The Evolution of Fluoroscopy

This gallery was prepared by Stephen Balter based, in part, on his paper Fluoroscopic Technology from 1895 to 2019 Drivers: Physics and Physiology, MEDICAL PHYSICS INTERNATIONAL Journal, Special Issue, History of Medical Physics 2, 2019

C 1896

Early fluoroscopy experiments: Physicist’s fluoroscope

Experiments, including fluoroscopy, were reported around the world within weeks of Roentgen’s discovery of X rays in 1895.
The monocular “cryptoscope” is the only item that may not have been immediately available in a typical physics lab following Roentgen’s announcement in 1895.

The investigator is using his own hand as a test-object. There were several published reports of hand injuries before the end of 1896.

Source: Anon

C 1899

Equipment testing using operators’ hands as test objects

Many early workers used images of their own hands to adjust exposures, with catastrophic consequences.

This ubiquitous photo of a seated individual’s hand is being radiographed while the standing individual is simultaneously using a cryptoscope to fluoroscope his own hand.

This image could be either a posed picture or the fluoroscopist is using his hand as a QA tool while he adjusts the apparatus.
Note the supply of additional X-ray tubes on the far wall.

Source: Anon


QA using a penetrometer in place of the operator’s hands

This tool allowed technique adjustment without the use of the operator’s hand as a test object.

It is interesting to note that this tool was promoted by an equipment manufacturer.

C 1896

Early complete X-Ray system

The unshielded X-ray tube is just right of center.

There is an attached spark-gap voltmeter mounted on the wall.

The image receptor consists of a large fluoroscopic screen.

A black cloth hood like the hood used with photographic cameras of the era isolates the operator from room light.

This system appears to have been energized by a power line instead of the more common batteries used in this era.

Source: Siemens Healthineers

Pre 1900

Chest fluoroscopy (original image is heavily edited)

The image of the chest is far too bright to be an unretouched photograph. Also, note that the patient has two left elbows.

Artistic versions of this image were widely available in the early 1900s. Their composition indicates that they were drawn from this ‘retouched’ photo.

Source: Anon


Radiation protection devices available by 1905

Personal protective equipment and tube shields were available within a few years of Roentgen’s discovery.

The cryptoscope with a mirror is intended to remove the observer from the X-ray beam (implying the tube shield shown above was also used).

Also, note the image illuminator in the lower right-hand corner of the illustration.

Source: Friedlander catalog No. 3 Public Domain


Fluoroscopy with a cryptoscope and a partially shielded X-Ray tube

The glass bowl supporting the gas X-ray tube is an electrical insulator.

The X-ray tube in the left image is contained in a glass bowl that appears to have a partial lead shield.

Note the exposed high-voltage wiring.

Source: Tousey 1910 Textbook Illustration


Fluoroscopy with a cryptoscope and a partially shielded X-Ray tube

The operator is tracing the patient’s anatomy using live fluoroscopy as the image source.

Captions of this and other figures in the textbook recommend radiography instead of notes or sketches based on fluoroscopy for documentation.

Source: Tousey 1910 Textbook Illustration

C 1916

Fluoroscopically guided surgery (a form of fluoroscopically guided intervention)

Note the cryptoscope, unshielded X-ray tube, and exposed high voltage wiring.

Room lights appear to be on.

This may have interfered with the surgeon’s dark adaptation.

Source: Anon


WW-2 Fluoroscopic inspection of an aircraft wing

The inspector appears to be wearing radiation PPE, including a face shield built into the cryptoscope.

Based on the size of the X-ray generator housing, the inspection may have been performed in the 100 – 200 kVp range.

Source: Europe – Anon


Horizontal radiographic/fluoroscopic table

This system includes an over-table radiographic tube (with glass-radiation shielding, a collimator) and an under-table fluoroscopic tube.

The radiographic tube itself and its wiring are not shown in this image. The two poles on the left-hand side are insulators.

In use, exposed high-voltage wires ran from these points to the X-ray tubes.

The enclosure for the under-table fluoroscopic tube may have been provided to minimize stray light during fluoroscopy.   Screen fluoroscopy is performed in a dark room.

Source: Anon


Shielded and insulated R/F table

Insulated high-voltage cables replace open wiring.

The X-ray tubes used for such systems were typically shielded by lead contained within a grounded metal casing.

