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Edit Comment Close Premium member Presentation Transcript Slide 1: Basic Principles of CT Scanning The basics of CT : The basics of CT CT imaging chain System components Acquisition methods Image quality Applications X-ray: The beginning : X-ray: The beginning X-Rays founded in 1895 by Wilhelm Conrad Roentgen CT: The beginning : CT: The beginning CT founded in 1970 by Sir Godfrey Hounsfield Engineer with EMI, LTD. first applications were in neuroradiology CT Scanner : CT Scanner X-Ray modality used to the body in cross section Used to determine extent of trauma location and type of tumors status of blood vessels pre surgical planning CT System : CT System CT System : CT System Basic CT scanner components : Basic CT scanner components Gantry X-Ray Tube Detector Control Console Gantry : Gantry CT X-ray tube High voltage generator Detector array Data acquistion system Slip ring The CT X-ray Tube : The CT X-ray Tube Anode heat capacity 3.5 MHU up to 6.5 MHU Determines maximum mAs Determines volume length Dictates generator size Detector Elements : Detector Elements Capture energy that has not been attenuated by the patient Control console : Control console Set scan parameters kVp, mA, scan time, reconstruction filter, etc. Set scan mode Digital radiograph, axial or volume Houses reconstructor Review and archive images Post-processing CT : CT CT - Computed Tomography CAT Scan - Computerized Axial Tomography Scanning methods : Scanning methods Digital projection AP, PA, Lat or Oblique projection Surview, Scanogram Conventional CT Axial Start/stop Volumetric CT Helical or spiral CT Continuous acquisition Digital Projection : Digital Projection X-ray tube and detector remain stationary Patient table moves continuously With X-rays “on” Produces an image covering a range of anatomy Similar to a conventional X-ray image, e.g. flat plate of the abdomen Image used to determine scan location Axial CT : Axial CT X-ray tube and detector rotate 360° Patient table is stationary With X-ray’s “on” Produces one cross-sectional image Once this is complete patient is moved to next position Process starts again at the beginning Volume CT : Volume CT X-ray tube and detector rotate 360° Patient table moves continuously With X-ray’s “on” Produces a helix of image information This is reconstructed into 30 to 1000 images Volume Scanning: Pitch : Volume Scanning: Pitch Advantages of Volume CT : Advantages of Volume CT More coverage in a breath-hold Chest, Vascular studies, trauma Reduced misregistration of slices Improved MPR, 3D and MIP images Potentially less IV contrast required Gapless coverage Arbitrary slice positioning Fundamentals of Multislice CT : Fundamentals of Multislice CT Multislice Fundamentals : Multislice Fundamentals Everything is better (R)esolution Z-axis, spatial, low contrast (S)peed Temporal - bolus capture, stopped motion (V)olume Thin slice - organ-specific coverage (P)ower Enough photons - uncompromising image quality Multislice Effectiveness : Single Slice = One 10mm slice per rotation Dual Slice = Two 5mm slices per rotation Quad Slice = Four 2.5mm slices per rotation Multislice Effectiveness Everything is better Resolution 2x 4x-8x Speed same same Volume same same Power same same Dual Quad Dual Slice Detector Optimized for 2 Slice Acquisition : . . single detector arc dual detector arc pre-patient collimation post-patient collimation x-ray tube focal spot _ _ _ Mx8000Dual Slice Dual Slice Detector Optimized for 2 Slice Acquisition Quad Detector Technology : Approximately 10% more efficient than matrix detectors Variable Wide Area Detector Asymmetrix™ Variable detector length Fixed detector length Quad Detector Technology Philips patented variable wide area detector Variable slice thickness 4 x 1mm 4 x 5mm 4 x 2.5mm 2 x 0.5mm 2 x 8mm 2 x 10mm Quad Technology : 8 Element 2-D array 4 Slices Quad Technology How it works Asymmetrix™ Technology : Asymmetrix™ Technology Variable slice thickness CT : CT CT attenuation information CT image quality Attenuation : Attenuation X-ray beam passes through patient Each structure attenuates X-ray beam differently According to individual densities Radiation received by detector varies according to these densities Density information : Density information Transferred from detector to CT computer(A to D converter) Reconstructed by computer into a cross-sectional image Displayed on screen Each pixel displayed on monitor has varying brightness The greater the attenuation, the brighter the pixel The less attenuation, the darker the pixel Density information : Density information Density values correspond to a range of numbers Hounsfield scale Window settings : Window settings Window width Determines range of CT numbers displayed on an image Values above this range = white Values below this range = black Window level Sets the center CT number displayed on the monitor Determines the location on the Hounsfield scale about which the window width will be centered CT image quality : CT image quality Spatial resolution Ability to resolve small objects in an image Measured in lp/cm Isotropic Imaging : Isotropic Imaging True 0.5mm Isotropic imaging CT image quality : CT image quality Contrast resolution Ability to differentiate small density differences in an image Post Processing Options : Post Processing Options Visualization ofvasculature in relation to pathology Show course of vessels Show stent placement Define vascular stricture Thin-Slice Spiral Neck : Cervical Spine Spiral Acquisition Rotation – 0.75 sec Coverage – 160 mm Pitch – 0.875 Acq. Time – 36 sec FOV – 250 mm ST – 1.0 mm Rec. Incr. – 0.6 mm Std Res. – 8 lp/cm 120 kV, 200 mAs CTDI100w – 39 mGy CTDIFDAw – 17 mGy Thin-Slice Spiral Neck Neuro-Angiography : Neuro-Angiography Circle of Willis Thin-Slice Spiral Lungs : Thin-Slice Spiral Lungs Renal Arteries : Renal Arteries Extended Spiral Acquisition : Ext. Spiral Acq. Spiral Acquisition UltraFast – 0.5 sec Coverage – 1400mm Pitch – 1.75 Acq. Time – 41.5 sec FOV – 420 mm ST –2.5 mm Rec. Incr. – 1.6 mm Std Res. – 8 lp/cm 120 kV, 96 mAs CTDI100w – 7.3 mGy CTDIFDAw – 4.9 mGy Extended Spiral Acquisition CT Scanners : CT Scanners Provide a window into the body Customer considerations How many patients Referring physicians Budget Upgrade expectations Philips has ALL the answers You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
Computed tomography basics allancavalcanti Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 9817 Category: Education License: All Rights Reserved Like it (3) Dislike it (0) Added: November 02, 2008 This Presentation is Public Favorites: 10 Presentation Description Computed tomography basics Comments Posting comment... By: biezar (11 month(s) ago) thanks for uploading......really helpful and knowledge giving Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Slide 1: Basic Principles of CT Scanning The basics of CT : The basics of CT CT imaging chain System components Acquisition methods Image quality Applications X-ray: The beginning : X-ray: The beginning X-Rays founded in 1895 by Wilhelm Conrad Roentgen CT: The beginning : CT: The beginning CT founded in 1970 by Sir Godfrey Hounsfield Engineer with EMI, LTD. first applications were in neuroradiology CT Scanner : CT Scanner X-Ray modality used to the body in cross section Used to determine extent of trauma location and type of tumors status of blood vessels pre surgical planning CT System : CT System CT System : CT System Basic CT scanner components : Basic CT scanner components Gantry X-Ray Tube Detector Control Console Gantry : Gantry CT X-ray tube High voltage generator Detector array Data acquistion system Slip ring The CT X-ray Tube : The CT X-ray Tube Anode heat capacity 3.5 MHU up to 6.5 MHU Determines maximum mAs Determines volume length Dictates generator size Detector Elements : Detector Elements Capture energy that has not been attenuated by the patient Control console : Control console Set scan parameters kVp, mA, scan time, reconstruction filter, etc. Set scan mode Digital radiograph, axial or volume Houses reconstructor Review and archive images Post-processing CT : CT CT - Computed Tomography CAT Scan - Computerized Axial Tomography Scanning methods : Scanning methods Digital projection AP, PA, Lat or Oblique projection Surview, Scanogram Conventional CT Axial Start/stop Volumetric CT Helical or spiral CT Continuous acquisition Digital Projection : Digital Projection X-ray tube and detector remain stationary Patient table moves continuously With X-rays “on” Produces an image covering a range of anatomy Similar to a conventional X-ray image, e.g. flat plate of the abdomen Image used to determine scan location Axial CT : Axial CT X-ray tube and detector rotate 360° Patient table is stationary With X-ray’s “on” Produces one cross-sectional image Once this is complete patient is moved to next position Process starts again at the beginning Volume CT : Volume CT X-ray tube and detector rotate 360° Patient table moves continuously With X-ray’s “on” Produces a helix of image information This is reconstructed into 30 to 1000 images Volume Scanning: Pitch : Volume Scanning: Pitch Advantages of Volume CT : Advantages of Volume CT More coverage in a breath-hold Chest, Vascular studies, trauma Reduced misregistration of slices Improved MPR, 3D and MIP images Potentially less IV contrast required Gapless coverage Arbitrary slice positioning Fundamentals of Multislice CT : Fundamentals of Multislice CT Multislice Fundamentals : Multislice Fundamentals Everything is better (R)esolution Z-axis, spatial, low contrast (S)peed Temporal - bolus capture, stopped motion (V)olume Thin slice - organ-specific coverage (P)ower Enough photons - uncompromising image quality Multislice Effectiveness : Single Slice = One 10mm slice per rotation Dual Slice = Two 5mm slices per rotation Quad Slice = Four 2.5mm slices per rotation Multislice Effectiveness Everything is better Resolution 2x 4x-8x Speed same same Volume same same Power same same Dual Quad Dual Slice Detector Optimized for 2 Slice Acquisition : . . single detector arc dual detector arc pre-patient collimation post-patient collimation x-ray tube focal spot _ _ _ Mx8000Dual Slice Dual Slice Detector Optimized for 2 Slice Acquisition Quad Detector Technology : Approximately 10% more efficient than matrix detectors Variable Wide Area Detector Asymmetrix™ Variable detector length Fixed detector length Quad Detector Technology Philips patented variable wide area detector Variable slice thickness 4 x 1mm 4 x 5mm 4 x 2.5mm 2 x 0.5mm 2 x 8mm 2 x 10mm Quad Technology : 8 Element 2-D array 4 Slices Quad Technology How it works Asymmetrix™ Technology : Asymmetrix™ Technology Variable slice thickness CT : CT CT attenuation information CT image quality Attenuation : Attenuation X-ray beam passes through patient Each structure attenuates X-ray beam differently According to individual densities Radiation received by detector varies according to these densities Density information : Density information Transferred from detector to CT computer(A to D converter) Reconstructed by computer into a cross-sectional image Displayed on screen Each pixel displayed on monitor has varying brightness The greater the attenuation, the brighter the pixel The less attenuation, the darker the pixel Density information : Density information Density values correspond to a range of numbers Hounsfield scale Window settings : Window settings Window width Determines range of CT numbers displayed on an image Values above this range = white Values below this range = black Window level Sets the center CT number displayed on the monitor Determines the location on the Hounsfield scale about which the window width will be centered CT image quality : CT image quality Spatial resolution Ability to resolve small objects in an image Measured in lp/cm Isotropic Imaging : Isotropic Imaging True 0.5mm Isotropic imaging CT image quality : CT image quality Contrast resolution Ability to differentiate small density differences in an image Post Processing Options : Post Processing Options Visualization ofvasculature in relation to pathology Show course of vessels Show stent placement Define vascular stricture Thin-Slice Spiral Neck : Cervical Spine Spiral Acquisition Rotation – 0.75 sec Coverage – 160 mm Pitch – 0.875 Acq. Time – 36 sec FOV – 250 mm ST – 1.0 mm Rec. Incr. – 0.6 mm Std Res. – 8 lp/cm 120 kV, 200 mAs CTDI100w – 39 mGy CTDIFDAw – 17 mGy Thin-Slice Spiral Neck Neuro-Angiography : Neuro-Angiography Circle of Willis Thin-Slice Spiral Lungs : Thin-Slice Spiral Lungs Renal Arteries : Renal Arteries Extended Spiral Acquisition : Ext. Spiral Acq. Spiral Acquisition UltraFast – 0.5 sec Coverage – 1400mm Pitch – 1.75 Acq. Time – 41.5 sec FOV – 420 mm ST –2.5 mm Rec. Incr. – 1.6 mm Std Res. – 8 lp/cm 120 kV, 96 mAs CTDI100w – 7.3 mGy CTDIFDAw – 4.9 mGy Extended Spiral Acquisition CT Scanners : CT Scanners Provide a window into the body Customer considerations How many patients Referring physicians Budget Upgrade expectations Philips has ALL the answers