Diffusion-weighted echo-planar MR imaging of primary parotid gland tumors: is a prediction of different histologic subtypes possible?

The value of combining conventional, diffusion-weighted and dynamic contrast-enhanced MR imaging for the diagnosis of parotid gland tumours

OBJECTIVES

The aim of this study was to determine the value of combining conventional MRI, diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE)-MRI in diagnosing solid neoplasms in the parotid gland.

METHODS

A total of 148 subjects (101 subjects with benign and 47 subjects with malignant tumours) were evaluated with conventional MRI, DWI and DCE-MRI prior to surgery and pathologic verification. The items observed with conventional MRI included the shape, capsule and signal intensity of parotid masses. The apparent diffusion coefficient (ADC) was calculated from DWI that was obtained with a b-factor of 0 and 1000 s mm^-2. A time-intensity curve (TIC) was obtained from DCE-MRI.

RESULTS

There were significant differences (p < 0.01) in the shape, capsule, ADC and TIC between benign and malignant parotid tumours. Irregular neoplasms without a capsule, ADC <1.12 × 10^-3 mm² s^-1 and a plateau enhancement pattern were valuable parameters for predicting malignant neoplasms. A combination of all of these parameters yielded sensitivity, specificity, accuracy, positive-predictive value and negative-predictive value of 85.1%, 94.1%, 91.2%, 87.0% and 93.1%, respectively.

CONCLUSIONS

A combined analysis using conventional MRI, DWI and DCE-MRI is helpful in distinguishing benign from malignant tumours in the parotid gland.

Feasibility study of reduced field of view diffusion-weighted magnetic resonance imaging in head and neck tumors

Background Reduced field of view (rFOV) imaging may be used to improve the quality of diffusion-weighted imaging (DWI) in the head and neck (HN) region. Purpose To evaluate the feasibility of rFOV-DWI in patients affected by HN tumors, through a comparison with conventional full FOV (fFOV) DWI. Material and Methods Twenty-two patients with histologically-proven malignant or benign tumors of the head and neck were included in a retrospective study. All patients underwent pre-treatment magnetic resonance imaging (MRI) studies including rFOV-DWI and fFOV-DWI. The apparent diffusion coefficient (ADC) value distributions inside tumor and muscle were derived and the mean, standard deviation (SD), and kurtosis were calculated. Image distortion was quantitatively and qualitatively evaluated, as well as the capability of lesion identification. The Wilcoxon test was used to compare all variables. Agreements between the ADC estimations were assessed by Bland-Altman plots. Results Image distortion and lesion identification scores were both higher for rFOV-DWI compared to fFOV-DWI. A reduction in ADC values with rFOV-DWI emerged for both lesion and muscle, with a mean percentage difference in ADC of 6.2% in the lesions and 24.9% in the muscle. The difference in SD of ADC was statistically significant in the lesions, indicating a higher ADC homogeneity for rFOV DWI ( P = 0.005). Conclusion The application of rFOV DWI in patients affected by HN tumors is feasible and promising, based on both qualitative and quantitative analyses. This technique has potential for improving the diagnostic accuracy of fFOV-DWI for the study of specific tumoral areas.

The added value of pretreatment DW MRI in characterization of salivary glands pathologies

OBJECTIVE

To evaluate the added value of diffusion weighted magnetic resonance imaging (DW-MRI) in characterization of salivary gland lesions.

STUDY DESIGN

A prospective study was carried out between January 2013, and March 2015.

METHODS

The study included 46 patients. The consultant radiologist, who reviewed the scans to comment on the apparent diffusion coefficient (ADC) value and ADC histogram was blind to the suspected pathology. Radiological findings were then compared to clinical and histological findings.

RESULTS

The diagnostic performance of DW-MRI for identification of malignant lesions showed that the sensitivity, specificity, and positive and negative prediction value were 100%, 92%, 91.3%, and 100%, respectively.

CONCLUSION

The specific ability of DW-MRI to probe tissue microstructures is an interesting complement to the currently used imaging procedures in the characterization, and even grading of malignancies. ADC mapping is an easy, cost effective promising tool that has neither radiation exposure, nor amalgam artifacts and can be used in helping characterization of salivary glands lesions.

LEVEL OF EVIDENCE

1B.

Diffusion-weighted MRI for differentiation between sialadenitis and pleomorphic adenoma

OBJECTIVES

The aim of this study was to compare apparent diffusion coefficient (ADC) values from diffusion-weighted MRI (DWI) among normal salivary glands, cases with sialadenitis and cases with pleomorphic adenoma of major salivary glands.

METHODS

22 patients (totalling 44 major salivary glands) diagnosed with either unilateral sialadenitis (on either parotid or submandibular gland) or parotid gland pleomorphic adenoma were selected. Contralateral non-affected glands (normal) were also analyzed. DW images were achieved using a spin-echo pulse sequence with a 1.5-T MRI device. Mean ADC values were compared among the three groups analyzed (contralateral normal glands, sialadenitis and pleomorphic adenoma).

RESULTS

The mean ADC values were significantly higher in cases of parotid sialadenitis (p = 0.001), but not in cases of submandibular sialadenitis (p = 0.466), as compared with the contralateral non-affected glands. Cases of pleomorphic adenoma presented the highest ADC values of the study. In addition, one-way ANOVA test revealed a significant difference among the three groups of parotid glands analyzed.

