CT Imaging and Photon Counting Detectors

<p>-1000 HU (D)</p> Signup and view all the answers

<p>Both A and B (D)</p> Signup and view all the answers

<p>By counting the number of X-ray photons instead of integrating their energy. (D)</p> Signup and view all the answers

<p>To adjust the contrast and brightness of the image. (A)</p> Signup and view all the answers

<p>They allow for the measurement of X-ray photon energy. (D)</p> Signup and view all the answers

<p>By defining a detection threshold to exclude low-energy signals. (B)</p> Signup and view all the answers

<p>To convert X-rays into visible light. (D)</p> Signup and view all the answers

<p>It allows for the weighting of low-energy photons to enhance contrast. (A)</p> Signup and view all the answers

<p>A helical CT scanner takes a series of images in a spiral pattern, while a multi-slice CT scanner takes multiple images simultaneously. (C)</p> Signup and view all the answers

<p>The linear attenuation coefficient divided by the density of water. (C)</p> Signup and view all the answers

<p>A few kilohertz (A)</p> Signup and view all the answers

<p>SiO2 (C)</p> Signup and view all the answers

<p>Reduced radiation dose to the patient. (A)</p> Signup and view all the answers

<p>Quantum noise (C)</p> Signup and view all the answers

<p>Focal spot size (B)</p> Signup and view all the answers

<p>Helical pitch (D)</p> Signup and view all the answers

<p>Smaller focal spots lead to higher spatial resolution (D)</p> Signup and view all the answers

<p>Voxel size can be larger than the spatial resolution if computational efficiency is prioritized (C)</p> Signup and view all the answers

<p>Blurring caused by the continuous rotation of the tube-detector system, increasing with distance from the center of rotation (B)</p> Signup and view all the answers

<p>To enhance high frequencies for sharper images or suppress high frequencies for noise reduction (D)</p> Signup and view all the answers

<p>The size of the detector channels (C)</p> Signup and view all the answers

<p>A short movement of an object (C)</p> Signup and view all the answers

<p>Gradual movement, such as cardiac motion (A)</p> Signup and view all the answers

<p>They are caused by large helical pitch or small reconstruction intervals. (D)</p> Signup and view all the answers

<p>A z-aliasing artifact occurring primarily in helical cone-beam CT. (D)</p> Signup and view all the answers

<p>Occurs primarily due to beam hardening and limited spatial resolution. (A)</p> Signup and view all the answers

<p>When the detector efficiency changes between calibration and measurement. (D)</p> Signup and view all the answers

<p>The presence of metal implants and beam hardening. (B)</p> Signup and view all the answers

<p>It can result in stairstep artifacts during reconstruction. (D)</p> Signup and view all the answers

<p>It increases SNR and increases patient dose. (A)</p> Signup and view all the answers

<p>Attenuation properties. (B)</p> Signup and view all the answers

<p>Aliasing. (A)</p> Signup and view all the answers

<p>It results in the preferential absorption of low-energy photons. (B)</p> Signup and view all the answers

<p>Up to 30%. (B)</p> Signup and view all the answers

<p>They yield streak artifacts. (D)</p> Signup and view all the answers

<p>It averages intensity across the beam width. (D)</p> Signup and view all the answers

<p>CT scans create projection images of thin body slices. (D)</p> Signup and view all the answers

<p>To focus the X-ray beam into a thin slice (A)</p> Signup and view all the answers

<p>The X-ray beam is attenuated differently by different tissues (A)</p> Signup and view all the answers

<p>Parallel-beam geometry uses a narrower X-ray beam than fan-beam geometry. (C)</p> Signup and view all the answers

<p>Linear tomography was developed before the invention of computed tomography. (A)</p> Signup and view all the answers

<p>CT produces three-dimensional images, while conventional radiography produces two-dimensional images. (C)</p> Signup and view all the answers

<p>Axial transverse tomography rotates the patient and the film, while linear tomography moves the patient and the film in opposite directions. (D)</p> Signup and view all the answers

<p>Because it uses a computer to generate the images. (D)</p> Signup and view all the answers

<p>CT scans can be used to diagnose a wider range of medical conditions than conventional X-rays. (B), CT scans provide more detailed information about bone fractures than conventional X-rays. (C)</p> Signup and view all the answers

<p>Greek words for 'slice' and 'to write' (D)</p> Signup and view all the answers

<p>Scanning (C)</p> Signup and view all the answers

<p>Conical-beam geometry (A)</p> Signup and view all the answers

<p>CT scans provide detailed cross-sectional images, enhancing the visibility of small differences in tissue density. (C)</p> Signup and view all the answers

<p>It stands for 'Computed Axial Tomography' and highlights the use of axial imaging in the technique. (D)</p> Signup and view all the answers

