| Objective To choose the optimal b value of diffusion weighted imaging(DWI)for characterization of systemic lymphoma,and to evaluate the role of apparent diffusion coefficient(ADC)value and exponent apparent diffusion coefficient(eADC)value in differentiating diagnosis of lymphoma and lymph node metastases respectively.To explore the clinical value of ADC and eADC in evaluating the response after chemotherapy quantitatively in follow-up examination.Materials and Methods Thirty-six patients with lymphoma from Dec.2006 to Jan. 2008 enrolled into the study.All the cases with neck or thoracic and abdominal lymph node involvement were proved pathologically by lymph node biopsy and resection. Twenty-one were male and 15 were female,aged from 11 to 85 years old(mean 52 years).Twenty-six patients with abdominal lymph node metastases proved by clinical or pathologic findings were also included in this study.Among of them,eighteen were male and 8 were female,aged from 25 to 83 years old(mean 58 years).Among of 36 lymphoma patients,follow-up exam were carried out in 14 patients after either 1 or 2 courses of chemotherapy.Among of the 14 patients,9 patients received follow-up study only after 1 course of chemotherapy,3 patients received follow-up study only after 2 course of chemotherapy,2 patients received follow-up study both after 1 course and 2 course of chemotherapy.Among them,7 were male and 7 were female,aged from 21 to 79 years old(mean 49 years).MR scaning were performed on GE 1.5 T Twin Speed Infinity with ExciteⅡscanner with neck-anterior coil or Torsopa phased array coil.SE-EPI-DWI sequence was performed with four different b values(400 s/mm2,600 s/mm2,800 s/mm2,1 000 s/mm2).The diffusion sensitive gradient was applied to X,Y,Z directions at the same time,DWI images were acquired,and ADC and eADC values were obtained by post processing.Signal intensities of DWI images,ADC and eADC values were measured respectively within the lesions.The following data were analyzed:a.DWI images,ADC and eADC images of lymphoma and lymph node metastases with different b values were inspected,and the contrast-to-noise ratio(CNR),ADC and eADC values of different b values within the lesions were calculated to determine an optimal b value,b.The ADC and eADC values were calculated,and the discrepancy between lymphoma and lymph node metastases were compared with each other at different b value,c.The optimal ADC and eADC threshold were determined by means of receiver operating characteristic (ROC)curve to differentiate between lymphoma and lymph node metastases.The size of the lesion were measured before and after the chemotherapy. According to RECIST,the groups of therapeutic effect were grouped.The following data were analyzed:a.DWI images,ADC and eADC images with different b values were inspected before and after therapy in every therapeutic effect group,and the ADC and eADC values of different b values within the lesions were calculated to determine an optimal b value,b.The discrepancies in ADC and eADC values were calculated and compared with each other between lymphomas before and after the chemotherapy with the different b value,c.The discrepancies of the ADC and eADC values between lymphoma 1 course after and 2 course after chemotherapy were compared with the optimal b value,d.The discrepancies in ADC and eADC values alteration extent were compared between different therapeutic effect groups and its relation with prognosis.Results DWI in lymphoma and lymph node metastases revealed:a.The features are different between lymphoma and lymph node metastases on all of the DWI,ADC and eADC images with different b values.The CNR of lymphoma and lymph node metastases are decreased with b value increasing.However,the lesions could still be recognized and the ADC and eADC values within lesions could still be measured with b value reaching 1000 s/mm2.b.There are significant differences between ADC values and eADC values of lymphoma and lymph node metastases with every b value (P=0.000).With b value of 1 000 s/mm2,the ADC value of lymphoma and lymph node metastases were(0.67±0.14)×10-3mm2/s and(1.03±0.14)×10-3mm2/s respectively,eADC value were(0.52±0.07)×10-2and(0.36±0.05)×10-2respectively.c. By means of ROC curve analyzing,the threshold of ADC and eADC within lymphoma and lymph node metastases are contributory to differentiate them. Especially with b value of 1000 s/mm2,the area under ROC curve is the largest.The optimal threshold values of ADC and eADC are 0.834×10-3mm2/s and 0.439×10-2 respectively.DWI examinations in lymphoma before and after therapy revealed:a.After chemotherapy,signal intensity of DWI within the lesions in part-remission group and stable group decreased,ADC value increased and eADC values decreased compared to that of the first exam,defined as response group.Progression group hadn't any change,defined as nortresponse group,b.The signal intensity of DWI and ADC value within lymphoma both in first exam and follow-up exam are decreased with b value increasing,in contrast eADC value increased.However,the lesions could be recognized and the ADC and eADC values within could be measured successfully with b value reaching 1000 s/mm2.c.By analyzing statistically,there is significant discrepencies between the ADC and eADC values of lymphoma obtained before and after the chemotherapy with the different b value(p＜0.05),the ADC and eADC values between lymphoma after 1 course and after 2 course chemotherapy also statistically different respectively(p＜0.05).d.The ADC and eADC values alteration in part remission group is statistically higher than that of stable group respectively (p＜0.05).The one year livability in progressed group and stable group was lower than that of part remission group.Conclusions The optimal b value for detecting and characterizing of lymph node enlargement in systemic lymphoma either before or after therapy,lymph node metastases were 1000 s/mm2.Features on DWI,quantitivity of ADC and eADC values could be helpful in differentiating lymphoma and lymph node metastases to some extent.On DWI,ADC and eADC values could be helpful to some extent in lymphoma response evaluation after chemotherapy.The alteration of ADC yalue after therapy might be in relationship with the prognosis.
|
PDF Full Text Request