title: Myocardial perfusion imaging with a solid-state camera: simulation of a very low dose imaging protocol.
abstract: High-sensitivity dedicated cardiac camera systems provide an opportunity to lower the injected doses for SPECT myocardial perfusion imaging (MPI), but the exact limits for lowering doses have not been determined. List-mode data acquisition allows for reconstruction of various fractions of acquired counts, enabling a simulation of gradually lower administered dose. We aimed to determine the feasibility of very low dose MPI by exploring the minimal count level in the myocardium required for accurate MPI.
  
  
  METHODS
  Seventy-nine patients were studied (mean body mass index, 30.0 ± 6.6; range, 20.2-54.0 kg/m(2)) who underwent 1-d standard-dose (99m)Tc-sestamibi exercise or adenosine rest-stress MPI for clinical indications using a cadmium-zinc-telluride dedicated cardiac camera. The imaging time was 14 min, with averaged 803 ± 200 MBq (21.7 ± 5.4 mCi) of (99m)Tc injected at stress. To simulate clinical scans with a lower dose at that imaging time we reframed the list-mode raw data. Accordingly, 6 stress-equivalent datasets were reconstructed containing various count fractions of the original scan. Automated quantitative perfusion and gated SPECT software was used to quantify total perfusion deficit (TPD) and ejection fraction for all 553 datasets (7 × 79). The minimal acceptable left ventricular region counts were determined on the basis of a previous report with repeatability of same-day, same-injection Anger camera studies. Pearson correlation coefficients and the SD of differences in TPD for all scans were calculated.
  
  
  RESULTS
  The correlations of quantitative perfusion and function analysis were excellent for both global and regional analysis between original scans and all simulated low-count scans (all r ≥ 0.95, P < 0.0001). The minimal acceptable counts were determined to be 1.0 million for the left ventricular region. At this count level, the SD of differences was 1.7% for TPD and 4.2% for ejection fraction. This count level would correspond to a 92.5-MBq (2.5-mCi) injected dose for the 14-min acquisition or 125.8-MBq (3.4-mCi) injected dose for the 10-min acquisition.
  
  
  CONCLUSIONS
  1.0 million counts appear to be sufficient to produce myocardial images that agree well with 8.0-million-count images on quantitative perfusion and function parameters. With a dedicated cardiac camera, these images can be obtained over 10 min with an effective radiation dose of less than 1 mSv without significant sacrifice of accuracy.
authors: Department of Imaging and Medicine, and Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.
authors: Ryo
authors: R
authors: Nakazato
authors: Daniel S
authors: DS
authors: Berman
authors: Sean W
authors: SW
authors: Hayes
authors: Mathews
authors: M
authors: Fish
authors: Richard
authors: R
authors: Padgett
authors: Yuan
authors: Y
authors: Xu
authors: Mark
authors: M
authors: Lemley
authors: Rafael
authors: R
authors: Baavour
authors: Nathaniel
authors: N
authors: Roth
authors: Piotr J
authors: PJ
authors: Slomka
mesh_terms: D000368:Aged; D002985:Clinical Protocols; D003198:Computer Simulation; D005260:Female; D015902:Gamma Cameras; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D011829:Radiation Dosage; D019275:Radiopharmaceuticals; D012984:Software; D013318:Stroke Volume; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi