Based in Switzerland Advancing clinical neuroscience
CLINICAL RECIPE / 03

Mapping a hostile flow field

From geometry to haemodynamic hypothesis

Prof. Daniel A. Rüfenacht Peer education series
Mixed-media neuroradiology artwork for Mapping a hostile flow field
ARTWORK 03 / FLOW
FLOW / CFD
THE CLINICAL QUESTION

Is the model explaining an observation—or manufacturing certainty?

MISE EN PLACE

Six ingredients,
one interpretation.

01Patient-specific geometry
02Inlet assumptions
03Mesh quality
04Velocity field
05Wall shear descriptors
06Sensitivity analysis
THE METHOD

Four movements.

01

Reconstruct

Create a geometry that preserves clinically relevant vessel relationships.

02

Declare

Make boundary conditions and modelling assumptions visible.

03

Explore

Examine patterns rather than searching for one decisive colour map.

04

Validate

Test whether the hypothesis remains stable across plausible inputs.

Detail of the recipe artwork
THE SECRET INGREDIENT

Assumptions.

Every flow field rests on choices about geometry, boundaries and numerical method. The most persuasive visualisation is not necessarily the most robust model.

MODEL / FLOW / SENSITIVITY
INTERPRETIVE TENSIONS

Hold both sides
in view.

Expert synthesis is rarely a choice between simple opposites. The work is to understand how each tension changes confidence.

01GeometryBoundary conditions
02PatternMagnitude
03PlausibilityValidation
04Visual impactReproducibility
HOW TO SERVE

Make the reasoning visible.

Show the model together with its assumptions and sensitivity. Use haemodynamics to sharpen a hypothesis, not to conceal uncertainty behind colour.

A beautiful flow field should still survive an uncomfortable question.Clinical Recipes / Editorial reflection
THE CLINICAL DOSSIER

Three deeper
readings.

GEOMETRY → ASSUMPTION → SENSITIVITY

I
GEOMETRY

Begin with the vessel, not the colour map

Segmentation is already an interpretation. Neck definition, small branches and smoothing decisions alter the domain in which the calculation will live. Before reading velocity or shear, inspect what anatomy the reconstruction kept—and what it quietly removed.

II
BOUNDARIES

Expose the invisible inputs

Inlet profiles, outlet conditions, rheology and wall behaviour are not decorative methodology. They determine what the model is able to say. A clinically useful display lets a colleague see those assumptions beside the result.

III
SENSITIVITY

Look for a hypothesis that survives

Repeat the calculation across plausible inputs. Stable spatial tendencies may help organise a biological question; fragile magnitudes should lower confidence. The endpoint is not computational certainty, but a more disciplined next question.

AT THE READING TABLE

Questions for
colleagues.

  1. 01

    Which geometric decision most influences the pattern?

  2. 02

    Does the observation persist across plausible boundary conditions?

  3. 03

    What independent measurement could challenge the model?

A model earns clinical attention by revealing its limits as clearly as its patterns.
KEEP IN VIEW

Computational haemodynamics is model-dependent and should be interpreted with imaging, biology and clinical context.