What is in devices/, what the numbers mean, and which to reach for. Set both
in a scenario's catheter block:
"catheter": { "device": "bentson_035", "tip_shape": "angled" }Flexural rigidity EI in N·mm², the single number that decides how a device behaves here. All the guidewires are 0.035" (0.889 mm); the catheter is 5F.
| id | shaft | tip | µ | source | use |
|---|---|---|---|---|---|
bentson_035 |
40 | 8 | 0.08 | estimate | Floppiest thing in the box. What you lead with into anything tortuous, and the safest wire to learn on. |
hydrophilic_angled_035 |
86 | 10 | 0.037 | estimate | Nitinol core, slippery, steerable tip. The tortuosity- and stenosis-crosser. Low friction cuts both ways — it slides beautifully and it gets away from you. |
amplatz_plain_035 |
291 | 61 | 0.08 | measured | General-purpose workhorse. Enough body to support a catheter, too stiff to explore with. |
rosen_j_035 |
350 | 61 | 0.08 | estimate | Mid-range exchange wire with a fixed J. The step between exploring and committing. |
diagnostic_catheter_5f |
675 | 30 | 0.25 | measured | 5F catheter, 1.67 mm across. Soft tip on a braided shaft. Note µ is 3× a coated wire — it drags. |
amplatz_super_stiff_035 |
1849 | 92 | 0.08 | measured | Exchange wire. Straightens what it is put into rather than following it. |
lunderquist_035 |
4857 | 92 | 0.08 | measured | Stiffest available. A rail, not a navigation tool. |
estimate means estimate. Those four are positioned against the Harrison
2011 guidewire family that the measured ones come from, but their moduli are
not read off that table — they are shaped to sit in the right places relative
to each other. Their source field says so in capitals, and a test asserts they
keep saying so. Replace them with real values when the table is to hand.
Everything above is 0.035" peripheral kit. Neuro work is a different scale, and the difference is section, not material — a 0.014" wire is the same nitinol, six times thinner.
| id | OD | shaft | tip | µ | use |
|---|---|---|---|---|---|
microwire_014_soft |
0.36 mm | 47 | 2 | 0.037 | The exploring microwire. Shapeable 30 mm tip. What you lead with everywhere intracranial. |
microwire_014_support |
0.36 mm | 57 | 6 | 0.08 | Short soft tip on a near-solid shaft. For tracking a microcatheter, not for finding your way. |
microcatheter_027 |
0.90 mm | 60 | 6 | 0.037 | 2.7F braided microcatheter. Stated as EI directly — a braid-reinforced composite has no meaningful solid-section modulus. |
guide_catheter_6f |
2.00 mm | 900 | 180 | 0.08 | Holds the arch and takes the reaction while smaller devices work through it. |
The whole class is bounded by arithmetic: a 0.014" round section has
I = 7.85e-4 mm⁴, so even solid austenitic nitinol at 75 GPa cannot exceed
59 N·mm². A test asserts both microwires stay under it. Everything here is a
SHAPED ESTIMATE — the Harrison table is a 0.035" family and does not reach this
scale, so these are shaped from section geometry and material limits instead.
Settled peak wall load, measured (scratch/bench_neuro.py). Expert peak is
0.54 N, novice 1.75 N, and a healthy wall perforates at 3.8 N.
| device | ICA siphon | M1 stenosis | Type III arch |
|---|---|---|---|
microwire_014_soft |
0.28 | 0.18 | 0.05 |
microwire_014_support |
0.98 | 3.83 ✗ | 0.14 |
hydrophilic_angled_035 |
1.30 | 4.33 ✗ | 0.35 |
bentson_035 |
1.09 | 5.64 ✗ | 0.38 |
amplatz_plain_035 |
9.37 ✗ | 40.1 ✗ | 1.37 |
Read the M1 column. Every 0.035" wire perforates it, because a 0.445 mm wire has no business in a 0.42 mm stenosis — that is clinical truth showing up as arithmetic, not a defect. And an Amplatz tears the siphon at 9.4 N while a microwire rests in it at 0.28 N: you do not lead into a siphon with a peripheral wire.
Neuro technique is coaxial almost throughout — a wire leads, a catheter follows. Declare it in the scenario:
"catheter": { "device": "microwire_014_soft", "outer_device": "microcatheter_027", "outer_lag": 0.03 }outer_lag is how much bare wire leads the catheter's tip. Over the length they
overlap the two are forced to the same curvature, so their stiffnesses add;
beyond the catheter tip you are steering the bare wire. That is the whole reason
the technique works, and why tracking the catheter forward for support and
pulling it back for a soft leading tip are different manoeuvres.
