CLUSTER 5
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Questions and Answers

What is the primary delivery method for the tracer used in nuclear medicine procedures?

  • Topical application
  • Injection (correct)
  • Oral ingestion
  • Inhalation

    • Which of the following radioisotopes is most commonly used for diagnosing cancer and infections?

  • I-131
  • I-123
  • Tc-99m (correct)
  • Co-60

    • In the context of nuclear medicine, what does the term 'localization' refer to?

  • The radioactive decay of the tracer over time
  • The accumulation of the tracer in specific organs or tissues (correct)
  • The process of administering medication through a vein
  • The use of radionuclides for therapeutic purposes

    • What is the main role of a nuclear medicine technologist?

    <p>To perform tests and operate nuclear medicine equipment</p> Signup and view all the answers

    Which type of radiation is primarily emitted by radionuclides used in diagnostic procedures?

    <p>Gamma radiation</p> Signup and view all the answers

    What is a key factor affecting radionuclide dosage in therapeutic procedures?

    <p>Patient weight and body surface area</p> Signup and view all the answers

    What is the fundamental building block of matter as described in nuclear physics?

    <p>Atom</p> Signup and view all the answers

    Which radioisotope is specifically noted for its use in targeted radiotherapy?

    <p>Zevalin (Y-90)</p> Signup and view all the answers

    Cyclotron production of isotopes is primarily used to create which type of radioactive materials?

    <p>Short-lived isotopes for diagnostic imaging</p> Signup and view all the answers

    What does the term 'emission' refer to in the context of nuclear medicine?

    <p>The gamma ray emissions from the tracer in the body</p> Signup and view all the answers

    What is the process by which an unstable atom emits radiation to become more stable?

    <p>Radioactive decay</p> Signup and view all the answers

    Which decay mode involves the emission of a helium nucleus?

    <p>Alpha decay</p> Signup and view all the answers

    What is the significance of half-life in radioactive decay?

    <p>Time required for half of the radioactivity to decay</p> Signup and view all the answers

    What type of transition involves the nucleus emitting a gamma photon?

    <p>Isomeric transition</p> Signup and view all the answers

    Which decay mode is characterized by a neutron transforming into a proton?

    <p>Beta minus decay</p> Signup and view all the answers

    What is a key characteristic of alpha particles?

    <p>Most ionizing and least penetrating</p> Signup and view all the answers

    What does internal conversion in decay indicate?

    <p>Transferring excess energy to an outer shell electron</p> Signup and view all the answers

    During which decay mode does the atomic number remain unchanged?

    <p>Gamma decay</p> Signup and view all the answers

    In biological half-life, what is primarily being measured?

    <p>Time required for a radioactive substance to reduce by half in a biological system</p> Signup and view all the answers

    What occurs during gamma decay?

    <p>Excess energy is released as gamma rays</p> Signup and view all the answers

    What is the primary purpose of Bexxar Therapy?

    <p>Treatment of certain non-Hodgkin’s lymphomas</p> Signup and view all the answers

    Which therapeutic pharmaceutical is indicated for the treatment of hyperthyroidism?

    <p>Iodine 131 Nal</p> Signup and view all the answers

    What characteristic of a radiopharmaceutical is essential for effective PET imaging?

    <p>Emits positron particles</p> Signup and view all the answers

    Which factor is not typically considered in determining radionuclide dosage for therapeutic applications?

    <p>Dose administered in diagnostic imaging</p> Signup and view all the answers

    What is the main function of a cyclotron in radionuclide production?

    <p>To accelerate charged particles</p> Signup and view all the answers

    Which of the following describes the ideal characteristics of a radionuclide for diagnostic imaging?

    <p>Short physical half-life and suitable energy emissions</p> Signup and view all the answers

    Which radionuclide is most commonly used in clinical applications due to its qualities?

    <p>Tc-99m</p> Signup and view all the answers

    Which of the following methods is not typically used for elution in radionuclide generation?

    <p>Aeration</p> Signup and view all the answers

    What is a significant advantage of using radionuclide generators?

    <p>They provide a continuous supply of short-lived isotopes</p> Signup and view all the answers

    What principle does the radioactive decay of parent radionuclides in generators rely on?

    <p>Isobaric transition</p> Signup and view all the answers

    Which form of radiopharmaceutical is used in renal dynamic scintigraphy?

    <p>Tc-99m pertechnetate</p> Signup and view all the answers

    Which element is a parent radionuclide that decays into Tc-99m?

    <p>Mo-99</p> Signup and view all the answers

    What is a unique emission characteristic of Tc-99m compared to its parent Tc-99?

    <p>Emits a monoenergetic gamma photon</p> Signup and view all the answers

    Which of the following distinguishes therapeutic radiopharmaceuticals from diagnostic ones?

    <p>They are designed to deliver higher doses to targeted tissues</p> Signup and view all the answers

    Which process is typically used to prepare radpharmaceuticals in nuclear medicine?

    <p>Heating in a water bath</p> Signup and view all the answers

    What is the effect of a narrow beam width on spatial resolution?

    <p>It provides better spatial resolution</p> Signup and view all the answers

    Which component is NOT part of spatial resolution?

    <p>Temporal Resolution</p> Signup and view all the answers

    How does the temporal resolution of an imaging system change with an increased frame rate?

    <p>It improves</p> Signup and view all the answers

    What is the role of backing or damping materials in ultrasonic imaging?

    <p>To reduce unwanted vibrations</p> Signup and view all the answers

    What does the Doppler effect describe in ultrasound imaging?

    <p>Change in echo frequency due to movement</p> Signup and view all the answers

    Which statement about thick physical housing in ultrasound systems is true?

    <p>It acts as an acoustic insulator</p> Signup and view all the answers

    The ability of an imaging system to display two structures close together as separate images is referred to as:

    <p>Spatial resolution</p> Signup and view all the answers

    Which type of resolution is primarily concerned with differentiating between gray shades in body tissues?

    <p>Contrast resolution</p> Signup and view all the answers

    What is the effect of high-frequency ultrasound on spatial resolution?

    <p>It enhances resolution</p> Signup and view all the answers

    What does a two-dimensional image represent in terms of slice thickness?

    <p>A single dimension of a three-dimensional volume</p> Signup and view all the answers

    What is the main cause of edge shadowing in ultrasound imaging?

    <p>Highly attenuating structures</p> Signup and view all the answers

    What does anechoic mean in the context of ultrasound imaging?

    <p>Absence of echoes</p> Signup and view all the answers

    How does beam width artifact affect ultrasound imaging?

    <p>Causes loss of detail at the edge of structures</p> Signup and view all the answers

    What is the primary factor that influences slice thickness artifact?

    <p>Beam angulation</p> Signup and view all the answers

    What effect do side lobes have on ultrasound imaging?

    <p>Cause artifacts leading to false diagnoses</p> Signup and view all the answers

    What does the Ankle/Brachial Index (ABI) measure?

    <p>Ratio of ankle pressure to brachial pressure</p> Signup and view all the answers

    Which of the following describes axial resolution in ultrasound?

    <p>Ability to distinguish two structures along a path parallel to the sound beam</p> Signup and view all the answers

    What is the function of color flow Doppler in ultrasound imaging?

    <p>Quantify velocity of blood flow by coloring pixels</p> Signup and view all the answers

    What is the main purpose of a converging collimator?

    <p>To provide some magnification</p> Signup and view all the answers

    Which component of the gamma camera is responsible for converting light into electrical pulses?

    <p>Photomultiplier tube (PMT)</p> Signup and view all the answers

    How do diverging collimators differ from converging collimators?

    <p>Their holes are angled opposite to the direction of converging collimators</p> Signup and view all the answers

    What type of collimator uses a single 2-5 mm hole?

    <p>Pinhole collimator</p> Signup and view all the answers

    What is the primary function of the scaler/timer in a gamma camera?

    <p>To measure and record the event times</p> Signup and view all the answers

    What happens to the image as the source is moved further away from a pinhole collimator?

    <p>The image gets smaller</p> Signup and view all the answers

    Which component of the gamma camera provides an image of the radionuclide injected into the patient?

    <p>Collimator</p> Signup and view all the answers

    Which type of collimator combines parallel and converging methods?

    <p>Fan beam collimator</p> Signup and view all the answers

    What role does a physicist play in nuclear medicine?

    <p>Managing the technology and equipment used in nuclear medicine</p> Signup and view all the answers

    Which method is NOT typically used for administering a tracer in nuclear medicine?

    <p>Sublimation</p> Signup and view all the answers

    What is the primary action involved in the localization phase of nuclear medicine?

    <p>Targeting specific organs or tissues with a tracer</p> Signup and view all the answers

    Which of the following best defines particulate radiation?

    <p>Radiation composed of particles like alpha and beta rays</p> Signup and view all the answers

    What is the function of a gamma camera in nuclear medicine?

    <p>To detect gamma emissions from a tracer in the body</p> Signup and view all the answers

    Which statement about nuclear medicine physicians is accurate?

    <p>They are licensed to use radioactive materials.</p> Signup and view all the answers

    What key aspect characterizes the emission phase in nuclear medicine procedures?

    <p>Gamma rays are emitted from the specific organ being studied.</p> Signup and view all the answers

    What does the nucleon binding force accomplish within an atomic nucleus?

    <p>Holds the atomic nucleus together</p> Signup and view all the answers

    What differentiates in vivo from in vitro analysis in nuclear medicine?

    <p>In vivo involves examination of living bodies.</p> Signup and view all the answers

    Which of the following is NOT a common diagnostic procedure in nuclear medicine?

    <p>Physical examination of internal organs</p> Signup and view all the answers

    What type of resolution does a shorter spatial pulse improve in continuous wave Doppler?

    <p>Axial resolution</p> Signup and view all the answers

    What is a key limitation of pulsed wave Doppler when measuring blood velocities?

    <p>Cannot measure high blood velocities in deep vessels</p> Signup and view all the answers

    How does lateral resolution depend on beam width in ultrasound imaging?

    <p>Narrower beam width leads to better lateral resolution</p> Signup and view all the answers

    What principle does color Doppler utilize to display flow velocities?

    <p>Frequency modulation</p> Signup and view all the answers

    What type of interaction occurs when sound waves strike boundaries between materials with different tissue properties?

    <p>Reflection</p> Signup and view all the answers

    What phenomenon occurs when an ultrasound wave strikes an object equal to or smaller than its wavelength?

    <p>Scattering</p> Signup and view all the answers

    What is the main cause of attenuation in ultrasound waves as they pass through tissues?

    <p>Absorption</p> Signup and view all the answers

    What occurs during acoustic shadowing in ultrasound imaging?

    <p>Decreased signal intensity behind strong reflectors</p> Signup and view all the answers

    How does focusing affect ultrasound imaging resolution?

    <p>Improves overall image quality</p> Signup and view all the answers

    What is the role of the Time-gain-compensation (TGC) amplifier in ultrasound?

    <p>Compensate for tissue attenuation</p> Signup and view all the answers

    What is one characteristic of ultrasound artifacts?

    <p>They appear as structures not reflective of actual tissues</p> Signup and view all the answers

    What occurs during the phenomenon of reverberation in ultrasound imaging?

    <p>Production of spurious echoes due to repeated reflection</p> Signup and view all the answers

    What is the typical speed of ultrasound propagation in soft tissues?

    <p>1540-4620 m/s</p> Signup and view all the answers

    How does increasing the frequency of ultrasound waves affect absorption?

    <p>Increases absorption</p> Signup and view all the answers

    What type of transducer provides a wide field of view and is best suited for abdominal and obstetric scanning?

    <p>Sector/curvilinear array transducer</p> Signup and view all the answers

    Which effect describes the conversion of mechanical energy into electrical energy in ultrasound technology?

    <p>Inverse piezoelectric effect</p> Signup and view all the answers

    The impedance matching layer in an ultrasound transducer serves to enhance what aspect?

    <p>Transmission into the body</p> Signup and view all the answers

    Which type of transducer is characterized by a flat face and is used primarily in cardiac ultrasound?

    <p>Phased array transducer</p> Signup and view all the answers

    What parameter determines lateral resolution in ultrasound imaging?

    <p>Width of the beam</p> Signup and view all the answers

    What is the primary characteristic of a large piezo crystal diameter in ultrasound applications?

    <p>Increased divergence of the beam</p> Signup and view all the answers

    Which feature is typical of a transducer with a small crystal diameter?

    <p>Improved axial resolution</p> Signup and view all the answers

    What is the purpose of an acoustic lens in an ultrasound transducer?

    <p>Control lateral resolution</p> Signup and view all the answers

    Which statement best describes the concept of bandwidth in ultrasound technology?

    <p>The range of frequencies contained within an ultrasound pulse</p> Signup and view all the answers

    The near field of an ultrasound beam is characterized by which feature?

    <p>Greater resolution</p> Signup and view all the answers

    What is the primary function of a gamma camera in nuclear medicine?

    <p>To transform radioactive emissions into images</p> Signup and view all the answers

    Which statement best describes radionuclide therapy?

    <p>It utilizes radioactive materials for therapeutic purposes</p> Signup and view all the answers

    What does the term 'tracers' refer to in nuclear medicine?

    <p>Radioactive drugs used in diagnostic procedures</p> Signup and view all the answers

    What occurs when ultrasound energy is lost to tissue energy and converted into thermal energy?

    <p>Absorption</p> Signup and view all the answers

    Who is considered the father of nuclear medicine?

    <p>Georg Charles de Hevesy</p> Signup and view all the answers

    What determines the reflection of an ultrasound wave at the boundary between two media?

    <p>Acoustic impedance difference</p> Signup and view all the answers

    What is one characteristic of a radionuclide used in therapeutic applications?

    <p>It must have appropriate energy levels for treating diseases</p> Signup and view all the answers

    Which branch of nuclear medicine focuses on utilizing radioactive materials for diagnosis and therapy?

    <p>Nuclear imaging</p> Signup and view all the answers

    Which of the following materials is NOT typically a piezoelectric crystal used in transducers?

    <p>Copper</p> Signup and view all the answers

    What happens to the ultrasound beam when it encounters two media with the same acoustic impedance?

    <p>100% energy is transmitted</p> Signup and view all the answers

    What type of information can a gamma camera record in nuclear medicine?

    <p>Physiologic and pathophysiologic information</p> Signup and view all the answers

    What describes the behavior of sound waves when they strike a boundary and some return to the source?

    <p>Reflection</p> Signup and view all the answers

    What is the primary focus of therapeutic procedures in nuclear medicine?

    <p>Treatment of diseases using radioactive substances</p> Signup and view all the answers

    Which type of scattering occurs due to interaction with smaller reflectors?

    <p>Rayleigh scattering</p> Signup and view all the answers

    What is the primary characteristic of a high-density substance in terms of acoustic impedance?

    <p>It has high acoustic impedance</p> Signup and view all the answers

    In terms of ultrasound energy propagation, what does the term 'refraction' refer to?

    <p>Change in direction of the beam</p> Signup and view all the answers

    What occurs when the difference in acoustic impedance between two materials is high?

    <p>High chance of reflection</p> Signup and view all the answers

    What does the piezoelectric effect describe in relation to ultrasound transducers?

    <p>Conversion of electrical energy into mechanical energy</p> Signup and view all the answers

    What is the purpose of the photodiode in a detector array?

    <p>To detect and convert light into an electrical signal</p> Signup and view all the answers

    Which characteristic is NOT associated with gas-filled detectors?

    <p>Requires a constant power supply</p> Signup and view all the answers

    In which imaging technique is the plane of the image perpendicular to the long axis of the body?

    <p>Axial tomography</p> Signup and view all the answers

    What does geometric efficiency refer to in detector systems?

    <p>The sensitive area of detectors relative to total exposed area</p> Signup and view all the answers

    What is the primary purpose of a scintillation detector?

    <p>To convert radiation into an electrical signal</p> Signup and view all the answers

    What aspect does quantum efficiency measure in a detector?

    <p>The fraction of incident X-rays absorbed and contributing to the signal</p> Signup and view all the answers

    What is an advantage of high scatter suppression in detector systems?

    <p>Reduces background noise and enhances image clarity</p> Signup and view all the answers

    Which component has the highest cooling rate in a spiral CT system?

    <p>Anode head</p> Signup and view all the answers

    What does dose efficiency represent in a detector?

    <p>The product of geometric, quantum, and conversion efficiencies</p> Signup and view all the answers

    Which is true about the life expectancy of tubes in conventional CT machines?

    <p>They last for approximately 5000 exposures</p> Signup and view all the answers

    What defines the stopping power of a detector material?

    <p>The amount of energy lost by radiation passing through</p> Signup and view all the answers

    Which statement accurately describes the first CT scan machine?

    <p>It involved 180 translations and 1 degree of rotation</p> Signup and view all the answers

    What is the typical range for overall dose efficiency values in detectors?

    <p>Between 0.45 and 0.85</p> Signup and view all the answers

    What happens during beta plus decay?

    <p>A proton is converted into a neutron and a positron.</p> Signup and view all the answers

    What is primarily produced during electron capture?

    <p>A neutron and a neutrino.</p> Signup and view all the answers

    What role do radionuclides play in radiopharmaceuticals?

    <p>They determine the biodistribution and behavior in the body.</p> Signup and view all the answers

    Which isotope is primarily used for thyroid function diagnosis?

    <p>Iodine-131</p> Signup and view all the answers

    What is the half-life of Nitrogen-13 typically used for?

    <p>10 minutes for myocardial perfusion imaging.</p> Signup and view all the answers

    Which of the following is not typically used in radiolabeling?

    <p>Cacao Butter</p> Signup and view all the answers

    What is the significance of gamma emitters in radiopharmaceuticals?

    <p>They allow for external detection and measurement post-administration.</p> Signup and view all the answers

    In the context of imaging, what does the term 'biodistribution' refer to?

    <p>The distribution of the agent throughout the body.</p> Signup and view all the answers

    Which property distinguishes alpha decay from beta decay?

    <p>Alpha decay decreases the atomic mass by 4.</p> Signup and view all the answers

    What is the function of biologically active molecules in radiopharmaceuticals?

    <p>To serve as a tracer and determine biodistribution.</p> Signup and view all the answers

    Which compound is commonly used for myocardial perfusion imaging?

    <p>Technetium-99m</p> Signup and view all the answers

    Which of the following is a common characteristic of radionuclides used in diagnostic imaging?

    <p>They must not emit alpha particles.</p> Signup and view all the answers

    What diagnostic purpose does Technetium-99m serve?

    <p>Cardiovascular imaging.</p> Signup and view all the answers

    What is a key feature of cobalt-57 used in medical imaging?

    <p>It is used to assess RBC volume.</p> Signup and view all the answers

    Which radionuclide is known for its rapid decay time?

    <p>Fluorine-18</p> Signup and view all the answers

    What does the term 'hyperechoic' refer to in ultrasound imaging?

    <p>Producing more echoes than normal</p> Signup and view all the answers

    Which transducer is specifically designed for high-frequency imaging inserted into the rectum?

    <p>Endorectal transducer</p> Signup and view all the answers

    Which layer of a blood vessel is referred to as the intima?

    <p>Inner layer of the vessel</p> Signup and view all the answers

    What does the term 'ischemia' describe in a cardiac context?

    <p>Damage due to blood supply disruption</p> Signup and view all the answers

    Which term describes structures that appear nearly the same in texture as their surrounding tissue?

    <p>Isoechoic</p> Signup and view all the answers

    What is lateral resolution in ultrasound imaging?

    <p>Ability to distinguish two structures lying perpendicular to the sound beam</p> Signup and view all the answers

    What is the primary characteristic of a leiomyoma?

    <p>It is the most common benign tumor</p> Signup and view all the answers

    What does the term 'embryo' refer to during early development?

    <p>A developing zygote through the 10th week of gestation</p> Signup and view all the answers

    What is the definition of 'gestational age'?

    <p>The length of time from the first day of the last menstrual period</p> Signup and view all the answers

    What describes a 'follicular cyst'?

    <p>A functional ovulatory cyst with an ovum</p> Signup and view all the answers

    Which statement best defines 'posterior acoustic shadowing'?

    <p>Reduction in reflection amplitude from strongly reflecting structures</p> Signup and view all the answers

    What does 'phasic flow' refer to in venous circulation?

    <p>Normal venous respiratory variations in blood flow</p> Signup and view all the answers

    How is the 'piezoelectric effect' best described?

    <p>Conversion of pressure to electrical voltage</p> Signup and view all the answers

    What does 'heterogeneous' refer to in a medical context?

    <p>Having a mixed composition of tissues or cells</p> Signup and view all the answers

    Which of the following best describes 'non-invasive techniques'?

    <p>Methods that do not break the skin or enter cavities</p> Signup and view all the answers

    What is the main purpose of the myometrium in the uterus?

    <p>To provide a thick muscular layer for uterine contractions</p> Signup and view all the answers

    What is the primary purpose of a gamma camera in nuclear medicine?

    <p>To transform emissions into images for diagnosis</p> Signup and view all the answers

    Which of the following best describes a tracer in nuclear medicine?

    <p>A radioactive substance that provides physiological information</p> Signup and view all the answers

    What specific condition may be treated using radionuclide therapy?

    <p>Benign diseases such as hyperthyroidism</p> Signup and view all the answers

    Which of the following described the father of nuclear medicine?

    <p>Georg Charles de Hevesy</p> Signup and view all the answers

    What type of information do scintillation cameras provide?

    <p>Physiologic or pathophysiologic images</p> Signup and view all the answers

    What is the role of radionuclides in therapeutic procedures?

    <p>To provide targeted treatment via radioactivity</p> Signup and view all the answers

    Which of the following best defines scattering in the context of ultrasound imaging?

    <p>Diffusion of sound in multiple directions upon encountering particles</p> Signup and view all the answers

    What is the significance of Hal Anger's contribution to nuclear medicine?

    <p>He created the gamma camera</p> Signup and view all the answers

    What is the main purpose of scintillation detectors in nuclear medicine?

    <p>To flash light when ionization particles pass through crystals</p> Signup and view all the answers

    Which imaging technique relies on phagocytosis for visualization in nuclear medicine?

    <p>Antigen-antibody tumor imaging</p> Signup and view all the answers

    What factor does NOT affect the geometric efficiency of collimators in scintillation detectors?

    <p>Type of scintillation crystal used</p> Signup and view all the answers

    In the context of active transport imaging, which of the following organs is primarily assessed?

    <p>Kidneys</p> Signup and view all the answers

    What is a key functional difference between survey meters and Geiger-Muller counters?

    <p>Geiger-Muller counters can measure contamination levels</p> Signup and view all the answers

    What is the role of receptor binding in adrenal medullary imaging?

    <p>To analyze hormonal activity in the adrenal glands</p> Signup and view all the answers

    Which of the following best describes how scintillation detectors measure the energy distribution of particles?

    <p>By detecting pulses of light emitted from ionized crystals</p> Signup and view all the answers

    What aspect of collimators contributes most to their geometric efficiency?

    <p>Arrangement of holes</p> Signup and view all the answers

    What do gas-filled detectors primarily rely on for their operation?

    <p>Ionization of gas</p> Signup and view all the answers

    Which of the following is a key factor determining detector efficiency?

    <p>Geometric efficiency</p> Signup and view all the answers

    What is the primary purpose of a photodiode in the context of detectors?

    <p>To convert light into an electrical signal</p> Signup and view all the answers

    What imaging advantage does a small focal spot provide in computed tomography?

    <p>Higher spatial resolution</p> Signup and view all the answers

    How does the term 'conversion efficiency' relate to detectors?

    <p>It indicates the ability to convert an absorbed x-ray signal to an electrical signal.</p> Signup and view all the answers

    What does overall dose efficiency indicate in a detector?

    <p>The product of geometric, quantum, and conversion efficiency.</p> Signup and view all the answers

    Which component contributes to heat dissipation in a computed tomography machine?

    <p>High speed rotors</p> Signup and view all the answers

    What is the general function of scintillation detectors?

    <p>To absorb radiation and produce light</p> Signup and view all the answers

    What was significant about the EMI scanner in the development of imaging technology?

    <p>It was the first CT scan machine.</p> Signup and view all the answers

    In computed tomography imaging, what does the plane of the image refer to?

    <p>The orientation of the image with respect to the body.</p> Signup and view all the answers

    What is the result of high scatter suppression in detectors?

    <p>Improved image clarity and accuracy.</p> Signup and view all the answers

    What occurs during the process of anode cooling in a CT machine?

    <p>The anode is heated by the x-ray tube.</p> Signup and view all the answers

    What characteristic defines conventional/axial tomography?

    <p>The image plane is parallel to the long axis of the body.</p> Signup and view all the answers

    What role does the anode head capacity play in CT imaging?

    <p>It affects the machine's heat dissipation.</p> Signup and view all the answers

    Study Notes

    Nuclear Medicine

    • Bq as a unit for disintegration per second (dps)
    • Half-life is the time required for radioactivity to decrease to half its initial value
    • Biological half-life is the time for half the amount of a substance to be eliminated from the body
    • Radioactive decay involves the spontaneous emission of radiation from an unstable atom (parent) to reach a more stable state (daughter).
    • There are key conservation laws that apply:
      • Conservation of energy
      • Conservation of mass number
      • Conservation of electric charge
    • Types of transition in radioactive decay:
      • Isomeric transition: Rearrangement of protons and neutrons into the lowest energy state, with excess energy released as a gamma photon
      • Isobaric transition: Nuclear transformation

    Modes of Decay

    • Alpha decay:
      • Proton and neutron rich
      • Emission of alpha particle - most ionizing and destructive, least penetrating.
      • Alpha particles are helium nucleus (2 protons and 2 neutrons).
    • Beta minus decay:
      • Neutron rich
      • Emission of negatron and an antineutrino
      • Neutron converts into a proton, an electron (negatron) and an antineutrino.
    • Electron capture:
      • Excited nucleus transfers excess energy to an inner shell electron.
      • The electron is ejected from the atom (if excess energy is greater than binding energy), resulting in conversion electron.
      • Filling of the vacancy creates a characteristic x-ray and a free electron.
    • Gamma decay:
      • Excess energy in the nucleus is released in the form of gamma rays (photons).
      • No change in atomic number.
      • Can occur directly (from excited nuclear state) or after other decays (alpha or beta).

    Radiopharmaceuticals

    • Thallium chloride (CF-201): Used for myocardial imaging, half-life of 73.5 hrs.
    • Xenon (133Xe): Used for lung ventilation imaging, half-life of 5.3 days, CF is Xenon gas.
    • Iodine-131 (131I): Used for thyroid cancer and hyperthyroidism treatment.
    • Strontium-89 chloride (89Sr) and Samarium-153 lexidronam (153Sm): Used for pain relief from cancer that is metastatic to bone.
    • Iodine-131 and Yttrium-90 (90Y) labeled monoclonal antibodies: used for treating certain non-Hodgkin's lymphomas
    • Phosphorus-32 (32P) as sodium phosphate: Used for bone marrow disorders such as polycythemia vera.
    • Main component of a radiopharmaceutical:
      • Radioactive molecule to allow monitoring of distribution and detection externally through imaging devices.

    Ideal Radiopharmaceutical

    • Ideal pharmaceutical:
      • Short biological half-life
      • Minimal side effects
      • Localizes quickly and precisely
    • Ideal radionuclide:
      • Short physical half-life
      • Pure gamma emitter
      • Easy to prepare
      • Labeling stability
      • Energy: 100-200 keV
      • Readily available
      • Suitable for incorporating into a pharmaceutical

    Design Characteristics of Radiopharmaceuticals

    • Decay in gamma emissions:
      • Suitable energy: 100-300 keV, ideal for gamma cameras
      • Sufficient abundance of emissions for detection
    • No particulate emissions/radiation:
      • Increases patient radiation dose
      • Does not contribute to diagnostic information
    • Beta emissions:
      • Used primarily for therapeutic radiopharmaceuticals due to higher energy and greater tissue damage
    • Optimal effective half-life:
      • Long enough for intended application
      • Typically a few hours
      • High specific activity
      • Prevents toxic effects to the patient

    Technetium-99m (Tc-99m)

    • Most commonly used radionuclide
    • Readily available
    • Favorable energy: 140 keV
    • Monoenergetic gamma photon (consistent energy)
    • Favorable dosimetry: lacks primary particulate radiations
    • Ideal half-life: 6 hours, good balance for many imaging studies
    • Advantages:
      • Short half-life: Reduces patient radiation exposure
      • Pure gamma emitter: Good for imaging
      • High specific activity: Improved resolution
      • High stability: Minimizes disintegration during preparation and administration
      • Multiple forms: Can be incorporated into various radiopharmaceuticals for different applications

    Technetium-99m (Tc-99m) vs Technetium-99 (Tc-99)

    • Tc-99m:
      • Half-life: 6 hours
      • Emits: Gamma radiation
      • Decay product of Mo-99 (molybdenum-99): Through isobaric transition
    • Tc-99:
      • Half-life: 211,000 years (long-lasting)
      • Emits: Beta particulate radiation
      • Decay product of U-235 (uranium-235): Through fission

    Forms of Technetium-99m:

    • Tc-99m pertechnetate (99mTcO4-): Common form in the body, both the radionuclide and the pharmaceutical component.
      • Can be used for thyroid imaging, brain scans, and gastrointestinal studies
    • Tc-99m-labeled radiopharmaceuticals: Examples include:
      • Mebrofenin (Hepatolite): Used for liver imaging.
      • MAG3 (mercaptoacetyltriglycine): Used for kidney function studies.
      • Bicisate (Ceretec): Used for brain perfusion studies.
      • Disofenin (Hepatolite): Used for liver imaging.
      • Diethylenetriamine-pentaacetic acid (DTPA): Used renal dynamic scintigraphy, lung ventilation studies, thyroid cancer and hepatocellular carcinoma imaging.

    Iodine-131 (131I)

    • Used for thyroid imaging and treatment.
      • Often used for thyroid cancer and hyperthyroidism

    Nuclear Medicine Procedures

    • Diagnostic Procedures:
      • Use radioactive materials to test body functions.
      • Common radioisotopes: Tc-99m and F-18 (fluorine-18).
    • In Vitro Procedures:
      • Analyze samples outside the body.
      • Detecting gamma-emitting radionuclides in urine and feces.
    • In Vivo Procedures:
      • Examine the living body.
      • Use gamma camera to detect gamma-emitting radionuclides introduced into the body.
        • Common methods: injection of a radiopharmaceutical.

    Nuclear Physics

    • Atom:
      • Fundamental building block of matter.
      • Smallest part of an element with all the properties of that element.
    • Nucleus:
      • Positively charged central part of the atom.
      • Contains most of the atom's mass.
      • Composed of nucleons (protons and neutrons).
      • Forces:
        • Repulsive force: Between protons due to similar charges.
        • Nucleon binding force: Holds the atomic nucleus together.
    • Electron cloud:
      • System of electrons revolving around the nucleus.
      • Exists in discrete energy levels.

    Particulate Radiation

    • Alpha particles:
      • Composed of 2 protons and 2 neutrons.
      • Highly ionizing and destructive, but least penetrating.
    • Beta particles:
      • Electrons (negatrons or positrons)
      • Moderately ionizing and penetrating.
    • Gamma rays:
      • High energy electromagnetic radiation.
      • Highly penetrating, with low ionizing power.
    • Neutron radiation:
      • Composed of neutrons.
      • High penetrating power, good for neutron activation.

    Continuous Wave Doppler

    • Uses continuous ultrasound waves.
    • Provides accurate measurement of high velocities.
    • Lacks depth resolution.
    • Uses spatial pulse length and wavelength to distinguish objects parallel to the beam.

    Pulsed Wave Doppler

    • Transmits ultrasound pulses allowing for depth resolution.
    • Measures blood flow speed within a specific vessel.
    • Unable to accurately measure high velocities in deeper vessels.
    • High velocities can be incorrectly displayed as low velocities.

    Lateral Resolution

    • Ability to distinguish objects perpendicular to the ultrasound beam.
    • Depends on the beam diameter.
    • Narrower beam width provides better lateral resolution.

    Colour Doppler

    • Displays different blood flow velocities in different colours.

    Duplex Doppler System

    • Directs the Doppler beam accurately towards specific blood vessels.

    Wave Propagation

    • Transmission and spread of ultrasound waves through tissues.
    • Soft tissues have an average propagation speed of 1540-4620 m/s.

    Wavelength

    • Length of a single cycle of the ultrasound wave.
    • Determines the scanner's resolution.

    Focusing

    • Adjustment of the ultrasound beam to improve resolution.
    • Can be electronic or achieved using a lens attached to the transducer.

    Amplification

    • Compensates for ultrasound attenuation using the Time-gain-compensation (TGC) amplifier.
    • Improves the quality of the final image.

    Ultrasound Interactions and Attenuations

    • Attenuation: Decrease in ultrasound wave intensity and amplitude as they pass through tissue.
    • Absorption: Conversion of ultrasound energy into heat, a major contributor to attenuation.

    Absorption

    • Higher frequencies result in greater absorption.
    • Bone has a higher absorption coefficient, increasing with protein content.

    Reflection

    • Occurs at interfaces between structures with significantly different acoustic impedance.

    Scattering

    • Occurs when ultrasound waves encounter objects smaller than the wavelength.

    Refraction

    • Beam deviation at an oblique angle interface between tissues with different wave velocities.

    Divergence

    • Beam spread due to diffraction as it travels through tissue.

    Ultrasound Artifacts

    • Image structures that do not represent the actual tissues being scanned.

    Reverberation

    • False echoes caused by repeated reflections between high impedance interfaces (Comet tail artifact).

    Acoustic Shadowing

    • Occurs behind highly attenuating structures, creating a shadow.

    Acoustic Enhancement

    • Occurs behind weakly attenuating structures, resulting in increased brightness behind the structure.

    Edge Shadowing

    • Combination of refraction and reflection at rounded structure edges.

    Beam Width Artifact

    • Echoes from side lobes are mistakenly attributed to the central axis of the main lobe.

    Slice Thickness Artifact

    • False echoes due to the beam's thickness, dependent on beam angulation.

    Side Lobe Artifact

    • False echoes generated by side lobes, affecting lateral resolution.

    Contrast Resolution

    • Ability to distinguish between tissues and display them as different shades of gray.
    • Optimized by using the correct overall gain.

    Temporal Resolution

    • Frame rate of the imaging system.
    • Higher frame rates provide better temporal resolution.

    Real-time Imaging

    • Displays movement as it happens.

    Doppler Ultrasound

    • Detects and measures blood flow.

    Doppler Effect

    • Change in apparent frequency of a wave due to relative motion between the source and observer.

    Axial Resolution

    • Ability to distinguish two structures along a path parallel to the sound beam.

    Biparietal Diameter (BPD)

    • Largest dimension of the fetal head measured perpendicular to the midsagittal plane, used to assess fetal development.

    Color Flow Doppler

    • Quantifies velocity direction by assigning a color to each pixel, with different colors representing different velocity frequency changes.

    Nuclear Medicine

    • Uses radioactive materials to test body functions.

    Administration

    • Radioactive substances, or tracers, are administered via injection, swallowing, or inhalation.

    Localization

    • Tracers concentrate in specific organs or tissues.

    Emission

    • Tracers emit gamma rays, which are then detected and form an image of the organ being studied.

    Atom

    • Fundamental building block of matter, the smallest part of an element containing all its properties.

    Nucleus

    • Positively charged central part of the atom containing most of its mass.
    • Made up of protons and neutrons.

    Electron Cloud

    • System of electrons moving around the nucleus at discrete energy levels.

    Chemical Bonding

    • Covalent bond: Formed by sharing electron pairs between atoms.

    Nuclear Transformation

    • Process by which a nucleus spontaneously emits particles to achieve stability, transforming into a different atom.

    Nuclear Medicine Physicist

    • Specialist with extensive education in basic and clinical sciences of medicine, licensed to work with radioactive materials.

    Nuclear Medicine Technologist

    • Educated in the theory and practice of nuclear medicine procedures, performing the tests.

    Physicist

    • Experienced in nuclear medicine technology and equipment, including computers.

    Collimator

    • Component of a gamma camera that filters out unwanted radiation, allowing only specific gamma rays to reach the crystal.
    • Types include converging, diverging, pinhole, fan beam.

    Photomultiplier Tube (PMT)

    • Converts light from the crystal into an electrical pulse.

    Converging Collimator

    • Holes converge to a focal point, providing magnification.

    Diverging Collimator

    • Holes angle opposite to converging collimators, creating a smaller image.

    Pinhole Collimator

    • Single 2-5 mm hole in the center, with image size dependent on source distance.

    Fan Beam Collimator

    • Combines parallel hole collimation along one axis and converging collimation along another.

    Sodium Iodide Crystal

    • Gamma rays interact with the crystal, releasing light photons.

    Pulse Height Analyzer

    • Analyzes the energy of the gamma rays, ensuring only those originating from the specific tracer are recorded.

    Scalar/Timer

    • Measures and records the number of gamma rays detected.

    Cathode Ray Tube (CRT)

    • Displays the image of the organ being studied based on detected gamma ray information.

    Ultrasound

    • Attenuation: Weakening of sound waves as they travel through a medium.
    • Absorption: Ultrasound energy lost to tissue energy, converted into heat.
    • Reflection: Sound energy strikes a boundary between two media, and some returns to the source. Most important characteristic of ultrasound.
    • Scattering: Interaction with smaller reflectors, causing reflection in multiple directions.
      • Rayleigh scattering: Occurs when the sound wave interacts with particles smaller than the wavelength.
    • Refraction: Occurs due to a difference in propagation speed between two media.
      • The beam is deviated as it travels through the medium, resulting in a bend in transmission and reflection.

    Acoustic Impedance

    • Represents the resistance of a tissue to the passage of ultrasound waves.
    • Calculated as the product of tissue density and the velocity of sound in the material.
    • A large difference in acoustic impedance between two media will cause a high percentage of the sound waves to be reflected back to the transducer.
    • High density substances: High acoustic impedance.
    • Low density substances: Low acoustic impedance.

    Piezoelectric Crystal

    • Composed of dipolar molecules that vibrate when electricity is applied.
    • The vibrations emit ultrasound pulses or mechanical waves.
    • Present inside the transducer.
    • Types:
      • Quartz (naturally occurring)
      • Lead zirconate tinate (man-made ceramic)

    Piezoelectric Effect

    • The ability of certain materials to convert mechanical energy into electrical energy and vice versa.
    • Direct piezoelectric effect: Production of an electric charge in response to applied pressure, resulting in an "echo".
    • Inverse piezoelectric effect: conversion of electrical energy into mechanical energy, resulting in a "pulse".

    Transducer/Probe

    • Converts electrical energy into ultrasound waves (mechanical) and vice versa.
    • Types:
      • Linear array transducer: Parallel scan lines, rectangular field of view, used in vascular, small parts, and musculoskeletal applications.
      • Sector/curvilinear array transducer: Provides a wide field of view, useful for abdominal and obstetric scanning.
      • Convex transducer: Wide fan-shaped, useful for all parts of the body except specialized echocardiography.
      • Phased array transducer: Flat-faced, wide field of view, used for cardiac and cranial ultrasound.

    Acoustic Lens

    • Reduces the beam width of the transducer to improve image resolution.
    • The width of the beam determines lateral resolution.
    • Lateral resolution: Ability to resolve structures across or perpendicular to the beam axis.

    Impedance Matching Layer

    • Sandwich between the piezoelectric crystal and the patient.
    • Chosen to improve the transmission of ultrasound waves into the body.

    Bandwidth

    • The range of frequencies contained within an ultrasound pulse.
      • Wide bandwidth:
        • Shorter spatial pulse length.
        • Wider range of frequency.
      • Narrow bandwidth:
        • Longer spatial pulse length.
        • Narrower range of frequency.

    Ultrasound Beam

    • Area through which the sound energy emitted from the ultrasound transducer travels.
    • 3D and symmetrical around its central axis.
    • Beam intensity: Measured in watts.
    • Near field: Area close to the transducer where the ultrasound beam is narrow and focused.
    • Far field: Area further away from the transducer where the beam diverges.

    Other terms:

    • Retrouterine pouch (cul-de-sac): Pelvic space located anterior to the rectum and posterior to the uterus; also known as the pouch of Douglas.
    • Sagittal: Plane that travels vertically from the top to the bottom of the body along the y axis.
    • Scattering: Diffusion or redirection of sound in several directions.
    • Sonar: (sound navigation and ranging) - Instrument used to discover objects underwater and to show their location.

    Nuclear Medicine

    • Branch of science that uses radioactive materials for diagnosis and treatment.
    • It determines and diagnoses based on organ or tissue function by utilizing radioactive tracers.
    • Radioactive tracer: Radioactive drug/material used in nuclear medicine procedures.
    • Radionuclide: Radioactive atom or nucleus with too many or too few nucleons.

    Radionuclide Decay

    • Beta plus decay (Positron decay): Proton-rich nucleus emits a positron (antimatter) and a neutrino.
      • One proton is converted to a neutron and a positron.
      • Decrease in atomic number by 1.
      • Isobaric transition.
    • Electron capture/K capture decay: Proton-rich nucleus captures an electron from the innermost electron shell (K-shell).
      • One proton is converted to a neutron.
      • Decrease in atomic number by 1.
      • Isobaric transition.
    • Beta minus decay: Neutron-rich nucleus emits an electron (beta particle) and an antineutrino.
      • One neutron is converted to a proton and an electron.
      • Increase in atomic number by 1.
      • Isobaric transition.
    • Alpha decay: Nucleus emits an alpha particle (two protons and two neutrons).
      • Atomic number decreases by 2, mass number decreases by 4.

    Therapeutic procedures

    • Treating diseases using radioactivity.
    • Radionuclide therapy is used in the treatment of:
      • Benign diseases: Hyperthyroidism, arthritis, and others.
      • Malignant diseases: Cancers.

    Radiopharmaceuticals

    • Substances containing radionuclides suitable for administration to humans for diagnosis or treatment of disease.
    • Gamma emitters: Used for image formation.
      • Do not emit alpha or beta particles.
    • Biologically active molecules:
      • Act as the tracer/carrier, determining the localization and biodistribution of the radiopharmaceutical in the body.
      • Influences the behavior and function of the radiopharmaceutical.

    Key Radiopharmaceuticals

    • Chromium (51Cr):
      • Half-life: 27.8 days.
      • Used for: Red blood cell volume and survival.
    • Cobalt (57Co):
      • Half-life: 270 days.
      • Used for: Vitamin B12 absorption.
    • Fluorine (18F):
      • Half-life: 110 minutes.
      • Used for: Oncology and myocardial hibernation.
    • Gallium (67Ga):
      • Half-life: 77 hours.
      • Used for: Inflammatory process and tumor imaging.
    • Indium (111In):
      • Half-life: 67.4 hours
      • Used for: Cerebrospinal fluid imaging.
    • Iodine (121I):
      • Half-life: 13.3 hours.
      • Used for: Thyroid function.
    • Iodine (131I):
      • Half-life: 8 days
      • Used for: Renal function.
    • Nitrogen (13N):
      • Half-life: 10 minutes.
      • Used for: Myocardial perfusion.
    • Rubidium (82Rb):
      • Half-life: 75 seconds
      • Used for: Cardiovascular imaging.
    • Technetium (99Tc):
      • Half-life: 6 hours.
      • Used for: Imaging of various organs, including brain, thyroid, liver, spleen, lungs, and heart.

    Imaging Applications

    • Single Photon Emission Computed Tomography (SPECT): Uses gamma camera to obtain 3D images.
    • Positron Emission Tomography (PET): Uses positron-emitting isotopes to produce high-resolution images of metabolic activity.

    PET Camera

    • Contains a ring of detectors (scintillators) surrounding the patient.
    • Detectors are coupled to PMTs to detect light produced in each detector.

    CT scan

    • Godfrey is considered the father of CT scan imaging.
    • In 1979, Hounsfield and Allan Mcleod Cormack shared the Nobel prize in physics for their work on CT imaging.
    • CT scan machines became widely available in 1980.

    EMI Scanner

    • The first CT scan machine.
    • Had 180 translations and 1 degree of rotation.
    • Acta was the first CT system that could make images of any part of the body.

    Conventional/Axial Tomography

    • The plane of the image is parallel to the long axis of the body.
    • Produces sagittal and coronal images.

    Computed Tomography

    • The plane of the image is perpendicular to the long axis of the body.

    CT Machine

    • Imaging time: 120 kvP, 400mA
    • High-speed rotors for heat dissipation
    • Anode head capacity: 7 MHU (Spiral CT)
    • Heat storage capacity: 8 MHU
    • Anode cooling rate: 1MHU/min
    • Small focal spot; ensures high spatial resolution imaging
    • Tube life: 5000 exposures (Conventional CT)

    Detector Array

    • The entire collection of detectors
    • Image receptor in CT
    • Detectors absorb radiation and convert it to an electrical signal.

