Материал: part17

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DICOM PS3.17 2020a - Explanatory Information

Page 851

JJJJ.4 Presentation of Multi-energy Images by Legacy Display Systems

A legacy, naïve display system can receive a multi-energy (ME) image and may not recognize it as ME image, but rather display the image as a conventional CT image. This may potentially cause clinical misinterpretation, for instance, in the following scenarios:

1.For virtual mono-energetic images (VMI, images similar to those obtained with mono-energetic x-ray beam, in keV), attenuation highly depends on the beam energy (keV), so CT pixel values in VMI images can be very different from those in conventional CT images. Without proper labeling of such images, including the specific keV value used, the reviewer can come to wrong conclusions.

2.HU-based Multi-energy images where CT pixel values have been modified for specific materials (suppressed, highlighted, etc.) look similar to conventional CT images. Without proper labeling of such images, including the identification of the affected mater- ials and the way of modification, the reviewer can come to wrong conclusions.

3.In certain types of Multi-energy images (effective atomic number, electron density, material-specific image containing material concentration), CT pixel values do not represent HU values. Common ROI tools used on such an image will measure and display an average value. Since non-HU values are quite unusual in CT IOD images, there is a significant risk that a common naïve display will either omit the units of measurements (leaving user to assume the material or units), or (which is even worse) will display "HU" units instead.

4.In case of Virtual Non-Contrast images, the pixel values are modified (contrast is removed and pixel values may have been cor- rected for displacement of one material by another material). Since pixels are modified, there is a risk that the modification is in- complete or the replacement is not adequate.

JJJJ.5. Examples of Implementation

These are examples how the Attributes can be set for each image family (Section JJJJ.3 Classification of Multi-energy Images).

The structure and content of a Multi-energy CT instance also depends on the architecture of the acquisition device, e.g. multiple sources and multiple detectors vs. switching source and single detector, etc. A variety of architectures will be shown in the following examples, but an example will not be shown for every architecture.

JJJJ.5.1 Examples For Objective Image Family

JJJJ.5.1.1 Example Multiple Physical Sources and Multiple Physical Detectors

This example shows an Effective Atomic Number image acquired on an acquisition device with multiple physical sources and multiple physical detectors.

Table JJJJ.5.1.1-1. CT Image Module Attributes

Attribute Name	Tag	Values
Image Type	(0008,0008)	ORIGINAL\
		PRIMARY\
		AXIAL\
		EFF_ATOMIC_NUM
Multi-energy CT Acquisition	(0018,9361)	YES
…
Rescale Intercept	(0028,1052)	-102.4
Rescale Slope	(0028,1053)	0.1
Rescale Type	(0028,1054)	Z_EFF
…
KVP	(0018,0060)	{null value because it is described
		below}

