Appropriate margin thresholds for isocontour metabolic volumetry of fluorine-18 fluorodeoxyglucose PET in sarcoma: a hybrid PET/MRI study.
OBJECTIVE
Metabolic volumetry and heterogeneity indexes are increasingly being used in fluorine-18 fluorodeoxyglucose (F-FDG) PET, mostly using isocontour methods. However, there is no standard method to determine optimal margin thresholds for isocontour volume of interest (VOIiso). Here, VOIiso with various margin thresholds were compared with exact anatomical tumor volumes in sarcoma using a hybrid PET/MRI scanner.


METHODS
F-FDG PET/MRI images were retrospectively analyzed for 36 lesions of soft tissue or bone sarcoma. VOIiso of tumors was drawn with varying margin thresholds; standardized uptake value (SUV) 1.0-4.0 with an increment of 0.5 and 30-70% of maximal SUV (SUVmax) with an increment of 10%. Exact anatomical tumor volumes (VOIMRI) were drawn manually on the basis of MRI. In each VOI, metabolic tumor volume, SUVmean, total lesion glycolysis, and SD were measured and compared between VOIiso and VOIMRI.


RESULTS
Significant correlations were observed between the indexes from VOIiso and VOIMRI. For metabolic tumor volume, no significant difference existed between VOIiso and VOIMRI with margin thresholds of 30 and 40% of SUVmax, and SUV 1.5. For SUVmean, no significant difference existed with 30% of SUVmax, and SUV 1.5. For total lesion glycolysis, no significant difference existed with 40% of SUVmax, SUV 1.5, and 2.0. For SD, no significant difference existed with 30% of SUVmax, SUV 1.5, and 2.0.


CONCLUSIONS
Margin thresholds of 30 or 40% of SUVmax and SUV 1.5 or 2.0 may be used for the VOIiso method in F-FDG PET images of sarcoma. VOIiso with these margin thresholds are expected to produce reliable metabolic, volumetric, and heterogeneity indexes on F-FDG PET images.
Departments of aNuclear Medicine bRadiology, Seoul National University Hospital, Seoul, Korea.
Hyunjong
H
Lee
Jin Chul
JC
Paeng
Sung Hwan
SH
Hong
Hye Jin
HJ
Yoo
Gi Jeong
GJ
Cheon
Dong Soo
DS
Lee
June-Key
JK
Chung
Keon Wook
KW
Kang
D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D012509:Sarcoma / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000473:pathology; D047368:Tumor Burden
D019788:Fluorodeoxyglucose F18