Heart disease and cancer are the biggest killers in both the UK and US. Heart disease is the cause of almost one in three American deaths each year while, in Britain, it accounts for nearly 40 per cent of the annual death toll. As for cancer, it causes around one in four deaths in the UK and US every year (Mortality Statistics: cause, England and Wales, 2002, Series DH2 no 29; National Center for Health Statistics; www.cdc.gov/ nchs/fastats/deaths.htm).
With statistics like these, it's little wonder that people undergo procedures promising early detection of these potentially fatal diseases. We are attracted to the concept of early detection because early discovery is believed to facilitate effective treatment and increase survival.
One method of early detection is the CT (computed tomography) scan, which purports to provide early warnings of cancer, heart disease and other, less serious conditions. The CT scan has been widely used as a diagnostic tool for at-risk individuals ever since its introduction in the 1970s (Internet J Radiol, 2003; 3: 1).
Recently, however, CT scanning - in particular, the full-body scan - has been hijacked by independent clinics and screening centres across the US in an aggressive marketing drive aimed at the worried well (Internet J Radiol, 2003; 3: 1). Some centres have billed the full-body scan as the 'ultimate screening miracle' while the American press has been peppered with people evangelically expounding the lifesaving merits of CT scans.
Aimed at the healthy, asymptomatic, wealthy individual, the full-body scan is lauded as the ultimate preventative measure, uncovering diseases that may be lurking undetected.
The radiation bombshell
But CT scans carry a fierce sting. Researchers have found that they expose subjects to considerable amounts of radiation.
One study found that the radiation from a single full-body CT scan corresponded to the amount of radiation linked to an increased risk of fatal cancer in atomic-bomb survivors in Hiroshima and Nagasaki (Radiology, 2004; 232: 735-8).
And, according to the Royal College of Physicians of Edinburgh, just having one CT scan of the abdomen or pelvis is the equivalent of 500 chest X-rays or four to five years of exposure to natural (background) radiation.
Nevertheless, a growing trend has emerged in countries like the US and Australia for mass full-body screening of the general public (www.behindthemedicalheadlines.com/articles/ct_scans.shtml). Companies and clinics, particularly across the US, continue to aggressively market full-body scanning - with no substantiating evidence to support any benefit from such screening.
Indeed, such is the lack of supporting clinical data for general CT screening that the US Food and Drug Administration (FDA) has declared:
"The FDA knows of no specific evidence demonstrating that whole body scanning of individuals without symptoms provides more benefit than harm to the people being screened" (www.fda.gov/cdrh/ct/ctscansbro.html). In fact, given the evidence so far, it seems more likely that CT scans may cause more harm than good, and may also be a public-health issue (Internet J Radiol, 2003; 3: 1; Radiology, 2004; 232: 735-8).
High levels of radiation are not the only drawback to systematic CT scanning. There is also the likelihood of false-positive results. These can lead to unnecessary worry or, even worse, to more invasive and higher-risk procedures (Am J Roentgenol, 2002; 179: 319-26).
In one lung-cancer CT-screening trial - the results of which remain unpublished - at least one indeterminate lung nodule was found in up to 50 per cent of all screened cases. Although it's likely that these nodules were benign, their very detection could have led to further, unnecessary and invasive tests such as a needle biopsy or thoracotomy (surgical incision of the chest wall) (Radiology, 2001; 221: 587-91).
So, instead of 'peace of mind', a full-body CT scan may uncover ill-defined abnormalities that will then require potentially high-risk follow-up procedures (Internet J Radiol, 2003; 3: 1). At worst, this could lead to overdiagnosis, where screening results in a diagnosis of cancer and leads to definitive treatment such as a lobectomy (Radiology, 2001; 221: 587-91).
On the other hand, a negative (normal) result could lead to a false sense of security and over-complacency.
Moreover, CT scans may not be as good at detecting certain cancers as they claim to be. Early-stage lung cancer can be missed, for example. In one case, the cancer was overlooked because of its similarity to a tiny granuloma (ulcerated tissue) (Radiology, 1999; 212: 61-6).
Nevertheless, most of us would leap at the opportunity to uncover an illness in its earliest stages to maximise the chances of survival and possible treatment.
But does screening have to come with such extreme health risks? Not necessarily.
One popular - and safer - alter-native technique for the early detection of certain diseases is digital infrared thermal imaging (DITI). This non-invasive, non-radioactive and painless procedure can measure skin-surface temperature changes to the very sensitive degree that they are actually reflections of deep physiological changes - in other words, the presence of disease - in the body (see www.wholisticmedical.co.uk).
The procedure involves either the direct application of liquid-crystal plates to the body or the use of ultrasensitive infrared cameras linked to a sophisticated computer (see www.iact-org.org/patients/what-is-thermography.html for more information).
Although not a diagnostic tool, DITI is an effective early-warning system for particular cancers - especially breast cancer (Cancer, 1980; 45: 51-6). Dr Shamim Daya, of the Wholistic Medical Centre in London, also finds it a valuable tool in identifying other conditions such as arthritis, heart disease, nervous-system disorders and repetitive strain injuries. According to her, DITI "is able to detect very subtle and significant changes in the body that not only allows for early intervention but can also demonstrate and monitor progress of treatments."
A number of studies support thermal imaging for the detection of breast cancer, including one that documented a 99-per-cent sensitivity rate for identifying the disease (Am J Roentgenol, 2003; 180: 263-9; Clin Obstet Gynecol, 1982; 25: 401-8; IEEE Trans Med Imaging, 1998; 17: 1019-27). This study looked at 769 cases over a four-year period, and concluded that infrared imaging is a completely safe, non-invasive way to detect breast cancer early, especially in women aged under 55 (Am J Roentgenol, 2003; 180: 263-9).
DITI has also been used to screen for dental, facial (sinus), musculoskeletal and neurological disorders. A 1988 informational report of the Council on Scientific Affairs by Dr John H. Moxley III supports the use of thermal imaging for diagnosing musculoskeletal conditions as well as autonomic nervous system and spinal disorders.
A further study has shown that thermal imaging is also a valuable tool for rheumatic (inflammatory), neurological, neonatal and vascular disorders, and for problems related to the skin, eyes and surgery (IEEE Trans Med Imaging, 1998; 17: 1019-27).
Although DITI is not yet a mainstream screening practice in either the US or UK, the fact that it is radiation-free and non-invasive make it a more attractive option for early detection of disease in the future.