title: The acetabular fossa hot spot on 18F-FDG PET/CT: epidemiology, natural history, and proposed etiology.
abstract: OBJECTIVE
  To describe a benign focus of increased activity in the acetabular fossa (the acetabular fossa hot spot, AFHS) on (18) F-FDG PET/CT that can mimic a neoplasm.
  
  
  METHODS
  (18)F-FDG PET/CT images from four patient populations were examined. Group 1 (n = 13) was collected from a search of radiology reports and used to define the AFHS and for hypothesis generation. Group 2 (n = 1,150) was used for prevalence of AFHS. Group 3 (n = 1,213) had PET/CT and MRI pelvis within a week of each other and was used to correlate metabolic and anatomic findings. Group 4 (n = 100) was used to generate the control group. Data were collected on demographics, common comorbidities, underlying cancer diagnosis and status, and hip symptoms.
  
  
  RESULTS
  Prevalence of AFHS was 0.36 % (95 % CI 0.10-0.91 %). None progressed to malignancy or was associated with cancer status. The majority (71 %) were on the left, and 6 % were bilateral. Mean SUVmax of the AFHS was 4.8 (range, 2.7-7.8). Male patients were more likely to have the AFHS (OR = 8.69, 95 % CI 1.88-40.13). There was no difference with respect to other collected data, including hip symptoms. Average minimum duration of AFHS was 346 days (range, 50-1,010 days). Readers did not detect corresponding hip abnormalities on MRIs.
  
  
  CONCLUSIONS
  AFHS is a benign finding that may be caused by subclinical ligamentum teres injury, focal synovitis, or degeneration of acetabular fossa fat. Despite uncertainty regarding its etiology, recognition of AFHS as a benign finding can prevent morbidity associated with unnecessary biopsy or initiation of therapy.
authors.affiliation: Trinity University, San Antonio, TX, USA, skubicki@trinity.edu.
authors.forename: Shelby L
authors.initials: SL
authors.lastname: Kubicki
authors.forename: Michael L
authors.initials: ML
authors.lastname: Richardson
authors.forename: Thomas
authors.initials: T
authors.lastname: Martin
authors.forename: Eric
authors.initials: E
authors.lastname: Rohren
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Behrang
authors.initials: B
authors.lastname: Amini
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000175:diagnosis* / Q000453:epidemiology*; D005189:False Positive Reactions; D019788:Fluorodeoxyglucose F18; D006801:Humans; D015994:Incidence; D007592:Joint Diseases / Q000175:diagnosis* / Q000453:epidemiology*; D008875:Middle Aged; D064847:Multimodal Imaging / Q000706:statistics & numerical data; D049268:Positron-Emission Tomography / Q000706:statistics & numerical data*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18