101 research outputs found
MINDE: Mutual Information Neural Diffusion Estimation
In this work we present a new method for the estimation of Mutual Information
(MI) between random variables. Our approach is based on an original
interpretation of the Girsanov theorem, which allows us to use score-based
diffusion models to estimate the Kullback Leibler divergence between two
densities as a difference between their score functions. As a by-product, our
method also enables the estimation of the entropy of random variables. Armed
with such building blocks, we present a general recipe to measure MI, which
unfolds in two directions: one uses conditional diffusion process, whereas the
other uses joint diffusion processes that allow simultaneous modelling of two
random variables. Our results, which derive from a thorough experimental
protocol over all the variants of our approach, indicate that our method is
more accurate than the main alternatives from the literature, especially for
challenging distributions. Furthermore, our methods pass MI self-consistency
tests, including data processing and additivity under independence, which
instead are a pain-point of existing methods
One-Line-of-Code Data Mollification Improves Optimization of Likelihood-based Generative Models
Generative Models (GMs) have attracted considerable attention due to their
tremendous success in various domains, such as computer vision where they are
capable to generate impressive realistic-looking images. Likelihood-based GMs
are attractive due to the possibility to generate new data by a single model
evaluation. However, they typically achieve lower sample quality compared to
state-of-the-art score-based diffusion models (DMs). This paper provides a
significant step in the direction of addressing this limitation. The idea is to
borrow one of the strengths of score-based DMs, which is the ability to perform
accurate density estimation in low-density regions and to address manifold
overfitting by means of data mollification. We connect data mollification
through the addition of Gaussian noise to Gaussian homotopy, which is a
well-known technique to improve optimization. Data mollification can be
implemented by adding one line of code in the optimization loop, and we
demonstrate that this provides a boost in generation quality of
likelihood-based GMs, without computational overheads. We report results on
image data sets with popular likelihood-based GMs, including variants of
variational autoencoders and normalizing flows, showing large improvements in
FID score
Continuous-Time Functional Diffusion Processes
We introduce Functional Diffusion Processes (FDPs), which generalize
score-based diffusion models to infinite-dimensional function spaces. FDPs
require a new mathematical framework to describe the forward and backward
dynamics, and several extensions to derive practical training objectives. These
include infinite-dimensional versions of Girsanov theorem, in order to be able
to compute an ELBO, and of the sampling theorem, in order to guarantee that
functional evaluations in a countable set of points are equivalent to
infinite-dimensional functions. We use FDPs to build a new breed of generative
models in function spaces, which do not require specialized network
architectures, and that can work with any kind of continuous data. Our results
on real data show that FDPs achieve high-quality image generation, using a
simple MLP architecture with orders of magnitude fewer parameters than existing
diffusion models.Comment: Under revie
Treatment of osteolytic solitary painful osseous metastases with radiofrequency ablation or cryoablation: a retrospective study by propensity analysis
The present study aimed to measure the improvement in pain relief and quality of life in patients with osteolytic solitary painful bone metastasis treated by cryoablation (CA) or radiofrequency ablation (RFA). Fifty patients with solitary osteolytic painful bone metastases were retrospectively studied and selected by propensity analysis. Twenty-five patients underwent CA and the remaining twenty-five underwent RFA. Pain relief, in terms of complete response (CR), the number of patients requiring analgesia and the changes in self-rated quality of life (QoL) were measured following the two treatments. Thirty-two percent of patients treated by CA experienced a CR at 12 weeks versus 20% of patients treated by RFA. The rate of CR increased significantly with respect to baseline only in the group treated by CA. In both groups there was a significant change in the partial response with respect to baseline (36% in the CA group vs. 44% in the RFA group). The recurrence rate in the CA and RFA groups was 12% and 8%, respectively. The reduction in narcotic medication requirements with respect to baseline was only significant in the group treated by CA. A significant improvement in self-rated QoL was observed in both groups. The present study seems to suggest that CA only significantly improves the rate of CR and decreases the requirement of narcotic medications. Both CA and RFA led to an improvement in the self-rated QoL of patients after the treatments. However, the results of the present study should be considered as preliminary and to serve as a framework around which future trials may be designed
