Various request, questions and concerns have reached us over time. This page constitutes an attempt to collect the answers to make them readily available to all participants.
Time-since-stroke (TSS), Time-to-treatment (TTT) and the TICI score. Do not use the mRS, as this constitutes as the clinical outcome measure the target of task II and hence won't be provided with the testing set.
No. The mRS is the target of task II and hence won't be provided with the testing set.
For each patient, a 90-day follow-up scan was acquired, which is assumed to show the final lesion extend. In this sequence one (training set) respectively two (testing set) experienced raters delineated the final lesion extend.
The anatomical follow up scan was non-rigidly registered to the acute ADC sequence and the expert segmentation transformed accordingly with nearest-neighbor interpolation.
Experiences raters created the expert segmentation. Although each registration was visually rated, some errors might be introduced by 1. the registration to the acute ADC sequence, 2. the interpolation and 3. the partially substantial changes to the brain's anatomy. Please keep in mind that the final lesion cannot be assumed to fit the acute diffusion lesion nor the acute perfusion lesion.
Yes, but we would welcome if you note the fact in your results.
Please feel free to ignore the "Lyse type" column in the table. It should not be in there and constitutes a mishap by one of our data contributors.
Our data contributors failed to recover the TTT values for these cases. We decided for leave them in for all teams not using the clinical parameters at all. If you choose to employ this clinical parameter in your method you can either (a) remove these three cases from the training set or (b) artificially assume the average TTT over all other cases to be a sufficient approximation of the missing values. In the test data, all cases will be provided with TSS, TICI and TTT values.
Medical Image Computing is rather similar to the classical Computer Vision, but differs in some concrete points such as this.
For the physician, the presence and location of the acute lesion is rather obvious and all current stroke treatment protocols involve a visual check of the MRI data. What he doesn't know, is how the stroke outcome is likely to be under different conditions (which treatment, which stroke, etc.) but nevertheless he has to a potentially fatal decision as fast as possible.
Now, the already necrotic tissue (the ischemic stroke core) and the underperfused but-yet-alive tissue (the penumbra) are assumed to be quantifiable (albeit not easily) in the acute image.
We go a step further and follow a theory that presumes that, given clinical parameters such as the stroke age (TSS) and the treatment success (TICI score), the final lesion and probably even clinical outcome can be predicted.
Here, computer vision meets the medical approach: Pure learning methods, such as CNN, might well be able to give good predictions (and I personally think they will). But a good model of stroke evolution, constructed with a sound background knowledge of the physical processes involved, might equally win.
Feel free to treat the challenge as a pure computer vision problem. It would be very interesting to see, what these method can achieve.
There is a difference between outcome (be it lesion or clinical) under UNTREATED conditions and outcome under certain TREATMENT conditions. The untreated lesion outcome is assumed to coincide with the perfusion lesion (penumbra and core together) and can presumably be deduced directly from the acute PWI scans. This was, e.g., the task of last years ISLES 2015 - SPES challenge. The good results obtained by many methods show that this is indeed possible.
But the treating physician is not interested in the untreated outcome, but rather in the potential benefit of treating the stroke (e.g. by thrombolysis or thrombectomy). Important is that these treatments are by no means risk-free (they can easily lead to haemorrhages and subsequently death or worse clinical outcome) and should only ever be performed when the potential benefit outweighs the risks. Furthermore, there are not always successful (see wide range of TICI scores).
So what if the physician could, after acquiring the acute scans and assessing the TSS, quickly check when the next operation room might be made available (TTT) and compare the outcomes under successful (TICI=3) against unsuccessful (TICI=0) re-canalization to get a quantitative measure of the potential gain? This would allow him to make a performed treatment decision, possibly widening the treatment time window, raise the stroke treatment success and maybe even decrease mortality and disability rates.
Well, that is the vision, at least. At the time of assessment, the physician has TSS, can assume TTT and wants to compare different TICI scores. The mRS should, as detailed in response to your previous question, not be used.