    Detector Efficiency

    • The ability of a detector to capture transmitted photons and change them to an electronic signal.
    • High scatter suppression is important.
    • High stability allows a system to be operational without frequent calibration.

    Detector Types

    • Gas-filled detectors: previously used
    • Scintillation and SSD detectors: recently used

    Gas Detectors

    • Ionization of gas:
      • Ionization chamber
      • Proportional counter
      • Geiger-Muller counter
    • Characteristics:
      • Excellent stability
      • Large dynamic range
      • Low quantum efficiency

    Scintillation Detector

    • Photodiode: converts light into an electrical signal.
    • Does not require a power supply

    Three Important Factors Contributing to Detector Efficiency:

    • Geometric Efficiency:
      • The area of the detectors sensitive to radiation as a fraction of the total exposed area.
      • The amount of space occupied by the detector collimator plates relative to the surface area of the detector.
    • Quantum Efficiency:
      • The fraction of incident x-rays on the detector that are absorbed and contribute to the measured signal.
    • Conversion Efficiency:
      • The ability to accurately convert absorbed x-ray signal to an electrical signal.
    • Overall/Dose Efficiency:
      • The product of geometric, quantum, and conversion efficiency.
      • The product of:
        • Stopping power of the detector material
        • Scintillator efficiency (in solid-state types)
        • Charge collection efficiency (in xenon types)
        • Geometric efficiency
        • Scatter rejection
      • Normal value: between 0.45-0.85

    Nuclear Medicine

    • Branch of science that uses radioactive material for diagnosis and therapy
    • Determines and diagnoses based on organ or tissue function
    • Tracers: Radioactive drugs/materials used in procedures
    • Radionuclide: Radioactive atom or nucleus; too many or too few nucleons
    • Radiopharmaceutical: Traces a particular physiologic or pathology process

    Two Branches of Nuclear Medicine

    • Therapeutic procedures: Treat diseases by means of radioactivity
      • Used to treat:
        • Benign diseases (e.g. hyperthyroidism and arthritis)
        • Malignant diseases (e.g. cancer)
    • Diagnostic procedures:
      • Uses radioisotopes as tracers to detect certain physiological abnormalities

    Therapeutic Procedures

    • Treat diseases by means of radioactivity
    • Treatment of:
      • Benign diseases (e.g., hyperthyroidism and arthritis)
      • Malignant diseases (e.g., cancer)

    Diagnostic Procedures

    • Uses radioisotopes as tracers to detect certain physiological abnormalities

    Types of Diagnostic Procedures

    • Cell sequestration: Splenic imaging (heat damaged RBC), WBC
    • Receptor binding and storage: Adrenal medullary imaging, somatostatin
    • Phagocytosis: Reticuloendothelial system imaging
      • Antigen-antibody tumor imaging
    • Active transport: Hepatobiliary imaging, renal tubular function, thyroid and adrenal imaging

    Detection Process

    • Gamma camera or scintillation camera transforms emissions into images, providing physiologic or pathophysiologic information.

    Recording Process

    • The camera records information in a computer or film

    Geiger-Muller Counter

    • Voltage is increased even higher than in the proportional chamber application.
    • All the molecules of the gas are ionized, liberating a large number of electrons.
    • Results in a large electron pulse and detection of single events but not energy.
    • Used for contamination control in Nuclear Medicine laboratories.

    Types of Collimators

    • Parallel Hole Collimator:
      • Most common used collimator.
      • Consists of a large number of small holes, separated by the lead septa which are parallel to each other.
      • Usually perpendicular to the crystal.
      • Geometric efficiency is affected by:
        • Shape of collimator holes
        • Length of collimator holes
        • Diameter of collimator holes

    CT Scan

    • Godfrey Hounsfield - father of CT scan imaging
    • 1979 - Hounsfield and Allan Mcleod Cormack shared Nobel prize in physics
    • 1980 - CT scan machine became widely available

    EMI Scanner

    • First CT scan machine
    • 180 translation/1deg rotation
    • Acta - first CT system that could make images of any part of the body

    Conventional/Axial Tomography

    • Plane of the image is parallel to the long axis of the body
    • Produces sagittal and coronal images

    Computed Tomography

    • Plane of image is perpendicular to the long axis of the body
    • Uses a rotating x-ray tube and a series of detectors to create a 3D image

    CT Scanner Components

    • High Speed Rotors: for heat dissipation
    • Anode Head Capacity: 7 MHU (Spiral CT)
    • Heat Storage Capacity: 8 MHU
    • Anode Cooling Rates: 1MHU/min
    • Small Focal Spot: due to high spatial resolution imaging
    • Tube Life: 5000 exposures (Conventional CT)

    Detector Array

    • Entire collection of detectors
    • Image Receptor in CT
    • Detector: absorbs radiation and converts it to an electrical signal
    • High Detector Efficiency: ability of the detector capture transmitted photons and change them to an electronic signal.
    • High Scatter Suppression: reduces noise in the image
    • High Stability: allows the system to be used without interruption of frequent calibration

    Types of Detectors

    • Gas-filled detectors: previously used
      • Ionization chamber
      • Proportional counter
      • Geiger-Muller counter
    • Scintillation and SSD: recently used

    Gas Detector

    • Ionization of gas is the principle.
    • Three types:
      • Ionization chamber
      • Proportional counter
      • Geiger-Muller Counter
    • Characteristics:
      • Excellent stability
      • Large dynamic range
      • Low Quantum Efficiency

    Scintillation Detector

    • Depends on excitation
    • When ionization particles pass through certain crystals, it flashes light or scintillation is emitted.
    • Most commonly used type in nuclear medicine.
    • Used to measure the energy distribution of particles in addition to counting them.
    • High sensitivity to gamma rays. (PET Camera contains a ring of detectors surrounding the patient, detectors are coupled to PMT to detect light produced in each detector)

    Factors Contributing to Detector Efficiency

    • Geometric Efficiency: the area of the detectors sensitive to radiation as a fraction of the total exposed area
    • Quantum Efficiency: the fraction of incident x-rays on the detector that are absorbed and contribute to the measured signal
    • Conversion Efficiency: the ability to accurately convert absorbed x-ray signal to electrical signal
    • Overall/Dose Efficiency: the product of geometric, quantum and conversion efficiency. Product of the following factors:
    • Stopping power of the detector material
    • Scintillator efficiency (in solid state types)
    • Charge collection efficiency (in xenon types)
    • Geometric efficiency
    • Scatter rejection
    • Normal Value: between 0.45-0.85
    • Value: depends on the type of detector used.

    Photodiode

    • Converts light into an electrical signal
    • Does not require a power supply

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