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Craniofacial Regeneration—Bone
Published in Vincenzo Guarino, Marco Antonio Alvarez-Pérez, Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Laura Guadalupe Hernandez, Lucia Pérez Sánchez, Rafael Hernández González, Janeth Serrano-Bello
PET scans also use radiopharmaceuticals to create three-dimensional images. The main difference between SPECT and PET scans is the type of radiotracers used. While SPECT scans measure gamma rays, the decomposition of radiotracers used with PET scans produces small particles called positrons. A positron is a particle with approximately the same mass as an electron, but with an opposite charge. These react with the electrons in the body and when these two particles combine they annihilate each other. This annihilation produces a small amount of energy in the form of two photons that fire in opposite directions. The PET scanner detectors measure these photons and use this information to create images of the internal organs. With this non-invasive technique, quantitative information on biological processes at the molecular level is obtained through tomographic images that reflect the concentration of activity of a radiopharmaceutical administered to a patient. The information obtained depends on the metabolic pathway, the targeted target receptor, the biodistribution and the rates of accumulation and elimination of the radiopharmaceutical. This makes it possible to perform an early detection of pathological processes with PET (Phelps 2000).
PET-CT
Published in Anju Sahdev, Sarah J. Vinnicombe, Husband & Reznek's Imaging in Oncology, 2020
Mario Jreige, Marie Nicod-Lalonde, John O Prior, Niklaus Schaefer
Positron emission tomography (PET) is an important tool in cancer diagnostics since it allows virtually any biochemical process in the human body to be followed with positron-emitting radiotracers, injected in picomolar quantities (1). Radiotracers consist of a radioactive, positron-emitting isotope, linked to a biological tracer, targeting any biochemical process, receptor, or any other druggable target (2). Isotopes suitable for PET imaging are proton-rich, such as 18F, 13N, 15O, 68Ga, 82Rb, or 89Zr and decay by emission of a neutron, a positron, and a neutrino. The emitted positron annihilates with a local electron after a short travel through matter (18F; ∼1 mm) with emission of two 511 keV gamma photons at 180° to each other.
Images from Radioactivity: Radionuclide Scans, SPECT, and PET
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
The spatial resolution of PET scans is limited in practice to 4 mm for current scanners for humans. This is appreciably worse than the best resolutions achievable by CT, MRI, and ultrasound, but an improvement over SPECT. PET's spatial resolution is inherently limited by the positron's range in body tissue, in addition to the usual imaging geometry limitations (Table 6.4). This is because emitted positrons travel within the body before annihilating, corrupting information about the position of the original decay site. With improvements in detector design, or by confining the field of view to smaller volumes for the brain or small research animals, higher spatial resolutions are being achieved, but the fundamental limits are not appreciably smaller than current values.
Metastatic seminoma presenting as neck and axillary lymphadenopathy in an elderly man
Published in Baylor University Medical Center Proceedings, 2023
Binoy Yohannan, Allen Omo-Ogboi, Johncy John Kachira, Syed H. Jafri
A Hispanic man in his 60s presented with a 1-year history of a gradually progressive right-sided neck mass. Initial core biopsy showed fibrous tissue with a mild lymphohistiocytic infiltrate; acid-fast bacilli and Grocott’s methenamine silver stains were negative for acid-fast and fungal organisms, respectively. No overt features of malignancy were identified. He was started on oral prednisone for presumed sarcoidosis. Two months later, the neck mass significantly increased in size, and he developed dysphagia to solids, hoarseness of voice, anorexia, moderate weight loss, and shortness of breath. He denied fever, chills, night sweats, cough, chest pain, or palpitations. He was a nonsmoker. On examination, his vital signs were stable. He had no stridor. A hard, fixed 10 × 15 cm right neck mass and 3 × 4 cm left neck mass was palpable. No ulcers or lesions were noted in the oral cavity. He had enlarged right axillary lymph nodes but no inguinal or supraclavicular lymphadenopathy. He had no evidence of a testicular mass. Complete blood count, comprehensive metabolic panel, and erythrocyte sedimentation rate were within normal limits. Infectious workup for Epstein-Barr virus, cytomegalovirus, HIV, and fungal serologies was negative. A positron emission tomography (PET) scan is shown in Figure 1. The patient underwent right axillary lymph node (LN) excisional biopsy, showing sheets of large cells admixed with inflammatory cells; immunohistochemistry was diffusely positive for OCT4, SALL4, CD117, and PLAP (Figure 2).
Posterior Uveitis Associated with Large Vessel Giant Cell Arteritis
Published in Ocular Immunology and Inflammation, 2022
Nam V. Nguyen, Samendra Karkhur, Murat Yuksel, Muhammed Hassan, Muhammad Sohail Halim, Quan Dong Nguyen, Murat Hasanreisoglu
Giant cell arteritis (GCA), also called temporal arteritis, is a granulomatous vasculitis that primarily affects people over 50 years of age, with the highest incidence between 70 and 80 years.1 Although GCA is one of the most common forms of vasculitis, the pathophysiology of GCA remains poorly understood. It is likely that both genetic and environmental factors contribute to the pathogenesis of the disease.1 GCA often involves the carotid and vertebral artery branches, and autopsy studies have shown histological evidence of large-vessel involvement in 80% of cases.1,2 Moreover, GCA has also been associated with musculoskeletal manisfestations including peripheral synovitis, distal extremity swelling with or without pitting edema, tenosynovitis, and carpal tunnel syndrome.3 Temporal artery biopsy (TAB) has remained as gold standard for the diagnosis of GCA; however, TAB may be negative in 9–61% of true GCA cases.4 Therefore, clinical assessment along with imaging tests such as positron emission tomography—computerized tomography (PET-CT) can aid clinicians in better diagnosing the disease.2,5
Graphene quantum dots (GQDs) nanoarchitectonics for theranostic application in lung cancer
Published in Journal of Drug Targeting, 2022
Rahul S. Tade, Mahesh P. More, Sopan N. Nangare, Pravin O. Patil
The traditional methods including X-ray, magnetic resonance imaging (MRI), Computed tomography (CT), or positron-electron microscopy (PET) scanning are commonly used for the diagnosis of cancer. Primary screening of LC by traditional methods is dependent on the severity and phases of LC. Unfortunately, the lack of site-specific localisation or inability to detect micrometer-sized tumours becomes inconclusive in the early detection of LC. Apart from this, sputum cytology, biopsy, and bronchoscopy methods are commonly used for the diagnosis of LC. Nevertheless, due to a lack of locations and specificity, the sampling presents many limitations to detect LC at an early stage [7,8]. Interestingly, when it comes to molecular identification, the tumour microenvironment and mutation driver are a major hurdle for early detection. To construct a diagnostic model for non-small cell lung cancer (NSCLC), it is important to screen and identify driver mutations. A newly published study specified that the oncogenic drivers were found in 50% of patients with NSCLC. It concluded that the targeted therapy can advance the overall survival rate [9]. Preceding this, several researchers put forth the advanced strategy for the identification of oncogenic drivers and their role in NSCLC [10]. According to a study, SCLC is recognised as refractory cancer with less than 7% of the 5-year survival rate [11]. Several researchers discovered therapeutic targets for SCLC, such as notch ligand (DLL3) which is recognised as a target for designing new strategies for diagnosis of SCLC that documented substantial shreds of evidence [12].