Table 1. A summary of the key terms used to describe the pathological processes in osteomyelitis and their MRI signal characteristics.

Key term	Pathological process	MRI signal
		T1	T2	T1 + C
Bone marrow oedema	Accumulation of pus within the medullary cavity, leading to vascular congestion	Low	High	High
Intraosseous abscess	Formation of reactive bone and granulation tissue around intramedullary pus	Low	High	Peripheral enhancement
Subperiosteal abscess	Accumulation of pus beneath elevated periosteum	Low	High	Peripheral enhancement
Cloaca	A cortical defect that allows pus to drain between bone and soft tissue	Low	High	Low
Sinus tract	A channel, lined with granulation tissue, that allows pus to drain between bone and the skin surface	Low	High	Peripheral enhancement
Sequestrum	A separated fragment of necrotic bone that is surrounded by pus, granulation tissue and an involucrum	Low	Low	Peripheral enhancement

MRI, magnetic resonance imaging.