Client side anonymization help

[Asim]

I'm trying to perform some client side anonymization with DICOM parser but require user input for a field like PatientName for anonymization. I understand this can be problematic in the case that the provided values exceed the previous length of the field. How should i handle this scenario? The anonymization example says it would require "resizing the Uint8Array and updating the length". How should I be doing this?

[Chris Hafey]

The output of dicomParser is the offset of the data portion of each attribute in the data set.  If you change the length of the data during anonymization, you need to resize the buffer and move bytes around to fit.  For example, if the parsed data length is 10 bytes and you de-identify it to a 16 byte value, you need to allocate a buffer 6 bytes bigger than the original one and copy the old data up to the de-identified attribute over, then the new deidentified data element and then the remaining data after that.  I haven't actually done this before myself, but I think it should work!

On Thu, Feb 25, 2021 at 4:06 PM Asim <asimdot...@gmail.com> wrote:

I'm trying to perform some client side anonymization with DICOM parser but require user input for a field like PatientName for anonymization. I understand this can be problematic in the case that the provided values exceed the previous length of the field. How should i handle this scenario? The anonymization example says it would require "resizing the Uint8Array and updating the length". How should I be doing this?

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[Salim Kanoun]

Hi,

When I will have more time, I wanted to try this way using dcmjs

https://github.com/dcmjs-org/dcmjs/issues/141

If you land with a solution that you could share I would be interested

Salim

[Todd Jensen]

I've used the following for character type elements (keeps element length the same):

var element = dataSet.elements[tag];

var deIdentifiedValue = "SomeTextHere";

for(var i=0; i < element.length; i++) {

  var char = (deIdentifiedValue.length > i) ? deIdentifiedValue.charCodeAt(i) : '0';

  dataSet.byteArray[element.dataOffset + i] = char;

}

Todd Jensen, PhD

Jensen Informatics LLC

[Salim Kanoun]

hi,

I have some feedback about dcmjs,

my first implementation seems to work properly on the early tests, I confirm that client side edition is easier with dcmjs as you can add / edit / delete dicom Tag without having to care about low level issue such as byte allocation.

Here is my code in developpement :

See https://github.com/salimkanoun/GaelO_Uploader/blob/edition/src/model/DicomFile.js

Best regards,

Salim

[Asim]

Hey Salim,

Thank you for the snippet! I've translated it for my use case and it seems to be working well here

Cheers,

Asim