title: When is reacquisition necessary due to high extra-cardiac uptake in myocardial perfusion scintigraphy?
abstract: BACKGROUND
  Technetium-labeled agents, which are most often used for assessing myocardial perfusion in myocardial perfusion scintigraphy (MPS), are cleared by the liver and excreted by the biliary system. Spillover from extra-cardiac activity into the myocardium, especially the inferior wall, might conceal defects and lower the diagnostic accuracy of the study. The objective was to determine rules of thumb for when reacquisition is useful due to high extra-cardiac uptake, i.e., when interpretation of the studies was affected by poor image quality.
  
  
  METHODS
  Patients admitted to MPS at any of the three study sites, who also underwent a reacquisition due to high extra-cardiac uptake were included. Image quality was assessed by ten technologists on a scale ranging from 1 to 5. Interpretations regarding the presence/absence of ischemia/infarction, including the certainty of the diagnosis, were made by three physicians.
  
  
  RESULTS
  There was a statistically significant increase in image quality between the first and the repeated acquisition (1,256 cases of increased quality at the repeated study (66%), 134 cases of decreased quality at the repeated study (7%), 510 cases of unchanged quality (27%) P < 0.0001). The number of equivocal studies, interpreted by physicians, decreased when evaluating the repeated studies compared to the first studies for all physicians, both for the interpretations of ischemia and for infarction. Receiver operating characteristic analyses revealed that for both endpoints (ischemia, infarction) and all physicians, the optimal cutoff point for performing a reacquisition was between quality categories 2 and 3.
  
  
  CONCLUSIONS
  This study indicates that repeat acquisition is useful when (1) the intensity of the extra-cardiac uptake is equal to or higher than the cardiac uptake when there is no separation between the extra-cardiac uptake and the inferior cardiac wall and (2) when the intensity of the extra-cardiac uptake is higher than the cardiac uptake when there is a separation between the extra-cardiac uptake and the inferior wall of less than one cardiac wall.
authors.affiliation: Nuclear Medicine Unit, Skåne University Hospital, Lund University, Malmo, Sweden. elin.tragardh@med.lu.se.
authors.forename: Allan
authors.initials: A
authors.lastname: Johansen
authors.forename: Milan
authors.initials: M
authors.lastname: Lomsky
authors.forename: Oke
authors.initials: O
authors.lastname: Gerke
authors.forename: Lars
authors.initials: L
authors.lastname: Edenbrandt
authors.forename: Lena
authors.initials: L
authors.lastname: Johansson
authors.forename: Gunhild
authors.initials: G
authors.lastname: Hansen
authors.forename: Birgitte
authors.initials: B
authors.lastname: Jensen
authors.forename: Maria Sallerup
authors.initials: MS
authors.lastname: Reid
authors.forename: Lise-Lott
authors.initials: LL
authors.lastname: Johansson
authors.forename: Camilla
authors.initials: C
authors.lastname: Olofsson
authors.forename: David
authors.initials: D
authors.lastname: Minarik
authors.forename: Karin
authors.initials: K
authors.lastname: Nyström
authors.forename: Per
authors.initials: P
authors.lastname: Wollmer
authors.forename: Elin
authors.initials: E
authors.lastname: Trägårdh