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Your search keyword '"Niklaus Schaefer"' showing total 4 results
Start Over Author "Niklaus Schaefer" Journal scientific reports
4 results on '"Niklaus Schaefer"'

1. Comparing various AI approaches to traditional quantitative assessment of the myocardial perfusion in [82Rb] PET for MACE prediction

Author

Sacha Bors, Daniel Abler, Matthieu Dietz, Vincent Andrearczyk, Julien Fageot, Marie Nicod-Lalonde, Niklaus Schaefer, Robert DeKemp, Christel H. Kamani, John O. Prior, and Adrien Depeursinge

Subjects
Medicine, Science
Abstract

Abstract Assessing the individual risk of Major Adverse Cardiac Events (MACE) is of major importance as cardiovascular diseases remain the leading cause of death worldwide. Quantitative Myocardial Perfusion Imaging (MPI) parameters such as stress Myocardial Blood Flow (sMBF) or Myocardial Flow Reserve (MFR) constitutes the gold standard for prognosis assessment. We propose a systematic investigation of the value of Artificial Intelligence (AI) to leverage [ $$^{82}$$ 82 Rb] Silicon PhotoMultiplier (SiPM) PET MPI for MACE prediction. We establish a general pipeline for AI model validation to assess and compare the performance of global (i.e. average of the entire MPI signal), regional (17 segments), radiomics and Convolutional Neural Network (CNN) models leveraging various MPI signals on a dataset of 234 patients. Results showed that all regional AI models significantly outperformed the global model ( $$p

Published
2024
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2. 99mTc-macroaggregated albumin SPECT/CT predictive dosimetry and dose-response relationship in uveal melanoma liver metastases treated with first-line selective internal radiation therapy

Author

Flavian Tabotta, Silvano Gnesin, Vincent Dunet, Alexandre Ponti, Antonia Digklia, Sarah Boughdad, Niklaus Schaefer, John O. Prior, Nicolas Villard, Georgia Tsoumakidou, Alban Denys, and Rafael Duran

Subjects
Medicine, Science
Abstract

Abstract First-line selective internal radiation therapy (SIRT) showed promising outcomes in patients with uveal melanoma liver metastases (UMLM). Patient survival depends on liver’s disease control. SIRT planning is essential and little is known about dosimetry. We investigated whether 99mTc-MAA-SPECT/CT dosimetry could predict absorbed doses (AD) evaluated on 90Y-PET/CT and assess the dose–response relationship in UMLM patients treated with first-line SIRT. This IRB-approved, single-center, retrospective analysis (prospectively collected cohort) included 12 patients (median age 63y, range 43–82). Patients underwent MRI/CT, 18F-FDG-PET/CT before and 3–6 months post-SIRT, and 90Y-PET/CT immediately post-SIRT. Thirty-two target lesions were included. AD estimates in tumor and non-tumor liver were obtained from 99mTc-MAA-SPECT/CT and post-SIRT 90Y-PET/CT, and assessed with Lin’s concordance correlation coefficients (ρ c and C b), Pearson’s coefficient correlation (ρ), and Bland–Altman analyses (mean difference ± standard deviation; 95% limits-of-agreement (LOA)). Influence of tumor characteristics and microsphere type on AD was analyzed. Tumor response was assessed according to size-based, enhancement-based and metabolic response criteria. Mean target lesion AD was 349 Gy (range 46–1586 Gy). Concordance between 99mTc-MAA-SPECT/CT and 90Y-PET/CT tumor dosimetry improved upon dose correction for the recovery coefficient (RC) (ρ = 0.725, ρ c = 0.703, C b = 0.969) with good agreement (mean difference: − 4.93 ± 218.3 Gy, 95%LOA: − 432.8–422.9). Without RC correction, concordance was better for resin microspheres (ρ = 0.85, ρ c = 0.998, C b = 0.849) and agreement was very good between predictive 99mTc-MAA-SPECT/CT and 90Y-PET/CT dosimetry (mean difference: − 4.05 ± 55.9 Gy; 95%LOA: − 113.7–105.6). After RC correction, 99mTc-MAA-SPECT/CT dosimetry overestimated AD (− 70.9 ± 158.9 Gy; 95%LOA: − 382.3–240.6). For glass microspheres, concordance markedly improved with RC correction (ρ = 0.790, ρ c = 0.713, C b = 0.903 vs without correction: ρ = 0.395, ρ c = 0.244, C b = 0.617) and 99mTc-MAA-SPECT/CT dosimetry underestimated AD (148.9 ± 267.5 Gy; 95%LOA: − 375.4–673.2). For non-tumor liver, concordance was good between 99mTc-MAA-SPECT/CT and 90Y-PET/CT dosimetry (ρ = 0.942, ρ c = 0.852, C b = 0.904). 99mTc-MAA-SPECT/CT slightly overestimated liver AD for resin (3.4 ± 3.4 Gy) and glass (11.5 ± 13.9 Gy) microspheres. Tumor AD was not correlated with baseline or post-SIRT lesion characteristics and no dose–response threshold could be identified. 99mTc-MAA-SPECT/CT dosimetry provides good estimates of AD to tumor and non-tumor liver in UMLM patients treated with first-line SIRT.

Published
2023
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3. Increased 18F-FDG signal recovery from small physiological structures in digital PET/CT and application to the pituitary gland

Author

Marie Meyer, John O. Prior, Marie Nicod Lalonde, Silvano Gnesin, Niklaus Schaefer, and Gilles Allenbach

Subjects
PET-CT, Pituitary gland, Multidisciplinary, business.industry, lcsh:R, lcsh:Medicine, Imaging phantom, 030218 nuclear medicine & medical imaging, Background level, 03 medical and health sciences, 0302 clinical medicine, Increased risk, medicine.anatomical_structure, Signal recovery, 030220 oncology & carcinogenesis, medicine, In patient, lcsh:Q, Nuclear medicine, business, Metabolic activity, lcsh:Science
Abstract

On conventional PET/CT, and under physiological conditions, the volume of the pituitary gland (PG) is small, and its metabolic activity is commonly comparable to the surrounding background level in 18F-FDG imaging. We compared the physiological 18F-FDG uptake of the PG in patients imaged with digital PET (dPET) and with conventional PET (cPET). Additionally, we performed phantom experiments to characterize signal recovery and detectability of small structures. We retrospectively included 10 dPET and 10 cPET patients and measured PG SUVmax, SUVmean and SUVratio (using cerebellum as reference). We imaged a modified NEMA/IEC phantom with both dPET and cPET (background activity 5 kBq/mL, and 3× and 5× higher concentrations in ∅2–20-mm spherical inserts). Mean recovery coefficients (RCmean) and signal-difference-to-noise-ratio (SDNR) were computed to assess lesion detectability. Patients imaged with dPET presented higher PG SUVmax and SUVratio (SUVR) compared to patients imaged with cPET (4.7 ± 2.05 vs. 2.9 ± 0.64, p = 0.004; and 0.62 ± 0.25 vs 0.39 ± 0.09, p = 0.029, respectively), while there was no difference for SUVmean (2.7 ± 1.32 vs 2.1 ± 0.44, p = 0.39). Thus, with a SUV readout scale of 0–5 g/mL, normal PG appeared abnormally hot with dPET, but not with cPET. Phantom evidenced higher RCmean in dPET compared to cPET. For both 3x and 5x measurements, lesion detectability according to size was systematically superior with dPET. In conclusion, patients imaged with dPET presented higher 18F-FDG physiological uptake of the PG as compared to patients imaged with cPET. These findings were supported by phantom experiments demonstrating superior signal recovery and small region detectability with dPET. Awareness of this new “higher” SUV of the normal 18F-FDG uptake of the PG is important to avoid potential pitfalls in image interpretation, notably in oncologic patients treated with immunotherapy, who are at increased risk to develop hypophysitis.

Published
2020

4. Increased

Author

Marie, Meyer, Gilles, Allenbach, Marie, Nicod Lalonde, Niklaus, Schaefer, John O, Prior, and Silvano, Gnesin

Subjects
Male, Molecular medicine, Pituitary Diseases, Middle Aged, Article, Metabolic Diseases, Fluorodeoxyglucose F18, Pituitary Gland, Positron Emission Tomography Computed Tomography, Humans, Female, Cancer imaging, Aged, Retrospective Studies
Abstract

On conventional PET/CT, and under physiological conditions, the volume of the pituitary gland (PG) is small, and its metabolic activity is commonly comparable to the surrounding background level in 18F-FDG imaging. We compared the physiological 18F-FDG uptake of the PG in patients imaged with digital PET (dPET) and with conventional PET (cPET). Additionally, we performed phantom experiments to characterize signal recovery and detectability of small structures. We retrospectively included 10 dPET and 10 cPET patients and measured PG SUVmax, SUVmean and SUVratio (using cerebellum as reference). We imaged a modified NEMA/IEC phantom with both dPET and cPET (background activity 5 kBq/mL, and 3× and 5× higher concentrations in ∅2–20-mm spherical inserts). Mean recovery coefficients (RCmean) and signal-difference-to-noise-ratio (SDNR) were computed to assess lesion detectability. Patients imaged with dPET presented higher PG SUVmax and SUVratio (SUVR) compared to patients imaged with cPET (4.7 ± 2.05 vs. 2.9 ± 0.64, p = 0.004; and 0.62 ± 0.25 vs 0.39 ± 0.09, p = 0.029, respectively), while there was no difference for SUVmean (2.7 ± 1.32 vs 2.1 ± 0.44, p = 0.39). Thus, with a SUV readout scale of 0–5 g/mL, normal PG appeared abnormally hot with dPET, but not with cPET. Phantom evidenced higher RCmean in dPET compared to cPET. For both 3x and 5x measurements, lesion detectability according to size was systematically superior with dPET. In conclusion, patients imaged with dPET presented higher 18F-FDG physiological uptake of the PG as compared to patients imaged with cPET. These findings were supported by phantom experiments demonstrating superior signal recovery and small region detectability with dPET. Awareness of this new “higher” SUV of the normal 18F-FDG uptake of the PG is important to avoid potential pitfalls in image interpretation, notably in oncologic patients treated with immunotherapy, who are at increased risk to develop hypophysitis.

Published
2019

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