History - fundamental - development of CT system

1972 – First clinical CT scanner- Used for head examinations -80 x 80 matrix -4minutes for each scan -8 levels of grey -overnight image reconstruction... Nobel man 1979 Nobel Prize in Ph

DR NGUYEN XUAN THUC

1972 – First clinical CT scanner

- Used for head examinations -80 x 80 matrix

-4minutes for each scan -8 levels of grey

-overnight image reconstruction

The first clinical scan

1st Oct, 1971

Nobel man (1979 Nobel Prize in Physiology and Medicine.) Godfrey Hounsfield with an

early version of the CT scanner - 1972

The first clinical CT scanners were installed between 1974 and 1976 The original systems were dedicated to head imaging only

2004 – 64 slice CT scanner

- Used for whole body -1024 x 1024 matrix -0,33s per revolution -64 images per revolution -overnight image reconstruction -0.4mm slice thickness

-20 images reconstructed/second

PHILIPS 256

SIEMEN 256

TOSHIBA 320

CT NUMBERS FOR VARIOUS BODY TISSUES

( H OUNSFIELD/ U NIT)

CT NUMBERS FOR VARIOUS BODY TISSUES

( H OUNSFIELD/ U NIT)

PARTIAL VOLUME EFFECT ON CT

S- 1

S- 2

S- 3

S- 6

S- 7

Hemorrhage?

Unenhanced CT image shows

a 1-cm lesion isodense

partially intraparenchymal

lesion measuring 20 HU

Nephrographic phase

Enhanced attenuation was 50 HU (pseudoenhancement 30

HU).Lesion revealed a cystic pattern on US and was stable for morethan 3 years on CT follow-up

Different windowing in CT allows optional evaluation of each organs; e.g subdural window (for subdural blood), brain window (for brain parenchyma), bone window (for bone), etc

Types of iodinated contrast

- Ionic

- Nonionic

(No change in death rate from reaction

but number of reactions is decreased by factor of 4 to compare with ionic).

1 Chest x ray approximates the same risk as:

- 1 year watching TV

- 1 coast to coast airplane flight

1 Head CT is approximately 20 chest x ray