Parotid masses: prediction of malignancy using magnetization transfer and MR imaging findings

Amide proton transfer (APT) and magnetization transfer (MT) in predicting short-term therapeutic outcome in nasopharyngeal carcinoma after chemoradiotherapy: a feasibility study of three-dimensional chemical exchange saturation transfer (CEST) MRI

BACKGROUND

The three-dimensional chemical exchange saturation transfer (3D CEST) technique is a novel and promising magnetic resonance sequence; however, its application in nasopharyngeal carcinoma (NPC) lacks sufficient evaluation. This study aimed to assess the feasibility of the 3D CEST technique in predicting the short-term treatment outcomes for chemoradiotherapy (CRT) in NPC patients.

METHODS

Forty NPC patients and fourteen healthy volunteers were enrolled and underwent the pre-treatment 3D CEST magnetic resonance imaging and diffusion-weighted imaging (DWI). The reliability of 3D CEST was assessed in healthy volunteers by calculating the intra- and inter-observer correlation coefficient (ICC) for amide proton transfer weighted-signal intensity (APTw-SI) and magnetization transfer ratio (MTR) values. NPC patients were divided into residual and non-residual groups based on short-term treatment outcomes after CRT. Whole-tumor regions of interest (ROIs) were manually drawn to measure APTw-SI, MTR and apparent diffusion coefficient (ADC) values. Multivariate analysis and the receiver operating characteristic curve (ROC) were used to evaluate the prediction performance of clinical characteristics, APTw-SI, MTR, ADC values, and combined models in predicting short-term treatment outcomes in NPC patients.

RESULTS

For the healthy volunteer group, all APTw-SI and MTR values exhibited good to excellent intra- and inter-observer agreements (0.736-0.910, 0.895-0.981, all P > 0.05). For NPC patients, MTR values showed a significant difference between the non-residual and residual groups (31.24 ± 5.21% vs. 34.74 ± 1.54%, P = 0.003) while no significant differences were observed for APTw-SI and ADC values (P > 0.05). Moreover, the diagnostic power of MTR value was superior to APTw-SI (AUC: 0.818 vs. 0.521, P = 0.017) and comparable to ADC values (AUC: 0.818 vs. 0.649, P > 0.05) in predicting short-term treatment outcomes for NPC patients. The prediction performance did not improve even when combining MTR values with APTw-SI and/or ADC values (P > 0.05).

CONCLUSIONS

The pre-treatment MTR value acquired through 3D CEST demonstrated superior predictive performance for short-term treatment outcomes compared to APTw-SI and ADC values in NPC patients after CRT.

MRI-Based radiomics nomogram for differentiation of benign and malignant lesions of the parotid gland

OBJECTIVES

Preoperative differentiation between benign parotid gland tumors (BPGT) and malignant parotid gland tumors (MPGT) is important for treatment decisions. The purpose of this study was to develop and validate an MRI-based radiomics nomogram for the preoperative differentiation of BPGT from MPGT.

METHODS

A total of 115 patients (80 in training set and 35 in external validation set) with BPGT (n = 60) or MPGT (n = 55) were enrolled. Radiomics features were extracted from T1-weighted and fat-saturated T2-weighted images. A radiomics signature model and a radiomics score (Rad-score) were constructed and calculated. A clinical-factors model was built based on demographics and MRI findings. A radiomics nomogram model combining the Rad-score and independent clinical factors was constructed using multivariate logistic regression analysis. The diagnostic performance of the three models was evaluated and validated using ROC curves on the training and validation datasets.

RESULTS

Seventeen features from MR images were used to build the radiomics signature. The radiomics nomogram incorporating the clinical factors and radiomics signature had an AUC value of 0.952 in the training set and 0.938 in the validation set. Decision curve analysis showed that the nomogram outperformed the clinical-factors model in terms of clinical usefulness.

CONCLUSIONS

The above-described radiomics nomogram performed well for differentiating BPGT from MPGT, and may help in the clinical decision-making process.

KEY POINTS

• Differential diagnosis between BPGT and MPGT is rather difficult by conventional imaging modalities. • A radiomics nomogram integrated with the radiomics signature, clinical data, and MRI features facilitates differentiation of BPGT from MPGT with improved diagnostic efficacy.

