幻灯片 1 - Florida Institute of Technology

幻灯片 1 - Florida Institute of Technology

Chapter 8 Planar Scintigaraphy Hui Pan Chapter 8, Planar Scintigraphy What is Planar Scintigraphy? Planar Scintigraphy: unlike x-ray imaging, use Anger scintillation camera, a type of electronic detection instrumentation, to generate medicineal image. The corresponding tomographic imaging method: SPECT (single photon emission computed tomography).

PET (positron emission tomography) Chapter 8, Planar Scintigraphy Different of Modalities Three basic imaging modalities in nuclear medicine: Planar imaging, SPECT, PET. 1. SPECT & Planar vs PET : radiotracers 2. SPECT & PET techniques.

vs Planar : reconstruct image Chapter 8, Planar Scintigraphy Components of an Anger scintillation camera. Chapter 8, Planar Scintigraphy Collimator The collimator defines the kind of projection and

determines the direction of the incident photon for any scintillation in the crystal. The types of collimators : parallel-hole, converging, diverging, and pinhole. Chapter 8, Planar Scintigraphy Different type of collimators Parallel-hole collimator: consists of an array of parallel holes perpendicular to the crystal face. Converging collimator: has an array of tapered holes that aim at a point.

Diverging collimator: is essentially an upside-down converging collimator. Pinhole collimator: thick conical collimators with a single 2 to 5 mm hole in the bottom center. Chapter 8, Planar Scintigraphy Different type of collimators Chapter 8, Planar Scintigraphy Scintillation Crystal

The scintillation detector is the most commonly used detector in nuclear medicine, because it is more sensitive to electromagnetic radiation than is a gas-filled detector. This type of detector is based on the property of certain crystals to emit light photons after deposition of energy in the crystal by ionizing radiation. Chapter 8, Planar Scintigraphy Photomultiplier Tubes

Each gamma photon that interacts in the scintillation crystal produces a burst of light in the crystal, comprising thousands of light or scintillation photons. This light is reflected and channeled out of the back of the crystal, through a glass plate, and is incident upon an array of photomultiplier tubes. Chapter 8, Planar Scintigraphy Photomultiplier Tubes Positioning Logic:

The goal of the Anger cameras positioning logic circuitry is to determine both (1) where the event occurred on the face of the crystal and (2) the combined output of all the tubes, which represents the light output of the crystal. Chapter 8, Planar Scintigraphy Pulse Height Analyzer Chapter 8, Planar Scintigraphy Gating Circuit

The pulse height analyzer is used to set an acceptance window around the photopeak. Its lower threshold is set to discriminate against Compton events, which have lower energy than a non-Compton event. Its upper threshold is set to discriminate against multiple events, which have more energy than a single event. Chapter 8, Planar Scintigraphy

Image Formation The primary mechanism for creating images in planar scintigraphy is to detect and estimate the position of individual scintillation events on the face of an Anger camera, i.e. X and Y coordinates on detector head Chapter 8, Planar Scintigraphy Image Formation First step, calculate the mass of the light distribution: Z=

K a k, k 1 Where k is the number of photomultiplier tubes.

ak is the amplitudes of their response to a scintillation event. Chapter 8, Planar Scintigraphy Image Formation Second step, calculate the center of mass (X, Y) 1 Z X=

Y= 1 Z K xk a k ,

k 1 K k 1 y k ak , Chapter 8, Planar Scintigraphy

Acquisition Modes Acquisition Mode is defined when W/R DCB line is set LO and the FIFO of any module is addressed in the address register-field; the module-field of the address is inessential. The types of Acquisition Mode list mode, static frame mode, dynamic frame mode, multiple-gated acquisition, whole body.

Chapter 8, Planar Scintigraphy Acquisition Modes Acquisition Mode is defined when W/R DCB line is set LO and the FIFO of any module is addressed in the address register-field; the module-field of the address is inessential. The types of Acquisition Mode list mode, static frame mode, dynamic frame mode,

multiple-gated acquisition, whole body. Chapter 8, Planar Scintigraphy Anger Camera Imaging Equation Chapter 8, Planar Scintigraphy Anger Camera Imaging Equation each photon has equal probability to propagate in any direction. (when a gamma ray hits the camera, it will usually be absorbed by the lead in

the collimator because it will eith be traveling in an improper direction or will miss a collimator hole.) Ignoring Compton scattering in our development of an imaging equation, photons are assumed to travel in straight lines. energy fluence rate / intensity : Id = AE 4r 2 Chapter 8, Planar Scintigraphy

Anger Camera Imaging Equation Id = AE 4r 2 A is the position of radioactivity in the body. E is the energy of each photon. r is the distance from object point (x , y, z) to a detector position (xd , yd , 0);

Chapter 8, Planar Scintigraphy Image Quality 1. Many factors affect the performance of Anger cameras, such as spatial resolution, sensitivity and field uniformity. 2.

Modern Anger cameras contain correction circuitry to improve performance in these areas as much as possible. Chapter 8, Planar Scintigraphy Image Quality Resolution: A basic measure of image quality is resolution. For our purposes, resolution can be thought of as the ability of a medical imaging system to accurately depict two distinct events in space, time or frequency as separate.

Chapter 8, Planar Scintigraphy Image Quality Two factors affecting resolution are most important: collimator resolution and intrinsic resolution. Collimator Resolution: Rc = d (l b | z |),

l Where d is the collimator hole diameter, l is the collimator hole length, b is the scintillator depth |z| is the collimator surface-to-patient distance. Chapter 8, Planar Scintigraphy Image Quality Two factors affecting resolution are most important: (1) collimator

resolution and (2) intrinsic resolution. Intrinsic Resolution: Additional blurring takes place in the scintillator itself, however, and this process is characterized by the intrinsic resolution of the Anger camera. Two reasons for inaccuracy in estimation of (X, Y) in an Anger camera, 1.Path of the absorbed photon. 2.Noise. Chapter 8, Planar Scintigraphy Image Quality

Sensitivity: Detect the gamma ray that are directed at the camera in the right direction (depends on the number of photons properly detected) Two major factors that prevent detection: 1.The photon may be absorbed in the collimator; 2.The photon may pass through both the collimator and the scintillation crystal. Chapter 8, Planar Scintigraphy Image Quality

High sensitivity detect most photons Low sensitivity reject most photons Chapter 8, Planar Scintigraphy Image Quality

Collimator Sensitivity: 2 Kd 2 ( ) le ( d h

Chapter 8, Planar Scintigraphy Image Quality Detector Efficiency Not every gamma ray that passes through the detector crystal will deposit energy in the detector material. No energy is deposited means no pulse will be generated. Chapter 8, Planar Scintigraphy Image Quality

Uniformity: Field uniformity is the ability of the camera to depict a uniform distribution of activity as uniform. At one time, it was thought that nonuniform response arose from changes in sensitivity across the crystal. To correct the nonuniform, a uniform floor or sheet source of radioactivity was imaged and recorded and used as a reference. Chapter 8, Planar Scintigraphy Image Quality

Energy Resolution Pulse height analysis is critical for rejection of scattered photons, whose inclusion in the image would reduce contrast. Thus, the performance of the pulse height analyzer, and especially its energy resolution, is critical. The worse the energy resolution of a pulse height analyzer, the broader the photopeak. Chapter 8, Planar Scintigraphy Image Quality Noise,

In a Possion process, the variance is equal to the mean, which we have used to simplify the analysis of noise in projection radiography. SNR N N N Chapter 8, Planar Scintigraphy

Image Quality Factors Affecting Count Rate: Increasing the number of detected counts - > improve the performance of the Anger camera. 1 Maximum counting rate

Recently Viewed Presentations

  • The Uberization of Talent Management in Law Firms

    The Uberization of Talent Management in Law Firms

    Uberization. Derived from the ride share company Uber. An innovation that makes an existing task or service easier . and . accessible. This can disrupt the existing industry so it permanently changes or creates a new industry
  • www.miro.ing.unitn.it

    www.miro.ing.unitn.it

    Heuristic control algorithm . Instantaneous center of rotation control algorithm. Mine simulation. Unity simulation. Dynamic Model in Unity: Wheel collider. Car-like & differential model. PID controller and velocity profile. PID's parameters tuning.
  • Risk Assessment, Audit Processes and Sample Sizes Its

    Risk Assessment, Audit Processes and Sample Sizes Its

    Covers major areas of cost accumulation . POLICY! Identifies firm size. Identifies officers. Identifies owners. Identifies related parties. Information on financial management system. Labor costing method. Premium overtime. Contract labor. Formal Risk Assessment.
  • Models of Cd Absorption by Italian Parsley Brittany

    Models of Cd Absorption by Italian Parsley Brittany

    Both Model 1 and Model 2 indicate there is a significantly higher deposition of Cd in plant roots versus plant shoots (Figures 5-6). In Model 1, the data suggest that the % Cd absorption is higher in roots than in...
  • Constructing geometric shapes - 7th Grade Science

    Constructing geometric shapes - 7th Grade Science

    EQ: How do we use formulas for Area and Circumference of Circles? What is a circle? A circle is a set of points in a plane that are the same distance from the center.
  • Rittenberg/Schwieger/Johnstone Auditing: A Business Risk Approach Sixth Edition

    Rittenberg/Schwieger/Johnstone Auditing: A Business Risk Approach Sixth Edition

    The standards for compilations and reviews of financial statements of non-public entities are called Statements on Standards for Accounting and Review Services (SSARS) Financial Statement Reviews (continued) Inquiry and analytical procedures are performed for each significant account balance Accountant does...
  • Character Vs. Self

    Character Vs. Self

    Character Vs. Self Character Vs. Nature Character Vs. Society Character Vs. Character Jimmy is fighting against depression. Jamie is learning to walk again after suffering serious injuries. An old man is trying to quit smoking. Brian is trying to do...
  • THE FEDERAL BUREACRACY - Amherst County High School

    THE FEDERAL BUREACRACY - Amherst County High School

    The Federal Bureaucracy Consists of Executive Office Executive Departments (President's Cabinet) Independent Agencies (Page 429) The Federal Bureaucracy is: 4 million employees; 2.8 million are civilians or "civil servants" President only appoints 3% 15 cabinet level departments 150+ independent agencies...