Recently a medical journal had some interesting information that I would like to share with you. The first involved a patient who suffered second degree burns from an MRI scanner. MRI scanners emit powerful radiofrequency energy, which can create heat. In this report, the patient had undergone an MRI for a skin infection of the right thigh and developed second degree (redness, pain, and blisters) burns of both inner thighs. Thermal burns are a little-known (in the lay community) potential cause of injury from MRI scanning. Most burns associated with MRIs occur in patients connected to external metal devices such as EKG leads and pulse oximeters. A much less common cause of burns can occur when the patient’s body is touching the radiofrequency coils or when the patient has skin-to-skin contact inside the scanner. Skin-to-skin contact can cause the scanner to emit high-power radiofrequency pulses that are conducted through the body, creating heat. When the patient has skin-to-skin contact it can create a closed-conducting circuit, or loop. The current flowing through this circuit creates heat and can cause burns. In this case, the patient admitted that he had moved his legs together before the scan and he was burned where his thighs touched. MRI technologists are well trained in all aspects of safety including skin-to-skin contact, but in this case the patient moved his legs after being properly positioned by the tech.
The second bit of information concerns the shingles, or herpes zoster (HZ) vaccine. Following primary infection with the varicella-zoster virus, usually in childhood, the virus remains dormant for many years in the spinal nerve roots. The reason it reactivates causing shingles is not well understood but is thought to be associated with a decline in a person’s immune system. Human immune systems decline naturally with age, with prolonged use of corticosteroids (i.e. prednisone) or other immune-suppressing medications, in persons with cancer, and with infections like HIV. Shingles in the general population occurs between three and five per thousand but rises to 13 to 15 per thousand after age 60. The varicella vaccine, which has been available for about 20 years, does not protect against shingles and shingles caused by the vaccine-strain virus do occur. In 2006 the FDA approved the use of Zostavax, a live-attenuated (weakened) strain of the varicella zoster virus manufactured by Merck. The vaccine, like all vaccines, is not 100 percent effective at preventing shingles and it does not protect against postherpetic neuralgia (PHN). PHN occurs in eight to 32 percent of people with shingles and the incidence increases with age. PHN can cause severe, persistent and debilitating pain in the area that was affected by shingles and may last from three months to as long as 10 years or longer. Zostavax is licensed for use in adults 50 and older but is approved by insurance plans only for those 60 and older. Recent research has shown that the immunity against shingles due to the vaccine is essentially gone in 10 years, and while repeat vaccination is not currently approved, it soon may be approved. So if you are 60 or over, see your doctor about getting vaccinated.
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