Menoufia Medical Journal

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 31  |  Issue : 1  |  Page : 236--243

Computed tomography versus magnetic resonance imaging in the diagnosis of pharyngeal lesions


Abd El Latif I El Rashedy, Essam A Behiary, Ayman A Abd El Fattah, Anas M El Dahshan 
 Department of Otolaryngology, Menoufia University, Menoufia, Egypt

Correspondence Address:
Anas M El Dahshan
Shibin El Kom, Menoufia
Egypt

Abstract

Objectives The aim of this study was to assess the reliability of computed tomography (CT) and MRI in evaluating pharyngeal lesions by comparing the two imaging modalities. Background The pharynx is a region of considerable anatomical and functional complexity, making the accurate diagnosis of pharyngeal lesion a challenging task. CT or MRI is performed for pretherapeutic assessment of pharyngeal lesions. Both can supply the information needed by the clinician for adequate treatment planning. Patients and methods Forty patients with pharyngeal lesions were evaluated using CT and/or MRI according to the decision of the treating physician. The results of imaging were assessed based on the corresponding histopathological diagnosis to define the true benign, true malignant, false benign, and false malignant results. Statistical analysis was performed to calculate the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of each technique, and the correct results of the two techniques were compared in 28 patients subjected to both. Results The study included 40 patients with lesions distributed among three anatomical sites: the nasopharynx (15), the oropharynx (nine), and the hypopharynx (16). The lesions included 23 malignant, nine benign neoplastic, and eight inflammatory lesions. CT was performed for all patients, whereas MRI was performed for 28 patients. CT revealed a sensitivity of 78.2%, a specificity of 70.6%, a diagnostic accuracy of 75%, a positive predictive value of 78.2%, and a negative predictive value of 70.6%. MRI revealed a sensitivity of 89.5%, a specificity of 77.8%, a diagnostic accuracy of 85.7%, a positive predictive value of 89.5%, and a negative predictive value of 77.8%. On comparing the overall results of CT and MRI, there was a nonsignificant difference (P = 0.19). Conclusion Both CT and MRI are effective imaging modalities for evaluating a pharyngeal mass. No significant difference was found between them as regards reaching the correct diagnosis of pharyngeal lesion.



How to cite this article:
El Rashedy AI, Behiary EA, Abd El Fattah AA, El Dahshan AM. Computed tomography versus magnetic resonance imaging in the diagnosis of pharyngeal lesions.Menoufia Med J 2018;31:236-243


How to cite this URL:
El Rashedy AI, Behiary EA, Abd El Fattah AA, El Dahshan AM. Computed tomography versus magnetic resonance imaging in the diagnosis of pharyngeal lesions. Menoufia Med J [serial online] 2018 [cited 2019 Aug 22 ];31:236-243
Available from: http://www.mmj.eg.net/text.asp?2018/31/1/236/234212


Full Text



 Introduction



The pharynx is a region of considerable anatomical and functional complexity, making the accurate diagnosis of pharyngeal lesions a challenging task. Many lesions in this region originate from the mucosa and are detectable by the clinician. However, the submucosal tumor extension and the possible regional and distant disease spread cannot be completely assessed based on clinical examination alone [1].

Modern imaging modalities visualize the pharyngeal structures to an unprecedented level of detail. If carefully performed and interpreted, these techniques allow a comprehensive evaluation of the extent of pharyngeal lesions [1]. Computed tomography (CT) or MRI is performed for pretherapeutic assessment of these lesions. Both techniques can supply the information needed by the clinician for adequate treatment planning [2].

The advantages of MRI over CT in the evaluation of pharyngeal lesions are its superior soft tissue contrast resolution and the absence of radiation exposure. Overall, the image quality is not or less hampered by the presence of dental fillings compared with CT; nevertheless, MRI studies may be severely jeopardized by metallic implants [3].

The aim of this work was to assess the reliability of CT and MRI in evaluating pharyngeal lesions in terms of sensitivity, specificity, and diagnostic accuracy by comparing the two imaging modalities.

 Patients and Methods



The study protocol was approved by the ethical committee of Menoufia university and a written consent was obtained from every participant with pharyngeal lesions who were retrieved from the outpatient clinic of the Otorhinolaryngology Department, Menoufia University Hospital.

Patients selected for this study included those with acute or insidious onset of pharyngeal lesions. Patients with previous operation on the neck, previous radiotherapy to the neck, or patients with congenital lesions were excluded from this study. Known hypersensitivity to contrast materials used with CT and MRI or a history of cardiac pacemakers or any metallic implant contraindicated with MRI were exclusion criteria for our study.

All patients were subjected to the following: full history taking, including age, sex, onset and course of swelling, and symptoms of inflammation (fever and pain) or malignancy (loss of weight and anorexia); general examination, including body build and vital signs; neck examination for each case for assessment of the site, size, consistency, surface, borders, and mobility of any neck swelling; and thorough ear, nose, and throat examination with emphasis on pharyngeal examination for each case.

