Imaging of oral cavity and oropharyngeal masses: clinico-radiologic correlation

Background Clinical diagnosis of the masses of the oropharynx and the oral cavity is usually straightforward; however, deep extension of lesions should be assessed by imaging. Thirty patients with suspected masses in oral cavity and oropharynx were enrolled in the present study. Contrast-enhanced CT and MRI were used for imaging of all patients, and superficial ultrasound was used as screening (whether the mass was accessible to ultrasound or not). The aim of this study was to evaluate clinical impact of combined imaging modalities for assessment of intraoral and oropharyngeal masses. Results There was a statistically significant difference between CT and MRI regarding the detected tumor size, lymph node and adjacent structures. CT had a sensitivity of 77.78% and specificity of 75% in the detection of malignancy. A low apparent diffusion coefficient can detect malignancy with 61.11% sensitivity and 91.67% specificity. Conclusions The radiographic diagnosis of the oral cavity presents a complex challenge. According to the unique presentation of each patient, combined CT and MRI imaging will enhance the identification and characterization of lesions in the oral cavity and oropharynx. There is a secondary, limited role for ultrasonography

The oropharynx is located posterior to the oral cavity, and extends from the soft palate to the level of the hyoid bone (C3).It is continuous with the nasopharynx superiorly, the hypopharynx inferiorly, and the oral cavity anteriorly (via the isthmus faucium) [2] .
Head and neck malignancies are the sixth most common tumors in the world, one-third of them are oral cavity tumors.Most of them are squamous cell carcinoma (SCC).Clinical diagnosis of the oral cavity and oropharyngeal tumors is usually straightforward; however, deep extension of tumors should be assessed by crosssectional imaging [3,4].
Since CT is easily accessible and provides faster image capture, it is typically used as a first-line examination to help differentiate between various clinical processes [5,6].
MRI is the most accurate method for assessing the amount of the initial intraoral tumor, its depth of invasion, its deep muscle invasion, and its resectability [7,8].
Ultrasonography (US) is widely available and simple to use, and it is of secondary importance.It can be helpful in guiding imaging of the submandibular region and accompanying lymph adenopathy [9].
Several reports on preoperative radiological depth of invasion evaluations using CT, MRI, and ultrasonography have been published to far; however, no study involving all of these procedures has been published [10,11].
The purpose of this study was to evaluate the clinical impact of combined imaging modalities including superficial ultrasound, CT, MRI for assessment of intraoral and oropharyngeal masses.

Methods
This prospective study was carried out on thirty patients with clinically suspected intraoral and oropharyngeal masses.All cases were referred from Otolaryngology department to Diagnostic Radiology and Medical Imaging department between October 2021 and January 2024.
The inclusion criteria included patients with suspected primary intraoral and oropharyngeal masses.No age or gender restrictions.
The exclusion criteria included general contraindication to MRI, contrast media hypersensitivity, and renal function impairment.
Ethical approval by university ethics committee.Ethics committee reference numbers is 34921/9/21.
Detailed history was taken regarding the current condition, its severity, and any other associated symptoms were recorded.Demographic information was obtained including age and gender.

Ultrasound imaging
Ultrasound imaging was conducted using a linear probe that was compatible and had a frequency of 10-12 MHz (Voluson E8; GE Healthcare Technologies, Milwaukee, WI, USA).Grayscale imaging was the first step in the US evaluation process for every patient.The patient was placed on their back, with their neck resting slightly on a cushion.Operators evaluated the mass's size, location, echogenicity, and relationship to neighboring structures at grayscale US.Doppler ultrasonography: to evaluate the mass's vascularity.

