Regarding spatial resolution: a. CT has a better spatial resolution c

1.	Regarding spatial resolution: a. CT has a better spatial resolution compared with film-screen radiography b. It is 3–5 line pairs mm-1 in digital imaging c. It depends on the width of the projection path d. The source-to-detector distance affects unsharpness but not the spatial resolution e. If the matrix is 512 x 512 and the field of view is 60 cm, then the spatial resolution would be 4 line pairs mm-1
Answer» a. False. The spatial resolution in CT is 20 line pairs cm^-1while in film-screen radiography it is 8–12 line pairs mm^-1 b. True. c. True. Spatial resolution in CT depends on the following: The matrix and field of view An algorithm: like bone reconstruction, this enhances the edge of high-contrast structures and increases the spatial resolution at the cost of increased noise The width of the projection path, which is affected by focal spot size/source to isocentre and source to detector distance/size of the sensitive area of the detector The number of projections sampled in each rotation. In the z direction, this depends on slice thickness or pitch: the higher the pitch, the less the spatial resolution. This effect is less important in a multi-slice scanner. d. False. e. True. Spatial resolution = 1/(2 pixel size) and pixel size = field of view/matrix = 1/(2 60/512) = 4.3; therefore, the spatial resolution is around 4 line pairs mm^-1 .

Regarding spatial resolution: a. CT has a better spatial resolution compared with film-screen radiography b. It is 3–5 line pairs mm-1 in digital imaging c. It depends on the width of the projection path d. The source-to-detector distance affects unsharpness but not the spatial resolution e. If the matrix is 512 x 512 and the field of view is 60 cm, then the spatial resolution would be 4 line pairs mm-1

Answer»

a. False. The spatial resolution in CT is 20 line pairs cm^-1while in film-screen radiography it is 8–12 line pairs mm^-1

b. True.

c. True. Spatial resolution in CT depends on the following:

The matrix and field of view
An algorithm: like bone reconstruction, this enhances the edge of high-contrast structures and increases the spatial resolution at the cost of increased noise
The width of the projection path, which is affected by focal spot size/source to isocentre and source to detector distance/size of the sensitive area of the detector
The number of projections sampled in each rotation. In the z direction, this depends on slice thickness or pitch: the higher the pitch, the less the spatial resolution. This effect is less important in a multi-slice scanner.

d. False.

e. True. Spatial resolution = 1/(2 pixel size) and pixel size = field of view/matrix = 1/(2 60/512) = 4.3; therefore, the spatial resolution is around 4 line pairs mm^-1 .

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