Patients with pharyngeal lesions were evaluated using CT or MRI according to the decision of the physician and the need for the imaging modality to reach a diagnosis.

Computed tomography with contrast

CT with contrast was performed around matrix 512 × 512 pixels during bolus injection of intravenous contrast (gastrografin contrast) stressed on axial cuts. The whole neck was scanned with 5 mm cuts, whereas the level of the larynx was scanned with 1–3-mm cuts. Comments on CTs were documented with emphasis on the lesion site, size, shape, spread, relations, and effects to surroundings and lymph nodes. The site of the lesion, the size of primary disease, the extent of involvement, enhancement pattern, calcification, necrosis, local extension, and distant metastasis were reported.

Magnetic resonance imaging with intravenous contrast

MRI with intravenous contrast (gadolinium) was performed using a 1.5 T initially, and localizer images in the coronal, sagittal, and transverse planes were obtained. Subsequently, T1-weighted (T1W), T2-weighted (T2W), and postcontrast images (after administration of 10 ml of intravenous gadolinium) were obtained. Imaging parameters included a slice thickness of 3 or 4 mm with a 0–1-mm intersectional gap, a field of view of 20 × 20 cm or less, and acquisition matrix 256 × 256.

The definite diagnosis of each case of pharyngeal lesion was made based on the result of histopathological examination of tissue biopsy either Tru-cut biopsy or excisional biopsy.

Outcome assessment

These results of imaging studies (CT and MRI) were divided into malignant and benign lesions. The latter included benign tumors and inflammatory lesions.

Malignant lesions of the nasopharynx were diagnosed in CT by asymmetry of the fossa of Rosenmüller manifested as blunting or obliteration, thickening of the deglutition muscle layer caused by tumor infiltration, obliteration or displacement of the parapharyngeal space, or widened preoccipital soft tissue width in axial cuts. On the other hand, nasopharyngeal malignancy on MRI was diagnosed by intermediate signal intensity (higher than the muscle signal) on T2W images, low signal intensity on T1W images, and enhancement to a lesser degree than does normal mucosa, submucosal extension to palatini muscles, or displacement or infiltration of the pharyngobasilar fascia, which is visualized by MRI only or extension through the sinus of Morgagni.

Malignant lesions of the oropharynx were diagnosed in CT by space-occupying growth, obliteration of fat planes, infiltration of muscles, bony destruction, or peripheral enhancement with intravenous contrast. On the other hand, oropharyngeal malignancy was diagnosed on MRI by being hypointense to muscle on T1W sequence, hyperintense to muscle on T2W sequence, enhanced with gadolinium contrast or bone marrow, perineural and prevertebral, or pterygopalatine fossa involvement.

Malignant lesions of the hypopharynx were diagnosed in CT by a solid soft tissue nodule or region of superficial thickening with increased enhancement. On the other hand, hypopharyngeal malignancy was diagnosed on MRI by intermediate-to-low signal mass in T1W images, intermediate-to-high signal in T2W images, and enhanced masses in T1-contrasted images.

The results of imaging were assessed based on the corresponding histopathological diagnosis to define the true benign, true malignant, false benign, and false malignant results.

Statistical analysis

The number of cases with true benign, true malignant, false benign, and false malignant results for each imaging modality was used to calculate sensitivity, specificity, diagnostic accuracy, precision (positive predictive value), and negative predictive value as follows:

Sensitivity = true-positive cases/(true-positive cases + false-negative cases).

Specificity = true-negative cases/(true-negative cases + false-positive cases).

Diagnostic accuracy=(true-positive cases + true-negative cases)/(true positive + true negative + false positive + false negative).

Precision (positive predictive value)=true-positive cases/(true-positive cases + false-positive cases).

Negative predictive value = true-negative cases/(true-negative cases + false-negative cases).

The previous parameters were calculated for each imaging modality as overall and then for each imaging modality in each anatomical location of the pharynx considering malignant cases as positive and benign cases as negative.

The results of CT and MRI for cases that were subjected to both modalities were used to compare the two imaging modalities in diagnosing lesions of the neck using the c2-test or Fischer exact test, with P  value less than 0.05 considered significant and P  value less than 0.01 highly significant.

 Results



The current study included 40 patients, comprising 28 (70%) male and 12 (30%) female patients. Their ages ranged from 18 to 63 years. The study included patients with lesion distributed among three anatomical sites: the nasopharynx (15 patients), the oropharynx (nine patients), and the hypopharynx (16 patients). The pharyngeal lesions included 23 malignant lesions, nine benign tumors, and eight inflammatory lesions. CT was performed for all patients, whereas MRI was performed for 28 patients [Table 1].{Table 1}

Evaluation of the overall results of CT imaging revealed a sensitivity of 78.2%, a specificity of 70.6%, a diagnostic accuracy of 75%, a positive predictive value of 78.2%, and a negative predictive value of 70.6%. Evaluation of the overall results of MRI revealed a sensitivity of 89.5%, a specificity of 77.8%, a diagnostic accuracy of 85.7%, a positive predictive value of 89.5%, and a negative predictive value of 77.8% [Table 2] and [Figure 1] and [Figure 2].{Table 2}{Figure 1}{Figure 2}

Evaluation of the results of CT imaging in nasopharyngeal lesions revealed a sensitivity of 77.8%, a specificity of 66.7%, a diagnostic accuracy of 73.3%, a positive predictive value of 77.8%, and a negative predictive value of 66.7%. Evaluation of the results of MRI in nasopharyngeal lesions revealed a sensitivity of 85.7%, a specificity of 75%, a diagnostic accuracy of 81.8%, a positive predictive value of 85.7%, and a negative predictive value of 75% [Table 3] and [Figure 3].{Table 3}{Figure 3}

Evaluation of the results of CT imaging in oropharyngeal lesions revealed a sensitivity of 80%, a specificity of 75%, a diagnostic accuracy of 77.8%, a positive predictive value of 80%, and a negative predictive value of 75%. Evaluation of the results of MRI in oropharyngeal lesions revealed a sensitivity of 100%, a specificity of 66.7%, a diagnostic accuracy of 85.7%, a positive predictive value of 80%, and a negative predictive value of 100% [Table 4] and [Figure 4].{Table 4}{Figure 4}

Evaluation of the results of CT imaging in hypopharyngeal lesions revealed a sensitivity of 77.8%, a specificity of 71.4%, a diagnostic accuracy of 75%, a positive predictive value of 77.8%, and a negative predictive value of 71.4%. Evaluation of the results of MRI in hypopharyngeal lesions revealed a sensitivity of 87.5%, a specificity of 100%, a diagnostic accuracy of 90%, a positive predictive value of 100%, and a negative predictive value of 66.7% [Table 5] and [Figure 5].{Table 5}{Figure 5}

On comparing the overall results of CT and MRI as correct and incorrect diagnosis, there was a nonsignificant difference between the two modalities (P = 0.19) [Table 6] and [Figure 6],[Figure 7],[Figure 8].{Table 6}{Figure 6}{Figure 7}{Figure 8}

 Discussion



Proper evaluation of pharyngeal mass is essential for proper approach of management. Although histopathological diagnosis remains the only definitive tool to determine the nature of a lesion, imaging constitutes an important step of investigation. It helps us to have a clear-cut idea about the expected pathology of the lesion and it provides us with its limits of extension and degree of involvement of adjacent structures. Thus, imaging gives us the plan for the next invasive step to reach the pathological diagnosis and hence the treatment protocol.

The current study is a prospective case series study that attempts to evaluate the validity of two common imaging modalities, CT and MRI, in 40 patients suffering from pharyngeal lesions. The study focused on these two modalities because they are the most widely available, highly prescribed, and affordable imaging techniques. Other modalities such as PET and PET/CT are not always available or affordable. Although ultrasound examination is superior to CT and MRI in terms of availability and cost and it is the first option striking the mind for evaluating a neck mass, it is not always applicable for every anatomical region, especially the nasopharynx, oropharynx, and hypopharynx. Thus, application of ultrasound is not involved in this study.

Our study did not involve ordering CT and MRI for every patient because this has not been applicable, being dependent on the decision of the treating physician. This decision can proceed from CT to MRI or choose CT or MRI from the start depending on the most convenient method that will help in establishing the diagnosis needed to proceed to a more invasive step for biopsy taking. Accordingly, our study included 40 CT and 28 MRI reports. Twenty-eight patients with pharyngeal lesions were subjected to both MRI and CT.

Evaluation of the overall results of CT imaging in our study revealed a sensitivity of 78.2%, a specificity of 70.6%, and a diagnostic accuracy of 75%. Our results are lower than those reported by Shrestha et al. [4], who found that the sensitivity of CT in detecting malignant/benign lesions of the neck was 96.5,%with a specificity of 100% and a diagnostic accuracy of 97.9%. Moreover, Charan et al. [5] found a sensitivity of 95.7%, a specificity of 77.5%, and a diagnostic accuracy of 90% in the diagnosis of neck lesions. This difference can be attributed to interpreter variability between radiologists and to the different sample size.

