title: Attenuation correction reveals gender-related differences in the normal values of transient ischemic dilation index in rest-exercise stress sestamibi myocardial perfusion imaging.
abstract: BACKGROUND
  Transient ischemic dilation (TID) has been established as an important independent marker of severe and extensive coronary artery disease (CAD) in myocardial perfusion imaging (MPI). The accuracy of the TID index is dependent on a well-determined threshold (normal limits) between normal and abnormal values for each study protocol. To date, the effects of neither gender nor attenuation correction (AC) on TID normal limits have been established. Thus, the objectives of this study were to determine if AC processing changes the normal value of the TID index and if there were gender-related differences in the TID index of normal patients who had undergone rest/exercise-stress technetium-99m sestamibi MPI.
  
  
  RESULTS
  Seventy-five patients (33 women, 42 men; mean age, 57.7 +/- 11.7 y and 55.9 +/- 10.0 y, respectively) with less than a 5% likelihood of CAD, who had undergone low-dose rest/high-dose exercise-stress Tc-99m sestamibi MPI, were studied. All studies were acquired using simultaneous emission/transmission scans and were corrected for attenuation, scatter, and resolution effects using the ExSPECT II method. Both the AC and non-AC studies were analyzed using the Emory Cardiac Toolbox (ECTb; Syntermed, Inc, Atlanta, Ga) quantitative software. The TID index was calculated automatically as the ratio of stress mean left ventricular volumes to rest mean left ventricular volumes by ECTb. Patients were grouped by gender and the TID indices from AC and non-AC studies were compared. Linear regressions of the TID index and body mass index were analyzed to exclude differences in body size between male and female patients as a confounding factor in gender-related differences in TID. The TID index upper normal limits were calculated as the mean value plus 2 standard deviations (SDs). AC processing did not change the TID index significantly whether the genders were combined or separated (AC TID = 0.97 +/- 0.14 vs non-AC TID = 0.98 +/- 0.12 for all patients). Female patients showed higher mean TID indices than male patients in both AC (1.01 +/- 0.15 vs 0.95 +/- 0.12) and non-AC studies (1.00 +/- 0.15 vs. 0.97 +/- 0.10), but this difference was statistically significant only in AC studies (p = .03). TID indices remained constant across the range of body mass index studied. The TID index upper normal limit was 1.31 for female and 1.18 for male patients.
  
  
  CONCLUSIONS
  TID normal values for rest/exercise-stress Tc-99m sestamibi MPI are gender-dependent and not affected by AC processing. Thus, diagnosticians should take into account these gender-related differences, as compared with the traditional value generated from mostly male populations, to ensure both men and women have the same overall accuracy of using the TID index in the diagnosis and prognosis of CAD.
authors.affiliation: Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Abel
authors.initials: A
authors.lastname: Rivero
authors.forename: Cesar
authors.initials: C
authors.lastname: Santana
authors.forename: Russell D
authors.initials: RD
authors.lastname: Folks
authors.forename: Fabio
authors.initials: F
authors.lastname: Esteves
authors.forename: Liudmila
authors.initials: L
authors.lastname: Verdes
authors.forename: Shorena
authors.initials: S
authors.lastname: Esiashvili
authors.forename: Gabriel B
authors.initials: GB
authors.lastname: Grossman
authors.forename: Raghuveer K
authors.initials: RK
authors.lastname: Halkar
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Bateman
authors.forename: Ernest V
authors.initials: EV
authors.lastname: Garcia
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D015444:Exercise; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007511:Ischemia / Q000473:pathology; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009206:Myocardium / Q000473:pathology*; D010477:Perfusion / Q000379:methods*; D019275:Radiopharmaceuticals; D012146:Rest; D012737:Sex Factors; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi