| DICOM PS3.3 2024e - Information Object Definitions |
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Table C.8.25.14-1 defines the Attributes used to encode axial measurements of the eye made by an axial measurements device. This is typically done for both eyes, but may be for just one.
Table C.8.25.14-1. Ophthalmic Axial Measurements Module Attributes
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Describes the type of ophthalmic axial measurement acquisition device. |
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The method used for obtaining axial measurements of the eye. Only a single Item shall be included in this Sequence. Required if Ophthalmic Axial Measurements Device Type (0022,1009) is ULTRASOUND. |
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The definition of anterior chamber depth for this instrument. |
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Axial measurements of a patient's right eye. |
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>Include Table C.8.25.14-2 “Ophthalmic Axial Measurements Macro Attributes” |
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>Include Table C.8.25.14-5 “Ophthalmic Axial Measurements Selected Macro Attributes” |
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Axial measurements of a patient's left eye. |
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>Include Table C.8.25.14-2 “Ophthalmic Axial Measurements Macro Attributes” |
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>Include Table C.8.25.14-5 “Ophthalmic Axial Measurements Selected Macro Attributes” |
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Table C.8.25.14-2 specifies the Attributes of the Ophthalmic Axial Measurements Macro.
Table C.8.25.14-2. Ophthalmic Axial Measurements Macro Attributes
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Lens status of the eye. See Section C.8.25.14.1.1.1 for further explanation. |
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Status of the vitreous cavity. See Section C.8.25.14.1.1.2 for further explanation. |
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A free form text description of Vitreous Status (0022,1025). |
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Whether or not the patient's pupils were pharmacologically dilated for this acquisition |
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Information about the agent administered. |
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>>Include Table 8.8-1 “Code Sequence Macro Attributes”. |
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Units of measure for the Mydriatic Agent Concentration. Only a single Item shall be included in this Sequence. Required if Mydriatic Agent Concentration (0022,004E) is present. |
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Identifies whether measuring the total axial length of the patient's eye or a segment of the eye for which a discrete measurement was obtained. |
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The axial length of a patient's eye, in mm. One or more Items shall be included in this Sequence. Required if Ophthalmic Axial Length Measurements Type (0022,1010) is TOTAL LENGTH. See Section C.8.25.14.1.1.4 for further explanation. |
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The axial length measurement acquired, in mm. The type of measurement is specified in the Ophthalmic Axial Length Measurements Type (0022,1010). See Section C.8.25.14.1.1.3 and Section C.8.25.14.1.1.4 for further explanation. |
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Whether or not the clinician intervened to modify the output of the device. For example by forcing it to select a different peak in the display. |
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>>Referenced Ophthalmic Axial Length Measurement QC Image Sequence |
Reference to the quality control image associated with this measurement. Only a single Item shall be included in this Sequence. See Section C.8.25.14.1.1.6 for further explanation. |
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>>>Include Table C.8.25.16-6 “Ophthalmic Axial Measurements Quality Image SOP Instance Reference Macro Attributes” |
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>>Include Table C.8.25.14-4 “Ophthalmic Axial Measurements Related Information Macro Attributes” |
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>Ophthalmic Axial Length Measurements Length Summation Sequence |
Axial length of a patient's eye, in mm, when it is calculated by summation of multiple segmental axial length measurements. One or more Items shall be included in this Sequence. Required if Ophthalmic Axial Length Measurements Type (0022,1010) is LENGTH SUMMATION. See Section C.8.25.14.1.1.4 for further explanation. |
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The axial length measurement acquired, in mm. The type of measurement is specified in the Ophthalmic Axial Length Measurements Type (0022,1010). See Section C.8.25.14.1.1.3 and Section C.8.25.14.1.1.4 for further explanation. |
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Whether or not the clinician intervened to modify the output of the device. For example by forcing it to select a different peak in the display. |
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>>Referenced Ophthalmic Axial Length Measurement QC Image Sequence |
Reference to the quality control image associated with this measurement. Only a single Item shall be included in this Sequence. See Section C.8.25.14.1.1.6 for further explanation. |
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>>>Include Table C.8.25.16-6 “Ophthalmic Axial Measurements Quality Image SOP Instance Reference Macro Attributes” |
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>>Ophthalmic Axial Length Measurements Segmental Length Sequence |
Segmental axial length measurements of a patient's eye that contribute to an aggregate axial length measurement. One or more Items shall be included in this Sequence. See Section C.8.25.14.1.1.4 for further explanation. |
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>>>Include Table C.8.25.14-3 “Ophthalmic Axial Length Segmental Measurements Macro Attributes” |
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>Ophthalmic Axial Length Measurements Segmental Length Sequence |
Segmental axial length measurement of a patient's eye. One or more Items shall be included in this Sequence. Required if Ophthalmic Axial Length Measurements Type (0022,1010) is SEGMENTAL LENGTH. See Section C.8.25.14.1.1.4 for further explanation. |
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>>Include Table C.8.25.14-3 “Ophthalmic Axial Length Segmental Measurements Macro Attributes” |
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Lens Status Code Sequence (0022,1024) refers to either the natural lens of the eye (phakic), or various types of lens implants inserted in cataract surgery, or lack of a lens in the eye (aphakic).
