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CT Final

Computed Tomography physics final

QuestionAnswer
The mathematical techniques used by the computer to reconstruct the computed tomography image are known as: a. Image reconstruction algorithms b. Computer programs c. Reformations d. pattern recognition A- Image reconstruction algorithms
Which imaging communication protocol is used with picture archiving and communications systems? a. health level b. digital imaging and communications in medicine c. hospital information system d. radiology information system B- digital imaging and communications in medicine
The approaches to secondary storage (archiving) can be categorized as all of the following except: a. Online b. Broadline c. Offline d. Nearline B- Broadline
Data acquisition refers to: a. collecting x-ray transmission readings from the patient b. subjecting data to computer processing c. changing the data before they are displayed on a monitor d. storing the data from the patient to mag tapes or disks A- collecting x-ray transmission readings from the patient
True/False: Aliasing results in an artifact that appears as a moiré pattern in the image. True
Which of the following is best used to describe patient dose in computed tomography? a. CTDI and MSAD b. isometric curves c. exposure doses d. collective doses A- CTDI and MSAD
True/False: Processing images by computer is referred to as digital image processing. True
Which type of artifact will appear on a digital image as a result of poor sampling of the analog signal? a. beam hardening b. partial volume c. aliasing d. poor sampling does not create artifacts C- aliasing
True/False: Isodose curves are a dose descriptor used in reporting radiation doses in computed tomography. True
True/False: Digitization consists of three steps: scanning, sampling and quantization. True
If the field of view for an examination is 30 cm and the matrix size is 512 x 512, what is the approximate pixel size? a. 0.06 mm b. 30 mm c. 0.3 mm d. 0.59 mm D- 0.59 mm
The main purpose of a filter used in computed tomography is to: a. decrease the mean energy at the detector b. reduce the intensity of the beam at the detector c. make the beam less uniform at the detector d. protect the patient D- protect the patient
Which of the following refers to the size, shape, motion, and path traced by the x-ray beam as it scans the patient? a. detector tracing b. data acquisition c. beam geometry d. projection profile c. beam geometry
The reduction of the intensity of a beam of x rays as it passes through the patient is: a. the linear attenuation coefficient b. attenuation c. the natural logarithm d. the relative transmission value b. attenuation
Which of the following represents the correct expression of Lambert Beer’s law? a. I = Ioe +µb b. I = Ioe –µ c. I = Ioe –µx d. Io = Ioe –µa c. I = Ioe –µx
How many pixels make up a computed tomography image whose matrix size is 512 x 512? 262,144
Attenuation of a beam of radiation depends on: I. the atomic number II. the electrons per gram of tissue III. the size of the anode I and II
The most obvious difference between CT and radiography is: a. decreased visualization of artifacts b. increased spatial resolution c. CT shows cross sectional anatomy or trans-axial anatomy d. decreased patient dose c. CT shows cross sectional anatomy or trans-axial anatomy
A computed tomography image of 12 bits per pixel means: a. each pixel can have a total of 4096 shades of gray b. the pixel size is 12 mm c. the voxel size is 12 mm d. the matrix is 4096 x 4096 a. each pixel can have a total of 4096 shades of gray
True/False: The window width controls the image contrast and the window level controls the image brightness. True
The computed tomography gantry houses all of the following except: a. collimators b. the x-ray tube and generator c. the detector electronics d. the central processing unit d. the central processing unit
All of the following are categories of computed tomography software except: a. detector software b. image postprocessing software c. preprocessing software d. reconstruction software a. detector software
he couch top (table top) of a computed tomography scanner table should have the following: I. low radiation absorption characteristics II. made of carbon fibers III. excellent vibration-damping features d. I, II, and III
The computer system receives _________ data from the data acquisition system. a. analog b. digital c. manipulated d. hard copy b. digital
Calculate the pitch of a 16 channel scanner using all 16 slices, 0.75 detector slice thickness and a table speed of 6mm per rotation. a. 0.5 b. 1.2 c. 1.0 d. 0.8 a. 0.5
As the window width increases, picture contrast: b. decreases
The purpose of the imaging system is to: I. produce x rays II. shape and filter the x ray III. detect and measure the radiation passing through the cross-section I, II, and III
A helical scan with a 25 second total acquisition time, 1 second rotation, 1.2mm slice thickness, 5 slices per rotation with a pitch of 1 covers how much anatomy? a. 760 mm b. 150 mm c. 104 mm d. 480 mm b. 150 mm
If you have a image matrix of 1024 and 400 images on a 12 bit system, how much storage is required? a. 4.9 MB b. 5,033 MB c. 35 MB d. 629 MB d. 629 MB
What is the most satisfactory window (soft tissue) for a general survey of the abdomen out of the choices below? a. 400 ww & 40 wl b. 40 ww & 400 wl c. -500 ww & 50 wl d. 500 ww& -100 wl a. 400 ww & 40 wl
What term describes how thick a section is imaged and to what extent details within the section contribute to the signal? a. detector profile b. collimation profile c. data acquisition profile d. slice sensitivity profile d. slice sensitivity profile
Partial volume artifacts can be reduced with _____________ slice acquisitions and computer algorithms. thinner
What is/are the unit(s) of exposure? I. Roentgen (R) II. Sievert (Sv) III. coulomb per kilogram (C/kg). I and III
To sharpen the image, a(n) ___________ process is applied to modify the frequency contents of the projection before back-projection. a. convolution b. accuracy c. resolution d. noise a. convolution
True/False: Low-contrast resolution can be measured with phantoms that contain low-contrast objects of different sizes. True
True/False: The ideal pitch in spiral/helical computed tomography is 2:1. False
In-plane resolution is measured in terms of: I. line pairs/centimeter II. line pairs/millimeter III. line pairs/inch I and II
Examples of stochastic effects include: I. cancer II. leukemia III. erythema I and II
The pitch ratio is expressed as: distance the table travels during 360 degrees/slice thickness
True/False: The measured radiation dose is inversely proportional to the number of detector rows. True
The maximum fluoroscopy time for continuous imaging is: 100 seconds
If the x-ray prepatient collimation width is 24 mm and the scanner has a four-row detector array, what is the detector row collimation? 6 mm d = (24/4)
True/False: A pitch greater than 1 will result in an increased dose True
True/False: The size of the needle and site of injection are not important during a computed tomographic angiography examination. Flase
Computed tomography screening has been used in all of the following except: a. breast screening b. colon screening c. lung cancer screening d. whole-body screening of healthy patients a. breast screening
What term is used to describe the resorting of the three-dimensional data collected from the cone-beam acquisition to a set of two-dimensional fan-beam data? a. binning b. rebinning c. reformatting d. sampling b. rebinning
The definition of pitch in a multislice scanner, as defined by the International Electrotechnical Commission, states: P = distance the table travels per rotation (d)/total collimation (W)
The computed tomography detector consists of: I. radiation sensors II. suitable electronics III. photodiode I, II and III
What type of detector is used in multislice computed tomography scanners? solid-state scintillation detector
Which visualization tool is the most frequently used in computed tomographic angiography examinations to display the structure of vessels? maximum intensity projection (MIP)
Clinical examples of positron emission tomographic imaging include: I. cardiac studies II. epilepsy studies III. oncology studies I, II and III
True/False: Only some of the information collected from the voxels that compose each of the scanned slices goes to the computer for image reconstruction. False
Clinical applications of three-dimensional imaging in computed tomography include all of the following except: a. craniomaxillofacial complex b. endocrine system c. gastrointestinal system d. pulmonary system b. endocrine system
The processing of an object-based model into a simulated three-dimensional image involves: I. object delineation II. rendering III. segmentation I, II and III
Virtual endoscopy allows the viewer to “fly through” structures such as: I. colon II. tracheobronchial tree III. vessels I, II and III
he fourth dimension involved in four-dimensional angiography is ____________. opacity
True/False: Most experts agree that surface rendering is not best suited for use in computed tomography virtual reality imaging. True
The next step after data acquisition that is intended to optimize the images before they are subject to further processing and analysis is: image preprocessing
The most commonly used radiopharmaceutical for positron emission tomographic imaging is: 18 F-2-fluoro-2-deoxy-D-glucose (FDG)
Three-dimensional rendering algorithms include: I. virtual rendering II. surface rendering III. volume rendering II and III
T/F: Quality control tests that are effective must be objective, quantitative, and easy and can be done very quickly. True
By modeling noise properties and the scanned object first, the following limitations due to noise in the reconstructed image are overcome except: a. lower dose exams b. large patients c. thin slices d. decreased pitch d. decreased pitch
Image acquisition is primarily obtained in the ___________ plane. Axial
Which tests the performance of a computed tomography scanner on a number of parameters and compares the performance with a standard? a. quality administration b. quality assurance c. quality control d. quality maintenance c. quality control
The tolerance limit for a computed tomography number calibration quality control test is: +- 3 CT numbers
manufactures offer these IR algorithms commercially except: a. iterative methods w/out modeling b. statistical methods w/ modeling of photon counting statistics. c. FBP algorithm d. model-based methods, that exceed statistical modeling c. FBP algorithm
Studies requiring reformatted images are acquired with ________ slices. Thin
Which is not a primary goal of IR algorithms? a. Reduce image noise with lower exposure technique b. Preserve spatial resolution at lower exposure techniques c. Reduce photon starvation artifact d. Reduce artifacts caused by patient motion d. Reduce artifacts caused by patient motion
What term describes the difference between the simulated raw data and measured projection raw data? a. model b. Projection c. Correction term d. Algorithm c. Correction term
Limitations presented by filtered back projection (FBP) algorithm include each of the following except: a. image noise b. artifact creation c. patient dose d. speed d. speed
Scheme that uses 3 elements to keep dose to a minimum during data acquisition: combined applications to reduce exposure, new ultra-fast ceramic detectors, on-line dose modulation
Dose descriptors are: MSDP, SSDP, CTDI, MSAD, and isodose curves
examples of magnetic storage floppy and hard disks
Define optical disk storage uses laser beam to write information on CD-ROM
The coordinate system (4 coordinates): Scanner, Scene, Object, Display
Major OS used in CT include: UNIX, MS windows NT and XP OS
what is the pixel size formula? pixel size= FOV/matrix size
another word for ADC digitizer
Pre-processing (with ADC/digitizer) includes what scanning, sampling, quantization
define spacial domain analog, a smooth sine wave of conventional radiograph
define frequency domain digital, a sine wave made of straight lines I's and O's (accomplished by fourier transform)
another name for HU numbers relative transmission values
HU are calculated using what? Lambert Beer's Law
What does Lambert Beer's law find? A linear attenuation coefficient
A group of rays is a ........ projection
in 4th generation scanner the tilting action of the detector ring is referred to as.... nutating
the result of preprocessing of the signals from the detectors is called...... raw data
another name for approximate cone-beam altorithms rebinning
what includes contrast enhancement, histogram stretching, histogram modification, contrast stretching or simply windowing Alias'
changing scan parameters can affect image contrast
shading appears next to dense object due to beam hardening
what compares the performance of different CT systems MTF or modulation transfer function
what can be used to generate a MTF PSF or point spread function
in MTF as the magnitude decreases the frequency of the bar pattern ........ increases
What is SSP/Slice sensitivity profile cross plane/z axis spacial resolution
Dose descriptors include (5) SSDP, MSDP, CTDI, MSAD, Isodose curves
What was the first dose descriptor and what is it MSAD it is the average from all the bell shaped dose curves summed
what is effective mA the mAs per slice in multi-slice CT
what is the formula for effective mA effective mA= true mAs / pitch
Created by: rreilly2