATERIALS AND METHODS

A total of 106 patients were included in this study. Only two b-values were employed to calculate vMRE and S-index. Univariate and multivariate Cox analyses were conducted with clinical factors as confounding variables. Multivariate logistic analysis was used to construct multiple models. The additional value of CPRI and TGT was evaluated through net reclassification improvement index (NRI) and integrated discrimination improvement (IDI). Model performance and robustness were evaluated.

RESULTS

The predictive performance of vMRE and S-index (area under the curve [AUC]: 0.620 ∼ 0.639) was comparable to that of model-based parameters (AUC: 0.570 ∼ 0.658, all P ≥ 0.366). CPRI and TGT independently predicted progression-free survival (PFS) and overall survival (OS). Combined models significantly outperformed than the TNM stage model (all P ≤ 0.002) and vMRE-based or S-index-based model (all NRI ≥ 0.105 and IDI ≥ 0.085) in terms of 5-year OS (AUC: 0.840 ∼ 0.843) and 5-year PFS (AUC: 0.786 ∼ 0.793). The combined model demonstrated robust performance through Hosmer-Lemeshow test, cross-validation (iteration = 1000), 7:3 validation (chronologically or randomly), and post-hoc subgroup analysis.

CONCLUSION

The advent of vMRE and S-index has streamlined the clinical applications without compromising the value of IVIM technique. Incorporating CPRI and TGT has further enhanced the predictive performance.

CLINICAL RELEVANCE STATEMENT

Only two b-values are needed to calculate vMRE and S-index, which, along with CPRI and TGT, are pivotal in forecasting long-term survival in patients with NPC.

Imaging Modalities for Head and Neck Cancer: Present and Future

Several imaging modalities are utilized in the diagnosis, treatment, and surveillance of head and neck cancer. First-line imaging remains computed tomography (CT); however, MRI, PET with CT (PET/CT), and ultrasound are often used. In the last decade, several new imaging modalities have been developed that have the potential to improve early detection, modify treatment, decrease treatment morbidity, and augment surveillance. Among these, molecular imaging, lymph node mapping, and adjustments to endoscopic techniques are promising. The present review focuses on existing imaging, novel techniques, and the recent changes to imaging practices within the field.

Differentiation of salivary gland tumours using diffusion-weighted image-based virtual MR elastography: a pilot study

OBJECTIVES

Differentiation among benign salivary gland tumours, Warthin tumours (WTs), and malignant salivary gland tumours is crucial to treatment planning and predicting patient prognosis. However, differentiation of those tumours using imaging findings remains difficult. This study evaluated the usefulness of elasticity determined from diffusion-weighted image (DWI)-based virtual MR elastography (MRE) compared with conventional magnetic resonance imaging (MRI) findings in differentiating the tumours.

METHODS

This study included 17 benign salivary gland tumours, 6 WTs, and 11 malignant salivary gland tumours scanned on neck MRI. The long and short diameters, T1 and T2 signal intensities, tumour margins, apparent diffusion coefficient (ADC) values, and elasticity from DWI-based virtual MRE of the tumours were evaluated. The interobserver agreement in measuring tumour elasticity and the receiver operating characteristic (ROC) curves were also assessed.

RESULTS

The long and short diameters and the T1 and T2 signal intensities showed no significant difference among the 3 tumour groups. Tumour margins and the mean ADC values showed significant differences among some tumour groups. The elasticity from virtual MRE showed significant differences among all 3 tumour groups and the interobserver agreement was excellent. The area under the ROC curves of the elasticity were higher than those of tumour margins and mean ADC values.

CONCLUSION

Elasticity values based on DWI-based virtual MRE of benign salivary gland tumours, WTs, and malignant salivary gland tumours were significantly different. The elasticity of WTs was the highest and that of benign tumours was the lowest. The elasticity from DWI-based virtual MRE may aid in the differential diagnosis of salivary gland tumours.