What Is Digital Infrared Thermal Imaging?

Physical Principles

All objects at temperatures higher than absolute zero emit electromagnetic radiation. Hotter objects, e.g., the filament of a light bulb, produce radiation of wavelengths that are in the visible part of the spectrum, whereas cooler objects such as the human body, produce invisible radiation of frequencies lower than those of the red color—infrared radiation. Special cameras, however, can capture infrared radiation which is then digitally recorded and processed by complex computer programs to produce color plots of the temperature pattern on the source.

Skin temperature depends on the blood flow and has a normal predictable pattern in a healthy body. Changes to the body due to disease or injury, called lesions, cause abnormal blood flows commonly resulting in skin temperature changes of about 1.5 °C with anomalies of up to 10 °C having been observed. DITI can detect abnormalities before lesions actually appear, detect their presence once they are formed, identify their boundaries, and monitor the healing process following treatment. DITI was introduced in the 1980s but it took another 10 years of development for it to be widely accepted.

DITI is widely used for breast cancer diagnosis and follow-up.lingerie 13 image by Nathalie P from Fotolia.com

Results of a study published in 2008 in the American Journal of Surgery show that DITI successfully diagnosed breast cancer in 58 of 60 women in whom the cancer had earlier been confirmed by mammograms or ultrasounds. DITI in this study cost about $200 per test, compared to about $2000 for MRI and the cost of the equipment was about $25,000 compared to the $2 million price tag of MRI equipment. The authors concluded that DITI is particularly useful for younger women, those with surgically altered or dense breasts or men with breast cancer.

During the H1N1 outbreak in 2009, DITI was used at airports and other points of mass public transit to screen for possible carriers of H1N1. Thermal imaging cameras could detect persons with elevated body temperatures almost instantaneously, who could then for example, be examined further or quarantined. DITI scans are also used for diagnosis of rheumatism (elevated joint temperatures), Raynauds disease and nerve disorders.

DITI simply measures skin temperature, therefore, it can only indicate the possibility of a malignancy, or monitor its progress, or recovery following treatment, but it cannot confirm its presence: in the case of breast cancer, a biopsy would be necessary for confirmation. Some experts have also been sceptical of the effectiveness of mass screening such as at airports because persons being scanned do not arrive at the check point from identical thermal environments.