Pitch (CT)
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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 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.
Choice of pitch affects both image quality and patient dose 2:
- P = 1.0: x-ray beams are contiguous for adjacent rotations
- P >1.0: x-ray beams are not contiguous for adjacent rotations, i.e. there are gaps in between the x-ray beams and tissue is not irradiated
- 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 (through fewer projections obtained, resulting in lower SNR). A pitch of <1.0 results in better image quality, but a higher patient dose.
Multislice CT (MSCT)
Beam pitch is defined as table distance traveled in one 360° gantry rotation divided by rotation divided by total thickness of all simultaneously acquired slices 3.
-<p><strong>Pitch (P)</strong> is a term used in <a title="Helical CT scanning" href="/articles/helical-ct-image-acquisition-1">helical CT</a>. It has two terminologies depending on whether single slice or multislice CT scanners are used <sup>1-3</sup>.</p><h5>Single slice CT (SSCT)</h5><p>The term <strong>detector pitch</strong> is used and is defined as table distance traveled in one 360° gantry rotation divided by beam collimation <sup>2</sup>.</p><p>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. </p><p>Choice of pitch affects both image quality and patient dose <sup>2</sup>:</p><ul>- +<p><strong>Pitch (P)</strong> is a term used in <a href="/articles/helical-ct-image-acquisition-1">helical CT</a>. It has two terminologies depending on whether single slice or multislice CT scanners are used <sup>1-3</sup>.</p><h5>Single slice CT (SSCT)</h5><p>The term <strong>detector pitch</strong> is used and is defined as table distance traveled in one 360° gantry rotation divided by beam collimation <sup>2</sup>.</p><p>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. </p><p>Choice of pitch affects both image quality and patient dose <sup>2</sup>:</p><ul>
-</ul><p>Thus a pitch >1.0 results in decreased patient dose but also decreased image quality (through fewer projections obtained, resulting in lower SNR). A pitch of <1.0 results in better image quality, but a higher patient dose. </p><h5>Multislice CT (MSCT) </h5><p><strong>Beam pitch</strong> is defined as table distance traveled in one 360° gantry rotation divided by total thickness of all simultaneously acquired slices <sup>3</sup>.</p>- +</ul><p>Thus a pitch >1.0 results in decreased patient dose but also decreased image quality (through fewer projections obtained, resulting in lower SNR). A pitch of <1.0 results in better image quality, but a higher patient dose. </p><h5>Multislice CT (MSCT) </h5><p><strong>Beam pitch</strong> is defined as table distance traveled in one 360° gantry rotation divided by total thickness of all simultaneously acquired slices <sup>3</sup>.</p>
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