Evaluation of solid lesions affecting masticator space with diffusion-weighted MR imaging

Computed tomography evaluation of alterations in the masticator space due to invasion by malignant head and neck neoplasms

Objective

To evaluate alterations in the masticator space due to the dissemination of malignant neoplasms originating from the tonsillar fossa, retromolar trigone, maxillary sinus, or nasopharynx, using computed tomography (CT), as well as to correlate the presence of trismus with the CT findings and the dimensions of the tumor.

Materials and Methods

We evaluated the medical records of 65 patients with malignant tumors in the regions described. The images were analyzed by two physician examiners, working independently, who were blinded to the clinical data. In the evaluation of the masticator space, the following parameters were considered: symmetry with the contralateral space; obliteration of the fat plane, retromolar trigone, or pharyngeal space; edema/atrophy of the medial or lateral pterygoid muscles; and destruction of the mandibular ramus.

Results

Obliteration of the fat plane was found in 69.2% of the patients. Asymmetry, edema/atrophy, and bone destruction were detected in 27.7%, 26.2%, and 20.0% of the patients, respectively. Trismus was identified in 15.4% of the patients. Of the patients with trismus, 90.0% had stage T4 tumors, compared with only 43.8% of those without trismus. Trismus was 11.6 times more common among the patients with stage T4 tumors than among those with lower-stage tumors. Neoplasms of the tonsillar fossa and retromolar trigone collectively accounted for 95.0% of the cases. The CT scans showed edema/atrophy of the pterygoid muscles in 60.0% of the patients with trismus and in 21.8% of those without. An association was observed between T4 tumor stage and edema/atrophy of the pterygoid muscles. In addition, the risk of trismus was 5.4 times higher among the patients with stage T4 tumors.

Conclusion

In our patient sample, the most common finding was obliteration of the fat plane, followed by asymmetry and edema/atrophy. Most of the patients with T4 tumors had trismus, together with edema/atrophy of the pterygoid muscles.

Diffusion-weighted magnetic resonance imaging of the oral and maxillofacial region: optimal fat suppression method

OBJECTIVE

To compare 3 fat suppression methods-water excitation (WE), chemical shift selective (CHESS), and short T1 inversion recovery (STIR)-for optimal image quality and apparent diffusion coefficient (ADC) values with magnetic resonance imaging (MRI) using diffusion-weighted imaging (DWI) of the oral and maxillofacial region.

STUDY DESIGN

In total, 53 patients with 73 lesions were enrolled in this study. MRI using DWI protocols with the 3 fat suppression methods were performed in addition to a conventional MRI protocol. The diagnostic image quality of lesions, image uniformity, degree of image artifacts, and ADC values of the lesions were evaluated. Average visual scores and ADC values were compared, and post hoc pairwise comparisons were performed, with the level of significance set at P < .0167.

RESULTS

Diagnostic image quality was not significantly different among the fat suppression methods (P ≥ .042). Image uniformity was significantly higher (P < .001), and the degree of image artifacts was significantly lower (P < .001), in images using the STIR method. Mean ADC values did not differ significantly among the 3 methods.

CONCLUSIONS

The STIR method was the most useful fat suppression method for DWI of the oral and maxillofacial region because of its high level of image uniformity and few image artifacts.

Application of diffusion-weighted magnetic resonance imaging in the diagnosis of odontogenic lesions: a systematic review

OBJECTIVES

This systematic literature review addresses the use of diffusion-weighted magnetic resonance imaging (DWI) and apparent diffusion coefficient (ADC) for the evaluation of benign maxillomandibular odontogenic lesions.

STUDY DESIGN

Databases were searched, and original research studies or case report manuscripts up to April 2019 were included, using the keyword "diffusion," combined with the keywords "maxillofacial pathology," "oral pathology," "odontogenic tumors," "dental tissue neoplasms," "odontogenic cysts," and the histologic denomination of benign odontogenic lesions, according to the World Health Organization classification. Only English language articles and studies pertaining to DWI were selected.

RESULTS

Fifteen investigations (11 original articles and 4 case reports) of distinct benign odontogenic lesions were included. Most studies did not include exclusively odontogenic lesions in their samples.

CONCLUSIONS

It is too early to reach a conclusion that DWI and ADC can provide useful information in the differentiation of the histologic type of some benign odontogenic lesions on the basis of available data in the literature.

A Rare Case of Idiopathic Temporal Muscle Abscess in a Nine-month-old Infant

Temporal muscle abscess in children usually occurs from acute otitis media, and rapid progression and concomitant infectious disease often make it easy to diagnose. We report a rare case of a nine-month-old infant who showed right temporal mass with no evidence of infection. Computed tomography showed an osteolytic round mass, and magnetic resonance imaging revealed heterogenous enhancement with a high apparent diffusion coefficient. Malignant tumor was first suspected, but an open biopsy revealed the swelling to be temporal muscle abscess. It should be noted that temporal abscess may mimic the features of a malignant tumor, and multiple examinations should be performed for an accurate diagnosis.

Tuberculosis of the parotid lymph nodes: clinical and imaging features

Objectives

To characterize clinical, computed tomography (CT) and magnetic resonance imaging (MRI) features of tuberculosis (TB) of the parotid nodes.

Materials and methods

CT (n=21) and MR (n=7) images, and clinical data from 25 patients with TB of the parotid nodes were retrospectively analyzed by two experienced radiologists who reached consensus.

Results

Younger patients (aged <50 years) accounted for 72%. Eighty percent of patients were asymptomatic, and had no history of TB exposure. According to clinical and imaging findings, 64% and 60% patients were misdiagnosed as having tumors, respectively. A total of 43 lesions were identified. Thirty-eight (88.4%) lesions involved the superficial lobe. Fourteen (56%) cases had multiple lesions. There were four types of changes in the parotid fascia: local thickening (40%, n=10); local rupture with thickened adjacent skin (28%, n=7); focal bulge (20%, n=5); and no changes (12%, n=3). Cervical lymphadenopathy was seen in 14 out of 25 cases (56%). The lesions were contrast-enhanced in four patterns on CT images: homogeneous enhancement (37.1%, n=13), irregular cyst-like enhancement (37.1%, n=13), thick-walled ring enhancement (14.2%, n=5), and garland-like enhancement (11.4%, n=4). On MRI, the signal intensity of lesions was isointense on T1-weighted image, hyperintense on T2-weighted image, markedly hyperintense on diffusion-weighted imaging, and low on the apparent diffusion coefficient map. The surrounding parotid parenchymal edema was identified clearly on coronal MR images.

Conclusion

TB of the parotid nodes tend to simulate tumors clinically and radiologically. Their preferential sites are the superficial lobe. In young patients with positive purified protein derivative skin test and lesions accompanied by cervical lymphadenopathy, changes in the parotid fascia and parotid parenchymal edema adjacent to the lesions on CT and MRI may be helpful in the diagnosis and to facilitate differential diagnosis.

Diffusion kurtosis imaging in the differential diagnosis of parotid gland disease and parotid adenolymphoma: preliminary results

OBJECTIVES

To study the value of diffusion kurtosis imaging (DKI) in diagnosis of parotid gland disease (PGD) with different pathological patterns and parotid adenolymphoma (PAL).

METHODS

57 patients with different kinds of PGD were enrolled and underwent DKI and conventional diffusion-weighted imaging (DWI). All patients were categorized into different groups according to their pathological patterns. The result of calculating the value of DKI-derived parameters (K_mean, K_rad, K_ax, D_mean, D_rad, D_ax, and FA) and apparent diffusion coefficient (ADC) of DWI were used to study their diagnostic accuracy in PGD with different pathological patterns. The binary logistic regression method was used to confirm clinical valuable diffusion parameters (obtained with DKI and DWI models) for diagnosing PAL. Using MedCalc 13.0, receiver operating characteristic (ROC) analysis was conducted to evaluate the diagnostic value of confirmed parameters based on the logistic regression equation.

RESULTS

Both DKI parameters and conventional ADC showed statistical significance in diagnosing PGD with different pathological patterns (p < .01). By using the DKI model, kurtosis coefficients showed higher diagnostic capability than diffusion coefficients ([K_mean+K_rad + K_ax] vs [D_mean +D_rad + D_ax]: 22 vs 15, p < .01) did in the differential diagnosis among different PGD groups. In the diagnosis of PAL among all PGD patterns, the ROC analysis demonstrated that the area under curve (AUC) FA +K_ax [0.881 ± 0.057 (0.824 to 0.938)] is higher than that when using FA [0.629 ± 0.095 (0.534 to 0.724)] and K_ax [0.800 ± 0.070 (0.730 to 0.870)] alone (p < .05), with sensitivity, specificity, accuracy, and both positive and negative predictive values of 71.43, 95.78, 91.77, 76.92, and 94.44%, respectively.

CONCLUSIONS

DKI showed higher diagnostic capacity in the differential diagnosis of PGD with different pathological patterns. Combined parameters of DKI can differentiate PAL from other PGD pathological patterns with a high degree of accuracy. This technique shows great potential for DKI in the differential diagnosis of PGD within a certain pathological category.

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.

Differentiation of benign and malignant lesions of the tongue by using diffusion-weighted MRI at 3.0 T

OBJECTIVES

Diffusion-weighted MRI (DWI) has been introduced in head and neck lesions and adds important information to the findings obtained through conventional MRI. The purpose of this study was to assess the role of DWI in differentiating benign and malignant lesions of the tongue at 3.0-T field strength imaging.

METHODS

78 patients with 78 lingual lesions underwent conventional MRI and DWI with b-values of 0 and 1000 s mm(-2) before therapy. The apparent diffusion coefficient (ADC) maps were reconstructed, and the ADC values of the lingual lesions were calculated and compared between benign and malignant lesions of the tongue.

RESULTS

The mean ADC values of the malignant tumours, benign solid lesions and cystic lesions were (1.08±0.16)×10(-3), (1.68±0.33)×10(-3) and (2.21±0.35)×10(-3) mm2 s(-1), respectively. The mean ADC values of malignant tumours were significantly lower (p<0.001) than those of benign solid lesions, and the mean ADC values of benign solid lesions were significantly lower (p<0.001) than those of cystic lesions. Receiver operating characteristic analysis showed that when an ADC value<.31×10(-3) mm2 s(-1) was used for predicting malignancy, the highest accuracy of 95.3%, sensitivity of 92.6% and specificity of 97.3% were obtained.

CONCLUSIONS

ADC values of benign and malignant lesions are significantly different at 3.0-T imaging. DWI can be applied as a complementary tool in the differentiation of benign and malignant lesions of the tongue.

Anatomy and pathology of the masticator space

Objective

This article reviews and illustrates the anatomy and pathology of the masticator space (MS).

Background

Pathology of the masticator space includes inflammatory conditions, vascular lesions, and tumours. Intrinsic tumours of this space can be benign and malignant, and they may arise from the mandibular ramus, the third division of the trigeminal nerve, or the mastication muscles. Malignant tumours may appear well defined and confined by the masticator fascia, without imaging signs of aggressive extension into neighbouring soft tissues. Secondary invasion of the masticator space can also occur with tumours of the nasopharynx, oropharynx, oral cavity, and parotid glands. Perineural tumour spread (PNS), especially along the trigeminal nerve, can also occur with masticator space malignancies.

Conclusion

Masses of the MS are difficult to evaluate clinically, and computed tomographic (CT) and magnetic resonance (MR) images are essential for the diagnosis and characterisation of these lesions. Malignant tumours may appear well defined and confined by the fascia. Thus, when a mass is identified, a biopsy should be done promptly. PNS may occur in tumours involving the MS and its recognition on imaging studies is essential to plan the appropriate treatment.

Teaching points

• Differentiating between intrinsic and extrinsic lesions is essential to the differential diagnosis

• Infections of the MS may cross the fascia and mimic neoplasms on imaging studies

• Malignant tumours may show no aggressive signs, such as bone erosion or violation of the fascia

• Perineural spread (PNS) is often clinically silent and frequently missed at imaging and leads to tumour recurrence

Role of diffusion-weighted MRI in differentiation of masticator space malignancy from infection

OBJECTIVE

The aim of this study was to assess the role of the apparent diffusion coefficient (ADC) value in differentiation of masticator space malignancy from infection.

METHODS

A retrospective study of 49 patients (31 male and 18 female; age range 5-66 years) with masticator space lesion was conducted. They underwent spin-echo-type echo planar diffusion-weighted MRI of the head and neck with b-values of 0 mm(2) s(-1), 500 mm(2) s(-1) and 1000 mm(2) s(-1). The ADC maps were reconstructed and the ADC value of the masticator space lesion was calculated.

RESULTS

The mean (± standard deviation) ADC value of masticator space malignancy (0.91 ± 0.21 × 10(-3) mm(2) s(-1)) was significantly lower (p = 0.001) than that of masticator space infection (1.59 ± 0.32 × 10(-3) mm(2) s(-1)). When an ADC value of 1.20 × 10(-3) mm(2) s(-1) was used as a threshold value for differentiating masticator space malignancy from infection, the best result was obtained with an accuracy of 88%, sensitivity of 88%, specificity of 87%, negative predictive value of 94%, positive predictive value of 86% and area under the curve of 0.92. There was a significant difference in the ADC value between squamous cell carcinoma and soft tissue sarcoma (p = 0.001), as well as between bacterial and fungal infection of the masticator space (p = 0.001).

CONCLUSION

We concluded that ADC value is a non-invasive promising imaging parameter that can be used for differentiation of masticator space malignancy from infection.