Description
Compare supplied slice-position spacing with a nominal reference; no substitution of slice thickness or clinical interpretation.
An image grid has array indices as well as physical spacing, timing, and signal conventions. A calculation on supplied metadata describes one part of that grid or signal; it does not inspect an image, validate a complete file, or interpret anatomy.
Compare supplied slice-position spacing with a nominal reference; no substitution of slice thickness or clinical interpretation.
When to use this tool
Use it for image slice spacing residual when the required inputs and conventions are already available.
How to use the tool and how it works
- Enter firstPosition, secondPosition, suppliedNominalSpacing. Use the stated units and boundary conventions.
- Run the calculation. Correct any input error before interpreting a result.
- Read signedSpacing, residual. Inspect any known, defined, inclusion, or boundary flags before interpreting numeric values.
Require nonnegative suppliedNominalSpacing. Return signedSpacing=secondPosition-firstPosition and residual=abs(signedSpacing)-suppliedNominalSpacing.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| firstPosition | First Position | Required. Finite number. |
| secondPosition | Second Position | Required. Finite number. |
| suppliedNominalSpacing | Supplied Nominal Spacing | Required. Finite number; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| signedSpacing | Signed Spacing | Required. Finite number. |
| residual | Residual | Required. Finite number. |
{
"input": {
"firstPosition": 10,
"secondPosition": 13,
"suppliedNominalSpacing": 2
},
"output": {
"signedSpacing": 3,
"residual": 1
}
}Limitations and assumptions
- Positions and nominal spacing must use a common length unit and axis. The residual uses a spacing magnitude; it does not measure slice thickness or detect nonparallel image planes.
- The field tables describe structural bounds; the mechanics also state cross-field requirements. Malformed input shapes, disallowed keys, and invalid domains cause input errors. Results must remain finite and within the declared output contract. A successful false flag or zero placeholder is distinct from an error.
- Numeric arithmetic uses binary floating point. Exact comparisons have no hidden tolerance or decimal rounding; negative zero is exported as zero. Decimal-text integer operations retain the exactness specifically stated above.
Alternative or Complementary methods
For image slice spacing residual, check the source records and the supplied rule before comparing the result with another method. Use a full image reader and geometry or signal analysis when the task requires interpreting image data.
References
Similar or alternative tools
- DICOM Image Orientation Dot Orthogonality Gap
Check supplied DICOM row/column direction cosines for unit lengths and orthogonality using an explicit tolerance.
- DICOM Pixel Spacing Row Column Crosswalk
DICOM Pixel Spacing order is row then column, in millimeters; distances are in the image plane, not patient-coordinate reconstruction.