Материал: part03

C.8.17.16.1OphthalmicOpticalCoherenceTomographyB-scanVolumeAnalysisImageModuleAttribute​

Descriptions​

C.8.17.16.1.1 B-scan Cycle Time and B-scan Cycle Time Vector​

The B-scan Cycle Time (0022,1645) is the nominal scan time (in milliseconds) plus the latency between the individual repeats of the​ B-scan at the same location. The B-scan Cycle Time Vector can be used if the time for the repeats are not uniform. Either the B-scan​ Cycle Time (0022,1645) or the B-scan Cycle Time Vector (0022,1646) are required.​

B-scan Cycle Time shall be used in the following manner to calculate 'the relative time' for each B-scan:​

B-scan Cycle 'Relative Time' (n) = B-scan Cycle Delay + B-scan Cycle Time * (n-1)​

where:​

n = number of B-scan cycles within the frame and the first B-scan number is one​

Note​

When there is only one B-scan present, B-scan Cycle Time (0022,1645) may have either a value of 0, or a nominal value​ that would apply if there were multiple B-scans.​

B-scan Cycle Time Vector (0022,1646) is an array that contains the time increments (in milliseconds) between the nth B-scan cycle​ and the previous B-scan cycle for a frame. The first B-scan cycle always has a time increment of 0. The B-scan Cycle Time Vector​ shall be used in the following manner to calculate 'relative time' T(n)for B-scan Cycle n:​

- Standard -​

n

T(n) = ∑ ti i = 1

where Δti is the ith B-scan Cycle Time Vector component.​

C.8.17.16.2OphthalmicOpticalCoherenceTomographyB-scanVolumeAnalysisAcquisitionParameters​

Expected Use​

TheacquisitiontechniqueofophthalmictomographyB-scanvolumeanalysis(e.g.,OCTangiographybloodflowinformation)isbased​ on the same mechanism as used for ophthalmic tomography images. Therefore, B-scans are used for individual image frames of the​ acquired volume. The frames of the resulting volume are calculated based on a number of repeated B-scans at the same spatial​ location. So the frame of an Ophthalmic Tomography B-scan Volume Analysis SOP Instance is not a B-scan, but a data aggregation​ of B-scans from the raw data of the acquisition.​

To convey the information about the acquisition of the raw data, which are not typically in the scope of DICOM, the OCT B-scan​ Analysis Acquisition Parameters Sequence (0022,1640) is used. The parameters are provided for the user to assess the quality of​ the resulting B-scan volume analysis as well as to provide a means to compare volumes created by different devices. Furthermore​ the user is able to identify if a vendor-recommended protocol has been used to acquire the raw data.​

The OCT B-scan Analysis Acquisition Parameters Sequence contains at least one Item. It can contain more than one if multiple scan​ patterns have been used to acquire the raw data and are used to calculate the volume data.​

Number of B-scans Per Frame (0022,1642) can be used to provide an indication about the resulting image quality. In principal, the​ more B-scans averaged the better but as a high number of scans slows down the acquisition process, the resulting data becomes​ prone to noise introduced by eye movements, which are not related to blood flow. Furthermore, the number of B-scans averaged can​ be used to determine whether the acquisition was based on a vendor-specific protocol, or if the user changed the protocol.​

The B-scan Slab Thickness (0022,1643) and Distance Between B-scan Slabs (0022,1644) provide information about the density of​ the sampling pattern used to acquire the volume data. The calculation of the volume (Ophthalmic Tomography B-scan Volume Ana-​ lysis SOP Instance) is based on this information.​

C.8.17.16.3 Data Subsets​

Applications may find it useful to break up an OPT image or B-scan volume into multiple data subsets. There are two mechanisms​ in DICOM to achieve this: Concatenations and Multiple SOP Instances.​

Concatenations are not permitted in the Ophthalmic Tomography Image and Ophthalmic Optical Coherence Tomography B-scan​ Volume Analysis IODs.​

However, an OPT image or a B-scan volume can be encoded in multiple SOP instances. For example:​

1.​All frames of the volume are collected and transmitted in one multi-frame SOP instance (e.g., one SOP Instance with 30 frames).​

