Table 8.

Pitfalls

Pitfall	Explanation	Distinguishing features/ recommendations
Very infiltrative lesions (e.g. MM)	Can preserve bone marrow fat [15] (normal signal on T1WI and signal drop in out of phase)	Can be undetectable
Anaemia, rebound following chemotherapy or treatment with colony-stimulating factor (Figs. 35 and 36)	Marked haematopoiesis increases the amount of red marrow, resembling recurrent tumoral disease	Usually bilateral and symmetric -Signal intensity > than that of muscle on T1WI USPIO-enhanced MRI can differentiate these from tumour deposits (RES cells are present in the reconverted marrow but not present/substantially reduced in tumour deposits [24]
Post-chemotherapy osteosarcoma “size increase”	Sometimes even in “good responders” the primary lesion does not diminish in size or appears to enlarge	Therapy has low impact on the mineralised matrix of osteogenic sarcoma Matrix maturation/ossification (presence of fatty marrow)
Benign GCT may show elevated choline levels on proton MR spectroscopy [46]	May be related to the degree of their local aggressiveness	Use radiographs and conventional MRI for diagnosis

USPIOs: ultra-small superparamagnetic iron oxide particles

RES: reticuloendothelial system