title: Low dose CT perfusion in acute ischemic stroke.
abstract: BACKGROUND
  The purpose of this investigation is to determine if CT perfusion (CTP) measurements at low doses (LD = 20 or 50 mAs) are similar to those obtained at regular doses (RD = 100 mAs), with and without the addition of adaptive statistical iterative reconstruction (ASIR).
  
  
  METHODS
  A single-center, prospective study was performed in patients with acute ischemic stroke (n = 37; 54% male; age = 74 ± 15 years). Two CTP scans were performed on each subject: one at 100 mAs (RD) and one at either 50 or 20 mAs (LD). CTP parameters were compared between the RD and LD scans in regions of ischemia, infarction, and normal tissue. Differences were determined using a within-subjects ANOVA (p < 0.05) followed by a paired t test post hoc analysis (p < 0.01).
  
  
  RESULTS
  At 50 mAs, there was no significant difference between cerebral blood flow (CBF), cerebral blood volume (CBV), or time to maximum enhancement (Tmax) values for the RD and LD scans in the ischemic, infarcted, or normal contralateral regions (p < 0.05). At 20 mAs, there were significant differences between the RD and LD scans for all parameters in the ischemic and normal tissue regions (p > 0.05).
  
  
  CONCLUSIONS
  CTP-derived CBF and CBV are not different at 50 mAs compared to 100 mAs, even without the addition of ASIR. Current CTP protocols can be modified to reduce the effective dose by 50 % without altering CTP measurements.
authors.affiliation: Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Room AG 31, Toronto, ON, M4N 3M5, Canada, amanda.murphy@live.ca.
authors.forename: Amanda
authors.initials: A
authors.lastname: Murphy
authors.forename: Aaron
authors.initials: A
authors.lastname: So
authors.forename: Ting-Yim
authors.initials: TY
authors.lastname: Lee
authors.forename: Sean
authors.initials: S
authors.lastname: Symons
authors.forename: Raphael
authors.initials: R
authors.lastname: Jakubovic
authors.forename: Liying
authors.initials: L
authors.lastname: Zhang
authors.forename: Richard I
authors.initials: RI
authors.lastname: Aviv
mesh_terms: D000368:Aged; D002545:Brain Ischemia / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D005260:Female; D059907:Functional Neuroimaging; D006801:Humans; D008297:Male; D011446:Prospective Studies; D011829:Radiation Dosage; D020521:Stroke / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed