Positron emission tomography (PET)

Positron emission tomography (PET) is a medical imaging technique involving the use of so-called radiopharmaceuticals, substances that emit radiation that is short-lived and therefore relatively safe to administer to the body. Although the first PET scanner was introduced in 1961, it took 15 more years before radiopharmaceuticals were combined with the technique and revolutionized its potential. …

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Ultrasonography is an imaging technique that uses the transmission of high-frequency sound waves into the body to generate an echo signal that is converted by a computer into a real-time image of anatomy and physiology. Ultrasonography is the least invasive of all imaging techniques, and it is therefore used more freely in sensitive situations such as …

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Computed tomography (CT scan)

Tomography refers to imaging by sections. Computed tomography (CT scan) is a noninvasive imaging technique that uses computers to analyze several cross-sectional X-rays in order to reveal minute details about structures in the body. The technique was invented in the 1970s and is based on the principle that, as X-rays pass through the body, they are absorbed …

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Magnetic resonance imaging (MRI)

Magnetic resonance imaging (MRI) is a noninvasive medical imaging technique based on a phenomenon of nuclear physics discovered in the 1930s, in which matter exposed to magnetic fields and radio waves was found to emit radio signals. In 1970, a physician and researcher named Raymond Damadian noticed that malignant (cancerous) tissue gave off different signals than …

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Methotrexate is a chemotherapy agent and immune system suppressant of a type known as an antimetabolite that interferes with the synthesis of folic acid, an essential component of cells. It is used to treat malignant tumors, leukemia, rheumatoid arthritis, and psoriasis.


Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment.


Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. There are three main classifications of anaphylaxis. Anaphylactic shock is associated with systemic vasodilation that causes low blood pressure which is by definition 30% lower than the person’s baseline or below standard values. Biphasic anaphylaxis is the recurrence of symptoms within 1–72 hours …

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Epidemiology is the study and analysis of the emergence, distribution (who, when, and where), patterns, determinants and control of disease, disability, and death among defined populations. The field of epidemiology combines the sciences of biology, clinical medicine, sociology, mathematics, and ecology to understand patterns of health problems and improve human health across the globe.


A disease is an abnormal condition of a living organism, caused by organic or functional alterations, which compromise its health. In many cases, terms such as disease, disorder, morbidity, sickness and illness are used interchangeably.


Medicine is the science that studies the diseases of the human body in order to guarantee people’s health, in particular establishing the diagnosis, prognosis, treatment, and prevention of disease, as well as different ways of alleviating the suffering of the sick (even those who cannot more heal). Medical specialization Medicine is divided into internal medicine and …

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