Sensation 16 Application Guide sw ver A60

The information presented in this application guide is for illustration only and is not intended to be relied upon by the reader for instruction as to the practice of medicine. Any health care practitioner reading this information is reminded that they must use their own learning, training and expertise in dealing with their individual patients. This material does not substitute for that duty and is not intended by Siemens Medical Solutions Inc., to be used for any purpose in that regard. The drugs and doses mentioned herein were specified to the best of our knowledge. We assume no responsibility whatsover for the correctness of this information. Variations may prove necessary for individual patients. The treating physician bears the sole responsibility for all of the parameters selected. The pertaining operating instructions must always be strictly followed when operating the SOMATOM Sensation 16. The statutory source for the technical data are the corresponding data sheets. We express our sincere gratitude to the many customers who contributed valuable input. Special thanks to the former authors and editors of this application guide, David Bradly, Martin Heuschmid*, and Bettina Klingemann for their great efforts and contribution. To improve future versions of this application guide, we would highly appreciate your questions, suggestions and comments. Please contact us: CT Application Hotline: Tel. no. +49-9191-18 80 88 Fax no. +49-9191-18 99 98 email [email protected] [email protected] Editor: Dr. Xiaoyan Chen * University Hospital, Tübingen, Germany

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Overview General

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Children

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Head

72

Neck

88

Shoulder

96

Thorax

100

Abdomen

114

Pelvis

130

Spine

136

Extremities

142

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Content General · Concept · Scan Set Up · Scan and Reconstruction – Slice Collimation and Slice Width – Pitch – Recon Job – Kernels – Image Filter · Effective mAs · Dose Information – CARE Dose – How Does It Work · Workflow – Auto Load in 3D and Postprocessing Presets · Contrast Medium IV Injection · How to Create your own Scan Protocols

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8 8 9 9 9 11 11 12 12 13 14 17 17 19 19 20 21

Content

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Head · Overview · Hints in General · AngioHead · AngioThinSlice · HeadSeq · HeadSpi · InnerEarSeq · InnerEarSpi · OrbiSinusSpi

72 72 73 74 76 78 80 82 84 86

Neck · Overview · Hints in General · AngioCarotid · NeckRoutine · ThinSliceSpi

88 88 89 90 92 94

Shoulder · Overview · Hints in General · ShoulderSpi

96 96 97 98

Thorax · Overview · Hints in General · LungLowDose · PulmonaryEmboli · ThoraxCombi · ThoraxRoutine · ThoraxHiRes · ThoraxSeqHiRes

100 100 101 102 104 106 108 110 112

General Concept The scan protocols for adult are defined according to body regions – Head, Neck, Shoulder, Thorax, Abdomen, Spine, Pelvis, Extremities. The pediatric scan protocols are defined under the folder “Children“. The protocols for special applications are defined under “Special“ (please refer to the Application Guide for Special applications). The general concept is as follows: “Fast“: uses 1.5 mm slice collimation and a higher pitch for fast acquisition for CT Angios or trauma cases. “Routine“: uses either 0.75 mm or 1.5 mm slice collimation depending on the region of interest for routine studies. “ThinSlice“: uses 0.75 mm slice collimation for thin slice studies. “HiRes“: uses 0.75 mm slice collimation and rotation time of 0.75 s for High-resolution studies. “UHR“: uses 0.75 mm or 0.6 mm slice collimation, a rotation time of 0.75 s and a scan FoV of 250 mm for ultra-high resolution studies. “Combi“: uses 0.75 mm as slice collimation and reconstruct images as both thinner slice width for HiRes or CTA and thicker slice width for soft tissue studies. “Seq“: stands for Sequence. E. g. “HeadSeq“ means the sequence mode for the head. “Spi“ stands for “Spiral“. E. g. “HeadSpi“ means the spiral mode for the head.

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General Scan Set Up Scans can be simply set up by selecting a predefined examination protocol. To repeat any mode, just click the chronicle with the right mouse button for “repeat”. To delete it, select “cut“. Each chronicle is rewriteable before “load“. Multiple ranges can be run either automatically with “auto range“, or separately with a “pause” in between.

