Linear Tomography and CT Flashcards
The pivot point in linear tomography is called
Fulcrum
CT scanners convert x-rays into electrical signals that are viewed as grayscale differences on a flat panel screen (T/F)
True
The control panel allows you to pick the following prior to the start of a scan
Scan field of view (SFOV)
Focal Spot Size
Slice thickness
Pitch
Scan Time
KVP
mAs
In linear tomography, if the tomographic angle is made smaller, the slice thickness will be
Thicker
What is the range of CT numbers would be viewed with a window level of 500 and a window width of 150
425-575, 150/2=75, 500-75=425, 500+75=575
The pre-patient collimator determines slice thickness (T/F)
False, the predetector determines the slice thickness
A constantly moving gantry in modern CT units (spiral CT) is made possible by what technology
Slip Ring
What is the HU (Houndsfield Unit) for water
0
The focal plane in linear tomography is
The area of anatomy you can see
A negative CT number would represent
Radiolucent material
Spatial resolution in CT
Depends on pixel size
Is measured by MTF
Has units of lp/cm
CT images are able to represent soft tissue detail because of excellent contrast resolution (T/F)
True
High mA and short exposure time is the best combination for linear tomography exams (T/F)
False, High exposure time and low mAs, long and low
What factors influence noise on a CT image
kVp
Filtration
Pixel size
Slice thickness
Linearity is evaluated on a CT unit using a water bath (T/F)
False, it uses a five pin test
