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CT & noise

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lee seong ju

on 28 February 2014

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Transcript of CT & noise

Tradeoff between
dose & image

Image Reconstruction
Reconstruction process
Toshiba Iterative Reconstruction
Figure : AIDR 3D is an advanced iterative reconstruction algorithm that reduces noise both in the raw data domain and also in the reconstruction process in 3-dimensions.
Iterative Reconstruction
Noise?
Filtered back projection
Iterative
Reconstruction
Lee seong ju
Noise Index = SD value
AIDR 3D Integrated
AIDR 3D has been designed to work in both the three Dimensional (3D) raw data and reconstruction domains
Adaptive
Iterative
Dose reduction AIDR3D
Iterative Reconstruction
Siemens Iterative Reconstruction
GE Iterative Reconstruction
radiation dose
image quality
ICRP (International Commission on
Radiological Protection)

- Justification, Optimization, Limitation
Optimization Image Quality & Radiation Dose
CTDI (computed tomography dose index)
Dose-length product (DLP)
Effective dose
CT scan 8~10mSV (chest X-ray : 0.02
mSV
)
1 year < 250mSV

2007 NEJM - 1year :
10 CT scan

: 1000

Plain X-ray(chest)
Low grade Level
In the projection-space
Statistical model and scanner model
Filtering in the photon count data before the logarithm operation
Adaptation of filter length according to relative noise level

In the image-space
Advanced operators for smoothing with edge preservation
Iteration
Blending of the FBP image and the iteratively processed image
The noise index is referenced to the
standard deviation of CT numbers
within a region of interest in a
water phantom of a specific size
Thanks for your attention!
A L A R A
ICRP(International Commission on
Radiological Protection)

- Justification, Optimization, Limitation
Recon Tree



• Traditional
successive substitutions
iterations
◦ e.g., Joseph and Spital (JCAT, 1978) bone correction
◦ usually only one or two “iterations”
◦ not statistical


Algebraic
reconstruction methods
◦ Given sinogram data y and system model A, reconstruct object x by
“solving” y = Ax
◦ ART, SIRT, SART, ...
◦ iterative, but typically not statistical
◦ Iterative filtered back-projection (FBP):


Statistical
reconstruction methods
◦ Image domain
◦ Sinogram domain
◦ Fully statistical (both)
◦ Hybrid methods (e.g., AIR, SPIE 7961-18, Bruder et al.)
“Iterative” vs “Statistical”
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