CT Essentials Webinar Series 2 - Scanning and Reconstruction Parameters

Good afternoon everybody on behalf of the Siemens Healthineers education team, I would like to welcome you to the next session of our CT Essentials Webinar series this week, covering setae, scanning and reconstruction parameters, part one if you have any questions throughout the webinar, please type these on the right hand side of the screen and we will answer as many as possible at the end certificates will be available through PP Connect within the next week and you will also receive an email linked. The recording by tomorrow afternoon I will now hand over to Andrew Pam, one of our CT application specialists to begin this session. Thanks Mel. Hello everyone, thank you for joining me today. So as Mel mentioned where covering session two and the topic that will be describing is CT scanning and reconstruction parameters. Now because of how? Involved these topics, we decided to break them up into two sessions. Last week we went over UI navigation of the Somerset and Scanners and now I think we're ready to go for more heavier topics. So without further ado, so some of the topics that we will be describing under CD parameters are what we consider to be fundamental towards practicing CT. So some of the parameters that will be discussing our two voltage to current rotation time, collimation, slice width, feed per scan, feed per rotation, pitch increment and field of view. So with these parameters, what we're aiming to do is just to go through what? Sakli what they are and what are the consequences to us adjusting these parameters as we build our protocols. But before we do that, I just want to go through the basic idea and principles of see T just to add to add to the background of it all. But essentially as hopefully you can see my diagram there, but essentially what it is is that we're trying to measure the 2D function of what we're scanning, and so if we know all the X Ray projections that are passing through, we should be able to get the attenuation function and then begin to build on that to the object. But building on that. This diagram should show. Hopefully you can see this should show you exactly what we're trying to achieve, so as you can see, that's just the traditional X Ray tube detector channel system there, and as we can see. As the incident beam enters into the anatomy and then exits into the detector channel, we measure this intensity profile over here and I'm going to break this down a little bit and it's also using this equation as well to graph to plot this graph. But as we can see, as the beam hasn't passed through the anatomy yet, the exit beam is equivalent to the entry beam, but as the beam passes through the anatomy we can begin to see that the intensity begins to drop. And then we're getting fluctuations in intensity as the beam passes through the anatomy and through the various structures. And then as we move laterally through the anatomy, we're going to go back to the intensity equals to the intensity beam again. OK, as you can see, this attenuation is also plotted down here on this attention attenuation profile graph here and it's also using this equation here. Now what's important about this graph is that it allows us to calculate the attenuation coefficient of the structures in that in the scanned object and what's really meaningful about the attenuation coefficient is that it helps us to calculate the grayscale or what we call CC value. And once we normalize that value to the attenuation of water. We get traditionally we call Hounsfield unit, so that's just a bit of background about CT there. OK, but moving on to tube voltage I know we have a few student radiography students in the audience today, so this this concept should be familiar to you. But just as a bit of a background, especially to voltage when we play around with true voltage by sensually creating the voltage potential between the cathode and anode and gives us the quality characteristics of our X Ray beam. But two voltage essentially has a greater influence on patient radiation dose and MAS and it increased increasing cavey. Obviously increases the patient dose now. What does that mean for image quality while a higher cavey generally results in reduced overall image noise, which is great. However, again, it does increase the radiation dose and also one image quality tradeoff is that it does decrease the image contrast OK, and the reason why is that if you increase the energy of the X Ray beam, essentially less and less structures within the anatomy will attenuate that beam, and so the structures will look more homogeneous than and we won't be able to differentiate. As well, OK? Moving onto tube card Ms Ascentia Lee, what it means is that it affects the number of photons in our X Ray beam and MAS is a product of both the X Ray tube current which is milliamps, MA and the exposure time and how we control exposure times are scan time. Now, depending on our scanning mode, Ms is actually described differently. So in sequential scanning, if you have a single slice CT scanner for example, or you performing a single slide scan, ascential EMS is described as sequence Ms. And it indicates the applied dose to that individual slice. Now, if we're doing a helical scan, we describe it as spiral Emmaus, and it's influenced by the pitch factor. Sorry, it's not described as MAS, but in the spiral mode. But in that mode it amazes described as effective MSN. It takes into account the pitch factor. And and its influences on image quality and doors an actually. This is how our Shoreview proprietary technology takes into account as well. So with me S and image quality is really important when we're adjusting our protocols to understand what will happen if we decrease or increase the MA S essentially at a higher MA is required to reduce the image noise and improve the low contrast resolution, whereas lower MA sitting are sufficient with imaging anatomy that is inherently height issue. High contrast. So for example, if we imaging a Bony anatomy or along examination because. They are inherently high contrast. We don't need the extra MAS to image them if effectively. OK, but moving on to a little bit of dose modulation which I would say is majority of most scans are. Perform when we engage with kiddos 4D, which is our automated dose modulation. The quality reference Ms is used to standardize the image quality preferred by the user. Quality reference image determines the overall dose and image quality criteria for a reference patient. So I want to unpack that a little bit more. It's a bit of a mouthful, but essentially at Siemens we. Have characterized the image quality for varying levels of MAS. For a reference patient, which is essentially a 75K patient. Now really what's powerful about that is that. Knowing the image quality changes with a reference patient allows us to make a quality image quality argument when we adjusting RMS value. So when we adjusting our quality reference parameter, we're saying, hey, I want you, I want to achieve the same image quality. That you achieved on your 75K patient when you used XMS, OK, and so with the dose modulation. It will take that image quality argument and apply the effect. The necessary MA is to achieve the same image quality so hopefully that that unpacks that a little bit for you. OK, so moving onto rotation time, rotation time is seconds required for one complete 360 degree rotation on the tube detector system. It determines the speed and the temporal resolution of the system and for the University students out there I will try to unpack temporal resolution a little bit more because I know that it was something that confused me when I was at school. Years ago, but yeah, essentially rotation time should be adapted to the clinical demands of the see T examination. Shorter rotation times are required for routine, chest, vascular and pediatric studies to reduce the scan duration in motion artifacts, so you can just imagine clinically how those patients would present when you're trying to edit your short, shorter rotation times, whether it's breathing is Asser, Bashan, or whether or not it's just non compliance. Plenty of reasons why you want a shorter rotation time to effectively reduce your scan time for vascular and cardiac. Siti studies a shorter rotation times are required for optimal contrast enhancement and to freeze the motion of the heart, so that's kind of where I want to just pause and just unpack that one a little bit. So for those who are new to see, TI just want to describe it this way. Imagine if you had a Polaroid camera and you were stationary in a fixed position and you're trying to take a picture of someone. Moving fast on the bike, chances are that image is going to be quite blurry and you're not going to capture it in any real high quality Fidelity. But if you were on a bike as well, and you were traveling at the same speed as the bike that you're trying to image, you're going to really freeze his motion, so to speak, relatively speaking, and you're going to really have a steel image of that subject, so that's just an analogy that I hope will help you. Kind of understand it conceptually. But moving on longer rotation times are used in routine brain and lumbar spine examinations where patient movement motion is negligible or when increased dose and projection samplings are needed to improve image detail. So you have to imagine that with the next road trip there is a maximum tude loading that you can really push it through and so reducing the rotation time allows you to reduce the loading by giving it enough time to really just apply that dose and sample the anatomy correctly. OK, now moving on to collimation. Now this is a bit of a hairy one because in multislice CT there is 2 combinations to collimation and detector channel collimation and multislice CT they kind of work incongruency, so with collimation, total collimation determines a slice in section thickness that will be utilized for particular setae. Scanning procedure really powerful when we're talking about diagnostic versus interventional, where we can change the scanning mode as well as the collimation. But when selecting the collimation, the technologist at determines the tube collimation by narrowing or widening the X Ray beam. This is not to be confused with this license, xclamation, which perfects the quality of acquisition data. It determines the minimum slice width that can be used for image reconstruction. So that's actually the important part. So if you increase it to, say, 10 millimeter slice thickness to be quiet at, then that's the Max. That's the minimum you can reconstruct that. OK, so just be mindful about how that can affect. Your post processing. But narrow reconstructed slice, which results in an improved axial resolution. But it does also increase noise, so be mindful as to what anatomy is scanning in and whether or not you can introduce more noise. OK, but moving on an just adding to that. We're going to discuss a little bit about detector configurations and the collimation. So here if we're going to use a 30. Two row by zero point 6 millimeter detector channel as an example. So if I'm