| Part1Application of MR Diffusion-Weighted Imaging in Salivary Glands with Gustatory StimulationPurpose:To evaluate the functional changes in salivary glands with gustatory stimulation by using MR diffusion-weighted imaging (DWI).Materials and methods:A prospective study was conducted on30patients with nasopharyngeal carcinoma who had normal salivary function. A DWI sequence was performed on the salivary glands at rest, then continually repeated on the parotid immediately after oral ascorbic acid stimulation over a period of21minutes (once every3minutes). The multiple b-values (0,400,600,800,1000s/mm2) were used. Apparent Diffusion Coefficients (ADC) maps were evaluated with a manually placed region of interest including the entire salivary glands bilaterally. The ADC of each gland was obtained by taking the mean of values on three contiguous sections containing the largest areas of the gland. The paired two-tailed Student t test was used to compare the ADC values of the parotid and the submandibular glands at rest, and of the parotid before and after stimulation.Results:The mean ADC value at rest was significantly lower in the parotid (1.23±0.12×10-3mm2/s)than in the submandibular glands(1.34±0.07×10-3mm2/s P<0.001). After acid stimulation, the ADC value increased from the baseline to1.41±0.19×10-3mm2/s firstly and then fluctuated at the following time, with a peak value of1.49±0.20×10-3mm2/s and the average value of1.36±0.17×10-3mm2/s (P<0.001). The minimum value (1.24±0.14×10-3mm2/s) was not significantly different compared to the baseline value (P=0.189).Conclusion:MR DWI can noninvasively evaluate the physiologic changes of salivary glands for nasopharyngeal carcinoma patients before and after acid stimulation. Part2Diffusion-Weighted MR Imaging of Salivary Glands with Gustatory Stimulation To Evaluate Salivary Function before and after Radiotherapy Purpose:Salivary gland hypofunction is the most prominent complication in patients with head and neck carcinoma after radiotherapy (RT).Our aim was to investigate the value of DWI combined with gustatory stimulation as a noninvasive tool for assessing salivary gland function in patients before and after RT.Materials and methods:Twenty-three consecutive patients with nasopharyngeal carcinoma were examined with a3T unit before the start of treatment,1week and1year after the completion of RT. Clinical xerostomia was also assessed at the same time as MRI, according to the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer (RTOG/EORTC) morbidity scoring system. A DWI sequence was performed on the salivary glands at rest, then continually repeated on the parotid immediately after oral ascorbic acid stimulation over a period of21minutes (once every3minutes). The multiple b-values (0,400,600,800,1000s/mm2) were used. Apparent diffusion coefficient (ADC) maps for salivary glands before and after stimulation were calculated. The time to peak ADC and the range of increase with stimulation were also obtained. The changes on salivary glands before and after RT were observed. Findings were also compared with clinical data.Results:The mean dose of the parotid glands (40.09±4.31Gy) was lower than that of the submandibular glands (59.78±3.58Gy, P<0.001). At1week post-RT, clinical xerostomia changed from Grade0to Grade2in all patients. At1year post-RT, xerostomia decreased to Grade1on13patients (Group1), and the remaining10patients were still Grade2(Group2). The ADC of parotid glands increased1week after RT, then decreased1year after RT (P<0.001). The time to peak ADC on parotid gland and the ADC of submandibular glands showed an increase after RT (P<0.001), without a decrease (P=0.957, P=0.581). A similar response to gustatory stimulation was found after RT. The ADC on the parotid glands increased after acid stimulation and the minimum ADC was not significantly different from the resting ADC both1week and1year after RT (P0.001).Grouped by clinical xerostomia at1year post-RT, the mean dose to parotid glands on Group1was significantly lower than that on Group2(P<0.001), but there was no difference on submandibular glands (P=0.100). For parotid glands at1week post-RT, the minimum and the average ADC during stimulation and the time to peak ADC on Group1were lower than Group2(P=0.012, P=0.025, P=0.019), and the resting ADC was lower than the minimum ADC on Group2(P=0.037); at1year post-RT, the ADC range of increase on Group1was higher than Group2(P=0.048). For submandibular glands at1week post-RT, the mean ADC on Group1was higher than Group2(P=0.013); at1year post-RT, a decrease was observed on Group1(P=0.017) but not on Group2(P=0.222).Conclusion:The ADC value is a sensitive indicator for salivary