CT Image Quality - USA

Continue Continue CT Image Quality CT Image Quality Online Training This online training will introduce you to the complex subject of image quality in Computed Tomography, and will cover the following two learning objectives: Specify the Criteria Affecting Image Quality in CT 1 Define the Factors Influencing Image Quality in CT 2 Master Template HOOD05162003052540 | Effective Date: 26-Nov-2019 CT Image Quality Online Training [audf_001.mp3] Welcome to the CT Image Quality Online Training. This online training will introduce you to the complex subject of image quality in Computed Tomography, and will cover the following two learning objectives: … Specify the Criteria Affecting Image Quality in CT Criteria Affecting Image Quality CT Image Quality (IQ) Criteria Contrast Temporal Resolution Sharpness Noise Artifacts CT Image Quality (IQ) Criteria [audf_002.mp3] This picture gallery gives you a preview of the criteria affecting CT image quality that we will focus on in the first part of this training. Criteria for Image Quality | Contrast Good contrast in CT images depends on the clear differentiation of CT values (indicated in Hounsfield units = HU) in the scanned objects. Contrast > 100 HU = High Contrast Contrast < 10 HU = Low Contrast Contrast [audf_003.mp3] Contrast is one of the fundamental characteristics in any image. In CT imaging, contrast depends on the clear differentiation of CT values. The radiodensity of the scanned objects is quantitatively described in Hounsfield units. Criteria for Image Quality Contrast | High Contrast Resolution Ability to display high-contrast objects Influenced by the system geometry Determines the sharpness of the image Great differences in tissue density Required for good image quality in bone and lung structures High image noise → scanning at low dose is necessary Insufficient differentiation of small variations in tissue density High Contrast Resolution [audf_004.mp3] High contrast resolution is the ability to display high-contrast objects in the CT image. It is influenced by the system geometry and determines the sharpness of the image. High-contrast images offer great differences in tissue density and are required for good image quality in bone and lung structures. High-contrast images also suffer from high noise. Therefore, scanning at a low dose is required. On the downside, high-contrast images do not offer sufficient differentiation of small variations in tissue density. Criteria for Image Quality Contrast | Low Contrast Resolution Where slight differences in contrast are significant! Image quality is affected by sharpness and noise Required for good image quality in soft tissue Great differentiation in soft tissue organs such as liver and brain Low Contrast Resolution [audf_005.mp3] Low contrast resolution is where the slight differences in contrast are significant. It is required for good image quality in soft tissue where sharpness and noise are factors that should be considered. Low-contrast images offer great differentiation in soft tissue organs such as liver and brain. SOMATOM Force Criteria for Image Quality | Temporal Resolution (1/2) Temporal resolution (TR) is the time required by the CT scanner to generate the data for an image. It is determined by the rotation time (RT) of the gantry. The shorter the acquisition time, the lower the occurrence of motion artifacts (important, e. g., for heart scans). For cardiac examinations, a 180° rotation of the gantry is sufficient to produce an image. Single Source scanners TR = Fastest RT 2 Example SOMATOM Edge TR = 280 ms 2 = 140ms Dual Source scanners TR = Fastest RT 3,75 SOMATOM Drive TR = 280 ms 2 = 140ms due to the 95º angle of the X-ray tubes TR = 66 ms Examples Temporal Resolution (1/2) [audf_006.mp3] Temporal resolution is the time required by the CT scanner to generate the data for an image. It is determined by the rotation time of the gantry. The shorter the acquisition time, the lower the occurrence of motion artifacts. For cardiac examinations, a 180-degree rotation of the gantry is sufficient to produce an image. In order to calculate the temporal resolution of a Single Source CT scanner, we have to take the fastest rotation time and divide it by 2. For Dual Source scanners, the fastest rotation time must be divided by 3.75. Criteria for Image Quality | Temporal Resolution (2/2) High temporal resolution is required for clinically stable images. The faster the rotation