Actual applications of magnetic resonance imaging in dentomaxillofacial region

Magnetic resonance imaging (MRI) is a versatile imaging modality utilized in various medical fields. Specifically used for evaluation of soft tissues, with non-ionizing radiation and multiplanar sections that has provided great guidance to diagnosis. Nowadays, use of MRI in dental practice is becoming more pervasive, especially for the evaluation of head-and-neck cancer, detection of salivary gland lesions, lymphadenopathy, and temporomandibular joint disorders. Understanding the basic principles, its recent advances, and multiple applications in dentomaxillofacial region helps significantly in the diagnostic decision making. In this article, the principle of MRI and its recent advances are reviewed, with further discussion on the appearance of various maxillofacial pathosis.

Connective Tissue Disorders in Childhood: Are They All the Same?

Systemic connective tissue disorders are characterized by the presence of autoantibodies and multiorgan system involvement. Juvenile systemic lupus erythematosus with or without associated antiphospholipid syndrome; juvenile dermatomyositis; sclerodermiform syndromes, including systemic and localized sclerodermas and eosinophilic fasciitis; mixed connective tissue disease; and Sjögren syndrome are the disorders that affect children most frequently. Diagnosis is difficult, because the clinical presentation of patients is diverse, from mild to severe disease. In addition, all organs may be affected. However, a variety of imaging techniques are now available to investigate rheumatic disease in children. These imaging modalities offer the potential for earlier diagnosis and improved assessment of therapeutic response. This article reviews the main connective tissue disorders that affect children, highlighting their key imaging features on images acquired with different diagnostic imaging modalities and correlating these features with clinical and pathologic findings, when available. ^©RSNA, 2019.

Whole-Volume ADC Histogram Analysis in Parotid Glands to Identify Patients with Sjögren's Syndrome

At present, no gold standard for diagnosing Sjögren’s syndrome (SS) is available in clinical practice. The 2002 American–European Consensus Group classification criteria are used to diagnose SS. Clinically, it is challenging to distinguish patients with SS from suspected patients undergoing different therapies. A total of 52 patients with SS and 24 patients suspected of having the disease prospectively underwent 3.0-T magnetic resonance (MR) scanning, including diffusion-weighted imaging (b = 0 and 1000 s/mm²). The whole-volume apparent diffusion coefficient (ADC) histogram analysis generated ADC_mean, skewness, kurtosis, and entropy values from bilateral parotid glands. Continuous variables were compared using an independent two-sample t test, and categorical variable compared using the Fisher’s test between the two groups. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic performance of the indexes. Fisher’s tests demonstrated that some clinical indexes and MR morphology grades differed significantly between patients with SS and patients suspected of having the disease (all P ≤ 0.001). The parotid entropy value of patients with SS was significantly higher than that of patients suspected of having the disease (P < 0.001). Among MR parameters, entropy combined with kurtosis performed the best in differentiating patients with SS from those suspected of having SS (area under the ROC curve = 0.955). A whole-volume ADC histogram analysis might provide a series of parameters that reflect tissue characteristics.

Quantitative Analysis of Parotid Gland Secretion Function in Sjögren's Syndrome Patients with Dynamic Magnetic Resonance Sialography

Objective

To evaluate the secretory function of parotid glands by dynamic magnetic resonance (MR) sialography and determine the clinical performance of this technique in diagnosing and evaluating Sjögren's syndrome (SS) patients.

Materials and Methods

This study enrolled 29 healthy volunteers (25 women and 4 men; mean age, 34.8 ± 6.3 years; age range, 26–47 years) and 25 primary SS (pSS) patients (23 women and 2 men; mean age, 37.7 ± 7.9 years; age range, 25–50 years) with decreased secretory function. The volume of the parotid gland ducts was precisely measured for both groups at single pre- and 6 post-gustatory-stimulated phases. Time-dependent volume change ratio curves were generated, four parameters were derived from the curves: the slope of the increase in the first post-stimulation phase (slope_1st), the peak value, the time-to-peak, the total saliva secretion post-stimulation. All values were used to quantitatively evaluate the secretory function of the parotid gland. The repeated measurement analysis, Mann-Whitney U test and receiver operating characteristic curve were applied.