CONCLUSIONS

Within the limitations of this study, the present results suggest that DWI allows for differentiation between parotid sialadenitis and pleomorphic adenoma.

Evaluating Instantaneous Perfusion Responses of Parotid Glands to Gustatory Stimulation Using High-Temporal-Resolution Echo-Planar Diffusion-Weighted Imaging

BACKGROUND AND PURPOSE

Parotid glands secrete and empty saliva into the oral cavity rapidly after gustatory stimulation. However, the role of the temporal resolution of DWI in investigating parotid gland function remains uncertain. Our aim was to design a high-temporal-resolution echo-planar DWI pulse sequence and to evaluate the instantaneous MR perfusion responses of the parotid glands to gustatory stimulation.

MATERIALS AND METHODS

This prospective study enrolled 21 healthy volunteers (M/F = 2:1; mean age, 45.2 ± 12.9 years). All participants underwent echo-planar DWI (total scan time, 304 seconds; temporal resolution, 4 s/scan) on a 1.5T MR imaging scanner. T2WI (b = 0 s/mm²) and DWI (b = 200 s/mm²) were qualitatively assessed. Signal intensity of the parotid glands on T2WI, DWI, and ADC was quantitatively analyzed. One-way ANOVA with post hoc group comparisons with Bonferroni correction was used for statistical analysis. P < .05 was statistically significant.

RESULTS

Almost perfect interobserver agreement was achieved (κ ≥ 0.656). The parotid glands had magnetic susceptibility artifacts in 14.3% (3 of 21) of volunteers during swallowing on DWI but were free from perceptible artifacts at the baseline and at the end of scans on all images. Increased ADC and reduced signal intensity of the parotid glands on T2WI and DWI occurred immediately after oral administration of lemon juice. Maximal signal change of ADC (24.8% ± 10.8%) was significantly higher than that of T2WI (-10.1% ± 5.2%, P < .001). The recovery ratio of ADC (100.71% ± 42.34%) was also significantly higher than that of T2WI (22.36% ± 15.54%, P < .001).

CONCLUSIONS

Instantaneous parotid perfusion responses to gustatory stimulation can be quantified by ADC by using high-temporal-resolution echo-planar DWI.

Application of DTI and ARFI imaging in differential diagnosis of parotid tumours

OBJECTIVES

To explore the utility of diffusion tensor imaging (DTI) and acoustic radiation force impulse (ARFI) imaging in the diagnosis of parotid tumours.

METHODS

51 patients with parotid tumours were examined with DTI on 3.0-T MRI and ARFI imaging on an ultrasound scanner before surgery. Values of apparent diffusion coefficient (ADC), fractional anisotropy (FA) and shear-wave velocity (SWV) were calculated and analyzed with independent samples Wilcoxon-Mann-Whitney test. Cut-off values, sensitivity and specificity were calculated with receiver-operating characteristic (ROC) curve analysis. The value of combination was calculated through parallel test for the cut-off value of ADC, FA and SWV (combination = 0 or 1); then, ROC analysis was performed with pathological results as the gold standard to calculate the sensitivity and specificity for the combination of the three parameters distinguishing benign and malignant parotid tumours. Pathological diagnosis for every patient was made post-operatively from the tumour tissue taken during operation.

RESULTS

There was a significant difference between benign and malignant tumours in the values of ADC, FA and SWV (p = 0.032, p = 0.011 and p < 0.0001); a significant difference in the values was also found between pleomorphic adenoma and malignant tumour (p = 0.0012, p < 0.0001 and p = 0.0002). The diagnosis cut-off points between benign and malignant tumours for ADC, FA and SWV were 1.02 × 10(-3) mm(2) s(-1), 0.24 and 2.76 m s(-1), respectively; the sensitivity for ADC, FA and SWV was 87.50, 62.50 and 68.75%; the specificity was 45.71, 82.86 and 97.14%. Analysis of the combination of the three parameters increased the sensitivity, specificity, Youden index and area under the ROC curve compared with analysis of each parameter alone for distinguishing benign and malignant tumours.

CONCLUSIONS

The diagnostic value of the combination of the three parameters for distinguishing benign and malignant parotid tumours is the best; SWV is the preferred indicator. Parameters of DTI and ARFI may reflect the histological characteristics of parotid tumours and predict benignancy and malignancy and could provide quantitative information about the tumour. Combination of DTI with ARFI imaging had obvious advantage for the diagnosis of parotid tumours than each alone.

Benign neck masses showing restricted diffusion: Is there a histological basis for discordant behavior?

Diffusion weighted imaging (DWI) evolved as a complementary tool to morphologic imaging by offering additional functional information about lesions. Although the technique utilizes movement of water molecules to characterize biological tissues in terms of their cellularity, there are other factors related to the histological constitution of lesions which can have a significant bearing on DWI. Benign lesions with atypical histology including presence of lymphoid stroma, inherently increased cellularity or abundant extracellular collagen can impede movement of water molecules similar to malignant tissues and thereby, show restricted diffusion. Knowledge of these atypical entities while interpreting DWI in clinical practice can avoid potential misdiagnosis. This review aims to present an imaging spectrum of such benign neck masses which, owing to their distinct histology, can show discordant behavior on DWI.

Parotid gland lesions: separate and combined diagnostic value of conventional MRI, diffusion-weighted imaging and dynamic contrast-enhanced MRI

OBJECTIVE

To evaluate the ability of conventional MRI, diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) MRI to differentiate malignant and benign parotid lesions.

METHODS

A retrospective review of MRI findings was performed in patients with pathologically confirmed parotid lesions between January 2010 and December 2014. Morphological MRI characteristics and functional characteristics such as apparent diffusion coefficient (ADC) and pattern of time-signal intensity curve (TIC) were recorded and compared. For each lesion, summed scores were respectively calculated for conventional MRI alone, conventional MRI with DWI and/or with DCE-MRI. Statistical analyses were performed to assess the association of these characteristics and summed scores with malignancy.

RESULTS

A total of 207 patients (111 males and 96 females; age: 48.4 ± 17.0 years) were included, consisting of 156 benign and 51 malignant tumours. After adjusting for age, sex, smoking status, alcohol use and tumour size, the lesions with ill-defined margin, adjacent tissue infiltration, cervical lymphadenopathy, ADC ≤1.01 × 10(-3) mm(2) s(-1) and plateau TIC pattern are more likely to be malignant than those without these findings. Significant difference in receiver operator characteristic was detected after adding DWI to conventional MRI (p = 0.003), generating a sensitivity and specificity of 54.05% and 91.30%, respectively. Compared with lesions score <3, lesions with score ≥5 in the combination of conventional MRI and DWI were approximately 90 times more likely to be malignant parotid tumour. Additional DCE-MRI did not improve differential ability of conventional MRI.

CONCLUSION

Morphological and functional MRI characteristics are associated with malignancy in parotid gland. The diagnostic value of MRI would increase when DWI is applied in combination with conventional MRI.

ADVANCES IN KNOWLEDGE

The parotid lesions with ill-defined margin, adjacent tissue infiltration, cervical lymphadenopathy, ADC ≤1.01 × 10(-3) mm(2) s(-1) and plateau TIC pattern are more likely to be malignant. The diagnostic value of conventional MRI would be increased when DWI is applied in combination, whereas additional DCE-MRI did not improve differential ability of conventional MRI.

Preoperative Diagnostic Strategy for Parotid Gland Tumors Using Diffusion-Weighted MRI and Technetium-99m Pertechnetate Scintigraphy: A Prospective Study

Objective

Fine needle aspiration cytology (FNAC) for diagnosis of a parotid gland tumor is widely used but its sensitivity is low and non-diagnostic rate is relatively high. In contrast, core needle biopsy (CNB) has a higher sensitivity and lower rate of sampling errors but has a higher risk of injury to adjacent organs such as facial nerve than FNAC. Screening of patients with parotid gland tumors to identify cases of pleomorphic adenoma (PA) and Warthin tumor (WT) may allow CNB to be confined to patients without PA and WT. We established an algorithm for preoperative diagnosis and management of parotid gland tumor using diffusion-weighted MRI and ^99mTc pertechnetate scintigraphy. This algorithm was developed with the goal of maximal reduction of the number of patients in whom CNB is required. The purpose of the study is to validate our algorithm prospectively.

Methods

A prospective study was conducted in 71 cases who were newly diagnosed with parotid gland tumor and 53 cases were enrolled in the study. In the algorithm, PA (high apparent diffusion coefficient (ADC) _mean≥1.5×10⁻³ mm²/s) and non-PA (low ADC_mean<1.5×10⁻³ mm²/s) cases are first distinguished based on the ADC_mean on diffusion-weighed MRI. Second, among suspected non-PA cases, WT and non-WT are distinguished using technetium-99m pertechnetate scintigraphy. CNB is then performed only in probable non-PA and non-WT cases.

Results

Although CNB was only required in 40% (21/53) of all cases, we made a preoperative histopathological diagnosis with an accuracy of 87% (46/53) and we correctly diagnosed whether a tumor was benign or malignant with an accuracy of 96% (51/53). Preoperative surgical planning had to be changed during surgery in only one case (2%)

Conclusions

Our algorithm is valuable in terms of clinical practice with highly potential for preoperative diagnosis and with less risk of CNB procedure.

Orbital tumours and tumour-like lesions: exploring the armamentarium of multiparametric imaging

Although the orbit is a small anatomical space, the wide range of structures present within it are often the site of origin of various tumours and tumour-like conditions, both in adults and children. Cross-sectional imaging is mandatory for the detection, characterization, and mapping of these lesions. This review focuses on multiparametric imaging of orbital tumours. Each tumour is reviewed in relation to its clinical presentation, compartmental location, imaging characteristics, and its histological features. We herein describe orbital tumours as lesions of the globe (retinoblastoma, uveal melanoma), optic nerve sheath complex (meningioma, optic nerve glioma), conal-intraconal compartment (hemangioma), extraconal compartment (dermoid/epidermoid, lacrimal gland tumours, lymphoma, rhabdomysarcoma), and bone and sinus compartment (fibrous dysplasia). Lesions without any typical compartmental localization and those with multi-compartment involvement (veno-lymphatic malformation, plexiform neurofibroma, idiopathic orbital pseudotumour, IgG4 related disease, metastases) are also reviewed. We discuss the role of advanced imaging techniques, such as MR diffusion-weighted imaging (DWI), diffusion tensor imaging, fluoro-2-deoxy-D-glucose positron emission tomography CT (FDG-PET CT), and positron emission tomography MRI (MRI PET) as problem-solving tools in the evaluation of those orbital masses that present with non-specific morphologic imaging findings. Main messages/Teaching points • A compartment-based approach is essential for the diagnosis of orbital tumours. • CT and MRI play a key role in the work-up of orbital tumours. • DWI, PET CT, and MRI PET are complementary tools to solve diagnostic dilemmas. • Awareness of salient imaging pearls and diagnostic pitfalls avoids interpretation errors.

Dynamic Contrast Magnetic Resonance Imaging (DCE-MRI) and Diffusion Weighted MR Imaging (DWI) for Differentiation between Benign and Malignant Salivary Gland Tumors

BACKGROUND

Salivary gland tumors form nearly 3% of head and neck tumors. Due to their large histological variety and vicinity to facial nerves, pre-operative diagnosis and differentiation of benign and malignant parotid tumors are a major challenge for radiologists.

OBJECTIVE

The majority of these tumors are benign; however, sometimes they tend to transform into a malignant form. Functional MRI techniques, namely dynamic contrast enhanced (DCE-) MRI and diffusion-weighted MRI (DWI) can indicate the characteristics of tumor tissue.

METHODS

DCE-MRI analysis is based on the parameters of time intensity curve (TIC) before and after contrast agent injection. This method has the potential to identify the angiogenesis of tumors. DWI analysis is performed according to diffusion of water molecules in a tissue for determination of the cellularity of tumors.

CONCLUSION

According to the literature, these methods cannot be used individually to differentiate benign from malignant salivary gland tumors. An effective approach could be to combine the aforementioned methods to increase the accuracy of discrimination between different tumor types. The main objective of this study is to explore the application of DCE-MRI and DWI for assessment of salivary gland tumor types.

Improved performance in differentiating benign from malignant sinonasal tumors using diffusion-weighted combined with dynamic contrast-enhanced magnetic resonance imaging

Background:

Differentiating benign from malignant sinonsal lesions is essential for treatment planning as well as determining the patient's prognosis, but the differentiation is often difficult in clinical practice. The study aimed to determine whether the combination of diffusion-weighted (DW) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can improve the performance in differentiating benign from malignant sinonasal tumors.

Methods:

This retrospective study included 197 consecutive patients with sinonasal tumors (116 malignant tumors and 81 benign tumors). All patients underwent both DW and DCE-MRI in a 3-T magnetic resonance scanner. Two different settings of b values (0,700 and 0,1000 s/mm²) and two different strategies of region of interest (ROI) including whole slice (WS) and partial slice (PS) were used to calculate apparent diffusion coefficients (ADCs). A DW parameter with WS ADCs_b0,1000 and two DCE-MRI parameters (time intensity curve [TIC] and time to peak enhancement [Tpeak]) were finally combined to use in differentiating the benign from the malignant tumors in this study.

Results:

The mean ADCs of malignant sinonasal tumors (WS ADCs_b0,1000 = 1.084 × 10⁻³ mm²/s) were significantly lower than those of benign tumors (WS ADCs_b0,1000 = 1.617 × 10⁻³ mm²/s, P < 0.001). The accuracy using WS ADCs_b0,1000 alone was 83.7% in differentiating the benign from the malignant tumors (85.3% sensitivity, 81.2% specificity, 86.4% positive predictive value [PPV], and 79.5% negative predictive value [NPV]). The accuracy using DCE with Tpeak and TIC alone was 72.1% (69.1% sensitivity, 74.1% specificity, 77.5% PPV, and 65.1% NPV). Using DW-MRI parameter was superior than using DCE parameters in differentiation between benign and malignant sinonasal tumors (P < 0.001). The accuracy was 87.3% (90.5% sensitivity, 82.7% specificity, 88.2% PPV, and 85.9% NPV) using DW-MRI combined with DCE-MRI, which was superior than that using DCE-MRI alone or using DW-MRI alone (both P < 0.001) in differentiating the benign from the malignant tumors.

Conclusions:

Diffusion-weighted combined with DCE-MRI can improve imaging performance in differentiating benign from malignant sinonasal tumors, which has the potential to improve diagnostic accuracy and to provide added value in the management for these tumors.

Early detection of pulp necrosis and dental vitality after traumatic dental injuries in children and adolescents by 3-Tesla magnetic resonance imaging

OBJECTIVES

More than 50% of all children suffer a traumatic dental injury (TDI) during childhood. In many cases, dentists apply root canal treatment (RCT), which is performed on an average of 7-10 days after replantation. Our aim was to evaluate whether RCT is necessary in many cases, and whether revitalization of affected teeth is possible and measurable by visualization using 3T magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Seven healthy children with TDI were treated by repositioning of the affected teeth and reduction of alveolar process fractures followed by splinting. Two weeks after initial treatment, splints were removed. After 6 weeks, all children received 3-Tesla (3T), three-dimensional, high-resolution MRI with a 20-channel standard head and neck coil. The mean age of the children (male/female = 5:2) was 10.8 years (range, 8-17 years). In addition, all children received conventional dental examination for tooth vitality and dental sensitivity to cold and tenderness on percussion.

RESULTS

3T MRI provided excellent images that allowed fine discrimination between dental pulp and adjacent tooth. Using four in-house optimized, non-contrast-enhanced sequences, including panoramic reconstruction, the assessment and analysis of the dental pulp was sufficiently feasible. We could demonstrate reperfusion and thus vitality of the affected teeth in 11 sites. In one child, MRI was able to detect nonreperfusion after TDI of the affected tooth. MRI results were confirmed by clinical examination in all cases. As a consequence of this expectant management and proof of reperfusion and tooth vitality by 3T MRI, only one child had to be treated by RCT.

