Abstract
ObjectivesTo investigate the reliability of simultaneous positron emission tomography and magnetic resonance imaging (PET/MRI)-derived biomarkers using semi-automated Gaussian mixture model (GMM) segmentation on PET images, against conventional manual tumor segmentation on dynamic contrast-enhanced (DCE) images.Materials and methodsTwenty-four breast cancer patients underwent PET/MRI (following 18F-fluorodeoxyglucose (18F-FDG) injection) at baseline and during neoadjuvant treatment, yielding 53 data sets (24 untreated, 29 treated). Two-dimensional tumor segmentation was performed manually on DCE–MRI images (manual DCE) and using GMM with corresponding PET images (GMM–PET). Tumor area and mean apparent diffusion coefficient (ADC) derived from both segmentation methods were compared, and spatial overlap between the segmentations was assessed with Dice similarity coefficient and center-of-gravity displacement.ResultsNo significant differences were observed between mean ADC and tumor area derived from manual DCE segmentation and GMM–PET. There were strong positive correlations for tumor area and ADC derived from manual DCE and GMM–PET for untreated and treated lesions. The mean Dice score for GMM–PET was 0.770 and 0.649 for untreated and treated lesions, respectively.DiscussionUsing PET/MRI, tumor area and mean ADC value estimated with a GMM–PET can replicate manual DCE tumor definition from MRI for monitoring neoadjuvant treatment response in breast cancer.
Highlights
Breast cancer is the most frequent type of cancer in women worldwide [1], with a mean 5-year survival of 90.4% in Norway [2]
center-ofgravity displacement (CoG) measurements were significantly lower for Gaussian mixture model (GMM)–PET compared to S UV2.5 for treated lesions (p = 0.002) (Fig. 4b)
Our study demonstrates a strong correlation between tumor apparent diffusion coefficient (ADC) values derived from GMM with corresponding PET images (GMM–PET) and manual dynamic contrast-enhanced (DCE) segmentation, in line with a previous study by Byun et al [19] using a similar approach in breast carcinomas; our study utilizes the intrinsic voxel correspondence of simultaneous positron emission tomography and magnetic resonance imaging (PET/MRI), avoiding the additional registration required by sequential FDG–PET/CT and Diffusion-weighted magnetic resonance imaging (DWI) and conferring greater confidence in the results
Summary
Breast cancer is the most frequent type of cancer in women worldwide [1], with a mean 5-year survival of 90.4% in Norway [2]. Patients diagnosed with locally advanced breast cancer (LABC, stage 3), have a worse survival outcome (78.3%) [2]. They receive neoadjuvant chemotherapy treatment before surgery with the goal of complete pathological tumor regression, which correlates with improved survival and a reduced chance of breast cancer recurrence [3]. Magnetic Resonance Materials in Physics, Biology and Medicine (2020) 33:317–328
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