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Dose Basics and the ACR Clinical Data Form

The purpose of this training is to review basic dose concepts, familiarize you with Siemens' dose and parameter terminology, and to help you find the information being requested when completing the Clinical Data Form for ACR Accreditation. This Web Based Training has been designed to correspond line by line with the parameters requested on the form, and we will use both a routine sequence head and a routine spiral abdomen protocol as examples.

Welcome to Siemens Dose Basics for CT ACR accreditation. The purpose of this training is to review basic dose concepts, familiarize you with Siemens' dose and parameter terminology, and to help you find the information being requested when completing the Clinical Data Form for ACR Accreditation. This web-based training has been designed to correspond line by line with the parameters requested on the form, and we will use both a routine sequence head and a routine spiral abdomen protocol as examples.   You have now completed the course Dose Basics for CT ACR Accreditation.  You should now be will be able to:  Understand Siemens dose and technical parameter terminology and how it applies to the ACR clinical form Know where to locate these technical parameters on the Siemens Examination User Interface (UI) for clinical form completion Apply various calculations in determining mA, mAs, effective mAs, and table feed/speed as they refer to spiral and sequence imaging Complete the ACR clinical data form for basic head and abdomen protocols   Select Next to take the assessment. You will be able to make three attempts to pass the assessment with a minimum score of 80%. Upon successful completion of this course, participants will be able to:  Understand Siemens dose and technical parameter terminology and how it applies to the ACR clinical form Know where to locate these technical parameters on the Siemens Examination User Interface (UI) for clinical form completion Apply various calculations in determining mA, mAs, effective mAs, and table feed/speed as they refer to spiral and sequence imaging Complete the ACR clinical data form for basic head and abdomen protocols Completion of any required ACR documentation for accreditation is the sole responsibility of the customer/applicant. This training is designed to assist the learner in identifying the ACR-requested information as it pertains to Siemens' CT scanners. Any scan parameters or other factors used or shown here are for example purposes only. As per the ACR accreditation form, all technical parameters submitted should come directly from the routine protocols of the form submitter.  Siemens holds no liability in the user's ACR accreditation process.   kVp/Kilovoltage kVp can be found: Defines the quantity of X-ray photons being used Defines the energy level or penetrating power of the X-ray beam Affects patient dose, image noise and contrast Influences CT numbers/HU in image On the Routine Card of the Examination User Interface (UI) On the Scan Card of the Examination User Interface (UI) On the Patient Protocol Page   mA/Milliamperage mA can be found: Defines the quality of X-ray photons being used Defines the actual X-ray tube current mA is NOT explicitly displayed on Siemens CT scanners mA for a spiral scan = effective mAs/Rotation Time x pitch Effective mAs and rotation time found on Patient Protocol Page Pitch found on the Scan Card of the examination user interface    Time Per Rotation(s) Rotation Time can be found: The time (in seconds) for the tube-detector system to make one complete 360 degree rotation On the Scan Card as Rotation Time On the Patient Protocol Page under the T.I. column  mAs mAs can be found:  X-ray tube current (mA) x Exposure time (s) Determines the number of photons or energy in the X-ray beam For spiral scanning, the applied dose is also influenced by the Pitch factor Applied dose is decreased when Pitch factor > 1 Applied dose is increased when Pitch factor < 1 Dose in spiral scanning must be adapted to Pitch factor Effective mAs takes into account the influence of Pitch on both the image quality and the dose Principle of Sure View concept On the Patient Protocol Page   Display Field of View (DFoV) DFoV can be found: The DFoV is the reconstructed Field of View of an image Determines how large or small the anatomy of interest appears Not the same as Zoom Shown in mm, reported in cm On the Recon Card - in mm - of the Examination UI    Reconstruction Algorithm/Kernel   Reconstruction Algorithm/Kernel can be found: Mathematical formula that defines sharpness and noise Allows various image impressions from the same scan data Kernels use image raw data, so not the same as Window/Level settings On the Recon Card of the Examination UI In the text of each reconstructed image   Helical (H) = Spiral Acquisition Type can be found: X-ray is on