CONCLUSION

3T MRI is a very promising tool for visualization and detection in the field of dental and oromaxillofacial diseases. By using new 3T MRI sequences in children with TDI, we could demonstrate that RCT are not necessary in every case, and thus could prevent unnecessary treatment of children in the future. Larger studies should follow to confirm the potential benefit in clinical practice.

Utility of apparent diffusion coefficient in characterization of different sinonasal pathologies

BACKGROUND

Sinonasal lesions are a heterogeneous group of lesions that span from a tumor to tumor-like nature. Characterization of such cases preoperatively can improve the surgical control and the overall outcome of these patients.

OBJECTIVE

In this prospective study, we aimed at evaluation of the role of apparent diffusion coefficient (ADC) in the differentiation between benign and malignant sinonasal lesions.

SUBJECTS AND METHODS

All patients scheduled to have sinonasal surgical intervention at Ain Shams University Hospitals, Cairo, Egypt, were enrolled. Diffusion-weighted (DW) magnetic resonance imaging (MRI) with calculation of ADC were done for all cases. Radiologic findings were then compared with histologic findings, and the sensitivity, specificity, negative and positive predictive values (PPVs) of the conventional MRI, DW-MRI, and ADC value in differentiation of benign from malignant sinonasal lesions were then calculated.

RESULTS

There were 59 patients with median age of 43 years old. There were 20 cases of inflammatory lesions, 16 cases of benign tumors, and 23 cases of malignant lesions. The ADC values of all cases ranged from 0.4 × 10(-3) to 2 × 10(-3) (median = 1.5 × 10(-3)). The median ADC value for the malignant lesions was 0.6 × 10(-3), whereas that for the inflammatory conditions was 1.6 × 10(-3) and that for the benign tumors was 1.5 × 10(-3) with a highly significant difference (p < .001). Analysis of the conventional MRI and DW-MRI to differentiate between malignant and benign lesions showed that the sensitivity, specificity, PPV, and negative predictive value (NPV) were 100%, 97%, 96%, and 100% and 91%, 97%, 95%, and 95%, respectively.

CONCLUSION

DW-MRI did not add significantly to the information gained from conventional MRI. It should be considered complimentary only to standard MRI in uncertain cases when malignancy is still a concern.

The application of dynamic contrast-enhanced MRI and diffusion-weighted MRI in patients with maxillofacial tumors

RATIONALE AND OBJECTIVES

To elucidate the characteristics of four types of tumors, including squamous cell carcinoma (SCC), malignant lymphoma (ML), malignant salivary gland tumors (MSGTs), and pleomorphic adenoma (Pleo), in the maxillofacial region using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted MRI (DW-MRI）data.

MATERIALS AND METHODS

A total of 59 tumors were included in this research. DCE-MRI and DW-MRI were performed. We applied the Tofts and Kermode model (TK model) for the DCE-MRI data and obtained three dependent parameters: the influx forward volume transfer constant into the extravascular extracellular space from the plasma (K(trans)), the fractional volume of extravascular extracellular space per unit volume of tissue (ve), and the fractional volume of plasma (vp).

RESULTS

Among the K(trans) values, there were no significant differences between the three types of malignant tumors; however, there was a significant difference between the SCC and Pleo (P = .0099). The ve values of the Pleo were highest, with significant differences compared to the other categories (SCC, P = .0012; ML, P = .0017; and MSGT, P = .041). The ML had the lowest ve values, and there were significant differences between ML and the other two types of malignant tumors (SCC, P = .0278 and MSGT, P = .0062). In 14 (24%) cases, apparent diffusion coefficient (ADC) could not be measured because of poor image quality. The ADC values of the ML were lowest, whereas those of Pleo were highest, similar to that observed for ve.

CONCLUSIONS

The Pleo tumors had lower K(trans) values and higher ve values, which are useful for differentiating them from the malignant tumors. Moreover, the ve was also useful for establishing a diagnosis of ML.

MRI criteria for the diagnosis of pleomorphic adenoma: a validation study

OBJECTIVES

To validate an MRI algorithm characteristic of pleomorphic adenoma (PA).

STUDY DESIGN

Cross-sectional analysis.

SETTING

Academic tertiary-care medical center.

METHODS

A radiologic algorithm for the MRI diagnosis of PA was developed on the basis of five "high probability" criteria that all must be fulfilled for the MRI to qualify as a positive test result: bright T2-signal, sharp margins, heterogeneous nodular enhancement, lobulated contours, T2-dark rim. We then identified MRI images from our institutional database to test the diagnostic accuracy of the proposed algorithm.

RESULTS

A total of 103 parotidectomy cases with adequate MRI studies were identified (pleomorphic adenoma n=41, mucoepidermoid carcinoma n=11, Warthin's tumor n=8, adenoid cystic carcinoma n=6, oncocytoma n=6, acinic cell carcinoma n=5, salivary duct carcinoma n=5, and other n=21). Eighteen of 21 cases that met all five "high probability" MRI criteria were consistent with PA on final histopathology; 3 were consistent with carcinoma. MRI had a specificity of 95.1% [95% confidence interval: 85.6-98.7%] and sensitivity of 43.9% [95% C.I.: 28.8-60.1%] for PA. The positive predictive value was 85.7% [95% C.I.: 70.4-100%] and the negative predictive value was 71.9% [95% C. I.: 62.0-81.9%]. The overall diagnostic accuracy was 74.8% [95% C.I.: 66.2-83.3%].

