Nuclear Medicine Introduction

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PowerPoint Presentation:

INTRODUCTION TO DIAGNOSTIC NUCLEAR MEDICINE

Table of Contents:

Table of Contents Objectives Introduction Types of Diagnostic Procedures Nuclear Medicine Detection Equipment Personnel Monitoring Safety Equipment Nuclear Medicine Facility Nuclear Medicine Process

PowerPoint Presentation:

Objective Upon completion of this presentation, the student will have an understanding of the procedures, equipment and processes of Diagnostic Nuclear Medicine

Nuclear Medicine?:

Nuclear Medicine? Nuclear Medicine is a medical specialty that is used to diagnose diseases in a safe and painless way. Nuclear medicine procedures permit the acquisition of medical information that may otherwise be unavailable, obtained only by surgery, or through more expensive and invasive diagnostic tests. The procedures very often identify abnormalities very early in the progression of a disease. Introduction

Nuclear Medicine?:

A diagnostic nuclear medicine study is one that is useful in the determination of the cause, nature, or manifestations of a disease or condition. It may include monitoring the progression or regression of a disease or injury in response to therapeutic regimens. A diagnostic nuclear medicine study can reveal structure or anatomy, and/or function, or physiology and metabolism. Nuclear Medicine? Introduction

Nuclear Medicine?:

The uniqueness of nuclear medicine studies lies in their ability to demonstrate function, physiology, and metabolism. Nuclear Medicine? Introduction

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Why “Nuclear” Medicine? Nuclear medicine refers to medicine (a pharmaceutical) that is attached to a small quantity of radioactive material (radioisotope). This combination is called a radiopharmaceutical. There are many different radiopharmaceuticals available to study different parts of the body; which pharmaceutical is used will depend upon the condition to be diagnosed or treated. Examples of some radioisotopes used in nuclear medicine are: Introduction

Why these isotopes?:

Why these isotopes? Short-lived in the body or have a short effective half life (T e ) : T e = (T p x T b / T p + T b ) where T, T p and T b are the physical and biological half lives of the radionuclide. No particulate emissions . A radionuclide with a particulate emission would cause poor image quality. Gamma energy should be monochromatic single peak with high photon abundance and a KeV not too high or too low. Less than 30 keV gammas would be easily attenuated by the tissue and cause a lot of electronic noise. High target to non-target ratio. An ideal radionuclide should localize more in the target organ than in the background tissue. Introduction

Types of Diagnostic Nuclear Medicine Procedures:

Imaging Procedures Most of the in-vivo* procedures involve the administration to the patient of relatively short lived radionuclides and the use of gamma cameras or other specialized instrumentation to form the images. *introduction of radioactive material into the patient's body Types of Diagnostic Nuclear Medicine Procedures

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Imaging Procedures The images from a nuclear medicine study will be either planar or tomographic images. Planar images are real-time images ( static or dynamic ) obtained as if the distribution of the radiopharmaceutical within the patient's body were from a single “plane.” The imaging devices ( e.g., scintillation camera ) are increasingly being connected to or integrated with computers, which allows manipulation of the display of imaging data. Lung scan, planar image Types of Diagnostic Procedures

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Imaging Procedures Tomographic images are those that have been computer reconstructed from linear projection data through an object. The data is acquired by placing radiation detectors 360 degrees around the patient. The reconstructed images appear as cross sectional planes or slices of the body. Diagnostic Cardiac Imaging Types of Diagnostic Procedures

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Imaging Procedures The two tomographic modalities in nuclear medicine are: Single photon emission tomography (SPECT). In SPECT, the camera ( radiation detector ) rotates and acquires data 360 o around the patient. Positron emission tomography (PET). Positron-emitting radionuclides are administered to the patient. The radiation detectors are located in a ring around the patient, and utilize coincidence detection to detect the 511 keV annihilation photons. Types of Diagnostic Procedures

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Imaging Procedures The images produced as part of a nuclear medicine test may be categorized in several different ways. Static images are made after the radiopharmaceutical has had time to reach its final biodistribution. Most imaging procedures are completed within a few hours after the administration of the radio-pharmaceutical. Some procedures require that images be acquired over periods of one day to a week or more. Types of Diagnostic Procedures

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Imaging Procedures Dynamic images consist of a series of images taken over a period of time to observe how the distribution of the radiopharmaceutical changes as the radioactive material is taken up or excreted by various organs. Measurements of the rate of handling of the radiopharmaceutical will reflect organ function. Examples of dynamic studies include the beating of the heart, emptying of stomach contents, or ventilation of the lungs. Types of Diagnostic Procedures

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Non-Imaging Procedures An example of a non-imaging procedure is the thyroid uptake study. The activity in the thyroid after a period of time is compared to the same amount of activity in a thyroid "phantom" or standard. The activity can be measured with a simple thyroid uptake probe. The number of counts from the patient's thyroid is compared to the number of counts from the standard. From this information, an estimate of the percent thyroid uptake can be made. This instrument is also used to indicate internal deposition for a bioassay. Thyroid probe Types of Diagnostic Procedures

Nuclear Medicine Detection Equipment:

Nuclear Medicine Detection Equipment Dose calibrator Camera Survey meter

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A dose calibrator is a well-type ionization chamber that is used for assaying gamma ray emitting radioactivity. Dose calibrators are used for measuring or verifying the activity of radionuclides for patient administration and technetium 99m (Tc-99m) generator eluates, shipments of radioactivity received from suppliers, and similar quantities of activity for assay. Nuclear Medicine Detection Equipment THE DOSE CALIBRATOR

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THE DOSE CALIBRATOR DETECTOR The detector element for a dose calibrator is a gas-filled ionization chamber, sealed to avoid variations in response with changes in ambient temperature and atmospheric pressure. The gas used is argon, which is pressurized to about 20 atmospheres. Nuclear Medicine Detection Equipment

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THE DOSE CALIBRATOR Different radionuclides with the same amount of activity will produce different amounts of electrical current in the ionization chamber because they emit different energy gamma rays. Ionization chambers cannot be used to identify radionuclides on the basis of gamma ray energy, like detectors with pulse-height analysis capabilities. They must be calibrated with known amounts of activity for different radionuclides. Once the calibration factors are known, then the unknown radioactivity of a given radionuclide is easily obtained by dividing the current produced in the chamber by the calibration factor for that radionuclide. Nuclear Medicine Detection Equipment

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THE DOSE CALIBRATOR Calibration factors are valid only for a given geometrical set-up, source volume, and source container. If the shape, type of source container, or volume of the source is changed appreciably, the calibration factor will change and, therefore, should be re-measured. The linearity (i.e., the relationship between current and radioactivity) and stability of a dose calibrator must be checked periodically. Nuclear Medicine Detection Equipment

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Dose calibrators utilize plug-in resistor modules, pushbuttons, or other selector mechanisms with a predetermined calibration factor to "adjust” the electrometer readout and display the activity of the selected radionuclide directly in mCi or µ Ci units. The Tc-99m source in a dose calibrator will display radioactivity at settings for other radionuclides, however these will not be correct measurements of the Tc-99m radioactivity since other calibration factors were used. THE DOSE CALIBRATOR Nuclear Medicine Detection Equipment

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Constancy means reproducibility in measuring the same source, over a period of time, with a decay correction. To measure constancy, assay a relatively long-lived source (such as Cs-137) each day prior to using the calibrator. Cs-137 (100 μCi) is strongly recommended because the 30 year half-life will assure use of the same source throughout the life of the calibrator, and is readily available. THE DOSE CALIBRATOR Nuclear Medicine Detection Equipment

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Linearity is the proportionality of the measurement result to the activity measured, as determined over the intended range of use for the dose calibrator. This test is performed by using a vial or syringe of Tc-99m wherein the activity is at least as large as the maximum activity normally assayed in a prepared radiopharmaceutical kit. A unit dose or radiopharmaceutical therapy kit could also be used for this test, as appropriate to the facility’s needs or procedures. Lineator Calicheck THE DOSE CALIBRATOR Nuclear Medicine Detection Equipment

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Accuracy means a determination of the dose calibrator’s absolute error resulting from a measurement of a suitable NIST traceable radionuclide activity. At least two sources with different principal photon energies (such as Co-57, Co-60 or Cs-137) should be used. One should have a principal photon energy between 100 keV and 500 keV. Traceable sources are available from NIST and from many radioisotope suppliers. THE DOSE CALIBRATOR Nuclear Medicine Detection Equipment

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Geometry Independence means that the indicated activity does not change with volume or configuration of the source material. This test should be done using a syringe that is normally used for injections. THE DOSE CALIBRATOR Nuclear Medicine Detection Equipment

Example Dose Calibrator Geometry Test Record:

Example Dose Calibrator Geometry Test Record Model:________________ Serial Number:_______________ Syringe: Type______ Volume_____ Date Time Volume Activity Volume (v) = Average / (Activity)(v) ______ ______ ______ ________ ______________________________ ______ ______ ______ ________ ______________________________ ______ ______ ______ ________ ______________________________ Activity Average= ________ Vial: Type______ Volume_____ Date Time Volume Activity Volume (v) = Average / (Activity)(v) ______ ______ ______ ________ ______________________________ ______ ______ ______ ________ ______________________________ ______ ______ ______ ________ ______________________________ Activity Average= ________ NOTE: You must correct activity for decay if test not completed within 10 minutes Nuclear Medicine Detection Equipment

The Gamma Camera:

The Gamma Camera Once a radiopharmaceutical has been administered, it is necessary to detect the gamma ray emissions in order to attain the functional information.  The instrument used in Nuclear Medicine for the detection of gamma rays is known as the Gamma camera.  The components making up the gamma camera are the collimator, detector crystal, photomultiplier tube array, position logic circuits, and the data analysis computer.  Nuclear Medicine Detection Equipment

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The first object that an emitted gamma photon encounters after exiting the body is the collimator. The collimator is a pattern of holes through a gamma ray absorbing material, usually lead or tungsten, that allows the projection of the gamma ray image onto the detector crystal.  The collimator allows only those gamma rays traveling along certain directions to reach the detector. This ensures that the position on the detector accurately depicts the originating location of the gamma ray. Nuclear Medicine Detection Equipment Camera Collimator

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A Thallium-activated Sodium Iodide [NaI(Tl)] detector crystal is generally used in Gamma cameras due to the crystal's optimal detection efficiency for the gamma ray energies common in Nuclear Medicine.  The gamma ray photon interacts with the detector through the Photoelectric Effect or Compton Scattering with the iodide ions of the crystal.  This interaction releases electrons that in turn interact with the crystal lattice to produce light in a process known as scintillation. A detector crystal may be circular or rectangular and is typically 3/8" thick with dimensions of 30-50 cm. Nuclear Medicine Detection Equipment Scintillation Detector

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RAD = radiation L = light flux 1 = scintillation phosphor 2 = photomultiplier 3 = light-tight enclosure 4 - 8 = photomultiplier terminals Nuclear Medicine Detection Equipment Scintillation Detector

Photomultiplier Tubes :

Photomultiplier Tubes The photomultiplier tube (PMT) is an instrument that detects and amplifies the electrons that are produced by the photocathode.  The photocathode, when stimulated by light photons, ejects electrons. The PMT is attached to the back of the crystal.    Only a very small amount of light is given off from the scintillation detector. Only one electron is generated for every 7 to 10 photons incident on the photocathode.  This electron is focused on a dynode that absorbs it and re-emits many more electrons (usually 6 to 10).  These new electrons are focused on the next dynode and the process is repeated over and over in an array of dynodes.  At the base of the PMT is an anode that attracts the final large cluster of electrons and converts them into an electrical pulse. Nuclear Medicine Detection Equipment Dynode

Position Circuitry :

Position Circuitry The position logic circuits immediately follow the photomultiplier tube array, where they receive the electrical impulses from the tubes in the summing matrix circuit (SMC).  This allows the position circuits to determine where each scintillation event occurred in the detector crystal. Nuclear Medicine Detection Equipment

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Finally, a processing computer is used to deal with the incoming projection data and processes it into a readable image of the 3D spatial distribution of activity within the patient.  The computer may use various methods to reconstruct an image, such as filtered back projection or iterative reconstruction. Nuclear Medicine Detection Equipment Data Analysis Computer

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PET/CT scanner Dual head scanner Single head SPECT scanner Nuclear Medicine Detection Equipment

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Survey Meters The Geiger Mueller (GM) detector is the most common instrument used for contamination surveys in a nuclear medicine department. It is a gas-filled detector that is very sensitive to small amounts of radioactivity. GM detectors are incapable of differentiating types of radiation like gamma rays and beta particles, and incapable of energy discrimination. However they are excellent in detecting contamination and are also used in certain types of wipe test counters. Nuclear Medicine Detection Equipment

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Regulations require exposure rate surveys to be made in areas of the nuclear medicine department and are best performed using an ionization chamber that will read out directly in units of exposure (Roentgen or coulombs/kg). Facilities use GM detectors for this purpose, even though most GM detectors are not designed to measure exposure or exposure rate except under certain conditions. GM instruments are usually calibrated with cesium 137 (Cs-137), that emits a 662 keV gamma ray (recall that Tc-99m emits a 140 keV gamma ray). Still, making exposure or exposure rate measurements for Tc-99m with a GM instrument calibrated with Cs-137 is acceptable to regulatory agencies. Nuclear Medicine Detection Equipment Survey Meters

Personnel Monitoring:

Personnel Monitoring Personnel monitoring for radiation workers is a process of estimating an individual’s occupational dose. It is also used to indicate: changes in the work activity of an individual or a department the effectiveness of a radiation safety program in keeping radiation doses ALARA (As Low As Reasonably Achievable).

