Echo Spacing

Budget echo-center spacing from explicitly nonoverlapping readout, turnaround and settling intervals; waveform overlaps require a different timing model.

Description

An EPI echo-spacing budget adds readout time, gradient turnaround and settling.

An EPI echo-spacing budget adds readout time, gradient turnaround and settling. The remaining configured margin shows whether those sequential components fit.

The tool returns minimumEchoSpacingMs (minimum echo spacing ms); configuredMarginMs (configured margin ms); timingFits (timing fits). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.

When to use Echo Spacing

Use Echo Spacing when you already have readoutDurationMs, turnaroundGradientMs, settlingMs, configuredEchoSpacingMs and want minimumEchoSpacingMs, configuredMarginMs, timingFits. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.

How to use Echo Spacing and understand its results

Enter readoutDurationMs, turnaroundGradientMs, settlingMs, configuredEchoSpacingMs using the field table below. Match the units, ordering and data boundaries described in the calculation.
Run the tool after checking the stated bounds and matching paired observations or categories. A malformed request gives a tool error rather than a usable measurement.
Read minimumEchoSpacingMs, configuredMarginMs, timingFits. Use the calculation and interpretation below to distinguish amounts, ratios, signs and decision flags where applicable.
Review the supplied parameters and assumptions before using the result in a report or comparing it with another observation.

Input field	Meaning	Value type and bounds	Requirement
readoutDurationMs	Readout duration ms	number	Required
turnaroundGradientMs	Turnaround gradient ms	number	Required
settlingMs	Settling ms	number	Required
configuredEchoSpacingMs	Configured echo spacing ms	number	Required

Require positive readout and configured spacing with nonnegative turnaround and settling. Zero margin fits.

minimumSpacing = readout+turnaround+settling; margin = configured−minimum

The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.

json

{
  "input": {
    "readoutDurationMs": 1,
    "turnaroundGradientMs": 0.2,
    "settlingMs": 0.1,
    "configuredEchoSpacingMs": 1.5
  },
  "output": {
    "minimumEchoSpacingMs": 1.3,
    "configuredMarginMs": 0.19999999999999996,
    "timingFits": true
  }
}

Limitations and assumptions

Overlap, ramp sampling and hardware timing are not modelled. This checks the supplied component budget only.

Numerical inputs must be finite. The tool checks its declared input shape and calculation constraints; those checks do not verify the quality, calibration or representativeness of the supplied observations.

Alternative or Complementary methods

Repetition Time TR: Budget sequential nonoverlapping slice blocks plus recovery time within TR; simultaneous or interleaved waveform schedules are not inferred. Readout Time: Distinguish N full ADC dwells from the (N−1)-dwell first-to-last timestamp span; gradient ramps are not included.

Methodological background: RAD229: MRI signal and sequence lecture notes.^[1]

References

RAD229: MRI signal and sequence lecture notes — Brian Hargreaves and colleagues, Stanford University

Similar or alternative tools

Repetition Time TR
Budget sequential nonoverlapping slice blocks plus recovery time within TR; simultaneous or interleaved waveform schedules are not inferred.
Readout Time
Distinguish N full ADC dwells from the (N−1)-dwell first-to-last timestamp span; gradient ramps are not included.