Improved cable flexibility finally provides electrical safety for X-Ray equipment.

Source: PICKER advertisement in RADIOLOGY


Chest fluoroscopy with little or no collimation

By this time, the fluoroscopic screen probably had a lead-glass covering providing radiation protection to the operator.

No collimation controls are evident. If collimation was not available, the beam size would have been large enough to fully illuminate the screen in any position.

Note that the screen can slide left to right.

Source: ORAU Health Physics Historical Museum


Dark Adaptation

Fluoroscopic screens could only produce a limited luminance at acceptable dose-rates. Operators dark adapted for about 30 minutes in order to fluoroscope at these low light levels.

Typically, they wore red goggles and avoided bright lights during the adaptation time.

Source: Anon


Image Intensifier Patent Drawing

This patent drawing illustrates all the essential elements of an image intensifier except for minification (the output image is the same size as the input image).

It is unlikely that this design entered routine clinical service.

Source: U.S. Patent 2,198,479


Prototype Image Intensifier (II)

This device has electronic gain but does not utilize minification (input and output are the same size)

The design may have derived from WW-2 night-vision devices.

Source: Coltman 1948

1948 (Top)

Image intensifier with minification

Minification greatly increased the brightness of the image.

Source: Coltman 1948 (Top)


c 1955

Clinical 5-inch image intensifier

Note the optical relay lens (on the right) which sent all available light from the II to the monocular viewing optic used by the system.

Source: Philips Healthcare

1956 (left), 2016 (center, right)

Mobile 5-inch image intensifier

With image intensifiers, dark adaptation and dark fluoroscopic rooms were no longer required.

Early image intensifiers had brightness gains of a few hundred times that of the brightness of the input screen. To permit operation at normal room light levels, as many of the light photons produced at the output as possible had to reach the observer’s retina. Monocular coupling was provided using optical periscopes.

Source: Philips Healthcare (left), SB (center, right)

c 1956

Image intensifier with cine camera and periscopic viewing

Single output channel for either monocular periscope fluoroscopy or cine-fluorography.

The image intensifier produced enough light to record high dose-rate images on fast photographic film.

Quantum noise was low because of the high dose-rates.

Source: Philips Healthcare

1955 (left), 1960 (right)

First generation clinical cardiac imaging fluoroscopes

The 11” II was too bulky to operate above the patient (left).

Note that a monocular viewing system was needed with this tube.

Photo of a ‘pit’ lab shows a 5” over table II with mirror optics added to the setup.

Source: Philips Healthcare

1960(Left), 1964 (Right)

Fluoroscopic mirror viewing and analog film documentation

Image intensifier gains improved sufficiently to provide an image to both eyes via a mirror.

Note the backup direct fluoroscopic screen shown on the left.

Note a radiographic spot-film device under the II shown on the left. Analog radiographic film was universally used for documentation of GI and similar procedures in this era.

Source: Philips Healthcare (left), Picker advertisement in Radiology (right)

c 1975

Video fluoroscopic viewing and analog film documentation

The operator is no longer ‘anchored’ to the image intensifier.

Everyone can now see the fluoroscopic image.

Note both cassette with film/screen and fluorographic acquisition documentation devices.

Source: Philips Healthcare (Left)


Video pickup tubes

Improvements in professional and consumer video pickup tubes were adapted for fluoroscopic cameras.

The orthicon required a great deal of maintenance and was replaced by vidicons when image quality was sufficient.

Source: ANON (left), Westinghouse ad in RADIOLOGY (right)

c 1978

Remote control system with under-table image intensifier

Remote control permits procedures with radiation shielding between the patient and operator.

Increased above-table scatter intensity may be a hazard when these systems are used with staff adjacent to the patient support.

These systems have evolved to provide both radiography and fluoroscopy with a single image receptor.

Source: Siemens Healthineers, German Post Office

c 1970

Angiographic table with a cradle to rotate the patient relative to the beam.

The cradle was used to rotate the patient into different orientations relative to a fixed vertical X-Ray beam.

The shielded table base was considered an essential element of radiation protection.

Dr. F. Mason Sones, the operator here, and in exhibit 4-21, developed coronary angiography.

Source: Philips Healthcare

1975 (left), 1995 (right)

Single and dual axis, isocentric rotating X-ray gantries

Single axis (left), dual axis (right).

