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Interchangeability of radiomic features between [18F]-FDG PET/CT and [18F]-FDG PET/MR


Vuong, Diem; Tanadini-Lang, Stephanie; Huellner, Martin W; Veit-Haibach, Patrick; Unkelbach, Jan; Andratschke, Nicolaus; Kraft, Johannes; Guckenberger, Matthias; Bogowicz, Marta (2019). Interchangeability of radiomic features between [18F]-FDG PET/CT and [18F]-FDG PET/MR. Medical Physics, 46(4):1677-1685.

Abstract

PURPOSE
Radiomics is a promising tool for identification of new prognostic biomarkers. However, image reconstruction settings and test-retest variability may influence the absolute values of radiomic features. Unstable radiomic features cannot be used as reliable biomarkers. PET/MR is becoming increasingly available and often replaces PET/CT for different indications. The aim of this study was to quantify to what extend [18F]-FDG PET/CT radiomics models can be transferred to [18F]-FDG PET/MR and thereby to investigate the feasibility of combined PET/CT-PET/MR models. For this purpose, we compared PET radiomic features calculated on PET/MR and PET/CT and on a 4D gated PET/MR dataset to select radiomic features that are robust to attenuation correction differences and test-retest variability, respectively.
METHODS
Two cohorts of patients with lung lesions were studied. In the first cohort (n=10), inhale and exhale phases of a 4D [18F]-FDG PET/MR (4DPETMR) scan were used as a surrogate for a test-retest dataset. In the second cohort (n=9), patients underwent first an [18F]-FDG PET/MR scan (SIGNA PET/MR, GE Healthcare, Waukesha) followed by an [18F]-FDG PET/CT scan (Discovery 690, GE Healthcare) with a delay of 33 min ± 5 min (PETCT-PETMR). Lesions were segmented on inhale and exhale 4D-PET phases and on the individual PET scans from PET/CT and PET/MR with two semi-automated methods (gradient-based and threshold-based). The scan resolution was 2.73x2.73x3.27 mm and 2.34x2.34x2.78 mm for the PET/CT and PET/MR, respectively. In total, 1355 radiomic features were calculated, i.e. shape (n=18), intensity (n=17), texture (n=136) and wavelet (n=1184). The intra-class correlation coefficient (ICC) was calculated to compare the radiomic features of the 4DPETMR (ICC(1,1)) and PETCT-PETMR (ICC(3,1)) datasets. An ICC>0.9 was considered stable among both types of PET scans.
RESULTS AND CONCLUSION
4DPETMR showed highest stability for shape, intensity and texture (>80%) and lower stability for wavelet features (40%). Gradient-based method showed higher stability compared to threshold-based method except from shape features. In PETCT-PETMR, more than 61% of shape and intensity features were stable for both segmentation methods. However, a reduced stability was observed for texture (50%) and wavelet (<30%) features. More wavelet features were robust in the smoothed images (low-pass filtering) compared to images with emphasized heterogeneity (high-pass filtering). Comparing stable features of both investigations, highest agreement was found for intensity and lower agreement for shape, texture and wavelet features. Only 53.6% of stable texture features in 4DPETMR were also stable in PETCT-PETMR, and even less in case of wavelet features (40.4%). Approximately 16.9% (texture) and 43.2% (wavelet) of stable PETCT-PETMR features are unstable in 4DPETMR. To conclude, shape and intensity features were robust when comparing two types of [18F]-FDG PET scans (PET/CT and PET/MR). Reduced stability was observed for texture and wavelet features. We identified multiple origins of instability of radiomic features, such as attenuation correction differences, different uptake times and spatial resolution. This needs to be considered when models based on PET/CT are transferred PET/MR models or when combined models are used. This article is protected by copyright. All rights reserved.

Abstract

PURPOSE
Radiomics is a promising tool for identification of new prognostic biomarkers. However, image reconstruction settings and test-retest variability may influence the absolute values of radiomic features. Unstable radiomic features cannot be used as reliable biomarkers. PET/MR is becoming increasingly available and often replaces PET/CT for different indications. The aim of this study was to quantify to what extend [18F]-FDG PET/CT radiomics models can be transferred to [18F]-FDG PET/MR and thereby to investigate the feasibility of combined PET/CT-PET/MR models. For this purpose, we compared PET radiomic features calculated on PET/MR and PET/CT and on a 4D gated PET/MR dataset to select radiomic features that are robust to attenuation correction differences and test-retest variability, respectively.
METHODS
Two cohorts of patients with lung lesions were studied. In the first cohort (n=10), inhale and exhale phases of a 4D [18F]-FDG PET/MR (4DPETMR) scan were used as a surrogate for a test-retest dataset. In the second cohort (n=9), patients underwent first an [18F]-FDG PET/MR scan (SIGNA PET/MR, GE Healthcare, Waukesha) followed by an [18F]-FDG PET/CT scan (Discovery 690, GE Healthcare) with a delay of 33 min ± 5 min (PETCT-PETMR). Lesions were segmented on inhale and exhale 4D-PET phases and on the individual PET scans from PET/CT and PET/MR with two semi-automated methods (gradient-based and threshold-based). The scan resolution was 2.73x2.73x3.27 mm and 2.34x2.34x2.78 mm for the PET/CT and PET/MR, respectively. In total, 1355 radiomic features were calculated, i.e. shape (n=18), intensity (n=17), texture (n=136) and wavelet (n=1184). The intra-class correlation coefficient (ICC) was calculated to compare the radiomic features of the 4DPETMR (ICC(1,1)) and PETCT-PETMR (ICC(3,1)) datasets. An ICC>0.9 was considered stable among both types of PET scans.
RESULTS AND CONCLUSION
4DPETMR showed highest stability for shape, intensity and texture (>80%) and lower stability for wavelet features (40%). Gradient-based method showed higher stability compared to threshold-based method except from shape features. In PETCT-PETMR, more than 61% of shape and intensity features were stable for both segmentation methods. However, a reduced stability was observed for texture (50%) and wavelet (<30%) features. More wavelet features were robust in the smoothed images (low-pass filtering) compared to images with emphasized heterogeneity (high-pass filtering). Comparing stable features of both investigations, highest agreement was found for intensity and lower agreement for shape, texture and wavelet features. Only 53.6% of stable texture features in 4DPETMR were also stable in PETCT-PETMR, and even less in case of wavelet features (40.4%). Approximately 16.9% (texture) and 43.2% (wavelet) of stable PETCT-PETMR features are unstable in 4DPETMR. To conclude, shape and intensity features were robust when comparing two types of [18F]-FDG PET scans (PET/CT and PET/MR). Reduced stability was observed for texture and wavelet features. We identified multiple origins of instability of radiomic features, such as attenuation correction differences, different uptake times and spatial resolution. This needs to be considered when models based on PET/CT are transferred PET/MR models or when combined models are used. This article is protected by copyright. All rights reserved.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Clinic for Radiation Oncology
04 Faculty of Medicine > University Hospital Zurich > Clinic for Nuclear Medicine
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:1 April 2019
Deposited On:15 Mar 2019 12:31
Last Modified:19 Jul 2019 10:57
Publisher:American Association of Physicists in Medicine
ISSN:0094-2405
OA Status:Closed
Publisher DOI:https://doi.org/10.1002/mp.13422
PubMed ID:30714158

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Embargo till: 2020-02-03