fix: Only check spatial pixdims for PET

Author: effigies

src/schema/rules/checks/nifti.yaml

@@ -17,7 +17,7 @@ NiftiUnit:
   issue:
     code: NIFTI_UNIT
     message: |
-      NIfTI file's header field for unit information for x, y, z, and t dimensions is empty or too short.
+      NIfTI file's header field for unit information for x, y, z, and t dimensions is underspecified.
     level: warning
   selectors:
     - type(nifti_header) != "null"
@@ -30,13 +30,26 @@ NiftiPixdim:
   issue:
     code: NIFTI_PIXDIM
     message: |
-      NIfTI file's header field for pixel dimension information is empty or too short.
+      NIfTI file indicates 0-sized voxels.
     level: warning
   selectors:
+    - suffix != 'pet'
     - type(nifti_header) != "null"
   checks:
     - min(nifti_header.voxel_sizes) > 0
 
+NiftiPixdimPET:
+  issue:
+    code: NIFTI_PIXDIM_PET
+    message: |
+      NIfTI file indicates 0-sized voxels along spatial axes.
+    level: warning
+  selectors:
+    - suffix == 'pet'
+    - type(nifti_header) != "null"
+  checks:
+    - min([nifti_header.pixdim[1], nifti_header.pixdim[2], nifti_header.pixdim[3]]) > 0
+
 # 60
 XformCodes0:
   issue: