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syngo FLC Exposure Index

This job aid covers the Exposure Index on the syngo FLC software.

syngo FLC: Exposure Index FLUOROSPOT Compact (syngo FLC) To avoid systematic errors, like under or overexposure, the imaging system provides the exposure index as an initial indication for the applied dose. The exposure index is only intended to be a coarse indicator of the dose applied to the receptor for a particular examination. The magnitude of this unitless value depends on many factors. It is therefore a relative value under certain acquisition conditions. Definitions and abbreviations There are several definitions for the exposure index. The values from two definitions are calculated by the imaging system: • The Physical EXI is a measure of the mean gray value in the middle area of the image. • The Clinical EXI analyzes the mean gray value of the diagnostic relevant part in the image via histogram, without the peaks for direct radiation and collimation. • The Deviation Index detects the tolerance of the exposure in correlation of the Clinical EXI value. The Deviation Index tells something about under- and overexposure of the diagnostic area. The exposure index is an important indicator for the exposure of the acquisitions. The exposure index, Physical EXI and/or Clinical EXI, is derived from the image data and is displayed on the bottom-left of the image. Please note: Pay attention to the exposure index in all examinations. EXI = Physical EXI The Physical EXI or EXI is determined as an average of the image signal of a centered region in the image (Definition according to German standard DIN 68 68 Part 58). The current collimation is considered. SIEMENS Unrestricted Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2021 Master Template Effective Date: 5 MAR 2020 | HOOD05162003074494 Healthineers Job Aid Effective Date: 06 I 24 I 2021 | HOOD05162003197804 Job Aid | syngo FLC Exposure Index Effective Date: 06 I 24 I 2021 | HOOD05162003197804 Please note that in system versions prior to VB10 and in older Siemen’s systems, e.g., Aristos, the Physical EXI has been indicated as EXI. The Physical EXI can be useful when a user is accustomed to older Siemen’s systems. The Physical EXI is also the better choice for constancy tests. Clinical EXI = EI The Clinical EXI or EI is determined according to IEC 62494-1 (2009-08) as the “value of Interest” of the image. The calculation considers the relevant area of the image and eliminates non relevant areas like directly radiated areas or non-collimated areas. The Clinical EXI may be more useful in clinical practice because it considers the image content. In contrary to the Physical EXI, the Clinical EXI is normalized to calibration conditions, i.e., it is widely independent from systematic influences, e.g., from the used flat detector. For this purpose, a normalization factor can be entered in service configuration. Typical values: Under calibration conditions, the Clinical EXI is related to the dose as follows: Sensitivity Dose setting Clinical EXI* 800 1.25 125 400 2.5 250 200 5 500 * theoretical value under calibration conditions according to IEC 62494-1 SIEMENS Unrestricted Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2021 Healthineers Master Template Effective Date: 5 MAR 2020 | HOOD05162003074494 Job Aid Effective Date: 06 I 24 I 2021 | HOOD05162003197804 Job Aid | syngo FLC Exposure Index Effective Date: 06 I 24 I 2021 | HOOD05162003197804 Linear relations Within defined conditions, the Physical EXI as well as the Clinical EXI are directly proportional to the applied dose (linear relation), i.e., a double in the exposure index corresponds to twice the dose. If the same organ program is selected under similar acquisition conditions and the same positioning of the patient has been maintained, the exposure index must be within a certain range. Example: Thorax series examination With identical positioning, e.g., central p.a., and exposure parameters, the exposure index value must only fluctuate within certain limits. Please note, that the reference value for the exposure index depends on the examination type and the organ examined. The exposure index values differ also with different projections/views. Dependencies The exposure index depends on the following factors: • selected organ program • organ examined • projection • collimation • position of the organ examined • e.g., metal implants, pacemakers, inside the considered area • position of the AEC