ADVANCED IMAGING MODALITIES

DEPT. OF ORAL MEDICINE & RADIOLOGY, MESDC

• Digital radiography
• CT
• CBCT
• MRI
• Scintigraphy
• SPECT, PET
• Ultrasound (USG)

Computed Tomography (CT)

Indications

• Investigation of intracranial diseases including tumors, hemorrhage and infarcts
• 3 D CT for assessment of fractures and reconstructive surgery for treatment of acquired and congenital disorders
• Diagnosis of infections, osteomyelitis, cysts, benign & malignant tumors
• Assessment for implant placement
• Investigation of osteomyelitis

Axial

(Transverse)

This is an Axial image..

…that represents this area of anatomy

Coronal

Coronal Plane slices through the anatomy from side to side.

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Sagittal

Sagittal Plane is a slice through the anatomy from front to back

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CORONAL VIEW

AXIAL VIEW

• HELICAL CT
• SPIRAL CT
• 3D CT
• CTA
• (SPECT)Single Photon Emission Computed Tomography
• PET (positron emission tomography)
• CBCT

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Advantages of CT

• Elimination of superimposition of structures outside the area of interest
• Detailed imaging of the intracranial lesions
• Imaging of hard and soft tissues
• Images can be manipulated
• Axial tomographic sections obtainable
• Reconstruction of images
• Image enhancement using IV contrast media

Disadvantage

• Expensive
• High radiation
• Metallic objects like filling produce artifacts

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CBCT

• Cone-Beam Computed Tomography
• Uses a cone shaped source of ionizing radiation

Advantage

• Reduced size of the instrument when compared with conventional CT
• Less expensive
• Short scan time
• Sub millimeter resolution
• Low patient radiation dosage
• Reconstruction and viewing can be done in personal computer

Disadvantage

• Lack clarity and utility of conventional CT images
• Poor soft tissue contrast

CT Versus CBCT

Applications of CBCT

• Implant site assessment:
• Bone density
• Shape, height & width of alveolus
• Nerve proximity, sinus floor etc
• Designing surgical stents
• Virtual implant creation

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Clinical Applications of CBCT- Dental Implants

• oral & maxillofacial surgery
• Locating impacted tooth precisely
• Relationship with vital structures
• Location & extend of cyst & tumors
• Identification of fractures & its displacements
• Cleft lip & palate
• Maxillofacial reconstruction

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• Orthodontics
• 3D visualization of craniofacial skeleton
• Mini implant placement
• 3D cephalograms
• Orthognathic assessment

Ceph Tracing�

• Endodontics
• 3D anatomy of root canals
• Identify missed canals
• Locate broken instuments
• Detect vertical root fractures
• Periapical & endoperio lesions

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• Analysis and diagnosis of TMJ problems
• Condylar erosions, developmental anomalies

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• CBCT assisted airway analysis

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• Periodontal assesment

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• Identify origin of orofacial pain

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Nuclear medicine /Radioisotope imaging

• A form of functional imaging
• Injection of radioactive isotope into the patient that have an affinity for particular tissues.
• Radioactive compounds become concentrated in the target tissue and their radiation emissions are detected and imaged using a gamma camera

Radioisotopes

• Technetium-salivary glands, thyroid, bone, blood, liver, lung, heart
• Gallium-Tumours, inflammation
• Iodine-Thyroid
• Krypton- Lung

Indication

• Assessment of site and extend of bone metastases
• Investigation of salivary gland
• Investigation of thyroid gland
• Investigations of the brain
• Evaluation of bone grafts

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Advantage

• Target tissue function is investigated
• Whole skeleton can be imaged in one bone scan
• Computer analysis and enhancement of the results available

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Disadvantages

• Poor image resolution-minimal information regarding target tissue anatomy
• Radiation dose to the whole body high
• Images are not disease specific
• Difficult to localize exact anatomical site of source of emissions
• Some investigation take several hours
• Facilities not widely available

Magnetic resonance imaging (MRI)

Indications

• Assessment of intracranial lesions
• Evaluation of site, size and extend of soft tissue tumors
• Imaging of the TMJ to show the bony and soft tissue components
• Implant assessment

Advantages

• No ionizing radiation
• No adverse effects
• Image manipulation available
• 3D reconstruction of images
• Excellent differentiation between normal and abnormal

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Disadvantage

• Time consuming
• Hard tissue image is not good
• Contra indicated in surgical clips, cardiac pacemakers, cochlear implants, first trimester of pregnancy
• Metallic objects should be replaced with ferromagnetic substance
• Equipment is claustrophobic & noisy
• Expensive & not widely available

COMPARISON OF CT with MRI

CT IMAGE

MRI IMAGE

Ultrasound

• 1 to 20 MHz ultrasound beam directed into the body from a transducer
• Some is reflected back by tissue interfaces to produce echoes
• Echoes picked up by the transducer
• Converted to electrical signal & displayed on the monitor

Indication

• Evaluation of the swelling of neck, thyroid, cervical nodes, salivary glands
• Detection of salivary gland & duct calculi
• Vascular lesions- anuerysms, atheromas etc
• Fetal anomalies
• Ultrasound guided biopsy

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Advantage

• No ionizing radiation
• No harmful effects
• Good differentiation between different soft tissues
• Widely available and inexpensive

Disadvantage

• Use restricted to superficial structures
• Limited uses in head and neck
• Technique is operator dependent
• Images difficult to interpret

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Thank you