CT scan
For all of the patients in the study, contrast-enhanced CT was carried out utilizing multi-slice 64 detectors (CT Toshiba Health Care, Japan).
Examination protocol The imaging range extended to the superior mediastinum from the inferior orbital edge.The nonionic iodine contrast medium, which has an iodine content of 300-350 mg/mL, was delivered at a speed of 0.8-1.5 mL/s from the superficial veins of the forearm or cubital fossa.Imaging was initiated 70-90 s after the contrast medium was injected.The axial plane is used for image acquisition.
The following were the CT acquisition parameters The tube voltage was 120-160 kVp (Reference mAs, 60-120) which was the standard tube current.There was 1.0 mm of slice thickness.The reconstruction interval was 3.0 mm employing a sophisticated reconstruction formula.
Post-processing The obtained images were sent to an independent workstation for processing, manipulation, and reconstruction in the bone and soft window axial, coronal, and sagittal planes.Axial sections with a thickness of 2-3 mm can be obtained, although multiplanar reformations need to be created from retro-reconstructed images of 0.625 or 0.75 mm (Fig. 1).

MRI imaging
MRI with Gadolinium contrast was performed using a 1.5-T system (Magnetom Essenza 1.5-T SIEMENS Healthineers) for all patients.
MRI acquisition parameters The MRI sequences were as follows: • Pre-contrast T1-weighted turbo spin-echo imaging: FOV was 260 mm, TR/TE was 735 ms/16.5 ms, slice thickness was 4 mm; for axial section, TR/TE was 602 ms/13 ms for the sagittal section.Image interpretation and analysis Two radiologists with 17 and 22 years of expertise, respectively, examined the scans and analyzed the images.Radiological DOI for CT and MRI was calculated using a specialized terminal using DICOM data that was imported into and kept in PACS: The post-contrast axial picture and the post-contrast coronal MPR image were used in CT to achieve the measurement.Measurements of FSCET1-WI and FST2-WI were made in axial and coronal MRI images.The ADC cut-off value of 1.23 × 10 −3 mm 2 s −1 was used as described by Yuan et al. [12].
Every image was assessed visually, and a consensus was established to determine the final opinion.The gold standard was histopathological analysis.

Statistical analysis
Statistical analysis was conducted by IBM SPSS software package version 25.0 (Armonk, NY: I BM Corp).Qualitative data were presented using number and percentage.Quantitative data are presented as mean and standard deviation (SD).For categorical variables, Chi-square test was used for analysis.The level of significance was adopted at P < 0.05.

Results
Thirty patients were enrolled in this study with mean age of 43.8 years old, ranged from 21 to 84 years.Males were 16 (53.3%)and females were 14 (46.7%).Symptoms of included patients were as swelling (Fig. 2), painful swallowing and dysphagia (Table 1).
The most common sites of primary lesions were in the tongue (Fig. 3) and palates (Fig. 4) (Table 2).
The mass was malignant in 53.3% of patients and benign in 46.7% patients.The majority of malignancy were squamous cell carcinoma (26.7%) and carcinoma ex pleomorphic adenoma (10.0%).The most common benign tumor was pleomorphic adenoma (Table 3).
Ultrasonography was useful in nine cases.It helped to detect absent thyroid and expect ectopic thyroid elsewhere, characterize lymph node enlargements.But, US could not differentiate carcinoma ex pleomorphic adenoma versus pleomorphic adenoma based on sonographic pattern (Table 4).In 21 cases, US was of limited value.
At CT, the size of tumor was 2.56 ± 1.28 cm.Tumor size was classified according to TNM classification (Table 5).
Involvement adjacent structures was more prominent in MRI images (Figs. 5 and 6).MRI had superiority in the diagnosis of carcinoma ex pleomorphic adenoma and pleomorphic adenoma than CT.In MRI, the size of tumor was 2.7 ± 1.3 cm.Involvement of adjacent structures, enlargement of lymph node, and necrosis or cystic change were assessed (Table 6).
There was a statistically significant difference between CT and MRI regarding the detected tumor size.Involvement of adjacent structures was observed in seven patients using CT and in 12 patients using MRI.Calcification was observed in two cases by CT and not observed using MRI.Enlargement of lymph node > 5 mm was observed in 17 patients using CT and in 20 patients using MRI (Table 7).
CT had sensitivity of 77.78% and specificity of 75% in detection of malignancy.Low apparent diffusion coefficient can detect malignancy with 61.11% sensitivity and 91.67% specificity.

Discussion
The oral cavity is a complicated anatomical area that can be subjected to a wide range of pathological illnesses, including tumors, inflammations, and developmental disorders [13].
Endoscopy and clinical examination are the main methods used to evaluate masses in the oropharynx and oral cavity.Biopsies are used to diagnose cancer.Crosssectional imaging is used for staging and makes the pathology under the mucosa visible.It also aids in estimating the tumor's size, thickness, and depth, detects invasion of nearby structures, bone, or perineural spread, evaluates lymph node metastases, rules out the presence of a second tumor, and is used for treatment planning and follow-up both during and after treatment [14].We recruited 30 patients with oral cavity and oropharyngeal masses, and the mean age was different from the results in the study done by Labib et al. [15] who found that the mean age of oral cancer occurrence was 56.85 ± 14.21 years with male predominance (male to female ratio was 1.4:1).In the study of Shahrour [16], the mean age of patients with oral cancer was 51.1 years (for males was 52.1 years and for females was 50 years).It was lower in the present study.
Tshering et al. [14] reported that because computerized tomography (CT) is widely accessible, reasonably priced, rapid, and simple to use, it is typically the initial imaging modality utilized to evaluate and stage tumors of the oral cavity and oropharynx.Define the size and extent of the main tumor, evaluate bone involvement, and identify any metastatic lymph nodes with a CT scan.Alsowey et al. [17] recorded an excellent overall agreement for the total score of metastatic lymph node detection by CT in HNSCC.Radiation exposure, the requirement to inject iodinated contrast agents, inadequate contrast for soft tissues, and amalgam-related artifacts are among the drawbacks.
Furthermore, in our study, computed tomography revealed that the majority of benign tumors were welldefined and the majority of malignant tumors were moderate and poorly defined.Enlargement of lymph node, which diagnosed using CT and MRI, was most observed in malignant cases.The majority of malignant tumors had hypointense T1-weighted and low ADC that was in the same way with Razek et al. [18] who observed that after therapy, recurrent malignant tumors show normal to enhanced ADC, whereas high cellularity in the former indicates decreased ADC.
In this study, CT had sensitivity 77.78% and specificity 75% in detection of malignancy.Mukherji et al. [19] conducted a study on 49 patients who underwent mandibulectomy for treatment of oral squamous cell carcinoma that was clinically fixed to the mandible.CT appropriately identified 25 out of 26 patients with mandibular invasion.In 20 out of 23 patients without invasion, CT properly ruled out mandibular invasion.The CT scan demonstrated a diagnostic accuracy of 96% for detecting mandibular invasion, 87% for specificity, 89% for positive predictive value, and 95% for negative predictive value, which is in line with our findings.
Truckmeier et al. [20] also revealed that CT proves sufficient to predict LN metastases (LNMs) in patients with oral SCC.Also, Uribe et al. [21] found that CT have a high diagnostic accuracy for detection of mandibular bone tissue invasion (83%) which in the same way with our results.
In our study, low apparent diffusion coefficient can detect malignancy with 61.11% sensitivity and 91.67% specificity and that near to the study of Ogura et al. [22] when examining ADC values of normal structures and lesions in the oral and maxillofacial region, a threshold ADC value of 1.791 × 10 −3 mm 2 /s was shown to have an 83.3% specificity and 80% sensitivity in differentiating between malignant and benign lesions.A threshold ADC value of less than 1.31 × 10 −3 mm 2 /s was determined by Li et al. [23]; after studying, 78 patients with lingual lesions were investigated (sensitivity, 92.6%; specificity, 97.3%).The study has certain drawbacks.First of all, the study was limited to a small number of cases at a single institution, and there was a variable interval between the assessment and the surgery.It also does not take into account hybrid imaging as additional imaging modality.Thirdly, the limited availability of long-term clinical outcomes.

