Latest / Cat Scan Guru Podcast / EP. 79 Pitch and Rotation Time 2-Part Series: Part 1: Pitch in CT

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EP. 79 Pitch and Rotation Time 2-Part Series: Part 1: Pitch in CT · Cat Scan Guru Podcast

• 0:00
  Hello. Welcome back, everybody.
• 0:01
  Welcome back to the podcast. Happy Thanksgiving, everybody.
• 0:06
  I can't believe Thanksgiving is here.
• 0:07
  And yeah, we are set up for snow here in the Midwest towards the
• 0:11
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• 0:15
  And I do not do cold considering I grew up in the desert and I'm
• 0:19
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• 0:22
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• 0:25
  So hope you guys are having an amazing week and enjoying the
• 0:29
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• 0:32
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  It really means a lot. And I put a lot of effort in my
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• 2:20
  training or you know, can use some guidance.
• 2:23
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• 2:25
  OK, so let's get into today's episode.
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  So I decided to make a two-part series.
• 2:30
  OK, so it's a two-part episode on pitch and rotation time.
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  Now, if you check out my TikTok channel, make sure you guys
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  check that out because I do have a video explaining pitch.
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  But I'm going to go into more depth as far as this podcast
• 2:46
  episode, so it makes sense for you.
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  OK, so in today's episode, this is Part 1, we're going to be
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  talking about pitch when it comes to CT.
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  Now, what is pitch in CT? So pitch is the ratio of the
• 3:02
  table movement to beam with. So your X-ray beam with during a
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  single 360° gantry rotation. So when the X-ray tube spins.
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  So what that does is it determines the amount of overlap
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  or gap in a helical scan path. And typically we use a pitch of
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  1. So when we use a pitch of one,
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  the table moves the same distance as your X-ray beam
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  with. Now you can use a greater pitch,
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  so a pitch greater than one and a pitch less than one.
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  So one of the key concepts that I want you to remember is how we
• 3:38
  calculate pitch because that is 1 important thing that you need
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  to know on the registry. So pitch is equal to the
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  distance that the table travels divided by the width of your
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  X-ray beam. So that is how we calculate
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  pitch when it comes to CT. Now pitch does have an impact
• 3:57
  when it comes to your image quality and your radiation dose.
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  And I'm going to explain as far as high pitch and low pitch
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  pitch, OK? Now when you have a pitch of 1,
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  you have the table that is moving exactly, you know, and
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  it's matching the beam width. So it provides continuous
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  coverage without any overlaps or any gaps.
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  So when we use a pitch of one, OK, now rotation time is a
• 4:21
  little bit different, but we're going to talk about that in the
• 4:23
  next episode. So when we have higher pitches,
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  so when I'm talking about high pitch, so this is pitch greater
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  than one. OK, so a high pitch.
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  So that means your table is moving further than the X-ray
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  beam. OK, so when you have a high
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  pitch, this allows for faster scanning, but it does create
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  artifacts. It does reduce your image
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  quality, however it does lower the radiation dose to your
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  patient. So think of high pitch like this
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  when you're scanning your abdomen and pelvises, when
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  you're scanning your PE studies, you have to get through that
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  anatomy fast because contrast timing is very crucial,
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  especially on a PE study right now when we're talking about low
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  pitch. OK, so lower pitches, this is
• 5:09
  when the table moves less than the X-ray beam, OK?
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  So the table's moving a lot slower.
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  So this is going to create overlap.
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  So what this does is it provides more data.
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  However, it does increase the dose to your patient.
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  It does increase your resolution and image quality, OK, because
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  of that overlap and your scan does take a little bit longer,
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  OK, But radiation dose is high when it comes to having a lower
• 5:39
  pitch. So think of lower pitch like
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  this. So when we're scanning a head
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  CT, we're using a lower pitch because we need that fine detail
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  of the brain and the different parts of the head IA C's same
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  thing. We need that fine bone detail in
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  the inner auditory canal temporal bones.
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  You know, you want to look at the fine detail of the temporal
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  bones, especially if like let's say for example the patient
• 6:02
  can't get a pituitary MRI. So typically we would do like
• 6:07
  either a dedicated pituitary CT if your site you know does have
• 6:12
  that protocol or we do temporal bones which we do cover that
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  area and you need that slower pitch to get that nice fine
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  detail. OK.
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  So lower pitches also we do use in cardiac scanning when we do
• 6:26
  ECD gated prospective gating. So when we do cardiac scanning
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  where we're doing prospective gating, we do use a slower pitch
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  because we need that nice detail and those nice vessels.
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  However, also keep in mind we have a faster rotation time of
• 6:42
  that X-ray tube when it comes to cardiac scanning, OK?
• 6:45
  So those two things are a little bit opposite when it comes to
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  that, OK? It's the same with other types
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  of exams where you have a slower pitch, but the X-ray tube is
• 6:55
  rotating a little bit quicker. Now it does impact your image
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  quality. So you know, when you have lower
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  pitches, you get less artifacts. Where when you have a high pitch
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  where you're, you know, the table is moving very, very fast,
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  It does increase that artifact. But to minimize those artifacts
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  when you have higher pitches, that's why we have
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  reconstructive algorithms or kernels depending on what system
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  you use. So those reconstruction, you
• 7:23
  know, algorithms do clean up that image quality so that when
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  it pops up on your screen, you have nice detail on your images,
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  OK, So and then radiation dose is always very, very important,
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  you know, because it depends on how fast or slow your table is
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  moving. So you have to take those
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  considerations in mind, OK. But with cardiac scanning,
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  especially when we have dual energy now we do have high pitch
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  scanning where we scan the entire heart in just one
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  heartbeat. So more dual energy scanners are
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  coming out with that as far as that.
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  OK. So that is how we determine
• 8:02
  pitch when it comes to that. So what I always like to do is I
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  always encourage everybody to just look at your protocols and
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  see, you know what different kinds of pitches on your
• 8:14
  protocols for different types of exams that you use, right.
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  So knowing that we customarily use a pitch of one because you
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  have no gaps, no overlap and you have you know your X-ray beam in
• 8:27
  your table that's moving simultaneously.
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  OK, so that that is what I have as far as pitch when it comes to
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  CT. Now make sure you check out my
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  TikTok channel because I kind of go into a little bit more as far
• 8:41
  as pitch and rotation time because those are a two-part
• 8:44
  series that I started on my TikTok page.
• 8:46
  OK. So hopefully this was very
• 8:49
  helpful and make sure you stay tuned to next week's episode
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  where I'm going to go ahead and talk about rotation time.
• 8:57
  So thank you so much for joining me on this podcast episode and I
• 9:01
  will chat with you guys next week.