A mirror-Unet architecture for PET/CT lesion segmentation

Automatic lesion detection and segmentation from [${}^{18}$F]FDG PET/CT scans is a challenging task, due to the diversity of shapes, sizes, FDG uptake and location they may present, besides the fact that physiological uptake is also present on healthy tissues. In this work, we propose a deep learning method aimed at the segmentation of oncologic lesions, based on a combination of two UNet-3D branches. First, one of the network's branches is trained to segment a group of tissues from CT images. The other branch is trained to segment the lesions from PET images, combining on the bottleneck the embedded information of CT branch, already trained. We trained and validated our networks on the AutoPET MICCAI 2023 Challenge dataset. Our code is available at: https://github.com/yrotstein/AutoPET2023_Mv1

Towards semi-inclusive deep inelastic scattering at next-to-next-to-leading order

In this paper, we compute the first set of ${\cal O}(\alpha_s^2)$ corrections to semi-inclusive deep inelastic scattering structure functions. We start by studying the impact of the contribution of the partonic subprocesses that open at this order for the longitudinal structure function. We perform the full calculation analytically, and obtain the expression of the factorized cross section at this order. Special care is given to the study of their flavour decomposition structure. We analyze the phenomenological effect of the corrections finding that, even though expected to be small a priori, it turns out to be sizable with respect to the previous order know, calling for a full NNLO calculation.Comment: 25 pages, 5 figure

A complete O(alpha_S^2) calculation of the signal-background interference for the Higgs diphoton decay channel

We present the full {\cal O}(\as^2) computation of the interference effects between the Higgs diphoton signal and the continuum background at the LHC. While the main contribution to the interference originates on the $gg$ partonic subprocess, we find that the corrections from the $qg$ and $q\bar{q}$ channels amount up to 35% of it. We discuss the effect of these new subprocesses in the shift of the diphoton invariant mass peak recently reported by S. Martin in Ref.\cite{Martin:2012xc}.Comment: 8 pages, 5 figure

Direct observation of magnetocaloric effect by differential thermal analysis: Influence of experimental parameters

The magnetocaloric effect is the isothermal change of magnetic entropy and the adiabatic temperature change induced in a magnetic material when an external magnetic field is applied. In this work, we present an experimental setup to study this effect in metamagnetic transitions, using the differential thermal analysis technique, which consists in measuring simultaneously the temperatures of the sample of interest and a reference one while an external magnetic field ramp is applied. We have tested our system to measure the magnetocaloric effect in La0.305Pr0.32Ca0.375MnO3, which presents phase separation effects at low temperatures (T < 200 K). We obtain ∆T vs H curves, and analyze how the effect varies by changing the external pressure and the rate of the magnetic field ramp. Our results show that the optimum conditions to measure the effect are at the lower pressures (< 10−4 Torr) and faster changes of the magnetic field. However, at very high vacuum, a temperature gradient appears and makes it difficult to set the temperature properly. Also, self-heating of the sensor becomes relevant at this condition, so care must be taken in order to establish the external conditions. We have obtained the effective heat capacity of the system without the sample by performing calorimetric measurements using a pulse heat method, fiting the temperature change with a two tau description. With this analysis, we are able to describe the influence of the environment and subtract it to calculate the adiabatic temperature change of the sample.Fil: Rotstein Habarnau, Yamila Valeria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Bergamasco, Pablo. Comisión Nacional de Energía Atómica; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Sacanell, Joaquin Gonzalo. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Leyva, Gabriela. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); ArgentinaFil: Albornoz, Cecilia. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); ArgentinaFil: Quintero, Mariano Horacio. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Polarized semi-inclusive electroweak structure functions at next-to-leading-order

We present a next-to-leading order (NLO) computation of the full set of polarized and unpolarized electroweak semi-inclusive DIS (SIDIS) structure functions, whose knowledge is crucial for a precise extraction of polarized parton distributions. We focus on the phenomenology of the polarized structure functions for the kinematical conditions that could be reached in an Electron-Ion-Collider. We show that the NLO corrections are sizeable, particularly in the small-$x$ range. We test the sensitivity of these structure functions on certain quark distributions and compare it to the situation of inclusive DIS and electromagnetic SIDIS.Comment: 17 pages, 5 figure

