PET imaging of adrenal cortical tumors with the 11beta-hydroxylase tracer 11C-metomidate.
The purpose of the study was to evaluate PET with the tracer 11C-metomidate as a method to identify adrenal cortical lesions.


METHODS
PET with 11C-metomidate was performed in 15 patients with unilateral adrenal mass confirmed by CT. All patients subsequently underwent surgery, except 2 who underwent biopsy only. The lesions were histopathologically examined and diagnosed as adrenal cortical adenoma (n = 6; 3 nonfunctioning), adrenocortical carcinoma (n = 2), and nodular hyperplasia (n = 1). The remaining were noncortical lesions, including 1 pheochromocytoma, 1 myelolipoma, 2 adrenal cysts, and 2 metastases.


RESULTS
All cortical lesions were easily identified because of exceedingly high uptake of 11C-metomidate, whereas the noncortical lesions showed very low uptake. High uptake was also seen in normal adrenal glands and in the stomach. The uptake was intermediate in the liver and low in other abdominal organs. Images obtained immediately after tracer injection displayed high uptake in the renal cortex and spleen. The tracer uptake in the cortical lesions increased throughout the examination. For quantitative evaluation of tracer binding in individual lesions, a model with the splenic radioactivity concentration assigned to represent nonspecific uptake was applied. Values derived with this method, however, did show the same specificity as the simpler standardized uptake value concept, with similar difference observed for cortical versus noncortical lesions.


CONCLUSIONS
PET with 11C-metomidate has the potential to be an attractive method for the characterization of adrenal masses with the ability to discriminate lesions of adrenal cortical origin from noncortical lesions.
Bergström
M
M
Department of Surgery, University Hospital, Uppsala, Sweden.
Juhlin
C
C
Bonasera
T A
TA
Sundin
A
A
Rastad
J
J
Akerström
G
G
Långström
B
B
D000306:Adrenal Cortex Neoplasms / Q000000981:diagnostic imaging*; D018246:Adrenocortical Adenoma / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D002250:Carbon Radioisotopes; D005045:Etomidate / Q000031:analogs & derivatives*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011849:Radioactive Tracers; D012680:Sensitivity and Specificity; D013252:Steroid 11-beta-Hydroxylase / Q000032:analysis; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed
D002250:Carbon Radioisotopes; D011849:Radioactive Tracers; D013252:Steroid 11-beta-Hydroxylase; C084586:metomidate; D005045:Etomidate