time of the gantry, the higher the temporal resolution. Low Temporal Resolution High Temporal Resolution Temporal Resolution (2/2) [audf_007.mp3] High temporal resolution is required for clinically stable images. The faster the rotation time of the gantry, the higher the temporal resolution. Criteria for Image Quality | Sharpness Sharpness describes the sharpness of an object in relation to the surrounding tissue. It depends on: Rotation time (Convolution) Kernel Slice thickness Radiation dose Noise is superimposed on the image and leads to a snowy impression. High noise Low noise 60 mA 206 mA Sharpness [audf_008.mp3] Sharpness describes the sharpness of an object in relation to the surrounding tissue. It depends on rotation time, kernel, slice thickness, and radiation dose. Noise is superimposed on the image and leads to a snowy impression. Criteria for Image Quality | Noise The intensity of image noise is influenced by the number of X-ray quanta reaching the detector and thus contributing to image generation. This number is determined by: Tube current Tube voltage Slice thickness Collimation (Convolution) Kernel Object thickness High noise Low noise 206 mA 60 mA Noise [audf_009.mp3] The intensity of noise in the image is influenced by the number of X-ray quanta reaching the detector, thereby contributing to the generation of the CT image. The number of X-rays or quanta reaching the detector is determined by tube current and voltage, slice thickness, collimation, kernel, and the thickness of the object. Criteria for Image Quality | Artifacts Artifacts are various patterns and structures that appear in the CT image although they do not exist in the original object. This are the most common artifacts in CT imaging: Motion artifacts Partial volume artifacts Beam hardening artifacts Ring artifacts Metal artifacts Long scan time Wrong slice thickness Wrong scan protocol Defective detector elements Implants or metallic foreign objects Caused by: Artifacts [audf_010.mp3] Artifacts are various patterns and structures that appear in the CT image although they do not exist in the original object. Take a look at the list of the most common CT imaging artifacts we are going to discuss and their major causes. Criteria for Image Quality | Motion Artifacts Motion artifacts appear due to the movement of the patient during the data acquisition. The shorter the scan time, the less likely motion artifacts are. strong moderate short long Artifact Scan time (s) Motion Artifacts [audf_011.mp3] The first type of artifact presented here is the so-called motion artifact. As its name indicates, this artifact appears due to the movement of the patient during the data acquisition. Short scanning times help to avoid this artifact. Criteria for Image Quality | Partial Volume Artifact (1/3) If an object is not located in the center of the radiation (isocenter), it is not detected by the X-ray beams in every tube position. This causes a partial volume artifact. Partial volume artifacts are stripe-like artifacts. They often occur in the bony area at the base of the skull. Tube at 0° Different tissues sampled by opposing rays Detector Combined Detector Tube at 180° Z-axis Partial Volume Artifact (1/3) [audf_012.mp3] If an object is not located in the center of the radiation beams (the isocenter), it cannot be detected in the same spot by each emitted X-ray beam, thereby causing the partial volume artifact. This is especially a problem if very dense structures are only partially included in the slice. This artifact manifests itself in the CT image as stripes. It is very common when scanning heads, particularly in the area at the base of the skull. Criteria for Image Quality | Partial Volume Artifact (2/3) Partial volume artifacts can be reduced by using a smaller slice thickness. By selecting thinner slices, artifacts of this type are decreased since the probability of high-contrast structures only partially reaching into the slice is lowered. However, the selection of thinner slices will lead to higher noise and, consequently, to a decreased low contrast resolution. 