title: Evaluation of the sensitivity and specificity of (11)C-metomidate positron emission tomography (PET)-CT for lateralizing aldosterone secretion by Conn's adenomas.
abstract: BACKGROUND
  Identification of unilateral aldosterone-producing (Conn's) adenomas has traditionally required lateralization by the invasive and technically difficult procedure of adrenal vein sampling (AVS). (11)C-metomidate, a potent inhibitor of adrenal steroidogenic enzymes, is a positron emission tomography (PET) radiotracer that is selectively accumulated by Conn's adenomas.
  
  
  OBJECTIVE
  The objective of the study was to compare the sensitivity and specificity of (11)C-metomidate PET-computed tomography (CT) against the current gold standard of AVS.
  
  
  METHODS
  The design of the study was within-patient comparison of diagnostic techniques.
  
  
  METHODS
  The study was conducted at a single center-university teaching hospital.
  
  
  METHODS
  Thirty-nine patients with primary hyperaldosteronism (PHA) and five with nonfunctioning adenomas (incidentalomas) participated in the study.
  
  
  METHODS
  The first six PHA patients were studied on three occasions to determine whether steroid pretreatment reduced (11)C-metomidate uptake by normal adrenal. Subsequent patients received dexamethasone for 3 d prior to injection of (11)C-metomidate 150-500 MBq.
  
  
  METHODS
  Maximum standardized uptake values (SUV(max)) over regions of interest determined from 35-45 min after injection were measured.
  
  
  RESULTS
  Dexamethasone increased tumor to normal adrenal SUV(max) ratio by 25.6 ± 5.0% (P < 0.01). PET-CT visualized subcentimeter adenomas and distinguished hot from cold adenomas within a gland. In 25 patients with PHA and AVS lateralization to the side of an adenoma, SUV(max) over tumor (mean ± sem) of 21.7 ± 1.6 was greater than over normal adrenal, 13.8 ± 0.6 (P = 0.00003); this difference was absent in 10 patients without lateralization on AVS (P = 0.28) and in four of five incidentalomas. On receiver-operator characteristics analysis, an SUV(max) ratio of 1.25:1 provided a specificity of 87% [95% confidence interval (69, 104)] and sensitivity of 76% (59, 93); in tumors with SUV(max) greater than 17, the specificity rose to 100%.
  
  
  CONCLUSIONS
  (11)C-metomidate PET-CT is a sensitive and specific noninvasive alternative to AVS in the management of PHA.
authors: Clinical Pharmacology Unit, Department of Medicine, University of Cambridge, Cambridge CB2 2QQ, UK.
authors: Timothy J
authors: TJ
authors: Burton
authors: Isla S
authors: IS
authors: Mackenzie
authors: Kottekkattu
authors: K
authors: Balan
authors: Brendan
authors: B
authors: Koo
authors: Nick
authors: N
authors: Bird
authors: Dmitri V
authors: DV
authors: Soloviev
authors: Elena A B
authors: EA
authors: Azizan
authors: Franklin
authors: F
authors: Aigbirhio
authors: Mark
authors: M
authors: Gurnell
authors: Morris J
authors: MJ
authors: Brown
mesh_terms: D000306:Adrenal Cortex Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D018246:Adrenocortical Adenoma / Q000000981:diagnostic imaging* / Q000378:metabolism; D000328:Adult; D000450:Aldosterone / Q000378:metabolism*; D002250:Carbon Radioisotopes; D005045:Etomidate / Q000031:analogs & derivatives*; D006801:Humans; D033162:Incidental Findings; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D012372:ROC Curve; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D002250:Carbon Radioisotopes; D000450:Aldosterone; C084586:metomidate; D005045:Etomidate