18F-FDG PET for diagnosis and response assessment for aggressive NK cell leukemia

Aggressive natural killer cell leukemia (ANKL) is a rare malignant disorder of mature NK cells characterized by aggressive clinical course and poor outcome. The commonly involved sites are peripheral blood, bone marrow, liver, and spleen, but any organ can show involvement. We report a case of ANKL diagnosed and assessed the clinical response with 18F-FDG PET. Pretreatment and posttreatment FDG PET/CT showed a high correlation with pathologic diagnosis and staging as well as in the follow-up assessment of the clinical response. FDG PET could be a valuable tool enabling comprehensive staging and follow-up of ANKL.

Automatic volume delineation in oncological PET. Evaluation of a dedicated software tool and comparison with manual delineation in clinical data sets

AIM

Evaluation of a dedicated software tool for automatic delineation of 3D regions of interest in oncological PET.

PATIENTS, METHODS

The applied procedure encompasses segmentation of user-specified subvolumes within the tomographic data set into separate 3D ROIs, automatic background determination, and local adaptive thresholding of the background corrected data. Background correction and adaptive thresholding are combined in an iterative algorithm. Nine experienced observers used this algorithm for automatic delineation of a total of 37 ROIs in 14 patients. Additionally, the observers delineated the same ROIs also manually (using a freely chosen threshold for each ROI) and the results of automatic and manual ROI delineation were compared.

RESULTS

For the investigated 37 ROIs the manual delineation shows a strong interobserver variability of (26.8±6.3)% (range: 15% to 45%) while the corresponding value for automatic delineation is (1.1±1.0)% (range: <0.1% to 3.6%). The fractional deviation of the automatic volumes from the observer-averaged manual ones is (3.7±12.7)%.

CONCLUSION

The evaluated software provides results in very good agreement with observer-averaged manual evaluations, facilitates and accelerates the volumetric evaluation, eliminates the problem of interobserver variability and appears to be a useful tool for volumetric evaluation of oncological PET in clinical routine.