not sure if anyone is really quick at math, mental math here. But as we can see the collimation with the coverage being coverage is exact same when we multiply these figures. But what we can see is that the narrow slice collimation is actually. Using the shop sampling, yes, we're actually going to do 64 slices, but really what it's referring to once a narrow slice? Collimation is the 0.6 millimeters there. So that means that we can reconstruct a thinner at 0.6 millimeters for example, whereas if we had color made the slice thickness to 1.2, that is the minimum slice thickness that we can reconstruct that. OK, so, and how it does that third example is that it will fuse the detector channel. Imports and then breaking and essentially marry them together so that it's 1.2 millimeters. So just be mindful as. How that's going to affect image quality and how you're going to proceed further. OK, so moving slice width now. This is a reconstruction parameter. I'm just throwing this in the middle because I think it kind of marysin nicely with what we've been talking about. Slice width is the thickness of the reconstructed image. Shouldn't be confused with the collimation. These terms are regarded as synonyms for single slice city imaging, because in this case only images with width equal to the size can be reconstructed. So with single slice, traditionally the X Ray beam with was the scan, collimation, so they kind of were. Really the same thing, but not so much in Multislice ET. OK, but hopefully you can read that, but if not, I'm just going to breakdown the differences in slice width and how they affect image quality, but ultimately with thinner slices you're going to get a much better spatial resolution, but at the cost of increased noise. So when we scanning something like the Patriots temporal bones, we often going to scan data thinner, slice, or we're going to produce the math in a slice, and we can afford a little bit more noise because that anatomy is. Inherently high contrast, OK within the slices as well. On the admin side. Just be mindful that they are of course larger files and they're going to eat up much of your storage, so be sure to see to make note as to whether or not your protocols need thin slices at all. So just something to consider. And then Lastly, you do want thin slices if you want to create further postprocessing like 3D or any kind of curve, NPR for example, you know want thinner slices. Whereas with thicker slices it is good for high, low contrast resolution. It's better for tissue differentiation, so that's why when you scan and abdomen scan, when you reconstruct it, its chances are it will be on five on five's or something close to that. Has come with lower noise levels. The Advent Admin advantages is that it does eat up less storage, but it's not really recommended for intense post processing. OK, so that's kind of where you might want to consider producing some things if that's how your practice likes to perform examinations. OK, but this is a bit of a visual example of the consequences of slice width, so you can see two images reconstructed at one within and one with a bit of a thicker slice there. Now on the left it's a zero point 775 millimeter. Slice with and hopefully you can appreciate this, but that image has quite a bit of noise in it. Certainly for an abdomen scan there is quite a bit of noise, but some of the advantages that you might see is the increase in detail there. Hopefully you can appreciate that that lesion in I think it's either segment two or three, but that lesion there is certainly pops out a lot clearer than the lesion over here. But that being said, with the 5 millimeter sliced. Image is a lot smoother, it it has great tissue contrast. But again when we're making a comparison between 2 images, I personally can see that lesion a lot better than I can see that lesion. OK, so that's just the consideration here. OK, this is another example of the Patriots temple, Barnes, Oregon here. As we can see. 0.6 millimeter slice will get in great detail. We get. We can see all the little structures in the master DSL's there and we can see that you can at all. Sorry that slices really showed that well, but yeah, it has way more detailed than the one on the right which is reconstructed at three millimeters and you can see also it's suffering from your partial volume artifact in there as well, which we can go in more detail later on. OK, so back into scanning parameters, we're going to discuss feed per scan. Now this is a lot more relevant to single sequential scanning or single slice scanning CT scanner. Sorry, but effectively it's the distance of the table travels during sequential scanning. It determines the increment between the axial slices. For single slice CT scanners and also influences the coverage of multislice CT sequential scanning, so again it's. It's still within the sequential scanning room. Typically the feed equals the slice. Collimation of single slice CT, or the total collimation of MSCT. But in this case what we're saying is that. If sorry if this is the case, then it would likely mean that your volume data set is contiguous, but if the feed exceeds the slice collimation there are gaps in your acquisition results and that those those type of data sets wouldn't be good for post processing. But if the feed is less than this last confirmation or total collimation, overlapping raw data results are quiet, so those ones raw overlapping raw data is certainly going to help you with more heavy post processing and will have more detail and image as well. But moving on to feed parrot protection. Feet