Results

Time-dependent volume change ratio curves demonstrated that there is a statistically significant difference between the two groups (F = 8.750; p = 0.005). A quickly increasing curve was shown in the volunteer group, whereas a slowly increasing curve was shown in the pSS patient group. The slope_1st, peak value and total saliva secretion post-stimulation of the patient group were significantly lower than those of the volunteer group (p = 0.005, p = 0.003, and p = 0.002, respectively). The time-to-peak between the two groups was not significantly different (p = 0.383). The slope_1st can be used as a discriminator to diagnose SS patients (p = 0.015; odds ratio = 4.234; area under the curve = 0.726).

Conclusion

Dynamic MR sialography is proven to be an effective method in evaluating salivary gland function and has a great potential in diagnosing and evaluating pSS patients.

Diffusional kurtosis imaging of parotid glands in Sjögren's syndrome: Initial findings

PURPOSE

To explore the role of diffusion kurtosis imaging (DKI) of parotid glands in diagnosing Sjögren's syndrome (SS).

MATERIALS AND METHODS

A total of 40 patients with SS and 40 healthy volunteers underwent 3.0T magnetic resonance imaging (MRI) including DKI, which generated the apparent diffusion coefficient (ADC), corrected diffusion (D), and diffusional kurtosis (K) values. The MR nodular grade was determined on the basis of MR morphological findings.

RESULTS

The parotid ADC, D, and K values in patients with SS were significantly higher than those of healthy volunteers (P = 0.011, < 0.001, 0.022, respectively). The parotid ADC and D values in patients with SS of MR nodular grade 0 were significantly higher than those of healthy volunteers (all P < 0.001). The parotid D value showed an accuracy of 75.0% and 87.9% in diagnosing patients with SS and MR nodular grade 0, respectively. The parotid ADC and D values correlated negatively, while the K values correlated positively with the MR nodular grade significantly in patients with SS (r = -0.741, -0.605, 0.424, all P < 0.001). All parotid DKI parameters differed significantly among patients with SS at different MR nodular grades (all P < 0.001).

CONCLUSION

Parotid DKI parameters hold great potential in diagnosing SS, especially in early-stage SS without MR morphological changes.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1409-1417.

Effects of regions of interest methods on apparent coefficient measurement of the parotid gland in early Sjögren's syndrome at 3T MRI

BACKGROUND

The apparent diffusion coefficient (ADC) has been used to assess parotid gland abnormalities in Sjögren's syndrome (SS) patients; however, few data exist on the influence of region of interest (ROI) methods on ADC measurements.

PURPOSE

To assess the influence of ROI methods on ADC measurement, and their diagnostic ability in detecting parotid gland abnormalities in early SS patients.

MATERIAL AND METHODS

Thirteen early SS patients underwent parotid gland diffusion-weighted imaging scans at a 3.0 T MR unit. Two readers independently measured the parotid gland ADC value using three different ROIs (whole-gland [WG], single-slice [SS], and reader-based circular [RBC]). The ADC value based on three different ROIs (ADC-ROI_WG, ADC-ROI_SS, ADC-ROI_RBC) were compared between the SS group and a matched healthy control (HC) group (n = 19). Receiver operating characteristic (ROC) curves and intra-class correlation coefficients (ICC) were used to determine the diagnostic ability and reproducibility of the parameters.

RESULTS

The ADC-ROI_WG, ADC-ROI_SS, and ADC-ROI_RBC in the SS group were all significantly higher than those in HC group (all P < 0.05). The ADC-ROI_WG showed better diagnostic ability than did ADC-ROI_RBC (P = 0.0200), while no significant difference was found between ADC-ROI_WG and ADC-ROI_SS (P = 0.4636). The ROI_WG method showed the best inter- and intra-reader agreement (ICC, 0.902 and 0.928, respectively), followed by ROI_SS and ROI_RBC.

CONCLUSION

The ROI methods can influence the parotid gland ADC measurements and their diagnostic ability. Considering our results, we suggest using in clinical practice single-slice ROIs to measure the ADC of the parotid gland.

Use of T1ρMR imaging in Sjögren's syndrome with normal appearing parotid glands: Initial findings

PURPOSE

To explore the feasibility of parotid spin-lattice relaxation time in the rotating frame (T1ρ) MR imaging in the diagnosis of Sjögren's syndrome (SS) without morphological changes of the parotid glands.

MATERIALS AND METHODS

The study enrolled 32 consecutive SS patients without morphological changes of parotid glands and 32 age- and gender-matched healthy volunteers who underwent parotid 3.0 Tesla MR imaging, including T1ρ sequences. Follow-up imaging was performed at 3 months. T1 signal intensities and T1ρ values of bilateral parotid glands were compared using paired samples t-test. Parotid T1 signal intensities and T1ρ values were compared using two independent samples t-test. Diagnostic performance of the parotid T1ρ values was evaluated by receiver operating characteristic analysis. The intraclass correlation coefficient (ICC) was calculated to evaluate the reproducibility of parotid T1ρ measurements.

RESULTS

There were no significant differences of T1 signal intensities and T1ρ values between bilateral parotid glands in SS patients and healthy volunteers (P = 0.170, 0.886 and 0.942, 0.229). The parotid T1ρ values of SS patients (96.47 ± 15.38 ms) were significantly higher than those of healthy volunteers (84.25 ± 6.11 ms) (P < 0.001), while there were no significant differences of T1 signal intensities between SS patients and healthy volunteers (P = 0.655). With a cutoff value of 88.02 ms, the sensitivity and specificity of the parotid T1ρ value was 75.0% and 100.0% in the diagnosis of SS. The reproducibility of parotid T1ρ measurement was excellent (ICC: 0.934-0.995).

CONCLUSION

Parotid T1ρ MR imaging held a potential role in diagnosing SS without morphological changes of parotid glands.

LEVEL OF EVIDENCE

2 J. Magn. Reson. Imaging 2017;45:1005-1012.

Kinetic Curve Type Assessment for Classification of Breast Lesions Using Dynamic Contrast-Enhanced MR Imaging

OBJECTIVE

The aim of this study was to employ a kinetic model with dynamic contrast enhancement-magnetic resonance imaging to develop an approach that can efficiently distinguish malignant from benign lesions.

MATERIALS AND METHODS

A total of 43 patients with 46 lesions who underwent breast dynamic contrast enhancement-magnetic resonance imaging were included in this retrospective study. The distribution of malignant to benign lesions was 31/15 based on histological results. This study integrated a single-compartment kinetic model and dynamic contrast enhancement-magnetic resonance imaging to generate a kinetic modeling curve for improving the accuracy of diagnosis of breast lesions. Kinetic modeling curves of all different lesions were analyzed by three experienced radiologists and classified into one of three given types. Receiver operating characteristic and Kappa statistics were used for the qualitative method. The findings of the three radiologists based on the time-signal intensity curve and the kinetic curve were compared.

RESULTS

An average sensitivity of 82%, a specificity of 65%, an area under the receiver operating characteristic curve of 0.76, and a positive predictive value of 82% and negative predictive value of 63% was shown with the kinetic model (p = 0.017, 0.052, 0.068), as compared to an average sensitivity of 80%, a specificity of 55%, an area under the receiver operating characteristic of 0.69, and a positive predictive value of 79% and negative predictive value of 57% with the time-signal intensity curve method (p = 0.003, 0.004, 0.008). The diagnostic consistency of the three radiologists was shown by the κ-value, 0.857 (p<0.001) with the method based on the time-signal intensity curve and 0.826 (p<0.001) with the method of the kinetic model.

CONCLUSIONS

According to the statistic results based on the 46 lesions, the kinetic modeling curve method showed higher sensitivity, specificity, positive and negative predictive values as compared with the time-signal intensity curve method in lesion classification.

Influence of amplitude-related perfusion parameters in the parotid glands by non-fat-saturated dynamic contrast-enhanced magnetic resonance imaging

PURPOSE

To verify whether quantification of parotid perfusion is affected by fat signals on non-fat-saturated (NFS) dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and whether the influence of fat is reduced with fat saturation (FS).

METHODS

This study consisted of three parts. First, a retrospective study analyzed DCE-MRI data previously acquired on different patients using NFS (n = 18) or FS (n = 18) scans. Second, a phantom study simulated the signal enhancements in the presence of gadolinium contrast agent at six concentrations and three fat contents. Finally, a prospective study recruited nine healthy volunteers to investigate the influence of fat suppression on perfusion quantification on the same subjects. Parotid perfusion parameters were derived from NFS and FS DCE-MRI data using both pharmacokinetic model analysis and semiquantitative parametric analysis. T tests and linear regression analysis were used for statistical analysis with correction for multiple comparisons.

RESULTS

NFS scans showed lower amplitude-related parameters, including parameter A, peak enhancement (PE), and slope than FS scans in the patients (all with P < 0.0167). The relative signal enhancement in the phantoms was proportional to the dose of contrast agent and was lower in NFS scans than in FS scans. The volunteer study showed lower parameter A (6.75 ± 2.38 a.u.), PE (42.12% ± 14.87%), and slope (1.43% ± 0.54% s(-1)) in NFS scans as compared to 17.63 ± 8.56 a.u., 104.22% ± 25.15%, and 9.68% ± 1.67% s(-1), respectively, in FS scans (all with P < 0.005). These amplitude-related parameters were negatively associated with the fat content in NFS scans only (all with P < 0.05).

CONCLUSIONS

On NFS DCE-MRI, quantification of parotid perfusion is adversely affected by the presence of fat signals for all amplitude-related parameters. The influence could be reduced on FS scans.

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.

Models and methods for analyzing DCE-MRI: a review

PURPOSE

To present a review of most commonly used techniques to analyze dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), discusses their strengths and weaknesses, and outlines recent clinical applications of findings from these approaches.

METHODS

DCE-MRI allows for noninvasive quantitative analysis of contrast agent (CA) transient in soft tissues. Thus, it is an important and well-established tool to reveal microvasculature and perfusion in various clinical applications. In the last three decades, a host of nonparametric and parametric models and methods have been developed in order to quantify the CA's perfusion into tissue and estimate perfusion-related parameters (indexes) from signal- or concentration-time curves. These indexes are widely used in various clinical applications for the detection, characterization, and therapy monitoring of different diseases.

RESULTS

Promising theoretical findings and experimental results for the reviewed models and techniques in a variety of clinical applications suggest that DCE-MRI is a clinically relevant imaging modality, which can be used for early diagnosis of different diseases, such as breast and prostate cancer, renal rejection, and liver tumors.

CONCLUSIONS

Both nonparametric and parametric approaches for DCE-MRI analysis possess the ability to quantify tissue perfusion.

The principal of dynamic contrast enhanced MRI, the method of pharmacokinetic analysis, and its application in the head and neck region

Many researchers have established the utility of the dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) in the differential diagnosis in the head and neck region, especially in the salivary gland tumors. The subjective assessment of the pattern of the time-intensity curve (TIC) or the simple quantification of the TIC, such as the time to peak enhancement (T_peak) and the wash-out ratio (WR), is commonly used. Although the semiquantitative evaluations described above have been widely applied, they do not provide information on the underlying pharmacokinetic analysis in tissue. The quantification of DCE-MRI is preferable; therefore, many compartment model analyses have been proposed. The Toft and Kermode (TK) model is one of the most popular compartment models, which provide information about the influx forward volume transfer constant from plasma into the extravascular-extracellular space (EES) and the fractional volume of EES per unit volume of tissue is used in many clinical studies. This paper will introduce the method of pharmacokinetic analysis and also describe the clinical application of this technique in the head and neck region.

Diagnostic Approaches to Sjögren's syndrome: a Literature Review and Own Clinical Experience

OBJECTIVES

The purpose of present paper is to critically address the recent advances on diagnostic procedures of Sjögren's syndrome, taking into account the attained local and systemic features of the disease.

MATERIAL AND METHODS

A comprehensive review of the available literature regarding to the diagnostic approaches to Sjögren's syndrome was conducted. Eligible studies were identified by searching the electronic literature PubMed, Medline, Embase, and ScienceDirect databases for relevant reports (last search update January 2012) combining the MESH heading term "Sjögren's syndrome", with the words "diagnosis, diagnostic procedures, salivary gland function, ocular tests, histopathology, salivary gland imaging, serology". The authors checked the references of the selected articles to identify additional eligible publications and contacted the authors, if necessary.

RESULTS

Presented article addresses the established diagnostic criteria for Sjögren's syndrome and critically evaluates the most commonly used diagnostic procedures, presenting data from author's own clinical experience. Diagnostic criteria for Sjögren's syndrome are required both by healthcare professionals and patients, namely in order to provide a rational basis for the assessment of the symptoms, establish an individual disease prognosis, and orientate the therapeutic intervention.

CONCLUSIONS

Sjögren's syndrome is quite a common autoimmune disease of which the diagnosis and treatment are not easily established. Due to its systemic involvement, it can exhibit a wide range of clinical manifestations that contribute to confusion and delay in diagnosis. The use of proper diagnostic modalities will help to reduce the time to diagnosis and preserve the health and quality of life of patients with Sjögren's syndrome.

Temporal resolution and SNR requirements for accurate DCE-MRI data analysis using the AATH model

Dynamic contrast-enhanced MRI has been used in conjunction with tracer kinetics modeling in a wide range of tissues for treatment monitoring, oncology drug development, and investigation of disease processes. Accurate measurement of model parameters relies on acquiring data with high temporal resolution and low noise, particularly for models with large numbers of free parameters, such as the adiabatic approximation to the tissue homogeneity model for separate measurements of blood flow and vessel permeability. In this simulation study, accuracy of the adiabatic approximation to the tissue homogeneity model was investigated, examining the effects of temporal resolution, noise levels, and error in the measured arterial input function. A temporal resolution of 1.5 s and high SNR (noise sd = 0.05) were found to ensure minimal bias (<5%) in all four model parameters (extraction fraction, blood flow, mean transit time, and extravascular extracellular volume), and the sampling interval can be relaxed to 6 s, if the transit time need not be measured accurately (bias becomes >10%). A 10% error in the measured height of the arterial input function first pass peak resulted in an error of at most 10% in each model parameter.

Oral involvement in primary Sjögren syndrome

BACKGROUND

In small studies, investigators have described oral features and their sequelae in primary Sjögren syndrome (PSS), but they have not provided a full picture of the aspects and implications of oral involvement. The authors describe what is, to their knowledge, the first large-scale evaluation to do so. In addition, they report data regarding utilization and cost of dental care among patients with PSS.

METHODS

The authors surveyed patients with primary Sjögren syndrome as identified by their physicians (PhysR-PSS), patient-members of the Sjögren's Syndrome Foundation (SSF-PSS) and control subjects who did not have PSS. They made comparisons between the three groups.

RESULTS

Subjects were 277 patients with PhysR-PSS, 1,225 patients with SSF-PSS and 606 control subjects. More than 96 percent of those in the patient groups experienced oral problems. An oral complaint was the initial symptom in more than one-half of the patients. Xerostomia-associated signs and symptoms were common and severe, as evidenced by scores on an inventory of sicca symptoms. These patients' rate of dental care utilization was high, and the care was costly.

CONCLUSIONS

Oral and dental disease in PSS is extensive and persistent and represents a significant burden of illness.

CLINICAL IMPLICATIONS

Oral symptoms and signs are common in patients with PSS. Early recognition of the significance of these findings by oral specialists could accelerate diagnosis and minimize oral morbidities.