title: IQ SPECT allows a significant reduction in administered dose and acquisition time for myocardial perfusion imaging: evidence from a phantom study.
abstract: We recently demonstrated in a clinical trial the ability of a new protocol, IQ SPECT, to acquire myocardial perfusion imaging (MPI) studies in a quarter of the time (12 s/view) of the standard protocol, with preserved diagnostic accuracy. We now aim to establish the lower limit of radioactivity that can be administered to patients and the minimum acquisition time in SPECT MPI using an IQ SPECT protocol, while preserving diagnostic accuracy.
  
  
  METHODS
  An anthropomorphic cardiac phantom was used to acquire clinical rest scans with a simulated in vivo distribution of (99m)Tc-tetrofosmin at full dose (740 MBq) and at doses equal to 50%, 25%, and 18%. For each dose, 2 sets of images were acquired, with and without a transmural defect (TD). Variable acquisition times were also used for each dose. We analyzed raw data and reconstructed images, including no correction and correction for attenuation (AC), for scatter (SC), or for both (ACSC). Images were evaluated qualitatively and quantitatively in order to assess left ventricle (LV) wall thickness (full width at half maximum of the medial sections), TD, and cavity contrast in the LV wall. Data were compared across different acquisition times within the same dose and across doses with the same acquisition time.
  
  
  RESULTS
  Images were visually scored as very-good quality except those acquired with 4 s/view or less at 100% dose and 6 s/view or less with 50%, 25%, or 18% dose, due to false-positive defects. LV wall thickness was not significantly different among all acquisitions. Cavity contrast remained unchanged within the same dose for all images and tended to be higher in AC and ACSC images. TD contrast remained unchanged within the same dose for all images. In SC and no-correction images, contrast was constant for all doses. AC images had significantly higher TD contrast values, and ACSC images showed a drop in TD contrast for a 50% dose.
  
  
  CONCLUSIONS
  IQ SPECT effectively preserved both image quality and quantitative measurements with reduced acquisition time or administered dose in a phantom study. These findings suggest that approximately one eighth of the time, compared with standard protocols with a full dose, or a lower dose at an acquisition time of 12 s/view can be applied in MPI without the loss of diagnostic accuracy.
authors.affiliation: Department of Nuclear Medicine, Fondazione Poliambulanza, Brescia, Italy; and Klinik für Nuklearmedizin, Medizinische Hochschule Hannover, Hannover, Germany Caobelli.federico@mh-hannover.de.
authors.forename: Federico
authors.initials: F
authors.lastname: Caobelli
authors.affiliation: Department of Nuclear Medicine, Fondazione Poliambulanza, Brescia, Italy; and.
authors.forename: Stefano Ren
authors.initials: SR
authors.lastname: Kaiser
authors.affiliation: Klinik für Nuklearmedizin, Medizinische Hochschule Hannover, Hannover, Germany.
authors.forename: James T
authors.initials: JT
authors.lastname: Thackeray
authors.affiliation: Klinik für Nuklearmedizin, Medizinische Hochschule Hannover, Hannover, Germany.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Bengel
authors.affiliation: Department of Nuclear Medicine, Fondazione Poliambulanza, Brescia, Italy; and.
authors.forename: Matteo
authors.initials: M
authors.lastname: Chieregato
authors.affiliation: Department of Nuclear Medicine, Fondazione Poliambulanza, Brescia, Italy; and.
authors.forename: Alberto
authors.initials: A
authors.lastname: Soffientini
authors.affiliation: Department of Nuclear Medicine, Fondazione Poliambulanza, Brescia, Italy; and.
authors.forename: Claudio
authors.initials: C
authors.lastname: Pizzocaro
authors.affiliation: Department of Nuclear Medicine, Fondazione Poliambulanza, Brescia, Italy; and.
authors.forename: Giordano
authors.initials: G
authors.lastname: Savelli
authors.affiliation: Department of Nuclear Medicine, Fondazione Poliambulanza, Brescia, Italy; and.
authors.forename: Marco
authors.initials: M
authors.lastname: Galelli
authors.affiliation: Department of Nuclear Medicine, Fondazione Poliambulanza, Brescia, Italy; and.
authors.forename: Ugo Paolo
authors.initials: UP
authors.lastname: Guerra
mesh_terms: D000465:Algorithms; D003326:Coronary Circulation / Q000502:physiology; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D019275:Radiopharmaceuticals / Q000008:administration & dosage; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals
keywords: 99mTc-tetrofosmin SPECT/CT; IQ SPECT; coronary artery disease; low counts acquisition; myocardial perfusion imaging