Conventional, diffusion, and dynamic contrast-enhanced MRI findings for differentiating metaplastic Warthin's tumor of the parotid gland

The purpose of this study was to explore conventional, diffusion, and dynamic contrast-enhanced MRI (DCE-MRI) characteristics for differentiating metaplastic Warthin's tumor (MWT) from other tumor types of the parotid gland, including non-metaplastic Warthin's tumor (non-MWT), pleomorphic adenoma (PA), and malignant tumor (MT). A total of 178 patients with histologically proven tumors of the parotid gland, including 21 MWTs, 49 non-MWTs, 66 PAs, and 42 MTs, were enrolled in the study. Conventional MRI was performed in all patients. One hundred and fifty patients had preoperative diffusion-weighted MR imaging (DWI), and 62 patients had preoperative DCE-MRI. The differences in the conventional, DCE-MRI, and DWI records between MWTs and the other three tumor types were statistically evaluated. Compared with non-MWTs and PAs, there was a statistically significant difference in circumscription (p < 0.01). The ill-defined circumscription was more common in MWTs than non-MWTs and PAs. Compared with PAs, there was a statistically significant difference in morphology (p < 0.05). The lobulated morphology was more common in PAs than MWTs. Compared with PAs and MTs, there was a statistically significant difference in the T2 signal of the solid component (p < 0.01). The T2 moderate intensity of solid components was more common in MWTs than PAs and MTs. The solid components of PAs mostly showed hyperintense on T2-weighted imaging. Cyst/necrosis was more common in MWTs than PAs and MTs. Hyperintense of cyst/necrosis was more common in MWTs and non-MWTs. With respect to contrast enhancement, 52.4% MWTs exhibited moderate or marked enhancement, and most non-MWTs (81.6%) exhibited mild enhancement. Most PAs (84.8%) exhibited marked enhancement. The mean ADC value of MWTs (0.94 × 10-3 ± 0.11 mm2/s) was significantly lower than that of the PAs (1.60 × 10-3 ± 0.17 mm2/s) (p < 0.001). On DCE-MRI, six of eight MWTs demonstrated TIC of type B. Although MWT is rare, conventional MRI characteristics, DWI and DCE-MRI can provide useful information for differentiating MWT from other parotid mass.

[Correlation between magnetic resonance imaging and extemporaneous and definitive histological examination of parotid gland tumors: a case series]

Parotid gland tumor is complex and poses diagnostic and therapeutic problems. The purpose of this study was to assess the role of extemporaneous examination in the management of patients with parotid gland tumors. We report a pro and retrospective analytical study of a series of cases of salivary gland tumors, whose data were collected in the ENT and in the department of cervical-facial Surgery at the University Hospital in Casablanca, between January 2012 and December 2015. Seventy two cases of parotid tumors were recorded. The sex-ratio (H/F) was 0.94, 0.76 for patients with benign tumors and 1.62 for patients with malignant tumors. The average age was 47 years (15- 75 years). The median of consultation time was 40 months. Clinical symptoms were dominated by parotid swelling (100%), pain in 25% of patients, facial palsy in 6%, and cervical adenopathies in 10%. Ultrasound was recommended in 80% of patients. MRI was performed in 26% of cases. All patients underwent surgery, 76% of patients underwent exofacial parotidectomies and 24% total conservative parotidectomies. This treatment was associated with ganglion resection in 24% of cases and radiotherapy in 24% of cases. Extemporaneous examination was performed in 71% of patients, its susceptibility was 89% and its specificity 88%. Definitive histological diagnosis was confirmed by anatomopathological examination in all cases. We confirmed benign and malignant tumors in 71% and 29% of cases respectively. Benign tumors were dominated by pleomorphic adenoma (59%), while malignant lesions were dominated by mucoepidermoid carcinoma (38%). The postoperative course was marked by: discrete haematoma in 4% of cases, transient facial palsy in 15%, superinfection of the wound in 3% and post-parotidectomy Frey´s syndrome in 3% of patients. One patient had labial recurrence of acinar cell carcinoma. No cases of death were noted. Parotid gland tumors are characterized by a great histological variability. Differentiation between malignant tumor and benign tumor is often difficult. Currently, MRI is the imaging test of choice. Extemporaneous examinationis is very useful intraoperatively when it is necessary to communicate with the pathologist. Multidisciplinary approach is adopted including ENT, oncological, radiotherapeutic, pathological and radiological approaches. Prognosis depends on the histological type, the stage of progression and treatment.

MRI-based texture analysis to differentiate the most common parotid tumours

AIM

To evaluate magnetic resonance imaging (MRI) features and signal characteristics of parotid masses and investigate the added role of texture analysis (TA) in the differentiation of parotid tumours.

MATERIALS AND METHODS

Ninety-five patients (42 women, 53 men; mean age 51.67±14.15) were included in this study. The study group consisted of 40 pleomorphic adenoma, 45 Warthin's tumour, and 10 mucoepidermoid carcinomas. Two reviewers assessed the MRI sequences retrospectively. Fat-suppressed T2-weighted and contrast-enhanced T1-weighted axial images were used for TA. Receiver operating characteristic curve analyses were performed to evaluate the ability to make a diagnosis. Logistic regression analyses were conducted to explore the independent risk factors among the MRI features and to analyse the added value of TA to the qualitative analysis.

RESULTS

Significant differences were found in the tumour border (p<0.001), infiltration of the surrounding tissue (p=0.003), contrast-enhancement grading (p<0.001), perineural spread (p=0.013), and pathological lymph nodes (p<0.001) between the malignant and benign tumours. Kurtosis on contrast-enhanced T1-weighted images, and skewness and kurtosis on T2-weighted images were significantly different between the three groups (p=0.020, <0.001, 0.003; respectively). A kurtosis value on T2-weighted images <2.815 along with an ill-defined border had the highest specificity (98.8%) and positive predictive value (83.3%) in the differentiation of malignant tumours.

CONCLUSION

The addition of TA parameters to the MRI findings may contribute to distinguish benign from malignant parotid tumours.

Delayed enhancement in differential diagnosis of salivary gland neoplasm

Background

Multi-phasic Computed Tomography (CT) evaluation allows to study the enhancement features of parotid gland masses. The aim of our study was to evaluate the role of delayed enhancement in the characterization of different histologic types of parotid tumours.

Methods

Forty-eight patients (22 male and 26 female) with at least one parotid gland tumor, were included in our study. Multi-phase CT images were obtained before and 30, 120 s and 8 minutes after intravenous contrast injection. The images were evaluated by two radiologists for lesion enhancement degree. A quantitative assessment was performed using a region of interest on each lesion and density changes between different phases were compared. The tumoral enhancement ratio was calculated between the 8 minutes delayed and the early (30 s) phase. The pathological diagnosis was confirmed in all patients after surgery.

Results

All patients had unilateral lesion for a total of 48 lesions. Twenty-eight were pleomorphic adenomas, 15 Warthin's tumours and 5 carcinomas. All Warthin tumours showed a rapid contrast enhancement at the early phase (30 sec) followed by a progressive wash-out during the delayed scans. Most of pleomorphic adenomas (89.2%) showed the highest density at the 8-minutes delayed phase. Malignant tumours showed slower contrast enhancement and 3 out of 5 (60%) showed a marked decrease at the 8 minutes delayed phase while the remaining 2 (40%), did not show any density reduction. The tumoral enhancement ratio was significantly different between Warthin tumours and pleomorphic adenomas and between Warthin's and malignant tumours.

Conclusions

Multi-phasic CT examination with 8 minutes delayed acquisition has shown to be useful in parotid gland lesion differentiation.

Preoperative biopsy in parotid malignancies: Variation in use and impact on surgical margins

OBJECTIVES

Determine rate of preoperative biopsy in parotid malignancies, identify factors associated with its use, and its association with surgical margins.

STUDY DESIGN

Retrospective cohort.

SETTING

Commission on Cancer-Accredited Institutions.

SUBJECTS AND METHODS

We included 5533 patients treated surgically for a parotid malignancy 2004-2014 in the National Cancer Database. Chi-squared tests, univariable, and multivariable logistic regressions were used to evaluate predictors of preoperative biopsy (defined as needle, aspiration, or incisional), and associate biopsy with surgical margins.

RESULTS

Preoperative biopsy was utilized in 26.0% of patients. Biopsy was more likely in patients >60 years (odds ratio [OR]: 1.19, P = .035), advanced clinical T stage (vs. T1,T2 OR: 1.23, P = .009; T3 OR: 1.26, P = .026; T4A OR: 2.05, P < .001), advanced clinical N stage (vs. N0, N1: OR: 1.39, P = .013; N2/3: OR: 1.63, P < .001), in academic centers (OR: 1.18, P < .024), and in higher volume centers (vs. low, medium OR: 1.28, P = .002; high OR: 2.16, P < .001). Biopsy use increased over time (vs. 2004-2006, 2007-2010 OR: 1.20, P = .047; 2011-2014 OR: 1.39, P < .001). Biopsy was associated with a reduced risk of positive margins in patients with clinical T1 stage (OR: 0.70, P = .012), and younger than 61 (OR: 0.79, P = .036).

CONCLUSION

The national rate of preoperative biopsy in parotid malignancy is low at 26.0%, but has increased over time. Preoperative biopsy is associated with a reduced risk of positive margins in younger patients and those with early clinical stage, suggesting its increased use may improve surgical outcomes and decrease reoperation or adjuvant therapy in these subgroups of patients.

LEVEL OF EVIDENCE

3 Laryngoscope, 130:1450-1458, 2020.

Diagnostic accuracy of magnetic resonance imaging techniques for parotid tumors, a systematic review and meta-analysis

OBJECTIVE

To assess the added benefit of combining different MRI techniques for preoperative diagnosis of parotid tumors when compared to conventional MRI and advanced MRI techniques alone with meta-analysis.

METHODS

A comprehensive PubMed electronic database search was performed for original diagnostic studies up to July 2017. The methodologic quality of each study was evaluated by two independent reviewers who used the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Statistical analysis included pooling of sensitivity and specificity with 95% confidence intervals (CI). All analyses were conducted using STATA (version 12.0), RevMan (version 5.2), and Meta-Disc 1.4 software programs.

RESULTS

Pooled sensitivity and specificity of conventional MRI, diffusion weighted imaging (DWI), dynamic contrast enhanced (DCE) and the above combination were 76% (95%CI)/91% (95%CI)/80% (95%CI)/86% (95%CI) and 83% (95%CI)/56% (95%CI)/90% (95%CI)/90% (95%CI).

CONCLUSION

Conventional MRI combined with DWI and DCE showed higher diagnostic accuracy than conventional or advanced MRI alone, supporting their use in parotid tumors diagnosis.

Functional MRI and CT biomarkers in oncology

Imaging biomarkers derived from MRI or CT describe functional properties of tumours and normal tissues. They are finding increasing numbers of applications in diagnosis, monitoring of response to treatment and assessment of progression or recurrence. Imaging biomarkers also provide scope for assessment of heterogeneity within and between lesions. A wide variety of functional parameters have been investigated for use as biomarkers in oncology. Some imaging techniques are used routinely in clinical applications while others are currently restricted to clinical trials or preclinical studies. Apparent diffusion coefficient, magnetization transfer ratio and native T1 relaxation time provide information about structure and organization of tissues. Vascular properties may be described using parameters derived from dynamic contrast-enhanced MRI, dynamic contrast-enhanced CT, transverse relaxation rate (R2*), vessel size index and relative blood volume, while magnetic resonance spectroscopy may be used to probe the metabolic profile of tumours. This review describes the mechanisms of contrast underpinning each technique and the technical requirements for robust and reproducible imaging. The current status of each biomarker is described in terms of its validation, qualification and clinical applications, followed by a discussion of the current limitations and future perspectives.

Accuracy of diagnosis of salivary gland tumors with the use of ultrasonography, computed tomography, and magnetic resonance imaging: a meta-analysis

OBJECTIVE

To compare ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) for clinical differential diagnosis in patients with salivary gland tumor (SGT).

STUDY DESIGN

Six databases were used to search the literature published between 1982 and 2013. Histologic diagnosis was required as standard diagnosis. Pooled estimate for sensitivity, specificity, summary receiver-operating characteristic curve (SROC) and area under curve (AUC) were calculated and compared using STATA and Meta-Disc statistical software.

