There's no fresh announcement from 4DMedical Ltd (ASX: 4DX) on Friday, but someone is clearly buying the stock.
The 4DMedical share price has jumped 10.79% to $4.21 around midday, with more than 4 million shares already changing hands.
It continues what has been a pretty dramatic turnaround over the past week.
The stock touched $3.31 last Friday and has since climbed around 27%.
And today's move has caught my attention because 4DMedical remains one of the most heavily shorted stocks on the ASX.
So, what is driving buyers back into this ASX 200 healthcare stock?
Image source: Getty Images
Why are buyers coming back?
The first place I'd look is the size of the recent sell-off.
Even after today's jump, 4DMedical shares are still trading around 44% below their 52-week high of $7.55.
That's a pretty big reset for a company that has continued making progress on the commercial side.
In FY26, operating revenue rose 21% to $7.1 million, while scan volumes increased 77% to 344,075 scans.
The company also finished the year with its software available across 540 sites globally, up 39% from a year earlier.
There has been more progress in the United States as well, with CT:VQ being rolled out across major healthcare networks and imaging providers.
Could short sellers be adding fuel?
The other part of Friday's move is the very large short position sitting against the stock.
As of 11 September, around 12.4% of 4DMedical shares were reported short, making it one of the most shorted stocks on the ASX.
That means a large number of traders are still positioned for the share price to fall.
When a heavily shorted stock suddenly starts climbing, some of those traders can be forced to buy shares back to close their positions.
That extra buying can then add more momentum to the rally.
Of course, we can't know for sure that's happening today because short position data comes through with a 4-trading-day delay.
Still, with the shares up more than 20% over the past week, I wouldn't be surprised if some short covering is helping the move.
What should investors watch next?
The stock has already bounced around 27% from last Friday's low, so I wouldn't get carried away just yet.
I'd be more inclined to watch whether 4DMedical can keep building its commercial progress, especially in the United States.
Scan volumes are rising, and more sites are coming on board, but shareholders will eventually want to see that translate into stronger revenue.
Still, with the shares well below their highs, I can see why buyers are starting to come back.
