Article Figures & Data
Figures
- Fig 1.
Illustration of differentiation between partial volume effect and hemorrhage in the vicinity of the skull. A, Calculation of the density gradient of an NCCT image with high hypodensities near the skull. High gradients are expected to be caused by partial volume effects in contrast to hemorrhages, which result in low gradients as seen in B and C. The pixels corresponding to low gradients (blue) are excluded from further segmentation. The white arrows mark the areas with high gradients present in the CSF image.
- Fig 2.
Illustration of the correction for patient-specific density differences. A, Each section of a specific tissue type (here CSF) is divided into 64 tiles, and the SDs of the density were calculated. B, Green tiles represent those with a low SD of the density and are expected to be free of a substantial amount of extravasated blood and therefore mainly consist of healthy brain tissue, whereas tiles with a high SD (red tiles) are more likely to contain hemorrhage. The densities in the green tiles were included in the calculation of the mean density of that tissue type. Comparison with the mean density of that tissue type in the reference image resulted in a density offset, which was corrected.
- Fig 3.
The accuracy of the volume measurement of the automatic method compared with that in observer 1. A, Accuracy depicted as a scatterplot. B, Accuracy shown by the Bland-Altman plot. Interobserver variability of the manual hemorrhage volume measurement depicted as C, scatterplot, and D, Bland-Altman analysis.
- Fig 4.
Correlation of the Hijdra score and Fisher score with hemorrhage volume after SAH assessed with scatterplots. A, The Fisher score with automatic volume measurement (blue) and manual volume measurement (red). B, The Hijdra score with automatic volume measurement (blue) and manual volume measurement (red).
- Fig 5.
Example of the results of the automatic segmentation of extravasated blood after SAH and manual measurement. A, NCCT image, shown in red, with results of the automatic method of a relatively small hemorrhage. B, The same NCCT image and hemorrhage as delineated by observer 1 (blue). C, NCCT image with beam-hardening in an extreme degree. The automatic method, in red, shows deviations of the hemorrhage volume as delineated by observer 1 (D) in blue.
Tables
Characteristics Test Set (No.) (%) Training Set (No.) (%) Sex Male 12 (40) 5 (75) Female 18 (60) 15 (25) Age (yr) 45 or younger 7 (23) 5 (25) 46–60 16 (53) 11 (55) Older than 60 7 (23) 4 (20) IVH Yes 16 (53) 4 (20) No 14 (47) 16 (80) ICH Yes 19 (63) 12 (60) No 11 (37) 8 (40) MCA location Left 14 (47) 18 (10) Right 16 (53) 2 (90) WFNS at admission Grade I 11 (37) 9 (45) Grade II 2 (7) 2 (10) Grade III 2 (7) 4 (20) Grade IV 8 (27) 3 (15) Grade V 7 (23) 2 (10) History of hypertension Yes 3 (10) 7 (35) No 22 (73) 13 (65) Aneurysm size ≤5 mm 9 (30) 6 (30) 6–10 mm 14 (47) 12 (60) 11–15 mm 3 (10) 2 (10) >15 mm 3 (10) – Signs of DCI No 21 (70) 19 (95) Yes 9 (30) 1 (5) Paresis 1 (3) 1 (5) Decreased consciousness 4 (13) – Hemiparesis and aphasia 3 (10) – Vasospasm 1 (3) – Note:—IVH indicates intraventricular hemorrhage; ICH, intracerebral hemorrhage; DCI, delayed cerebral ischemia; WFNS, World Federation of Neurosurgical Societies.
- Table 2:
Interobserver variability of manual SAH volume measurement and comparison of the manual and automatic methods
ICC Volumea (95% CI) Bland-Altman Volume Limits of Agreement (mL) ICC Densitya (95% CI) Bland-Altman Density Limits of Agreement (HU) Dice Coefficient (Mean and Range) No.b Automatic interobserver 0.98 (0.96–0.99) −12.90–12.13 0.80 (0.62–0.90) −7.58–9.18 0.55 (0.00–0.83) 30 Manual interobserver 0.97 (0.77–0.99) −18.68–6.24 0.98 (0.89–0.99)c −1.52–3.44c 0.64 (0.00–0.86) 30
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