diff --git a/src/modality-specific-files/magnetic-resonance-imaging-data.md b/src/modality-specific-files/magnetic-resonance-imaging-data.md
index 5e4528aca5..ce58b6446a 100644
--- a/src/modality-specific-files/magnetic-resonance-imaging-data.md
+++ b/src/modality-specific-files/magnetic-resonance-imaging-data.md
@@ -721,37 +721,46 @@ within the `[*_]dwi.bval` and `[*_]dwi.bvec` files) MAY change across DWI runs.
**Gradient orientation file formats**.
The `[*_]dwi.bval` and `[*_]dwi.bvec` files MUST follow the
-[FSL format](https://fsl.fmrib.ox.ac.uk/fsl/docs/#/diffusion/index?id=diffusion-data-in-fsl):
-The `[*_]dwi.bvec` file contains 3 rows with *N* space-delimited floating-point numbers
-(corresponding to the *N* volumes in the corresponding NIfTI file.)
-The first row contains the *x* elements, the second row contains the *y* elements and
-the third row contains the *z* elements of a unit vector in the direction of the applied
-diffusion gradient, where the *i*-th elements in each row correspond together to
-the *i*-th volume, with `[0,0,0]` for *non-diffusion-weighted* (also called *b*=0 or *low-b*)
-volumes.
-Following the FSL format for the `[*_]dwi.bvec` specification, the coordinate system of
-the *b* vectors MUST be defined with respect to the coordinate system defined by
-the header of the corresponding `_dwi` NIfTI file and not the scanner's device
-coordinate system (see [Coordinate systems](../appendices/coordinate-systems.md)).
-The most relevant limitation imposed by this choice is that the gradient information cannot
-be directly stored in this format if the scanner generates *b*-vectors in *scanner coordinates*.
-
-Example of `[*_]dwi.bvec` file, with *N*=6, with two *b*=0 volumes in the beginning:
-
-```Text
-0 0 0.021828 -0.015425 -0.70918 -0.2465
-0 0 0.80242 0.22098 -0.00063106 0.1043
-0 0 -0.59636 0.97516 -0.70503 -0.96351
-```
-
-The `[*_]dwi.bval` file contains the *b*-values (in s/mm2) corresponding to the
-volumes in the relevant NIfTI file), with 0 designating *b*=0 volumes, space-delimited.
-
-Example of `[*_]dwi.bval` file, corresponding to the previous `[*_]dwi.bvec` example:
-
-```Text
-0 0 2000 2000 1000 1000
-```
+[FSL format](https://fsl.fmrib.ox.ac.uk/fsl/docs/#/diffusion/index?id=diffusion-data-in-fsl).
+
+The `[*_]dwi.bvec` file contains 3 rows with *N* space-delimited floating-point numbers,
+corresponding to the *N* volumes in the corresponding NIfTI file.
+Across these three rows,
+each column encodes three elements of a 3-vector for the corresponding image volume;
+each vector MUST be either of unit norm,
+or optionally the vector `[0.0,0.0,0.0]`
+for *non-diffusion-weighted* (also called *b*=0 or *low-b*) volumes.
+These values are to be interpreted as cosine values with respect to the image axis orientations
+as defined by the corresponding NIfTI image header transformation;
+*unless* the image axes defined in the corresponding NIfTI image header
+form a right-handed coordinate system
+(that is, the 3x3 matrix of direction cosines has a positive determinant),
+in which case the sign of the first element of each 3-vector must be inverted
+for this interpretation to be valid.
+Note that this definition of orientations with respect to the NIfTI image axes
+is *not* equivalent to the DICOM convention,
+where orientations are instead defined with respect to the scanner device's coordinate system
+(see [Coordinate systems](../appendices/coordinate-systems.md)).
+
+The `[*_]dwi.bval` file contains the *b*-values (in s/mm2)
+corresponding to the volumes in the relevant NIfTI file,
+with 0 designating *b*=0 volumes; space-delimited.
+
+Examples of `[*_]dwi.bvec` and `[*_]dwi.bval` files,
+corresponding to a NIfTI image with 6 volumes
+with the first two volumes having no diffusion sensitization:
+
+- `[*_]dwi.bvec`:
+ ```Text
+ 0 0 0.021828 -0.015425 -0.70918 -0.2465
+ 0 0 0.80242 0.22098 -0.00063106 0.1043
+ 0 0 -0.59636 0.97516 -0.70503 -0.96351
+ ```
+
+- `[_]dwi.bval`:
+ ```Text
+ 0 0 2000 2000 1000 1000
+ ```
### Multipart (split) DWI schemes
diff --git a/src/schema/objects/extensions.yaml b/src/schema/objects/extensions.yaml
index db38cf55b2..d482f8849d 100644
--- a/src/schema/objects/extensions.yaml
+++ b/src/schema/objects/extensions.yaml
@@ -30,21 +30,26 @@ bvec:
description: |
A space-delimited file containing gradient directions (b-vectors) of diffusion measurement.
- This file contains 3 rows with *N* space-delimited floating-point numbers,
+ The `bvec` file contains 3 rows with *N* space-delimited floating-point numbers,
corresponding to the *N* volumes in the corresponding NIfTI file.
- The first row contains the *x* elements, the second row contains the *y* elements and
- the third row contains the *z* elements of a unit vector in the direction of the applied
- diffusion gradient, where the *i*-th elements in each row correspond together to
- the *i*-th volume, with `[0,0,0]` for *non-diffusion-weighted* (also called *b*=0 or *low-b*)
- volumes.
+ Across these three rows,
+ each column encodes three elements of a 3-vector for the corresponding image volume;
+ each vector MUST be either of unit norm,
+ or optionally the vector `[0.0,0.0,0.0]`
+ for *non-diffusion-weighted* (also called *b*=0 or *low-b*) volumes.
+ These values are to be interpreted as cosine values with respect to the image axis orientations
+ as defined by the corresponding NIfTI image header transformation;
+ *unless* the image axes defined in the corresponding NIfTI image header
+ form a right-handed coordinate system
+ (that is, the 3x3 matrix of direction cosines has a positive determinant),
+ in which case the sign of the first element of each 3-vector must be inverted
+ for this interpretation to be valid.
- Following the FSL format for the `bvec` specification, the coordinate system of
- the *b* vectors MUST be defined with respect to the coordinate system defined by
- the header of the corresponding `_dwi` NIfTI file and not the scanner's device
- coordinate system (see [Coordinate systems](SPEC_ROOT/appendices/coordinate-systems.md)).
- The most relevant limitation imposed by this choice is that the gradient information cannot
- be directly stored in this format if the scanner generates *b*-vectors in *scanner coordinates*.
+ Note that this definition of orientations with respect to the NIfTI image axes
+ is *not* equivalent to the DICOM convention,
+ where orientations are instead defined with respect to the scanner device's coordinate system
+ (see [Coordinate systems](SPEC_ROOT/appendices/coordinate-systems.md)).
chn:
value: .chn
display_name: KRISS CHN