Influence of Thin Slice Reconstruction on CT Brain Perfusion Analysis

PLoS One. 2015 Sep 11;10(9):e0137766. doi: 10.1371/journal.pone.0137766. eCollection 2015.

Abstract

Objectives: 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.

Materials and 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.

Trial registration: ClinicalTrials.gov NCT00880113.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Brain / blood supply
  • Brain / diagnostic imaging*
  • Cerebrovascular Circulation
  • Humans
  • Neuroimaging / methods
  • Perfusion Imaging / methods*
  • Stroke / diagnostic imaging
  • Stroke / physiopathology
  • Tomography, X-Ray Computed / methods*

Associated data

  • ClinicalTrials.gov/NCT00880113

Grants and funding

This work was supported by a research grant from the Dutch Technology Foundation STW (AIRSPACE, 11632). The project AIRSPACE received in-kind funding from Philips Healthcare and the LifeTec Group. The CTP data was collected under the Dutch acute Stroke Trial (DUST), details of which can be found at https://clinicaltrials.gov/ct2/show/NCT00880113. The DUST study was funded by the University Medical Center Utrecht, the Netherlands Heart Foundation (2008T034), the NutsOhra Foundation (0903-012), and in-kind by Philips Healthcare. Jan Willem Dankbaar was funded by the Netherlands Heart Foundation (2012T61). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.