Elsevier

European Journal of Radiology

Volume 81, Issue 11, November 2012, Pages 3306-3312
European Journal of Radiology

Diagnostic value of dynamic contrast-enhanced MRI for submucosal palatal tumors

https://doi.org/10.1016/j.ejrad.2012.04.009Get rights and content

Abstract

Objectives

To evaluate the diagnostic value of dynamic contrast-enhanced MRI (DCE-MRI) for differentiating between benign and malignant tumors in the palate.

Materials and methods

26 patients with submucosal palatal tumors were preoperatively examined using DCE-MRI. Their maximum contrast index (CImax), time of CImax (Tmax), and washout ratios (WR300 and WR600) were determined from contrast index curves. The submucosal palatal tumors were divided into two groups according to their Tmax values: the early enhancement group (Tmax < 300 s) consisted of 9 malignant tumors and 6 benign tumors, while the late enhancement group (Tmax  300 s) included one malignant tumor and 10 benign tumors. We compared the following DCE-MRI parameters between the benign and malignant tumors: CImax and Tmax in all cases and CImax, Tmax, and the washout ratios in the early enhancement group. In addition, we performed a regression analysis of the relationships between tumor size and DCE-MRI parameters; i.e., CImax, Tmax, and washout ratios, among the malignant salivary gland tumors and pleomorphic adenomas.

Results

In all cases and the early enhancement group, significant differences in Tmax were detected between the benign and malignant tumors (P < 0.001 and P < 0.05, respectively), and the optimal Tmax cutoff value for differentiating between them was found to be 165 s. None of the other parameters displayed significant differences between the benign and malignant tumors. Only the WR600 of the pleomorphic adenomas was significantly correlated with tumor size (R2 = 0.92, P < 0.001).

Conclusions

Tmax is a useful parameter for distinguishing between benign and malignant submucosal palatal tumors.

Introduction

The palate separates the oral cavity from the nasal cavity and is divided into two parts, the anterior bony hard palate, and the posterior soft palate. Palate tumors include a variety of pathological types, and approximately 50% of palate tumors are malignant tumors [1]. Squamous cell carcinoma is the most common malignancy in the palate and is relatively easy to identify as a malignant lesion by inspection and palpation. On the other hand, in palate tumors that present as a submucosal mass such as minor salivary gland tumors, imaging diagnosis could play an important role in distinguishing between benign and malignant lesions.

Magnetic resonance imaging (MRI) is used to diagnose palate tumors because it is the most useful modality for analyzing the internal structures of lesions due to its superior soft tissue contrast ability. However, palate tumors are often noticed by patients when they are still small as they occur at visible and palpable sites, and it is often difficult to observe the internal structures of small tumors on routine MR images. Several authors have reported that dynamic contrast-enhanced MRI (DCE-MRI) parameters and time signal intensity curves (TIC) are useful for diagnosing certain tumors of the head and neck region [2], [3], [4], [5], [6], [7]. Therefore, we considered that DCE-MRI, which is able to observe not only the internal structures of tumors, but also changes in their signal intensities over time, might provide useful information for the differential diagnosis of palate tumors.

We previously reported that the DCE-MRI parameters of minor salivary gland tumors in the oral cavity contributed little to their differential diagnosis, but this study included several tumors that arose at sites other than the palate [8]. As tumors are supplied with blood from the surrounding tissues, evaluating the DCE-MRI parameters of tumors arising at a single site might provide useful information for their diagnosis. However, there are few reports about the DCE-MRI parameters of tumors arising at a single site in the head and neck region, and the DCE-MRI findings of palate tumors have only been described in one report of 9 cases [7], [9], [10]. The purpose of the present study was to evaluate the diagnostic value of the DCE-MRI parameters of palate tumors.

Section snippets

Patients

Thirty-four patients who underwent DCE-MRI were histopathologically diagnosed with palate tumors at our hospital between February 1999 and August 2011. Of the 34 patients, six were excluded from this study because their MR examinations were performed with different MR devices from those of the other patients. Furthermore, we excluded one patient who underwent DCE-MRI using different sequence parameters from the other subjects and one patient whose lesion was too small to allow its signal

All cases

There was no significant difference between the mean CImax value (P = 0.562) of the benign tumors and that of the malignant tumors (Fig. 4a). A significant difference in Tmax (P < 0.001) was detected between the benign and malignant tumors (Fig. 4b). In ROC analysis, we found that a Tmax cutoff value of 165 s provided the best combination of sensitivity (100%), specificity (70.0%), and accuracy (88.5%) (Table 2).

Early enhancement group (Tmax < 300 s)

Table 3 summarizes the CImax, Tmax, WR300, and WR600 values of the early enhancement

Discussion

Among head and neck lesions, the TIC of malignant tumors commonly display rapid increases, whereas those of benign tumors show gradual increases. However, regardless of whether delayed images are obtained or the length of the period between contrast medium injection and the delayed images being obtained, clinicians can obtain various subjective impressions from the shapes of TIC. Takashima et al. classified the TIC of 79 head and neck lesions into five groups according to the time at which they

References (16)

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