title: Effect of increasing the sampling interval to 2 seconds on the radiation dose and accuracy of CT perfusion of the head and neck.
abstract: OBJECTIVE
  To evaluate the effect of increasing the sampling interval from 1 second (1 image per second) to 2 seconds (1 image every 2 seconds) on computed tomographic (CT) perfusion (CTP) of head and neck tumors.
  
  
  METHODS
  Twenty patients underwent CTP studies of head and neck tumors with images acquired in cine mode for 50 seconds using sampling interval of 1 second. Using deconvolution-based software, analysis of CTP was done with sampling interval of 1 second and then 2 seconds. Perfusion maps representing blood flow, blood volume, mean transit time, and permeability surface area product (PS) were obtained. Quantitative tumor CTP values were compared between the 2 sampling intervals. Two blinded radiologists compared the subjective quality of CTP maps using a 3-point scale between the 2 sampling intervals. Radiation dose parameters were recorded for the 2 sampling interval rates.
  
  
  RESULTS
  No significant differences were observed between the means of the 4 perfusion parameters generated using both sampling intervals; all P >0.05. The 95% limits of agreement between the 2 sampling intervals were -65.9 to 48.1) mL/min per 100 g for blood flow, -3.6 to 3.1 mL/100 g for blood volume, -2.9 to 3.8 seconds for mean transit time, and -10.0 to 12.5 mL/min per 100 g for PS. There was no significant difference between the subjective quality scores of CTP maps obtained using the 2 sampling intervals; all P > 0.05. Radiation dose was halved when sampling interval increased from 1 to 2 seconds.
  
  
  CONCLUSIONS
  Increasing the sampling interval rate to 1 image every 2 seconds does not compromise the image quality and has no significant effect on quantitative perfusion parameters of head and neck tumors. The radiation dose is halved.
authors.affiliation: From the Department of Diagnostic and Interventional Radiology, Mansoura University Hospital, Mansoura, Egypt.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Tawfik
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Razek
authors.forename: Galal
authors.initials: G
authors.lastname: Elhawary
authors.forename: Nihal M
authors.initials: NM
authors.lastname: Batouty
mesh_terms: D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D055420:Perfusion Imaging / Q000379:methods*; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D018401:Sample Size; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*