Table 3.

Common postoperative complications and their respective imaging modalities.

Complication	MRI Findings	Role of advanced Imaging	Pitfalls and precautions
Hematoma/Seroma	Signal intensity varies with age of hematoma	Gradient-echo imaging shows areas of blooming in the region of hematoma. These areas will not show any post contrast enhancement.	When haemorrhage occurs within the tumour it may not be possible to differentiate.
	Seroma is well defined, Homogeneous area with T1 hypointense and T2 hyperintense with low-intensity rim caused by deposition of hemosiderin	DWI: ADC is significantly higher compared to recurrent tumour	Recurrent myxomas are T2 hyperintense- show post contrast enhancement and mimic seroma
Post-surgical hypertrophic scar/Pseudotumor	Can be bulky mass- like progressively enlarging, irregular shape	DWI: Increased ADC values	Early inflammatory pseudotumors with granulation tissue might show T2 hyper intensity and enhancement pattern mimicking tumour
	T1: Hypointense	DCE: Almost never shows arterial phase enhancement
	T2: Hypointense
	Little/no post contrast enhancement
Pseudo-progression	Post radiation/post chemotherapy	The residual tumour will show persistent enhancement and diffusion restriction. The pseudo-progression will show blooming in gradient sequences with non-enhancement and no diffusion restriction.	Avoid imaging for 4–6weeks following therapy to allow differentiation form recurrence.
	Heterogeneous signal intensity
	Enlargement of central non-enhancing component with reduced solid enhancing areas
Post radiation reactive changes in soft tissue, flaps and bone	Soft tissue: Diffuse edema with preserved architecture (“muscle texture sign or feathering sign” on T1 weighted images) limited to the radiation field is seen within the muscles and the flap.	DWI: Low signal on DWI and high signal on ADC	Follow up imaging muscle atrophy with fat overgrowth. The overall flap size will decrease.
	Radiation osteitis: T2/STIR hyperintense areas in the marrow	DCE: Delayed enhancement	New mass or bone destruction within radiation field,
	Radiation osteonecrosis: New heterogeneous area within irradiated area		Heterogenous signal intensity lesion with matrix calcification can be sarcoma and should not be mistaken for osteonecrosis.
	T1 hyperintense
	T2 intermediate signal intensity
Tumour recurrence Bone/soft tissue	Focal progressively enlarging mass with heterogeneous signal intensity	Shows Post contrast enhancement with increase diffusion restriction and decreased ADC values.	Certain Densely ossified tumors and fibrous tumors may remain T2 hypointese.
	Replacement of normal muscle texture	Diffusion quantification also known as tumor ADC histograms represent the distribution of ADC values within the tumor. Malignant tumor components generally show ADC values less than 1.0 x 10-3 mm2/s	No optimal cut off value between different vendors for ADC parameters.
	T1 hypointensity	DCE: Early arterial phase enhancement with washout or plateau in highly vascular recurrent tumor as seen in time intensity curves.	Time consuming for routine clinical use and may not be available in all centers
	T2 hyperintensity
	Similar in signal intensity to primary tumor

DCE – Dynamic contrast enhancement; DWI – Diffusion weighted image.