Name: pet scans and how they work
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 29 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Chemistry

Matter and Its Interactions

CHEM1.PS1.10

Positron Emission Tomography

Positron emission tomography, or PET, is a radiotracer-based medical imaging technique commonly used for tumor detection, determining the extent of metastases, evaluating heart ailments like impaired blood supply, and studying&#160; neural activity in the brain.
To perform a PET scan, the patient is most often injected with a radioactive tracer, a biological molecule bound to a positron-emitting isotope such as carbon-11, oxygen-15, or fluorine-18.
Once in the body, these radiotracers accumulate inside the tissue or the cells where they have higher affinity. For instance, fluorodeoxyglucose or FDG accumulates more in tumors due to their higher metabolic activity.
The unstable radioactive fluorine decays, emitting positrons - the positively charged antiparticle of electrons. The positrons combine with nearby electrons resulting in an annihilation reaction and emit two photons of 511 keV energy in opposite directions.
The PET detector collects millions of these annihilation events and, using complex computing algorithms, reconstructs the images of tracer distribution in the area under study.

positron emission tomography

Positron emission tomography (PET) is a medical imaging technique involving radiopharmaceuticals &#8212; substances that emit short-lived radiation. 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.
One of the main requirements of a PET scan is a positron-emitting radioisotope, which is produced in a cyclotron and then attached to a substance used by the part of the body being investigated. This &#34;tagged&#34; compound, or radiotracer, is then put into the patient (injected via IV or breathed in as a gas), and how the tissue uses it reveals how that organ or other area of the body functions. For example, F-18 is produced by proton bombardment of 18O and incorporated into a glucose analog called fludeoxyglucose (FDG). How the body uses FDG provides critical diagnostic information. For example, since cancers use glucose differently than normal tissues, FDG can reveal cancers. The 18F emits positrons that interact with nearby electrons, producing a burst of gamma radiation. This energy is detected by the scanner and converted into a detailed, three-dimensional color image that shows how that part of the patient&#39;s body functions. Different levels of gamma radiation produce different amounts of brightness and colors in the image, which a radiologist can then interpret to reveal what is going on. For instance, a radioactive form of iodine can be used to monitor the thyroid and radioactive gallium can be used for cancer imaging.
The main advantage is that PET can illustrate the physiologic activity&#8212;including nutrient metabolism and blood flow&#8212;of the targeted organ or organs. In contrast, CT and MRI scans can only show static images. PET is widely used to diagnose a multitude of conditions, such as heart disease, the spread of cancer, certain forms of infection, brain abnormalities, bone disease, and thyroid disease. PET can also locate regions in the brain that become active when a person carries out specific activities, such as speaking, closing his or her eyes, etc. PET scans are now usually performed in conjunction with a computed tomography or magnetic resonance imaging scan for better data visualization and interpretation.
This content is derived from <a href="https://openstax.org/books/anatomy-and-physiology/pages/1-7-medical-imaging">Openstax, Anatomy and Physiology, Section 1.7: Medical Imaging</a> and <a href="https://openstax.org/books/chemistry-2e/pages/21-3-radioactive-decay">Openstax, Chemistry 2e, Section 21.3: Radioactive Decay</a> and <a href="https://openstax.org/books/physics/pages/22-5-medical-applications-of-radioactivity-diagnostic-imaging-and-radiation">Openstax, Physics, Section 22.5: Medical Applications of Radioactivity: Diagnostic Imaging and Radiation</a>

Positron emission tomography (PET) is a medical imaging technique involving radiopharmaceuticals &#8212; substances that emit short-lived radiation. ...

Education

JoVE Core

Anatomy and Physiology

Unit 1

Diagnostic Imaging Techniques

KEY TERMS AND CONCEPTS

pet scans and how they work

PET scans use radiopharmaceuticals to show how the body is working. PET, or positron emission tomography, is a medical imaging method that depends on short-lived radiation from these compounds. It gives doctors a way to see tissue activity instead of only body structure.

A PET scan starts with a positron-emitting radioisotope. This isotope is made in a cyclotron and then attached to a substance used by the body part being studied. The tagged compound is called a radiotracer. It can be given by IV injection or breathed in as a gas.

One common example uses F-18. It is produced by proton bombardment of oxygen-18 and added to a glucose analog called fludeoxyglucose, or FDG. The way the body uses FDG gives important diagnostic information. Because cancer cells often use glucose differently from normal tissue, FDG can help reveal cancers.

After the radiotracer is in the body, the F-18 emits positrons. These positrons interact with nearby electrons and create a burst of gamma radiation. The scanner detects this energy and turns it into a detailed, three-dimensional color image. Different levels of gamma radiation appear as different brightness and colors, and a radiologist interprets the image to understand what is happening in the body.

PET can use different tagged substances for different organs. A radioactive form of iodine can monitor the thyroid. Radioactive gallium can be used for cancer imaging. The main advantage of PET is that it shows physiologic activity, including nutrient metabolism and blood flow, in the targeted organ or organs.

This makes PET different from CT and MRI scans, which show static images. PET is widely used to diagnose heart disease, the spread of cancer, certain infections, brain abnormalities, bone disease, and thyroid disease. It can also show which brain regions become active during activities such as speaking or closing the eyes. PET scans are now often done with CT or MRI for better visualization and interpretation.

PET Scans and How They Work

x-ray imaging

X-Ray Use in Medical Diagnosis

X-rays are a standard tool in medical diagnosis. They help doctors see bones, teeth, and some soft tissues without surgery. The first X-ray image showed Wilhelm Röntgen’s wife’s hand, and it opened a new way to look inside the body. Wilhelm Röntgen, a German physicist, discovered X-rays in 1895 while studying electrical current. He found that an invisible ray could pass through flesh but leave the bones outlined on a screen coated with a metal compound. His work led to the first durable record...

computed tomography

CT Scans for Body Slices

Computed tomography, or CT, creates detailed body slices using X-rays and computers. It is a non-invasive imaging method that helps reveal fine details inside the body. The word tomography means imaging by sections. CT was developed in the 1970s. It works by measuring how X-rays pass through the body and are absorbed or reflected at different levels. During a scan, the patient lies on a motorized platform while a computerized axial tomography, or CAT, scanner rotates 360 degrees around the...

magnetic resonance imaging

MRI Scans: How Body Signals Are Formed

Magnetic resonance imaging, or MRI, is a noninvasive way to create detailed medical images. It uses strong magnetic fields and radio waves. When the body is exposed to them, it can emit radio signals that are used to build the image. MRI became especially important after researchers saw that cancerous tissue gave off signals different from normal tissue. Raymond Damadian identified this difference in 1970 and later applied for a patent for the first MRI scanner used in clinical care. Early...

PET scans use radiopharmaceuticals to show how the body is working. PET, or positron emission tomography, is a medical imaging method that depends on short-lived radiation from these compounds. It gives doctors a way to see tissue activity instead of only body structure. A PET scan starts with a positron-emitting radioisotope. This isotope is made in a cyclotron and then attached to a substance used by the body part being studied. The tagged compound is called a radiotracer. It can be given by...

ultrasonography

Ultrasonography in Medical Imaging

Ultrasonography in medical imaging uses high-frequency sound waves to create images of internal body structures. It is a safe, non-invasive procedure. It does not use ionizing radiation, which is one reason it is widely used in medicine. During an ultrasound exam, a handheld transducer is placed on the skin. A transducer is the device that sends sound waves into the body. When the waves hit different tissues, they bounce back as echoes. The transducer catches those echoes and sends them to a...

overview of microscopy techniques

How Microscopes Reach Higher Resolution

Microscopes have become more powerful by improving magnification, resolution, and contrast. Early pioneers such as van Leeuwenhoek used far simpler instruments than the microscopes used today. In 1830, Joseph Jackson Lister created an essentially modern light microscope. Later advances in the 20th century added nonvisible light, including fluorescence microscopy and electron microscopy. Many microscopes used in schools and labs are light microscopes. These instruments use light to make images...

key terms and concepts

Learn how PET scans use radiotracers, gamma radiation, and color images to show organ function, detect cancer, and track brain activity.

PET Scans and How They Work | JoVE K12

anatomy and physiology

JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

Texas Essential Knowledge and Skills

CHEM.14

CHEM.14.C

Next Generation Science Standards

Physical Science

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Waves and Their Applications in Technologies for Information Transfer

HS-PS4-5

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South Carolina College and Career Ready Science Standards

Biology

Biological Evolution: Unity and Diversity

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New York State Science Learning Standards

HS. Waves and Electromagnetic Radiation

HS-PS4-5.

formula-mass-and-mole-concepts-of-compounds

Formula Mass and Mole Concepts of Compounds

Formula Mass of Covalent Compounds

Chemical formulas represent the elemental makeup of substances. For covalent compounds, the formula represents the ...

Expressing Solution Concentration

A solute is a component of a solution that is typically present at a much lower concentration than the solvent. Solute concentrations are often described ...

determining-the-mass-percent-composition-in-an-aqueous-solution

Determining the Mass Percent Composition in an Aqueous Solution

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
Determining the composition of a solution is an important ...

Solutions and Concentrations

Source: Laboratory of Dr. Michael Evans &#8212; Georgia Institute of Technology
A solution is a homogeneous mixture containing some components in small ...

Reaction Stoichiometry

A balanced chemical equation provides a great deal of information in a very succinct format. Chemical formulas provide the identities of the reactants and ...

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Stoichiometry, Product Yield, and Limiting Reactants

Chemical equations represent how a chemical reaction proceeds from reactants to products through physical or chemical change using chemical formulas.
...

Understand and be prepared to use values specific to chemical processes: the mole, molar mass, molarity, and percent composition. EXPLANATION: During the early and mid-1800s, a tremendous amount of early research poured into building an understanding of the way that atoms combine. This work required analysis of the percent composition of different substances. Joseph Proust's work with tin oxides led him to publish his law of definite proportions noting that a given pure substance will have a constant ratio for the combination of elements making up the substance. Building on Proust's work, John Dalton published his law of multiple proportions and atomic theory noting that multiple patterns exist for the way that atoms combine, yet the combining atoms are invariable. Meanwhile Amedeo Avogadro hypothesizes that given equal pressures and temperatures, two equal volumes of gas will contain equal numbers of atoms. Acknowledging that the exact number of atoms was unknown in these gaseous volumes, the Latin word "mole" was used. "Mole" translates to "lump" recognizing the ambiguous quantity of gas. A number of attempts have been undertaken historically to quantify the mole. Robert Millikan's oil drop experiment revealed the change of a single electron, which could then be divided into Faraday's Constant for the charge of a mole of electrons. Dividing the charge of a mole of electrons by the charge of a single electron yields the number of electrons in a mole, $6.022\times10^{\wedge}23$. Students should be familiar with how to translate between the given quantities. Student's first use atomism/Dalton's atomic theory in third grade noting that matter is made up of particles too small to be seen. This the first time where students will undertake the process of counting these invisible particles. Electrolysis of water provides a tangible experience to demonstrate the constituent parts of water, though the definite proportions of water may not be easily seen due to the solubility of the gasses produced. The concept of relative mass can be explored by comparing small groups of like items. For example, relative masses of beans can be compared with pinto, white, and black beans. If bags are created with equal numbers of like beans, students can develop a concept of why the smallest bean will have a relative mass of 1, analogous to hydrogen.

CHEM1.PS1.1

Chemical Equations

Chemical equations represent the identities and relative quantities of substances involved in a chemical reaction. The substances undergoing reaction are ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Chemical Reactions

A chemical reaction is a process by which the bonds in the atoms of substances are rearranged to generate new substances. Matter cannot be created or ...

Balancing Redox Equations

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Demonstrate that atoms, and therefore mass, are conserved during a chemical reaction by balancing chemical reactions. EXPLANATION: Standard 7.PS1.4 explores the idea that chemical reactions are rearrangements of atoms, and students undertake the process of balancing chemical reactions with that standard in seventh grade. The introduction of molar masses in high school makes an explicit connection between the number of atoms, as previously investigated, and the actual masses of the atoms, permitting the collection of more concrete evidence for the conservation of mass in chemical reactions.

CHEM1.PS1.2

Reaction Yield

The theoretical yield of a reaction is the amount of product estimated to form based on the stoichiometry of the balanced chemical equation. The ...

A balanced chemical equation provides the information of chemical formulas of the reactants and products involved in the chemical change. A ...

Limiting Reactant

The relative amounts of reactants and products represented in a balanced chemical equation are often referred to as stoichiometric amounts. However, in ...

chemical-equilibria-systematic-approach-to-equilibrium-calculations

Chemical Equilibria: Systematic Approach to Equilibrium Calculations

In systems with multiple equilibria, the equilibrium calculations use a systematic approach involving a series of steps to make sure there are as many ...

Perform stoichiometric calculations involving the following relationships: mole- mole; mass-mass; mole-mass; mole- particle; and mass- particle. Show a qualitative understanding of the phenomenon of percent yield, limiting, and excess reagents in a chemical reaction through pictorial and conceptual examples. (states of matter liquid and solid; excluding volume of gasses). EXPLANATION: This standard builds on the idea that balancing chemical reactions provides evidence for conservation of mass and that the behavior of atoms follows predictable patterns. Students now have the opportunity to utilize this understanding as they perform and evaluate chemical reactions. (The concepts of limiting reagent and percent yield are presented; however, students are not expected to determine these values algebraically. Use of molar volume in stoichiometric processes is beyond the scope of this standard.)

CHEM1.PS1.3

Predicting Reaction Outcomes

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Introduction to Chemical Reactions

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Chemical Reactions in Aqueous Solutions

Chemical substances interact in many different ways. Certain chemical reactions exhibit common patterns of reactivity. Due to the vast number of chemical ...

Precipitation Reactions

In a precipitation reaction, aqueous solutions of soluble salts react to give an insoluble ionic compound &#x2013; the precipitate. The reaction occurs ...

Oxidation-Reduction Reactions

Oxidation&ndash;Reduction Reactions

Earth&rsquo;s atmosphere contains about 20% molecular oxygen, O2, a chemically reactive gas that plays an essential ...

Oxidation Numbers

In redox reactions, the transfer of electrons occurs between reacting species. Electron transfer is described by a hypothetical number called the ...

Acids, Bases and Neutralization Reactions

An acid-base reaction is one in which a hydrogen ion, H+, is transferred from one chemical species to another. Such reactions are of central importance to ...

Synthesis and Decomposition Reactions

Synthesis and decomposition are two types of redox reactions. Synthesis means to make something, whereas decomposition means to break something. The ...

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Types of Chemical Reactions: Exchange and Reversible

An exchange reaction is a chemical reaction in which both synthesis and decomposition occur, chemical bonds are both formed and broken, and chemical ...

Use the reactants in a chemical reaction to predict the products and identify reaction classes (synthesis, decomposition, combustion, single replacement, double replacement). EXPLANATION: Chemical reactions are rearrangements of atoms that follow predicable patterns. There are patterns both at the macroscopic level in the behavior of some of the reaction classes, as well as patterns in the rearrangements of the atoms underlying the reaction. Students should be able to predict the products of the reactions, which also requires the ability to recognize the general patterns for each type of reaction.

CHEM1.PS1.4

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Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

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Basic Postulates of Kinetic Molecular Theory: Particle Size, Energy, and Collision

The ideal-gas equation, which is empirical, describes the behavior of gases by establishing relationships between their macroscopic properties. For ...

Ideal Gas Law

Derivation of the Ideal Gas Law
Gases are a fundamental state of matter. A gas is a collection of molecules that have a significant distance between their ...

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Gas Laws: Boyle's, Gay-Lussac, Charles', Avogadro's, and Ideal Gas Law

Through experiments, scientists established the mathematical relationships between pairs of variables, such as pressure and temperature, pressure and ...

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Kinetic Molecular Theory: Molecular Velocities, Temperature, and Kinetic Energy

The kinetic molecular theory qualitatively explains the behaviors described by the various gas laws. The postulates of this theory may be applied in a ...

Kinetic Theory of an Ideal Gas

A mole is defined as the amount of any substance that contains as many molecules as there are atoms in exactly 12 grams of carbon-12. An Italian scientist ...

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Applications of the Ideal Gas Law: Molar Mass, Density, and Volume

The volume occupied by one mole of a substance is its molar volume. The ideal gas law, PV = nRT, &nbsp;suggests that the volume of a given quantity of gas ...

Conduct investigations to explore and characterize the behavior of gasses (pressure, volume, and temperature), develop models to represent this behavior, and construct arguments to explain this behavior. Evaluate the relationship (qualitative and quantitatively) at STP between pressure and volume (Boyle's Law), temperature and volume (Charles' Law), temperature and pressure (Gay-Lussac Law) and moles and volume (Avogadro's Law), and evaluate and explain these relationships with respect to kinetic molecular theory. Be able to understand, establish, and predict the relationships between volume, temperature, and pressure using combined gas law both qualitatively and quantitatively. EXPLANATION: When exploring the behavior of gasses, it is important to consider experimental design. Experiments used to show the relationships between these sets of variables should include one independent and one dependent variable. Other variables should be held constant. Pressure should serve as the dependent variable because it cannot be manipulated directly. Avogadro's Law can be used to relate the amount of gas in two different containers in lieu of knowing actual number of gas particles in an individual container. Individual demonstrations can be performed to explore each of the different gas laws.

CHEM1.PS1.5

Ideal Gas Equation

The ideal gas equation is an equation of state that relates the state variables pressure, volume, temperature, and the number of moles of a hypothetical ...

Source: Laboratory of Dr. Andreas Z&#252;ttel - Swiss Federal Laboratories for Materials Science and Technology
The ideal gas law describes the behavior ...

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Real Gases: Effects of Intermolecular Forces and Molecular Volume Deriving Van der Waals Equation

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chemical-stoichiometry-gases-using-ideal-gas-law-to-determine

Chemical Stoichiometry and Gases: Using Ideal Gas Law to Determine Moles

Chemical stoichiometry describes the quantitative relationships between reactants and products in chemical reactions.

In addition to measuring quantities ...

pV-Diagrams

The pV diagram, which is a graph of pressure versus volume of the gas under study, is helpful in describing certain aspects of the substance. When the ...

Use the ideal gas law, PV = nRT, to algebraically evaluate the relationship among the number of moles, volume, pressure, and temperature for ideal gases. EXPLANATION: If students have collected data during investigations for CHEM1.PS1.5, these data can then be used to linearize. With pressure assigned as the dependent variable and plotted against (moles) (temperature)/volume, the slope of the graph will be the gas constant, yielding the ideal gas law. After developing the mathematical model, this model can be used to make predictions for other systems.

CHEM1.PS1.6

Separation of Mixtures via Precipitation

Source: Laboratory of Dr. Ana J. Garc&#237;a-S&#225;ez &#8212; University of T&#252;bingen
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Distillation: Vapor&ndash;Liquid Equilibria

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Filtration

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Centrifugation

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...

Sublimation

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Recrystallization: Solid&ndash;Solution Equilibria

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Precipitation and Co-precipitation

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Extraction: Effects of pH

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Extraction: Advanced Methods

Metal ions can be separated by complexation with organic ligands to form uncharged chelates.
The chelating agent must contain hydrophobic groups and ...

Chromatography: Introduction

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Dialysis

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Analyze solutions to identify solutes and solvents, quantitatively analyze concentrations (molarity, percent composition, and ppm), and perform separation methods such as evaporation, distillation, and/or chromatography and show conceptual understanding of distillation. Construct argument to justify the use of certain separation methods under different conditions. EXPLANATION: In seventh grade, students developed an understanding that chemical and physical properties of a sample of matter could be used to identify a substance. Building on this understanding, students now explore the use of these physical and chemical properties to separate mixtures. Analysis of the substances is performed to aid in further discussion and facilitate further quantitative analysis.

CHEM1.PS1.7

Acids and bases play several important roles in biology. The pH of a biological system can significantly impact the function of biological molecules, ...

Bronsted-Lowry Acids and Bases

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Lewis Acids and Bases

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acidbase-strengths-and-dissociation-constants

Acid/Base Strengths and Dissociation Constants

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Identify acids and bases as a special class of compounds with a specific set of properties. EXPLANATION: The concept of pH is first introduced in seventh grade as a chemical property of matter. Students should be introduced to multiple explanations of acid and base behavior to permit classification of common substances (e.g. baking soda, ammonia, carbon dioxide) as acids or bases. To further develop discussions of solubility, qualitative discussions of the differences between strong and weak acids are appropriate. (Calculations of pH or ion concentrations are beyond the scope of this standard. Discussions of pOH are beyond the scope of this standard. Conjugate pairs are beyond the scope of this standard.)

CHEM1.PS1.8

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Radioactivity and Nuclear Equations

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Isotopes and Radioisotopes

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Nuclear Stability

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Draw models (qualitative models such as picture or diagrams to demonstrate understanding of radioactive stability and decay.) Understand and differentiate between fission and fusion reactions. Use models (graphs or tables) to explain the concept of half-life and its use in determining the age of materials (such as radiometric dating). EXPLANATION: To build an understanding of nuclear processes, students should attribute the existence of the nucleus and nuclear stability to neutrons and the strong nuclear force. The process of fusion is facilitated when two nuclei are forced near one another to the point where strong nuclear forces exceed repulsive electromagnetic forces. Due the random movements of nucleons, decay processes are also random but can be charted exhibiting consistent patterns. These patterns are useful in radiometric dating on varying scales.

CHEM1.PS1.9

PET Scans and How They Work

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