Fig 1.
T2WI and DWI of a patient with demonstration of ROI drawing for parotid glands.
Parotid glands are contoured (blue polygons) on T2WI for volume measurement (1A). For measurement of parotid ADC, ROIs are drawn about 2-mm medially to the margin of glands with excluding visible vessels (while polygons) on DWI to avoid partial volume effect (1B).
Fig 2.
Percentage of dry mouth grade versus MR stage, showing continuous decrease of grade 2 xerostomia percentage as MR stage increased.
Fig 3.
A 54-year-old patient with nasopharyngeal carcinoma with a radiation dose to the tumor, right parotid gland and left parotid gland of 72 Gy, 26.49 Gy and 24.75 Gy, respectively.
Serial axial T2-weighted images of were obtained at MR stage 0 (3A; before radiotherapy), 1 (3B; 53 days), 2 (3C; 270 days) and 3 (3D; 435 days), respectively. The parotid glands (arrows) showed perceivable shrinkage at stage 1 followed by gradual restoration at stage 2 and stage 3.
Fig 4.
Parotid volume at different MR stages in nasopharyngeal carcinoma patients treated by intensity-modulated radiotherapy.
Compared to MR stage 0 (before radiotherapy), parotid volume reduced significantly at stage 1 (≦100 days) and stage 2 (101 days to 1 year). The parotid volume is smallest at stage 1 with gradual increase at stage 2 and stage 3 (>1 year).
Fig 5.
Parotid ADC at different MR stages in nasopharyngeal carcinoma patients treated by intensity-modulated radiotherapy.
Compared to stage 0 (before radiotherapy), parotid ADC increased significantly at all MR stages. After initial elevation at stage 1 (≦100 days), parotid ADC gradually decreased at stage 2 (101 days to 1 year) and stage 3 (>1 year).
Fig 6.
Scatter plots of parotid ADC versus parotid volume.
Linear regression of parotid ADC versus parotid volume at all MR stages shows that the parotid ADC is negatively correlated to the parotid volume with significance (P < .005).
Fig 7.
Parotid volume versus xerostomia (7A) and parotid ADC versus xerostomia (7B) in nasopharyngeal carcinoma patients treated by intensity-modulated radiotherapy.
The parotid volume is significant lower in grades 1 and 2 as compared to grade 0 (P < .005). On the contrary, the parotid ADC was significant higher in grades 1 and 2 as compared to grade 0 (P < .005). Note: Grade 0 represents no symptom of dry mouth; grade 1 represents slight dryness of the mouth with good response on stimulation; grade 2 represents moderate dryness with poor response on stimulation.