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Page 852	DICOM PS3.17 2020a - Explanatory Information
Attribute Name		Tag		Values
…
Distance Source to Detector		(0018,1110)	1000
Distance Source to Patient		(0018,1111)	500
Exposure Time		(0018,1150)	1000
Single Collimation Width		(0018,9306)	0.6
Total Collimation Width		(0018,9307)	38,4
…
Include Table 10-27 “RT Equipment Correlation Macro Attributes Description” in PS3.3
Table JJJJ.5.1.1-2. Multi-energy CT Image Attributes
Attribute Name		Tag		Values
Multi-energy CT Acquisition Sequence		(0018,9362)
>Multi-energy Acquisition Description		(0018,937B)		Dual Source
				Dual Energy
>Include Table JJJJ.5.1.1-3 “Multi-energy CT X-Ray Source Macro Attributes”
>Include Table JJJJ.5.1.1-4 “Multi-energy CT X-Ray Detector Macro Attributes”
>Include Table JJJJ.5.1.1-5 “Multi-energy CT Path Macro Attributes”
>Include Table JJJJ.5.1.1-6 “CT Exposure Macro Attributes”
>Include Table JJJJ.5.1.1-7 “CT X-Ray Details Sequence Macro Attributes”
>Include Table JJJJ.5.1.1-8 “CT Acquisition Details Macro Attributes”
>Include Table JJJJ.5.1.1-9 “CT Geometry Macro Attributes”
Multi-energy CT Processing Sequence		(0018,9363)
>Include Table JJJJ.5.1.1-10 “Multi-energy CT Processing Attributes”
Table JJJJ.5.1.1-3. Multi-energy CT X-Ray Source Macro Attributes
Attribute Name		Tag		Values
Multi-energy CT X-Ray Source Sequence		(0018,9365)
ITEM 1
>X-Ray Source Index		(0018,9366)	1
>X-Ray Source ID		(0018,9367)	Tube A
>Multi-energy Source Technique		(0018,9368)	CONSTANT_SOURCE
>Source Start DateTime		(0018,9369)	2018.05.01 13:22:03
>Source End DateTime		(0018,936A)	2018.05.01 13:22:20
>Generator Power		(0018,1170)	100
ITEM 2
>X-Ray Source Index		(0018,9366)	2
>X-Ray Source ID		(0018,9367)	Tube B
>Multi-energy Source Technique		(0018,9368)	CONSTANT_SOURCE
>Source Start DateTime		(0018,9369)	2018.05.01 13:22:03
>Source End DateTime		(0018,936A)	2018.05.01 13:22:20
>Generator Power		(0018,1170)	100

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DICOM PS3.17 2020a - Explanatory Information		Page 853
Table JJJJ.5.1.1-4. Multi-energy CT X-Ray Detector Macro Attributes
Attribute Name	Tag	Values
Multi-energy CT X-Ray Detector Sequence	(0018,936F)
ITEM 1
>X-Ray Detector Index	(0018,9370)	1
>X-Ray Detector ID	(0018,9371)	Detector A
>Multi-energy Detector Type	(0018,9372)	INTEGRATING
>X-Ray Detector Label	(0018,9373)	High-Energy
>Nominal Max Energy	(0018,9374)	150
>Nominal Min Energy	(0018,9375)	35
>Effective Bin Energy	(0018,936E)	90
ITEM 2
>X-Ray Detector Index	(0018,9370)	2
>X-Ray Detector ID	(0018,9371)	Detector B
>Multi-energy Detector Type	(0018,9372)	INTEGRATING
>X-Ray Detector Label	(0018,9373)	Low-Energy
>Nominal Max Energy	(0018,9374)	100
>Nominal Min Energy	(0018,9375)	35
>Effective Bin Energy	(0018,936E)	60

Table JJJJ.5.1.1-5. Multi-energy CT Path Macro Attributes

Attribute Name	Tag	Values
Multi-energy CT Path Sequence	(0018,9379)
ITEM 1
>Multi-energy CT Path Index	(0018,937A)	1
>X-Ray Source Index	(0018,9366)	1
>X-Ray Detector Index	(0018,9370)	1
ITEM 2
>Multi-energy CT Path Index	(0018,937A)	2
>X-Ray Source Index	(0018,9366)	2
>X-Ray Detector Index	(0018,9370)	2

Table JJJJ.5.1.1-6. CT Exposure Macro Attributes

Attribute Name	Tag	Values
CT Exposure Sequence	(0018,9321)
ITEM 1
>Referenced X-Ray Source Index	(0018,9377)	1
>Exposure Time in ms	(0018,9328)	1000
>X-Ray Tube Current in mA	(0018,9330)	500
>Exposure in mAs	(0018,9332)	500
>Exposure Modulation Type	(0018,9323)	CD4D
>CTDIvol	(0018,9345)	5

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Page 854	DICOM PS3.17 2020a - Explanatory Information
Attribute Name	Tag	Values
ITEM 2
>Referenced X-Ray Source Index	(0018,9377)	2
>Exposure Time in ms	(0018,9328)	1000
>X-Ray Tube Current in mA	(0018,9330)	250
>Exposure in mAs	(0018,9332)	250
>Exposure Modulation Type	(0018,9323)	CD4D
>CTDIvol	(0018,9345)	5

Table JJJJ.5.1.1-7. CT X-Ray Details Sequence Macro Attributes

Attribute Name	Tag	Values
CT X-Ray Details Sequence	(0018,9325)
ITEM 1
>Referenced Path Index	(0018,9378)	1
>KVP	(0018,0060)	150
>Focal Spot(s)	(0018,1190)	1.2
>Filter Type	(0018,1160)	WEDGE2
>Filter Material	(0018,7050)	MIXED
ITEM 2
>Referenced Path Index	(0018,9378)	2
>KVP	(0018,0060)	100
>Focal Spot(s)	(0018,1190)	1.2
>Filter Type	(0018,1160)	WEDGE2+FLAT
>Filter Material	(0018,7050)	TIN

Table JJJJ.5.1.1-8. CT Acquisition Details Macro Attributes

Attribute Name	Tag	Values
CT Acquisition Details Sequence	(0018,9304)
ITEM 1
>Referenced Path Index	(0018,9378)	1
>Rotation Direction	(0018,1140)	CW
>Revolution Time	(0018,9305)	0.5
>Single Collimation Width	(0018,9306)	0.6
>Total Collimation Width	(0018,9307)	38.4
>Table Height	(0018,1130)	88.5
>Gantry/Detector Tilt	(0018,1120)	0
>Data Collection Diameter	(0018,0090)	500
ITEM 2
>Referenced Path Index	(0018,9378)	2
>Rotation Direction	(0018,1140)	CW
>Revolution Time	(0018,9305)	0.5
>Single Collimation Width	(0018,9306)	0.6

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DICOM PS3.17 2020a - Explanatory Information		Page 855
Attribute Name	Tag	Values
>Total Collimation Width	(0018,9307)	38.4
>Table Height	(0018,1130)	88.5
>Gantry/Detector Tilt	(0018,1120)	0
>Data Collection Diameter	(0018,0090)	350
Table JJJJ.5.1.1-9. CT Geometry Macro Attributes
Attribute Name	Tag	Values
CT Geometry Sequence	(0018,9312)
ITEM 1
>Referenced Path Index	(0018,9378)	1\2
>Distance Source to Detector	(0018,1110)	1000
>Distance Source to Data Collection Center	(0018,9335)	500

Table JJJJ.5.1.1-10. Multi-energy CT Processing Attributes

Attribute Name	Tag	Values
Decomposition Method	(0018,937E)	HYBRID
Decomposition Description	(0018,937F)	iBHC + MAT DECOMP

JJJJ.5.1.2 Example Single Source Multi-layerdetector

This example shows a type Effective Atomic Number image acquired on an acquisition device with a single source and multi-layer detector.

Table JJJJ.5.1.2-1. CT Image Module Attributes

Attribute Name	Tag	Values
Image Type	(0008,0008)	ORIGINAL\PRIMARY\AXIAL\EFF_ATOMIC_NUM
Multi-energy CT Acquisition	(0018,9361)	YES
…
Rescale Intercept	(0028,1052)	0
Rescale Slope	(0028,1053)	1.3
Rescale Type	(0028,1054)	10^-2 Z_EFF
…
KVP	(0018,0060)	{null value because it is described below}
…
Scan Options	(0018,0022)	AXIAL
Data Collection Diameter	(0018,0090)	500
…
Distance Source to Detector	(0018,1110)	1040
Distance Source to Patient	(0018,1111)	570
Exposure Time	(0018,1150)	750
X-Ray Tube Current	(0018,1151)	440
Exposure	(0018,1152)	330
Single Collimation Width	(0018,9306)	0.625

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Источник: https://studfile.net/preview/14585770/

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