How to anonymize a surgical video

When you decide to make surgical videos showing details of a procedure in the operating theatre, and therefore of the person being operated on, anonymisation of the person is a necessary step. This is particularly the case when it is carried out using the raw surgical videos, which are in fact part of the patient’s medical record. The GDPR to be followed when creating a surgical video are detailed here. The patient has to be informed and a consent form signed (a consent form can be found here).

This article is therefore a guide to anonymising a surgical video and presents three methods often used in this context.

Making an anonymous or de-identified surgical video

In the case of a surgical video, in practical terms, making a person unidentifiable means masking all the details of their body that could be recognised.

This means carrying out research and drawing up a list of revealing elements. As a general rule, this step should pay particular attention to :

• skin details: special moles, spots, etc.;
• facial features;
• any tattoos or piercings;
• any particular form of anatomy;
• physical signs: pimples, lesions, etc.

Nevertheless, it is sometimes impossible to make a surgical video 100% anonymous: in the case of a nasal septum operation, for example, the shape of the nose (impossible to conceal given the area operated on) could be recognisable. The patient must be warned of this.

The 3 techniques to de-identify a surgical video

There are three main methods of anonymisation: cropping, zooming within the image and blurring.

1. Cut out identifiable sequences

The first thing to do, and this is the easiest and most practical technique to apply, is to refine the derushing of the video to remove all the sensitive footage.

If the sequence is not crucial to the proper understanding of the video, it may be deleted.

2. Zoom into the image

If the recognisable elements are located at the edges of the frame and can be cropped without cutting off the area showing the surgical procedure, then the video can be cropped to hide these visual cues.

For example, if a tattoo is spotted in the bottom left-hand corner and is of no importance in the surgical procedure, the image can be cropped.

Warning: zooming means stretching the pixels. The quality of the video may be slightly degraded if this technique is used, especially if the image is not of very good quality to begin with. That’s why you should always opt for high-definition capture and files (ideally 4K, since zooming produces a 1080p or full HD image).

Find out more: Video editing glossary

3. Precise anonymisation: the treatment of blurring

If it is impossible to mask recognisable anatomical details by cutting or cropping the video, the areas concerned will have to be blurred or pixelated.

In most cases, we prefer to blur: a blurred area is often more discreet and esthetically pleasing than a raw mass of pixels.

There are several points to bear in mind when carrying out this stage:

• The blurring needs to be as close to the scene as possible, so that it does not affect the area involved in the surgery. To achieve this, you will need to use masks, which allow you to assign a geometric shape of your choice (circle, square, freehand shape, etc.) to the video effects;
• In some cases, the area to be masked will be moving. As a result, defining a fixed shape won’t be enough and you’ll need to ensure that the blurred area follows the movement. The aim will be to inform the software of the positions of the area according to the time code, in order to indicate to the system a path to follow.

Making surgical procedures anonymous is painstaking work, but essential before you can broadcast a surgical video, even if you have the patient’s consent.

For this kind of more advanced manipulation, the use of professional or semi-professional editing software with fairly advanced features is recommended (DaVinci Resolve, for example). Blurring in motion, in particular, requires a certain amount skills, but is perfectly doable for beginners with the help of tutorials.

To find out more: The best tutorials for getting to grips with DaVinci Resolve