Table 4.

Technical characteristics of the imaging techniques used, diagnostic criteria and histopathological validation per study

Reference	Imaging method	Equipment, contrast medium or radionucleotide and setting conditions	Tumour localization (number)	Imaging invasion criteria	Histopathological invasion criteria	Histopathological protocol	Comments
Handschel et al30	CT	Somatom Sensation 6 (Siemens Healthcare, Munich, Germany). Lohexol 300 mg ml−1. Collimation of 6 × 1 mm at 110 kVp and 100 mAs. Axial slice thickness up to 2007: 3 mm. From 2007 to 2010: 1.5 mm. Bone window: 1400/400 HU. Soft-tissue window: 350/50 HU	Mandible (58), floor of the mouth (43) and tongue (6)	Three-point scale according to the degree of cortical bone erosion Invasion: compromise of periosteum and bone	Three-point classification according to the degree of penetration in cortical bone	n.i.
Gu et al29	CT	MX8000 Infinite Detector Technology, Omnipaque 300 (Philips, Eindhoven, Netherlands), 100 ml. Collimation of 41.5 mm at 120 kVp and 200 mAs. Slice thickness: 3 mm. Axial and coronal reconstruction of 3 mm in a matrix 512 × 512	Tonsils (23)	Interruption or erosion of the peripheral hyperattenuating rim adjacent to a mass of abnormal soft tissue or when the medullary bone is replaced by a hyperattenuating lesion. Four-point scale according to the presence or absence of invasion Invasion: probably present and definitely present	No distinction is made between cortical or medullary invasion. Both are considered positive for invasion	n.i.
	MRI	Gyroscan Intera 1.5 T. Omniscan (Philips), 0.1 mmol kg−1. Axial, sagittal and coronal slices. FOV: 200–300 mm. Slice thickness: 6 mm. Matrix 256 × 256	Retromolar trigone (8)	Replacement of the hypointense peripheral signal by a signal intensity of the tumour on T1 and T2 or replacement of the hyperintense signal by an intermediate tumour signal
	PET/CT	Discovery STE whole-body PET/CT system (General Electric Medical Systems, Milwaukee, WI). 18F-FDG 370–555 MBq (10–15 mCi). Detector configuration: 8 × 1.25 mm. Tube voltage: 120 kVp and 200 mAs. Slice thickness: 3.75 mm. Reconstruction in the axial and coronal planes with a slice thickness of 6.5–7.8 mm	Base of the tongue (6)	Dark areas correspond to regions with high FDG absorption adjacent to the cortical bone that shows a visible defect in CT or FDG accumulation in the cortical bone and within the medullary bone in the same region, even without detectable cortical erosion
	CT + MRI		Floor of the mouth (5)	Combined score: score of 4 for more than one imaging test or a combined score of >2
	CT + PET/CT		Buccal space (3)	As above
	MR + PET/CT		Gingiva (1)	As above
	CT + MRI + PET/CT			As above
Hendrikx et al28	Cone beam CT Classic i-CAT		Retromolar trigone (8)	Four-point scale according to bone compromise. Positive: slight invasion, clear invasion	Erosion: bone replacement without invasion towards the medullary space, mandibular canal or periodontal ligament space. Mandibular invasion: diffuse growth of the tumour within the medullary bone, root canal and, if present, the periodontal ligament space	Decalcification with 10% formic acid. Slice thickness: 5 μm
	Digital panoramic	Planmeca Promax (Planmeca, Helsinki, Finland)	Floor of the mouth (9)	As above
	MRI	1.5 T Siemens Vision whole-body (Siemens Healthcare). Gadopentetate dimeglumine 0.2 ml kg−1. Slice thickness: 3 mm	Inferior alveolar flange (6)	As above
Van Cann et al26	CT	Somatom 3. Iohexol, 150 ml, 350 mg I ml−1. Slice thickness: 1.5 mm. Configuration: soft and hard tissue	Retromolar trigone (20), floor of the mouth (31), inferior alveolar flange (13) and mucous membrane (3)	Absence of cortical bone adjacent to a mass of abnormal soft tissue	(a) Cortical invasion: bone replacement without invasion into the medullary space, mandibular canal or periodontal ligament space (b) Medullary invasion: diffuse growth of the tumour within the medullary bone, root canal and, if present, the periodontal ligament space	Decalcification with 10% formic acid. Slice thickness: 5 μm	Includes diagnostic algorithms for different strategies of imaging method sequences
	MRI	1.5 T Siemens Vision whole body. Gadopentetate dimeglumine 0.2 ml kg–1. Slice thickness: 3 mm		Replacement of the hypointense peripheral signal by a signal intensity of the tumour on T1 and T2 or replacement of the hyperintense signal by an intermediate signal from the tumour
	Panoramic	Planmeca Promax		n.i.
	Single photon emission CT	99mTc-methylene-diphosphonate 600 MBq. Dual head gamma camera. Photo peak: 140 keV. Window: 15%. Matrix: 128 × 128		n.i.
van den Brekel et al27	MRI	0.6 T or 1.5 T Siemens systems (Siemens Healthcare). Gadolinium in 24 patients. Slice thickness: 2.5–5.0 mm	Retromolar trigone (9)	Tumour on the inside of the mandible or the normal medulla high signal replaced by an intermediate signal or an inflammatory reaction in T1 window	Compromise of spongy and medullary bone	Fixed and decalcified	Consider erosion and invasion as positive
	CT	Philips Tomoscan 350 (Philips) or Siemens Plus (Siemens Healthcare). Slice thickness: 5–6 mm	Floor of the mouth (20)	Destruction of the external cortical bone and/or medullary bone
	Panoramic	Siemens Orthopantomograph (Sirona Dental Company, Bensheim, Germany) 10		Three categories: no compromise, minimal erosion or extensive invasion Invasion: much bone destruction and replacement by tumour

FDG, fludeoxyglucose; FOV, field of view; n.i., no information/not enough information available; PET, positron emission tomography.