In 1995, Goffman completed a study on the etiology of breast cancer. The results showed that of the 180,000 cases of breast cancer diagnosed each year, about 2/3 were related to medical X-rays. In a more recent survey, in addition to "all types of cancer" and breast cancer, Goffman focused on cancers of the digestive, respiratory, urinary and reproductive systems. He found that only cancers of the female reproductive system were not directly linked to medical radiation.
These findings not only confirm the relationship between medical radiation and common terminal illnesses, but also send a cheering message that reducing medical radiation can prevent the induction of cancer and heart disease. Over the past 20 years, people have also figured out a number of ways to minimize X-ray exposure while ensuring the effectiveness of treatment.
Ionizing Radiation Woes and Fortunes
Electromagnetic radiation is the process of spreading energy in the form of beams of photons. According to the order of increasing energy, photon beams can be divided into radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. The latter three types of photon beams have sufficient energy to collide with electrons when they meet atoms or molecules, i.e., ionizing radiation occurs. However, only X-rays and gamma rays can penetrate the internal organs of the human body.
The "medical X-rays" in the Koch study refer specifically to X-rays used for medical diagnostics, i.e., X-rays used in different medical procedures such as dental exams, fluoroscopy, CT scans, orthopedic bone setting, foreign body finding, catheter and needle placement, and surgical guidance, and exclude X-rays used for the treatment of cancer. The latter increase the dose of irradiation in order to kill cancer cells.
The damage done to cells by medical X-rays does not come directly from the X-ray photons, but from the high-energy electrons released during the movement of the photons. The electrons, in the course of their motion, transfer some of their energy to the biomolecules in an erratic manner, leading to what Goffman calls "chemical and biological damage". For example, the source electron causes other electrons to escape from the molecule, creating a jet of electrons. This puts the molecule in a high-energy state, resulting in a chemical reaction that is only possible under ionized X-ray conditions.
This damage can have undesirable consequences, such as killing cells, destroying the internal structure of cells, or causing mutations - lifelong damage to genetic molecules that is difficult to repair. Suppose that the energy of an X-ray does have this effect? smoked then there is no such thing as a safe or acceptable dose of ionizing radiation. Moreover, the damage caused by continuous X-ray exposure is cumulative and much more harmful. At the same time, the body itself is not omnipotent with respect to the damage caused by X-rays, although it has a better repair function.
Cells damaged by X-rays are prone to mutations. Numerous epidemiologic analyses have repeatedly demonstrated that these cells are also the "root cause" of almost all types of cancer. However, Edward Radford, Chairman of the US National Research Advisory Board, is not convinced. After investigating the biological effects of ionizing radiation, he concluded that it was too early to characterize these altered cells as the culprits of every type of cancer known to man.
Dose-response: a correlation analysis
It is well known that there are many other factors that contribute to cancer, such as smoking or poor nutrition. After having formulated the hypothesis that "medical radiation induces many types of cancer", Goffman had to determine the so-called "cause fraction" (or cause percentage) in order to prove it.
Both cancer and coronary heart disease are induced by multiple etiologic factors. These factors **** work together to cause the onset of these terminal illnesses. Among them, the necessary factors play a major role in the progression of the disease. As an example, if medical X-rays are a necessary factor in 75% of cancer deaths, then the cause score is 75%. In other words, medical X-rays cause 75% of cancer deaths.
Calculating the cause fraction reveals the dose-response ratio. Where dose refers to the amount of medical X-ray exposure and response refers to cancer mortality. (Note: "Response" here refers specifically to the death rate, not the number of deaths.) Gow's analysis is extremely simple on the surface. First, he obtained information on the response (age-specific cancer mortality rates) for each of the nine major census tracts in the United States from data published by the U.S. government. He has data on the number of cancer deaths per 100,000 population by sex, the number of cancer deaths in different parts of the body, and selectively on a number of other causes of death.
The next step was to create a database of X-ray doses, which had to overcome difficulties caused by many uncertainties. Recently, U.S. officials released statistics on the subject and acknowledged that X-ray doses used for medical diagnosis over the years may be 60 percent lower than is now believed. In addition, the average radiation dose per operation varies considerably from one device to another, which is also an influencing factor; and dose data from decades ago are even more difficult to ascertain. These uncertainties add up to a statistically significant bias in the "average rad risk" (the mortality rate per rad unit).
Goffman, on the other hand, came up with a basic assumption, which he rigorously scrutinized, and which solved the problem. The assumption is that the more physicians per 100,000 population, the more radiation examinations (doses) are performed. This assumption is in line with common sense and has been confirmed by the assessment studies carried out globally by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). It has been further confirmed by other sources, such as the ratio of medical X-ray film sales to the number of doctors per 100,000 population.
Thus, in the absence of absolute numbers for dose, Goffman utilized data on the number of physicians per 100,000 population to characterize the dose associated with the nine census divisions. Fortunately, the numbers vary relatively widely from place to place. And that's crucial, because it's the existence of differences in dose that makes dose-response analysis meaningful. If the dose data were exactly the same in each region, it would be impossible to conclude that medical radiation is the cause of cancer. As the analysis progressed, another statistical requirement was met: that the dose data from the nine subregions be relatively stable over a long time span.
Once the reaction and dose data were available, Goffman had to test them and figure out the interrelationships to prove or disprove his hypothesis that "medical X-rays are the leading cause of cancer deaths in the United States". To do this, regression analysis in statistics plays an important role. This method can be used to calculate a curve that shows the dose-response ratio. One can further determine the fraction of X-rays that are the cause of cancer deaths by bringing the dose value to zero. When the dose value is zero, the corresponding response value is the mortality rate from cancer not induced by medical X-ray exposure, i.e., the non-radiation cancer mortality rate (set to N). The non-radiation cancer mortality rate (set to T) is then subtracted from the total cancer mortality rate (set to T), and the difference is divided by the total cancer mortality rate, resulting in the cause fraction we need: (T-N)/T.
Analyzing the results, Gao arrived at a higher percentage of cause fractions, thus confirming his hypothesis that medical X-rays are the scourge of cancer in the United States.
Heart disease also stems from X-rays
In a narrow sense, this is where the research ends. But, as a thoughtful scholar, it was necessary to look further into the link between radiation and non-cancer patients. As expected, he found that non-malignant tumors behaved quite differently from malignant tumors in terms of responding to medical radiation. Coronary heart disease mortality, on the other hand, showed an unexpectedly strong relationship with radiation.
There is a basic idea in science that correlation is not the same as causation. The strikingly similar responses between cancer and coronary heart disease and medical X-rays urgently need to be systematically accounted for. Some researchers had put forward the view that mutagens (or mutagenic factors) cause small tumors to form on the smooth muscle of coronary arteries, and that's where Goffman started. This hypothesis fits quite well with what it reveals about the apparent dose-response ratio between coronary heart disease and medical radiation (as a proven mutagen).
Of course, studies have shown that there are many other factors that trigger coronary heart disease. Goffman himself has studied this for many years. Limited to space, he did not elaborate, but only pointed out that small tumors on the coronary arteries and poor lipoprotein content, hypertension, smoking, obesity and body dysfunction, diabetes mellitus, nutritional deficiencies, and other factors, as highly susceptible to induced disease.
Gaufman emphasized, on the one hand, that it is indisputable that there is a clear dose-response ratio between medical X-rays and coronary artery disease, and, on the other hand, acknowledged that the research "still needs to go further". But an important first step has been taken, and the stage is set for future heart disease prevention and improved treatment.
X-rays still have their place
Although X-rays are a major cause of cancer and coronary heart disease, they are still vital to human health. One should minimize radiation doses without sacrificing these uses of X-rays. After Goffman published the results of his breast cancer research, some people disagreed: the radiation dose had long been reduced, and Goffman's conclusions were unconvincing. On the one hand, the use of X-rays has been greatly reduced or even eliminated; on the other hand, other means have taken their place. For example, many hospitals have switched to the extensive use of CT scans, which, according to the UNSCEAR study, deliver 10 times the radiation dose of "traditional" diagnostic tests.
Thankfully, it's not impossible to make X-rays work better than they already do, and a 1998 UNSCEAR report cited a number of new technologies that can both reduce radiation dose and enhance X-ray imaging, such as the use of rare-earth screens and carbon-based fibers, and increased voltage limits. Each of these techniques reduces the amount of radiation by a little bit, and the effect is even more pronounced when used in combination.
The patient, as the recipient of the treatment, should confide in his or her doctor his or her concerns about the required radiation dose, exercise his or her right to know how to reduce the dose, and cooperate with the medical staff to improve the effectiveness of the treatment