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What are the four main image quality factors?
- Spatial resolution
- Contrast resolution
- Noise
- Artifacts
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What is the most significant geometric factor for spatial resolution?
Detector aperture width
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What factors affect spatial resolution?
- Slick thickness
- Reconstruction algorithm
- Focal spot size
- Display FOV
- Matrix
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What factors affect contrast resolution?
- Slick thickness
- Reconstruction algorithm
- X-ray beam energy
- Image display
- Patient size and detector sensitivity also have direct effect on contrast resolution
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What scan parameters affect noise?
- Slice thickness
- Reconstruction algorithm
- X-ray beam energy
- Matrix size
- Also patient size and scattered radiation contribute to noise
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What is incrementation?
The distance the table moves between scans aka scan index
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Define SSD. What would you use SSD for?
- Shaded Surface Display. CT numbers above threshold selected for 3D.
- Fractures
- Soft tissue trauma
- Vessel diagnosis
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Define MIP. What would you use MIP for?
- Maximum Intensity Projection: Very bright images. Excludes unwanted anatomy below a certain CT number.
- Vascular structures
- Contrast filled structures
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What can endoluminal imaging be used for?
- Air-containing structures
- Contrast enhanced blood vessels or bladder
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Define pitch.
Pitch is the ratio of the speed of table motion to slice thickness.
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Define segmentation and what it is used for.
A procedure that removes unwanted structures from the image, where different structures have similar radiodensity.
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What are the three considerations for IV contrast media injections?
Volume, rate, scan delay.
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What direction are CT brain scans done?
Caudal-cranial.
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What direction are thorax CT scans done?
Cranio-caudal.
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What direction are abdomen/pelvis CT scans done?
Cranio-caudal.
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Does spiral CT give more or less dose than single slice?
Depends on choice of factors. In practice, gives more.
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List the factors that affect CT dose.
- kVp
- mAs
- Rotation or exposure time
- Section or slice thickness
- Object thickness
- Pitch
- Dose reduction techniques (mA modulation)
- Distance from tube to isocentre
- Attenuation (size of patient, pediatric vs adult)
- Filtration
- Detector efficiency
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What is the biggest risk factor in developing breast cancer?
Age. Over 75% of BC occur in women >50
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9 out of 10 women who get breast cancer have a family history of breast cancer. T/F?
False. 9 out of 10 women who get breast cancer DO NOT have a family history of breast cancer.
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List clinical indications of breast cancer.
- Pain
- Lumpiness
- Thickening skin
- Restracted/inverted nipple
- Nipple discharge
- Change in size or shape of breast
- Lumps in armpit
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What is the breast made up of?
- Ducts (carries milk from lobules to nipple)
- Lobules (milk-producing glands)
- Stroma (fatty and connective tissue)
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Where do most breast cancers begin?
In the cells lining the ducts
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Name the two routes of spread for breast cancer.
Lymphatic system or vascular system.
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What are the two standard views in mammography?
- CC: Cranial Caudal
- MLO: Mediolateral Oblique
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Why are two projections obtained in mammography?
Increases the detection rate of breast cancer by 24%. (Wald et al., 1995)
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What two things determine the quality of mammograms?
Specificity and sensitivity.
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Which quality of a mammogram decreases false positives?
Specificity: the higher the specificity, the fewer false positives.
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Which quality of a mammogram decreases false negatives?
Sensititivy: the higher the sensitivity, the fewer false negatives.
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What is the difference in purpose between screening and diagnostic mammography?
- Screening: reducing mortality rate of breast cancer
- Diagnostic: diagnosis of breast pathologies
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What are the two ways of considering the pathology of the breast?
- 1. Anatomically: ductal or lobule
- 2. Pathological classification: benign or malignant
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