CONCLUSION

A "high probability" MRI is about 95% specific for pleomorphic adenoma. A subset of patients with MRI imaging that is highly suggestive of PA may reliably avoid further workup. The value of MRI in this setting is especially useful if preoperative fine needle aspiration is not readily available. A significant proportion of PAs, however, have indeterminate imaging features that overlap considerably with other benign and malignant lesions.

The role of diffusion-weighted magnetic resonance imaging in the diagnosis, lymph node staging and assessment of treatment response of head and neck cancer

Standard magnetic resonance imaging (MRI) and computed tomography continue to be the imaging modalities of choice in staging and reviewing patients with head and neck cancer. Diffusion-weighted MRI (DW-MRI) is an advanced imaging modality that records the molecular diffusion of protons and thus provides an opportunity to further assess tissue character. Interest in DW-MRI of the head and neck continues to grow, especially its application to the assessment and treatment of head and neck cancer. We highlight the potential role of DW-MRI in the delineation, characterization, and lymph node staging of head and neck tumours. Furthermore, we discuss the ability of DW-MRI to provide a real opportunity to differentiate post-treatment tumour recurrence from chemoradiotherapy-induced local tissue changes. The future impact of these findings upon the clinical practice of the head and neck surgeon is discussed.

Salivary gland tumors of the parotid gland: CT and MR imaging findings with emphasis on intratumoral cystic components

INTRODUCTION

The purpose of this study was to assess computed tomography (CT) and magnetic resonance (MR) imaging findings of salivary gland tumors of the parotid gland with emphasis on intratumoral cystic components.

METHODS

Seventy-two histopathologically confirmed salivary gland tumors of the parotid gland (44 benign and 28 malignant), which underwent both CT and MR imaging including contrast-enhanced study, were included in this study. We retrospectively reviewed images for the presence, number, occupying rate, margin characteristics, distribution, and predominant MR signal intensity of intratumoral cystic components.

RESULTS

The prevalence of cystic components was greater in malignant than benign tumors (79 vs. 50%, p < 0.05). The number and occupying rate were similar between benign and malignant tumors. The irregular margins were more frequent in malignant than benign tumors (73 vs. 27%, p < 0.01). The frequency of eccentric location was greater in benign than malignant tumors (91 vs. 55%, p < 0.01), whereas the frequency of centric location was greater in malignant than benign tumors (32 vs. 0%, p < 0.01). On T1-weighted images, the frequency of hyperintensity was greater in benign than malignant tumors (50 vs. 9%, p < 0.01), whereas that of isointensity was greater in malignant than benign tumors (50 vs. 0%, p < 0.01). Multiple logistic regression analysis showed that the absence of irregular margins of cystic components only was significantly correlated with the presence of benign salivary gland tumors (p < 0.01).

CONCLUSION

Imaging features of intratumoral cystic components may help to differentiate benign from malignant tumors of the parotid salivary gland.

Facial Nerve Paralysis due to a Pleomorphic Adenoma with the Imaging Characteristics of a Facial Nerve Schwannoma

Background Facial nerve paralysis in a patient with a salivary gland mass usually denotes malignancy. However, facial paralysis can also be caused by benign salivary gland tumors.

Methods We present a case of facial nerve paralysis due to a benign salivary gland tumor that had the imaging characteristics of an intraparotid facial nerve schwannoma.

Results The patient presented to our clinic 4 years after the onset of facial nerve paralysis initially diagnosed as Bell palsy. Computed tomography demonstrated filling and erosion of the stylomastoid foramen with a mass on the facial nerve. Postoperative histopathology showed the presence of a pleomorphic adenoma. Facial paralysis was thought to be caused by extrinsic nerve compression.

Conclusions This case illustrates the difficulty of accurate preoperative diagnosis of a parotid gland mass and reinforces the concept that facial nerve paralysis in the context of salivary gland tumors may not always indicate malignancy.

Evaluation of four different optimized magnetic-resonance-imaging sequences for visualization of dental and maxillo-mandibular structures at 3 T

OBJECTIVES

The purpose of this study was to evaluate four in-house optimized, non-contrast enhanced sequences for MRI-investigation of maxillo-mandibular and dental structures by use of 3 T.

METHODS

12 volunteers with different dental status were examined by using a 3 T MRI with a 20-channel standard head-and-neck coil. All images performed were evaluated by using 3D-techniques, with different slice-thicknesses, in 3D T1- and T2-weighted sequences, as well as by using new techniques of image depictions. In addition phantom measurements were performed to estimate the extent of image artefacts caused by retainers and metal implants.

RESULTS

Mean age of the participants was 33 years (range, 25.5-62.75 years), and the sex ratio was 5 females to 7 males. We identified different techniques to improve osseous and dental structures, despite problems caused by dental implants, tooth crowns or braces.

CONCLUSION

The sequences evaluated offered excellent visualization in 2D and 3D of osseous and dental structures. Anatomical, osseous and dental structures were described at their ROI, in relation to patients with dental and head and neck pathologies. The ability to detect and distinguish pathological processes as soon as possible in 3D with excellent image quality avoiding ionizing radiation remains a challenging domain.