dominant Please note: If the area in question is exposed to direct radiation during the acquisition, e.g., incorrect positioning with respect to the collimation, the Physical EXI is meaningless. In exposures with two organs in one acquisition, e.g., two hands, the Physical EXI is also meaningless. Large deviations If the exposure index deviates greatly from the usual values, this might be due to incorrect positioning, incorrect setting, or in extreme cases, a defect in the system. Please note: If the exposure index deviates greatly from the usual values during a standard examination and other causes for the deviation have been eliminated: Perform the constancy test. If this test reveals deviations from previous measurement results: Call Siemens Service to have the system inspected. If no deviations are found, the observed deviation was probably due to the dependencies described above. SIEMENS Unrestricted Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2021 Healthineers Master Template Effective Date: 5 MAR 2020 | HOOD05162003074494 Job Aid Effective Date: 06 I 24 I 2021 | HOOD05162003197804 Job Aid | syngo FLC Exposure Index Effective Date: 06 I 24 I 2021 | HOOD05162003197804 Deviation Index = DI The Deviation Index or DI is a gauge for the deviation of the Clinical EXI of an image from the target value scaled in exposure points. The Deviation Index is calculated after image acquisition by the following formula: • DI = 10·log10 (EI/EIT) EI is the clinical exposure index of the actual exposure. EIT is the target clinical exposure index (Target EXI) for the examination, which is defined in the organ program (in the EXI Values parameter set). Please note: In software versions before VE10, the Deviation Index was defined as follows: • DI = 10·log₁₀ [Clinical EXI / (Max. EXI + Min. EXI) / 2] Max. EXI and Min. EXI are defined in the organ program (in the EXI Values parameter set). Max. EXI, Min. EXI, Target EXI As a guidance, maximum and minimum clinical EXI values as well as a target clinical EXI value can be defined in every organ program via selection of a parameter subset. Please note: Make sure to assign the correct EXI Values parameter subset suitable for the organ program. When importing organ programs from system versions prior to VB10, for every Imported organ program, a suitable EXI Values parameter subset must be assigned! SIEMENS Unrestricted Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2021 Healthineers Master Template Effective Date: 5 MAR 2020 | HOOD05162003074494 Job Aid Effective Date: 06 I 24 I 2021 | HOOD05162003197804 Job Aid | syngo FLC Exposure Index Effective Date: 06 I 24 I 2021 | HOOD05162003197804 Display When configured, the exposure index value of the acquired image is displayed in the lower left- hand corner on the monitor. kV: 69.8 mAs: 0.6 SC: 400 Physical EXI 885 Clinical EXI 408 0_CRST_Wall 1 0.51 uGym2 Example: It can be configured in the User Settings either the Physical EXI, the Clinical EXI, the Deviation Index, or any combination of them, or none is displayed on the monitor image. If configured, the exposure index is also displayed on the film sheet. The configured exposure index value is also included in the exam protocol. Please note: The EXI value in the exam protocol is recorded directly after acquisition. It will not be changed when reprocessing images. DICOM header The exposure index values, Physical EXI, Clinical EXI, and Deviation Index are stored as private tags and as (new) public tags in the DICOM header of an image. For details, see the DICOM Conformance Statement. In the User Settings, you can configure for one of the tags to be assigned as the (old) public tag in the DICOM header. The exposure index values are therefore included in image transfers. Clinical EXI control For monitoring purposes, the imaging system logs all the Deviation Index, Clinical EXI, and Physical EXI values as well as other exposure data in the Clinical EXI Log. These data can also be exported to USB memory and used for statistical evaluations. SIEMENS Unrestricted Published by Siemens Healthcare GmbH © Siemens Healthcare GmbH, 2021 Healthineers Master Template Effective Date: 5 MAR 2020 | HOOD05162003074494 Job Aid Effective Date: 06 I 24 I 2021 | HOOD05162003197804 Job Aid | syngo FLC Exposure Index Effective Date: 06 I 24 I 2021 | HOOD05162003197804 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, for relevant safety information like warnings and cautions. 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