英文回答：
The carbon-14 urea breath test is a diagnostic test used to detect the presence of Helicobacter pylori (H. pylori) bacteria in the stomach. The test involves the administration of a small amount of carbon-14 labeled urea, which is a non-radioactive form of carbon. This urea is metabolized by the H. pylori bacteria in the stomach, resulting in the production of carbon dioxide (CO2) that can be detected in the breath.
The first step of the test is to fast for a specified period of time, usually overnight, to ensure an accurate result. This is because the presence of food in the stomach can interfere with the accuracy of the test. After fasting, the patient is given a small amount of carbon-14 labeled urea to swallow. The urea is quickly absorbed into the bloodstream and transported to the stomach.
Once in the stomach, the carbon-14 labeled urea is metabolized by the H. pylori bacteria.
The bacteria produce an enzyme called urease, which breaks down the urea into ammonia and carbon dioxide. The carbon dioxide is then absorbed into the bloodstream and transported to the lungs, where it is exhaled in the breath.
To measure the amount of carbon dioxide in the breath, the patient is asked to blow into a special collection bag or tube. The exhaled breath is collected and analyzed using a machine called a mass spectrometer. The mass spectrometer can detect the presence of carbon-14, which indicates the presence of H. pylori bacteria in the stomach.
The results of the carbon-14 urea breath test are usually available within a few minutes. A positive result indicates the presence of H. pylori bacteria, while a negative result suggests their absence. This test is considered to be highly accurate and reliable in diagnosing H. pylori infection.
为什么不建议年轻人做碳14 中文回答：
碳十四尿素呼气试验是一种用于检测胃中幽门螺杆菌（H. pylori）细菌存在的诊断试验。
该试验涉及到给予少量的碳十四标记的尿素，这是一种非放射性碳的形式。这种尿素被胃中的H. pylori细菌代谢，产生二氧化碳（CO2），可以在呼气中检测到。
试验的第一步是在指定的时间内进行禁食，通常是过夜，以确保准确的结果。这是因为胃中食物的存在可能会影响试验的准确性。禁食后，给患者服用少量的碳十四标记的尿素。尿素迅速被吸收进入血液并运送到胃。
一旦进入胃，碳十四标记的尿素被H. pylori细菌代谢。细菌产生一种叫做尿素酶的酶，将尿素分解为氨和二氧化碳。二氧化碳随后被吸收进入血液并运送到肺部，在呼气中排出。
为了测量呼气中的二氧化碳含量，患者被要求吹气进入一个特殊的收集袋或管子中。呼出的气体被收集起来，并使用质谱仪进行分析。质谱仪可以检测到碳十四的存在，从而表明胃中存在H. pylori细菌。
碳十四尿素呼气试验的结果通常在几分钟内得出。阳性结果表示存在H. pylori细菌，而阴性结果则表明不存在。这个试验被认为在诊断H. pylori感染方面非常准确可靠。
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