Vitreous Status Code Sequence (0022,1025) refers to either the natural status of the vitreous cavity (vitreous only) or to various possible states after vitreous surgery.
If Ophthalmic Axial Measurements Device Type (0022,1009) is ULTRASOUND, the Ophthalmic Axial Length (0022,1019) measurement is taken from the anterior vertex of the cornea to the anterior surface of the retina (internal limiting membrane).
If Ophthalmic Axial Measurements Device Type (0022,1009) is OPTICAL, the Ophthalmic Axial Length (0022,1019) measurement is taken from the anterior vertex of the cornea to the level of the photoreceptors in the retina and compensated to adjust for the thickness of the retina to mimic the ultrasound technique.
This difference is an inherent property of the measurement method. Since optical devices measure to retinal pigment epithelium and ultrasound devices measure to internal limiting membrane, the difference must be subtracted to obtain comparable results for use in intraocular lens calculation formulas. The difference is the thickness of the retina, which has been determined empirically and varies with the axial length of the eye.
When the acquisition device type is ultrasound, the Ophthalmic Axial Length (0022,1019) may represent distance calculated using a single time value and an average presumed velocity for the entire eye. Alternatively it may represent the sum of multiple segmental axial length measurements with each distance value calculated using a different time value and a presumed velocity specific to that segment of the eye.
When the acquisition device type is optical, the whole length can be measured instead of measuring and summing up different segments of the eye. Nevertheless, optical axial measurement devices can also measure segments of the eye independently (e.g., the Anterior Chamber depth).
Each segment of the eye that is measured shall be identified by the Ophthalmic Axial Length Measurements Segment Name Code Sequence (0022,1101).
For Attribute Observer Type (0040,A084), Ultrasound axial length measurement devices take many measurements in rapid sequence. The machine can be set to select a good quality measurement automatically, or it can be set so that the user presses a footswitch when he/she sees a quality measurement based on the graphical display.
The Attribute Referenced Ophthalmic Axial Length Measurement QC Image Sequence (0022,1330) references a quality control image that is a secondary capture of the presentation of a one dimensional waveform produced when performing ophthalmic axial measurements. It is acquired by the modality creating the ophthalmic axial measurements. The purpose of these images is to judge the quality of an axial length measurement for use in calculating the power of intraocular lens to place in a patient's eye in cataract surgery. The image is used for quality control and not for diagnostic purposes. See PS3.17.
The SOP Instance for the quality control image will meet the following requirements:
Frame Increment Pointer (0028,0009) is set to 00182002 = sequencing by Frame Label Vector (0018,2002).
The Attribute Referenced Instance Sequence (0008,114A) is conveyed and only a single Item is used. The Item in Referenced Instance Sequence (0008,114A) contains the value "1.2.840.10008.5.1.4.1.1.78.7" = (this SOP Class) for Attribute Referenced SOP Class UID (0008,1150) and Attribute Referenced SOP Instance UID (0008,1155) will reference this measurement SOP Instance.
Burned In Annotation (0028,0301) is set to NO.
The Attribute Burned In Annotation (0028,0301) defines whether patient demographics have been burned into the image. This Attribute does not prohibit non-demographic burned in annotation, such as position of gates, for image or waveform annotations that are very important to a user. Such annotations are expected to be conveyed and displayed.
| DICOM PS3.3 2024e - Information Object Definitions |
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