The Holland international has made just three appearances since joining from Ajax after his comeback from a serious thigh injury was delayed by a collapsed lung.
De Jong had surgery to repair that problem, and Newcastle boss John Carver this month said he was planning for the rest of the season without the forward.
But an update from the player on Wednesday raised hope he could yet be seen in a Newcastle shirt before the summer.
He tweeted:??”The last X-ray was all good! So tomorrow I will start training for??myself again. #NUFC #comebackstronger”.