COMPUTER SCIENCE :COMPUTER SCIENCE GROUP IV: Gipsy Morales Viviana Gonzalez Michael Mallo


Objectives :Objectives Describe the presentation of data in decimal, binary, octal, and hexadecimal format Analyze data representation Describe hardware Discuss the function of frequency filters. Describe the process of reconstructing images in SPECT systems. Define non-imaging computer application. Discuss the use of the internet as well as the definition of a network.


History :History 1500 BC→ Chinese invented the abacus 1889→ Herman Hollerith 1939 → John Atanasoff and Clifford Berry 1965 → digital equipment corporation 1971 → the first microprocessor 1970’s → the first computer into NM imaging


Data Representation :Data Representation Fundamental building block → transistor Binary →use for numbers representation Decimal →numbers from 0 through 9 Hexadecimal → numbers supplemented with letters 8 bits = 1 byte 2 bytes= 1 word 1 word= 16 bits in length Memory requirements Kilobytes Megabytes gigabytes


Hardware :Hardware Central Processing Units (CPU) regulate the system operation interact with memory Coordinate the control of input/output devices Components: Control unit (CU) Arithmetic logic unit (ALU)


Hardware :Hardware Memory Read-only memory (ROM) Random-access memory (RAM) Basic input/output system (BIOS) Direct memory access (DMA) Reduced-instruction set computer (RISC)


Hardware :Hardware Input/Output devices (I/O) Bus →communication of the CPU with the outside world Display terminals →keyboard and monitor Mouse →mechanical mouse Optical mouse Light pen Printer →laser printer Ink-jet printer Modem →connect computers with telephone line or high-speed


Hardware :Hardware Data storage Disk →magnetic disk, floppy, and hard disk Floppy disk →allows file to be stored Optical disk →latest technology to write large amounts of data on a very small area


Hardware :Hardware Camera interface Analog-to digital converters Digitize the X and Y signals No loss storing counts and waiting for them to transform electronic pulses into the digital format


Hardware :Hardware Care and quality assurance Air condition at 700 F Humidity around 50% Away any electromagnetic fields Voltage very small Cleanliness of environment Quality testing


Software :Software Software Set of instructions that provide control over the calculations and subsystems of the computer. Calculations Word processing Game playing Image processing System software Comprises the programs and files necessary Internal operation of the computer Programs necessary to manipulate the files. Programming software Editor (Word processing) Support libraries


Software :Software User Programs Instructions to execute applications needed Word processing, image processing Operating systems Systems software Set of programs used to control, assist and run other programs Toolbox Subprograms Interacts with disks, graphic display, modem and camera interface Allows user to list programs and file on disk Loading and executing programs Create, copy and delete files To create, modify and store data.


Software :Software Operating systems Large programs Stored on a Disk Operating System (DOS) Has a monitor with the portions not needed by memory retained on a disk until, they are needed. Controls internal functions in running programs Advance operating systems Foreground & Background operations (simultaneously) Foreground Process that has priority (Image acquisition program) When uses DMA (direct memory access) should have minimal requirements of the CPU Some other type of operation can be performed simultaneously


Software :Software Programming languages Machine oriented language Series of zeros and ones High level programming languages English Editor Program that allows keyboard entry of written material to create, modify and save Program Interpreted Program is interpreted to machine code and one line of instructions is executed at a time No zeros and ones Language runs very slowly


Software :Software Basic Beginners All Purpose Symbolic Instruction Code Lines of instructions are numbered Executed in numerical order Elementary image processing quickly Rapid image manipulation Ex: Decay processing We only provide the dose needed and the radiopharmaceutical Compiled languages Creates programs that execute directly Translates from English into a code file. Liker Program used to incorporate functions to the program Executable (Computer language)


Fortran :Fortran High level language For performing computation large amount of numeric data Complex calculations Poor dealing with texts C. (Computer Programming language) Interacts directly with the CPU Power to perform complex applications More transportable between computers Image Acquisition Digitalization By ADCs (Analog Digital Convertors) Provide location of the scintillation event. Digital location information locates the appropriate pixel into which the gamma event can be recorded. If output is an analog scintillation camera, the energy pulse has been analyzed by PHA & determined within the selected energy range.


Image Acquisition :Image Acquisition Digital Camera Z pulse is compared with the selected window for PH Analysis. If the Z pulse is within the appropriate window Scintillation event is recorded Each pixel store a limited amount of counts Pixel overflow Image density By the number of counts within the pixel. Prior acquisition Pixel data depth can be selected Pixel containing 1Byte (8bits) (255 counts) 256th not recorded (Information is lost) Most computers 64x64, 128x128, 256x256 or 512x512.


Image Acquisition :Image Acquisition Large field of view camera (400mm) FWHM resolution of 4mm 100 pixels (high resolution image) Static images 256x256 In a bone scan Image resolution deteriorates as the selected acquisition matrix gets smaller Dynamic images Record physiological information. Time per image Blood flow studies of organs (Kidneys) 1frame/sec 64x64 or 128x128 Cardiac studies (rapid physiological phenomena) 25 frames/sec 64x64


Image Acquisition :Image Acquisition Kidney function (many minutes) Frame rates of 20-20 seconds 64x64 or 128x128 Hepatobiliary 1-3min/frame 128-128 or 256-256 ((high count density) Blood pool studies are very similar to SPECT Size and storage format Whole body images (digital) High resolution matrix 512 pixels array (Minimum) Small organs (Heart & Thyroid) Hardware magnification (Zoom) Improve resolution X and y signals are amplified to fill the image matrix The outside perimeter is lost Zooming ↑ resolution ↓ counts per pixel = noisier image


Image Acquisition :Image Acquisition Increase the size of the heart SPECT Myocardial Perfusion (Myocardium) Bone scan (Small details ) RVG (Radionuclide Ventriculogram) Dynamic data acquisition of the heart cycle MUGA or ERNA 16-32 images For a 24- frame study (heart rate of 60) Each frame 42 milliseconds Count rate of a typical cardiac study is 10,000 to 20,000 Counts/sec 64x64 or larger matrixes Arrhythmia Data is compromised by PVCS (Primary Ventricular Contractions) Dual Buffering (Filter bad beats) While 1st beat is evaluated, images from the next beat are placed into the second buffer for RR interval evaluation. Data acquisition alternates (Saving only good cardiac intervals)


Image Acquisition :Image Acquisition List mode acquisition After acquiring the data, it can be evaluated Desired RR interval can be selected Images can be reconstructed Each event is recorded Timing makers are added to take out arrhythmias Measures and corrects respiration displacement of the ventricle to minimize motion blurring Use the store multispectral energy to perform scatter correction on the dynamic images


Image Display and Processing :Image Display and Processing Each pixel is stored as a byte or word Image is stored and displayed on High Resolution monitor Each pixel Gray scale value (# of counts) Images can be displayed Black on white or vise versa Some systems have assigned 64 shades of Gray Relationship between the number of counts and display intensity is Linear Uniform shading between count levels Exponential Relationship Holds the number of gray scales assigned to low count values while expanding the number of shades of gray assigned to higher pixel counts Provides a background Subtraction Logarithmic relationship More gray levels to low count pixels Allows better appreciation


Image Display and Processing :Image Display and Processing Another technique for image enhancement is the use of color Red Green and Blue can be assigned from 0 to 255 More that 16 million colors Image Algebra Add, Subtract, multiply and Divide Dynamic flow Add an image to improve count density Identify time activity changes within the image Subtraction Numeric value fro pixels (background subtraction) Body background is going to be eliminated from the image Subtraction of one frame from another can create a cardiac stroke image By subtracting the end-systolic image from the end-diastolic image Area of myocardial contractions Parathyroid image Technetium image is subtracted from the thallium image Parathyroid tissue only


Image Smoothing :Image Smoothing Reduce Noise from the random effects of the radionuclide counting Nine-point smooth Filtering technique Modify a specific pixel value according to its neighbors 3x3 matrix Can be a little beat blurry To filter a dynamic sets Temporal filter Gated cardiac images Removes noise without a loss of spatial resolution Cinematic Display Continuous-loop movie Information is saved in the buffer to be retrieve (disk) Kidney Studies


Image Quantization :Image Quantization ROI program Display or print counts within the region Number of pixels Counts per pixel Identify the edge of the organ Ex: to see the renal cortex Renal pelvis is subtracted from a region defining the whole kidney Curves Useful information in evaluating the accumulation and washout radiopharmaceutical from the kidney. Demonstrate diagnostic information Normalization Measurement is brought to a standard Two images with different maximum counts may have their intensities normalized if the image with the lowest maximum counts is multiplied so that the maximum count matches the maximum counts of second one. ROI or Curves


Emission Computed Tomography :Emission Computed Tomography Emission Computed Tomography (ECT) is a general term describing the reconstruction of three-dimensional image volumes derived from one of two techniques. Single Photon Emission Computer Tomography SPECT or Positron Emission Tomography PET. These techniques are similar in that they acquire information from different projections This projection information from around the patient is used to determine mathematically the three-dimensional distribution within the body.


SPECT :SPECT SPECT imaging is performed by obtaining planar images with the scintillation camera from may angles around the patient. Images are acquired from 360 degrees, except in myocardial perfusion studies, where 180 degree right anterior oblique to left posterior oblique images over the anterior chest are acquired. Images are acquired in 64x64 resolution for most studies for single detector cameras or low count images from multiple detector systems, and 128x128 resolution images can be acquired on high resolution studies.


Back & Filtered Back-Projection :Back & Filtered Back-Projection Back-projection produces a streak or star artifact that results from data being laid onto the slice image from various projections. The filtered back-projection reduces the streak artifact. In the reconstruction process a frequency space filter is used to modify the projection data, in essence creating negative values on each side of areas of increased count. These negative numbers, when combined with positive values, cancel each other out, thereby eliminating streak artifacts.


Frequency Filters :Frequency Filters Filters are mathematical formulas that generate the curve shape, and cutoff values determine the drop-off point of the filter. Cutoff frequency is a parameter used to generate and characterize filter shapes and may be measured in cycles/pixel, cycles/mm or just millimeters. The purpose of these filters are to increase the amplitudes of the object frequencies and reduce the amplitude of the high frequencies. The Ramp filter is the higher resolution filter, but it also significantly multiplies high frequencies, producing a noisy image. There is a group of filters classified as low-pass filters which let low frequencies through such as Von Hann, Hamming, Butterworth and Parzen.


Type of Filters :Type of Filters


Iterative Reconstruction Algorithms :Iterative Reconstruction Algorithms Most algorithms provide clinically useful images after a number of iterations. Iterative algorithms consist of computing a series of improving images of 3D distribution of activity. There are specific categories of iterative algorithms, such as Maximum Likelihood (ML), Expectation Maximization (EM), conjugate gradient, and Maximum a Priori (MAP). The most commonly used is the ordered-subset expectation maximization (OSEM) algorithm. OSEM is an EM technique that evaluates subsets of projections in order to calculate the 3D volume more quickly than calculating values in every pixel from all projections.


Clinical Applications :Clinical Applications Clinical application programs designed specifically for use in the hospital can be written using a programming language such as C or by using a Macro Protocol. A Macro is a chain of simple computer operations that are combined to form a practical and meaningful method of evaluating image data. Workstations are multitasking computers with graphical user interface. Non-imaging Computer Applications are commercial software programs that process studies and patient data such Unit Dose Manager. Network is the connection of two or more computers that share, store, and edit data between system Standard networking protocol is the Ethernet followed by the host computer, host computer, and a bus computer.


The Information SuperhighwayWorld Wide Web :The Information SuperhighwayWorld Wide Web


Summary :Summary CPU regulate the system operation, interact with memory and coordinate the control of O/I devices Fundamental building block is the transistor ROM: read only memory RAM: random access memory I/O devices: bus, keyboard, monitor, mouse, and printer Care and quality assurance A filter-back projection creates negative values on the sides of the high-count areas that cancel positive values and remove the star artifacts. Linear :Number of counts is equivalent to the intensity Logarithmic: assigns more gray levels to low count pixels Exponential: Provides background subtraction by restraining low counts.


Summary :Summary Using list mode acquisition: Desired RR interval can be selected, Images can be reconstructed, each event is recorded, timing makers are added to take out arrhythmias & measures and corrects respiration displacement of the ventricle to minimize motion blurring Desired RR interval can be selected, Images can be reconstructed Each event is recorded, timing makers are added to take out arrhythmias Measures and corrects respiration displacement of the ventricle to minimize motion blurring Emission Computed Tomography (ECT) is a general term describing the reconstruction of three-dimensional image volumes derived from one of two techniques The filtered back-projection reduces the streak artifact


References :References M.Waterstram-Rich, Paul E. Christian & Kristen. "Nuclear Medicine and PET/CT Technology and Techniques." Christian, Paul E. Nuclear Medicine and PET/CT Technology and Techniques. Salt Lake City, Utah: Patricia Tannian, 2007. 241-248 Radiological Society of North America. Radiology Info. 2008. 21 9 2008 http://www.radiologyinfo.org/en/about/index.cfm?pg=abt_copyrt&bhcp=1 Researchsoft, ISI. IOP Electronic Journals. 6 12 2008. 1 10 2008 .


Questions :Questions What CPU means and name its components Write the equivalent of the following 8 bits= 2 bytes= Name three input/output devices List four care and quality assurance T/F: A workstation is a system that allows the communication between several computer such as PACS, Acquisition Computers, and RIS. How is a 360-degree right anterior oblique to left posterior oblique image over the anterior chest images of a myocardial perfusion study is acquired? What is a filter-back projection? Explain Linear, logarithmic and exponential relationships Explain how to use curves when processing an image. List at least three benefits of using list mode acquisition.


Answers :Answers Central Processing Units (CPU). Control Unit and Arithmetic Logic Unit 8bits=1byte and 2 bytes=1 word mouse, printer keyboard, and monitor air condition at 700 F, humidity around 50%, voltage, and quality testing False False A filter-back projection creates negative values on the sides of the high-count areas that cancel positive values and remove the star artifacts. Linear :Number of counts is equivalent to the intensity Logarithmic: assigns more gray levels to low count pixels Exponential: Provides background subtraction by restraining low counts. 9. Explain 10. Desired RR interval can be selected, Images can be reconstructed Each event is recorded, timing makers are added to take out arrhythmias Measures and corrects respiration displacement of the ventricle to minimize motion blurring