3D/4D Echo White paper - List of use cases

List of 3D/4D Echo use cases

Below is an initial list of clinical use cases for which 3D/4D Echocardiography is relevant. For each use case there will be a high level description, some basic steps, and open issues. At this point in time this is meant to be a starting point for discussions rather than detailed clinical use cases.

In the context of this whitepaper we will be focussing on interactions between the sonographer at the scanner and the reading physicin at a review workstation. The overall clinical workflow (including patient admission, ordering, scheduling, image acquisition, storage and reporting) is covered in the Echo workflow and will be most likely the same for 3D/4D Echo workflow, actually most likely it will be the same, since all studies will include 2D and 3D objects. The critical part for 3D/4D workflow is on the review of the 3D/4D datasets and the interaction with the volume data.

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Generic Echo use case

In clincial routine, there will be no specific 3D Echo use cases, a general Echo exam will consist of 2D image data as well as of volume data. Therefore the generic use case will be described here and links to use cases for specific volume workflows provided. Again, this use case will only cover the interactions between acquisition modality, evidence creator, Image Manager/Archive and Image Display. For all other actors please refer to the Echocardiography workflow.

Basic steps:

• On the scanner:
  • User claims a work item and start the corresponding exam
  • The user performs some of the following steps in the site specific order
    • optimizes settings and performs 2D acquisition of anatomy/morphology of interest using one of the following techniques:
      • B-Mode
      • B-Mode with color flow
      • M-Mode
      • CW
      • PW
      • ...
    • optimizes settings and performs a volume acquisition of anatomy/morphology of interest using one of the following techniques:
      • B-Mode
      • B-Mode with color flow
      • ...
    • performs measurements during data acquisition
    • performs volume stress echo acquisition
  • System stores images and measurements locaclly. For volume data the ECG is stored in a separate object and linked to the volume
  • User reviews acquired objects, performs additional measurements and manipulates volume data:
    • performs 3D quantification use case
    • performs visualization of valvular or congential disease use case
    • performs volume contrast echo use case
    • performs fetal stress echo use case
    • performs volume stress echo use case
  • Systems stores all additional images, derived views, measurements locally
  • User ends the exam
  • User either sends the study manually to PACS or system automatically forwards the study to the archive
• At the workplace:
  • User or system intiates retrieval of study from archive
  • User opens study and reviews images, views and measurements done by the sonographer on the scanner:
    • performs 2D review (as usual)
    • performs 3D quantification use case
    • performs visualization of valvular or congential disease use case
    • performs volume contrast echo use case
    • performs fetal stress echo use case
    • performs volume stress echo use case
  • Systems stores all additional images, derived views, measurements locally
  • User ends the exam
  • User either sends additional images/views/measurements manually to PACS or system automatically forwards the study to the archive

Open Issues

• Do all user want to permanently archive volume data, or are there scenarios in which the user only wants to keep derived views? In the latter scenario, we should think about a direct send from Modality to PACS (but what happens to storage commitment transaction then).
• Do we need to take into account a workflow for acquiring 3D and only archiving 2D derived views to PACS?

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3D Quantification of chambers

It is proven that 3D quantification of the cardiac chambers is more accurate and reproducible for multiple reasons:

• No geometric modelling is necessary
• Improved endocardial visualization

Parameters to be quantified:

• LV ejection fraction
• LV mass
• LA and RA volume
• RV volume
• Note: are there additional parameters which have not conventionally been used on 2D

Basic steps:

• On the scanner (initial review through sonographer):
  • For each chamber, the user wants to perform quantification on
    • The user opens the volume best depicitng the chamber to be analyzed
    • The system displays the volume and the associated ecg waveform time synchronized
    • The user generates view(s) appropriate to initiate the quantification algorithm and stores them
    • The user starts the quantification algorithm
    • system segments the cavity and calculates relevant parameters (TBD) and displays the results in one or multiple of the following options:
      • measurment values in the reporting/measurement package
      • MPR views, with outlines of segmented chamber
      • Rendered view of chamber with or without surrounding tissue
      • 16/17 segment model as rendered view (?)
      • anything else?
    • Optionally the user corrects segmentation results, re-initiates quantification
    • The user stores results and representative views
  • Optionally the user generates different standard views, stores them and performs standard 2D measurments on them not previously calculated.

• At the review workstation (follow up review through cardiologist)
  • For each chamber of interest, that was previously analysed:
    • The user opens the volume through one of the representative views generated previously (eg MPRs with outlines)
    • The system displays the view of the volume and the associated ecg waveform time synchronized
    • The user reviews the results of previous analysis
    • optionally the user corrects segmented conturs and re-initiates quantification
    • the user stores the updated views and quantification results
  • For each chamber of interest that was not previously analysed, the user performs the basic review steps as defined in the previous worklfow.
  • User opens volume through derived 2D views and reviews measurement results
  • Optionally the user modifies views and re-measures
  • User stores and additional views if needed.