2 mm 5 mm Partial Volume Artifact (2/3) [audf_013.mp3] Partial volume artifacts can be reduced by using a smaller slice thickness. By selecting thinner slices, artifacts of this type are decreased since the probability of high-contrast structures only partially reaching into the slice is lowered. However, the selection of thinner slices will also lead to higher noise in the image and, consequently, to a decrease in the low contrast resolution. Criteria for Image Quality Partial Volume Artifact | Wrong HU Values (3/3) Without overlap: CT value underrated Object overlooked Two adjacent 5 mm slices Three consecutive 5 mm slices with 50% overlap Use overlapping slices! With overlap: Small objects visible Wrong HU Values (3/3) [audf_014.mp3] This CT image of a small lung nodule makes a strong case for using overlapping slices to prevent the partial volume artifact. In the two adjacent slices without overlap, the CT value of the nodule is underrepresented and the object might be overlooked. In the three consecutive slices with 50% overlap, the nodule is clearly visible in the center slice. Criteria for Image Quality | Beam Hardening Artifact Beam hardening artifact is corrected automatically Selection between bone or iodine beam hardening is possible With correction Without correction Outgoing X-ray beam from the patient Incoming X-ray beam from the tube Object Beam Hardening Artifact [audf_015.mp3] The beam hardening effect is illustrated in the drawing. The length of the arrows represents the variable energy of the X-ray quanta in the emitted radiation beam. Low-energy quanta are selectively attenuated in the object and the resulting X-ray spectrum shifts to higher energies. This effect is called “beam hardening”. The beam hardening artifact is corrected automatically by the system. A selection between bone or iodine beam hardening is possible. Criteria for Image Quality | Ring Artifacts If too many detector elements are defective, this can no longer be compensated for. This results in so-called ring artifacts. One or several calibrations can be done in order to try to eliminate this artifact. If the problem persists, calling the SIEMENS Healthineers Service hotline is the only option. Ring Artifacts [audf_016.mp3] If too many detector elements are defective, a ring artifact of the type seen in the images will appear. One or several calibrations can be done in order to try to eliminate this artifact. If the problem persists, calling the SIEMENS Healthineers Service hotline is the only option. Criteria for Image Quality | Stripe Artifacts The user cannot do anything to solve this problem. A Service call is the only option. Stripe Artifacts [1.18 Stripe Artifacts_v2.mp3] Stripe artifacts appear in the image as a result of a problem of system components, e.g. IRS or broken filter. There is nothing the user can do to solve this and a Service call is the only option to get the problem fixed. Criteria for Image Quality | Metal Artifacts Metals such as gold almost completely absorb X-rays and thus produce "radiation shadows" that lead to pronounced stripe artifacts throughout the reconstructed image. Metal artifacts are minimized by: Selection of a sharper convolution core (higher kernel number) Use of 140 kV tube voltage Use of iMAR (Iterative Metal Artifact Reduction) technology Metal Artifacts [audf_018.mp3] Metal artifacts appear when the scanned region contains metal. Metals such as gold can absorb the X-rays almost completely, leading to stripe artifacts in the reconstructed image. This artifact can be reduced by using sharp kernels, by scanning with high kV, or by the use of iMAR technology. Iterative Metal Artifact Reduction reduces metal artifacts (caused, for example, by implants, artificial joints, or pacemakers) in various body regions without the need to increase the radiation dose. Criteria for Image Quality Metal Artifacts | Extended CT Scale (1/2) Normal Hounsfield scale: CT values from -1024 HU to +3071 HU Extension of the scale by factor 10 to -10240 HU to + 30710 HU Evaluation of higher-density metal is possible, e.g. for hip implants CT value = 6000 HU Extended CT Scale (1/2) [audf_019.mp3] Evaluation of higher-density metal objects like hip replacements is possible with the use of the tenfold extended CT scale. Criteria for Image Quality Metal Artifacts | Extended CT Scale (2/2) Extended CT scale is an option in Somaris 5 and Somaris 7 systems. In Somaris 10 systems it is not an option as a wide-ranging CT scale is always active with values from -8192 HU to +57343 HU. Somaris 5 and 7 systems Extended CT Scale (2/2) [audf_020.mp3] Extended CT scale is an option in Somaris 5 and 7 scanners but it is not available in Somaris 10 since the scanners in this group have a wide-ranging CT scale that is always active. Define the Factors Influencing Image Quality in CT Factors Influencing Image Quality CT Image Quality | Influences System User Parameters Patient CT Image Quality | Influences [audf_021.mp3] This picture gallery gives you a preview of the next major topic: the factors that influence CT image quality. Decisive factors are the actions of persons (such as the system user and the patient) as well as the technical setup (such as the system status and the CT parameter settings). Influences on Image Quality System | Technical Influences Without proper calibration, individual detector elements can produce different signal amplitudes at the same radiation intensity. This can be seen in the images as ring artifacts. Therefore, a calibration needs to be performed every 24 hours at the latest. New in Somaris 10 scanners, a calibration reminder will pop up one hour after the check-up. After this calibration, no further calibrations are needed for the day, unless problems like ring artifacts occur or the system gets restarted. Technical Influences [audf_022.mp3] The image quality is affected by technical parameters. CT scanners must be calibrated every 24 hours to ensure good image quality. If no calibration is performed, individual detectors can produce different signal amplitudes at the same radiation intensity and the already mentioned ring artifacts will appear in the images. A new feature in Somaris 10 scanners is that a calibration reminder will pop up one hour after the check-up. After this calibration, no further calibrations are needed for the day, unless problems like ring artifacts occur or the system gets restarted. Influences on Image Quality | User The system user is responsible for: Preparation of the patient for the examination Patient positioning Choosing the correct protocol Adjusting the parameters User [audf_023.mp3] The scanner user can also affect the image quality. It is the user’s responsibility to ensure a correct patient preparation and positioning, select the appropriate clinical protocol, and adjust the parameters accordingly. Influences on Image Quality | Parameters mAs kV Kernel Slice thickness Scan time Field of View (FoV) Parameters [audf_024.mp3] The scan and image reconstruction parameters are key to obtaining a good image. Among others, milliampere second (mAs) settings, kilovoltage, kernel, slice thickness, scan time, and Field of View affect the image quality. Influences on Image Quality Parameters | mAs (1/2) Soft Tissue Diagnostics Representation of small structures with low density differences (low contrast resolution) CT values of adjacent structures are very similar → noise must be kept as low as possible Requires higher mAs High Contrast Diagnostics Display of small structures with large differences in density (high contrast resolution) CT values are very high compared to surrounding tissues → some level of noise is acceptable Low mAs sufficient mAs (1/2) [audf_025.mp3] In soft tissue diagnostics, the representation of small structures with low density differences requires high mAs settings. Since the CT values of surrounding tissue are very similar, noise in the image must be kept to a minimum. In order to display small structures with large differences in density as is the case in high contrast diagnostics, low mAs settings are sufficient. Since the CT values of the structures of interest are very high compared to surrounding tissues, some level of noise is acceptable. Influences on Image Quality Parameters | mAs (2/2) 180 mAs 45 mAs Noise Dose The higher the dose, the lower the noise! Low mAs value → High noise Quadruple mAs value → Half noise Doubling the dose reduces noise by a factor of 1.4 mAs (2/2) [audf_026.mp3] Low mAs values lead to noisy images. The graph shows the correlation between radiation dose and noise. The rule of thumb is: The higher the dose, the lower the noise! Influences on Image Quality Parameters | Kilovoltage (kV) The higher the voltage, the more the spectrum shifts to higher energy levels. This leads to a lower attenuation of the X-ray beams. If kV values are too high, the contrast deteriorates ("kV turns gray"). kV settings have a great influence on the patient dose. 80 kV 140 kV Kilovoltage (kV) [audf_027.mp3] The higher the voltage, the more the spectrum shifts to higher energy levels, leading to a lower attenuation of the X-ray beams. High kV deteriorates the contrast in the image, giving rise to the radiographers’ expression: “kV turns gray”. Kilovoltage settings have a great influence on the patient dose. Influences on Image Quality Parameters | Kernels Smooth Kernel Sharp Kernel Smooth kernels deliver low-definition images with low noise. Sharp kernels deliver sharp-definition images with high noise. 10 30 50 70 90 smooth low high Noise sharp Image definition Kernels [audf_028.mp3] As you can see from the correlation between noise and image definition in the graph and the comparison between the two CT images of the lung: Smooth kernels deliver low-definition images with low noise. Sharp kernels deliver sharp-definition images with high noise. Influences on Image Quality Parameters | Slice Thickness (1/2) The choice of slice thickness is a compromise between edge sharpness and noise because they influence each other. Low noise Better low contrast resolution Poorer edge sharpness Increased partial volume artifacts Better edge sharpness Better high contrast resolution Reduced partial volume artifacts Higher noise Poorer low contrast resolution Thick slice leads to: Thin slice leads to: Slice Thickness (1/2) [audf_029.mp3] The choice of slice thickness is a compromise between edge sharpness and noise as they influence each other. Thicker slices offer lower noise and better low contrast resolution while sacrificing edge sharpness. Partial volume artifacts are more common when using thick slices. On the other hand, thin slices offer better edge sharpness and better high contrast resolution. Partial volume artifacts are less common but the trade-off is that images will have higher noise and poor low contrast resolution. Influences on Image Quality Parameters | Slice Thickness (2/2) Thicker slices result in less noise and better contrast in soft tissue studies. Thinner slices result in better geometric resolution. 3 mm slice 10 mm slice 5 mm slice 1 mm slice Slice Thickness (2/2) [audf_030.mp3] As you can see in the images, thicker slices have less noise and better contrast in soft tissue studies, and thinner slices have much better geometric resolution. Influences on Image Quality Parameters | Scan Time The shorter the scan time, the less likely motion artifacts are. strong moderate short long Scan time (s) Artifact Scan Time [audf_031.mp3] The scan time determines the speed and temporal resolution of the acquisition. This graph shows the correlation between scan time and the occurrence of motion artifacts. The shorter the scan time, the less likely motion artifacts are. Influences on Image Quality Parameters | Field of View (FoV) (1/2) The selection of appropriate FoV values has a big impact on the optimal visualization of image details. The raw data is always recorded from the entire measuring field. Consequently, an image section can always be calculated directly from the raw data. The image detail can be calculated anywhere within the 500 mm FoV. Large FoV Small FoV Field of View (FoV) (1/2) [audf_032.mp3] The last parameter we would like to address is Field of View. The selection of appropriate Field of View values has a big impact on the optimal visualization of image details. The raw data is always recorded from the entire measuring field. Consequently, an image section can be calculated from the raw data, just as the image detail can be calculated anywhere within the 500-millimeter Field of View. Influences on Image Quality Parameters | Field of View (FoV) (2/2) Only zoom: Purely optical enlargement of the image data (zoom), which can lead to blurred images. Real reconstruction with smaller FoV: A section of the overall raw data is reconstructed to improve detail sharpness. Field of View (FoV) (2/2) [audf_033.mp3] Let’s now compare using the magnification tool (that is, the optical zoom function) with performing real reconstruction directly from the raw data with a smaller Field of View. As you can see in the two CT images from the lung, purely optical enlargement of the image data (or zoom) leads to a blurred image impression while real reconstruction with a smaller Field of View shows improved detail sharpness. Influences on Image Quality | Patient Patient size (diameter) Patient cooperation Patient [audf_034.mp3] Image quality is also influenced by the patient, especially by the patient size and the patient cooperation. Influences on Image Quality | Patient Size The image noise doubles for every 8 cm that the patient's diameter increases. Patient diameter Noise 400% 300% 200% 100% 30 cm 34 cm 38 cm 42 cm 46 cm Patient Size [audf_035.mp3] The image noise doubles for every 8 centimeters that the patient’s diameter increases. Influences on Image Quality | Patient Cooperation Patient cooperation is essential for achieving a good image quality. Bad cooperation might necessitate adjustments of scan parameters which might affect image quality Example: Change to shorter scan times due to a patient’s short breath holding ability Patient Cooperation [audf_036.mp3] Patient cooperation is essential for achieving a good image quality. Bad cooperation might necessitate adjustments of scan parameters which in turn might affect image quality. As an example: Shorter scan times will help with the CT exam of patients who cannot hold their breath for a long time. Define the Factors Influencing Image Quality in CT Specify the Criteria Affecting Image Quality in CT Course Review Congratulations. You have completed the CT Image Quality course. Select the objectives listed below to review the material before proceeding to the final assessment. Additionally, a full course review is available in the Resources tab. 1 1 1 2 2 2 Course Review Define the Factors Influencing Image Quality in CT Table with 2 columns and 5 rows Influence Description System Technical influences: Calibration needs to be performed every 24 hours at the latest! New in Somaris 10 scanners: A calibration reminder will pop up one hour after the check-up. After this calibration, no further calibrations are needed for the day, unless problems like ring artifacts occur or the system gets restarted. User Responsibilities of the system user: Preparation of the patient for the examination Patient positioning Choosing the correct protocol Adjusting the parameters Parameters Tube current (mAs): Soft tissue diagnostics require higher mAs, for high contrast diagnostics low mAs are sufficient. Tube voltage (kV): kV settings have a big influence on the patient dose. Kernel: Smooth kernels deliver low-definition images with low noise, sharp kernels deliver sharp-definition images with high noise. Slice thickness: Thick slices leading to lower noise, but poorer edge sharpness. Thin slices leading to better edge sharpness, but higher noise. Scan time: The shorter the scan time, the less likely motion artifacts are. Field of View (FoV): Reconstruction of an image detail with smaller FoV improves detail sharpness. Patient Patient size (diameter): Image noise doubles for every 8 cm the patient's diameter increases. Patient cooperation: Essential for achieving a good image quality. Bad cooperation might necessitate adjustments of scan parameters which might affect image quality. Specify the Criteria Affecting Image Quality in CT Table with 3 columns and 6 rows Image Quality Criteria Description Example Contrast High contrast: > 100 HU, low contrast: < 10 HU High contrast resolution required for good image quality in bone and lung structures. Low contrast resolution required for good image quality in soft tissue such as liver and brain. Temporal Resolution (TR) TR = Time required by the CT scanner to generate the data for an image, determined by the rotation time (RT) of the gantry. Single Source scanners: TR = Fastest RT / 2 Dual Source scanners: TR = Fastest RT / 3.75 The faster the RT, the higher the TR. SOMATOM Edge: TR = 280ms/2 = 140ms SOMATOM Drive: TR = 280ms/3.75 = 75ms Sharpness Sharpness of an object in relation to the surrounding tissue, depending on rotation time (RT), kernel, slice thickness and radiation dose. Noise Image noise is superimposed on the image and leads to a snowy impression. Intensity is influenced by the number of X-ray quanta reaching the detector, thus contributing to image generation. This number is determined by tube current, tube voltage, slice thickness, collimation, kernel and object thickness. Artifacts Motion artifacts caused by long scan time Partial volume artifacts caused by wrong slice thickness Beam hardening artifacts caused by wrong scan protocol Ring artifacts caused by defective detector elements Metal artifacts caused by implants or metallic foreign objects Please note that the learning material is for training purposes only. For the proper use of the software or hardware, please always use the Operator Manual or Instructions for Use (hereinafter collectively “Operator Manual”) issued by Siemens Healthineers. This material is to be used as training material only and shall by no means substitute the Operator Manual. Any material used in this training will not be updated on a regular basis and does not necessarily reflect the latest version of the software and hardware available at the time of the training. The Operator Manual shall be used as your main reference, in particular for relevant safety information like warnings and cautions. Please note: Some functions shown in this material are optional and might not be part of your system. Certain products, product related claims or functionalities (hereinafter collectively “Functionality”) may not (yet) be commercially available in your country. Due to regulatory requirements, the future availability of said Functionalities in any specific country is not guaranteed. Please contact your local Siemens Healthineers sales representative for the most current information. The reproduction, transmission or distribution of this training or its contents is not permitted without express written authority. Offenders will be liable for damages. All names and data of patients, parameters and configuration dependent designations are fictional and examples only. All rights, including rights created by patent grant or registration of a utility model or design, are reserved. © Siemens Healthcare GmbH 2023 Siemens Healthineers Headquarters\Siemens Healthcare GmbH\Henkestr. 127\ 91052 Erlangen, Germany\Telephone: +49 9131 84-0\siemens-healthineers.com Disclaimer Disclaimer Assessment Assessment Welcome to the assessment. For each question, select your answer and then select Submit. You will have 3 attempts to take this assessment and to successfully pass this course. You must receive a score of 80% or higher. You will receive your score when you have completed the assessment. Start Assessment Contrast < 100 HU = High Contrast Contrast > 100 HU = High Contrast Contrast < 10 HU = High Contrast Contrast > 10 HU = Low Contrast Select the correct statement. Question 1 of 5 Select the best answer. Multiple Choice Question kV settings have a big influence on the patient dose. mAs settings have a big influence on the patient dose. Temporal resolution has a big influence on the patient dose. All of the above Select the correct statement. Question 2 of 5 Select the best answer. Multiple Choice Question Weekly Every 48 h Every 24 h System calibration must be done by Siemens Healthineers Service annually Calibration of the Somaris 5 and 7 systems should take place ... Question 3 of 5 Select the best answer. Multiple Choice Question TR = Slowest Rotation Time / 2 TR = Fastest Rotation Time / 2 TR = Slowest Rotation Time / 4 TR = Fastest Rotation Time / 4 What is the equation of temporal resolution for Single Source scanners? Question 4 of 5 Select the best answer. Multiple Choice Question Partial volume artifact Motion artifact Stripe artifact Ring artifact Which artifact appears in the CT image, if too many detector elements are defective? Question 5 of 5 Select the best answer. Multiple Choice Question Retry Assessment Results %Quiz2.ScorePercent%% %Quiz2.PassPercent%% Continue YOUR SCORE: PASSING SCORE: Assessment Results You have exceeded your number of assessment attempts. Exit You did not pass the course. Select Retry to continue. Congratulations. You passed the course. Exit To access your Certificate of Completion, select the Launch button drop down on the course overview page. You can also access the certificate from your PEPconnect transcript. You have completed the CT Image Quality Online Training. Completion CT Image Quality I HOOD05162003154120 1.1 CT Image Quality Online Training 1.2 Criteria Affecting Image Quality 1.3 CT Image Quality (IQ) Criteria 1.4 Contrast 1.5 High Contrast Resolution 1.6 Low Contrast Resolution 1.7 Temporal Resolution (1/2) 1.8 Temporal Resolution (2/2) 1.9 Sharpness 1.10 Noise 1.11 Artifacts 1.12 Motion Artifacts 1.13 Partial Volume Artifact (1/3) 1.14 Partial Volume Artifact (2/3) 1.15 Wrong HU Values (3/3) 1.16 Beam Hardening Artifact 1.17 Ring Artifacts 1.18 Stripe Artifacts 1.19 Metal Artifacts 1.20 Extended CT Scale (1/2) 1.21 Extended CT Scale (2/2) 1.22 Factors Influencing Image Quality 1.23 CT Image Quality | Influences 1.24 Technical Influences 1.25 User 1.26 Parameters 1.27 mAs (1/2) 1.28 mAs (2/2) 1.29 Kilovoltage (kV) 1.30 Kernels 1.31 Slice Thickness (1/2) 1.32 Slice Thickness (2/2) 1.33 Scan Time 1.34 Field of View (FoV) (1/2) 1.35 Field of View (FoV) (2/2) 1.36 Patient 1.37 Patient Size 1.38 Patient Cooperation Course Review and Assessment 1.39 Course Review 1.40 Disclaimer 2 Assessment