title: Reexamining normative radiation data for radioguided parathyroid surgery.
abstract: OBJECTIVE
  To reexamine the "Norman rule" (affected parathyroid gland would contain at least 20% radioactivity compared with background), report normative radiation data, offer alternative ratios, and explore the effect of lapsed time on minimally invasive parathyroidectomy (MIRP).
  
  
  METHODS
  Retrospective analysis.
  
  
  METHODS
  Tertiary care academic medical center.
  
  
  METHODS
  A total of 116 consecutive patients who had a diagnosis of primary hyperparathyroidism, positive findings on sestamibi scan, and complete study data from 2000 to 2005 at a single institution.
  
  
  METHODS
  Minimally invasive radio-guided parathyroidectomy (MIRP) for primary hyperparathyroidism.
  
  
  METHODS
  Ten-second gamma radiation counts at key procedural steps. Various ratios of measured radioactivity counts were studied.
  
  
  RESULTS
  A total of 116 patients who underwent MIRP had complete data; 91 patients waited 4 or more hours until surgery (78%), with some waiting 8 or more hours. Every patient had a successful surgery and was observed for 1 year thereafter. The Norman ratio of radiation counts (ex vivo to background) was compared with other radiation ratios using Spearman correlation; the comparisons included skin to background (rho = 0.579), in vivo to background (rho = 0.770), basin to background (rho = 0.525), and in vivo-basin to background (rho = 0.788). Regression analysis indicated that the Norman ratio decreased over time at 11% per hour (P = .31).
  
  
  CONCLUSIONS
  Alternative ratios to the Norman ratio are reported. An ex vivo to background ratio greater than 20% as a rule of successful parathyroid adenoma excision was observed in all but 2 cases in our series.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Andre
authors.initials: A
authors.lastname: Wineland
authors.forename: Eric
authors.initials: E
authors.lastname: Siegel
authors.forename: Brendan C
authors.initials: BC
authors.lastname: Stack
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging* / Q000601:surgery*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D015902:Gamma Cameras; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000000981:diagnostic imaging* / Q000601:surgery*; D007091:Image Processing, Computer-Assisted; D007279:Injections, Subcutaneous; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D010280:Parathyroid Glands / Q000000981:diagnostic imaging*; D010282:Parathyroid Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D016105:Parathyroidectomy; D011446:Prospective Studies; D011877:Radionuclide Imaging; D012016:Reference Values; D025321:Surgery, Computer-Assisted / Q000379:methods*; D017256:Technetium Tc 99m Sestamibi
chemical_list: D017256:Technetium Tc 99m Sestamibi