Podcast
Questions and Answers
What does CT stand for?
What does CT stand for?
What is the goal of CT?
What is the goal of CT?
To overcome the limitations of radiography and conventional tomography by minimal superimposition, improve image contrast, and record very small tissue differences.
CT is qualitative rather than quantitative imaging.
CT is qualitative rather than quantitative imaging.
False
Each cross-sectional slice in CT represents a specific ______ in the patient.
Each cross-sectional slice in CT represents a specific ______ in the patient.
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Match the following terms:
Match the following terms:
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Define Computed Tomography (CT).
Define Computed Tomography (CT).
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What are the goals of CT? Select all that apply.
What are the goals of CT? Select all that apply.
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Radiography is a quantitative procedure.
Radiography is a quantitative procedure.
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Each cross-sectional slice in CT represents a specific plane in the patient's __________.
Each cross-sectional slice in CT represents a specific plane in the patient's __________.
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What do Hounsfield units (CT numbers) represent?
What do Hounsfield units (CT numbers) represent?
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Match the following terms with their definitions:
Match the following terms with their definitions:
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What are advantages of CT? Select all that apply.
What are advantages of CT? Select all that apply.
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Study Notes
Computed Tomography (CT)
- CT is a type of cross-sectional imaging that eliminates unwanted planes or layers of the body.
- A thin beam is transmitted through a specific cross-section, striking special detectors opposite the x-ray tube.
Goal of CT
- Overcome the limitations of radiography and conventional tomography.
- Minimize superimposition.
- Improve image contrast.
- Record very small differences in tissue contrast.
Limitations of Radiography
- Superimposition of structures in one film, making it difficult to distinguish particular details.
- Radiography is qualitative rather than quantitative, making it difficult to distinguish between homogeneous objects of non-uniform thickness and heterogeneous objects.
CT Defined
- Images are cross-sectional, showing only parts of the anatomy imaged at a particular level.
- Each cross-sectional slice represents a specific plane in the patient.
- Slice thickness is referred to as the z-axis.
Cross-Sectional Images
- Data that form the CT slice are further sectioned into elements called pixels.
- Width is represented by x, and height is represented by y.
Pixels and Voxels
- A pixel is a 2D square shade of gray.
- A voxel is a 3D volume of gray.
Attenuation and Hounsfield Units
- Attenuation is the absorption of x-rays by different tissues.
- Hounsfield units (CT numbers) represent the percent difference between the x-ray attenuation coefficient for a voxel and that of water, multiplied by 1000.
Advantages of CT
- Excellent low-contrast resolution due to highly collimated x-ray beams and special detectors.
- Ability to change window width and level to suit the observer's needs.
- Spiral CT includes volume data acquisition in a single breath, improving 3D imaging and multiplane image reformatting.
- Facilitates diagnosis using various techniques, such as xenon CT and determination of bone mineral content.
Limitations of CT
- Difficulty imaging soft tissue surrounding bone, such as the posterior fossa and spinal cord.
- Presence of metallic objects produces streak artifacts.
CT Reconstruction
- MPR (Multi-Planar Reconstruction) reconstruction using spiral scanning.
- Curved reformatting reconstruction using spiral scanning.
- SI joint sagittal image used to reconstruct coronal image.
CT-Guided Biopsy
- Allows for accurate placement of catheters and biopsies under CT guidance.
- Enables drainage of fluid collections and pus.
CT Angiography
- Visualizes blood vessels and detects vascular diseases.
- Used for brain, renal, and pulmonary angiography.
CT Reconstruction Applications
- Bone reconstruction.
- Lung reconstruction.
Computed Tomography (CT)
- CT is a type of cross-sectional imaging that eliminates unwanted planes or layers of the body.
- A thin beam is transmitted through a specific cross-section, striking special detectors opposite the x-ray tube.
Goal of CT
- Overcome the limitations of radiography and conventional tomography.
- Minimize superimposition.
- Improve image contrast.
- Record very small differences in tissue contrast.
Limitations of Radiography
- Superimposition of structures in one film, making it difficult to distinguish particular details.
- Radiography is qualitative rather than quantitative, making it difficult to distinguish between homogeneous objects of non-uniform thickness and heterogeneous objects.
CT Defined
- Images are cross-sectional, showing only parts of the anatomy imaged at a particular level.
- Each cross-sectional slice represents a specific plane in the patient.
- Slice thickness is referred to as the z-axis.
Cross-Sectional Images
- Data that form the CT slice are further sectioned into elements called pixels.
- Width is represented by x, and height is represented by y.
Pixels and Voxels
- A pixel is a 2D square shade of gray.
- A voxel is a 3D volume of gray.
Attenuation and Hounsfield Units
- Attenuation is the absorption of x-rays by different tissues.
- Hounsfield units (CT numbers) represent the percent difference between the x-ray attenuation coefficient for a voxel and that of water, multiplied by 1000.
Advantages of CT
- Excellent low-contrast resolution due to highly collimated x-ray beams and special detectors.
- Ability to change window width and level to suit the observer's needs.
- Spiral CT includes volume data acquisition in a single breath, improving 3D imaging and multiplane image reformatting.
- Facilitates diagnosis using various techniques, such as xenon CT and determination of bone mineral content.
Limitations of CT
- Difficulty imaging soft tissue surrounding bone, such as the posterior fossa and spinal cord.
- Presence of metallic objects produces streak artifacts.
CT Reconstruction
- MPR (Multi-Planar Reconstruction) reconstruction using spiral scanning.
- Curved reformatting reconstruction using spiral scanning.
- SI joint sagittal image used to reconstruct coronal image.
CT-Guided Biopsy
- Allows for accurate placement of catheters and biopsies under CT guidance.
- Enables drainage of fluid collections and pus.
CT Angiography
- Visualizes blood vessels and detects vascular diseases.
- Used for brain, renal, and pulmonary angiography.
CT Reconstruction Applications
- Bone reconstruction.
- Lung reconstruction.
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Description
Learn about the definition and principles of Computed Tomography (CT) scans, a type of cross-sectional imaging. Understand how it works and its applications in medicine.
