Salivary glands: Echo-planar versus PROPELLER diffusion-weighted MR imaging for assessment of ADCs

Purpose: To compare the image distortion and the quantification variation in parotid gland apparent diffusion coefficients (ADCs) on periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) versus echoplanar diffusion-weighted (DW) magnetic resonance (MR) images and to investigate the relationship between parotid gland ADC and parotid gland fat content. Materials and Methods: This prospective study was approved by a local institutional review board. Written informed consent was obtained from all 33 enrolled healthy volunteers (15 men, 18 women; mean age, 36.4 years ± 11.8 [standard deviation]). All participants underwent 1.5-T non - fat-saturated and fat-saturated PROPELLER DW MR imaging as well as 1.5-T nonaccelerated and twofold-accelerated echo-planar DW MR imaging. Image distortion on the DW images was qualitatively scored, and parotid ADC was quantitatively analyzed. The correlation between parotid ADC and parotid fat content was evaluated by using linear regression analysis. Wilcoxon signed rank and t tests were used for statistical analysis, with Bonferroni correction applied for multiple comparisons. Results: Echo-planar DW images showed distortion, which was completely eliminated on the PROPELLER DW images. The mean parotid ADCs measured with non - fat-saturated PROPELLER (0.670 x 10-3 mm2/sec ± 0.149), nonaccelerated echo-planar (0.892 x 10-3 mm2/sec ± 0.128), twofold-accelerated echo-planar (1.088 x 10-3 mm2/sec x 0.124), and fat-saturated PROPELLER (1.307 x 10-3 mm2/sec ± 0.217) DW imaging differed significantly from one another (P <.001 for all comparisons). Parotid ADC had a significant negative correlation with parotid fat content (x) measured at non - fat-saturated PROPELLER DW imaging: ADC = -0.0087x + 1.1173 (r = 0.80, P <.001). Conclusion: PROPELLER DW imaging pulse sequences can yield distortion-free images for parotid ADC measurements and enable quantitative evaluation of the relationship between parotid ADC and parotid fat content.