Open issues:

• workflow must accomodate for manual, semi-automated, and automated methods to calculate chamber volumes. Depending on the method used, different requirements for derived views (and therefore presentation states) may apply (eg what is the starting point for manually tracing views or for semi-automated algorithms? Are spefic views needed, if so I assume it should be based on MPRs of standard views.)
• 3D measurements:
  • Are there additional volume measurements which do not exist currently in 2D Echo
  • Do we need to support spatial coordinates in the SR, eg should there be references between measurement values and points/regions in the image that were used in order to get the measuremnt. SCOORD currently only supports references based on x- and y- coordinates, how would segmented regions be mapped.
  • How are 3D measurements encoded (3D modifier?)

  ==> for measurements existing already the following mapping can be used:
      Image Mode: DCM 125231 3D mode 
      Echocardiography Volume Method : needs to be extended for real volume based 
      calculations methods. 

• Annotations inside of image
• Is support for the segmentation IOD needed?

Presentation State requirements:

• MPR Views (ideally with View Labeling)
• MPR views with segmented outlines overlaid or other graphical overlays.
• Calibration information in MPR views to allow 2D measurements
• Rendering of segmented chambers (color coded display of segmented structures)

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3D to support 2D:

• Slicing in any direction: Get several 2D views from the same acquisition, e.g. 9-slice. Then use those data as regular 2D images for measurements and wall-motion scoring.

==> This use case will be covered in the 3D quantification use case 

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Visualization of valvular or congential heart disease

The advantages of using 3D Echocardiography for visualizing valvular heart disease are

• quantification of the mitral anulus
• visualization of mitral leaflets, commisures and orrifice
• perpendicular en-face views enable accurate valve area measurements
• support of surgical planning
• more accurate quantification of mitral and aortic stenosis
• 3D color flow imaging combined with grayscale data for analysis of jets (origin, direction , orrifice areas, flow measurements ...)
• Visualization of complex cardiac anatomy of congenital defects
• perpendicular en face view of septal defects for determinig size

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Volume Stress Echo

• Fast volume acquistion at different stress levels, wall motion analysis based on MPRs of standard views

Basic Steps:

• At the Scanner
  • User prepares patient
  • User selects/registers the patient and start the Stress Echo exam
  • User starts image acquisition and acquires one or multiple volumes in resting stage
  • The system stores the acquired data sets locally (marked as resting stage)
  • Patient Exercises
  • User captures one or multiple volumes in post exercise stage
  • The system stores the acquired data sets locally (marked as post-exercise stage)
  • User reviews stress data sets:
    • User selects appropriate volume(s) for each stage
    • User generates standard 2D views for wall motion analysis (A4C, A3C, A2C, short axis views on various levels)
  • User ends study
  • User either sends the study manually to the archive or the system automatically forwards it

• At the workstation
  • User or system intiates retrieval of study from archive
  • User opens study
  • System displays the study for stress review (pending on user preferences either sorted by stage or by view)
  • User reviews the study, eventually corrects some of the derived views and performs wall motion analysis.
  • System stores analysis results

Issues

• Is time resolution good enough for high heart rates in stress phases?
• View label in a volume (in order to fulfill requirements for Stress Option)
• Do we need a presentation state here or are standard 2D views derived from the volume sufficient?

Presentation State Requirements:

• MPR views of standard views (A4C, A2C, A3C, Short axis views at different levels)
• View labeling of derived views
• Stage labels (or are the ones in the volume sufficient)

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Interoperative 3D Echo

Different scenarios

• Display images from previously acquired exam.
• Acquire image during intervention, e.g.:
  • Epicardial imaging to display heart anatomy (valvular apparatus) before starting heart-lung machine.
  • 3D TEE imaging for in-situ decision (size of device) and guidance of devices.
• Use of 4D in intracardiac echo, e.g. for ablation as well as for injection of stem cells, in which case one would use a 4D imaging catheter to visualize the ablation/injection catheter. It's possible that an imaging and "delivery" catheter can be combined. This is quite similar to 3D TEE in many ways as being a visualization tool (and I guess 3D TEE to some degree can be used today to do this job).

Issues:

• I need clarification on what happens to the image data after surgery. Is there still a review process on Image display or are they just archived for legal purposes?

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Volume Contrast Echo

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Fetal Volume Echo

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Fusion of different imaging modalities

Ultrasound could provide information about valves and function (others to provide coronary anatomy, scar, perfusion).

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Coronary imaging

3D may help, but more of a future feature.

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