Image RECONSTRUCTION & PROCESSING

Question 1

During a CT scan, numerous measurements of the transmission of X-rays through a patient are acquired at many angles

This is the basis for _____

Answer 1

reconstruction of the CT image.

Question 2

are taken from a large number of angles and backprojected (d) yielding a strongly blurred image

Answer 2

Transmission profiles

Question 3

Mathematics shows that simple backprojection is not

sufficient for accurate image reconstruction in CT..

Instead a ___ must be used ⚫It is the standard for image reconstruction in CT.

Answer 3

filtered backprojection

Question 4

Solves number of simultaneous equations

Answer 4

Algebraic reconstruction

Question 5

(statistical) reconstructions are sometimes used

• These are routinely used in nuclear medicine. • They are becoming available for commercial CT scanners

Answer 5

Iterative

Question 6

Potential benefits of iterative reconstructions ⚫ the removal of streak artefacts (particularly when fewer projectionangles are used) ⚫ better performance in ____

Answer 6

low-dose CT acquisitions

Question 7

is the most frequently applied
technique for CT reconstruction

Answer 7

Filtered backprojection

Question 8

3 domains in filterrd backprojection

Answer 8

Object, Radon & Fourier space

Question 9

The three domains associated with the technique of filtered backprojection are

a) __ (linear attenuation values).

b) ____ (projection values recorded under many angles) this domain is also referred to as sinogram space where Cartesian coordinate are used).

c) _____
which can be derived from object space by a 2D Fourier transform.

Answer 9

Object space
Radon space
Fourier space

Question 10

theorem states that the 1D Fourier transform of the projection profile yields an angulated line in (Cartesian) Fourier space at the angle of the projection

Answer 10

Fourier slice

Question 11

A 2D Radon transform
converts the object
space into __
space.

Answer 11

Radon

Question 12

The creation of 2D Radon
space is carried out during a CT
scan: projections are recorded
and they are stored as ___
in 2D Radon space

Answer 12

raw data

Question 13

Multi-slice or multi-row scanners enabled *

Answer 13

Thinner slicesLonger scan volumesFaster scan volumes

Question 14

A typical acquisition with a single detector row scanner covered __mm.

Answer 14

5

Question 15

Techniques for reconstruction include*

Answer 15

Simple backprojection
*Algebraic reconstruction
*Iterative reconstruction
*Filtered back projection

Question 16

The 2D image space is defined as ƒ(x,y), where __ are the cartesian coordinates in image space.

Answer 16

(x,y)

Question 17

One 1D projection of the 2D image space with equidistant
and parallel rays yields one line in Radon space
• expressed as the projection p(t,θ),
where _ is the distance from
the projected x-ray to the
iso-center and
θ is the ____

Answer 17

t
projection angle

Question 18

2D Fourier space is sometimes
also referred to as ___

Answer 18

k-space

Question 19

A reconstruction can thus, at least theoretically, be achieved by first a construction of the ___
F(u,v) by many1D Fourier transforms of the projection
profiles measured under many projection angles, and subsequently a 2D inverse Fourier transform of the 2D fourier space to the 2D image space.

Answer 19

2D Fourier space