What is motion degradation mean?
What is motion degradation mean?
Motion degradation in MRI can be attributed to macroscopic motion that encompasses both 1) physiological motion, from respiration, cardiac pulsations or peristalsis and 2) involuntary subject movement during the scan.
What is a motion artifact in an MRI?
Phase-encoded motion artifact is one of many MRI artifacts occurring as a result of tissue/fluid moving during the scan. Motion that is random such as the patient moving produces a smear in the phase direction. Periodic motion, such as respiratory or cardiac/vascular pulsation, produces discrete, well-defined ghosts.
What causes motion artifact?
Motion artifacts are related to cardiac motion which are caused by cardiac pulmonary or body motion and can cause blurring or double images. Fast CTA scanners having more X-ray sources can reduce the motions artifacts since the patient has less time to move during the image acquisition (Fleischmann and Boas, 2011).
What does mild motion artifact mean?
Motion artifact is a patient-based artifact that occurs with voluntary or involuntary patient movement during image acquisition. Misregistration artifacts, which appear as blurring, streaking, or shading, are caused by patient movement during a CT scan.
How do you reduce motion artifacts?
Reducing Motion Artifacts
- Minimize the degree of motion. a. The importance of simple instruction/education of the patient to hold still while the scanner is making noise should not be underestimated.
- Suppress signal from moving tissues. a.
- Adjust imaging sequences and parameters. a.
- Detect and compensate for motion.
What is motion artifacts in ECG?
Electrocardiographic artifacts are defined as electrocardiographic alterations, not related to cardiac electrical activity. As a result of artifacts, the components of the electrocardiogram (ECG) such as the baseline and waves can be distorted. Motion artifacts are due to shaking with rhythmic movement.
What are motion artifacts TV?
Display motion blur, also called HDTV blur and LCD motion blur, refers to several visual artifacts (anomalies or unintended effects affecting still or moving images) that are frequently found on modern consumer high-definition television sets and flat panel displays for computers.
What is an artifact in medical terms?
In medical imaging, artifacts are misrepresentations of tissue structures produced by imaging techniques such as ultrasound, X-ray, CT scan, and magnetic resonance imaging (MRI). Physicians typically learn to recognize some of these artifacts to avoid mistaking them for actual pathology.
What means artifact?
1a : a usually simple object (such as a tool or ornament) showing human workmanship or modification as distinguished from a natural object especially : an object remaining from a particular period caves containing prehistoric artifacts.
What does artifact mean on CT scan?
Out of field
What is beam hardening effect?
Beam hardening is the phenomenon that occurs when an x-ray beam comprised of polychromatic energies passes through an object, resulting in selective attenuation of lower energy photons. CT beam hardening artifact has two distinct manifestations, streaking (dark bands) and cupping artifacts.
What is artifact in radiology?
Definition : An artifact is a structure or an appearance that is not normally present on the radiograph and is produced by artificial means. Radiographic errors may be due to technical errors [ errors related to the technique of. taking the radiograph] or processing errors [related to all aspects of processing]
What is photon starvation?
Photon starvation is one source of streak artifact which may occur in CT. It is seen in high attenuation areas, particularly behind metal implants. Because of high attenuation, insufficient photons reach the detector.
What causes photon starvation?
This photon starvation artifact phenomenon occurs frequently when a pelvis or shoulder is scanned with thin slices. The common understanding regarding photon starvation streaks is that they are a manifestation of irregularities caused by noise in the raw data profile.
What is cone beam artifact?
Cone beam effect artifacts are seen in multidetector row CT (cone beam CT) acquisitions 1. Modern CT scanners use more detector arrays to increase the number of sections acquired per rotation. This causes the x-ray beams to become cone-shaped as opposed to fan-shaped 2.
How can I reduce noise in CT?
Noise reduction can occur at various stages of the CT imaging process. In conventional analytic filtered backprojection (FBP)–based reconstruction, a smooth filter is typically applied to control noise.
What is noise CT?
Noise in computed tomography is an unwanted change in pixel values in an otherwise homogenous image. Often noise is defined loosely as the grainy appearance on cross-sectional imaging; more often than not, this is quantum mottle. The higher the ratio, the less noise is present in the image.
What is signal to noise ratio in CT?
It is calculated by comparing the level of the desired signal to the background deviation from normal pixel values. In general, the larger the number of photons transmitted, the greater the SNR.
What is image quality in CT?
CT image quality, as in most imaging, is described in terms of contrast, spatial resolution, image noise, and artifacts. Spatial resolution is ultimately limited by sampling, but both image noise and resolution are strongly affected by the reconstruction filter.
How does mA affect image quality?
An increase in mA will increase the quantity of exposure; decreased mA will reduce the quantity of exposure.
What is the resolution of a CT scan?
Current CT scanners have a spatial resolution of 0.5–0.625 mm in the z-axis, and approximately 0.5 mm in the x- to y-axes. A basic requirement for adequate multiplanar reconstruction is that the resolution is isotropic; eg, the resolution is approximately equal in all directions.
What is SFOV?
SFOV: Scan field of view–the parameter that determines how much anatomy is scanned.
What is voxel in CT scan?
A voxel is the smallest 3D element of the volume,2 and is typically represented as a cube or a box, with height, width and depth.
What is the Matrix in CT?
Matrix: Two dimensional grid of pixels, used to compose images on a display monitor. The matrix determines the number of rows and columns. Partial volume effect: When different tissues/objects are represented by the same voxel. Each tissue/object only partially fills the voxel and is therefore a partial volume.
What is raw data in CT?
Raw data are the values of all measured detector signals during a scan. From these data the CT images are reconstructed including the use of mathematical procedures like convolution filtering and back projection.
What is CT data?
A computerized tomography (CT) or computerized axial tomography (CAT) scan combines data from several X-rays to produce a detailed image of structures inside the body. CT scans produce 2-dimensional images of a “slice” or section of the body, but the data can also be used to construct 3-dimensional images.
What is FOV in CT scan?
Scan Field Of View. (SFOV) The scan field of view is the area being scanned. This selectable scan factor is measured from a CT system isocenter to the most distant located edge of the patient. See also Reconstruction Field Of View.
What is data acquisition system in CT scan?
What is data acquisition? Data acquisition refers to the method by which the patient is scanned to obtain enough data for image reconstruction. What is scanning? The beam geometry, which characterizes the particular CT system and also plays a central role in spatial resolution and artifact production.
Why CT scan modality has separate control console?
Some system designs provide for remote viewing stations in addition to the operating-viewing console station located in the main CT control area. The control area should allow a direct view of the scanning area so the radiographer can monitor the patient throughout the course of the procedure.