Conclusions
The radiographic diagnosis of the oral cavity presents a complex challenge.Oral cavity and oropharyngeal lesions will be better detected and characterized with the use of combined CT and MRI imaging according to patient specific presentation.Ultrasonography has a secondary limited role.

Fig. 1 A
Fig. 1 A 35-year-old male presented with difficulty of swallowing.CECT axial (A, B and C), coronal (D and E) and sagittal (F) show A small well-defined fluid density lesion is seen expanding the left epiglottic vallecula at the level of the hyoid bone.It abuts the aryepiglottic fold and the base of epiglottis.It abuts the base of the epiglottis with no sign of infiltration or invasion, no significant enhancement.No significant paraglottic fat or soft tissue invasion seen.Intra-operative laryngoscopy (G and H) revealed well-defined rounded lesion with smooth outline at the base of the tongue.Diagnosis: vallecular cyst

Fig. 2 A
Fig.2A 62-year-old female with no known medical illness, presented with swelling at the floor of the mouth in the left sublingual region for 3 months, gradually increase in size, associated with abnormal, foul tastes, loss of appetite and loss of weight.US (A and B) show hypoechogenic solid masses with irregular margin, non-uniform echo and abundant blood flow signals.MRI (C-J): A mass is seen at left sublingual region.The lesion extends and involve the root of tongue, not cross the midline.The lesion is isointense to muscle on T1, heterogeneously hyperintense on T2, hyperintense in STIR with restricted diffusion and shows heterogeneous marked enhancement post-contrast.Central part of lesion less enhanced with involvement of mylohyoid muscles.A few enlarged nodes are also seen at Level II and Level III.K clinical inspection L surgical specimen.Diagnosis: Adenoid cystic carcinoma of the left sublingual salivary gland (See figure on next page.)

Fig. 3 AFig. 3 continuedFig. 4 AFig. 4
Fig. 3 A 60-year-old female presented with difficulty in swallowing and chewing.CT (A and B) revealed enhanced soft tissue mass at left side of tongue measures about (3 × 1.5 × 2.5 cm) mainly involving left genioglossus muscle, not crossing the midline.In MRI (C-H), the lesion displays low T1 signal intensity, high T2 signal intensity, hyperintense in STIR and shows marked enhancement post-contrast.I Clinical inspection revealed mass at the left lateral of the tongue.Histopathology proved Squamous cell carcinoma of the tongue.Patient treated with radiotherapy

Fig. 5 A
Fig. 5 A 65-year-old female presented with dysphagia.MRI (A-J) revealed large well-circumscribed lobulated soft tissue mass in the prevertebral space (C2-C5) invading C2 with intact clivus.It extends to the oropharynx that compressed and deformed.There is no vascular encasement, no extension into spinal canal.The mass is T1 hypointense, T2 hyperintense with minimal heterogeneous enhancement.DWI image at b factor of 1000 s/mm 2 (I) shows low signal intensity of the lesion.ADC map shows high signal intensity of the mass with high ADC value (1.4 × 10 -3 mm 2 /s).Axial CT image soft window showed the mass, axial CT soft tissue and bone window at the same level (L and M) and sagittal images (N and O) confirmed the extent of the mass with C2 invasion.Diagnosis: oropharyngeal chordoma

Table 1
Baseline characters of examined patients with oral and oropharyngeal masses N.B: more than one symptom could be found in the same patient

Table 2
Exact sites of oral and oropharyngeal lesions in the examined patients

Table 4
Ultrasound findings for carcinoma ex pleomorphic adenoma versus pleomorphic adenoma in studied group

Table 5
CT findings in benign and malignant tumors

Table 3
Result of histopathology in the examined patients with oral and oropharyngeal masses

Table 6
MRI findings in benign and malignant tumors in the examined patients with oral and oropharyngeal masses P value < 0.01 is highly statistically significant *

Table 7
Comparison between CT and MRI for diagnosis of oral and oropharyngeal masses in examined patients P value < 0.01 is highly statistically significant *