Pitch. (p) The pitch (in computed tomography) is the ratio of the patient table increment to the total nominal beam width for the CT scan. The pitch factor relates the volume coverage speed to the thinnest sections that can be reconstructed.
What is detector pitch in CT scan technology?
It has two terminologies depending on whether single slice or multislice CT scanners are used 1-3. The term detector pitch is used and is defined as table distance travelled in one 360° gantry rotation divided by beam collimation 2.
What is the meaning of p pitch in CT?
Pitch (P) is a term used in helical CT. It has two terminologies depending on whether single slice or multislice CT scanners are used 1-3. Single slice CT (SSCT) The term detector pitch is used and is defined as table distance traveled in one 360° gantry rotation divided by beam collimation 2.
What is a high p pitch on a CT scan?
P <1.0: there is x-ray beam overlap; i.e. a volume of tissue is irradiated more than once per scan Thus a pitch >1.0 results in decreased patient dose but also decreased image quality (fewer projections are obtained, resulting in lower SNR). A pitch of <1.0 results in better image quality, but a higher patient dose.
How does pitch affect X-ray image quality?
Choice of pitch affects both image quality and patient dose 2: P >1.0: x-ray beams are not contiguous for adjacent rotations; i.e. there are gaps in the x-ray helix, but the full volume is still irradiated, only with fewer projections per rotation P <1.0: there is x-ray beam overlap; i.e. a volume of tissue is irradiated more than once per scan
What is pitch in CT?
What is detector pitch?
What is beam pitch?
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What is pitch in CT scan?
The pitch in multislice spiral CT is defined as the ratio of the table increment over the detector collimation in this study. In parallel to the current framework for studying longitudinal image resolution, the central fan-beam rays of direct and opposite directions are considered, assuming a narrow cone-beam angle.
What does a pitch of 1 mean in CT?
Helical CT scanning is described by defining the pitch ratio, which is the ratio of the distance moved by the table (patient) in one rotation of the x-ray tube divided by the nominal x-ray beam width. A helical scan performed using a pitch ratio of 1 corresponds most closely to contiguous axial scanning.
What happens when pitch increases CT?
Changing the pitch on any type of CT scanner will not change the dose. If the pitch is increased, the AEC system on the scanner will simply increase the mA to keep the dose constant - as determined by the selection in the AEC system of Noise Index, Standard Deviation (SD), or reference effective mAs.
What is scanner pitch?
The “pitch” of a CT scan is commonly defined as the ratio of table feed per 360 degree gantry rotation and collimated beam width 7.
Does pitch affect CT number?
In the spiral CT technique, the term pitch is known, which is the distance (speed) of the table for one x-ray rotation in gantry (l) compared to the number and width of the detector (nT). Pitch changes will affect the spatial resolution of the patient's image and dose received.
What happens when you decrease the pitch in CT?
Pitch can be increased to extend the area of coverage and decrease scan time. A pitch of less than 1 means there is overlapping of slices, which results in higher patient dose.
How does pitch affect scan time?
By decreasing the pitch and the rotation times by equal amounts, both helical and patient motion artifacts can be reduced without affecting the exam time. The use of lower helical pitch also allows better scanning of larger patients by allowing a greater scan effective mAs, if the exam time can be extended.
When pitch is less than 1 The resulting bands of data are?
If the pitch is less than 1, the spiral is overlapping on itself. A pitch less than one means the table is moving a distance less than the width of the X-ray beam. This causes the scanned data to overlap on itself. This is often done intentionally to create high-resolution scans with extra detail.
What is a beam pitch?
Beam pitch is defined as table distance traveled in one 360° gantry rotation divided by the total thickness of all simultaneously acquired slices 3.
What is pixel in CT scan?
Pixel: Two dimensional picture element that makes up the matrix. Each pixel represents a CT number and is the building block of the matrix and image. Pixel Size = DFOV/matrix. Prospective data: An image automatically reconstructed from the scan data.
What is slice thickness in CT?
Slice thickness in CT scans normally ranges from sub-millimeter to 5 mm or above depending on the anatomy being imaged. FOV varies depending on the overall width of the specimen being scanned.
What is CT rotation time?
The average rotation time obtained with CTDP and Xi operated under the dedicated software was found to be 400.6 and 400.5 ms, respectively. The detector for this measurement need not be specifically designed for CT dosimetry.
How do you calculate CT pitch?
Thus, the pitch is calculated as follows: Pitch = table travel per gantry rotation (mm) / total nominal beam width, or Pitch = table travel per gantry rotation (mm) / (slice width × number of slices).
When pitch is less than 1 The resulting bands of data are?
If the pitch is less than 1, the spiral is overlapping on itself. A pitch less than one means the table is moving a distance less than the width of the X-ray beam. This causes the scanned data to overlap on itself. This is often done intentionally to create high-resolution scans with extra detail.
What is the ideal pitch in spiral helical CT?
The ideal pitch in spiral/helical computed tomography is 2:1 .
How does pitch affect scan time?
By decreasing the pitch and the rotation times by equal amounts, both helical and patient motion artifacts can be reduced without affecting the exam time. The use of lower helical pitch also allows better scanning of larger patients by allowing a greater scan effective mAs, if the exam time can be extended.
Dose and Pitch Relationship for a Particular Multislice CT Scanner ...
Over the past 25 years, CT has become an invaluable diagnostic imaging tool for a wide variety of clinical applications. Helical CT technology [1, 2] and, more recently, multislice helical CT [3, 4] have produced dramatic improvements in scanner capability, in image quality, and in patient throughput.However, a growing concern about the radiation dose delivered to the patient during helical CT ...
Helical CT image acquisition | Radiology Reference Article ...
Helical (a.k.a. spiral) CT image acquisition was a major advance on the earlier stepwise ("stop and shoot") method.. With helical CT, the patient is moved through a rotating x-ray beam and detector set. From the perspective of the patient, the x-ray beam from the CT traces a helical path.
The effect of pitch in multislice spiral/helical CT - PubMed
The purpose of this study is to understand the effect of pitch on raw data interpolation in multislice spiral/helical computed tomography (CT) and provide guidelines for scanner design and protocol optimization. Multislice spiral CT is mainly characterized by the three parameters: the number of dete …
Basic CT Parameters
W126 AJR:203, August 2014 Basic CT Parameters G. Donald Frey1 Frey, DG 1Department of Radiology, Medical University of South Carolina, 161 Ashley Ave, Charleston, SC 29425. Address correspondence to G. D. Frey ([email protected]).
What is pitch in CT?
Pitch (P) is a term used in helical CT. It has two terminologies depending on whether single slice or multislice CT scanners are used 1-3.
What is beam pitch?
Beam pitch is defined as table distance travelled in one 360° gantry rotation divided by the total thickness of all simultaneously acquired slices 3.
What is pitch in CT?
Pitch (P) is a term used in helical CT. It has two terminologies depending on whether single slice or multislice CT scanners are used 1-3.
What is detector pitch?
The term detector pitch is used and is defined as table distance traveled in one 360° gantry rotation divided by beam collimation 2.
What is beam pitch?
Beam pitch is defined as table distance traveled in one 360° gantry rotation divided by the total thickness of all simultaneously acquired slices 3.
