- •We propose a simplified algorithm, VIAAVG, which is independent on DIR and requires only AVG CT as input.
- •Accuracy and efficiency are evaluated for 50 patients, which is the largest cohort as far as we know.
- •VIAAVG shows nearly substantial similarity with gold standard, VISPECT, which is higher than other proposed algorithms.
- •VIAAVG takes much less time to compute CTVI than other algorithms proposed before.
- •VIAAVG is more convenient for clinical use, since structures, dose, lung function are all defined on the same AVG CT.
It is still not conclusive which four-dimensional computed tomography (4DCT)-based ventilation imaging algorithm is most accurate and efficient. In this study, we proposed a simplified algorithm (VIAAVG) which only requires the average computed tomography (AVG CT) as input, and quantitatively compared its accuracy and efficiency with three other popular algorithms.
Material and methods
Fifty patients with lung or esophageal cancer who underwent radiotherapy were enrolled. Single photon emission computed tomography (SPECT) ventilation images (VI-SPECT) and 4DCT were acquired 1–3 days before the first treatment session. The end of exhalation and the end of inhalation CT were registered to derive deformable vector field (DVF) using MIMvista. 4DCT-based ventilation images (CTVI) were first calculated respectively by means of four algorithms (VIAJAC, VIAHU, VIAPRO and VIAAVG). The computation times were compared using paired t-test. The corresponding CTVIs (CTVIJAC, CTVIHU, CTVIPRO and CTVIAVG) and VI-SPECT were segmented into three equal sub-volumes (high, medium and low function lung, respectively) after smoothing and normalization. The Dice Similarity Coefficients (DSCs) were calculated for each sub-volume between each CTVI and VI-SPECT. The average DSCs for high, medium and low function lung in different CTVIs for each patient were compared using paired t-test.
The mean DSCs for CTVIJAC, CTVIHU, CTVIPRO and CTVIAVG were 0.3255, 0.4465, 0.5865 and 0.5958, respectively. The average computation times for CTVIJAC, CTVIHU, CTVIPRO and CTVIAVG were 18.3 s, 24.2 s, 144.8 s and 15.0 s.
VIAAVG is available for clinical use because of its high accuracy, improved efficiency and less input requirement compared to the other algorithms.
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Published online: August 12, 2019
Accepted: August 5, 2019
Received in revised form: July 8, 2019
Received: January 18, 2019
© 2019 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.