[Radiation therapy for pleomorphic adenoma of the parotid]

Parotid pleomorphic adenoma is the most frequent tumor of salivary glands. The prognosis depends on the recurrences because they could lead to iatrogenic events (facial paralysis). Moreover the risk of malignant transformation increases with the number of local relapses. This article aims at reviewing histological and radiological criteria and the surgical techniques. To improve local control, adjuvant irradiation (in first intention or after recurrence) may be useful but is still controversial for benign tumors in young patients with a risk of radio-induced cancer. We listed studies in which adjuvant radiotherapy was used so as to define its place in the treatment strategy. Prognostic factors were found by some authors. Other studies have to be done before strong evidence-based recommendations are issued.

Texture-based and diffusion-weighted discrimination of parotid gland lesions on MR images at 3.0 Tesla

The purpose of this study was to evaluate whether texture-based analysis of standard MRI sequences and diffusion-weighted imaging can help in the discrimination of parotid gland masses. The MR images of 38 patients with a biopsy- or surgery-proven parotid gland mass were retrospectively analyzed. All patients were examined on the same 3.0 Tesla MR unit, with one standard protocol. The ADC (apparent diffusion coefficient) values of the tumors were measured with three regions of interest (ROIs) covering the entire tumor. Texture-based analysis was performed with the texture analysis software MaZda (version 4.7), with ROI measurements covering the entire tumor in three slices. COC (co-occurrence matrix), RUN (run-length matrix), GRA (gradient), ARM (auto-regressive model), and WAV (wavelet transform) features were calculated for all ROIs. Three subsets of 10 texture features each were used for a linear discriminant analysis (LDA) in combination with k nearest neighbor classification (k-NN). Using histology as a standard of reference, benign tumors, including subtypes, and malignant tumors were compared with regard to ADC and texture-based values, with a one-way analysis of variance with post-hoc t-tests. Significant differences were found in the mean ADC values between Warthin tumors and pleomorphic adenomas, as well as between Warthin tumors and benign lesions. Contrast-enhanced T1-weighted images contained the most relevant textural information for the discrimination between benign and malignant parotid masses, and also for the discrimination between pleomorphic adenomas and Warthin tumors. STIR images contained the least relevant texture features, particularly for the discrimination between pleomorphic adenomas and Warthin tumors. Texture analysis proved to differentiate benign from malignant lesions, as well as pleomorphic adenomas from Warthin tumors, based on standard T(1w) sequences (without and with contrast). Of all benign parotid masses, Warthin tumors had significantly lower ADC values than the other entities.

Different histological subtypes of parotid gland tumors: CT findings and diagnostic strategy

AIM: To present computed tomography (CT) findings of different histological subtypes of parotid gland masses in detail and to establish diagnostic strategy.

METHODS: From January 2009 to November 2011, 56 patients were collected through the histopathology and Picture Archiving and Communication Systems records, which revealed 5 basal cell adenoma (BCA), 16 pleomorphic adenoma (PA), 25 Warthin’s tumor (War-T), 3 Kimura’s disease (KD) and 7 parotid carcinoma (PCa) cases. All the CT images were retrospectively analyzed by two radiologists in consensus, based on their description of morphology (location, number, size, margin and fibrous capsule) and enhancement patterns of masses. In addition, the diagnostic efficiency of diagnostic strategy is tested.

RESULTS: War-T and BCA patients’ mean age was 59.9 ± 12.6 years and 58.4 ± 18.2 years; the significant difference was seen in War-T vs PA and BCA vs PA. About 40% of War-Ts presented with bilateral multifocal lesions, a higher ratio than others. Seventy two percent of War-Ts were limited to the superficial lobe, followed by BCA 60% and PA 40%. Vessel facing sign and enlarged lymph nodes were both frequent in War-T, which respectively accounts for 84% and 76% of cases. Rapid contrast enhancement and decreases were unique for War-T. BCA and PA showed obvious delayed enhancement. The diagnostic strategy of parotid gland tumor had a good diagnostic efficiency, with high accuracy, sensitivity and specificity.

CONCLUSION: Determination of the histological subtypes of parotid gland masses might be possible based on CT findings and clinical data. A diagnostic strategy with high diagnostic efficiency was established.

Parotid perfusion in nasopharyngeal carcinoma patients in early-to-intermediate stage after low-dose intensity-modulated radiotherapy: evaluated by fat-saturated dynamic contrast-enhanced magnetic resonance imaging

PURPOSE

To investigate parotid perfusion in early-to-intermediate stage after parotid-sparing radiation dose using fat-saturated DCE-MRI, and to verify whether the perfusion alteration was related to radiation dose and the PSV.

METHODS AND MATERIALS

Thirty-two parotid glands from 16 consecutive patients with pathologically proven nasopharyngeal carcinoma treated by IMRT were examined. The parotid glands received a radiation dose of 28.9±3.9Gy with a PSV of 43.1%±13.9%. Perfusion parameters were calculated using time-shifted Brix model from fat-saturated DCE-MRI data before (pre-RT) and in early-to-intermediate stage after (post-RT) IMRT. Paired t-test was used to evaluate perfusion changes, while Pearson's correlation test was used to examine perfusion dependency on radiation dose and PSV. For multiple comparisons Bonferroni correction was applied.

