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W.C.Roentgen discovers "a new kind of rays", later referred to as roentgen rays in his honor.
Roentgen called his discovery X-rays to indicate that it was unknown type of radiation. -
First "tomographic" technique was developed between 1910-1960. It creates cross-sectional image by beaming x-ray from multiple angles. A number of people were working alone and with no knowledge of each other. They called their discovery statigraphy, planigraphy, transverse axial tomography, laminigraphy, stereoradiography... -
Physicist Allan Cormack first proposed a method to improve tomographic imaging. Rather than use X-rays to make photographs (the traditional method), Cormack suggested that physicians measure X-rays after they passed through a body to see how much radiation had been absorbed. He also provided mathematical formulas for constructing images of specific cross-sections using the measurements. Cormack’s article generated no medical interest, however. -
Mathematic theories from Cormack were adopted by Godfrey Hounsfield to reconstruct a 3D picture of a box.
Hounsfield worked for EMI, the company that owned The Beatles’ music. EMI used the profits made from Beatles records to invest in Hounsfield’s scanning technology.
It led to further funding first CT scanner. -
The first EMI-scanner was installed in Atkinson Morley Hospital in Wimbledon, England and the first patient brain-scan was done on 1 October 1971 by Hounsfield and Dr. Ambrose and publicly announced in 1972.
The original 1971 prototype took 160 parallel readings through 180 angles, each 1° apart, with each scan taking a little over 5 minutes. The images from these scans took 2.5 hours to be processed by algebraic reconstruction techniques on a large computer. -
The first computed tomography (CT) scanner in the US was installed in June 1973 at the Mayo Clinic in Rochester, MN. -
In 1973 American dentist and biophysicist Robert Ledley of Georgetown University developed the ACTA 0100 CT Scanner — the first whole-body computed tomography scanner.
It took approximately 20 seconds to acquire a single image slice, making full-body scans feasible, but patients still had to hold breath during process – a key distinction from the EMI scanner, which could not perform body scans due to its five-minute acquisition time for a single slice. -
EMI 5000-series, a second-generation design with 30 detectors over 10 deg, with the translation and rotation of the heavy gantry reduced to slightly more than 1 s, achieving a scan time of 20-s to facilitate breath-hold imaging to reduce motion effects.
While these scan times were compatible with breath-hold imaging in many individuals, extracranial image quality was inconsistent due to random patient, organ, and peristaltic motion effects. The field needed even higher speed scanning. -
Varian Associates developed a unique system, the first of which was installed at Stanford in late 1975.
Like most of the other early third-generation scanners, it had a xenon ionization chamber (301 channels) and pulsed x-ray source, but unlike all the other systems of the time, it had a slip-ring that supported continuous gantry rotation. -
Third generation scanners improved scan speed but suffered from ring artefacts from imperfect detector channels.
The problem was solved by CT system with a stationary ring of detectors around the patient with a tube that rotates in the space between the patient and the detector ring.
The problems that appeared: need more detectors, in-plane scatter, higher skin dose for patient. -
The Philips Tomoscan 300, introduced in 1977, also had a xenon detector but offered the unique feature of variable magnification. The source and detector, rigidly coupled to each other could be repositioned with respect to the center of rotation to use all the detectors for both small and large fields of view. -
Axel described the theoretical possibility of using rapid CT acquisition to analyze CT perfusion characteristics.
Perfusion CT permitted calculation of cerebral blood volume, transit times, and cerebral blood flow, which have proved powerful additions in the assessment of acute ischemia, stroke and the characterization of brain tumors. -
In 1989, the first report of a practical spiral CT scanner was presented at the RSNA meeting in Chicago by Dr. Willi Kalender.
The spiral/helical CT scanners developed after 1989 were referred to a single slice spiral/helical or volume
CT scanners. -
The first scanner with more than one row of detectors was introduced by Elscint in 1992. This scanner had 2 rows of detectors, and was developed primarily to help address the x-ray tube heating problem.
The first scanners of the “modern MSCT era” were introduced in late 1998 and consisted of 16 rows of detector elements.
Because of the limitations in acquiring large amounts of data, the first versions of modern MSCT scanners limited simultaneous data acquisition to 4 slices. -
Portable CT scanners can be brought to the patient's bedside and do a scan without getting the patient out of bed. Some portable scanners are limited by their bore size and therefore mainly used for head scans. -
During 2003 and 2004, MSCT manufacturers introduced models with both fewer than and more than 16 channels.
By 2005, 64-slice scanners were announced, and installations by most manufacturers began.
The approach used by most manufacturers for 64-slice detector array designs was to lengthen the arrays in the z-direction and provide all submillimeter detector elements: 64 × 0.625 (0.5) mm (total z-axis length up to 40 mm). -
A dual source CT (DSCT) is a CT system with two x-ray tubes and two detectors at an angle of approximately 90°. Both measurement systems acquire CT scan data simultaneously at the same anatomical level of the patient (same z-position). DSCT provides temporal resolution of approximately a quarter of the gantry rotation time for cardiac, cardio-thoracic and pediatric imaging. -
Developed 320-row area detector CT (Aquilion ONE™)
Up to 16 cm z-axis coverage
0.5 mm × 320 PUREViSION detector
0.275 sec rotation -
New Ultra-High Resolution CT detector 0.25 mm, 1024x1024 matrix capable of resolving anatomy as small as 150 microns. -
In 2021, the FDA approved Siemens' photon-counting scanner. The scanner counts individual x-ray photons that pass through a patient and discriminates their energy, increasing the detail supplied to the reader. The technique also reduces the amount of x-rays needed for a scan. -
AI promise of further reductions in patient radiation dose through optimization's of data acquisition processes, image reconstruction parameters, advanced reconstruction algorithms, and image denoising methods.
AI-based methods to automatically segment organs or detect and characterize pathology have been translated out of the research environment and into clinical practice to bring automation, increased sensitivity, and new clinical applications to patient care.