Moving gantries, and the lack of metal table bases, introduced new concerns about operator irradiation.

These systems provided major improvements in patient comfort and safety by not requiring the patient to be rotated.

Source: Philips Healthcare (left), Siemens Healthineers (right)

1974 (left), 1964 (right)

Rapid film changer and its controller

Film was needed to provide anatomical coverage beyond the 9” image intensifier used in this era.

This lab has biplane changers for angiography and a separate X-ray tube/II for fluoroscopy.

Variable frame rates provided by the controller during individual sequences were used to optimize the very limited available film supply.

In-run variable frame-rate DSA is available in most modern digital fluoroscopes.

Source: St. Vincent Hospital, Worcester MA (left), Sanchez-Perez Radiology advertisement (right)


Cesium Iodide (CsI) replaces ZnCdS as the image intensifier’s input screen

Replacement of ZnCdS by CsI was a major step.

The crystal needles improved spatial resolution because of less lateral light diffusion.

The solid CsI layer improved DQE because of greater X-ray stopping power.

Source: Philips Healthcare


First Generation DSA Systems

Almost all 20th century DSA systems used analog video systems followed by A/D converters. These components were frequently the cause of image quality failures.

The initial generation of DSA used a 256 x 256 matrix because of memory size and temporal bandwidth limitations. Note the size of the electronics cabinet needed to house the image processor.

Source: Siemens Healthineers (left)
SB – NYU Hospital (right)

c 1980 (left), c 1990 (right)

High cooling rate X-Ray tubes permit spectral shaping of the X-Ray beam

High cooling rates enabled the use of copper spectral filters to better match the X-Ray spectrum to clinical targets. There is enough power to overcome the loss of photons in the filter.

The tube on the left uses radiative cooling.

The tube on the right uses conduction cooling via liquid metal bearings and an external radiator.

Source: Siemens Healthineers (left)
Philips Healthcare (right)

c 2000

Transition from analog to digital image management

Cine film processor and darkroom.

One day’s cases for one physician. Individual case images are on film, CD, and analog videotape.

In this era PACS was a shelf of films or CDs.

Source: SB – Lenox Hill Hospital, NY

c 2000

Indirect flat-panel fluoroscopic image receptors

The same CsI input layer found in image intensifiers was used for FPDs.

There was no inherent change in DQE with these detectors

Observed dose reductions are attributable to parallel changes in other fluoroscopic components and software.

Detector assembly with electronics and thermal regulators shown on right.

Source: Philips Healthcare (right)

1966 (top)

Information flow

The purpose of any imaging system is to probe the patient resulting in clinically actional information in the brain of the observer.

Fluoroscopic system development after 2010 has focused on image processing techniques intended to improve perception.

One byproduct of image processing has been radiation dose reduction.

Source: Morgan (1966) top


Global temporal recursive filtering

Left: No recursion

Center: Low recursion

Right: High recursion

Visual noise decreases and ghosts of moving objects increase with increased recursion.

Source: Siemens Healthineers


Global temporal recursive filtering with gaussian blur

Simple gaussian blur has been applied to the same image shown in Exhibit 4-35.

Source: Siemens Healthineers (Left)


Single frame local processing

Last-image-hold of a portion of a daily fluoroscopic QA phantom.

Image processor automatically adapts to local contents within the image.

Less blurring applied near lead markers and guide wires, more applied in uniform areas of the image.

Source: SB Columbia


Block diagram of some of the control elements and control loops in a fluoroscope

The operator is a key node in many fluoro control loops.

Images and radiation use displays provide real-time information.


Effect of monitor size on operator posture and irradiation

Left, 19” monitor: The operator is leaning over the patient to better see the arteries during a cine run.

Right, 60” monitor: The magnified image permits the operator to stand erect and away from the patient.

This improves both operator radiation protection and operator ergonomics.

Source: SB Columbia


A-priori, automated, and operator- controlled image processing

Image processing and analysis can use both prior knowledge and feedback from the observer, and prior knowledge from the electronic medical record.

AI in the image processor is expected to yield additional benefits.

This could reduce irradiation and increase positive clinical outcomes.


Quality assurance and fluoroscopic information flow in 2020

The for-processing, for-display, and clinical-utilization nodes could be used for quality evaluations.

Hardware level quality assurance is necessary but not sufficient to evaluate clinical utility of a fluoroscopic image.