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The Compton process varies slightly with the energy in this range – and is the dominating absorp- tion process for energies above 50 keV trusted elavil 75 mg. In Rayleigh scattering the photon interacts with a bound electron and is scattered without loss of energy discount elavil 50mg with mastercard. In Thomson scattering the photon interacts with a free electron and the radiation is scattered in all directions buy elavil 50 mg amex. The two elastic scattering processes accounts for less than 10 % of the interactions in the diagnostic energy range. The purpose for discussing these details about absorption and scat- tering is to give some background knowledge of the physics of the x-ray picture. It is differential attenuation of photons in the body that produces the contrast which is responsible for the information. The attenuation of the radiation in the body depends upon; the density, the atomic num- ber and the radiation quality. In mammography one are interested in visualizing small differences in soft tissue – and we use low energy x-rays (26 – 28 kV) to enhance the tissue details. In the case of chest pictures the peak energy must be larger because the absorbing body is very much larger – and some radiation must penetrate the body and reach the detector. It is the transmitted photons that reach the detector that are responsible for the picture. The detector system A number of different detectors (flm, ionization chambers, luminescence and semiconductors) have been used since the beginning of x-ray diagnostic. The x-ray picture was created when the radiation was absorbed in the flm emul- sion consisting of silver halides (AgBr as well as AgCl and AgI). In the usual morning meeting the doctors were often gath- ered in front of the “light box” to discuss the patients (see illustration). Consequently, in order to increase the sensitiv- ity, intensifying screens were introduced. The screen is usually a phosphor scintillator that converts the x-ray photons to visible light that in turn expose the flm. The introduction of intensifying screens was made already in 1896 by Thomas Alva Edison. He introduced the calcium tungstate screens which were dominating up to the 1970-ties. We do not intend to go through the technical details with regard to intensifying screens – nor to the many technological details within x-ray diagnostic. In order to ensure that the photoelec- tric effect is dominant lower energies are used. Energies lower than 30 kV are used for mammog- raphy – which is very effective for seeing details in soft tissue. However, this energy range is only useful for tissue thicknesses of a few centimeter. Mammography X-ray tube In mammography the goal is to see the contrast between different den- sity of soft tissue, fat and blood ves- sels without use of contrast media. The x-ray energy is between 25 and 30 kV in order to ensure that the photoelectric effect is dominant. This also result in absorption of ra- diation and an increase of the patient dose. Detector 181 Examples Tumor It is sometimes very convincing to see a mammogram like that shown to the right. It is also amazing that we can see details like this in soft tissue without using contrast media to enhance the difference in electron density. To the left is a modern digital picture whereas the other is a flm-based mammography. Implants Muscle It is obvious, even for the layman, that the presence of breast implants does interfere and makes it more diffcult to obtain good information with mammography. The presence of implants affects the way mammograms are done, since additional views are needed during routine screening mammography to visualize all of the breast tissue. The lesson to learn from this is that implants could be an impediment to cancer detection. Implant We can conclude that you have to be well trained to give a good de- scription. In order to re- duce the dose to the doctors the fuorescent screen was backed by lead glass. This examination (in Norway known as “gjennomlysning”) was widely used in the treatment of lung tuberculosis and pneumothorax treatment. The x-rays were con- verted to light by using phosphors (CsI:Na) – and again to photoelectrons. They were accelerated and focused on a smaller fuorescent screen which in turn is coupled to a re- corder system; for exam- ple a video camera or a flm camera. If the technique is coupled with the use of contrast media it is possible to follow the contrast when it is fowing through the blood vessels. Shoe-ftting fuoroscopy Today it is almost unbelievable that x-rays was used to fnd the right pair of shoes. However, during the period 1930 – 1950 an x-ray fuoroscope like the one shown was used. The system consisted of a vertical wooden cabinet with an opening near the bottom into which the feet were placed.
Leape cites McIntyre and Popper order elavil 10mg online, who said the “infallibility model” of medicine leads to intellectual dishonesty with a need to cover up mistakes rather than admit them effective 10 mg elavil. There are no Grand Rounds on medical errors buy discount elavil 10mg line, no sharing of failures among doctors, and no one to support them emotionally when their error harms a patient. Leape hoped his paper would encourage medical practitioners “to fundamentally change the way they think about errors and why they occur. Therefore, the iatrogenic death rate dwarfs the annual automobile accident mortality rate of 45,000 and accounts for more deaths than all other accidents combined. The survey found that more than 100 million Americans have been affected directly or indirectly by a medical mistake. Forty-two percent were affected directly and 84% personally knew of someone who had experienced a medical mistake. Leape used a 14% fatality rate to determine a medical error death rate of 180,000 in 1994. The authors learned that the American College of Surgeons estimates that surgical incident reports routinely capture only 5- 30% of adverse events. In one study, only 20% of surgical complications resulted in discussion at morbidity and mortality rounds. They also suggest that our statistics concerning mortality resulting from medical errors may be in fact be conservative figures. An article in Psychiatric Times (April 2000) outlines the stakes involved in reporting medical errors. General Accounting Office responsible for health financing and public health issues, testified before a House subcommittee hearing on medical errors that "the full magnitude of their threat to the American public is unknown” and "gathering valid and useful information about adverse events is extremely difficult. A survey of nurses found that they also fail to report medical mistakes for fear of retaliation. Pharmacology texts also will tell doctors how hard it is to separate drug side effects from disease symptoms. Treatment failure is most often attributed to the disease and not the drug or doctor. Doctors are warned, “Probably nowhere else in professional life are mistakes so easily hidden, even from ourselves. Jay Cohen, who has extensively researched adverse drug reactions, notes that because only 5% of adverse drug reactions are reported, there are in fact 5 million medication reactions each year. Dorothea Wild surveyed medical residents at a community hospital in Connecticut and found that only half were aware that the hospital had a medical error-reporting system, and that the vast majority did not use it at all. Wild adds that error reporting is the first step in locating the gaps in the medical system and fixing them. With the discovery of the “germ theory,” medical scientists convinced the public that infectious organisms were the cause of illness. Medication Errors A survey of a 1992 national pharmacy database found a total of 429,827 medication errors from 1,081 hospitals. The error rate intercepted by pharmacists in this study was 24%, making the potential minimum number of patients harmed by prescription drugs 417,908. A 2003 study followed 400 patients after discharge from a tertiary care hospital setting (requiring highly specialized skills, technology, or support services). Reuters also reported that prior research has suggested that nearly 5% of hospital admissions (over 1 million per year) are the result of drug side effects. The study found that one of the reasons for this failure is that in nearly two-thirds of the cases, doctors could not diagnose drug side effects or the side effects persisted because the doctor failed to heed the warning signs. Often, instead of gaining relief, they fall victim to the myriad iatrogenic side effects of antidepressant medication. Moreover, a whole generation of antidepressant users has been created from young people growing up on Ritalin. Medicating youth and modifying their emotions must have some impact on how they learn to deal with their feelings. As adults, these medicated youth reach for alcohol, drugs, or even street drugs to cope. Television Diagnosis To reach the widest audience possible, drug companies are no longer just targeting medical doctors with their marketing of antidepressants. By 1995, drug companies had tripled the amount of money allotted to direct advertising of prescription drugs to consumers. While the drug companies maintain that direct-to-consumer advertising is educational, Dr. Another aspect of scientific medicine that the public takes for granted is the testing of new drugs. Drugs generally are tested on individuals who are fairly healthy and not on other medications that could interfere with findings. But when these new drugs are declared “safe” and enter the drug prescription books, they are naturally going to be used by people who are on a variety of other medications and have a lot of other health problems. Then a new phase of drug testing called “post-approval” comes into play, which is the documentation of side effects once drugs hit the market. Agger reminds us that low concentrations of antibiotics are measurable in many of our foods and in various waterways around the world, much of it seeping in from animal farms. Agger contends that overuse of antibiotics results in food-borne infections resistant to antibiotics. Salmonella is found in 20% of ground meat, but the constant exposure of cattle to antibiotics has made 84% of salmonella resistant to at least one anti-salmonella antibiotic.
The simplist test is to ask participants if they knew which therapy they were getting purchase 50 mg elavil. If there is no difference in the responses between the two groups buy discount elavil 10 mg online, the blinding was successful and there is not likely to be any bias in the results due to lack of blinding purchase elavil 10mg visa. Studies of different surgical methods or operations can be done with blinding by using sham operations. This has been successfully performed and in some cases found that standard therapeutic surgical procedures were not particularly ben- eﬁcial. A recent series of studies showed that when compared to sham arthro- scopic surgery for osteoarthritis, actual arthroscopic surgery had no beneﬁt on outcomes such as pain and disability. Similar use of sham with acupuncture showed an equal degree of beneﬁt from real acupuncture and sham acupunc- ture, with both giving better results than patients treated with no acupuncture. A recent review of studies of acupuncture for low back pain found that there was a dramatic effect of blinding on the outcomes of the studies. However, when blinded studies were ana- lyzed, no such effect was found and the results, presented in Table 15. The intervention must be well described, including dose, frequency, route, precautions, and monitoring. The interven- tion also must be reasonable in terms of current practice since if the inter- vention being tested is being compared to a non-standard therapy, the results will not be generalizable. The availability, practicality, cost, invasiveness, and ease of use of the intervention will also determine the generalizability of the study. In addition, if the intervention requires special monitoring it may be too expensive and difﬁcult to carry out and therefore, impractical in most ordinary situations. Instruments and measurements should be evaluated using the techniques dis- cussed in Chapter 7. Appropriate outcome measures should be clearly stated, and their measurements should be reproducible and free of bias. Subjective outcomes don’t automatically invalidate the study and observer blinding can minimize bias from subjective outcomes. Measurements should be made in a manner that ensures consistency and maximizes objectivity in the way the results are recorded. For statistical reasons, beware of composite outcomes, subgroup analysis, and post- hoc cutoff points, which can all lead to Type I errors. The study should be clear about the method, frequency, and duration of patient follow-up. This is important because patients may leave the study for important reasons such as death, treatment complications, treatment ineffec- tiveness, or compliance issues, all of which will have implications on the appli- cation of the study to a physician’s patient population. A study attrition rate of > 20% is a rough guide to the number that may invalidate the ﬁnal results. How- ever, even a smaller percentage of patient drop-outs may affect the results of a study if not taken into consideration. The results should be analyzed with an intention-to-treat analysis or using a best case/worst case analysis. In this method, all patient outcomes are counted with the group to which the patient was originally assigned even if the patient dropped out or switched groups. This approximates real life where some patients drop out or are non-compliant for various reasons. Patients who dropped out or switched therapies must still be accounted for at the end of the trial since if their fates are unknown, it is impos- sible to accurately determine their outcomes. Some studies will attempt to use statistical models to estimate the outcomes that those patients should have had if they had completed the study, but the accuracy of this depends on the ability of the model to mimic reality. A good example of intention-to-treat analysis was in a study of survival after treatment with surgery or radiation for prostate cancer. The group randomized to radical prostatectomy surgery or complete removal of the prostate gland, did much better than the group randomized to either radiation therapy or watchful waiting with no treatment. Some patients who were initially randomized to the surgery arm of the trial were switched to the radiation or watchful waiting arm of the trial when, during the surgery, it was discovered that they had advanced and inoperable disease. These patients should have been kept in their original surgery group even though their cancerous prostates were not removed. When the study was re-analyzed using an intention-to-treat analysis, the survival in all three groups was identical. Removing those patients biased the original study results since patients with similarly advanced cancer spread were not removed from the other two groups. Remov- ing patients after randomization for reasons associated with the outcome is patently biased and grounds to invalidate the study. Leaving them in the analysis as an intention-to-treat is honest and will not inﬂate the results. However, if the outcomes of patients who left the study are not known, a best case/worst case scenario should be applied and clearly described so that the reader can deter- mine the range of effects applicable to the therapy. In the best case/worst case analysis, the results are re-analyzed considering that all patients who dropped out or crossed over had the best outcome possible or worst outcome possible. This should be done by adding the drop-outs of the intervention group to the successful patients in the intervention group and at the same time subtracting the drop-outs of the comparison group from the success- ful patients in that group. The opposite process, subtracting drop out patients from the intervention group and adding them to the comparison group, should then be done. If this range is very large, we say that the results are sensitive to small changes that Randomized clinical trials 173 could result from drop-outs or crossovers. If the range is very small, we call the results robust, as they are not likely to change drastically because of drop-outs or crossovers. Lack of compliance may inﬂuence outcomes since the reason for non-compliance may be directly related to the intervention. Other clinically important outcomes that should be measured include adverse effects, direct and indirect costs, invasiveness, and monitoring of an intervention.