<p>All of the above. (D)</p> Signup and view all the answers

<p>It produces blurred images of sharp features. (D)</p> Signup and view all the answers

<p>It can construct images while data are being collected. (A)</p> Signup and view all the answers

<p>Radial projection (B)</p> Signup and view all the answers

<p>To remove frequency components causing blurring. (D)</p> Signup and view all the answers

<p>Differences in measurements are integrated into the appropriate elements. (B)</p> Signup and view all the answers

<p>Filtered backprojection (C)</p> Signup and view all the answers

<p>One-dimensional integral equation (B)</p> Signup and view all the answers

<p>Algebraic reconstruction technique (C)</p> Signup and view all the answers

<p>They use direct conversion materials for higher charge production. (A)</p> Signup and view all the answers

<p>By precisely counting individual photons instead of averaging. (A)</p> Signup and view all the answers

<p>It is susceptible to introducing electronic noise. (D)</p> Signup and view all the answers

<p>96% (A)</p> Signup and view all the answers

<p>The electronic noise generated is inherently higher. (C)</p> Signup and view all the answers

<p>The size of the focal spot (D)</p> Signup and view all the answers

<p>They enhance the count and energy measurement of X-ray photons. (C)</p> Signup and view all the answers

<p>Quantum noise (A)</p> Signup and view all the answers

<p>It reduces the influence of electronic noise on the detected signals. (A)</p> Signup and view all the answers

<p>Detector channel size affects channel-to-channel crosstalk (C)</p> Signup and view all the answers

<p>The area fill fraction of the septa. (A)</p> Signup and view all the answers

<p>It increases linearly with distance from the center of rotation (A)</p> Signup and view all the answers

<p>It may determine the spatial resolution instead (C)</p> Signup and view all the answers

<p>Statistical noise (D)</p> Signup and view all the answers

<p>The focal spot size and detector cell size (D)</p> Signup and view all the answers

<p>To enhance or suppress image frequencies (D)</p> Signup and view all the answers

<p>EMI scanner technology (C)</p> Signup and view all the answers

<p>A range depending on tissue composition (D)</p> Signup and view all the answers

<p>To convert X-rays into visible light (C)</p> Signup and view all the answers

<p>The energy of the absorbed X-rays (B)</p> Signup and view all the answers

<p>To define the displayed gray level interval (B)</p> Signup and view all the answers

<p>Bone's CT number varies due to its composition (D)</p> Signup and view all the answers

<p>512 × 512 (D)</p> Signup and view all the answers

<p>Photodiode (D)</p> Signup and view all the answers

<p>Increases SNR, reducing relative quantum noise (A)</p> Signup and view all the answers

<p>The various physical factors such as beam hardening and scatter (A)</p> Signup and view all the answers

<p>Sharp edges in projections being poorly approximated (C)</p> Signup and view all the answers

<p>It causes a beam to become less attenuated as it interacts with tissues (A)</p> Signup and view all the answers

<p>About 30% (B)</p> Signup and view all the answers

<p>The averaging of intensity over finite beam width (B)</p> Signup and view all the answers

<p>Streak artifact (C)</p> Signup and view all the answers

<p>It reduces the perceptibility of low-contrast details (C)</p> Signup and view all the answers

<p>Conventional radiography produces a 2D image, while CT produces a series of cross-sectional images that can be reconstructed into a 3D image. (D)</p> Signup and view all the answers

<p>Greek words for 'slice' and 'writing' (B)</p> Signup and view all the answers

<p>A single X-ray beam is used to create a 2D image. (A)</p> Signup and view all the answers

<p>CT scans use specialized algorithms to reconstruct cross-sectional images, enhancing the visualization of subtle differences in tissue density. (D)</p> Signup and view all the answers

<p>Axial transverse tomography produces a series of cross-sectional images, while linear tomography produces a single image of a specific plane. (A)</p> Signup and view all the answers

<p>Fan-beam geometry allows for faster data acquisition. (A)</p> Signup and view all the answers

<p>A mathematical algorithm is used to process the line attenuation measurements taken at various angles, reconstructing the 3D image. (A)</p> Signup and view all the answers

<p>Susceptibility to electronic noise from the transimpedance amplifier (A)</p> Signup and view all the answers

<p>Significantly higher charge production per X-ray photon (A)</p> Signup and view all the answers

<p>By eliminating electronic noise through careful thresholding and counting individual photons (D)</p> Signup and view all the answers

<p>They can measure the energy of individual X-ray photons (B)</p> Signup and view all the answers

<p>They improve CNR by reducing the influence of electronic noise, resulting in cleaner images (C)</p> Signup and view all the answers

<p>By limiting the area fill fraction, decreasing the overall collection efficiency (D)</p> Signup and view all the answers

<p>They detect the charge produced by each photon, allowing for discrimination based on energy (D)</p> Signup and view all the answers

<p>Radon Transform (C)</p> Signup and view all the answers

<p>It is a 2D dataset created by stacking projections of the object at different angles. (A)</p> Signup and view all the answers

<p>Because the projection profiles measured at opposite sides are redundant. (C)</p> Signup and view all the answers

<p>The attenuation profile is the logarithm of the measured intensity profile. (C)</p> Signup and view all the answers

<p>Because the projection process involves line integrals along different angles. (C)</p> Signup and view all the answers

<p>The angle of the X-ray beam and the distance from the origin. (C)</p> Signup and view all the answers

<p>It is used to separate the frequency components of the attenuation pattern. (D)</p> Signup and view all the answers

<p>To convert the measured projection data into a sinogram. (B)</p> Signup and view all the answers

<p>Filtered backprojection (C)</p> Signup and view all the answers

<p>It produces blurred images of sharp features in the object. (B)</p> Signup and view all the answers

<p>To remove or reduce the blurring inherent in the backprojection process. (D)</p> Signup and view all the answers

<p>Simple backprojection reconstructs the image directly from the raw data, while filtered backprojection uses a deblurring function to reduce blurring before backprojection. (B)</p> Signup and view all the answers

<p>FFT (fast Fourier transform) (A)</p> Signup and view all the answers

<p>By iteratively comparing attenuation data at different angles and adjusting corresponding elements in the image. (B)</p> Signup and view all the answers

<p>The x-ray attenuation data is used to calculate the CT numbers, which are then assigned to corresponding pixels to form the reconstructed image. (A)</p> Signup and view all the answers

<p>Ability to reconstruct images from incomplete data sets or with lower radiation doses. (A)</p> Signup and view all the answers

<p>Focal spot size (B)</p> Signup and view all the answers

<p>NaCl (D)</p> Signup and view all the answers

<p>The width of the displayed gray level interval (D)</p> Signup and view all the answers

<p>Convert visible light into an electrical signal (D)</p> Signup and view all the answers

<p>The composition and structure of bone vary, affecting its attenuation. (B)</p> Signup and view all the answers

<p>They allowed for faster scanning and higher spatial resolution. (C)</p> Signup and view all the answers

<p>The CT number is directly proportional to the linear attenuation coefficient. (C)</p> Signup and view all the answers

The reduction of X-ray intensity as it passes through materials, crucial for CT imaging.

The ability to distinguish small details in an image; affected by focal spot size and detector channel size.

The area on the anode where electrons hit, originating the X-rays; impacts image quality.

Blurring that increases with distance from the center of rotation during continuous rotation of the tube-detector.

A filter in image reconstruction that sharpens high frequencies or reduces noise in CT images.

The 3D equivalent of a pixel, chosen smaller than system resolution for accurate imaging.

Statistical noise in CT primarily from the nature of X-ray photons, represented by a Poisson distribution.

Includes quantum noise, electronic noise, and round-off noise that affect image quality in CT.

An imaging modality producing cross-sectional images based on X-ray attenuation.

Derived from Greek meaning 'to write slices', it refers to imaging techniques that produce slice images of objects.

Device that produces X-rays, essential for CT imaging.

Reduction of the intensity of X-rays as they pass through the body, critical in CT image formation.

Measures the X-ray intensity after it has been attenuated by the patient.

A scanning technique in CT where X-rays spread in a fan-like shape across the patient's body.

A type of tomography where the X-ray source and film move at constant speed in opposite directions.

A CT technique where the film is positioned horizontally and both patient and film rotate around a vertical axis.

The plane in focus during CT rotation, while others are averaged out.

The first CT scanner, developed by Godfrey Hounsfield in 1972.

CT numbers reflecting tissue density, used for imaging analysis.

A measure related to the absorption of X-rays by different tissues.

A technique to optimize the gray level display in CT imaging.

Material converting X-rays into visible light in CT detectors.

CT detectors that generate electric current from scintillations.

CT technology introduced in 1998, enabling multiple slices at once.

Ratio that compares the level of a desired signal to the level of background noise.

The difference in shading between an object and its background, influenced by attenuation.

Technique to enhance displayed image contrast in digital images.

Taking insufficient detector samples leading to artifacts like aliasing.

Phenomenon where low-energy photons are absorbed more, causing the beam to harden.

Photons deviating from their original path, causing inaccuracies in intensity measurements.

Effect caused by finite beam width leading to averaged intensity measurements.

Inconsistent measurements caused by small movements of an object during acquisition.

Visible lines resulting from object movement during imaging, causing distortion.

Blurred representation of moving parts from gradual movements like the heart.

Artifacts in helical CT due to large helical pitch or small reconstruction intervals.

Z-aliasing artifact with a pattern like spokes due to cone-beam CT interpolation.

Artifacts caused by poor calibration or detector failure during imaging.

Artifacts from beams hardening and scattering caused by metal implants.

Overestimation of calcified plaque size caused by beam hardening and resolution limits.

Materials that produce light when absorbing radiation, enabling detection.

The percentage of radiation absorbed by a detector material, indicating its effectiveness.

A semiconductor device that converts light into an electrical current.

A system that collects and processes data from detectors to produce readable signals.

An electronic device that converts current from a photodiode to voltage.

Unwanted signals that interfere with the detection and processing of useful signals.

Devices that count individual photons and detect their energy, improving CNR.

The ability of a detector to determine the charge related to each photon impact, improving accuracy.

A measure of how much a material can attenuate X-rays, varies with tissue type.

A value representing tissue density in Hounsfield Units (HU), affects image quality.

A technique to optimize image contrast by adjusting the range of displayed gray levels.

Technique that allows visualization of structures in three dimensions using CT data.

Advanced imaging that includes time as a factor, showing motion within a scan.

An imaging modality producing cross-sectional images using X-ray attenuation.

The term tomography derives from Greek words meaning 'to write slices'.

An array of detectors that measure X-ray intensity after attenuation by the patient.

The method of reconstructing the actual attenuation at each point from measurements taken at various angles.

Computed tomography originated in the late 20th century, building on earlier imaging technologies.

The process of creating a spatially correct image from x-ray data using techniques like backprojection.

A method where x-ray paths are divided into elements, summing their contributions to create an image, but often blurs sharp features.

An advanced technique that uses a filter to remove blurring from x-ray data before reconstructing the image.

In image reconstruction, it’s where a deblurring function is combined with x-ray data to improve image clarity.

A reconstruction method where x-ray data from different angles are compared and combined to refine image quality.

A variation of series expansion that refines images using data from multiple angles to enhance details.

A series expansion method that minimizes the error between the estimated image and actual data.

A series expansion technique that refines image reconstruction by simultaneously processing data from multiple angles.

The amount of radiation received by the patient during imaging; affects noise and SNR.

Characteristics that determine how much radiation an object can absorb or scatter.

A process that adjusts pixel brightness in digital images to enhance contrast.

A phenomenon caused by undersampling, resulting in distorted or misrepresented images.

The width of the X-ray beam influenced by focal spot and detector size.

The dimensions of the individual channels in a CT detector, affecting resolution.

Elements influencing clarity in CT images, including focal spot size and voxel size.

The method used in backprojection that relies on sample density for image reconstruction.

At close range to the focal spot, its size greatly impacts beam width.

Interference between detector channels that affects image quality.

Including quantum noise, electronic noise, and round-off noise affecting image quality.

Describes the statistical nature of quantum noise measured in CT imaging.

A measure of how well scintillators convert radiation into detectable light.

A method in detectors that counts individual photons rather than integrating their energy.

Materials like CdTe and CZT that directly convert X-rays to electronic charges.

The principle that relates the amount of charge produced to the energy of the incoming X-ray.

The enhancement of contrast-to-noise ratio achieved by photon counting detectors.

A predefined limit that improves signal detection by eliminating electronic noise effects.

Unwanted signals that interfere with capturing actual photon signals in detectors.

Assigning greater importance to lower-energy X-ray detection to boost contrast.

Value representing tissue density in imaging; varies with composition and structure.

Scintillators have high optical quality for efficient light transfer and high absorption efficiency.

Detectors quantify the charge per X-ray, enhancing energy detection accuracy.

A measure of how effectively scintillators absorb radiation, typically around 96%.

The overall clarity and detail in CT images, influenced by several factors.

Voxel size impacts spatial resolution; smaller sizes provide finer detail.

Process where data from different angles combine for accurate image creation.

Sources of noise like quantum and electronic noise that degrade image quality.

Blurring caused by rotational motion, particularly at image edges, affecting quality.

Different methods of reconstructing images, including simple and filtered types for better results.

CT images are produced by X-ray attenuation measured at various angles.

Detectors that directly convert X-rays into electronic signals for CT imaging.

A mathematical transformation that converts a function into its sinogram in CT imaging.

A 2D dataset that results from stacking projections of a function obtained at different angles.

Represents the intensity profile of X-ray beams for a specific angle in CT.

The angle at which X-ray beams are measured relative to the patient.

The maximum rate that a detector can accurately count incoming X-ray photons.

The measurement of X-ray intensity received at different positions (r) during imaging.

A method to separate X-ray attenuation patterns into frequency components for analysis.

Mathematical methods for creating images from X-ray data in CT.