Treatment of Solitary Painful Osseous Metastases with Radiotherapy, Cryoablation or Combined Therapy: Propensity Matching Analysis in 175 Patients
aim of this study was to identify outcomes in pain relief and quality of life in patients with a solitary painful osseous metastasis treated by radiotherapy, cryoablation or the combination using a propensity score matching study design
Segmentation of Planning Target Volume in CT Series for Total Marrow Irradiation Using U-Net
Radiotherapy (RT) is a key component in the treatment of various cancers,
including Acute Lymphocytic Leukemia (ALL) and Acute Myelogenous Leukemia
(AML). Precise delineation of organs at risk (OARs) and target areas is
essential for effective treatment planning. Intensity Modulated Radiotherapy
(IMRT) techniques, such as Total Marrow Irradiation (TMI) and Total Marrow and
Lymph node Irradiation (TMLI), provide more precise radiation delivery compared
to Total Body Irradiation (TBI). However, these techniques require
time-consuming manual segmentation of structures in Computerized Tomography
(CT) scans by the Radiation Oncologist (RO). In this paper, we present a deep
learning-based auto-contouring method for segmenting Planning Target Volume
(PTV) for TMLI treatment using the U-Net architecture. We trained and compared
two segmentation models with two different loss functions on a dataset of 100
patients treated with TMLI at the Humanitas Research Hospital between 2011 and
2021. Despite challenges in lymph node areas, the best model achieved an
average Dice score of 0.816 for PTV segmentation. Our findings are a
preliminary but significant step towards developing a segmentation model that
has the potential to save radiation oncologists a considerable amount of time.
This could allow for the treatment of more patients, resulting in improved
clinical practice efficiency and more reproducible contours
Ensemble Methods for Multi-Organ Segmentation in CT Series
In the medical images field, semantic segmentation is one of the most
important, yet difficult and time-consuming tasks to be performed by
physicians. Thanks to the recent advancement in the Deep Learning models
regarding Computer Vision, the promise to automate this kind of task is getting
more and more realistic. However, many problems are still to be solved, like
the scarce availability of data and the difficulty to extend the efficiency of
highly specialised models to general scenarios. Organs at risk segmentation for
radiotherapy treatment planning falls in this category, as the limited data
available negatively affects the possibility to develop general-purpose models;
in this work, we focus on the possibility to solve this problem by presenting
three types of ensembles of single-organ models able to produce multi-organ
masks exploiting the different specialisations of their components. The results
obtained are promising and prove that this is a possible solution to finding
efficient multi-organ segmentation methods
Celiac disease in type 1 diabetes mellitus
Celiac Disease (CD) occurs in patients with Type 1 Diabetes (T1D) ranging the prevalence of 4.4-11.1% versus 0.5% of the general population. The mechanism of association of these two diseases involves a shared genetic background: HLA genotype DR3-DQ2 and DR4-DQ8 are strongly associated with T1D, DR3-DQ2 with CD. The classical severe presentation of CD rarely occurs in T1D patients, but more often patients have few/mild symptoms of CD or are completely asymptomatic (silent CD). In fact diagnosis of CD is regularly performed by means of the screening in T1D patients. The effects of gluten-free diet (GFD) on the growth and T1D metabolic control in CD/T1D patient are controversial. Regarding of the GFD composition, there is a debate on the higher glycaemic index of gluten-free foods respect to gluten-containing foods; furthermore GFD could be poorer of fibers and richer of fat. The adherence to GFD by children with CD-T1D has been reported generally below 50%, lower respect to the 73% of CD patients, a lower compliance being more frequent among asymptomatic patients. The more severe problems of GFD adherence usually occur during adolescence when in GFD non compliant subjects the lowest quality of life is reported. A psychological and educational support should be provided for these patients
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