Evaluation of the overall results of MRI in our study revealed a sensitivity of 89.5%, a specificity of 77.8%, and diagnostic accuracy of 85.7%. These results are higher than the results reported by Laubenbacher et al. [6], who found that the sensitivity and specificity of MRI values in the detection of neck malignancies were 72 and 56%, respectively. This difference can be attributed to the improvement in MRI techniques and protocols with better delineation of tissues. Moreover, Kitagawa et al. [7] found that the sensitivity of pretreatment MRI in detecting malignant primaries in the neck was 78%, whereas the sensitivity and specificity of post-treatment MRI were 100 and 41%, respectively.

To the best of our knowledge, no other study has evaluated CT or MRI in the whole pharynx, nor a specific subsite such as the nasopharynx or the oropharynx. This can explain the difference between the results of the current study and the mentioned studies, which assessed lesions of the whole neck.

CT and MRI of the nasopharynx provide images with significant information and exquisite anatomical detail. Axial and direct coronal plane CT scans (4–5 mm thick) are used to evaluate the nasopharynx and regional anatomy. Thinner sections (2.5–3 mm) should be obtained for smaller lesions and for the evaluation of subtle bone invasion by nasopharyngeal carcinoma. Examination should be carried out with and without iodinated contrast material. Contrast is important for the evaluation of metastatic nodal disease, the base of the skull, and intracranial involvement [8].

In the current study, CT imaging for nasopharyngeal carcinoma showed a sensitivity of 77.8%, a specificity of 66.7%, and a diagnostic accuracy of 73.3%. On the other hand, MRI for nasopharyngeal carcinoma showed a sensitivity of 85.7%, a specificity of 75%, and a diagnostic accuracy of 81.8%. These results are in agreement with the results reported by Liua et al. [9], who performed a systematic review to compare fluorodeoxyglucose FDG-PET, CT, and MRI for the diagnosis of local residual or recurrent nasopharyngeal carcinoma. Twenty-one articles were included in the study. The pooled sensitivity estimates for PET (95%) were significantly higher than that for CT (76%) and MRI (78%). The pooled specificity estimates for PET (90%) were significantly higher than for CT (59%) and MRI (76%). This difference can be attributed to the larger sample size included in the mentioned study. This difference can be attributed to the different sample sizes between our study and this study [9].

The oropharynx is characterized by complex anatomy not always accessible to physical examination, making radiologic imaging a potentially useful supplement for effective diagnosis and follow-up assessment [10].

In the current study, CT imaging for oropharyngeal carcinoma showed a sensitivity of 80%, a specificity of 75%, and a diagnostic accuracy of 77.8%. However, MRI for oropharyngeal carcinoma showed a sensitivity of 100%, a specificity of 66.7%, and a diagnostic accuracy of 85.7%. These results are higher than the results reported by Leslie et al. [11], who assessed the accuracy of CT and MRI in staging of squamous cell carcinoma of the oral cavity and the oropharynx in 51 patients. For staging primary tumors, the accuracy of MRI was 77% and that of CT was 67%. For detecting recurrent tumor, the accuracy of MRI was 89% and that of CT was 100%. Sensitivity for high-risk sites was 60% for clinical assessment, 35% for CT, and 75% for MRI [11].

The spectrum of pathological changes in anatomical sections of the hypopharynx ranges from benign pathologies to hypopharyngeal carcinoma. Besides the clinical status and the endoscopic evaluation, imaging techniques play an important role in pretherapeutic and post-therapeutic diagnostics and in the follow-up of pharyngeal disease patterns, especially for malignant lesions [12].

In the current study, CT imaging for hypopharyngeal carcinoma showed a sensitivity of 77.8%, a specificity of 71.4%, and a diagnostic accuracy of 75%. In the current study, MRI for hypopharyngeal carcinoma showed a sensitivity of 87.5%, a specificity of 100%, and a diagnostic accuracy of 90%. These results are different from the results reported by Zbären et al. [13], who assessed 44 patients with hypopharyngeal cancer with contrast-enhanced CT and MRI at 1.5 T. MRI was more sensitive in detecting neoplastic invasion of cartilage compared with CT (97 vs. 68%). MRI was less specific compared with CT (62 vs. 84%), taking into account the thyroid and cricoid cartilages. There was no difference between the overall accuracy of CT and MRI in detecting neoplastic invasion of cartilage (78 vs. 75%) [13].

Moreover, our results were lower than the results of Dhoot et al. [14], who evaluated 40 biopsy-proven cases of hypopharyngeal carcinoma. Contrast-enhanced CT of the neck was performed for all patients. CT achieved a sensitivity of 92.8%. These differences can be attributed to the different sample sizes.

In the current study we compared the efficacy of CT and MRI in 28 patients with pharyngeal lesions who were subjected to both modalities in terms of correct and incorrect diagnosis.

 Conclusion



Both CT and MRI are effective imaging modalities for evaluating a pharyngeal mass. No significant difference was found between CT and MRI in reaching the correct diagnosis of pharyngeal lesion.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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