per rotation is now moving into the multislice CT area. It's the distance between. Sorry the distance the table travels during one gantry rotation during a spiral scan. It is usually used to describe the speed of the spiral acquisition and the influence in the scan direction, and whilst it's not a parameter that we adjust. On the platform we do adjust the feed per attention by indirectly adjusting the pitch value OK, and just to be sure this is the pitch. The equation for pitch there OK and that shows the relationship between the Z coverage and the feet per rotation. But just ultimately though, if you increase the pitch, you're increasing the feed per rotation. OK, so moving on, it's a good time for us to discuss pitch factor now. The pitch factor determines the patient table speed and speed of acquisition. The higher the pitch value, the faster the table travels in, the shorter the scan duration and generally the values ranges between 0.35 to 1.5 and you select the billing increments of 0.05. Of course, that doesn't apply to duel source scanners, for example. The force that can scan at a higher pitch. But again that we mentioned last week that depending on your scanner configuration there will be differences in the examination parameters there so. Just be mindful of that as well. That's just a reemphasis on the pitch equation there. OK, but you know what? How does pitch affect our examination? So despite it moving faster, if we have a pitch of 1, so besides this speed of the acquisition, if we have pitch of one, it means that there is no overlap. But if we have a picture of 0.5, it means that the table travels half the coverage per rotation, but. More broadly, essentially, if the table travels at distance shorter than the coverage, the pitch is less than one, so that's where you get overlapping your your raw data there. But we single source city not to be confused with single Slice City single seat is limited to dial acquisitions with a Max pitch of 1.5. Faster table speeds on these type of scanners would result in deteriorating image quality. Back that is due to the gaps in data sampling, so being mindful that whilst you don't have to scan with overlap scanning above one will result in gaps in your data which requires more interpolation to stitch together, and that's where those artifacts can really come through. OK, and just more on the language side of pitch. It's normally expressed in ratio, so a picture of 0.5. Can be described as Zero point 5 by 1. Yeah, and that's also just discussing that pitch of 0.5 respectful refers to an overlap and higher patient dose as well. So yeah, that's right with picture and you do have to take into consideration patient dose as well as image quality. And yeah, if you have a faster pitch, you can degrade the image quality, but you could also reduce the patient verse as well, so it's a bit of a balancing act. Cool moving into increments there. Sorry this is moving back into the reconstruction parameter increments or position increments is the distance between reconstructed images in the Z direction. You can be freely adapted from Zero point 1 millimeters upwards from Spyro or two D sequential scanning, but if the increments is smaller than the slice width, images are created with overlap, which provides better detail of the anatomy. And also gives you the ability to do further postprocessing because there is that overlap. But moving on to reconstruction increases. This is where I want to talk a little bit more about partial voluming. I'm sorry a little bit background about partial voluming. Essentially what it is is that it's if we're looking at one pixel voxel partial voluming is the averaging of neighboring pixel voxels into the one that we want to image, and so if we have a large request, if we have a. Large slice thickness without any overlap. We can really miss small lesions and I'll give you a bit of a visual representation that in second. But in this case, the best case would be that the object is that is covered with in one slice and can be pictured properly without blurring. So partial volume effect does present in that blurring and the worst case would be the object falls in between reconstructions. Slices will sorry, the object that falls in between reconstructed slices will be inadequately presented in both images or maybe overlooked so sometime. So I'll show you an image here. So these images are essentially two contiguous 5 millimeters slice reconstructed images without overlap, and as you can see, because of that thick slice of width. Ascension without any overlap we're getting the partial volume of that lesion of lung nodule there, and it's not really a good characterization of really what that module is. So if we provided a 50% overlap, we're going to get a better representation of that module there. And as we can see depicted in the center slice. So that's another way. That's another consideration when you're thinking about increments there OK? Who, now with field of view, now this one is, I'm sure a lot of people are familiar with, but essentially with the filler view, it determines the area of anatomy displayed with within the see T image as well as the spatial resolution. So you can see with this image here to 400 millimeter. Filter grew out to 1:20 and these images are both reconstructed as well, not rather not magnified, and go into that a little bit later, but. The spatial resolution is generally improved by using a smaller field of view because it's reducing the pixel size and how it's being represented, and on a side note, when it comes to field of view for those