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Iterative Metal Artifacts Reduction in CT

This online training will introduce you to the basics of iterative metal artifacts reduction in CT.

Continue Button Welcome Master Template HOOD05162003052540 | Effective Date: 26-Nov-2019 ? Iterative Metal Artifacts Reduction in CT Online Training This online training will introduce you to the basics of iterative metal artifacts reduction in CT, and will cover the following three learning objectives: Identify Metal Artifacts in CT Images 1 Learn about Protocols, Kernel and User Interface 3 Understand the Principles of Correction 2 Welcome audf_imar_title_page_01.mp3 Welcome to the Iterative Metal Artifacts Reduction in CT Online Training. This online training will introduce you to the basics of iterative metal artifacts reduction in CT, and will cover the following three learning objectives : Metal Artifacts in CT Images Identify Metal Artifacts in CT Images Iterative Metal Artifacts Reduction in CT Online Training Identify Metal Artifacts in CT Images audf_imar_met_art_intro_02.mp3 ? Identify Metal Artifacts in CT Images General problem with metal artifacts Physical effects that generate metal artifacts Approaches F29 Identify Metal Artifacts in CT Images audf_imar_met_art_overview_03.mp3 This chapter will offer you an explanation regarding the nature of metal artifacts in CT images. Different approaches to their reduction or removal will be addressed. ? Metal Artifacts in CT Images Four physical effects that generate metal artifacts: Beam hardening The total attenuation is underestimated. Dark streaks and bands appear in areas with the highest attenuation of X-rays. Scatter Scattered photons lead to the wrong registration in the detector. The appearance in this case is similar to that of beam hardening artifacts. Undersampling Due to the large density differences between metal and the surrounding tissue, significantly higher sampling would be necessary. This results in thin streaks (so-called edge artifacts). Photon starvation Fewer photons pass through the object, which results in signal loss. Because of this, white and dark thin noise streaks appear. F29 Metal Artifacts in CT Images audf_imar_met_art_phys_effect_04.mp3 There are four physical effects that generate metal artifacts:   Beam hardening: The total attenuation is underestimated. Dark streaks and bands appear in areas with the highest attenuation of X-rays. Scatter: Scattered photons lead to the wrong registration in the detector. The appearance in this case is similar to that of beam hardening artifacts. Undersampling: Due to the large density differences between metal and the surrounding tissue, significantly higher sampling would be necessary. This results in thin streaks (so-called edge artifacts). Photon starvation: Fewer photons pass through the object, which results in signal loss. Because of this, white and dark thin noise streaks appear. ? Metal Artifacts in CT Images There are different approaches regarding the reduction or removal of metal artifacts during acquisition and post-processing. These include: Selection of more adequate scan parameters Beam hardening correction The general problem connected with metal artifacts is that the information in the detector readings behind the metal is unusable. These metal shadows need to be replaced by some surrogate data (e.g. linear interpolation). Drawback: Insertion of new artifacts → No valuable results for diagnostics or therapy planning. F29 Metal Artifacts in CT Images audf_imar_met_art_approach_05.mp3 There are different approaches regarding the reduction or removal of metal artifacts during acquisition and post-processing.   These include: Selection of more adequate scan parameters, or Beam hardening correction.   The general problem connected with metal artifacts is that the information in the detector readings behind the metal is unusable.   These metal shadows subsequently need to be replaced by some surrogate data (for instance, by means of linear interpolation).   There is, however, a significant drawback: In doing so, we insert new artifacts, which makes it impossible to obtain valuable results for diagnostics or therapy planning.   Principles of Correction Understand the Principles of Correction Iterative Metal Artifacts Reduction in CT Online Training Understand the Principles of Correction audf_imar_princ_corr_intro_07.mp3 ? MARIS MARIS – previous version of iMAR (iterative Metal Artifact Reduction) Metal Artifact Reduction (MAR) in Image Space (MARIS) Correcting one of the primary causes of metal artifacts: beam hardening Multiple steps based on an analysis of the projections from the CT acquisition F29 MARIS audf_imar_met_art_maris_06.mp3 The previous version of iMAR was termed MARIS which stands for Metal Artifact Reduction in Image Space.   Its major function is to correct one of the primary causes of metal artifacts, namely beam hardening.   It includes multiple steps based on an analysis of the projections from the CT acquisition. ? Understand the Principles of Correction MARIS Principles of Correction Examples iMAR Approaches Linear Interpolation MAR Normalized MAR Frequency Split MAR H:\My Documents\Talks\RSNA2013\64977 (2).png H:\My Documents\Talks\RSNA2013\64977 (2).png FBP (Filtered Back Projection) iMAR Principles of Correction audf_imar_princ_corr_overview_08.mp3 This chapter focuses on the principles of correction in MARIS. Some examples will be presented. In the second part of the chapter, you will be offered some insights into the iMAR functionality.   Full polychromatic attenuation ‘P’ for all water  bone combinations Misfit of metal attenuation ‘B’ due to beam hardening Correction value as a function of P and B  Stored in a lookup table  Both P and B derived from CT image using Fourier-based forward projection Polychromatic X-ray beam  simulates real CT measurement Table with 5 columns and 5 rows P B Correction values 2D lookup table MARIS – Principle of Correction P Metal Water ? MARIS - Principle of Correction audf_imar_princ_corr_polychr_09.mp3 If we simulate a polychromatic (CT-like) beam P and use a phantom as shown in the picture, we can calculate the attenuation for every possible thickness combination of metal (namely metal, contrast or bone) and water (that is, soft tissue).   Correction values as a function of P and the misfit of metal attenuation B will be stored in a lookup table.   MARIS – Principle of Correction Correction Algorithm → Full attenuation data is corrected value by value using a two-dimensional lookup table → Correction is based on relative contribution of metal versus tissue (2 components) → Correction is only applied to the projections where metal has been detected Improved image Correction Algorithm Image Recon-struction Full attenuation P Metal attenuation B Original image Forward Projection (Fourier) Forward Projection (Fourier) Segmentation of metal (thresholds) ? MARIS - Principle of Correction audf_imar_princ_corr_algorithm_10.mp3 The correction takes place according to the following principle:   Firstly, a standard image is reconstructed without correcting the errors introduced by the metal. Secondly, segmentation of metal pixels takes place by means of the thresholding process. The correction values shall be applied in accordance with the P/B combination (the respective values are stored in the 2D lookup table). MARIS – Example: Phantom ? Water improved MARIS - Example: Phantom audf_imar_princ_corr_ex_phantom_11.mp3 In order to handle different types of metal, there are several levels of intensity.   Titanium, for instance, creates a weaker beam hardening effect, whereas stainless steel creates a stronger one.   MARIS – Example: Spine Fixation (Titanium) Standard (D30) MARIS* (M30) MARIS* (M31) MARIS* (M32) MARIS* (M33) MARIS* (M34) Courtesy: Dr. Rainer Raupach; HIM CR R&D PA SC ? MARIS - Example: Spine Fixation (Titanium) audf_imar_princ_corr_ex_spine_12.mp3 The user can choose between five different intensity levels of the algorithm. Each level corresponds to a certain degree of amplification of the correction values in the table.   Please note that under- or overcorrection shall be avoided.   MARIS – Example: Hip Prosthesis (Unknown Material) Standard (D30) MARIS* (M32) MARIS* (M33) MARIS* (M34) Best result Correction too weak Overcompensated Courtesy: Dr. Rainer Raupach; HIM CR R&D PA SC ? MARIS - Example: Hip Prothesis audf_imar_princ_corr_ex_hip_13.mp3 In this application, the user can choose between three different intensity levels of the algorithm. Each level corresponds to a certain degree of amplification of the correction values in the table.   Under- or overcorrection shall be avoided here as well.   ? iMAR iMAR combines 3 successful approaches: Beam hardening correction Normalized sinogram inpainting Frequency split The correction process is iteratively refined by repeating the normalized sinogram inpainting and the mixing steps up to six times. Courtesy of Hirslanden Klinik, Zurich Switzerland without iMAR1 with iMAR1 iMAR audf_imar_princ_corr_approach_14.mp3 iMAR combines three successful approaches, namely:   Beam hardening correction in sinogram regions with less severe metal attenuation, Normalized sinogram inpainting in sinogram regions with high metal attenuation, and Frequency split mixing back in some of the image noise, texture and sharp detail that may have potentially been lost during the inpainting.   The correction process is iteratively refined by repeating the normalized sinogram inpainting and the frequency split mixing steps up to six times. ? iMAR Correction of soft tissue HU values is significantly higher. H:\My Documents\Talks\RSNA2013\64977 (2).png H:\My Documents\Talks\RSNA2013\64977 (2).png FBP iMAR iMAR audf_imar_princ_corr_soft_tissue_15.mp3 The correction of Hounsfield unit values of soft tissue with iMAR is significantly higher. Compare the image quality of a filtered back projection without correction and the new iMAR image. ? iMAR Reduction in streak artifacts H:\My Documents\Talks\RSNA2013\Abe2 (2).png H:\My Documents\Talks\RSNA2013\Abe2 (2).png FBP iMAR iMAR audf_imar_princ_corr_streak_16.mp3 Here you can see the reduction in streak artifacts. ? Linear Interpolation MAR Linear sinogram interpolation in metal trace (Kalender et al., 1987) FBP image Metal mask Corrected image Linear Interpolation MAR audf_imar_princ_corr_lin_int_17.mp3 The first idea behind linear interpolation was to obtain a corrected image. Please take a close look at the orange interpolation in the histogram.   ? Linear Interpolation MAR Linear sinogram interpolation in metal trace (Kalender et al., 1987) Ima_0_cut.png Ima_NMAR_cut.png Reduction in streak artifacts … but at the same time … introduction of new artifacts tangentially to high contrast objects Linear Interpolation MAR audf_imar_princ_corr_lin_int_2_18.mp3 A reduction in streak artifacts could be observed, but at the same time new artifacts were added tangentially to high-contrast objects.   ? Linear Interpolation MAR Interpolation performed on flat and structureless normalized sinogram (Meyer et al., 2010) FBP image “Prior” image Corrected image Normalization Interpolation on normalized sinogram Denormalization A prior image is generated from the original reconstructed image or pre-corrected image Linear Interpolation MAR audf_imar_princ_corr_lin_int_3_19.mp3 Another approach to metal artifacts reduction is to perform an interpolation on a flat and structureless normalized sinogram. ? Normalized Metal Artifact Reduction (NMAR) Interpolation performed on flat and structureless normalized sinogram (Meyer et al., 2010) Ima_0_cut.png Ima_NMAR_cut.png Minimal introduction of low-frequency artifacts … but at the same time … loss of detail close to metal implants Normalized Metal Artifact Reduction (NMAR) audf_imar_princ_corr_normalized_20.mp3 The normalized metal artifact reduction involves minimal introduction of low-frequency artifacts, but at the same time loss of detail is observed close to metal implants.   ? Frequency Split MAR Combining low frequencies of MAR image with high frequencies of FBP image (Meyer et al., 2010) FBP FBP highpass Frequency Split MAR audf_imar_princ_corr_freq_split_21.mp3 The frequency split metal artifact reduction is a method that combines low frequencies of a metal artifact-reduced image with high frequencies of a filtered backprojection image.   ? Frequency Split MAR Combining low frequencies of MAR image with high frequencies of FBP image (Meyer et al., 2010) Natural image impression and preservation of edge information … but at the same time … some low-frequency artifacts still remain Frequency Split MAR audf_imar_princ_corr_freq_split_2_22.mp3 What we observe here is a natural image impression and preservation of edge information, but at the same time there are still some low-frequency artifacts.   ? Frequency Split MAR Iterative MAR with normalized interpolation, frequency split and adaptive sinogram mixing Input image Metal detection Prior image calculation Frequency split (Meyer et Al.) 2012 iMAR image Beam hardening correction Normalized interpolation (Meyer et Al.) 2010 Adaptive sinogram mixing P P P R P R iMAR iterative correction loop projection reconstruction Image space Image space Projection space Projection space Frequency Split MAR audf_imar_princ_corr_freq_split_loop_23.mp3 The methods of iterative metal artifact reduction with normalized interpolation, frequency split and adaptive sinogram mixing are now combined into the iMAR iterative correction loop. Protocols, Kernel and User Interface Learn about Protocols, Kernel and User Interface Iterative Metal Artifacts Reduction in CT Online Training Learn about Protocols, Kernel and User Interface audf_imar_prot_ker_ui_intro_24.mp3 ? Learn about Protocols, Kernel and User Interface Scan protocols SOMARIS 5 SOMARIS 7 SOMARIS X Reconstruction kernel Supported actions Unsupported actions Protocols, Kernel and User Interface audf_imar_prot_ker_ui_overview_25.mp3 The last chapter will address the issues of scan protocols, different types of kernels, and user interfaces. ? SOMARIS 5 | CT Scanner Portfolio SOMATOM Scope SOMATOM Perspective SOMATOM Scope Power P:\03_TransferProjekte\SI_CT\SI-CT021_ECR\01_Input\02_Kunde\03_Bildpool-Siemens\lowRes-pptx\SH_CT_38740_14_V3.jpg P:\03_TransferProjekte\SI_CT\SI-CT021_ECR\01_Input\02_Kunde\03_Bildpool-Siemens\lowRes-pptx\SH_CT_38740_14_V3.jpg SOMARIS 5 I CT Scanner Portfolio audf_imar_somaris5_portfolio_26.mp3 Here you can see the SOMARIS 5 Scanner Portfolio. ? SOMARIS 7 | CT Scanner (Single Source) Portfolio SOMATOM Definition AS SOMATOM Definition AS+ SOMATOM Confidence SOMATOM Definition Edge SOMATOM Edge Plus SOMARIS 7 I CT (Single Source) Portfolio audf_imar_somaris7_portfolio_27.mp3 This is the SOMARIS 7 Single Source Scanner Portfolio. ? SOMARIS 7 | CT Scanner (Dual Source) Portfolio SOMATOM Definition Flash SOMATOM Force SOMATOM Drive \\ww005.siemens.net\meddfsroot\DE\MED\CT\apps\CRM-CTM-MarCom\Produkt_und_klinisches_Marketing\Drive\03_Images\02_3D_Renderings\01_FINAL\Healthineers\16_to_9_tif\SOMATOM_Drive_FullHD_0000.tif SOMARIS 7 I CT Scanner (Dual Source) Portfolio audf_imar_somaris7_dual_portfolio_28.mp3 And here is the SOMARIS 7 Dual Source Scanner Portfolio. ? SOMARIS X | CT Scanner Portfolio SOMATOM go.All SOMATOM go.Top SOMATOM go.Sim SOMATOM go.Open Pro SOMATOM X.cite SOMATOM go.Up SOMATOM go.Now SOMARIS X I CT Scanner Portfolio audf_imar_somarisX_portfolio_29.mp3 This is an overview of SOMARIS X Scanner. ? iMAR Scan protocol SOMARIS 5 & 7 scanners: Only one protocol is set with an iMAR reconstruction as default: Hip_iMAR. Other protocols require customization if an iMAR reconstruction is needed. iMAR reconstruction can be activated for any other scan protocol with the exception of UHR scans. SOMARIS X scanners: iMAR reconstruction can be activated for every scan protocol. iMAR audf_imar_prot_ker_ui_scan_prot_26.mp3 Some specifics shall be observed when working with scan protocols. If SOMARIS 5 and SOMARIS 7 scanners are used:   Only one protocol will be set with an iMAR reconstruction as default, namely: Hip_iMAR . Other protocols have to be customized if an iMAR reconstruction is needed. iMAR reconstruction can be activated for any other scan protocol with the exception of UHR  scans.   If SOMARIS 10 scanners are used: iMAR reconstruction can be activated for every scan protocol.   ? iMAR – SOMARIS 7 * Recon parameter iMAR can be found in the Recon tab card. Symbol before VB10: Symbol since VB10: * SOMATOM Definition AS, SOMATOM Confidence, SOMATOM Definition AS+, SOMATOM Definition Edge, SOMATOM Edge Plus, SOMATOM Definition Flash, SOMATOM Drive, SOMATOM Force iMAR - SOMARIS 7 audf_imar_prot_ker_ui_recon_par_27.mp3 In SOMARIS 7 scanners, the iMAR function can be found in the Recon tab card.   ? iMAR – SOMARIS X * Recon parameter iMAR can be found under the reconstruction parameter in the Image Impression tab card. * SOMATOM go.Now, SOMATOM go.UP, SOMATOM go.All, SOMATOM go.Sim, SOMATOM go.Top, SOMATOM go.Open Pro, SOMATOM X.cite iMAR - SOMARIS X audf_imar_prot_ker_ui_image_imp_28.mp3 If you use a SOMARIS 10 scanner, the iMAR function can be found under the reconstruction parameter in the Image Impression tab card. ? iMAR Important tip: The visual impression of images reconstructed with iMAR can differ from those reconstructed with a conventional method. Furthermore, the iMAR algorithm can occasionally introduce artifacts, particularly in the close vicinity of metal implants. Therefore, iMAR images are to be compared side by side with conventional image reconstructions. iMAR audf_imar_prot_ker_ui_tip_29.mp3 Please note that the visual impression of images reconstructed with iMAR can differ from images reconstructed by means of a conventional method.   Furthermore, the iMAR algorithm can occasionally introduce artifacts, particularly in the close vicinity of metal implants.   Therefore, iMAR images are to be compared side by side with conventional image reconstructions. ? iMAR – SOMARIS 7 * Artifact correction algorithm When iMAR is activated, different settings become available: Neuro coils Dental fillings Spine implants Shoulder implants Pacemaker Thoracic coils Hip implants Extremity implants * SOMATOM Definition AS, SOMATOM Confidence, SOMATOM Definition AS+, SOMATOM Definition Edge, SOMATOM Edge Plus, SOMATOM Definition Flash, SOMATOM Drive, SOMATOM Force iMAR - SOMARIS 7 audf_imar_prot_ker_ui_aca_som7_30.mp3 The following different iMAR settings are available for SOMARIS 7: Neuro coils Dental fillings Spine implants Shoulder implants Pacemaker Thoracic coils Hip implants, and Extremity implants ? iMAR – SOMARIS X Artifact correction algorithm When iMAR is activated, different settings become available: Neuro coils Dental fillings Spine implants Shoulder implants Pacemaker Thoracic coils Hip implants Extremity implants * SOMATOM go.Now, SOMATOM go.UP, SOMATOM go.All, SOMATOM go.Sim, SOMATOM go.Top, SOMATOM go.Open Pro, SOMATOM X.cite iMAR - SOMARIS X audf_imar_prot_ker_ui_aca_som10_31.mp3 The iMAR settings available for SOMARIS 10 are the same as with SOMARIS 7.  ? iMAR Series description & image text iMAR audf_imar_prot_ker_ui_series_32.mp3 iMAR will also be added to the series description.   ? iMAR Image text for … … Neuro coils: iMARne … Dental fillings: iMARde … Spine implants: iMARsp … Shoulder implants: iMARsh … Pacemaker: iMARpa … Thoracic coils: iMARth … Hip implants: iMARhi … Extremity implants: iMARex iMAR audf_imar_prot_ker_ui_image_text_33.mp3 There are also different image texts available with this feature. Please take a closer look at the slide.  ? iMAR Reconstruction kernel Depending on the software version, iMAR can be used with the following kernels: VC30 & VA48 (SOMARIS 5, SOMARIS 7): Head kernels – index of H42 and softer Body kernels – B41 and softer Dual energy kernels – D40 and softer All ASA, PFO and IR kernels – J41, I41, Q40 and softer Emotion: no iMAR available VC40 & VC50 (SOMARIS 5): H80, J80, B90, I80, D45, Q40 and softer VA62 (SOMATOM Drive): H60, J49, B70, I70, D50, Q40 and softer iMAR audf_imar_prot_ker_ui_rec_kernel_34.mp3 Depending on the software version, iMAR can be used with the following reconstruction kernels:   For VC30 and VA48, Head kernels have a resolution index lower than 42.   Body kernels use an index of B41 and softer. Dual energy kernels require an index of D40 and softer. All ASA, PFO and IR  kernels are J41, I41, Q40 and softer. No iMAR is available for Emotion.   The reconstruction kernels in VC40 and VC50 are H80, J80, B90, I80, D45, Q40 and softer.   In VA62, the kernels are H60, J49, B70, I70, D50, Q40 and softer.  ? iMAR Reconstruction kernel Cont.: VA50 (Force): no iMAR available VB20 is combined with VB10 (SOMARIS 7 also Force!): kernels with a resolution index smaller than 60 (e.g. Bf42) VA30 (SOMARIS X): kernels with a resolution index smaller than 44 (e.g. Br40) iMAR audf_imar_prot_ker_ui_rec_kernel_cont_35.mp3 The iMAR feature is not available for VA50. For VB10 and VB20, iMAR is available in all scanners (including SOMATOM Force) for kernels with a resolution index lower than 60, for example Bf42. As to VA30 in SOMARIS X scanners, this function is available with a resolution index lower than 44, for example Br40. ? iMAR Supported actions iMAR can be used with: SAFIRE (Sinogram Affirmed Iterative Reconstruction) ADMIRE (Advanced Modeled Iterative Reconstruction) Extended CT scale eFoV / HD FoV (Extended Field of View / High Definition Field of View) Direct DensityTM iMAR is always an option and needs a fast Image reconstruction system (IRS)! iMAR audf_imar_prot_ker_ui_support_36.mp3 iMAR can be used with the following supported actions:   SAFIRE / ADMIRE, Extended CT scale, Extended field of view or HD field of view, and Direct Density. iMAR is always an option and needs a fast IRS ! ? iMAR Unsupported actions There is no iMAR for: Scan control RTD iFluoro Osteo CARE bolus Test bolus UHR scans iMAR audf_imar_prot_ker_ui_unsupport_37.mp3 Some actions are not supported by iMAR and subsequently cannot be used with it. These actions are: Scan control, RTD, iFluoro, Osteo, CARE bolus, Test bolus, and UHR scans. Course Review ? Course Review Congratulations. You have completed the Iterative Metal Artifacts Reduction in CT course. Select the objectives listed below to review the material before proceeding to the final assessment. Learn about Protocols, Kernel and User Interface Understand the Principles of Correction Identify Metal Artifacts in CT Images 1 1 2 2 2 3 3 3 Course Review Visual impression of images reconstructed with iMAR can differ from those reconstructed with a conventional method. The iMAR algorithm can occasionally introduce artifacts, particularly in the close vicinity of metal implants  iMAR images are to be compared with additional conventional image reconstruction. Reconstruction kernel: Depending on software version, iMAR can be used with the different kernels Supported actions: iMAR can be used with: SAFIRE/ADMIRE, Extended CT scale, eFoV/HD FoV, Direct DensityTM Unsupported actions: There is no iMAR for: Scan control, RTD, iFluoro, Osteo, CARE bolus, Test bolus iMAR is always an option and needs a fast IRS! Learn about Protocols, Kernel and User Interface Table with 4 columns and 2 rows SOMARIS 7 SOMARIS X Both Scan Protocols Only one default protocol: Hip_iMAR Others require customization if iMAR reconstruction is needed iMAR can be found in the Recon tab card iMAR reconstruction can be activated for every scan protocol iMAR can be found under Image Impression tab card When iMAR is activated, different settings become available: Neuro coils, Dental fillings, Spine implants, Shoulder implants, Pacemaker, Thoracic coils, Hip implants, Extremity implants Image text e.g.: Neuro coils: iMARne, Pacemaker: iMARpa Understand the Principles of Correction Table with 2 columns and 2 rows MARIS Simulating a polychromatic (CT-like) beam P and use of a phantom, attenuation for every possible thickness combination of metal and water can be calculated Correction values as a function of P and the misfit of metal attenuation B get stored in lookup-table Correction takes place according to the following principle: Standard image is reconstructed without correcting errors by the metal Segmentation of metal pixels takes place by means of the thresholding process Correction values shall be applied in accordance with P/B combination iMAR Correction of soft tissue HU values with iMAR is significantly higher Reduction in streak artifacts Combines 3 successful approaches: Beam hardening correction, normalized sinogram inpainting, frequency split Linear Interpolation MAR: reduction in streak artifacts but new artifacts added tangentially to high-contrast objects, perform interpolation on a flat and structure-less normalized sinogram Normalized metal artifact reduction involves minimal introduction of low-frequency artifacts, but loss of detail close to metal implants Frequency split metal artifact reduction: combines low frequencies of a metal artifact reduced image with high frequencies of a filtered backprojection image natural image impression and preservation of edge information, but still some low-frequency artifacts iMAR iterative correction loop: combination of iterative metal artifact reduction methods with normalized interpolation, frequency split and adaptive sinogram mixing Identify Metal Artifacts in CT Images General problem: Information in the detector readings behind metal is unusable.  Metal shadows need to be replaced by some surrogate data. 4 physical effects generating metal artifacts: Beam hardening: total attenuation is underestimated, dark streaks and bands appear Scatter: Scattered photons lead to wrong registration in detector, appearance similar to beam hardening artifacts Undersampling: large density differences between metal and surrounding tissue, results in thin streaks (so-called edge artifacts) Photon starvation: Fewer photons pass through object, which results in signal loss, white and dark thin noise streaks appear Approaches regarding the reduction or removal of metal artifacts during acquisition and post-processing: Selection of more adequate scan parameters, beam hardening correction MARIS (Metal Artifact Reduction in Image Space) = previous version of iMAR: Correction of beam hardening Multiple steps based on analysis of projections from CT acquisition Disclaimer Disclaimer 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's Manual shall be used as your main reference, in particular for relevant safety information like warnings and cautions. 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. Copyright © Siemens Healthcare GmbH 2021 Siemens Healthineers Headquarters\Siemens Healthcare GmbH\Henkestr. 127\ 91052 Erlangen, Germany\Telephone: +49 9131 84-0\siemens-healthineers.com ? Disclaimer Assessment Assessment This assessment will test your retention of the presented content. A passing score of 80% or higher is required to complete the course and earn your certificate. You may repeat the assessment as many times as needed. Start ? Assessment Select the best answer. ? Question 1 of 5 iMAR stands for… iterative Metal Artifact Reduction iterative Metal Artifact Reconstruction iterative Metal Artifact Reformation iterative Metal Artifact Reset Multiple Choice Incorrect This is not correct. Incorrect This is not correct. Incorrect This is not correct. Incorrect This is correct. Select the best answer. ? Question 2 of 5 What are beam hardening artifacts? The total attenuation is underestimated. Dark streaks & bands appear where the X-rays are attenuated to the greatest degree. The total attenuation is overestimated. Dark streaks & bands appear where the X-rays are attenuated to the greatest degree. The total scatter is underestimated. Dark streaks & bands appear where the X-rays are attenuated to the greatest degree. The total attenuation is underestimated. Dark streaks & bands appear where the X-rays are attenuated to the least degree. Multiple Choice Incorrect This is not correct. Incorrect This is not correct. Incorrect This is not correct. Incorrect This is correct. Select the best answer. ? Question 3 of 5 Which is the default iMAR scan protocol of Siemens? Hip_iMAR Spine_iMAR Head_iMAR Pelvis_iMAR Multiple Choice Incorrect This is not correct. Incorrect This is not correct. Incorrect This is not correct. Incorrect This is correct. Select the best answer. ? Question 4 of 5 Which image text abbreviation does not exist with iMAR? iMARfe iMARde iMARsh iMARpa Multiple Choice Incorrect This is not correct. Incorrect This is not correct. Incorrect This is not correct. Incorrect This is correct. Select the best answer. ? Question 5 of 5 There is no iMAR for… iFluoro Dual Energy HD Field of View Direct Density Multiple Choice Incorrect This is not correct. Incorrect This is not correct. Incorrect This is not correct. Incorrect This is correct. Assessment Results YOUR SCORE: PASSING SCORE: Review Retry Retry Continue Continue Continue %Results.ScorePercent%% %Results.PassPercent%% ? Assessment Results You did not pass the course. Take time to review the assessment then select Retry to continue. Congratulations. You passed the course.. 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 Iterative Metal Artifacts Reduction in CT Online Training. Exit Completion Navigation Help Select the icon above to open the table of contents. Click Next to continue. Next Welcome Slide The timeline displays the slide progression. Slide the orange bar backwards to rewind the timeline. Click Next to continue. Next Timeline Select the X to close the pop-up. Click Next to continue. Next Layer Slide Select Submit to record your response. Click the X in the upper right corner to exit the navigation help. Assessment Slide Question Bank 1 HOOD05162003164840 Effective Date 05-Feb-2021 1 Welcome 1.1 Welcome 2 Metal Artifacts in CT Images 2.1 Identify Metal Artifacts in CT Images 2.2 Identify Metal Artifacts in CT Images 2.3 Metal Artifacts in CT Images 2.4 Metal Artifacts in CT Images 3 Principles of Correction 3.1 Understand the Principles of Correction 3.2 MARIS 3.3 Principles of Correction 3.4 MARIS - Principle of Correction 3.5 MARIS - Principle of Correction 3.6 MARIS - Example: Phantom 3.7 MARIS - Example: Spine Fixation (Titanium) 3.8 MARIS - Example: Hip Prothesis 3.9 iMAR 3.10 iMAR 3.11 iMAR 3.12 Linear Interpolation MAR 3.13 Linear Interpolation MAR 3.14 Linear Interpolation MAR 3.15 Normalized Metal Artifact Reduction (NMAR) 3.16 Frequency Split MAR 3.17 Frequency Split MAR 3.18 Frequency Split MAR 4 Protocols, Kernel and User Interface 4.1 Learn about Protocols, Kernel and User Interface 4.2 Protocols, Kernel and User Interface 4.3 SOMARIS 5 I CT Scanner Portfolio 4.4 SOMARIS 7 I CT (Single Source) Portfolio 4.5 SOMARIS 7 I CT Scanner (Dual Source) Portfolio 4.6 SOMARIS X I CT Scanner Portfolio 4.7 iMAR 4.8 iMAR - SOMARIS 7 4.9 iMAR - SOMARIS X 4.10 iMAR 4.11 iMAR - SOMARIS 7 4.12 iMAR - SOMARIS X 4.13 iMAR 4.14 iMAR 4.15 iMAR 4.16 iMAR 4.17 iMAR 4.18 iMAR 5 Course Review, Disclaimer and Assessment 5.1 Course Review 6.1 Disclaimer 7.1 Assessment

  • metal artifacts
  • IMAR
  • CT artifacts