The historical development of thermal imaging in medicine

Heberden Historical Series/Series Editor: M. I. V. Jayson

E. F. J. Ring

Thermal Physiology, Medical Imaging Research Group, School of Computing University of Glamorgan, Pontypridd CF37 1DL, UK.

The association between disease and human body temperature is as old as medicine itself. Hippocrates defined fever in different forms, such as malignant, benign and acute. It was claimed that if wet mud was applied to the skin, and one area dried rapidly while the remainder was still moist, that an underlying tumour may be suspected.

It was not until Gallileo Gallilei developed his simple thermoscope in 1595 that attempts to measure temperature really began, and some hundred years later before closed thermometers and calibrated scales were used. Carl Wunderlich made the greatest progress in medicine by his development of the clinical thermometer and systematically recorded the progression of temperature in a large number of sick patients in 1871 [1]. His treatise On the Temperature in Disease carries a substantial section on temperature graphs from diseased patients, some with ‘rheumatic fever’. He argued for the routine measurement of temperature and that a graphic record be established for every patient.

Following the work of Horvath and Hollander in the late 1940s [2], temperature measurements were used as a means of monitoring intra-articular steroid therapy by a number of authors. However, intra-articular temperature and isotope clearance techniques were invasive, unlike the infrared remote sensing techniques, which were available from the late 1950s.

The story of infrared radiation began in 1800, when Sir William Herschel, the astronomer, detected heating rays beyond the visible red of the spectrum. After his death in 1840, his son John Herschel made the first thermal image from sunlight using the evaporograph technique. He used the term thermogram to describe the image, which is still in common use today [3].

Early infrared imaging systems were developed during the 1940s and became available to industry and medicine first in 1959. The Pyroscan (a 1942 instrument) was first used in Bath in 1959 (Fig. 1) and was used to image the increased heat over arthritic joints. Picture quality improved with the Mark 2 instrument (Fig. 2), although each image took 3–4 minutes to acquire and was almost impossible to quantify. Later, with improved equipment, better dynamic (and objective images) were obtained that could usefully supplement radiological investigation [4].



View larger version (133K):
[in this window]
[in a new window]
 
FIG. 1. Prototype Pyroscan used in Bath in 1959.

 


View larger version (174K):
[in this window]
[in a new window]
 
FIG. 2. Early thermogram of RA knees recorded with Mark 2 Pyroscan in 1963.

 
During the 1960s and 1970s a new generation of thermal imaging systems were developed in Europe, the USA and Japan. Oscilloscope displays were introduced and electronic isotherms were added to the image. By multiple exposure colour photography, the first colour thermograms were produced in the 1960s. Mini-computers for image processing arrived in the mid- to late 1970s providing colour displays, image analysis and, importantly, data and image storage. This marked the beginning of quantitative thermography [5].

Modern systems introduced within the last three years use focal plane array detectors, with high speed images at high thermal and spatial resolution. Image quality has dramatically improved, modern digital thermograms are now very different from the crude clinical images obtained 40 years ago (Figs 3and 4).



View larger version (128K):
[in this window]
[in a new window]
 
FIG. 3. A modern thermal image of hands.

 


View larger version (161K):
[in this window]
[in a new window]
 
FIG. 4. Thermogram of knee synovitis.

 
Today, applications in rheumatology include the quantitative study of inflammation and anti-inflammatory therapies, peripheral circulatory disorders related to connective tissue diseases, and Raynaud's phenomenon, sympathetic disturbances, pain syndromes and locomotor injuries [6].

References

  1. Wunderlich C. On the temperature in disease, a manual of medical thermometry. [English translation by W. Bathurst Woodman.] London: The New Sydenham Society, 1871.
  2. Horvath SM, Hollander JL. Intra-articular temperature as a measure of joint reaction. J Clin Invest 1949;28:469–73.[ISI]
  3. Ring EFJ. The discovery of infra red radiation in 1800. Imaging Sci J 2000;48:1–8.[ISI]
  4. Collins AJ, Ring EFJ, Bacon PA, Brookshaw JD. Thermography and radiology complimentary methods for the study of inflammatory diseases. Clin Radiol 1976;27:237–43.[ISI][Medline]
  5. Ring EFJ. Thermal imaging of skin temperature. In: Serup J, Jemec G, eds. Handbook of non-invasive methods and the skin, 1995:457–71.
  6. Will RK, Ring EFJ, Clarke AK, Maddison PJ. Infrared thermography: what is its place in rheumatology in the 1990s? Br J Rheumatol 1992;31:337–44.[ISI][Medline]