128 research outputs found
Simulation of Arbitrary Level Contrast Dose in MRI Using an Iterative Global Transformer Model
Deep learning (DL) based contrast dose reduction and elimination in MRI
imaging is gaining traction, given the detrimental effects of Gadolinium-based
Contrast Agents (GBCAs). These DL algorithms are however limited by the
availability of high quality low dose datasets. Additionally, different types
of GBCAs and pathologies require different dose levels for the DL algorithms to
work reliably. In this work, we formulate a novel transformer (Gformer) based
iterative modelling approach for the synthesis of images with arbitrary
contrast enhancement that corresponds to different dose levels. The proposed
Gformer incorporates a sub-sampling based attention mechanism and a rotational
shift module that captures the various contrast related features. Quantitative
evaluation indicates that the proposed model performs better than other
state-of-the-art methods. We further perform quantitative evaluation on
downstream tasks such as dose reduction and tumor segmentation to demonstrate
the clinical utility.Comment: Accepted in MICCAI 202
Non-Invasive Placental Perfusion Imaging in Pregnancies Complicated by Fetal Heart Disease Using Velocity-Selective Arterial Spin Labeled MRI
The placenta is a vital organ for fetal growth and development during pregnancy. Congenital heart disease (CHD) is a leading cause of morbidity and mortality in newborns. Despite the parallel development of the placenta and fetal heart early in pregnancy, very few studies suggested an association between placental dysfunction and fetal CHD. In this study, we report placental perfusion of healthy pregnancies and pregnancies complicated by fetal CHD measured using advanced fetal MRI techniques. We studied forty-eight pregnant women (31 healthy volunteers and 17 with fetal CHD) that underwent fetal MRI during their second or third trimester of pregnancy. Placental perfusion imaging was performed using velocity-selective arterial spin labeling (VSASL) and 3D image acquisition with whole-placenta coverage. In pregnancies with fetal CHD, global placental perfusion significantly decreased and regional variation of placental perfusion significantly increased with advancing gestational age; however, no such correlation was found in healthy pregnancies. Also, global placental perfusion was significantly higher in fetal CHD versus controls, in the lateral side-lying patient position versus supine, and in the posterior placental position versus anterior placental position. This study reports for the first time non-invasive whole-placenta perfusion imaging in utero. These data suggest that placental VSASL may serve as a potential biomarker of placental dysfunction in fetuses diagnosed with CHD
Non-Invasive Placental Perfusion Imaging in Pregnancies Complicated by Fetal Heart Disease Using Velocity-Selective Arterial Spin Labeled MRI.
The placenta is a vital organ for fetal growth and development during pregnancy. Congenital heart disease (CHD) is a leading cause of morbidity and mortality in newborns. Despite the parallel development of the placenta and fetal heart early in pregnancy, very few studies suggested an association between placental dysfunction and fetal CHD. In this study, we report placental perfusion of healthy pregnancies and pregnancies complicated by fetal CHD measured using advanced fetal MRI techniques. We studied forty-eight pregnant women (31 healthy volunteers and 17 with fetal CHD) that underwent fetal MRI during their second or third trimester of pregnancy. Placental perfusion imaging was performed using velocity-selective arterial spin labeling (VSASL) and 3D image acquisition with whole-placenta coverage. In pregnancies with fetal CHD, global placental perfusion significantly decreased and regional variation of placental perfusion significantly increased with advancing gestational age; however, no such correlation was found in healthy pregnancies. Also, global placental perfusion was significantly higher in fetal CHD versus controls, in the lateral side-lying patient position versus supine, and in the posterior placental position versus anterior placental position. This study reports for the first time non-invasive whole-placenta perfusion imaging in utero. These data suggest that placental VSASL may serve as a potential biomarker of placental dysfunction in fetuses diagnosed with CHD. © 2017 The Author(s)
Brain MRI-to-PET Synthesis using 3D Convolutional Attention Networks
Accurate quantification of cerebral blood flow (CBF) is essential for the
diagnosis and assessment of a wide range of neurological diseases. Positron
emission tomography (PET) with radiolabeled water (15O-water) is considered the
gold-standard for the measurement of CBF in humans. PET imaging, however, is
not widely available because of its prohibitive costs and use of short-lived
radiopharmaceutical tracers that typically require onsite cyclotron production.
Magnetic resonance imaging (MRI), in contrast, is more readily accessible and
does not involve ionizing radiation. This study presents a convolutional
encoder-decoder network with attention mechanisms to predict gold-standard
15O-water PET CBF from multi-sequence MRI scans, thereby eliminating the need
for radioactive tracers. Inputs to the prediction model include several
commonly used MRI sequences (T1-weighted, T2-FLAIR, and arterial spin
labeling). The model was trained and validated using 5-fold cross-validation in
a group of 126 subjects consisting of healthy controls and cerebrovascular
disease patients, all of whom underwent simultaneous $15O-water PET/MRI. The
results show that such a model can successfully synthesize high-quality PET CBF
measurements (with an average SSIM of 0.924 and PSNR of 38.8 dB) and is more
accurate compared to concurrent and previous PET synthesis methods. We also
demonstrate the clinical significance of the proposed algorithm by evaluating
the agreement for identifying the vascular territories with abnormally low CBF.
Such methods may enable more widespread and accurate CBF evaluation in larger
cohorts who cannot undergo PET imaging due to radiation concerns, lack of
access, or logistic challenges.Comment: 19 pages, 14 figure
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