PF315 CLINICAL VALUE OF DIFFUSION‐WEIGHTED WHOLE‐BODY IMAGING WITH BACKGROUND BODY SIGNAL SUPPRESSION IN NEWLY DIAGNOSED LYMPHOMA PATIENTS

Background: 18 F‐fluoro‐2‐deoxyglucose positron emission tomography/computed tomography ( 18 F‐FDG PET/CT) is the widely used functional imaging method in lymphoma. Although 18 F‐FDG PET/CT shows a higher sensitivity for detecting lesions, it has the disadvantage of associated substantial dose of ionizing radiation and may cause radiation‐induced secondary malignancies. Diffusion‐weighted whole‐body imaging with background body signal suppression (DWIBS), a noninvasively functional magnetic resonance imaging (MRI) technique that can probe random microscopic motion of water molecules in the body. Aims: In this study, we evaluate clinical value of DWIBS by comparing the accuracy of DWIBS and 18 F‐FDG PET/CT in the staging of newly diagnosed lymphoma patients. Further to investigate the correlation between the minimum apparent diffusion coefficient (ADC min ) and maximum standard uptake value (SUV max ), Ki‐67, international prognostic index (IPI), clinical stages, serum lactate dehydrogenase (LDH) and β2‐microglobulin (β2‐MG). Methods: Fifty‐four newly diagnosed lymphoma patients prospectively underwent both DWIBS and 18 F‐FDG PET/CT. Staging was performed with WB‐DWI and 18 F‐FDG PET/CT respectively according to the Ann Arbor stage system. For each patient, the ADC min of the lesion was measured on the ADC map and SUV max was measured in the lesion with high FDG uptake. The mean value of ADC min for all measurable lesions per patient was indicated by ADC mean . Pathological specimens were immunohistochemically stained to obtain Ki‐67 positive rates. Serum LDH and β2‐MG level results were collected. Results: A total of 273 lesions, 222 nodal lesions and 51 extra‐nodal lesions, were detected by DWIBS. 18F‐FDG PET/CT showed a total of 271 lesions involved, 207 nodal lesions and 64 extra‐nodal lesions. The agreement of detecting nodal lesions between the two imaging methods was excellent (к = 0.828, p  < 0.001). The agreement of detecting extra‐nodal lesions between the two imaging methods was good (к = 0.674, p  < 0.001). The agreement of detecting overall lesions (nodal lesions and extra‐nodal lesions) between the two imaging methods was good (к = 0.755, p  < 0.001). The two methods were concordant in the staging in 45 (83.3%) patients (к = 0.755, p  < 0.001). DWIBS staging and clinical staging were concordant in 45 (83.3%) patients (к = 0.757, p  < 0.001). 18F‐FDG PET/CT staging and clinical staging were concordant in 47 (87.0%) patients(к = 0.809, p  < 0.001). One hundred and ninety lesions simultaneously obtained ADC min and SUV max . Based on 190 lesions, ADC min and SUV max were inversely correlated (r = −0.222, p = 0.002). There was no statistically significant difference in ADC mean between different stages and different IPI scores. There were no correlations between ADC mean and IPI, clinical staging, LDH, β2‐MG. Among 42 patients with biopsy, a significant inversely correlation was observed between ADC min and Ki‐67 of the biopsy lesions (r = −0.401 p = 0.009). Summary/Conclusion: Our results showed good agreement between DWIBS and PET/CT in staging of newly diagnosed lymphoma patients, and an inversely correlation between ADC min and SUV max , ADC min and the proliferation index Ki‐67. Although the concordance rate between DWIBS staging and clinical staging was slightly lower than that of between PET/CT staging and clinical staging, DWIBS has the advantages of safe and efficient, affordable and non‐ionization radiation. Therefore, DWIBS in the clinical application of lymphoma is still promising.