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医疗放射,福祸相倚

Medical Radiation Soars, With Risks Often Overlooked
医疗放射,福祸相倚

Radiation, like alcohol, is a double-edged sword. It has indisputable medical advantages: Radiation can reveal hidden problems, from broken bones and lung lesions to heart defects and tumors. And it can be used to treat and sometimes cure certain cancers.

正如酒精,医疗放射也是把双刃剑。它固然有无可争议的优势:揭露从骨折、肺部病变到肿瘤、心脏缺损等潜在问题;治疗、甚至治愈癌症。

But it also has a potentially serious medical downside: the ability to damage DNA and, 10 to 20 years later, to cause cancer. CT scans alone, which deliver 100 to 500 times the radiation associated with an ordinary X-ray and now provide three-fourths of Americans' radiation exposure, are believed to account for 1.5 percent of all cancers that occur in the United States.

但它同时亦藏有严重的安全隐患:损伤病人的DNA,在10~20年后诱发癌症。单独一项CT(Computed Tomography,计算机断层摄影)扫描,其放射性就是普通X射线的100-500倍。而CT已成为全美四分之三放射暴露(radiation exposure)的来源。据估计,美国有1.5%的癌症都因它而起。
 

Recognition of this hazard and alarm over recent increases in radiological imaging have prompted numerous experts, including some radiologists, to call for more careful consideration before ordering tests that involve radiation.

人们逐渐意识到了医疗放射的危害,对日益普遍的放射成像也开始警觉。包括放射科医师在内的众多专家呼吁,在决定用放射手段为病人做检查前请务必三思。

"All imaging has increased, but CTs account for the bulk of it," said Dr. Rebecca Smith-Bindman, a specialist in radiology and biomedical imaging at the University of California, San Francisco. "There's clearly widespread overuse. More than 10 percent of patients each year are receiving very high radiation exposures."

“所有放射成像技术都用得越来越多了,不过CT仍占绝大多数。”加州大学旧金山分校(University of California, San Francisco)放射与生物医学成像专家丽贝卡∙史密斯-宾德曼(Rebecca Smith-Bindman)医生说:“这显然是一种大范围的滥用。每年有10%以上的病人都在接受很高的放射暴露。”

The trick to using medical radiation appropriately, experts say, is to balance the potential risks against known benefits. But despite the astronomical rise in recent years in the use of radiation to obtain medical images, this balancing act is too often ignored. The consequences include unnecessary medical costs and risks to the future health of patients.

专家表示,平衡利弊才是正确运用医疗放射的关键。然而近年来,尽管利用放射技术获取医学影像的情况持续疯长,但平衡观念却往往被抛诸脑后。其结果就是耗费了不必要的医用开支,并给病人的健康埋下了隐患。

Both doctors and patients have a responsibility to better understand the benefits and risks and to consider them carefully before doctors order and patients undergo a radiation-based procedure.

医生和病人都有责任了解放射的利弊,在医生签下需要用到放射手段的诊疗单前仔细审度。

Patients may be surprised to learn that some of the newest uses of radiological imaging, including CT scans of coronary arteries to look for calcium buildup, have not yet been shown in scientifically designed clinical trials to lead to better outcomes than tests that do not involve radiation exposure, and thus their true benefits are at best a guess. Experts have estimated that widespread use of coronary artery scans, which deliver 50 to 150 times the radiation of a chest X-ray, could result in 42 additional cases of cancer for every 100,000 men who have the procedure, and 62 cases for every 100,000 women who do.

听到以下事实,病人一定会惊讶:包括CT扫描冠状动脉查找钙积聚在内的一些最新放射显影技术,还根本没用科学设计的临床试验检验过。因此它们的真正优势最多也就是个猜测。当前广泛使用的冠脉扫描,其放射量是普通X光胸透的600倍。据专家估计,每10万名接受过这类扫描的男性中会有42人、女性中将有62人因此而日后患上癌症。

For every 1,000 people undergoing a cardiac CT scan, the radiation adds one extra case of cancer to the 420 that would normally occur. This risk may seem inconsequential, but not to someone who gets a cancer that could have been prevented.

正常情况下,平均1000 人里会有420人罹患癌症;但每经过一次心脏CT扫描,这个数字就往上加1。尽管看起来风险不高,可这对于那位本来能避免癌症的人来说就太不一样了。

Complicating the matter is the enormous variation - sometimes tenfold or more - in the amounts of radiation to which patients are exposed from the same procedure at different institutions, or even at the same institution at different times.

