CT Basics and Principles Series 1

CT BASICS AND PRINCIPLES

4 GENERATIONS OF CT SCANNERS

INVENTION OF CT

• CT WAS INVENTED IN 1972 BY GODFREY HOUNSFIELD AND WAS ONLY ABLE TO

PERFORM HEAD SCANS AT THAT TIME. CT SCANNERS BECAME AVAILABLE IN

THE MEDICAL MARKET IN THE 1980S. THIS TECHNOLOGY WAS FAIRLY NEW AT

THAT TIME, AND THERE WASN’T A HUGE DEMAND DUE TO THE LENGTH OF TIME

IT TOOK TO COMPLETE ONE HEAD SCAN ON A PATIENT.

GENERATION OF CT SCANNERS

FIRST GENERATION

• SINGLE DETECTOR

• PENCIL BEAM

• TRANSLATE-ROTATE TUBE

DETECTOR MOVEMENT

• SCAN TIMES TOOK ABOUT AN

HOUR OR MORE

• ONLY HEAD IMAGING WAS

POSSIBLE

SECOND GENERATION

• MULTIPLE DETECTORS

• PENCIL BEAM

• STILL USED TRANSLATE-ROTATE

METHOD

• 1-2 MINUTES PER SLICE

THIRD GENERATION

• MULTIPLE ROTATING DETECTORS

IN AN ARC

• FAN BEAM

• ROTATE-ROTATE TUBE DETECTOR

METHOD

• SCAN TIME OF 5 SECONDS

• ALL SCANNERS TODAY USE THIS

TECHNOLOGY

FOURTH GENERATION

• STATIONARY DETECTORS

ARRANGED IN OUTER RING

• FAN BEAM

• ONLY THE TUBE ROTATES AROUND

THE PATIENT

• SCAN TIME IS A FEW SECONDS

• AVOIDS RING ARTIFACT

CT MACHINE COMPONENTS

• A CT UNIT IS DESIGNED WITH THE

FOLLOWING:

• GANTRY

• X-RAY TUBE

• DETECTOR ARRAY

• PATIENT TABLE (COUCH)

• CONTROL CONSOLE

CT ADVANCEMENTS

ADAPTIVE ITERATIVE RECONSTRUCTION

• THIS ADVANCEMENT HAS HELPED WITH DOSE REDUCTION TO THE PATIENTS

WITHOUT SACRIFICING IMAGE QUALITY BY NOISE REDUCTION TO IMAGES AND

REDUCING PATIENT DOSE BY 30-40%.

• COMMON ITERATIVE RECONSTRUCTION APPLICATIONS ARE:

1. ASIR (GE)

2. SAFIRE (SIEMENS)

3. AIDR 3D (TOSHIBA)

4. I-DOSE 4, IMR (PHILIPS)

REFERENCES AND ACKNOWLEDGEMENTS

CT IMAGES COURTESY OF:

• SLIDESHARE.NET

• HTTP://OPENI.NLM.NIH.GOV/