RESULTS

Successful fat saturation was achieved in 29 of 32 parotid glands. Compared with pre-RT, the post-RT parotid glands showed significantly higher A, peak enhancement, and wash-in slope, plus a lower Kel, suggesting a mixed effect of increased vascular permeability and acinar loss. Linear regression showed that peak enhancement was positively associated with radiation dose in post-RT parotid glands. Kel and slope were negatively associated with PSV, while time-to-peak was positively associated with PSV significantly.

CONCLUSIONS

Our results suggest that time-shifted Brix model is feasible for quantifying parotid perfusion using DCE-MRI. The perfusion alterations in early-to-intermediate stage after IMRT might be related to a mixed effect of increased vascular permeability and acinar loss with dose and PSV dependencies.

Salivary gland carcinomas

INTRODUCTION

Salivary gland carcinomas are rare tumours of heterogeneous morphology that require distinctive surgical and adjuvant therapy.

METHODS

Relevant studies were electronically searched in PubMed and reviewed for innovative and important information.

RESULTS

Recent insights in genetic alterations like chromosomal aberrations, expression of receptor tyrosine kinases, malfunction of tumour suppressor genes or DNA promoter methylations increased the knowledge about aetiology and pathogenesis. New histological subtypes are recognised, and a three-tiered grading system seems reasonable. Ultrasound remains the basic diagnostic imaging procedure. New developments comprise the diffusion-weighed magnetic resonance imaging, while fluorodeoxyglucose positron emission tomography/computed tomography shows good diagnostic accuracy in detecting distant metastases and local recurrence. Fine-needle aspiration cytology helps in differentiating a neoplasia from a non-neoplastic lesion while being unreliable in recognising malignancy. In contrast, additional core needle biopsy and/or intraoperative frozen section diagnosis increase the accuracy in diagnosing a malignant lesion. Conservative parotid surgery with nerve monitoring remains state-of-the-art. Free flaps or musculoaponeurotic flaps are proposed for prevention of Frey's syndrome. As parotid cancer often shows skip metastases, complete ipsilateral neck dissection (level I-V) is indicated particularly in high-grade lesions. Adjuvant radio(chemo)therapy increases local tumour control, whereas overall survival is not necessarily improved. Current results of systemic chemotherapy or targeted therapy in advanced tumour stages are disappointing.

CONCLUSION

Despite several developments, salivary gland carcinomas remain a heterogeneous group of tumours challenging both pathologists and clinicians.

Head and neck tumors: assessment of perfusion-related parameters and diffusion coefficients based on the intravoxel incoherent motion model

BACKGROUND AND PURPOSE

IVIM MR imaging provides perfusion and diffusion information with a single diffusion-weighted MR image. We determined whether PP and D differ among various types of head and neck tumors.

MATERIALS AND METHODS

The study cohort included 123 head and neck tumors: 30 SCCs, 28 benign and 20 malignant SG tumors, 36 lymphomas, and 9 schwannomas. The D and PP values were determined by using b-values of 0, 500, and 1000 s/mm(2) based on the IVIM model.

RESULTS

The PP values (lymphomas, 0.09 ± 0.04; SCCs, 0.15 ± 0.04; and malignant SG tumors, 0.22 ± 0.07) and D values (0.47 ± 0.07 × 10(-3) mm(2)/s, 0.82 ± 0.17 × 10(-3) mm(2)/s, and 1.03 ± 0.16 × 10(-3) mm(2)/s, respectively) were significantly different among the malignant tumors (P < .01). These values were also significantly different between pleomorphic adenomas (0.13 ± 0.02 and 1.44 ± 0.39 × 10(-3) mm(2)/s) and Warthin tumors (0.19 ± 0.04 and 0.73 ± 0.22 × 10(-3) mm(2)/s) (P < .001). The PP values of malignant SG tumors were significantly different from those of pleomorphic adenomas (P = .001) and the D values of the malignant SG tumors were significantly different from those of pleomorphic adenomas (P = .002) and Warthin tumors (P = .007). Schwannomas had large PP (0.23 ± 0.08) and D values (1.26 ± 0.20 × 10(-3) mm(2)/s), greatly overlapping those of some SG tumor types.

CONCLUSIONS

Head and neck tumors had distinctive PP and D values by using IVIM MR imaging.

Apparent diffusion coefficient measurements in the differentiation between benign and malignant lesions: a systematic review

Objectives

To systematically review the value of apparent diffusion coefficient (ADC) measurement in the differentiation between benign and malignant lesions.

Methods

A systematic search of the Medline/Pubmed and Embase databases revealed 109 relevant studies. Quality of these articles was assessed using the Quality Assessment of the Studies of Diagnostic Accuracy Included in Systematic Reviews (QUADAS) criteria. Reported ADC values of benign and malignant lesions were compared per organ.

Results

The mean quality score of the reviewed articles was 50%. Comparison of ADC values showed marked variation among studies and between benign and malignant lesions in various organs. In several organs, such as breast, liver, and uterus, ADC values discriminated well between benign and malignant lesions. In other organs, such as the salivary glands, thyroid, and pancreas, ADCs were not significantly different between benign and malignant lesions.

Conclusion

The potential utility of ADC measurement for the characterisation of tumours differs per organ. Future well-designed studies are required before ADC measurements can be recommended for the differentiation of benign and malignant lesions. These future studies should use standardised acquisition protocols and provide complete reporting of study methods, to facilitate comparison of results and clinical implementation of ADC measurement for tumour characterisation.

Electronic supplementary material

The online version of this article (doi:10.1007/s13244-012-0175-y) contains supplementary material, which is available to authorized users.