title: Influence of Thin Slice Reconstruction on CT Brain Perfusion Analysis.
abstract: OBJECTIVE
  Although CT scanners generally allow dynamic acquisition of thin slices (1 mm), thick slice (≥5 mm) reconstruction is commonly used for stroke imaging to reduce data, processing time, and noise level. Thin slice CT perfusion (CTP) reconstruction may suffer less from partial volume effects, and thus yield more accurate quantitative results with increased resolution. Before thin slice protocols are to be introduced clinically, it needs to be ensured that this does not affect overall CTP constancy. We studied the influence of thin slice reconstruction on average perfusion values by comparing it with standard thick slice reconstruction.
  
  
  METHODS
  From 50 patient studies, absolute and relative hemisphere averaged estimates of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and permeability-surface area product (PS) were analyzed using 0.8, 2.4, 4.8, and 9.6 mm slice reconstructions. Specifically, the influence of Gaussian and bilateral filtering, the arterial input function (AIF), and motion correction on the perfusion values was investigated.
  
  
  RESULTS
  Bilateral filtering gave noise levels comparable to isotropic Gaussian filtering, with less partial volume effects. Absolute CBF, CBV and PS were 22%, 14% and 46% lower with 0.8 mm than with 4.8 mm slices. If the AIF and motion correction were based on thin slices prior to reconstruction of thicker slices, these differences reduced to 3%, 4% and 3%. The effect of slice thickness on relative values was very small.
  
  
  CONCLUSIONS
  This study shows that thin slice reconstruction for CTP with unaltered acquisition protocol gives relative perfusion values without clinically relevant bias. It does however affect absolute perfusion values, of which CBF and CBV are most sensitive. Partial volume effects in large arteries and veins lead to overestimation of these values. The effects of reconstruction slice thickness should be taken into account when absolute perfusion values are used for clinical decision making.
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands; Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Edwin
authors.initials: E
authors.lastname: Bennink
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands; Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Jaap
authors.initials: J
authors.lastname: Oosterbroek
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Horsch
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: Dankbaar
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Birgitta K
authors.initials: BK
authors.lastname: Velthuis
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Max A
authors.initials: MA
authors.lastname: Viergever
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands; Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Hugo W A M
authors.initials: HW
authors.lastname: de Jong
mesh_terms: D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation; D006801:Humans; D059906:Neuroimaging / Q000379:methods; D055420:Perfusion Imaging / Q000379:methods*; D020521:Stroke / Q000000981:diagnostic imaging / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000379:methods*