Intravoxel incoherent motion imaging measurement of perfusion changes in the parotid gland provoked by gustatory stimulation: A pilot study

Image denoising and model-independent parameterization for IVIM MRI

Objective. To improve intravoxel incoherent motion imaging (IVIM) magnetic resonance Imaging quality using a new image denoising technique and model-independent parameterization of the signal versusb-value curve.Approach. IVIM images were acquired for 13 head-and-neck patients prior to radiotherapy. Post-radiotherapy scans were also acquired for five of these patients. Images were denoised prior to parameter fitting using neural blind deconvolution, a method of solving the ill-posed mathematical problem of blind deconvolution using neural networks. The signal decay curve was then quantified in terms of several area under the curve (AUC) parameters. Improvements in image quality were assessed using blind image quality metrics, total variation (TV), and the correlations between parameter changes in parotid glands with radiotherapy dose levels. The validity of blur kernel predictions was assessed by the testing the method's ability to recover artificial 'pseudokernels'. AUC parameters were compared with monoexponential, biexponential, and triexponential model parameters in terms of their correlations with dose, contrast-to-noise (CNR) around parotid glands, and relative importance via principal component analysis.Main results. Image denoising improved blind image quality metrics, smoothed the signal versusb-value curve, and strengthened correlations between IVIM parameters and dose levels. Image TV was reduced and parameter CNRs generally increased following denoising.AUCparameters were more correlated with dose and had higher relative importance than exponential model parameters.Significance. IVIM parameters have high variability in the literature and perfusion-related parameters are difficult to interpret. Describing the signal versusb-value curve with model-independent parameters like theAUCand preprocessing images with denoising techniques could potentially benefit IVIM image parameterization in terms of reproducibility and functional utility.

Routine and Advanced Diffusion Imaging Modules of the Salivary Glands

This article reviews the role of routine and advanced diffusion imaging modules of the salivary glands. Routine and advanced diffusion imaging modules have a role in differentiation of malignant from benign salivary gland tumors, characterization of some benign salivary gland tumors, and staging of salivary gland cancer. The role of advanced diffusion modules in patients with salivary gland cancer after surgery, radiation therapy, or radioiodine therapy is discussed. Advanced diffusion imaging modules can help in diagnosis and staging of Sjögren syndrome.

Intravoxel incoherent motion magnetic resonance imaging of the normal-appearing parotid glands in patients with differentiated thyroid cancer after radioiodine therapy

Background Radiation damage to the salivary gland is a common complication of radioiodine therapy (RIT) in the patients with differentiated thyroid cancer (DTC). Purpose To investigate the feasibility of using intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) to detect radiation-induced changes of normal-appearing parotid glands in the patients after RIT for DTC. Material and Methods We prospectively enrolled 20 patients with RIT-induced sialoadenitis and 20 healthy control (HC) participants. The patients were divided into intermediate and late groups, and a questionnaire was used to assess the related symptoms. IVIM MRI was scanned using nine b-values (0, 50, 100, 150, 200, 400, 600, 800, and 1000 s/mm²). Quantitative parameters (pseudodiffusion coefficient, D*; perfusion fraction, f; tissue diffusivity, D) were obtained using a biexponential model and compared among different groups using one-way analysis of variance (ANOVA) test. Correlations between significant parameters and symptom score were assessed using Spearman's correlation analysis. Results The f and D value differed significantly (f, P = 0.016; D, P = 0.006) among different groups. Post hoc analysis showed that f and D value of intermediate group were significantly higher than those of HC group (f, P = 0.012; D, P = 0.004), while no significant differences between late group and HC group (f, P = 0.852; D, P = 0.707). Significant positive correlation was found between f value and the total symptom score of the patients in intermediate group ( P = 0.028, r = 0.762). Conclusion The IVIM MRI might be feasible to detect the radiation-induced changes of parotid glands in the patients after RIT for DTC.

Differentiating between benign and malignant sinonasal lesions using dynamic contrast-enhanced MRI and intravoxel incoherent motion

PURPOSE

To explore the value of dynamic contrast-enhanced MRI (DCE-MRI) and intravoxel incoherent motion (IVIM) for distinguishing between benign and malignant sinonasal lesions and investigate the correlations between the two methods.

METHODS AND MATERIALS

Patients with sinonasal lesions (42 benign and 31 malignant) who underwent DCE-MRI and IVIM before confirmation by histopathology were enrolled in this prospective study. Parameters derived from DCE-MRI and IVIM were measured, the optimal cut-off values for differential diagnosis were determined, and the correlations between the two methods were evaluated. Statistical analyses were performed using the Wilcoxon rank sum test, receiver operating characteristic (ROC) curve analysis, and Spearman's rank correlation.

RESULTS

Significantly higher K^trans and K_ep values but lower D and f values were found in malignant lesions than in benign lesions (all p<0.001). There were no significant differences in the V_e and D* values between the two groups. The area under the curve (AUC) of K^trans was significantly higher than those of other parameters. There was no significant difference between the AUCs of DCE-MRI and IVIM with parameters combined (p=0.86). Significant inverse but weak correlations were found between D and K^trans (r=-0.46, p<0.001), f and K^trans (r=-0.41, p<0.001), D and K_ep (r=-0.37, p=0.008), and f and K_ep (r=-0.33, p=0.004).

CONCLUSIONS

DCE-MRI and IVIM can effectively differentiate between benign and malignant sinonasal lesions. IVIM findings correlate with DCE-MRI results and may represent an alternative to DCE-MRI.