Dose Reduction and Artifacts in CT

77 Pages·2013·5.42 MB·English

Dose Reduction and
Artifacts in CT
Stephen E. Hale Jr., Ph.D.
Integrated Science
Support, Inc.
Outline
(cid:1) Nature and History of CT
(cid:1) CT Dose Issues
(cid:1) Dose Reduction Capabilities
(cid:1) Dose Management
(cid:1) Artifacts in CT
(cid:1) Summary
NATURE & HISTORY OF CT
First CT - 1967
(cid:1) 1st Generation
(cid:1) Translate and
Rotate
(cid:1) Single detector
(cid:1) Hounsfield in
1967 actually
had 2 detectors
Clinical Introduction
(cid:1) First patient head scan
performed at Atkinson-
Morley Hospital in
England on 10/1/1967
(cid:1) 160 rays @ each of 180
angles, 1° apart
(cid:1) Scan took 5 minutes
(cid:1) Reconstruction took 2.5
hours
2nd Generation CT
(cid:1) Still translate and
rotate
(cid:1) Multiple detectors with
multiple beams (or a
beam with width = fan
beam)
(cid:1) Scatter increased with
wider beam
3rd Generation CT
(cid:1) Widen x-ray beam to a
fan beam
(cid:1) Array of detectors
(cid:1) Physically tie detectors
and x-ray source onto
same structure
(cid:1) Complications –
detector stability,
matching responses,
ring artifacts
4th Generation CT
(cid:1) Rotate/Stationary
(cid:1) Fixed ring of detectors
(cid:1) X-ray tube rotates
inside of detector ring
(cid:1) Issues
Size of system
–
Cost of detectors
–
Scatter removal
–
CT in Motion
EBCT – 5th Generation
(cid:1) Electron beam onto stationary target with
stationary detector array
(cid:1) 50 msec imaging times