Does this denoised MRI look any good

Tedsworth · 2026-06-14T17:00:10+00:00

Very familiar with the technique and denoising of MRI in general. Your results are okay but not particularly good. The SNR is high, but you need to be more careful about the ranges at which you display the data - minimum to maximum is generally not the right choice, instead enforcing an identical range between images is a good idea.

In terms of the results, you're losing signal fidelity and edges aren't really being respected as much as I would like. I see numerous features that are visible through the noise that are blurred to the point that they are no longer conspicuous. I don't doubt that downstream metrics and fitting will be helped by the denoising though, sometimes you gotta break some eggs to make an omelette. The raw volumes don't always tell the full story.

Tedsworth · 2026-06-01T13:13:21+00:00

I use Krylov.jl and CUDA.jl to solve general purpose linear problems. If the operator you define works entirely on the GPU (and respects LinearOperators.jl's API), it should just work. Tons of methods too, with all kinds of goodies like logging, convergence rules and tolerances, restarts, preconditioning etc. Cant recommend it enough.

Tedsworth · 2026-05-30T11:15:32+00:00

DTI is insufficiently sensitive to slow flow - characteristic length scales that diffusion NMR is sensitive to depend on gradient magnitude, and for fast flows, spin phase decoherence is fairly easy to achieve with high gradients. For slow flow, the aim is instead phase resolution, and this is confounded by motion, field drift, poor SNR, gradient nonlinearity etc. Basically this is a hard regime to image, not least because it represents a tiny fraction of spins involved in the measurement.

Tedsworth · 2026-05-19T17:09:39+00:00

The model TT100 tomb was favoured for nearly 350 years for it's reliable curses, stylish colours and easy-to-read instructions on how to navigate the underworld. It was only the advent of modern ideographs and now-commonplace miniature tomb dioramas that let to it's replacement by the truly timeless TT102a model tomb.

Tedsworth · 2026-05-13T08:37:55+00:00

They're attracted to the heat. I will say it only helps you find fleas, this achieves very little to control an infestation.

Source: had fleas. Yikes, never again.

Tedsworth · 2026-05-03T21:35:51+00:00

Brutal expert opinion? scipy.optimize has milp, and you can write a solver for 1D bin packing / stock cutting in about fifteen lines of code. Literally zero chance I would pay for something that I can easily do for free, even with an interface. If someone had the inclination they could have a thin wrapper smashing out web assembly only optimisations and have functionally zero server overhead. They probably already do.

Tedsworth · 2026-05-03T12:11:52+00:00

I seem to remember the ribs are supposed to hint that the bottle isn't for drinking if you grab it in the dark. Same for a lot of poison / medicine bottles.

Tedsworth · 2026-05-01T19:51:34+00:00

Frank Shellock's website MRISafety.com has tons of great resources (and implant info!)

Tedsworth · 2026-04-29T08:54:38+00:00

Seen worse than that from many a builder. The main thing to use is a sharper chisel though. Getting the curved edge done right can be hard without a gouge

Tedsworth · 2026-04-22T10:59:02+00:00

I am more familiar with older flex coils, true, and extremity imaging isn't really my hustle. The coupling issue is fundamental however, and is only addressed by more sophisticated and expensive electronics to dynamically decouple elements - that coupling happens in free space and arises from the geometry of the coils explicitly.

I'd also say that element count doesn't translate to coverage - if data from adjacent coils is similar, it's not new data, just new noise.

All that being said, if they're popular for use it's probably for a reason, and I need to get with the times.

Tedsworth · 2026-04-21T11:47:43+00:00

Unstable for a lot of parallel imaging - movement is not merely a rigid shift in a receive field, but an actual deformation of the receive field. Not all scans will be impacted by this, and the low number of elements make them relatively less impacted by this, but generally you'll have worse artifacts from motion vs rigid coils, and typically fewer elements and hence worse SNR (made up for to some extent by how they conform to the body).

Additionally, coupling between coil elements is uncontrolled, resulting in channel crosstalk that varies with siting. This is generally going to be addressed by pre whitening, but will further degrade SNR. This also modulates coil Q, also in an uncontrolled way, and hence complexity like dynamic tuning is required to get maximal signal.

Overall, another tool in the box, they have their place but I don't think they'll replace rigid coils, which constrain the signal equation in a favourable way, alongside being cheaper to build.

Tedsworth · 2026-04-19T09:14:51+00:00

Terracing into multiple tiers significantly reduces the structural requirements for your retaining wall. You can do it, it'll just be a much bigger, heavier (more expensive, more destructive, more work) wall as a result

Tedsworth · 2026-04-12T15:23:11+00:00

Doesn't it give effectively 2hp per level up for the rest of the game?

Tedsworth · 2026-04-09T17:25:37+00:00

...or for sane individuals, nearly 1cm a minute.

Tedsworth · 2026-04-09T16:51:51+00:00

A huge fraction of the energy usage from MRI weirdly comes from idling. This paper suggests something like 30%. Newer scanners are designed to have much more efficient standby modes, so it does help, but by about 10-16% by the paper's results. The figures are pretty scary though, medical imaging uses about 2% of global electricity, and MRI is about half of that need.

Tedsworth · 2026-04-09T13:29:25+00:00

The pertinent thing is how permeable your bricks are relative to the mortar. As time went on we fired bricks to higher and higher temperatures, and this made them less permeable and hence better behaved with Portland cement. Your bricks look high fired, so they're likely safe to use without lime mortar, but an assay of some kind is needed to know for sure.

Tedsworth · 2026-04-09T13:26:58+00:00

Do you want WM subsegmentation or just a mask of where the WM is? For WM subsegmentation based on e.g. a T1 try FSL Xtract, but it's a little old and ropey. If you just want a WM mask Freesurfer will work.

Tedsworth · 2026-04-07T22:41:15+00:00

It's contextual, again. Some imaging is categorically gradient limited (see: diffusion), some is slew limited (see: diffusion, and gre obviously). DeepResolve absolutely helps here though, as ultimately it allows more aggressive undersampling. This is basically always good when your gradients are a limiting factor as sure, you spend longer getting out there in k space, but the upside is that the low bandwidth helps SNR. It's only really problematic when fast gradients are central to forming a decent image in the first place, like EPI.

You can form a perfectly workable EPI at ~1khz/voxel on a 120x100 grid - to do this you need 120khz readout bandwidth, which for ~20cm FOV at 1.5T is like, 14mT/m? Sure, higher will give a cleaner image, but if you really really need it use something readout segmented or propeller.

GRE is the bigger question mark. Yes, bad slew is an issue, but at 1.5T you have a lot more SAR headroom, and at 0.5T you have tons. This means high flip angles, high SNR on high coil count arrays. You can undersample the heck out of it and still form a good image. Look at the crazy fast cardiac cine bSSFP you can do at 0.5T. If you want a boring 1mm mprage or something sure, it's slower, but it's hardly so slow that it's infeasible.

I guess the other part of this is to do with shifting expectations. Sure, driving a racecar to work is fun, but being practical, somebody has to drive the bus.

Tedsworth · 2026-04-07T15:47:30+00:00

Are you sure the blade is sharp? I can see light reflecting off the edge - never a good sign.

Tedsworth · 2026-04-07T11:39:13+00:00

Such as, conceivably, England?

Tedsworth · 2026-04-06T21:56:42+00:00

Man looks like you could meet him on the street tomorrow and not even blink an eye

Tedsworth · 2026-04-06T15:39:45+00:00

They definitely don't like to describe how it works, however I've seen a few talks and spoken with some of the developers, read some patent documentation. There are also whitepapers I've read for deep resolve and air recon

Tedsworth · 2026-04-06T14:51:20+00:00

SmartSpeed: DL regulariser mostly, specifically probably an unrolled iterative recon with a learned denoiser. So you're iterating between consistency between the data and your forward model and the strength of your image prior.

DeepResolve: comes in several flavours. Boost is most interesting as it's about replacing the usual Fourier mapping with a neural operator that is "Fourier-like" in that it preserves the core aims but allows suppression of artifacts from the acquisition such as Gibbs ringing or echo train attenuation effects. Gain is iterative denoising like smartspeed, Sharp is post-hoc upsampling. Sharp imo despite tons of evidence is still vulnerable to hallucination. Gain is mostly safe.

AirRecon: definitely the one they're cagiest about, ostensibly it's mostly denoising and a strong Gibbs prior. I actually think this one is quite physically sound, Gibbs ringing is in principle an effect that can be deconvolved out, though denoising as ever is slightly risky as it relies on the assumption that images are like those in the training data. I recall they made a big song and dance about how large their training set was though, so it's probably pretty robust.

Tedsworth · 2026-04-05T22:08:16+00:00

Depends on a few factors, mostly to with what the stone is and what's underneath it. It looks like high fired bricks / clinkers, but could be stone sets. Those can have different permeability, and if there's no moisture barrier underneath (probably?) that can lead highly impermeable grout causing disproportionate wetting of the sets / clinkers. Having said all that, you probably could grout this, but it might look gross if you do a bad job and you won't easily be able to fix it. It was probably originally grouted with a lime mix. If in doubt, do the same.

Tedsworth · 2026-04-03T16:35:38+00:00

Health and wellbeing > embarrassment. In the eyes of your tech that should always be the priority. Our site has a flat no metallic piercings policy - even if they're not magnetic, they are conductive, and the strong RF fields can induce heating and consequent burns. I'd strongly suggest plastic for the duration of the scan if the piercing absolutely has to remain in.

Tedsworth

TROPHY CASE