title: The importance of a correct positioning of the heart using IQ-SPECT system with multifocal collimators in myocardial perfusion imaging: a phantom study.
abstract: BACKGROUND
  We have recently validated a quarter-time protocol in Myocardial Perfusion Imaging named IQ-SPECT, whose basic principle is to implement a multifocal collimator; However, in clinical practice, it may sometimes be difficult to center the heart in the region of highest magnification of the multifocal collimators (the so-called sweet spot). We therefore aimed to evaluate whether a heart mispositioning may affect results in MPI.
  
  
  METHODS
  We simulated a rest study with an anthropomorphic phantom with an in vivo distribution of 400 MBq [(99m)Tc]tetrofosmin, with and without a transmural defect (TD). For each set of images, we performed 5 acquisitions, one with a correct centering and with other 4 degrees of mispositioning. Raw data and reconstructed images were evaluated qualitatively and quantitatively, including no corrections, correction for attenuation, for scatter or for both. We assessed polar plot uniformity, LV wall thickness, and TD and cavity contrast.
  
  
  RESULTS
  Images obtained either with a correct heart centering or with mild misposition showed no differences, both qualitatively and quantitatively. Those obtained with major mispositioning differed in uniformity and TD contrast depending on correction parameters.
  
  
  CONCLUSIONS
  This is the first study investigating how a heart mispositioning can affect diagnostic accuracy with IQ-SPECT system. Mild-to-moderate mispositioning (≤2.5 cm) is unlikely to significantly affect results.
authors.affiliation: Department of Nuclear Medicine, Fondazione Poliambulanza, Brescia, Italy. caobelli.federico@mh-hannover.de; Klinik für Nuklearmedizin, Medizinische Hochschule Hannover, Germany.
authors.forename: Federico
authors.initials: F
authors.lastname: Caobelli
authors.forename: Stefano
authors.initials: S
authors.lastname: Ren Kaiser
authors.forename: James Thomas
authors.initials: JT
authors.lastname: Thackeray
authors.forename: Frank Michael
authors.initials: FM
authors.lastname: Bengel
authors.forename: Matteo
authors.initials: M
authors.lastname: Chieregato
authors.forename: Alberto
authors.initials: A
authors.lastname: Soffientini
authors.forename: Claudio
authors.initials: C
authors.lastname: Pizzocaro
authors.forename: Giordano
authors.initials: G
authors.lastname: Savelli
authors.forename: Ugo Paolo
authors.initials: UP
authors.lastname: Guerra
authors.forename: Marco
authors.initials: M
authors.lastname: Galelli
authors.forename: Orazio
authors.initials: O
authors.lastname: Zoccarato
mesh_terms: D000886:Anthropometry; D006321:Heart / Q000000981:diagnostic imaging; D006352:Heart Ventricles / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009038:Motion; D055414:Myocardial Perfusion Imaging; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D056888:Patient Positioning; D019047:Phantoms, Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012984:Software; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C078700:technetium tc-99m tetrofosmin