RESULTS

Nineteen articles were included. Pooled sensitivity for US, CT, and MRI was 0.629 (95% confidence interval [CI] 0.52-0.73), 0.830 (95% CI 0.74-0.90), and 0.807 (95% CI 0.73-0.87), respectively; pooled specificity for US, CT, and MRI was 0.920 (95% CI 0.89-0.94), 0.851 (95% CI 0.79-0.90), and 0.886 (95% CI 0.85-0.92), respectively. The AUC under SROC for US, CT, and MRI was 0.934 ± 0.058, 0.912 ± 0.889, and 0.903 ± 0.045, respectively.

CONCLUSIONS

CT is recommended, as it is an effective imaging tool for differential diagnosis in patients with primary SGT, and MRI is suggested for differential diagnosis between benign and malignant GSTs because of its highest sensitivity and specificity.

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.

Correlation between equivalent cross-relaxation rate and cellular density in soft tissue tumors

OBJECTIVE

Equivalent cross-relaxation rate (ECR) imaging (ECRI), which allows quantitation of macromolecular tissue components, is a potentially useful nuclear magnetic resonance (NMR) technique for histopathological diagnosis. The purpose of this study was to compare ECR values among various histological types and assess the correlation between ECR and tumor cellular image in soft tissue tumors.

MATERIALS AND METHODS

We performed ECRI to evaluate cellular images of soft tissue tumors and tumorous lesions. Thirty-three patients who underwent evaluation with MRI and ECRI at the first visit were enrolled. Resection or biopsy was performed to obtain a histopathological diagnosis, followed by cell density measurement. ECR values of the histological subgroups were compared, and the correlation between ECR and cell density was analyzed to assess whether ECR can be used as an indicator of histological cell density.

RESULTS

ECR values for benign tumors varied widely and were not significantly different from those for malignant tumors. However, the mean ECR value was significantly higher for high-grade malignant tumors than for low-grade tumors (p < 0.01). Moreover, a positive correlation was found between ECR and cell density (r s = 0.72; p < 0.01).

CONCLUSIONS

ECR reflects the cell density and malignancy grade of a soft tissue tumor. ECRI could provide cellular imaging and useful clinical information to aid the pre-operative diagnosis of soft tissue tumors.

Real-time sonoelastography of major salivary gland tumors

OBJECTIVE

The purpose of this study was to determine the performance of real-time sonoelastography in the differential diagnosis of salivary gland tumors.

SUBJECTS AND METHODS

Between 2007 and 2010, 74 salivary gland tumors were examined by ultrasound and sonoelastography in 66 patients. Lesions were graded according to a 4-point elastography score. Surgical excision and histopathologic examination were performed in all cases. The difference in elastographic score between benign and malignant masses and that between pleomorphic adenomas and Warthin tumors were evaluated.

RESULTS

Of the 74 salivary tumors, 63 were located in the parotid, and 11 were in the submandibular gland. There were 18 malignant and 56 benign tumors. The mean (± SD) elastographic score was 2.58 ± 0.87 for pleomorphic adenomas, 2.15 ± 0.80 for Warthin tumors, 2.00 ± 0.57 for other benign tumors, and 2.94 ± 0.87 for malignant tumors. For benign tumors overall, the mean elastographic score was 2.41 ± 0.87. The difference in elastographic score between benign and malignant tumors overall was statistically significant (p < 0.05), but the difference between malignant tumors and pleomorphic adenomas and that between Warthin tumors and pleomorphic adenomas were not statistically significant. Using cutoff values between scores 2 and 3 and scores 3 and 4, there was no statistically significant difference between benign and malignant tumors.

CONCLUSION

Although this study revealed a difference in elastographic score between benign and malignant tumors, detailed analysis did not provide consistent results. Consequently, real-time sonoelastography appears to be a limited technique in the differential diagnosis between benign and malignant salivary masses.

MRI & MRS assessment of the role of the tumour microenvironment in response to therapy

MRI and MRS techniques are being applied to the characterisation of various aspects of the tumour microenvironment and to the assessment of tumour response to therapy. For example, kinetic parameters describing tumour blood vessel flow and permeability can be derived from dynamic contrast-enhanced MRI data and have been correlated with a positive tumour response to antivascular therapies. The ongoing development and validation of noninvasive, high-resolution anatomical/molecular MR techniques will equip us with the means to detect specific tumour biomarkers early on, and then to monitor the efficacy of cancer treatments efficiently and reliably, all within a clinically relevant time frame. Reliable tumour microenvironment imaging biomarkers will provide obvious advantages by enabling tumour-specific treatment tailoring and potentially improving patient outcome. However, for routine clinical application across many disease types, such imaging biomarkers must be quantitative, robust, reproducible, sufficiently sensitive and cost-effective. These characteristics are all difficult to achieve in practice, but image biomarker development and validation have been greatly facilitated by an increasing number of pertinent preclinical in vivo cancer models. Emphasis must now be placed on discovering whether the preclinical results translate into an improvement in patient care and, therefore, overall survival.

MR imaging of parotid tumors: typical lesion characteristics in MR imaging improve discrimination between benign and malignant disease

BACKGROUND AND PURPOSE

The surgical approach to parotid tumors is different for benign and malignant neoplasms, but the clinical symptoms do not correlate well with histology. Difficulties in tumor classification also arise in imaging modalities, in which sonography has the lowest and MR imaging, the highest accuracy. The purpose of this study was to review our experience using conventional MR imaging of the neck in the evaluation of parotid tumors and to evaluate which MR imaging findings are best able to predict malignant histology.

MATERIALS AND METHODS

Eighty-four consecutive patients (43 males, 41 females; median age, 56 years; range, 9-85 years) with parotid gland tumors who underwent MR imaging before surgery were prospectively included in the present study and retrospectively analyzed. Histology was available for all tumors. We analyzed the following MR imaging parameters: signal intensity, contrast enhancement, lesion margins (well-defined versus ill-defined), lesion location (deep/superficial lobe), growth pattern (focal, multifocal, or diffuse), and extension into neighboring structures, perineural spread, and lymphadenopathy.

RESULTS

The 57 (68%) benign and 27 (32%) malignant tumors consisted of 29 pleomorphic adenomas, 17 Warthin tumors, 11 various benign tumors, 5 mucoepidermoid carcinomas, 3 adenoid cystic carcinomas, 1 acinic cell carcinoma, 1 carcinoma ex pleomorphic adenoma, 9 metastases, and 8 various malignant neoplasms. Specific signs predictive of malignancy were the following: T2 hypointensity of the parotid tumor (P = .048), ill-defined margins (P = .001), diffuse growth (P = .012), infiltration of subcutaneous tissue (P = .0034), and lymphadenopathy (P = .012).

CONCLUSIONS

Low signal intensity on T2-weighted images and postcontrast ill-defined margins of a parotid tumor are highly suggestive of malignancy.

Potential of magnetization transfer MRI for target volume definition in patients with non-small-cell lung cancer

PURPOSE

To develop a magnetization transfer (MT) module in conjunction with a single-shot MRI readout technique and to investigate the MT phenomenon in non-small-cell lung cancer (NSCLC) as an adjunct for radiation therapy planning.

MATERIALS AND METHODS

A total of 10 patients with inoperable NSCLC were investigated using a 1.5T MR scanner. MT ratio (MTR) maps of several slices throughout the tumor were assessed. Each MTR-map was acquired within a short breathhold. Fluorodeoxyglucose positron emission tomography (FDG-PET) investigations were performed in addition to the MRI protocol. A total of 60 structures appearing conspicuous in FDG-PET were compared with structures appearing conspicuous in corresponding MTR maps. Quantification of similarity between both modalities was performed using similarity index calculation.

RESULTS

MTR-maps showed different contrast than FDG-PET images. However, structures that appeared conspicuous in FDG-PET images, either by a marked signal enhancement or signal decrease, were found to be similarly present in MTR maps. A mean similarity index of 0.65 was calculated. MTR values of suspected atelectasis were on average lower than MTR values of tumor tissue.

CONCLUSION

The proposed MT-MRI technique provides a high MT efficiency, while being robust and fast enough for breathhold acquisition. The results obtained encourage for further exploration of MT-MRI as an adjunct for radiotherapy planning in NSCLC.

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

BACKGROUND AND PURPOSE

Our aim was to determine the value of echo-planar diffusion-weighted MR imaging (epiDWI) in differentiating various types of primary parotid gland tumors.

MATERIALS AND METHODS

One hundred forty-nine consecutive patients with suspected tumors of the parotid gland were examined with an epiDWI sequence by using a 1.5T unit. Image analysis was performed by 2 radiologists independently, and the intraclass correlation coefficient was computed. Histologic diagnosis was obtained in every patient. For comparison of apparent diffusion coefficients (ADCs), a paired 2-tailed Student t test with a Bonferroni correction was used.

RESULTS

In 136 patients, a primary parotid gland tumor was confirmed by histology. Among the observers, a high correlation was calculated (0.98). ADC values of pleomorphic adenomas were significantly higher than those of all other entities, except for myoepithelial adenomas (P = .054). ADC values of Warthin tumors were different from those of myoepithelial adenomas, lipomas, and salivary duct carcinomas (P < .001, 0.013, and .037, respectively). Mucoepidermoid carcinomas, acinic cell carcinomas, and basal cell adenocarcinomas were not differentiable from Warthin tumors (P = .094, .396, and .604, respectively).

CONCLUSION

epiDWI has the potential to differentiate pleomorphic adenoma and myoepithelial adenomas from all other examined entities. Due to an overlap not only within the group of benign and malignant lesions but also between groups, diagnoses should not be addressed on the basis of ADC values solely. Therefore, further studies combining DWI, morphologic criteria, and probably other MR imaging techniques seem warranted.

Les tumeurs des glandes salivaires

Tumors of salivary glands arise mainly from the parotid gland. Magnetic Resonance Imaging (MRI) is mandatory not only to localize precisely the tumor within the gland but also to differentiate between benign and malignant neoplasms, in competition with cytology in fine-needle aspiration biopsy. Tumors without risk of transformation, such as adenolymphoma, are not systematically operated on. Indications of roentgenotherapy and irradiation volumes depend on histologic type, localisation and size of the tumor.

MR imaging of salivary glands

Diagnostic imaging of salivary glands has been revolutionized with the advent of cross-sectional imaging modalities like CT and MR imaging. In the era before CT, imaging of the salivary glands was relatively unrewarding and was used uncommonly by ear-nose-throat surgeons. Early diagnostic tests like plain films and sialography evaluated dilated parotid ducts and calculus disease within ducts or glands. Full evaluation of salivary glands, especially deep lobes of parotid gland and masses of minor salivary glands, was not possible by these methods, however. Imaging of the parotid glands has developed significantly since that time. CT and MR imaging greatly compliment physical and endoscopic examinations (and previous favorites like sialography) by direct visualization of previously blind areas of the salivary glands and extension of the disease process in surrounding tissue planes.

Diagnostic accuracy of fine-needle aspiration cytology and frozen section in primary parotid carcinoma

BACKGROUND

The low incidence and histologic heterogeneity of primary parotid carcinomas makes it difficult to evaluate the value of preoperative fine-needle aspiration cytology (FNAC) and intraoperative frozen section (FS) analysis. In the current study, the authors reviewed a single institution's experience regarding the preoperative and intraoperative diagnostic value of FNAC and FS in primary salivary gland carcinomas.

METHODS

Between January 1990 and December 2002, 108 primary parotid carcinomas were resected at the Department of Otorhinolaryngology, Head and Neck Surgery at the University of Berne, Inselspital (Berne, Switzerland). Included in the study were a total of 101 carcinomas with preoperative FNAC results in 88 tumors and/or intraoperative FS results in 45 tumors. In a retrospective study, the results of FNAC and FS were analyzed and compared with the corresponding histopathologic diagnoses.

RESULTS

The cytologic findings were true-positive for malignancy in 63 tumors (72%), false-negative in 22 tumors (25%), and nondiagnostic in 3 tumors (3%). The tumor grading was correct in 29 of 63 tumors (46%), and the exact tumor typing was correct in 27 of 63 (43%) true-positive tumors. The FS findings were true-positive for malignancy in 43 of 45 tumors (96%), the tumor grading was correct in 35 of 45 tumors (78%), and the tumor typing was correct in 32 of 45 tumors (71%). Overall, at the time of surgery, of the 101 parotid carcinomas, the tumor was known to be malignant in 83 tumors (82%), and the correct grade and the exact tumor type were known in 55 tumors (54%) and 48 tumors (48%), respectively.

