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    It is often important for doctors to know how much water there is in a patient's body, especially if he has heart disease. Almost 20 years ago, Physicist George Hevesy worked out a way to use the stable isotope of hydrogen (deuterium or hydrogen-2) in heavy water for this purpose. But the technique is complicated and takes a long time. Now the University of California's Dr. John H. Lawrence, one of the first and most imaginative of the atomic medicine men, can do the job far faster with heavy-heavy water, the oxide of hydrogen3 or tritium.-The radiant atoms of tritium reveal themselves (to the Geiger or scintillation counter); from the dilution of tritium oxide, it is a simple matter to calculate the total amount of water in the body.

    Facts for the Surgeon. No less important is the mass of red blood cells in the body. Some researchers hold that the "count" of red cells in a droplet of blood is not precise enough. Lawrence now gets a more accurate estimate by tagging the red cells with phosphorus. Then there is the question of blood volume; a surgeon needs to know how much blood may have been lost by injury before he undertakes an amputation, and then how much is lost during the operation. With iodine-131 or phosphorus-32 and a Geiger counter this too, is relatively easy. _ One of the most difficult problems facing cancer specialists and brain surgeons is the diagnosis and location of brain tumors. Now a team of doctors claims to have reached 95% accuracy in pinning down the tumor site with the aid of a dye tagged with iodine-131. Other doctors have not been able to get as good results so the search goes on. Boston's Dr. Abraham S. Freedberg is encouraged by the way radioactive rubidium (a rare trace element in the body) concentrates in the tumor more than in healthy brain tissue making the cancer easier to spot.

    Paths for Pioneers. The medical pioneers, advancing behind thick lead shields and armed with radiation counters, are striking out along two main paths: i) experiments in actual treatment, where the benefit _of new discoveries may be felt by the patient tomorrow, and 2) fundamental research into the most deeply hidden details of the chemistry of the body and its every cell—the results of which may not be apparent for years. Prime examples of experimental treatments:

    51 Bone cancers are hard to treat because if radioactive elements (such as calcium and phosphorus) settle in hard bone, they also affect the marrow and damage the blood-making cells. At Oak Ridge, doctors and radiologists have just eliminated gallium7 2 as unsuitable for treatment, largely because it takes too long to settle in the bone (and meanwhile loses most of its radioactivity). Next on their list is gallium-67.

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