Personnel Monitoring:

Personnel Monitoring Various devices such as a film badge, a thermoluminescent dosimeter (TLD), an optically stimulated luminescence (OSL) detector, or a ring badge are used to monitor external exposures. Bioassay techniques are used to monitor internal exposures by assessing the internal deposition of a radionuclide. Radioiodines and tritium are the most frequently utilized isotopes that are either inhaled, ingested, or absorbed.

Safety Equipment:

Safety Equipment L- blocks Syringe shields Container shields Sharps containers Latex gloves Ammo boxes

Lead Blocks (L-blocks):

Lead Blocks (L-blocks) Nuclear medicine makes extensive use of shielding. Work is performed behind an L-block, a physical barrier consisting of a lead front shield and base, with leaded glass for viewing the work area. L-blocks are designed based upon the highest energy and amount of radioactivity used in the intended work area. Lead bricks may also be added for partial barriers. Safety equipment

Syringe Shields:

Syringe Shields Syringe shields are very effective in reducing exposure to the occupational worker’s hands and fingers during patient injection. Syringe shields should be thick enough to protect the occupational worker from the highest photon energy in use. Safety equipment

Container Shields:

Container Shields Container shields are also effective at reducing dose exposure to the occupational worker during manipulation of multi-use vials. Safety equipment

Sharps Containers:

Sharps Containers All biological hazard material must be properly stored and disposed. Sharps containers are commonly used to store needles, scalpels, IV tubing and other equipment containing biological fluids. If radioactive material is present, these containers may be encased in lead and appropriately labeled. Safety equipment

Latex Gloves:

Latex Gloves Gloves are primarily used in nuclear medicine to protect the occupational worker from biological hazards and radiation contamination. Safety equipment

Transportation Cases :

Transportation Cases Radiopharmaceutical doses (single unit doses) are delivered to administer at a predetermined time. The short half-life of the nuclides requires that an efficient method is used to safely transport the doses to licensees. Radiopharmacies use dedicated vehicles to transport the doses in specially designed DOT approved transport containers ("suitcases" or “ammo boxes”) to minimize exposure to occupational workers and the public. Safety equipment

Nuclear Medicine Facility:

Nuclear Medicine Facility

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Nuclear Medicine Facility Hot Lab Gamma camera Treadmill

Posting:

Posting Facilities possessing and using radioactive material must have proper posting. Some of the postings include: Caution Radioactive Materials Emergency Notification Information Notice to Employees Nuclear Medicine Facility

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Nuclear Medicine Facility

Nuclear Medicine Process:

Nuclear Medicine Process Receive package from nuclear pharmacy Assay dose Administer dose Image patient Interpret image

Receive package from nuclear pharmacy:

Receive package from nuclear pharmacy Typically, radioactive materials are delivered daily to the facility by a nuclear pharmacy prior to normal business hours. The nuclear medicine technologist performs some quality assurance and prepares for the day’s activities. Nuclear Medicine Process

Assay Dose:

Assay Dose Doses are assayed prior to patient injection to verify that the activity of the delivered unit dose matches the prescribed dose. Nuclear Medicine Process

Administer Dose:

Administer Dose Radiopharmaceuticals are introduced into the patients body by injection, ingestion or inhalation. The pharmaceutical part of the radiopharmaceutical is designed to go to a specific place in the body where there could be disease or an abnormality. The radioactive part of the radiopharmaceutical emits gamma radiation and is detected using a gamma camera. Nuclear Medicine Process

Image Patient:

Gamma cameras allow the physician to determine what is occurring inside the body. The patient is asked to lie down or sit, and then the gamma camera is positioned a few inches away from the patient’s body. It then detects the radiation emitted from the patient’s body, and acquires the images through digital processing. Nuclear medicine determines the cause of a medical problem based on metabolic function, in contrast to other diagnostic tests that determine the presence of disease based on anatomy or structural appearance. Image Patient Nuclear Medicine Process

Interpretation of Image:

Interpretation of Image Authorized Users are specially trained and certified to interpret the results of the scan. Other personnel, such as certified nuclear medicine technologists, administer the radiopharmaceuticals and perform the scan. Nuclear Medicine Process

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Nuclear Medicine Applications Nuclear medicine studies can help diagnose and treat many diseases. New technologies continue to evolve, expanding the capability of nuclear medicine to improve patient care.

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