Giant cell tumor (GCT) of the tendon sheath is a localized form of pigmented villonodular synovitis (PVNS) and can cause certain imaging findings. Which imaging modality is useful for detecting GCT of the tendon sheath, and what type of MRI signal characteristic is typically seen in these lesions?

A) Ultrasound; Hypointensity on T2-weighted images
B) CT scan; Calcifications within the lesion
C) MRI; Blooming on gradient-echo sequences
D) X-ray; Blurred margins of the lesion