radiographers who are working in an RT site or work closely with NRT site, it is important to include the skin edge because it does help the. It does help for the planning of that type of therapy. OK, so just be mindful of that. But some of the so going around multiple size. I've seen some radiographers do this when we've they've scanned in abdomen and they've seen a. They've seen some pathology in the spine, or the vertebrae, and they just grab the original set, another visual there, grab a reconstructed image of the abdomen, and they just zoom the image into the spine and then they just create a whole bunch of series from that. Now I would really, really discourage you from doing that, because it's not really the same as reconstructing it at a smaller field of view where you're preserving the spatial resolution. What you're really doing when you're magnifying it and creating a series that way is that you're. Blowing up the existing pixels and how it was interpolated for a larger field of view. And yeah, you really just want to. If you really want to do any kind of diagnostic analysis on a particular need, it's the best way to go is to reconstruct it with that smaller field of view. Just be mindful though, to be able to do that. You still need to have your raw data available because it is a reconstruction thing. But that's about it for me, and scanning and reconstruction.

Tube Voltage (kV) CT Parameters — detector configuration and Feed per Rotation (MSCT) Reconstruction increment and partial volume effect Increment and partial volume effect Feed per Scan (feed) Feed per Rotation (fee/rot) Field of View Image magnification — what if we just zoom up the Slice Width Slice Width and Image Noise Scanning Principle Tube Current mAs Tube Current (mAs) Collimation collimation Rotation Time Pitch Feed per Scan Basic Idea CT Parameters Increment SIEMENS .. SIEMENS SIEMENS SIEMENS .. Healthineers Healthineers • Healthineers • Healthineers collimation image? Collimation The Field of View (FOV) determines the area of Tube Current mAs Tube Current (mAs) mAs and Image Quality Tube Voltage (kV) Rotation Time is the time (second) required for one complete 360 degree rotation of the Collimation (total collimation) determines the slice or section thickness that will Feed per sotati(on feed) is the distance the table travels during one uential Feed per sctan (or feed) is the distance the table travels during snequential Feed per scan (or feed) is the distance the table travels during sequential Increment or position increment is the distance (in mm) between the Pitch or Pitch factor, is a spiral scanning parameter determining the patient table Feed per sotation (feed/rot) is the distance the table travels during one uentia If thick slices without overlap are used, small lesions (depending on their size and Image Magnification gives worse results because zooming and image only blows Feed Per Rotation (feed/rot) is the distance the table travels during one gantry For example; if the table moves by a distance equal to the z-coverage per Pitch is expressed as a ratio, such as 0.5:1 and 1.5:1 Feed per sctan (or (feed/rot) is the distance the table travels during snequential three consecutive 5mm slices with 50% overlap: the nodule is clearly depicted in If we know all projections (line integrals) of 1. Physical Deter Configuration — 32 rows of (1) (2) (3) Think slices x-ray tube Tube voltage has a greater influence on the patient's dose anatomy displayed within the CT Image as well as (1) (2) (3) Higher spatial resolution greater detail Higher low contrast resolution — better tis- tube-detector system. It determines the speed and temporal resolution of the system a 2D function, the function itself can be scanning. It determines the Increment between the axial slices for single-slice CT be utilised for a particular CT scanning procedure. When selecting the Collimation, reconstructed images in the z-direction. It can be freely adapted from 0.1mm the centre slice between the contiguous slices rotation, the pitch is equal to 1. position relative to the reconstructed slices) may not be clearly registered due to rotation during spiral scanning. It is usually used to prescribe the speed of the up and interpolates the existing pixels. To preserve the resolution, a second 0.6mm Slice width is the thickness of the reconstructed image. Slice width should not Tube Current (mAs) Higher mAs is required to reduce the image noise and improve the low contrast sue differentiation CT Essentials Webinar Series," CT Essentials Webinar Series" CT Essentials Webinar Series? its spatial resolution than mAs. Increasing kV causes an increase of dose Increased noise noise level a Technologist determines the tube collimation by narrowing or widening the x-ray scanners and influences the coverage for MSCT sequential scanning table travels and the shorter the scan duration. Generally the value ranges from reconstruction should be performed with a smaller FOV using the raw data partial volume effect resolution. Lower mAs settings are sufficient when imaging anatomy with inherent mAs is defined as the product of the x-ray tube current (mA) and the exposure With a pitch of 0.5, the table travels half the z-coverage per rotation Rotation Time Fewer images. easier storage and archiving More images. larger storage requirement A pitch of 0.5:1 results in overlapping images and higher patient dose. A Pitch of 2 x 0.6 mm beam 0.35 to 1.5 and is selectable in increments of 0.05 Rotation time should be adapted to the clinical demands of the CT examination. Shorter Recommended for detailed