Having formerly worked as a CT Tech that included providing coverage (both Trauma and ‘routine’ CT scans) at a major Children’s Hopsital, I have done MANY CT-Heads on kiddos of your ‘type’. It is not uncommon as US has issues penetrating through cranium and showing overall ‘gross anatomy’ as a whole, succintly put, and MRI’s take a lot, LOT longer.
A good newer-model spiral scan CT unit can do a full scan in like 10-15 seconds once the two 'scout/planning/ images are done (and oth of those are quick, maybe 3-4 seconds, IME). Take a minute or two at most usually between the front/side scout images, then ‘program’ in the image-slices/angle of gantry wanted. So, two quick pics, slight wait to program in scan parameters, then when kid is at an apparent ‘relaxed’ state, the Tech presses the ‘go’ button and its over pretty quick. Lots of adjustments can be made on table speed, slice thickness for reconstructions, etc…). My gut feeling is this scan will not require a slower table-speed needed for finer detail, but a scan with thicker slices (ie faster table speed). Don’t hold me to that, but that what I usually came across in ‘screening’=like scans such as your kids seems to be. YMMV.
It was routine to plan on having child’s head placed withing a little ‘cup-like’ holder that came up around sidesw of head, and then to place foam to snug up head. Then straps were placed, gently at first to see reaction and tighter if need be. Seems cruel, but it is only for a few minutes, tops, more often than not, IME. Nothing will cause true pain to your kid.
The place I worked allowed Mom/Dad to be next to kid in kid’s field of view for comforting and distraction, and often made a HUGE difference in child’s relaxing. I would often let kiddos touch the gantry and satisfy curiousity of “is this gonna hurt me?” kinda feeling before placing them into the head-holder - slow approach seemed to help rather than rush 'em in and slap 'em in restraint, so to speak. Of course, anyone close to gantry (ie baby being scanned) would be asked to wear a lead apron and ensure that females there were not pregnant, etc, and I often suggested them to wear the glasses with lead in them for eye protection as well. A risk-v-benefit judgement overall. And chances are that kid will have a (moderately) heavy lead apron laid upon them, and hopefully underneath as well, so the weight alone helps limit squirming to some extent.
If this scan is being done at a place that routinely does children of this age, rest assured the Techs will assuredly know the tricks and appropriate means to ‘soothe’ a nervous youngster depending on age. Radiologists do seriously frown on a kiddo being radiated over and over, so methods of easing the outcome of scan is shared amongst all the Techs there.
Worst case scenario I ever had, and there were VERY few of them overall) was tight strapping and having kiddo in a ‘papoose’, a full-body wrap that prevents them from moving. Even if they scream, the cranium does not move and give artifacts from movement. This is, however, not very comonly needed, rest assured. Kids that age don’t take long to scan on a fast-scanning machine of modern design.
Hope that helps reassure you a bit, Zsofia, and best of luck at scan time. Most, by large percentage, IME, of the scans I did for similar Sx’s were normal for the most part, but better safe than sorry if the means are available, IMHO. Plus, if kiddo has a favorite toy or thing that distracts him/her, take it along to possibly gaze upon (distract attention from the obvious spinning noisy thing in that gantry) - stuff like that just might make a helpful difference during the scan. It wasn’t uncommon for the sound of the tube in gantry spinning up around kid got their attention and distracted them for duration of the scan, LOL. They can see something moving around them through the little slit where beam emerges and focus on if as it appears then reappears so quickly, I guess.