continuously as the patient is moved through the gantry on the table Volumetric scanning Flexibility of reconstructing the dataset with alternate parameters When Pitch displays on the Scan Card of the Examination UI Spiral Acquisition Image on Routine Card    Acquisition Slice Thickness/Z-Axis Collimation Acquisition Slice Thickness can be found:   Typically equal to the Collimation Slice Thickness Almost always reconstructed into other thicknessess (like 3s or 5s) As the latter half of the Acquisition Mode on the Routine or Scan Cards of the Examination UI On the Patient Protocol Page under the cSL column    Slice Collimation Examples: Acquisition mode 64 X 0.6, where 0.6 is the Z-axis collimation Acquisition mode 24 X 1.2, where 1.2 is the Z-axis collimation Number of Slices Per Tube Rotation   # of Slices Per Tube Rotation can be found: Maximum number of axial slices acquired simultaneously in one rotation N =  Maximum number of physical data channels used Other factors may need to be taken into account in order to report this number accurately Z-sharp technology allows for double the data sampling in the z-axis The system generates twice as many images as there are physical detector channels Example: 128 x 0.6 (using Z-sharp) = 128 axial slices per rotation, but N max (number of physical data channels) is 64      As a factor of the Acquisition Mode on the Routine or Scan Cards of the Examination UI    Table Increment/Speed Table Speed (Spiral) = Feed per Rotation Distance (in mm) that the table moves during one full rotation of the tube/detector Not explicitly displayed - must be calculated Table Speed = Z-axis coverage x Pitch or (N x T x Pitch) N = Detector channels in Z-axis T = Z-axis collimation Table Increment can be found: On the Scan Card of the Examination UI Example: Acquisition mode 128 X 0.6 mm, Z-sharp technology, Pitch of 1 N = 64 (because of Z-sharp) T = 0.6 mm (0.6 mm collimation) Pitch = 1 64 x 0.6 x 1 = 38.4 mm per rotation Example: Acquisition mode 24 x 1.2 mm, no Z-sharp technology, Pitch of 0.8 N = 24 (No Z-sharp) T = 1.2 mm (1.2 mm collimation) Pitch = 0.8 24 x 1.2 x 0.8 = 23.4 mm per rotation Reconstructed Scan Width (mm)                               Reconstructed Scan Width can be found: The thickness of the reconstructed image slice  Displayed and reported in mm     On the Routine, Scan, and Recon Cards of the Examination UI        Reconstructed Scan Interval (mm)   Reconstructed Scan Interval can be found: The distance between the reconstructed axial slices in the Z direction Can vary for spiral images - consecutive images that overlap Displayed and reported in mm On the Recon Card of the Examination UI      Dose Reduction Technique Used   Dose Reduction Techniques can be found: (depending on scanner and purchased options Care Dose 4D CARE kV Adaptive Dose Shield IRIS SAFIRE On the Scan and Recon Cards of the Examination UI   **In clinical practice, the use of IRIS or SAFIRE may reduce CT patient dose depending on the clinical task, patient size, anatomical location, and clinical practice. A consultation with a radiologist and a physicist should be made to determine the appropriate dose to obtain diagnostic image quality for the particular clinical task. CTDIvol/CT Dose Index Volume CTDIvol can be found: Standardized measure of radiation dose in milligray (mGy) Represents the average dose absorbed in the scanned volume of the phantom or patient of the same size Must be reported after scanning On the Patient Protocol Page AFTER scanning                              DLP/Dose Length Product DLP can be found:  Takes into consideration the scan range Is the product of the CTDIvol x Examination Range in cm Displayed and reported in mGy/cm On the Patient Protocol Page AFTER scanning   Scan Field of View (SFoV) Scan Field of View (SFoV) is not displayed on the system Area within the gantry where the data is actually used to generate images Typically smaller than the physical gantry aperture Influences the spatial resolution of the anatomy being imaged Not the same as Display or Recon Field of View Displayed and reported in cm SFoV for most body protocols is 50 cm     kVp/Kilovoltage kVp can be found: Defines the quantity of X-ray photons being used Defines the energy level or penetrating power of the X-ray beam Affects patient dose, image noise and contrast Influences CT numbers/HU in image On the Routine Card of the Examination User Interface (UI) On the Scan Card of the Examination User Interface (UI) On the Patient Protocol Page   Scan Card Routine Card mA/Milliamperage Defines the quality of X-ray photons being used Defines the actual X-ray tube current Form requires mA - NOT mAs, effective mAs, or mAs per slice mA is NOT explicitly displayed on Siemens CT scanners mA for a sequence scan = effective mAs/Rotation Time mAs and Rotation Time can be found: On the Patient Protocol Page Rotation Time displayed under T.I. column  Acquisition Slice Thickness/Z-Axis Collimation     Acquisition Slice Thickness can be found: Almost always reconstructed into other thicknessess (like 3s or 5s) Typically equal to the Collimation Slice Thickness As the latter half of the Acquisition Mode on the Routine or Scan Cards of the Examination UI On the Patient Protocol Page under the cSL column  Slice Collimation Examples Acquisition mode 64 X 0.6, where 0.6 is the Z-axis collimation Acquisition mode 24 X 1.2, where 1.2 is the Z-axis collimation Time Per Rotation (s) Rotation Time can be found: The time (in seconds) for the tube-detector system to make one complete 360 degree rotation For Sequence protocols, the Scan Time is the Rotation Time On the Patient Protocol Page under the T.I. column On the Routine and Scan cards as the Scan Time   mAs mAs can be found: X-ray tube current (mA) x Exposure time (s) For sequence CT, mAs indicates applied dose per slice mAs is calculated differently for spiral scans due to pitch  On the Patient Protocol Page            Scan Field of View (SFoV)   Scan Field of View (SFoV) is not displayed on the system Area within the gantry where the data is actually used to generate images Typically smaller than the physical gantry aperture Influences the spatial resolution of the anatomy being imaged Not the same as Display or Recon Field of View Displayed and reported in cm SFoV for most head protocols is 30 cm    Display Field of View (DFoV) DFoV can be found: The DFoV is the reconstructed Field of View of an image Determines how large or small the anatomy of interest appears Not the same as Zoom Shown in mm, reported in cm On the Recon Card - in mm - of the Examination UI    Reconstruction Algorithm/Kernel Algorithm/Kernels can be found: Mathematical formula is applied to the raw data of each image that defines the levels of sharpness and noise Allows us to reconstruct various image impressions from the same scan data Significantly different than simply changing the window and level settings Higher number = sharper image On the Recon Card of the Examination UI In the text of each reconstructed image Axial (A) = Sequence Acquisition Type can be found: Axial or Sequence scan is a step-and-shoot acquisition X-ray is turned on for imaging and off as the table moves to the next scan position Dedicated protocols for sequence scanning - e.g. HeadRoutineSeq When Feed displayed on the Scan Card of the Examination UI Sequential Acquisition Image on Routine Card  Number of Slices Per Tube Rotation # / Slices Per Tube Rotation can be found: Maximum number of axial slices acquired simultaneously in one rotation Based on number of physical data channels used in Z-axis, represented by N Example: Acquisition mode 24 X 1.2, where 24 is N Max      As the first half of the Acquisition Mode on the Routine or Scan Cards of the Examination UI    Table Increment Table Increment can be found:      The distance that the table travels in between sequential scans Sequence exams = Feed per Scan or Feed Displayed and reported in mm On the Scan Card of the Examination UI      Reconstructed Scan Width (mm) Reconstructed Scan Width can be found:    The thickness of the reconstructed image slice  Displayed and reported in mm On the Routine, Scan, and Recon Cards of the examination UI          Routine Scan Recon Reconstructed Scan Interval (mm)   Reconstructed Scan Interval can be found: The distance between axial slices in the Z-Direction Indicates if there is any overlap or any gaps between adjacent images For routine sequence scans, the distance between images - from one slice center to the next - is the same as the slice thickness itself Displayed and reported in mm On the Routine, Scan, and Recon Cards of the Examination UI as the Slice Width    Routine Scan Recon Dose Reduction Technique Used Dose Reduction Techniques Location (depending on scanner & purchased options) Care Dose 4D CARE KV IRIS SAFIRE On the Scan & Recon cards of the Examination UI   **In clinical practice, the use of IRIS or SAFIRE may reduce CT patient dose depending on the clinical task, patient size, anatomical location, and clinical practice. A consultation with a radiologist and a physicist should be made to determine the appropriate dose to obtain diagnostic image quality for the particular clinical task. CTDIvol/CT Dose Index Volume CTDIvol can be found: Standardized measure of radiation dose in milligray (mGy) Represents the average dose absorbed in the scanned volume of the phantom or patient of the same size Must be reported after scanning On the Patient Protocol Page AFTER scanning                             DLP/Dose Length Product DLP can be found:  Takes into consideration the scan range Is the product of the CTDIvol x Examination Range in cm Displayed and reported in mGy/cm On the Patient Protocol Page AFTER scanning

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  • ACR Clinical Data Form