Precision studies of semi-inclusive processes at high energy colliders

Se estudian en esta tesis procesos semi-inclusivos en colisionadores de altas energías, con el fin de contar con la descripción más precisa posible de dichos fenómenos. Este tipo de procesos se caracterizan por la observación de un leptón o hadrón en el estado final. En particular, analizamos los procesos de dispersión inelástica profunda semiinclusiva (SIDIS) y la producción de un bosón W decayendo en un par leptón-neutrino en colisionadores hadrónicos.En primer lugar, se presenta en este trabajo la primera etapa del análisis de la componente longitudinal de SIDIS a segundo orden en teoría de perturbaciones en la constante de acoplamiento de la teoría de la Cromodinámica Cuántica (QCD), es decir a next-to-next-to-leading-order (NNLO). Hemos realizado el cálculo completamente analítico de la contribución a las funciones de estructura longitudinales de los canales partónicos que contribuyen por primera vez al orden analizado, que cuentan con la ventaja de no contener contribuciones con lazos (loops) ni distribuciones. Además, se presentan aspectos generales relacionados con la organización de un futuro cálculo completo a NNLO, como la descomposición en sabores de la sección eficaz total y un resumen de las diferentes contribuciones partónicas a tener en cuenta.Por otro lado, se estudia en esta tesis el proceso de producción de un leptón a través del decaimiento de un bosón W en la colisión de dos protones polarizados, tal como sucede en el Relativistic Heavy Ion Collider (RHIC). En particular, se realiza la resumación a todo orden en la constante de acomplamiento fuerte de las grandes correcciones logarítmicas que surgen cerca de la región cinemática umbral en que el espacio de fase disponible para la radiación de gluones reales se ve reducida. Este procedimiento se conoce como resumación de umbral y permite mejorar el comportamiento de la serie perturbativa. Estudiamos en este trabajo la implementación de la resumación de umbral al orden siguiente al dominante, conocido como next-to-leading logarithmic (NLL).We study in this thesis semi-inclusive processes at high energy colliders, in order to obtain the most precise description of such phenomena. This kind of processes are characterized by the observation of a lepton or a hadron in the nal state. In particular, we study semi-inclusive deep inelastic scattering (SIDIS) and the production of a W boson, decaying into a lepton-neutrino pair, in hadron colliders. Firstly, we present the rst stage of the analysis of the longitudinal component of SIDIS at second order in perturbation theory in the strong coupling constant of Quantum ChromoDynamics (QCD), that is to say at next-to-next-to-leading-order (NNLO). We have performed the fully analytical computation of the contributions to the longitudinal structure function of those partonic channels that open for the rst time at this order, which have the advantage of presenting no loop corrections and no distributions. Besides, we show some general issues related to the organization of a future complete computation at NNLO, such as the avor decomposition of the total cross section and a summary of the di erent partonic contributions that must be taken into account. In addition, we study the process of lepton production through the decay of an intermediate W boson in the collision of two polarized protons, as measured at the Relativistic Heavy Ion Collider (RHIC). In particular, we perform the all-order resummation of the large logarithmic corrections arising near threshold, when the available phase space for real gluon emission is reduced. This procedure is known as threshold resummation and improves the behavior of the perturbative expansion. We perform the implementation of threshold resummation at next-to-leading logarithmic accuracy (NLL).Fil: Rotstein Habarnau, Yamila Valeria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Exploring the applicability of a lesion segmentation method on [18F]fluorothymidine PET/CT images in diffuse large B-cell lymphoma

Abstract Background and purpose The determination of the total metabolic tumour volume based on [18F]fluorothymidine ([18F]FLT) PET/CT images in diffuse large B-cell lymphoma has a potential clinical value for detecting early relapse in this type of heterogeneous lymphoproliferative tumours. Tumour segmentation is a key step in this process. For this purpose, our objective was to determine a segmentation threshold of [18F]FLT PET/CT images, based on a reference tissue uptake, on a cohort of patients with diffuse large B-cell lymphoma (DLBCL) that have been scanned at different stages of the treatment. Methods We enrolled 23 adult patients with DLBCL confirmed in II-IV stages without nervous system compromise. All patients were scanned using [18F]FLT PET/CT at the time of diagnosis (baseline PET), interim PET (iPET), and at the end of treatment (fPET). The administered activity was 1.8–2.6 MBq/kg body weight, performed 60–70 min after injection and without use of contrast-enhanced CT. First, we assessed the [18F]FLT uptake stability in liver and bone marrow along the patient follow-up. For the lesion segmentation, three threshold values were assessed. Results Both, liver, and bone marrow can be indistinctly taken as reference tissue. The SUV threshold for a voxel to be considered as belonging to a lesion is expressed in terms of a percentage relative to the patient’s uptake in the reference tissue. Found thresholds were: for liver, 62%, 33%, 27%; and for bone marrow, 35%, 21% and 22%, for baseline, iPET and fPET stages, respectively. The relative threshold throughout the treatment has a decreasing tendency along the stages. Conclusion Based on the results obtained with [18F]FLT PET/CT during staging and follow-up in patients with DLBCL, reference values were obtained for each stage referring to liver and bone marrow uptake that could be used in clinical practice oncology