巨大的变动性也让情况更为复杂。同样的操作,在不同医院、甚至同一医院不同时间段进行,带给患者的放射暴露竟可以有10倍以上的差异。

Although the cancer-causing effects of radiation are cumulative, no one keeps track of how much radiation patients have already been exposed to when a new imaging exam is ordered. Even when patients are asked about earlier exams, the goal is nearly always to compare new findings with old ones, not to estimate the risks of additional radiation.

虽然放射诱发癌症是个累积的过程,但没有人追究一位病人在即将接受新的显影检查时已有过多少放射暴露了。就算被问及,也是为了比较新旧结果,而非评估此次放射的危险。

As Dr. Michael S. Lauer of the National Heart, Lung and Blood Institute wrote in The New England Journal of Medicine three years ago, "The issue of radiation exposure is unlikely to come up because each procedure is considered in isolation, the risks posed by each procedure are low and seemingly unmeasurable, and any radiation-induced cancer won't appear for years and cannot easily be linked to past imaging procedures."

三年前,美国国家心肺血液研究所(National Heart, Lung and Blood Institute)的迈克尔·S·劳尔(Michael S. Lauer)医生在《新英格兰医学期刊》(The New England Journal of Medicine)上撰文称:“放射暴露带来的问题不太容易被发现,其原因是每次放射都被认为是孤立的,每一回的风险都很低、几乎无法测量,而且任何放射诱发的癌症都是多年后才浮出水面,很难与从前做过的医学成像检查联系起来。”

After an extensive review of the environmental causes and risk factors for breast cancer, the Institute of Medicine reported last year that sufficient evidence of risk was found only for combined hormone therapy used by postmenopausal women and exposure to ionizing radiation, at doses much higher than those received during a mammogram.

医学研究所(Institute of Medicine)在广泛地分析了环境及其他危险因素与乳腺癌的关系之后,在去年发布了一份报告,当中指出,唯一有足够证据证明有损健康的举措是:停经女性采用激素疗法,同时暴露在比一般乳房X光摄影剂量高得多的电离辐射中。

Everyone is exposed to a certain amount of background radiation - about three millisieverts a year from cosmic rays, radon gas and the earth's radioactive elements. By 1980, according to The Harvard Health Letter, various introduced sources, like medical tests, nuclear power plants, nuclear fallout, television sets, computer monitors, smoke detectors and airport security scanners, added another 0.5 millisieverts per year.

实际上我们每个人都处在来自宇宙射线、氡气和地球上放射性元素的背景辐射中,大约每年3毫希(millisieverts,辐射剂量单位)。根据《哈佛健康通讯》(The Harvard Health Letter)报道,至1980年,随着各种新辐射来源进入人们的生活,如医疗检测、核电站、放射性沉降物、电视机、电脑显示器、烟雾探测器以及机场安检,每年人们接受的辐射量增加了0.5毫希。

Now, however, the amount of radiation used medically rivals that of the background radiation, adding three millisieverts each year to the average person's exposure. (A mammogram involves 0.7 millisieverts, a dose that is doubled with a 3-D mammogram.)

然而如今,医疗带来的辐射已然要赶超背景辐射:平均每年在每人身上增加3毫希。(一次乳房X光摄影为0.7毫希,如果做3D显影,则剂量加倍。)

There are many reasons for this increase. Doctors in private practice who have bought imaging equipment tend to use it liberally to recoup the expense. The same goes for hospitals just a few miles apart that needlessly duplicate certain equipment so they can boast of having the latest and greatest capacity to detect disease. Doctors ordering tests suffer no adverse effects, and patients feel they are getting the most that modern medicine can offer.

这是有因可寻的。私人诊所买了昂贵的医学影像设备后为赚回成本,必须尽可能多地使用。很多大医院为了显摆自己拥有最先进高端的疾病探测仪器,即使与其他医院相距不远,也要购进同样的设备——其实全无必要。开诊疗单的医生自己当然不受辐射的影响,病人还自认为最大程度地利用了现代医学的便利。

Dr. Lauer wrote in a commentary about cardiac tests, "Most physicians who order imaging tests experience no consequences for incurring costs for procedures of unproven value. On the contrary, they or their colleagues are paid for their services, and their patients don't complain because the costs are covered by third parties. Patients are pleased to receive thorough evaluations that involve the best cutting-edge technologies."