CONCLUSIONS

FNAC recognized malignancy in 72% of tumors, but it could not be relied upon to provide an accurate tumor grading or typing. Therefore, FNAC alone is not prone to determine the surgical management of primary parotid carcinomas. The current analysis showed the statistically significant superiority of FS compared with FNAC regarding the diagnosis of malignancy, tumor grading, and tumor typing in primary parotid carcinomas.

Magnetization transfer, HASTE, and FLAIR imaging

Continuous technologic developments and research have increased the clinical applications of MT, HASTE, and FLAIR imaging in neuroradiology. HASTE has become the MR imaging sequence of choice for fetal neuroimaging. Other promising uses, such as for diffusion-weighted imaging, have not been fully exploited. FLAIR has been firmly established as one of the cornerstones of brain imaging; however, post-contrast FLAIR images have not offered a clear advantage over standard T1-weighted images as suggested by early studies. FLAIR imaging with echoplanar acquisition is not considered advantageous, because the decreased imaging times are obtained at the expense of lower sensitivity. For a number of applications, diffusion-weighted imaging has surpassed FLAIR. Nevertheless, FLAIR images may be more sensitive for the detection of acute brain infarction. Recently described methods for the elimination of CSF flow artifacts may lead to improved quality and reliability of FLAIR images for subarachnoid space disease. MT preparation is now routinely incorporated in time-of-flight MR angiography and gradient-echo T2*-weighted spine imaging sequences and provides increased sensitivity for postcontrast MR imaging. These applications may not be advantageous in all clinical settings. MTR analysis offers valuable information for an increasing number of pathologic processes but has not yet gained wide clinical acceptance owing to sophisticated postprocessing and significant intercenter variations. Different modifications of these techniques are being evaluated, and further developments are expected.

Preoperative diagnostic values of fine-needle cytology and MRI in parotid gland tumors

The aim of this retrospective study was to assess and compare the diagnostic value of fine-needle cytology and MRI for the prediction of malignancy in parotid tumors. During an 11-year period, 148 patients underwent preoperative fine-needle aspiration cytology in our institution. Eighty-seven patients underwent a preoperative MRI study, and 54 had both MRI and cytology. The study compares results of cytology and MRI with histological reports. The sensitivity, specificity and accuracy for detecting malignant lesions were 87, 94 and 93% respectively for MRI, 81, 95 and 92% respectively for cytology and 100, 88 and 91% respectively for both studies combined. Fine-needle cytology provided better information than MRI concerning precise histological diagnoses. Conversely, the proportion of non-diagnostic smears reached 10%. Fine-needle cytology and MRI are simple, well-tolerated diagnostic means with an impact on the management of salivary gland tumors. The associated anatomic information obtained by MRI imaging makes it the test of first choice in an optimal medical environment.

Effect of muscular contraction on magnetization transfer detected at 1.5 T

The effect of rigor (formation of actomyosin complexes) on magnetization transfer was observed with a 1.5 T clinical magnetic resonance (MR) imaging system. The magnetization transfer ratio of chemically skinned (calcium-sensitive) muscle fiber preparations increased much more in a rigor state than in a relaxed state, while that of calcium-insensitive fiber preparations and solutions showed no difference. These results suggest that the formation of actomyosin complexes increased the magnetization transfer ratio. A clinical MR system is not only effective for medical imaging, but also has the potential to demonstrate physiological characteristics.

MR imaging of salivary glands

In conclusion, if a parotid gland mass is bilateral, it is more likely to be Warthin's tumor, especially if it does not enhance. Less likely, it could be lymphoepithelial cyst or necrotic lymph node. A unilateral, non-enhancing mass with a high T2 signal is more likely to be a Warthin's tumor and less likely a necrotic lymph node or first branchial cleft cyst. If the mass is unilateral, shows postcontrast enhancement, has a high T2 signal, and does not invade surrounding tissue planes, it is more likely to be a pleomorphic adenoma. An intermediate to low T2 signal mass-with or without invasion of surrounding tissue planes--is more likely to be a malignant mass such as adenocystic or mucoepidermoid carcinoma. Biopsy is superior and the gold standard for diagnosis and cannot be replaced by MR imaging, however.