Hi, I’m developing a DICOM files volume rendering web application using vtk.js and itk.js
I use the very handy and efficient `readImageDICOMFileSeries` function.
However, this function returns an `undefined` image when it is called multiple times, which I need to do.
Here is a jsfiddle illustrating this issue : [http://jsfiddle.net/nvmoxy6L/8/](http://jsfiddle.net/nvmoxy6L/8/)
(the console.log statements must be read in the debugger console)
Can anyone help me?
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Hi @JC_Buisson,
You may want to try the latest version of itk.js, which has improved support for repeated calls.
Note that the [arguments to `readImageDICOMFileSeries`](https://insightsoftwareconsortium.github.io/itk-js/api/browser_io.html#readImageDICOMFileSeries-fileList-singleSortedSeries-false-gt-image-webWorkerPool) changed in recent versions of itk.js. Now, you only past the file list, and optionally whether the list is known to be a single sorted series (if so, it will improve performance).
We are updating the examples to use the new API.
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It still doesn’t work with latest version 12.3.1 : [http://jsfiddle.net/0pc4nz2r/](http://jsfiddle.net/0pc4nz2r/)
It’s strange: the first call always works nice, but the second is unreliable: it succeeds or fails (it does not throw an error but returns `undefined`), with the same set of files, in circumstances I cannot explain. Yesterday the fiddle worked ok and this morning it does not, with the same files.
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> [@JC\_Buisson](#):
>
> [vtk.js - JSFiddle - Code Playground](http://jsfiddle.net/0pc4nz2r/)
@JC_Buisson thanks for creating the JS fiddle! This is very helpful for reproducibility.
I suspect that it has to do with how memory is handled in JavaScript – I will investigate.
However, you likely want to just create a copy of the `itk/Image` data structure instead of reading again regardless, since reading requires parsing all the DICOM tags, etc.
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In my application, I handle all the DICOM files hierarchy from the CDROM which is given to a patient after a CT exam, using ``. I first parse their meta-data using `dicom-parser` library, and then find the subset of files which contains the main series. But when I apply `readImageDICOMFileSeries` to this subset, it fails, apparently because of the prior use of `dicom-parser`.
After many attempts, I found out that calling the `readImageDICOMFileSeries` function twice also failed - that’s why I presented this case for easier reproducibility. But the initial use-case is common and I cannot handle it with the method you suggest.
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> [@JC\_Buisson](#):
>
> . I first parse their meta-data using `dicom-parser` library, and then find the subset of files which contains the main series.
Cool, we added a new argument recently in itk.js to improve performance for this use case – `singleSortedSeries` can be set to `true` when calling `readImageDICOMSeries` in this case.
> [vtk.js - JSFiddle - Code Playground](http://jsfiddle.net/0pc4nz2r/)
This issue here is
```auto
let { image2 } = await itk.readImageDICOMFileSeries(files)
```
The [object returned by `readImageDICOMFileSeries`](https://insightsoftwareconsortium.github.io/itk-js/api/browser_io.html#readImageDICOMFileSeries-fileList-singleSortedSeries-false-gt-image-webWorkerPool) has the property `image`. So, the syntax to return the variable in the second call as `image2` is:
```auto
let { image:image2 } = await itk.readImageDICOMFileSeries(files)
```
@agirault
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