anatomical struc- Recommended for regular soft tissue studies high tissue contrast . Such as routine bone or lung examination Session 2: time (s). mAs determines the number of photons in the x-ray beam 2. Narrow Slice Collimation : 32 x 0.6mm double tures and 3D presentations with 20 post-processing Collimation collimation A typical CT image is reconstructed with a square 2:1 results in extended imaging and reduced patient dose (1) (2) (3) kV and image quality rotation times are required for routine chest, vascular and paediatric studies to reduce the Typically, the Feed equals the slice collimation for single-slicea or the total These terms are regarded as synonyms for single-slice CT imaging because in Typically, the Feed equals the slice collimation for single-sliceaCT or the total Typically, the Feed equals the slice collimation for single-slice CT or the total sampling with z-sharp technology allows I. Reconstructed Smaller FOV Sequence mAs used to indicate applied dose format using a fixed matrix on 512 x 512 pixels The Feed per Rotation is usually set up indirectly via adjustment of the Pitch Best Case: the object covered within one slice can be pictured properly or Slice Width scan duration and motion artifacts. For vascular and cardiac CT studies, shorter rotation the line integral of a 2D attenuation Imaging at a higher kV (same mAs) generally results in Essentially if the table travels a distance shorter that the z-coverage, the pitch is • Measured intensit this case, only images with a width equal to the scan collimation can be collimation for MSCT. In this case, the acquired data represents a set of contiguous Slice Collimation affects the quality of the acquisition data. It determines the acquisition of 64 slices per rotation Quality Reference mAs (quality Ref mAs) Spiral mAs influenced by the pitch factor (effective mAs) value. Pitch is defined as : High resolution images, such as those in the inner ear structure or lung These images show the increment with a partial volume effect The Slice width influences the noise and the image definition as summarized in times are required for optimal contrast enhancement and to 'freeze' the motion of the function 2. Zoomed images Feed per Scan (feed) reduced overall image noise. However, tradeoffs are less than 1 reconstructed axial slices to slab-by-slab volume datasets. If the Feed exceeds the slice minimum slice width that can be used for image reconstruction. Narrower post processing Pitch is the relationship between the patient couch movement and x-ray beam parenchyma, should be reconstructed with thin slices and appropriate wide When CARE Dose 4D (automated dose modulation) is employed, the Quality Ref the table above Spatial resolution is generally improved by using heart. Pitch = Feed per rotation (mm)/ z-coverage (MM) 1. 0.75mm Slice width, more noise, but more detail in the image CT Scanning and Reconstructipn'.•. CT Scanning and Reconstructipn'.'. decreased image contrast and increased dose. Feed per Rotation (fee/rot) 1. 400m m collimation, there are gaps in the acquisition result. If the Feed is less than the slice reconstructed slice width results in improved axial resolution, but also increases • Total attenuation (line integral) collimation Collimation a small FOV because it reduces the pixel size window settings. The images above are an example 3. Wide Slice Collimation : 16 x 1.2mm; signals 2 x (32 x 0.6 mm) mAs is used to standardise the image quality preferred by the user. Quality 16 x 1.2 mm ctappssupport.au@siemens-healthineers.com Effective mAs 2 contiguous 5mm slices reconstructed without overlap, the small lung Feed per sotation feed) is the distance the table travels during one uentia Feed per rotation = the distance the patient table traves during one 360 Feed per sotati(on feed) is the distance the table travels during one uential Feed per sctan (or feed) is the distance the table travels during snequential FOV = 120mm Measuring all rays through a 2D object can collimation or total collimation, overlapping raw data results are acquired Pitch noise The relationship between these factors is defined by the formula Worst Case: the object that falls in between reconstructed slices will be Pitch = Feed per rotation/total collimation L = = —In— Reference mAs determines the overall dose and image quality criteria for a NOTE: Be aware of your Planning Software, as they might not recognise overlap in from the individual detector rows (0.6mm) are Single source CT is limited to data acquisition with a max pitch on 1.5. Faster Parameters Part 1 1. 0.6mm slice, excellent small detail Longer rotation times are used in routine brain or lumbar spine examinations where degree revolution of the tube yield the attenuation function of this object Takes into account the influence of PITCH on both the image quality and 2. 5mm slice, smooth image with excellent soft tissue contrast, but less small 2000 inadequately presented in both images (partial volume effect) or may be Increment the images reference patient. fused in pairs table speeds on these scanner would result in deteriorating image quality due to NOTE: for RT scanning please include the skin patient motion is negligible, or when an increased dose and projection samplings are without superposition 2. 3mm slice, poor image details Attenuation coefficient, CT value Z-coverage = the total collimation defined in the centre of rotation the dose (SureView Concept) lesion detail overlooked Field of View (FOV) edges gaps in the data samplings need to improve image details. 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