Application Of Mr Diffusion Weighted Imaging In Precise Radiotherapy And Evaluation Of The Effect In Esophageal Carcinoma

Objective: By observing the application of target delineation and the changes of apparent diffusion coefficient (ADC) value before and after radiotherapy in using chest MR diffusion-weighted imaging (DWI) ,and to explore the application of MR Diffusion Weighted imaging in precise radiotherapy and evaluation of the effect in esophageal carcinoma.Methods: Thirty-seven patients with potentially radical radiotherapy and biopsy-proven esophageal cancer from March 2010 to January 2011 were included in this study.All patients were taken esophagogram and esophagoscope. Fixed by a heat plastic device, each patient was examined by MRI DWI and CT scan using the same position as the radiotherapy treatment. All images obtained were transmitted to treatment planning system by local area network and fusioned with CT according to bony structures by Syntegra software,delineating the gross tumor volume(GTV) and developing radiation therapy planning. Prescription dose : 54-61.2 Gy. All patients were examined with conventional MRI (T1WI, T2WI sequence) and diffusion-weighted imaging scans(DWI) before and after radiotherapy and then once a mouth after radiotherapy, following up 1-3 months.(1)The tumor lengths were compared measured by esophagogram, esophagoscope, CT and MRI. Also the tumor transverse diameters were compared between CT and MRI DWI image. (2)To redetermine mediastinal lymph nodes which is metastasised according to CT and MRI DWI respectively, and compare the difference of ADC values of metastasised lymph nodes diagnosed by CT and MRI DWI with which diagnosed by MRI DWI only, and observe the differences in clinical stages. (3) For each patient, two separate GTVs were defined, one based on CT (GTV-ct) and another one based on MRI DWI(GTV-mri) respectively. To compare the size of volume and the diversity of upper and lower bounds of GTV-ct and GTV-mri.(4)To measur the length of tumor and the ADC value of normal tissue and tumor using MRI DWI before and after radiotherapy. (5) Following up 1-3 months, to compare the difference of ADC values of tumor betweenⅠgroup(the patients whose high signal disappeared in DWI sequences) andⅡgroup(the patients whose high signal did not disappeare in DWI sequences). To observe the action of MRI in Prognosis.(6)To Evaluate the efficacy of the esophagus according to esophagogram after radiotherapy and observe the influence of the ADC value. Statistical analysis was performed using an SPSS statistical package (Version 16.0).Results: (1) The esophageal lesions and lymph nodes of three patients had no sige in DWI sequences.(one of the three is early esophageal cancer). Tumor lengths of esophagogram,esophagoscope,CT and MRI were: 5.70cm,6.06cm,7.97cm,5.79cm respectively in Remaining patients.The lengths between CT and esophagogram, CT and esophagoscope, CT and MRI had statistical significance, P=0.001,0.006,0.002 respectively. The greatist diameters of tumor shown on CT and MRI were 3.79cm and 3.81cm respectively. Then were not statistical significance between CT and MRI. P=0.751. (2) 78 lymph nodes were assessed positive on CT image,68 on the MRI DWI image and 53 on both. MRI DWI image excluded 25 positive lymph nodes assessed by CT(7 of them located in Aorta - pulmonary artery window and 6 of them were paratracheal lymph nodes); also confirmed 15 negative lymph nodes excluded by CT (6 of them were paraesophageal lymph nodes and 3 were hilar lymph nodes). The average ADC value of lymph nodes assessed by CT and MRI was 1.73×10-3s/mm2,and that 2.06×10-3s/mm2 by MRI only. Then were not statistical significance. The addition of MRI information altered the clinical stage in 6 patients(6/34). (3) The volumes of GTV-ct and GTV-mri were 45.75mm3 and 38.05mm3 respectively.There were significant difference between the volume of GTV-ct and GTV-mri. P=0.001. On the basis of MRI, CT overrate average 1.28cm on the upper bound of tumor in 29 patients and underrate average 0.38cm in 4 patients; CT overrate average 1.77cm on the lower bound of tumor in 27 patients and underrate average 1.35cm in 4 patients. (4) (b=600)The ADC value of normal esophageal tissues is 3.04±0.55×10-3s/mm2, The ADC value of tumor esophageal tissues is 1.65±0.48×10-3s/mm2;(b=1000)The ADC value of normal esophageal tissues is 2.03±0.34×10-3s/mm2, The ADC value of tumor esophageal tissues is 1.38±0.32×10-3s/mm2.In 33 patients(except 3 patients who had no siges in DWI image and 1patient stopped radiotherapy because of bone marrow suppression),the length of tumor was 5.37±2.26cm in DWI image before radiotherapy and 2.11±1.95cm after radiotherapy.The ADC value of tumor is 1.65±0.48×10-3s/mm2 before radiotherapy and 2.49±0.57×10-3s/mm2 after radiotherapy. There were statistical significance. (5) The average ADC value of tumor was increased 0.99×10-3s/mm2 inⅠgroup before and after radiotherapy,and 0.63×10-3s/mm2 inⅡgroup,P=0.035, there wes significant difference. (6) Assessment of Efficacy:in 36 patients(except 1patient stopped radiotherapy because of bone marrow suppression), esophagogram:complete remission(CR) 21 patients,partial remission(PR) 15 patients.In 4 of 21 patients still has high sign in DWI image,7 of 15 had no high sign in DWI image. So MRI:CR 24 patients,PR 12 patients,the ADC value of CR patients assessed by esophagogram was lower than that of CR patients assessed by MRI after radiotherapy, the ADC value of PR patients assessed by esophagogram was higer than that of PR patients assessed by MRI after radiotherapy.Conclusion: Tumor lengths measured on MRI and esophagogram had the optimal approximation. MRI was easy to find paraesophageal lymph nodes easily.By the additional MRI information, the Target range and clinical stage were alerted in some patients of esophageal carcinoma. The ADC value of normal esophageal tissues was higer than that of tumor and mediastinal metastatic lymph node. MRI could provide important clinical information in evaluating the radiotherapy effect and infering prognosis early for esophageal cancer.