title: Changes in the appearance of attenuation artefacts due to change in posture in myocardial perfusion imaging.
abstract: OBJECTIVE
  Traditional supine imaging with arms raised for myocardial perfusion imaging (MPI) is uncomfortable for many cardiac patients. Seated imaging with arms resting at shoulder level is an attractive alternative. This study aimed to compare the patient comfort and image appearance of seated MPI with traditional supine MPI.
  
  
  METHODS
  Sixty-seven patients (41 male, 26 female; body mass index (BMI) between 20.4 and 45.4) were imaged seated on the Mediso Nucline Cardiodesk gamma camera and supine on the GE Millennium VG gamma camera using our standard departmental MPI protocol. The images from each were compared and a questionnaire was used to determine patients' views of the relative comfort of the procedures.
  
  
  RESULTS
  Strong patient preference for seated imaging was demonstrated. Perfusion patterns on seated and supine images were strikingly different with the changes seen being greatest and very striking in obese females with seven out of 12 (58%) showing changes of more than two grades. For a subset of 17 normal weight (BMI <25) male patients a significant reduction (P<0.05) in defect size was found in the inferior segment only, signifying a reduction in diaphragmatic attenuation in the seated position.
  
  
  CONCLUSIONS
  Seated imaging offers considerable advantages in terms of patient acceptability. For non-obese men seated imaging also offers advantages in terms of reduced diaphragmatic attenuation artefacts. However, women and also obese men show significant differences in perfusion pattern from traditional supine imaging. A facility for accurate attenuation correction of seated images could provide useful information to elucidate these effects.
authors.affiliation: Department of Nuclear Medicine, Manchester Royal Infirmary, Oxford Road, Manchester, UK. Christine.tonge@cmmc.nhs.uk
authors.forename: Christine M
authors.initials: CM
authors.lastname: Tonge
authors.forename: Ian S
authors.initials: IS
authors.lastname: Armstrong
authors.forename: Parthiban
authors.initials: P
authors.lastname: Arumugam
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: James
authors.forename: Ghada I
authors.initials: GI
authors.lastname: Al-Bahrani
authors.forename: Richard S
authors.initials: RS
authors.lastname: Lawson
authors.forename: Robert A
authors.initials: RA
authors.lastname: Shields
authors.forename: Mary C
authors.initials: MC
authors.lastname: Prescott
mesh_terms: D016477:Artifacts; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D010477:Perfusion / Q000379:methods; D011187:Posture; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity