Rick Avila will give a presentation titled ‘Calibration of computed tomography (CT) volumetric measurements for assessing tumour response to drug therapy in a randomised multicentre oncology study‘ based on collaborative work with D. Yankelevitz, V. Archer, and G. Zahlmann. The presentation will be at 10:30 on Monday, March 11.
Purpose: Quantification of tumour diameter and volumetric measurement variability, due to CT acquisition properties, for patients participating in a clinical NSCLC trial
Methods and Materials: A validated ‘pocket phantom’ was scanned with patients; image acquisition was standardised. Volumetric and diameter measurement performance in X, Y, and Z axes was evaluated. Fully automated software detected and analysed phantoms. A precision-manufactured 15.88mm diameter teflon sphere within each phantom was segmented, using constant thresholding, and measured.
Results: Data were acquired from 77 patients at various time points during the trial using 13 different scanner models across three manufacturers. The mean, standard deviation (SD) and coefficient of variation (CV) were calculated in the X, Y and Z axes of the scanner. Mean, SD and CV for diameter measurements were 15.7mm, 0.13mm and 0.8%, respectively (X axis); 15.6mm, 0.15mm and 1.0% (Y axis); 15.8mm, 0.71mm and 4.5% (Z axis). Mean, SD and CV of volumetric measurements were 1,989mm3, 99mm3 and 5.0%, respectively. Variability of Z-axis diameter measurements was >4 times that of X and Y axes. For 45 patients with >1 scan, volumetric measurement CV was 5.3%. Maximum volumetric change for consecutive CT scans was 44 %. Exclusion of six patients with maximum variation reduced CV to 2.2%. All six of these patients’ images were acquired using 16- and 8-row scanners from a single manufacturer.
Conclusion: Axial diameter measurements had consistently low variability across all scanners and acquisition parameters. Large variation occurred for Z diameter measurements and volumetric measurements.
As part of the ECR Live program, this presentation will be streamed live online via the ESR website.