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--- sift:gait_measures:gait_deviation_index [2024/11/06 18:00] – wikisysop
+++ sift:gait_measures:gait_deviation_index [2024/11/19 15:55] (current) – wikisysop
@@ Line 56: / Line 56: @@
-**Please note:** This is a summarized overview of the GDI calculation, and only the original paper should be referenced for recreating and interpreting the GDI (here).
+**Please note:** This is a summarized overview of the GDI calculation, and only the original paper should be referenced for recreating and interpreting the GDI [[https://www.sciencedirect.com/science/article/abs/pii/S0966636208001136|(here)]].
 ==== Derived GDI Calculation ====
@@ Line 91: / Line 91: @@
 To further understand how to get the derived GDI, we tested this ourselves using Richard Baker's spreadsheet to find the true GDI compared to our own GDI*.
-We started with a set of 4 subjects as our 'Control Group'. Here we have the average stride for each control subject, normalized to 52 points for all kinematic features. (This images shows only part of the left pelvic anterior/posterior angle signal for these subjects).
+We started with a set of 4 subjects as our 'Control Group'. We gathered the average stride for each control subject, normalized to 52 points for all kinematic features.
-{{sift:gait_measures:controlkinematics.png}}
-\\
-\\
 We then gathered and normalized 42 strides from a set of subjects to find GDI and GDI* for. We found the same kinematic features, normalized to heel strikes at 51 points.
-{{sift:gait_measures:subjectstrides.png}}
 \\
@@ Line 116: / Line 113: @@
 **NOTE: The GDI measure implemented in Sift is the derived GDI**
+=== Step 1: Joint Angle Definition ===
+The joint angles for each of the nine kinematic variables (per side) need to be calculated. These kinematic variables are the same for the GPS and GDI. If kinematic variables have not been calculated for your database, visit the following tutorial for instructions and zip files for finding the kinematic measures needed for the GPS/GDI through Visual3D pipeline commands: [[Visual3D:Tutorials:Gait_Profile_Score:Gait_Profile_Score_and_Movement_Analysis_Profile_Pipeline|Tutorial:_Gait_Profile_Score_and_Movement_Analysis_Profile_Pipeline]]
+=== Step 2: Create a Normalized Database ===
+To calculate the GDI values a reference database needs to be created. The normal database, or 'control group' as we have used throughout this page, needs to have information about each individual within the control group. Therefore, you need the mean signals over the entire normal database, and the mean signals for EACH individual that makes up that normal database. This is because the GDI* calculates the RMS difference across the ND to determine A and B for the derived GDI equation. The database should contain gait data with the same nine kinematic variables described above, which should be normalized to 51 points per gait cycle (in this tutorial, the gait cycles are defined as LHS to LHS).
+== Generate a Normal Database in Sift ==
+With Sift's [[sift:build_nds:building_normal_databases|Build ND]] feature, users can generate a reference database within the Sift application. Simply load a library of CMZ files you wish to include in the ND, query the required joint angles for the GDI measure, and generate a normal database containing mean summaries at the Library level AND workspace level for each angle. More specifics about building a ND in Sift and how to use it are found [[sift:build_nds:building_normal_databases|here]].
+=== Step 3: Dialog Selections ===
+{{ Sift:gait_measures:GDIDLG.png?500}}
+The main GDI Dialog in Sift can be accessed through the Gait Measures menu {{:sift_gait_measures.png?20}} on the main toolbar. Users should begin by selecting the sift ND file they are using. This file will be used as the reference signals when calculation the global variance scores (GVS).
+**NOTE:** The Sift ND File MUST be loaded into Sift before using it for the GDI.
+The signal type dialog selection will be deactivated here, as the GDI will always use LINK_MODEL_BASED signals from the underlying workspaces.
+The folder selection defaults to Original here, and will be used for this example. The left and right event cycles will be populated with the gait events defined in the underlying CMZ files. If this is not populated, no events were found, and those must be generated before proceeding. The literature suggests 51 normalization points for GDI signals, however, the user may change this if they wish.
+Here we have checked "compute query after calculation" which means that the GDI values will be auto queried into the explore page after running.
+We have also checked "compute individual component queries after calculation" so that groups will be queried for each GVS that makes up the total GDI score.
+\\
+We then select the signal selection button to prompt a second dialog to the GDI. It is crucial that the user make careful selections in this dialog to ensure the correct signals are being compared. Here, users will select the signal from a list of all signals in the type and folder selected in the first dialog. Each combo box is populated with data from either the CMZ library that is loaded, or the ND file.
+\\
+**Pelvic Signals** - The first three combo boxes under "Signals" are for the selection of the Pelvic angles. Here, we provide users with a list of all signals from the underlying CMZ workspaces and corresponding folders selected in the first dialog. Here we have chosen the "L_Pelvic_Angle" (left and right for this database example are actually the exact same signal), with components X, Y, and Z for the pelvic tilt, obliquity, and rotation angles. Sift will normalize this pelvic signal to left events for the left side GDI, and right events for the right side GDI. We then selected the left and right pelvis X, Y, and Z angles from the list of signals that Sift identified in the VND or Sift ND normal database. Here, the normal database has computed a L_Pelvic_Angle and R_Pelvic_Angle. Note that the Normal Database signals are assumed to be already normalized to gait events, and then averaged. So in this case, L_Pelvic_Angle was normalized to left side events, and R_Pelvic_Angle was normalized to right side events prior to loading in this Normal database file.
+\\
+** General Signals** - The rest of the "Signals" options are populated with signals that Sift has found a left and right match for in the CMZ workspaces, and gives you the "general" names. For example, Sift may find a L_Hip_Angle and R_Hip_Angle in each workspace, and the user would select "Hip_Angle" as the general option. Sift only provides users with signals where both L and R are found. Sift does not look specifically for matches in the ND files, because again, it is assumed that these signals have already been normalized to left and right gait events. Make sure you select the correct L and R signals for each entry of the dialog.
+\\
+{{:GPSSelections.png?700}}\\
+\\
+Once we return to the main dialog, the compute button is now active, and we can calculate the GDI and individual GVS measures for the active CMZ files against the normal database.
+\\
+{{Sift:gait_measures:GDIDLGActive.png}}
+\\
+=== Step 4: Calculate and View Results ===
+GDI calculations are saved as metrics in the CMZ workspaces loaded in Sift. When queried into the explore page, users may plot them as Metric or Metric-Metric plots. Here, we can see the total GDI scores generated for selected workspaces plotted as a metric bar chart. We can also look at right and left specific GDI scores from the conditions of group GDI_1.
+{{sift:gait_measures:GDIResults.png?1000}} {{sift:gait_measures:LeftvsRightGDI.png?1000}}
 ==== References ====