Hi Xue,
As always you provide the most amazing cases and high quality images for us to enjoy and consider,
I am perplexed by this appearance and will consult my brains trust to see if there is any consensus.
I suspect this will remain a mystery for a while,
It is a very mysterious appearance,
If you have any other imaging or clinical follow up that would be most welcome,
Please examine some MRI volumes to see if costal cartilage is always solid cartilage or if there is occasional liquid islands within the cartilage.
I think you have the mystery case of the year so far Xue,
I always love your work and attention to detail,
Please keep it coming and share your amazing cases through this forum,
Happy scanning,
Steve