title: Correlation of left ventricular count rate with patient weight in Tc-99m myocardial perfusion imaging.
abstract: OBJECTIVE
  The aim of this retrospective investigation was to devise a protocol for obtaining consistent myocardial counts for patients attending myocardial perfusion imaging.
  
  
  METHODS
  A total of 229 patients were included in the study sample. For each rest single-photon emission computed tomography data set, a three-dimensional ellipse was manually defined to isolate the left ventricle. The count rate per voxel was measured from a threshold region of interest covering the normally perfused myocardium (70-100% of maximum counts). Data were normalized for net administered activity and plotted against patient weight. The correlation between the variables was used to derive a protocol for adjusting injected activity or scan time to obtain consistent counts from patient to patient.
  
  
  RESULTS
  There was a significant correlation between counts per second per voxel per MBq and patient weight. The best fit was achieved with an inverse model. A correlation equation was derived for patients weighing more than 60 kg (combined R=0.79): [CPS/voxel/MBq=(0.0163/weight(kg)]-3.68×10+A in which A, a sex-dependent constant, was 0 for men and -2.920×10 for women.
  
  
  CONCLUSIONS
  There was a significant inverse correlation between patient weight and CPS per voxel per MBq.
authors.affiliation: Department of Nuclear Medicine, Sheffield Teaching Hospitals, NHS Foundation Trust, Royal Hallamshire Hospital, Sheffield, UK. jonathan.taylor@sth.nhs.uk
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Taylor
authors.forename: Sally-Anne
authors.initials: SA
authors.lastname: Froberg
authors.forename: Philip G
authors.initials: PG
authors.lastname: Hillel
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Harris
authors.forename: Wendy B
authors.initials: WB
authors.lastname: Tindale
mesh_terms: D001835:Body Weight / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D012016:Reference Values; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D016277:Ventricular Function, Left / Q000502:physiology*
chemical_list: D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C078700:technetium tc-99m tetrofosmin; D017256:Technetium Tc 99m Sestamibi