Impact of slice thickness on clinical utility of automated Alberta Stroke Program Early Computed Tomography Scores

Eur Radiol. 2020 Jun;30(6):3137-3145. doi: 10.1007/s00330-019-06616-8. Epub 2020 Feb 21.

Abstract

Objectives: The clinical utility of electronically derived ASPECTS (e-ASPECTS) to quantify signs of acute ischemic infarction could be demonstrated in multiple studies. Here, we aim to clinically validate the impact of CT slice thickness (ST) on the performance of e-ASPECTS software.

Methods: A consecutive series of n = 258 patients (06/2016 and 01/2019) with middle cerebral artery occlusion and subsequent treatment with mechanical thrombectomy was analyzed. The e-ASPECTS score and acute infarct volumes were calculated from baseline non-contrast CT with a software using 1-mm slice thickness (ST) (defined as ground truth) and axial reconstructions with 2-10-mm ST and correlated with baseline stroke severity (NIHSS) as well as clinical outcome (mRS) using logistic regressions.

Results: In comparison with the ground truth, significant differences were seen in e-ASPECTS scores with ST > 6 mm (p ≤ 0.031) and infarct volumes with ST > 4 mm (p ≤ 0.001). There was a significant correlation of lower e-ASPECTS and higher acute infarct volumes with increasing baseline NIHSS values for all ST (p ≤ 0.001, respectively), with values derived from 1 mm yielding the highest correlation for both parameters (rho, - 0.38 and 0.31, respectively). Similarly, lower e-ASPECTS and higher acute infarct volumes from all ST were significantly associated with poor outcome after 90 days (p ≤ 0.05, respectively) with values derived from 1-mm ST yielding the highest effects for both parameters (OR, 0.69 [95% CI 0.50-0.88] and 1.27 [95% CI 1.10-1.50], respectively).

Conclusions: The e-ASPECTS software generates robust values for e-ASPECTS and acute infarct volumes when using ST ≤ 4 mm with ST = 1 mm yielding the best performance for predicting baseline stroke severity and clinical outcome after 90 days.

Key points: • Clinical utility of automatically derived ASPECTS from computed tomography scans was shown in patients with acute ischemic stroke and treatment with mechanical thrombectomy. • Thin slices (= 1 mm) had the highest clinical utility in comparison with thicker slices (2-10 mm) by having the strongest correlation with baseline stroke severity and independent effects on clinical outcome after 90 days. • Automatically calculated acute infarct volumes possess clinical utility beyond ASPECTS and should be considered in future studies.

Keywords: Brain ischemia; Image interpretation, computer-assisted; Stroke; Thrombectomy; Tomography, X-ray computed.

Publication types

  • Validation Study

MeSH terms

  • Aged
  • Aged, 80 and over
  • Alberta
  • Female
  • Humans
  • Image Processing, Computer-Assisted
  • Infarction, Middle Cerebral Artery / diagnostic imaging*
  • Infarction, Middle Cerebral Artery / therapy
  • Male
  • Mechanical Thrombolysis
  • Middle Aged
  • Software*
  • Stroke / diagnostic imaging*
  • Tomography, X-Ray Computed / methods*
  • Treatment Outcome