Data and Pitch

raw data

data collected from the scan, there is no HU unit assigned. Because of this it cannot be reformatted to 2D or 3D. However this information can be stored and used to reconstruct in different formats

image data

after raw data is given a HU value. can be used for reformatting iamges in other planes.

what is retrospective reconstruction

information can be stored and used to reconstruct in different formats. this is in raw data

MDCT: Pitch

uTable movement during each 360⁰ rotation (1 revolution of x-ray tube)                  Beam width

beam width formula

(BW= number of slices x slice thickness)

what is pitch

parameter that describes the movement of the table throughout helical scan. essentially the travel distance of the table per 360 roation o fthe xray tube DIVIDED by the collimated xray beam width

what does pitch affect

1. dose

2. quality image

3. scan time

what is the ideal pitch

1:1 or just 1

is pitch usually changed from pre-programmed standards

no but can be

increasing pitch…

uLarger volume of tissue covered

uDecreases patient dose

uIncreases table speed

uDecreases image quality

  anatomy covered in 1 rotation

decreasing pitch…

uSmaller volume of tissue covered

uIncreases patient dose

uDecreases table speed

uIncreases image quality

  anatomy not covered in 1 rotation

ideally pitch should remain below…why?

1.5. maintain image quality and reduce patient dose

T/F binning occurs when multiple detectors are combined provide the desired overall section thickness

true

x occurs when raw data is retrieved to create new images

Retrospective Reconstruction