2.​EachframeofthevolumeistransmittedinoneSOPinstancewherethenumberofframesisequaltoone(e.g.,30SOPInstances​ with 1 frame each).​

3.​The frames in the volume are transmitted in multiple SOP Instances (e.g., 3 SOP Instances with 10 frames each).​

C.8.17.17 Ophthalmic Tomography En Face Series Module​

Table C.8.17.17-1 specifies the Attributes that identify and describe general information about the Ophthalmic Tomography En Face​ Series.​

- Standard -​

DICOM PS3.3 2020a - Information Object Definitions​ Page 1043​

Table C.8.17.17-1. Ophthalmic Tomography En Face Series Module Attributes​

Only a single Item shall be included in this Sequence.​

Required if a Performed Procedure Step SOP Class was​ involved in the creation of this Series.​

>Include Table 10-11 “SOP Instance Reference Macro Attributes”​

C.8.17.18 Ophthalmic Tomography B-scan Volume Analysis Series Module​

Table C.8.17.18-1 specifies the Attributes that identify and describe general information about the Ophthalmic Tomography B-scan​ Volume Analysis Series.​

Table C.8.17.18-1. Ophthalmic Tomography B-scan Volume Analysis Series Module Attributes​

Only a single Item shall be included in this Sequence.​

Required if a Performed Procedure Step SOP Class was​ involved in the creation of this Series.​

>Include Table 10-11 “SOP Instance Reference Macro Attributes”​

C.8.18 Stereometric Modules​

C.8.18.1 Stereometric Series Module​

Table C.8.18.1-1 specifies the Attributes that describe a Stereometric Series produced by Ophthalmic Photography equipment (OP)​ imaging Modalities.​

- Standard -​

Page 1044​ DICOM PS3.3 2020a - Information Object Definitions​

Table C.8.18.1-1. Stereometric Series Module Attributes​

C.8.18.2 Stereometric Relationship Module​

The stereometric relationship Module is used to identify pairs of images that may be viewed in stereo. It is possible that the same​ image or frame may be a member of multiple pairs. The images forming a pair shall be in different SOP Instances. The images​ forming a pair can be in different Series. All Instances referenced in this Module shall be in the same Study as the Instance in which​ the Module occurs.​

Table C.8.18.2-1. Stereometric Relationship Module Attributes​

C.8.18.2.1 Stereometric Relationship Module Attribute Descriptions​

C.8.18.2.1.1 Left and Right Image Sequences​

The images referenced by the Left Image Sequence (0022,0021) and Right Image Sequence (0022,0022) in a single Stereo Pairs​ Sequence (0022,0020) Item shall have the same values for Rows (0028,0010) and the same values for Columns (0028,0011).​

- Standard -​

The reference may be to images with a single frame, all the frames of images with multiple frames, or one or more selected frames​ within an image with multiple frames. If multiple frames are selected, the same number of frames shall be referenced from both Se-​ quences.​

C.8.19 Enhanced XA/XRF Image​

C.8.19.1 XA/XRF Series Module​

The XA/XRF X-Ray IODs use the General Series Module, specialized by the XA/XRF Series Module, to describe the DICOM Series​ Entity specified in Section A.47 and Section A.48. It is defining what constitutes a Series for the context of projection XA/XRF device.​

Table C.8.19.1-1 specifies the Attributes that identify and describe general information about the XA/XRF Series.​

Table C.8.19.1-1. XA/XRF Series Module Attributes​

Only a single Item shall be included in this Sequence.​

Required if a Performed Procedure Step SOP Class was​ involved in the creation of this Series.​

>Include Table 10-11 “SOP Instance Reference Macro Attributes”​

C.8.19.2 Enhanced XA/XRF Image Module​

ThissectiondescribestheEnhancedXA/XRFImageModule.TableC.8.19.2-1containsIODAttributesthatdescribeaXA/XRFImage​ by specializing Attributes of the General Image Module and Image Pixel Module, and adding additional Attributes.​

Table C.8.19.2-1. Enhanced XA/XRF Image Module Table​

- Standard -​