The Impact of Optimal Respiratory Gating and Image Noise on Evaluation of Intratumor Heterogeneity on 18F-FDG PET Imaging of Lung Cancer.
Accurate measurement of intratumor heterogeneity using parameters of texture on PET images is essential for precise characterization of cancer lesions. In this study, we investigated the influence of respiratory motion and varying noise levels on quantification of textural parameters in patients with lung cancer.


METHODS
We used an optimal-respiratory-gating algorithm on the list-mode data of 60 lung cancer patients who underwent18F-FDG PET. The images were reconstructed using a duty cycle of 35% (percentage of the total acquired PET data). In addition, nongated images of varying statistical quality (using 35% and 100% of the PET data) were reconstructed to investigate the effects of image noise. Several global image-derived indices and textural parameters (entropy, high-intensity emphasis, zone percentage, and dissimilarity) that have been associated with patient outcome were calculated. The clinical impact of optimal respiratory gating and image noise on assessment of intratumor heterogeneity was evaluated using Cox regression models, with overall survival as the outcome measure. The threshold for statistical significance was adjusted for multiple comparisons using Bonferroni correction.


RESULTS
In the lower lung lobes, respiratory motion significantly affected quantification of intratumor heterogeneity for all textural parameters (P < 0.007) except entropy (P > 0.007). The mean increase in entropy, dissimilarity, zone percentage, and high-intensity emphasis was 1.3% ± 1.5% (P = 0.02), 11.6% ± 11.8% (P = 0.006), 2.3% ± 2.2% (P = 0.002), and 16.8% ± 17.2% (P = 0.006), respectively. No significant differences were observed for lesions in the upper lung lobes (P > 0.007). Differences in the statistical quality of the PET images affected the textural parameters less than respiratory motion, with no significant difference observed. The median follow-up time was 35 mo (range, 7-39 mo). In multivariate analysis for overall survival, total lesion glycolysis and high-intensity emphasis were the two most relevant image-derived indices and were considered to be independent significant covariates for the model regardless of the image type considered.


CONCLUSIONS
The tested textural parameters are robust in the presence of respiratory motion artifacts and varying levels of image noise.
Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands w.grootjans@lumc.nl.|Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.
Willem
W
Grootjans
Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.|Department of Nuclear Medicine, DACTIM, University Hospital Poitiers, Poitiers, France.
Florent
F
Tixier
Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.
Charlotte S
CS
van der Vos
Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
Dennis
D
Vriens
Department of Nuclear Medicine, DACTIM, University Hospital Poitiers, Poitiers, France.
Catherine C
CC
Le Rest
Department of Radiation Oncology, Radboud University Medical Center, Nijmegen, The Netherlands.
Johan
J
Bussink
Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, United Kingdom.
Wim J G
WJ
Oyen
MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands; and.
Lioe-Fee
LF
de Geus-Oei
INSERM, UMR1101, LaTIM, University of Brest, Brest, France.
Dimitris
D
Visvikis
Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.
Eric P
EP
Visser
D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
18F-FDG PET/CT; lung cancer; radiomics; respiratory gating; total lesion glycolysis