Scan and Reconstruction Slice Collimation and Slice Width Slice collimation is the slice thickness collimated by the tube collimator, which determines the Z-coverage per rotation. In multislice CT, this is divided by the number of active detector channels (e. g. 16 x 0.75 mm). Slice width is the true thickness of the reconstructed image. With the SOMATOM Sensation 16, you select the slice collimation together with the slice width desired. The slice width is independent of pitch and algorithm, i. e. what you select is always what you get. Actually, you do not need to care about the algorithm any more; the software does it for you. On the SOMATOM Sensation 16 some slice widths are marked as “fast” (blue background). These images will be reconstructed with highest performance (up up to 6 images per second). All others will be reconstructed with up to 3 images per second. The reconstruction time depends on slice collimation and the reconstructed slice width. To get the fast performance, slice width has to be at least 3 times the slice collimation. 9

General During scanning the user normally will get “Real Time” reconstructed images in full image quality, if the “fast” slice has been selected. In some cases – this depends also on Scan range, Feed/ Rotation and Reconstruction increment – the Recon icon on the chronicle will be labeled with “RT”. This indicates the Real Time display of images during scanning. The Real Time displayed image series has to be reconstructed afterwards. The following tables show you the possibilities of image reconstruction in spiral and sequential scanning. Slice Collimation and Slice Width for Spiral Mode 0.75 mm 0.75, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 10 mm 1.5 mm 2, 3, 4, 5, 6, 7, 8, 10 mm Cardio Spiral Modes 0.75 mm 0.75, 1.0, 1.5, 2,3 mm 1.5 mm 2, 3, 4, 5 mm Slice Collimation and Slice Width for Sequence Mode 0.75 mm 0.75, 1.5, 3, 4.5, 9 mm 1.5 mm 1.5, 3, 4.5, 6, 9 mm 5 mm 5, 10 mm Perfusion Modes 1.5 mm 6, 9, 12, 18 mm ECG triggered Modes 0.75 mm 0.75, 1.5, 3 mm 1.5 mm 1.5, 3, 6 mm UHR Spiral Mode 0.6 mm 0.6, 0.75, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 10 mm 0.75 mm 0.75, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 10 mm UHR Sequence Mode 0.6 mm 0.6, 1.2 mm 0.75 mm 0.75, 1.5, 3, 4.5, 9 mm

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General Pitch In single slice CT: Pitch = table movement per rotation/slice collimation E. g.: slice collimation = 5 mm, table moves 5 mm per rotation, then pitch = 1. With the SOMATOM Sensation 16, in Siemens multislice CT, we differentiate between: Feed/Rotation, the table movement per rotation Volume Pitch, the table movement per rotation/single slice collimation E. g.: single slice collimation = 1.5 mm, table moves 24 mm per rotation, then the Volume Pitch = 16 Pitch Factor, the table movement per rotation/ collimation E. g.: slice collimation = 16 x 1.5 mm, table moves 24 mm per rotation, then the Pitch Factor = 1 With the SOMATOM Sensation 16, you do not need to select pitch. Once the scan range, scan time, slice collimation, and rotation time is defined, the software will adapt the table feed per rotation accordingly. The Pitch Factor can be freely adapted from 0.5 to 1.5. Recon Job In the Recon card, you can define up to 3 reconstruction jobs with different parameters either before or after you acquire the data. When you click on “Recon“, they will all be done automatically. In case you want to add another recon job, simply click the little icon on the chronicle with the right mouse button and select “delete recon job“ to delete the one which has been completed, and then one more recon job will be available in the Recon card. (Note: what you delete is just the job from the display, not the images that have been reconstructed). You can also reconstruct images for all scan modes completed at once – do not select any chronicle before you click “Recon“.

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General Kernels There are 5 different types of kernels: “H“ stands for Head, “B“ stands for Body, “U“ stands for Ultra High Resolution, “C“ stands for ChildHead, and “S“ stands for Special Application, e. g., Osteo CT. The image sharpness are defined by the numbers – the higher the number, the sharper the image; the lower the number, the smoother the image. Note: Do not use different kernels for other body parts than designed for. Image Filter There are 4 different filters available: PFO: To reduce beam-hardening artifacts in head images, particularly in the base of the skull, use the Posterior Fossa Optimization (PFO) filter. ASA: The Advanced Smoothing Algorithm (ASA) filter reduces noise in soft tissue while edges with high contrast are preserved. LCE: The Low-contrast enhancement (LCE) filter enhances low-contrast detectability. It reduces the image noise. HCE: The High-contrast enhancement (HCE) filter enhances high-contrast detectability. It increases the image sharpness.

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General Effective mAs In sequential scanning, the dose (Dseq) applied to the patient is the product of the tube current-time (mAs) and the CTDIw per mAs: Dseq = DCTDIw x mAs In spiral scanning, however, the applied dose (Dspiral) is influenced by the mAs (mA x Rot Time) and in addition by the Pitch Factor. For example, if a multislice CT scanner is used, the actual dose applied to the patient in spiral scanning will be decreased when the Pitch Factor is larger than 1, and increased when the Pitch Factor is smaller than 1. Therefore, the dose in spiral scanning has to be corrected by the Pitch Factor: Dspiral = (DCTDIw x mA x Rot Time)/Pitch Factor To make it easier for the users, the concept of the effective mAs was introduced with the SOMATOM Multislice scanners. The effective mAs takes into account the influence of pitch on both the image quality and dose: Effective mAs = mAs/Pitch Factor To calculate the dose on the SOMATOM Sensation 16, you simply have to multiply the CTDIw per mAs with the effective mAs of the scan: Dspiral = DCTDIw x effective mAs For spiral scan protocols, the indicated mAs is the effective mAs per image. The correlation between tube current mA and effective mAs of spiral scans on a Multislice CT scanner is given by the following formula: Effective mAs = mA x RotTime/Pitch Factor Pitch Factor = mA =

Feed/Rot nrow x Slice collimation

effective mAs x Pitch Factor RotTime

where collimated Slice refers to the collimation of one detector row, and nrow is the number of used detector rows. 13

General Dose Information The dose as described by CTDIw is displayed on the user interface for the selected scan parameters. The CTDIw is measured in the dedicated plastic phantoms – 16 cm diameter for head and 32 cm diameter for body (as defined in IEC 60601 – 2 – 44). This dose number gives a good estimate for the average dose applied in the scanned volume as long as the patient size is similar to the size of the respective dose phantoms. Since the body size can be smaller or larger than 32 cm, the CTDI value displayed can deviate from the dose in the scanned volume. The CTDIw value does not provide the entire information of the radiation risk associated with CT examination. For the purpose, the concept of the “Effective Dose“ was introduced by ICRP (International Commission on Radiation Protection). The effective dose is expressed as a weighted sum of the dose applied not only to the organs in the scanned range, but also to the rest of the body. It could be measured in whole body phantoms (Alderson phantom) or simulated with Monte Carlo techniques. The calculation of the effective dose is rather complicated and has to be done by sophisticated programs. These have to take into account the scan parameters, the system design of individual scanner, such as x-ray filtration and gantry geometry, the scan range, the organs involved in the scanned range and the organs affected by scattered radiation. For each organ, the respective dose delivered during the CT scanning has to be calculated and then multiplied by its radiation risk factor. Finally the weighted organ dose numbers are added up to get the effective dose.

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General The concept of effective dose would allow the comparison of radiation risk associated with different CT or x-ray exams, i. e. different exams associated with the same effective dose would have the same radiation risk for the patient. It also allows comparing the applied x-ray exposure to the natural background radiation, e. g. 2 – 3 mSv per year in Germany. For most of our scan protocols, we calculated the effective dose numbers for standard male* and female* and listed the result in the description of each scan protocol. The calculation was done by the commercially available program “WinDose“ (Wellhoefer Dosimetry) – as shown in figure 1 – 3. For pediatric protocols, we used the WinDose calculation and the correction factors published in “Radiation Exposure in Computed Topography“**, in which there only the conversion factors for the age of 8 weeks and 7 years old are available.

Fig. 1: User interface of the PC program WinDose. All parameters necessary for the effective dose calculation have to be specified.

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General

Fig. 2: A graphic interface of WinDose allows to specify the anatomical scan range.

Fig.3: Results as output of WinDose with the organ dose readings and the effective dose according to ICRP26 (previous version) and ICRP60 (currently valid). Please note: Effective dose values were calculated with the WinDose™ Software Version 2.1, which was optimized for SOMATOM Volume Zoom scanners. SOMATOM Sensation 16 has modified shaped filters which might cause slightly different effective dose numbers (difference not expected to be more than 5%). An update of WinDose for the SOMATOM Sensation 16 is currently developed. * The Calculation of Dose from External Photon Exposures Using Reference Human Phantoms and Monte Carlo Methods. M. Zankl et al. GSF report 30/91 ** Radiation Exposure in Computed Topography, edited by Hans Dieter Nagel, published by COCIR c/o ZVEI, Stresemannallee 19, D-60596, Frankfurt, Germany.

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General CARE Dose CARE Dose is a clinical application package that provides real-time tube current modulation for Spiral and Sequential Scanning. CARE Dose reduces patient dose significantly, especially in the regions of shoulder and pelvis. It decreases tube load, which extends the capacity for volume scanning with thinner slices, larger volumes or Multi-phase studies. It can also improve image quality by increasing mA and thus reducing image noise on the lateral views. How Does it Work It reduces the mA for low attenuation views up to 90% and keeps the nominal higher mA for high attenuation views, e. g. in the lateral projection (Fig. 4). This is done “on-the-fly”, i. e. the scanner adapts the mA in real-time, according to the patient’s attenuation profile (Fig. 5).

High attenuation, high mA

Low attenuation, low mA Fig. 4: Example of scanning in the region of shoulder.

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General

lateral a.p.

Object attenuation Modulated tube current

rel. units

1.00 0.75 0.50 0.25

time

Fig. 5: Principle of CARE Dose tube current adaptation. • CARE Dose is pre-selected by default for all standard protocols. It can be switched on/off in the scan card. • The application of CARE Dose does not require any changes in the scan parameters. The mean value of the mAs applied will be lower than what you have selected. • The mean value of the effective mAs applied is shown in the image text.

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General Workflow

Auto Load in 3D and Postprocessing Presets You can activate the “Auto load in 3D” function on the Examination Card/Auto Tasking and link it to a recon job. For example, the 2nd recon job with thinner slice width in some of the examination protocols. If the Postprocessing type is chosen from the pull down menu, the reconstructed images will be loaded automatically into the 3D Card on the Navigator with the corresponding Postprocessing type. On the 3D Card you have the possibility to create for MPR, MIPthin Range Parallel and Radial protocols which can be linked to a special series. For example, if you always do some sagittal Multiplanar Reconstructions for a Spine examination, you load once a Spine examination into the 3D Card. Select the image type (MPR, MIPthin), select the orientation and open the Range Parallel function. Adapt the range settings (Image thickness, Distance between the images etc.) and hit the link button. From now on, you have a predefined Postprocessing protocol, linked to the series description of a Spine examination. Exactly the same can be done for VRT presets. In the main menu, under Type/VRT Definition, you can link VRT presets with a series description.

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General Some of the Scan protocols, mainly for Angio examinations, are already delivered with Auto load in 3D. If you do not like, please deselect the Auto load in 3D and save your scan protocol. Some of the Scan protocols are delivered with links to a Postprocessing protocol. If you do not like our suggestions, please delete the Range Parallel preset or overwrite them with your own settings.

Contrast Medium IV Injection* The administration of a contrast medium depends on the indication and on the delay times to be used during the examination. The patients weight and circulatory situation also play a role. In general, no more than 3 ml per kg of body weight for adults and 2 ml per kg of body weight for children should be applied. As a rule of thumb, the contrast medium injection should be stopped when the scan (or acquisition) is finished. Keep this in mind, you may save contrast medium in your routine study since the multislice spiral scan can be up to 32 times faster than a 1 second, single slice spiral scan. For CTA study (arterial phase), the principle is to keep contrast injection for the whole scan. Thus, the total amount of contrast medium needed should be calculated with the following formula: CM = (start delay time + scan time) x flow rate. CARE Bolus or Test Bolus may be used for optimal contrast bolus timing. Please refer to the Application Guide for special protocols. * For more information regarding the general use of drugs and doses mentioned in this guide, please refer to page 2.

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General How to Create your own Scan Protocols User-specific scan protocols can be saved with the following basic procedure: • Register a test patient, patient position must be head-supine. • Select a scan protocol. • Set the table position to 0 (either at the gantry panel, or on the topogram routine card). • Modify the scan protocol, change parameters, add new ranges etc. • Do not load the scan protocol. • Select Edit/Save Scan Protocol in the main menu. • Select the organ region and the scan protocol name in the pop-up dialog. You can either use the same name to modify the existing scan protocol, or enter a new name. Tips – It is recommended that you save your own scan protocol with a new name in order to avoid overwriting the default scan protocol. – You may use preceding numbers (e. g. 1_Abdomen) for user specific scan protocols to make them appear on top of the list and to distinguish them from the Siemens defaults. – Do not use special characters like “/“, “.“ or ““ within scan protocol names. – Don’t rename scan protocol files on Windows NT level – this will lead to inconsistencies. – Do not mix head and body scan protocols: e. g. do not save a head mode in the abdomen directory. – System/Run offers the tool “Restore Default Scan Protocols“ which allows one to remove user specific scan protocols and to restore the Siemens default settings.

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General – System/Edit offers save/delete Scan Protocols. – System/Run also offers the tool “List Scan Protocols“ which generates an HTML table of all available scan protocols. This list can be printed or saved on Floppy (“File/Save As…“).

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