gland dysfunction, and it changes earlier than clinical xerostomia. MR DWI is potentially useful for noninvasively evaluating functional changes in the salivary glands and the severity of xerostomia before and after RT. Part3Utility of Three Dimension Fast Recovery Fast Spin Echo Sequences in MR Sialography:Comparison before and after Gustatory StimulationPurpose:To evaluate the utility of three dimension fast recovery fast spin echo (3D-FRFSE) sequence for the visualization of salivary gland ducts in MR sialography and to optimize the technology by comparing images before and after gustatory stimulation.Materials and methods:MRI was performed with a3T unit and an8-channel neurovascular head and neck array coil on27patients with nasopharyngeal carcinoma who had normal salivary function. For MR sialography,3D-FRFSE sequences were applied, the images encompassed the full volume of both the parotid and the submandibular glands, and the acquisition time of one sequence was about8-9min. MR sialography was performed once at rest, then repeated after gustatory stimulation with six100-mg tablets of commercially available ascorbic acid. The branches of salivary ducts were observed, and morphological scoring criteria of the salivary gland system were used to evaluate the visibility of the salivary ducts. The images before and after stimulation were compared.Results:The parotid and submandibular duct systems were clearly demonstrated with3D-FRFSE sequence in MR sialography, and the third-order branches in some parotid gland were visualized. At rest, the visualization rates of second-order branches in parotid and submandibular glands were61.1%、20.4%respectively, and after stimulation the rates increased to85.2%、31.5%respectively (P<0.001, P=0.031). The average resting parotid and submandibular ducts scores were3.57±0.63、1.83±0.38respectively, and the stimulated scores were4.85±0.66、2.46±0.69respectively, higher than the resting values (both P<0.001).Conclusion:The3D-FRFSE sequences can be used in MR sialography for visualization of salivary duct system, and the quality of the images could be improved by combining with gustatory stimulation. Part4Objective Evaluation of salivary duct injury using MR Sialography: Follow-up of radiation-induced xerostomia in head and neck carcinomasPurpose:To explore the utility and the clinical value of magnetic resonance sialography as a noninvasive tool for evaluating radiation-induced xerostomia in patients with head and neck carcinomas.Materials and methods:Twenty-one consecutive patients with nasopharyngeal carcinoma were examined with a3T unit before the start of treatment,1week and1year after the completion of RT. Clinical xerostomia was also assessed at the same time as MRI, according to the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer (RTOG/EORTC) morbidity scoring system. For MR sialography,3D-FRFSE sequences were applied, the images encompassed the full volume of both the parotid and the submandibular glands, and the acquisition time of one sequence was about8-9min. MR sialography was performed once at rest, then repeated after gustatory stimulation with six100-mg tablets of commercially available ascorbic acid. Morphological scoring criteria of the salivary gland system were used to evaluate the visibility of the salivary ducts. The resting and stimulated data before and after radiotherapy were compared.Results:The mean dose of the parotid glands (39.73±4.30Gy) was lower than that of the submandibular glands (59.34±3.24Gy, P<0.001). At1week post-RT, clinical xerostomia changed from Grade0to Grade2in all patients. At1year post-RT, xerostomia decreased to Grade1on12patients (Group1), and the remaining9 patients were still Grade2(Group2). The visibility scores of both parotid and submandibular ducts at rest and after stimulation decreased at1week post-RT (all P<0.001). For the parotid ducts, the visibility scores improved at1year post-RT both at rest and under stimulation (P=0.002, P=0.001respectively), but not for the submandibular ducts.Grouped by clinical xerostomia at1year post-RT, the mean dose to parotid glands on Group1was significantly lower than that with Group2(P=0.008), but there was no difference on submandibular glands (P=0.962). At1year post-RT, the visibility of parotid ducts on Group1was better than that on Group2.Conclusion:MR sialography can successfully visualize the changes of salivary duct system before and after radiotherapy and demonstrate the difference between different grades of xerostomia. It has the potential to noninvasively evaluate salivary gland function and follow up patients with radiation-induced xerostomia. |
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