劳尔医生写过一篇关于心脏检查的评论:“很多下单要求患者做影像检查的医师并没有因进行这些意义不明确的操作而招来什么损失;正相反,他们就靠此服务获取薪水。患者亦不会抱怨,因为费用是由第三方来承担。人们都觉得用最前沿的技术来个彻底的检查。”

According to a new study, the rise in medical imaging clearly goes beyond financial motives. Dr. Smith-Bindman and her colleagues reported in June in The Journal of the American Medical Association that a dramatic rise in imaging rates from 1996 to 2010, including a tripling of CT scans, occurred in six large prepaid health systems where the financial incentive ought to have encouraged fewer, not more, tests. The increased testing doubled the proportion of patients who received high or very high radiation exposures.

一项新的研究显示,医学成像的大量应用早已超过了原始的经济动机。史密斯-宾德曼医生及同事在6月刊的《美国医学协会杂志》(The Journal of the American Medical Association)上发表了一篇文章:1996~2010年间,6家大型预付型卫生系统的成像技术使用度飞速上涨,其中CT扫描的次数增加了两倍。然而从财政刺激的方面来讲,本应是鼓励少做,而非多做成像类检查的。这样大量地应用放射技术让接受高度甚至超高度放射暴露的病人比从前多出一倍。

By 2010, the researchers reported, 20 CT scans were performed for every 100 adult patients; for every 100 patients ages 65 to 75, about 35 CT scans were done. And among the 10 to 20 percent of children in the study who underwent a single CT scan of the head, radiation doses were in the range previously shown to triple the risk of later developing brain cancer or leukemia.

研究指出,截至2010年,每100名成年患者中就有20位接受过CT扫描;65~75岁的患者中,每100人里有35位。10~20%用前述放射剂量进行过脑CT扫描的儿童,日后患脑癌或白血病的几率增至三倍。

Dr. Smith-Bindman urged patients to participate in the decision to undergo medical imaging. She said, "Patients should ask, 'What is this test for? Do I need it? Why? Do I need it now?' "

史密斯-宾德曼医生强烈建议患者参与决定是否进行成像检查。她说:“患者都应该问问:‘这个检查的目的是什么?’‘有必要做么?’‘是刻不容缓的么?’”

Legislation can help curtail, or at least monitor, radiation doses, she said, citing a California law that took effect in July requiring that the dose used for CT scans be recorded in every patient's medical record and that inadvertent overdoses be reported to the state immediately.

“法律可以帮助减少、或至少监控放射剂量。”她说。7月开始生效的一项加州法律要求:每个病人做CT扫描时用的放射剂量都要记录在案,偶然用量过多要立刻上报州里。

If such recording were to become a national mandate, electronic medical records could help doctors and patients keep track of radiation exposures and provide further incentive to avoid unnecessary imaging.

如果类似法律能在美国推行,电子病历就可以帮医生和病人了解已接受的放射暴露,努力在日后减少不必要的成像检测。

Sidebar: Limiting the Fallout of Cancer Treatment

控制放疗辐射


Radiation therapy to treat cancer depends on much higher doses than are used in imaging, and these treatments have long been known to increase a patient's risk of later developing another cancer. Doctors consider this risk of radiation therapy reasonable when the goal is to prevent death from the original cancer.

放射性疗法治疗癌症时所用的放射剂量远高于成像检测,人们早就知道放疗会增加病人日后患另一种癌症的风险。但医生们往往认为冒这个险是值得的,因为第一要务是把病人从当前的病魔中救出来。

Last year in a report in The Lancet Oncology researchers from the National Cancer Institute and M.D. Anderson Cancer Center in Houston reported that among 647,672 adult cancer patients treated five or more years earlier, about one half of 1 percent developed a second cancer years later related to radiation treatment of the first cancer. More than half of the second cancers occurred in survivors of breast and prostate cancers.

去年,国家癌症研究所(National Cancer Institute)和休斯顿M.D.安德森癌症中心(M.D. Anderson Cancer Center)的研究人员在《柳叶刀肿瘤》(The Lancet Oncology)上发表了一篇报道:在过去的五年及以上时间里进行过癌症治疗的647672名成年病人中,约8%都因放疗而得了第二种癌症。这些人里有一半以上都曾是乳腺癌和前列腺癌的幸存者。

As expected, the risk of developing a second cancer was highest among those originally treated at younger ages and most often involved organs exposed to the highest doses of radiation.

正如所料,接受放疗的癌症病人越年轻,日后患上第二种癌症的危险越高。且第二种癌症往往与接受到最强放射的器官有关。

In recent years, radiologists have taken great pains to limit radiation exposure to nontarget organs - for example, by using a cone beam when treating breast cancer - which should reduce the risk of radiation-induced second cancers.

近年来,放射专家尽了极大努力减少非目标器官的放射暴露,比如在治疗乳腺癌时利用锥形束射线。这样做应当有助于减少由于放射而引发的第二次癌症。
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