Value of Diffusion-Weighted Imaging Combined with Susceptibility-Weighted Imaging in Differentiating Benign from Malignant Parotid Gland Lesions

Abstract

BACKGROUND The aim of this study was to investigate the diagnostic value of diffusion-weighted imaging (DWI) in combination with susceptibility-weighted imaging (SWI) for differentiating benign parotid gland lesions from malignant ones. MATERIAL AND METHODS This retrospective study was approved by the Ethics Committee of our hospital. A total of 36 patients (26 benign cases and 10 malignant cases) were confirmed by surgical pathology. The apparent diffusion coefficient (ADC), normalized ADC (ADCNormalized), intratumoral susceptibility signals (ITSS), and morphological characteristics were analyzed with SPSS 19.0 software. RESULTS The mean ADC values of parotid gland lesions was not different between malignant and benign lesions (P=0.07), while the differences between ADCNormalized (P=0.026) and ITSS grading (P=0.014) were statistically significant. Logistic regression analysis identified use of ADCNormalized and ITSS as the only independent predictor of malignant lesions (odds ratio 0.038; 95% confidence interval 0.001~0.988; P=0.011) and (odds ratio 4.867; 95% confidence interval 1.442~16.423; P=0.049), respectively. The optimum threshold of the ADCNormalized values was -0.45%, ITSS grade was 2, the corresponding areas under the receiver operating characteristic curve (AUC) were 0.750 and 0.787 respectively, and the combination of the 2 was 0.846. CONCLUSIONS DWI integrated with SWI can significantly improve the diagnostic efficacy in distinguishing benign from malignant parotid lesions.

Figure 1

Images in a 28-year-old man with pleomorphic adenoma. A parotid gland tumor is imaged with (A) Apparent diffusion coefficient (ADC) map, which illustrates the regions of interest placement for ADC measurements; ADC value is 1.559×10⁻³ mm²/S, ADC _Normalized value is 79.8%. (B) Intratumoral susceptibility signals (ITSS) map; ITSS is grade 1.

Figure 2

Images in a 47-year-old man with Warthin’s tumors. A parotid gland tumor is imaged with (A) apparent diffusion coefficient (ADC) map, which illustrates the regions of interest placement for ADC measurements, ADC value is 0.604×10⁻³ mm²/s, ADC_Normalized value is −31%; (B) Intratumoral susceptibility signals (ITSS) map; ITSS is grade 1.

Figure 3

Images in a 58-year-old man with achromatosis of the parotid gland. A parotid gland tumor is imaged with (A) apparent diffusion coefficient (ADC) map, which illustrates the regions of interest placement for ADC measurements. ADC value is 0.805×10⁻³ mm²/s, ADC_Normalized value is −19.7%. (B) Intratumoral susceptibility signals (ITSS) map; ITSS is grade 3.

Figure 4

Receiver operating curve (ROC) in relation to compared diagnostic effectiveness of normalized apparent diffusion coefficient (ADC), intratumoral susceptibility signals (ITSS), and normalized ADC combined with ITSS.