<p>I have a set of 2D pictures from a CT scan.</p>

<p>How can I convert them into a 3D model for 3D printing? An example looks like this:</p>

<p><a href="https://i.stack.imgur.com/EV9Q8.jpg" rel="nofollow noreferrer" title="CT-Scan of a mouse&#39;s bones"><img src="https://i.stack.imgur.com/EV9Q8.jpg" alt="CT-Scan of a mouse&#39;s bones" title="CT-Scan of a mouse&#39;s bones"></a></p>

Using the terms "convert CT scan to 3D model," I found a number of links of tutorials. One of them is described as free, with registration and appears to be web based. The link,
Embodi3D
, appears to have a relatively comprehensive set of instructions to accomplish your goal.
Instructables
also has a similar tutorial. Should neither of these prove suitable, the search terms above may be of value.
Image below via Instructables: