title: Two-phase (low-dose) computed tomography is as effective as 4D-CT for identifying enlarged parathyroid glands.
abstract: BACKGROUND
  Four-dimensional computed tomography (4D-CT) is often used for patients with primary hyperparathyroidism and non-definitive localization after Sestamibi scan (MIBI) and ultrasound (US), but may expose patients to unnecessary radiation, typically between 10 and 26 millisieverts (mSv). We hypothesize that a simpler two-phase CT protocol would have a similar sensitivity, specificity and accuracy to those published for 4D-CT, while exposing the patient to less radiation.
  
  
  METHODS
  We reviewed 54 patients with primary hyperparathyroidism and non-definitive localization studies who had a two-phase CT between 2009 and 2012 at our tertiary referral center.
  
  
  RESULTS
  The mean radiation dose of two-phase CT over the course of the study was 5.2 mSv (range 3.5 mSv-9.1 mSv). Two-phase CT had a 77% (CI = 65%-86%) sensitivity and an 87% (CI = 73%-95%) specificity to lateralize enlarged parathyroid glands to the correct side of the neck and a 58% (CI = 45%-68%) sensitivity and 91% (CI = 83%-94%) specificity to localize parathyroid tumors to the correct quadrant of the neck. The overall accuracy of two-phase CT to lateralize enlarged parathyroids was 81% (CI = 73%, 88%) and the accuracy to localize enlarged parathyroids was 79% (CI = 73%, 84%).
  
  
  CONCLUSIONS
  As a second line investigation two-phase CT has a similar sensitivity, specificity and accuracy to those published for 4D-CT in patients with non-localized, enlarged parathyroids with less radiation exposure. Two-phase CT can help localize enlarged parathyroid glands not definitively identified using MIBI and US.
  
  
  CONCLUSIONS
  Two-phase CT allows clinicians to accurately identify enlarged parathyroid glands while exposing the patient to less radiation than 4D-CT.
authors.affiliation: University of California, Davis, Sacramento, CA, USA. Electronic address: Michael.Campbell@ucdmc.ucdavis.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Campbell
authors.affiliation: Virginia Mason Medical Center, Seattle, WA, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Sicuro
authors.affiliation: Virginia Mason Medical Center, Seattle, WA, USA.
authors.forename: Adnan
authors.initials: A
authors.lastname: Alseidi
authors.affiliation: Virginia Mason Medical Center, Seattle, WA, USA.
authors.forename: C Craig
authors.initials: CC
authors.lastname: Blackmore
authors.affiliation: Virginia Mason Medical Center, Seattle, WA, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Ryan
mesh_terms: D000236:Adenoma / Q000175:diagnosis / Q000473:pathology; D000328:Adult; D000368:Aged; D005260:Female; D056973:Four-Dimensional Computed Tomography; D019220:High-Energy Shock Waves; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000601:surgery; D008875:Middle Aged; D009929:Organ Size; D010280:Parathyroid Glands / Q000000981:diagnostic imaging* / Q000473:pathology; D010282:Parathyroid Neoplasms / Q000175:diagnosis / Q000473:pathology; D016105:Parathyroidectomy / Q000379:methods; D011300:Preoperative Care; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult
keywords: 4D-CT; Hyperparathyroidism; Two-phase CT