What is the pitch in helical CT?

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 is the pitch of a CT scan?

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. For example, if the table traveled 5 mm in one rotation and the beam collimation was 5 mm then pitch equals 5 mm / 5 mm = 1.0.

Does pitch affect CT number?

Abstract. In spiral computed tomography (CT), dose is always inversely proportional to pitch.

What is beam pitch in CT?

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 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.

How does pitch affect CTDI?

A pitch less than one simply delivers more dose to the CT detectors. Reducing the pitch by a factor of 2 will deliver twice the dose to the patient, averaged over tissues, and will therefore have the same net effect on patient dose and image quality as doubling the mA.

What is beam width in CT?

Although the radiation beam width is typically within 1 millimeter of the nominal scan width for single-detector CT scanners, the width of the radiation beam typically exceeds the total scan width in MSCT scanners. The amount of beam width overage that occurs is dependent upon the detector configuration used.

What is collimator pitch in CT?

Single slice CT (SSCT) The term detector pitch is used and is defined as table distance travelled in one 360° gantry rotation divided by beam collimation 2. For example, if the table travelled 5 mm in one rotation and the beam collimation was 5 mm then pitch equals 5 mm / 5 mm = 1.0.

How does pitch affect CNR?

A pitch of 1 had the highest CNR values while a pitch of 3 had the lowest CNR values. For similar table speeds selection of a lower pitch will improve CNR. The effect of object-slice alignment on CNR indicates no significant difference at a pitch of 3, but it had the lowest CNR values.

How does pitch affect noise?

The sensation of a frequency is commonly referred to as the pitch of a sound. A high pitch sound corresponds to a high frequency sound wave and a low pitch sound corresponds to a low frequency sound wave.

What is slice width CT?

Slice thickness and slice increment are central concepts that surround CT/MRI imaging. Slice thickness refers to the (often axial) resolution of the scan (2 mm in the illustration). Slice Increment refers to the movement of the table/scanner for scanning the next slice (varying from 1 mm to 4 mm in the illustration).

How is slice thickness calculated in CT?

With single-slice CT, the slice thickness is determined by the detector width – with mild slice broadening just based on the pitch of the helical scan. With MDCT, slices can be composed of a single detector thickness or multiple adjacent detectors.