Limit. Coaxial assemblies are exact on straight and gently curved anatomy (0.000 N and zero kinked joints on a straight 1.85 mm lumen; 0.575 N settled for a 5F over a 0.035" in the arch, inside the Rafii-Tari band). Driving one through tight curvature coils it — the siphon reaches 1600–2500 N where the bare wire reads 0.66 N. That is the geometric-stiffness term
rod.pydefers: without it the rod has no compression instability, so where a real assembly would prolapse back out of the vessel this one has nowhere to put the axial load and knots instead. Pair coaxially in vessels large and gentle enough to take it. The arch is; the siphon is not.
straight · angled · j_tip · pigtail
A pre-shaped tip is an intrinsic rest curvature in the last few joints. Q/E
deflection adds to it, so a shaped tip at full deflection is more curled than
either alone.
| tip | total curl at full deflection | min radius it needs | what it is for |
|---|---|---|---|
straight |
88° | 5.4 mm | No pre-shape. Deflection only. |
angled |
132° | 3.6 mm | Presents a direction. The one you can aim into a branch ostium. |
j_tip |
268° | 1.8 mm | Presents a loop. Atraumatic — it rides past side branches rather than digging in, which is the point and also why it is poor at selection. |
pigtail |
448° | 1.1 mm | Full curl. An angiographic catheter tip for sitting in a chamber and injecting, not something to lead a wire with. |
The lumen must be wider than the curl the controls can command, or the tip wedges against the wall instead of turning, and deflection reads as scraping.
Counterintuitively the straight tip is the worst case at 5.4 mm, because its deflection spreads over four joints with no pre-shape concentrating it. Measured twice the hard way: an angled wire in a 2.5 mm lumen perforated at 7 N in a straight run-in before reaching any obstacle, and the sandbox at 3 mm produced 2.9 N in a vessel containing nothing, purely from working the controls.
tests/test_driving_test.py checks each shipped scenario's nominal lumen against
its own tip. A deliberate narrowing is allowed to be tighter — the driving test's
1 mm stenosis is tight precisely so a deflected tip cannot barge through it.
Wall load is linear in EI. Measured: a Lunderquist reads 11.3× an Amplatz for a 16.7× stiffness ratio. So halving stiffness halves the force a given bend costs you, and that is the whole reason the soft wires exist — before they were added, nothing was below 291 N·mm² and no realistic tortuosity stayed inside the literature force band.
Settled wall load, sinusoidal vessel, 3 mm lumen — total N, worst single node in brackets:
| radius of curvature | Amplatz 291 | 5F cath 675 | Lunderquist 4857 |
|---|---|---|---|
| 11 mm | 38.5 (9.4) | 57.8 (20.3) | 435.8 (156.7) |
| 46 mm | 14.9 (6.3) | 17.6 (10.1) | 199.1 (105.1) |
| 91 mm | 4.4 (1.5) | 13.1 (9.8) | 51.7 (25.4) |
| 182 mm | 0.0 | 0.0 | 0.0 |
Healthy arterial wall perforates near 3.8 N at a single point; diseased intima at 0.15–0.45 N. Expert operators peak around 0.54 N, novices 1.75 N.
The zeros in the last row are correct, not a bug: once the vessel's deviation drops below the device's clearance, a straight wire fits without bending and exerts nothing.
- Start soft. Lead with the floppiest wire that will track. A Bentson gets
further into the driving test than anything else in the box — though at time
of writing it still perforates at the selection turn, which is a fault in
that course rather than in the wire. See
docs/HANDOFF.mdsection 3e. - Match the tip to the lumen using the table above before blaming the controls.
- Exchange up when you need support, not before — that is what the Amplatz and Lunderquist are for, and neither will navigate tortuosity for you.
- Watch friction, not just stiffness. The hydrophilic wire is 0.037 against the catheter's 0.25. Slippery is easier to advance and harder to place.
Drop a JSON file in devices/; the filename stem is the id. Stiffness may be
given as a flexural modulus E_pa on a solid circular section (how guidewires
are reported) or as EI_n_mm2 directly (how catheters are). Both normalise to
N·m². cathsim.device validates the result against a published envelope per
class and rejects anything outside it.
Set confidence honestly. measured and estimate are the difference between
a number someone can defend and a number someone made up, and this whole model
rests on being able to tell which is which.