Computed Tomography

By Karim Sedki

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Computed Tomography by Mind Map: Computed Tomography

1. Scanners: use xray to produce slices as in tomography BUT:

1.1. radiographic film replaced by sensitive crystal or gas detectorsScintillation (solid state) and Ionization (xenon gas) detectors.

1.1.1. X ray rotate around patient scanning one section at a time

2. System Components

2.1. Gantry:

2.1.1. circular device that houses the Data Acquisition system (DAS) = Tube, Detectors, Filters, Collimators & Analog-to – Digital Converter (ADC) Detector:Function as image receptors for remnant radiation, then converts the measurement into an electrical signal proportional to the radiation intensity. Two basic detector types are used: Scintillation (solid state) and Ionization (xenon gas) detectors.

2.2. Computer:

2.2.1. functions: 1. Control of data acquisition

2.2.2. 2. Image reconstruction

2.2.3. 3. Storage of image data

2.2.4. 4. Image display

2.3. Table

2.3.1. Automated device linked to the computer and gantry Designed to move in increments after every scan according to the technologists scan program

2.4. Operator's Console

3. Indications

3.1. Investigation of intracranial disease including tumours, haemorrhage and infarcts

3.2. Investigation of suspected intracranial and spinal cord damage following trauma to the head and neck

3.3. Assessment of fractures involving:

3.3.1. The orbits and naso-ethmoidal complex

3.3.2. The cranial base

3.3.3. The odontoid peg

3.3.4. The cervical spine

3.4. Tumour staging―assessment of the site, size and extent of tumours, both benign and malignant, affecting:

3.4.1. The maxillary antra

3.4.2. The base of the skull

3.4.3. The pterygoid region

3.4.4. The pharynx

3.5. Investigation of tumours and tumour-like discrete swellings both intrinsic and extrinsic to the salivary glands

3.6. Investigation of osteomyelitis

3.7. investigation of the TMJ

3.8. Preoperative assessment of maxillary and mandibular alveolar bone

3.9. height and thickness before inserting implants.

4. Advantages

4.1. Very small amounts, and differences, in X-ray absorption can be detected. This enables:

4.1.1. Detailed imaging of intracranial lesions

4.1.2. Imaging of hard and soft tissues

4.1.3. Excellent differentiation between different types of tissues, both normal and diseased

4.2. Images can be manipulated

4.3. Axial and coronal tomographic sections of the skulls are obtainable

4.4. Reconstructed images can be obtained from information obtained in the axial plane

4.5. images can be enhanced by the use of IV contrast media providing additional information.

5. Disadvantages

5.1. Expensive Equipment

5.2. Not Available

5.3. High Radiation Dose

5.4. Risk with IV Contrast agent

5.5. Metallic artifact