###### Abstract  
The oral cavity constitutes a complex anatomical area that can be affected by many developmental, inflammatory, and tumoural diseases. MultiSlice Computed Tomography (MST) and Magnetic Resonance Imaging (MRI) currently represent the essential and complementary imaging techniques for detecting oral cavity abnormalities. Advanced MRI with diffusion-weighted imaging (DWI) and dynamic contrast-enhanced perfusion-weighted imaging (DCE-PWI) has recently increased the ability to characterise oral lesions and distinguish disease recurrences from post therapy changes. The analysis of the oral cavity area via imaging techniques is also complicated both by mutual close appositions of different mucosal surfaces and metal artifacts from dental materials. Trevisless, an exact identification of oral lesions is made possible thanks to dynamic manoeuvres and specific stratagems applicable on MST and MRI acquisitions. This study summarises the currently available imaging techniques for oral diseases, with particular attention to the role of DWI, DCE-PWI, and dynamic manoeuvres. We also propose MST and MRI acquisition protocols for an accurate study of the oral cavity area. computed tomography; magnetic resonance imaging; diffusion weighted imaging; perfusion weighted imaging; oral cancer; imaging techniques +
Footnote †: journal: Medical Imaging  
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Footnote 0: _Applied_  
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The open mouth technique also increases the visibility of structures obscured by dental metal artifacts, especially the soft palate but also the cheek, gingiva, oropharynx, and upper part of the mobile tongue, thus highlighting tumours or other diseases that are difficult to detect with the mouth closed (Figure 14). 3. 4. +++  
Figure 15: Open mouth with tongue extended MST technique. This manoeuvre allows to clearly separate the oral cavity from oropharyngeal structures. (**A**) Axial non-enhanced conventional MST acquisition at the level of the tongue base (*) and palatine tonsils (arrows). It is not possible to clearly distinguish the boundaries between the oral cavity and orophnx making it difficult to assess a possible extension of a tonsillar neoplasm to the tongue base and adjacent muscles (or vice versa, a tongue neoplasm towards the tonsil). (**B**) Axial contrast-enhanced open mouth with tongue extended acquisition at the same level. Tongue and orophnx with tonsils are “stretched”, isolating these different compartments from each other. (**C**) Detailed image of (**B**) where it is possible to distinguish the palatine tonsil (blue), styloglossus muscle (red), medial pterygoid muscle (green), and glosso-tonsillar sulcus (dotted line). (**D**) Reconstructed sagittal image. Proper instruction and testing of the manoeuvre are required before scanning. This technique reduces artifacts from metal material (for the same reasons of simple open mouth technique, the X-ray beam better penetrates the oral cavity without the interference of dental metal) (Figure 14) and enables a better visualisation of oral cavity/oropharynx tumours, thus allowing a more accurate staging [51]. Lingual protrusion causes \"stretching\" of the oropharyngeal structures and distends the glosso-tonsillar sulcus. Small lesions located on the lateral or ventral margin of the anterior tongue or located on the lingual apex are clearly highlighted by such manoeuvre [47]. 4. Water distension of the oral vestibule. This technique is exclusively used on MRI examinations since MRI has a high contrast for liquids by using specific sequences,  
Figure 16: Open Mouth with Tongue extended MRI technique. (**A**) T1 contrast-enhanced axial image and (**B**) T1 contrast-enhanced sagittal image showing a left tonsillar neoplasm (arrow in (**A**), outlined by white dotted line in (**B**)) where it is not possible to distinguish between the infiltration of the tongue (outlined by the red line in (**B**)) and the surrounding muscles.