Browsing by Author "Branco, Susana"
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- Evaluation of the respiratory motion effect in small animal PET images with GATE Monte Carlo simulationsPublication . Branco, Susana; Almeida, Pedro; Jan, SébastienThe rapid growth in genetics and molecular biology combined with the development of techniques for genetically engineering small animals has led to increased interest in in vivo small animal imaging. Small animal imaging has been applied frequently to the imaging of small animals (mice and rats), which are ubiquitous in modeling human diseases and testing treatments. The use of PET in small animals allows the use of subjects as their own control, reducing the interanimal variability. This allows performing longitudinal studies on the same animal and improves the accuracy of biological models. However, small animal PET still suffers from several limitations. The amounts of radiotracers needed, limited scanner sensitivity, image resolution and image quantification issues, all could clearly benefit from additional research. Because nuclear medicine imaging deals with radioactive decay, the emission of radiation energy through photons and particles alongside with the detection of these quanta and particles in different materials make Monte Carlo method an important simulation tool in both nuclear medicine research and clinical practice. In order to optimize the quantitative use of PET in clinical practice, data- and image-processing methods are also a field of intense interest and development. The evaluation of such methods often relies on the use of simulated data and images since these offer control of the ground truth. Monte Carlo simulations are widely used for PET simulation since they take into account all the random processes involved in PET imaging, from the emission of the positron to the detection of the photons by the detectors. Simulation techniques have become an importance and indispensable complement to a wide range of problems that could not be addressed by experimental or analytical approaches.
- Immunotherapy in triple-negative breast cancer: the role of immune checkpoint inhibitorsPublication . Branco, Susana; Graça, Maria Inês; Morais, SaraABSTRACT - Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer, associated with a poor prognosis in both early and advanced stages. Chemotherapy remains the standard treatment for these patients, despite its limited benefit. Due to the disease’s aggressive features and lack of targeted therapies, several attempts have been made to disclose novel molecular targets. TNBC is now known to be an immunogenic breast cancer subtype. Therefore, immunotherapy has emerged as a promising treatment option for this disease. During the last few years, immune checkpoint inhibitors (anti-PD1/PD-L1 and anti-CTLA-4 monoclonal antibodies) have been investigated either as monotherapy or combined with conventional therapy in TNBC. Herein, we review the status of immunotherapy in TNBC, focusing on the value of immune checkpoint inhibitors.
- Minimisation of acquisition time in a TOF PET/CT scanner without compromising image qualityPublication . Oliveira, Joana; Parafita, Rui; Branco, SusanaSignificant improvements have been made in Positron Emission Tomography (PET) to enhance the image quality, namely, the development of time-of-flight (TOF) technology. This technique is useful to localize the emission point of the beta plus-emitter (β+) radiopharmaceutical inside the body, allowing better lesion contrast and leading to a short scan time. The main goal of this study is to investigate the shortest acquisition time without compromising the image quality in both a NEMA body phantom and patients, using a TOF PET/Computed Tomography (PET/CT) scanner and the radionuclide Gallium-68 (68Ga). Image quality parameters and quantification in terms of standardized uptake value (SUV) were acquired. A time between 45 and 60 s per bed position is proposed for future clinical practices.
- Minimisation of acquisition time in a TOF PET/CT scanner without compromising image qualityPublication . Oliveira, Joana; Parafita, Rui; Branco, SusanaIntroduction - Significant improvements have been made in Positron Emission Tomography/Computed Tomography (PET/CT) to enhance the image quality, namely, the development of time-of-flight (TOF) technology. This technique is useful to localize the emission point of the beta plus-emitter (β+) radiopharmaceutical inside the body, allowing better lesion contrast, especially for large patients, improving structural details and leading to a short scan time. The main goal of this study is to verify the shortest acquisition time per bed position, in a TOF PET scanner, without compromising the image quality, in both phantom and clinical imaging. Methods - For that purpose, images of a torso NEMA phantom were acquired with different acquisition times per bed position (30, 45, 60, 80 and 120 s) in a TOF PET/CT scanner (GEMINI TF 16, Philips), using Gallium-68 (68Ga) citrate. Clinical images were also acquired of an aleatory patient (male, 64 y) with 68Ga-prostate specific membrane antigen (68Ga-PSMA). Image quality parameters, such as signal-to-noise ratio (SNR), noise, contrast, contrast-to-noise ratio (CNR), contrast recovery coefficient (CRC) and quantification in terms of standardized uptake value (SUV) were acquired. Results - The increased contrast and CRC in larger spheres and with longer acquisition times produces an increase on the noise, leading to a decrease in SNR and CNR. In phantom imaging, SUVmax varied between 1.1 and 1.6 for background (normal uptake) and between 2.1 and 8.0 for spheres (abnormal uptake). A strong correlation was found for both SUVmax and SUVmean between the different acquisition times (R>0.7). Inpatient imaging, spleen showed higher SNR, contrast, noise, and CNR than liver. Median SUVmax was 7.1 for liver, 9.8 for spleen and 1.8 for bone. Conclusions - A time between 45 and 60 s per bed position is proposed for future clinical practices, allowing schedule more scans per day, contributing to an optimization of protocols without compromising the image quality.
- PET/CT e PET/RMPublication . Branco, SusanaIndividualmente nenhuma modalidade imagiológica oferece em simultâneo uma elevada resolução espacial e temporal, aliado a uma boa resolução de contraste e sensibilidade. No entanto, combinações de diferentes modalidades podem aproximar-se deste ideal, permitindo a integração de diferentes sistemas num sistema de imagem única. Um dos marcos históricos da medicina nuclear ocorreu com o aparecimento dos sistemas de Tomografia por Emissão de Positrões/Tomografia Computorizada (PET/CT) que permitem obter, em simultâneo, informações funcionais e anatómicas sobre as alterações metabólicas e estruturais que ocorrem em situações de doença.