Module A Computed Tomography Physics, Instrumentation, and Imaging

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Historical development of Computed Tomography  Godfrey Newbold Hounsfield (1919 – 2004) 1979 Nobel Prize in Medicine 1979 Nobel Prize in Medicine Attenuation scale used in CT Attenuation scale used in CT  Allan McLeod (1924 – 1998) South African physicist South African physicist

Continue……. Timeline for the Historical development of Computed Tomography  1917 Johann Radon Austrian mathematician Austrian mathematician Work resulted in the mathematical basis for tomography Work resulted in the mathematical basis for tomography  1955 K.C. Tsien Introduced computers in Radiology Introduced computers in Radiology

Continue……. Timeline for the Historical development of Computed Tomography  1957 Allan McLeod Cormack First x-ray reconstruction using aluminum/wood phantom First x-ray reconstruction using aluminum/wood phantom  1967 Godfrey Newbold Hounsfield Developed first CT scanner Developed first CT scanner headhead

Continue……. Timeline for the Historical development of Computed Tomography  1970 Godfrey Newbold Hounsfield 1 st demonstration 1 st demonstration  1971 James Ambrose Atkinson-Morley’s Hospital Atkinson-Morley’s Hospital Installation of scanner Installation of scanner

Continue……. Timeline for the Historical development of Computed Tomography  1972 Hounsfield and Ambrose Atkison-Morley’s Hospital Atkison-Morley’s Hospital 1 st patient scanned 1 st patient scanned  1973 First scanners installed in US Mayo Clinic and Massachusetts General Hospital

Continue……. Timeline for the Historical development of Computed Tomography  1974 Robert S. Ledley and staff 1 st whole body scanner 1 st whole body scanner National Biomedical Research Foundation National Biomedical Research Foundation Georgetown University Medical Center Georgetown University Medical Center ACTA ACTA

Continue……. Timeline for the Historical development of Computed Tomography  1979 Cormack and Hounsfield Nobel Prize in Medicine Nobel Prize in Medicine Computerized Axial Tomography (CAT) Computerized Axial Tomography (CAT)

Continue……. Timeline for the Historical development of Computed Tomography  1989 Dr. Willi Kalender RSNA RSNA 1 st Spiral/Helical 1 st Spiral/Helical Volumetric Acquisition CT ScannersVolumetric Acquisition CT Scanners Siemens and Toshiba Siemens and Toshiba

Continue……. Timeline for the Historical development of Computed Tomography 1998 Multidetector-Row CT Scanner Additional milestones in the development of CT can be found in Chapter 1, Seeram, Computed Tomography 2 nd edition.

CT Generations  generation – refers to the geometry used in data acquisition. scanning geometry scanning geometry scanning motion scanning motion number of detectors number of detectors

CT  CT is defined as a three-step process 1. Data acquisition 2. Image reconstruction 3. Image display, manipulation, communication, archival, etc.

First Generation  EMI  Head only  Pencil (parallel) beam  1 – 2 detectors  Translate – Rotate mode  1 degree increments  > 60 second scan times per slice

Second Generation  Fan – Beam Geometry  Full body  Translate – Rotate mode  Multiple detectors (solid – state – sodium iodide)  20 – 60 second scan time per slice

Third Generation  GE Medical Systems  Rotate – Rotate mode Incorporation of slip ring technologyIncorporation of slip ring technology  Focused tube and detectors  Detector Array XenonXenon  5 – 8 second scan times

Fourth Generation  Rotate – Stationary Tube rotation/stationary detectorsTube rotation/stationary detectors  < 5 second scan time per rotation/slice

Fifth Generation  Emitron No moving x-ray or detector partsNo moving x-ray or detector parts  Electron Gun  Photons accelerated upwards through patient to DAS

Continue …… Fifth Generation  Also called Electron Beam CT  Heart imaging  1/20 th second scan time  Chapter 5 in Seeram’s text shows picture

Beam Geometry  Pencil/Parallel - 1 st generation  Fan - 2 nd generation and used today in conventional CT.  Cone - due to use of multiple detector rows  Total of 3 beam geometries used in CT today

continue …….. Beam Geometry Pencil (parallel) beam geometry – is defined by a set of parallel rays that generate a projection profile Fan beam geometry – defined by its divergent ray. Cone beam geometry – introduced as a result of the incorporation of multiple rows of detectors. The beam diverges in y axis and in the Z axis.