title: A Bayesian iterative transmission gradient reconstruction algorithm for cardiac SPECT attenuation correction.
abstract: BACKGROUND
  High-quality attenuation maps are critical for attenuation correction of myocardial perfusion single photon emission computed tomography studies. The filtered backprojection (FBP) approach can introduce errors, especially with low-count transmission data. We present a new method for attenuation map reconstruction and examine its performance in phantom and patient data.
  
  
  RESULTS
  The Bayesian iterative transmission gradient algorithm incorporates a spatially varying gamma prior function that preferentially weights estimated attenuation coefficients toward the soft-tissue value while allowing data-driven solutions for lung and bone regions. The performance with attenuation-corrected technetium 99m sestamibi clinical images was evaluated in phantom studies and in 50 low-likelihood patients grouped by body mass index (BMI). The algorithm converged in 15 iterations in the phantom studies. For the clinical studies, soft-tissue estimates had significantly greater uniformity of mediastinal coefficients (mean SD, 0.005 cm(-1) vs 0.011 cm(-1); P < .0001). The accuracy and uniformity of the Bayesian iterative transmission gradient algorithm were independent of BMI, whereas both declined at higher BMI values with FBP. Attenuation-corrected perfusion images showed improvement in myocardial wall variability (4.8% to 4.1%, P = .02) for all BMI groups with the new method compared with FBP.
  
  
  CONCLUSIONS
  This new method for attenuation map reconstruction provides rapidly converging and accurate attenuation maps over a wide spectrum of patient BMI values and significantly improves attenuation-corrected perfusion images.
authors.affiliation: Cardiovascular Imaging Technologies, LLC, Kansas City, MO 64111, USA. jcase@cvit-online.com
authors.forename: James A
authors.initials: JA
authors.lastname: Case
authors.forename: Bai Ling
authors.initials: BL
authors.lastname: Hsu
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Bateman
authors.forename: S James
authors.initials: SJ
authors.lastname: Cullom
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001499:Bayes Theorem; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi