Xenon-127m: a new radionuclide for applications in nuclear medicine.

Xenon-127m (127mXe) emits two gamma rays in cascade, with half-life of 69.2 +/- 0.9 sec. The first has the energy of 172.5 keV, and is emitted from the nucleus in 38% of the decays. The second gamma ray has the energy of 124.8 keV and is emitted from the nucleus in 69% of the disintegrations. Together they furnish 107 easily collimated gamma rays per 100 decays. Xenon-127m is generated readily by bombarding nearly saturated aqueous solutions of sodium or potassium iodide with 14-MeV protons. The 127mXe is swept out continuously, as it is produced, by bubbling helium upward through the solutions. Up to approximately 100 mci/l are obtained from the resulting mixture of gases. The 127mXe + helium is admixed with about five volumes of air (or oxygen) and then driven continuously to a scintillation camera located approximately 200 yd distant. When the mixture of gases is inhaled, high quality images of the lungs are obtained by means of an Anger scintillation camera.

Krypton-79m: a new radionuclide for applications in nuclear medicine.

Krypton-79m emits 130-keV gamma rays in 27 +/- 1% of its disintegrations and decays with a half-life of 50 +/- 3 sec. It is generated readily by bombarding nearly saturated aqueous solutions of bromide salts, or bromoform, with 14-MeV protons. The 79mKr is swept out continuously as it is produced by bubbling helium upward through the liquids. Up to 200 mCi per I are obtained of the resulting mixture of gases. The 79mKr + helium is mixed with about five volumes of air and then driven continuously through a small-bore tube to an Anger scintillation camera located approximately 200 yards away. The rate of flow is adjusted so that the amounts of 13-sec 81mKr and of 35-hr 79Kr are inconsequential at the time and point of use. When the gases are inhaled, good images of the lungs are obtained with an Anger scintillation camera. The trachea and bronchi commonly are revealed also.

Production of 7.6-minute potassium-38 for medical use.

A method is described for generating 20--30 mCi of 7.6-min potassium-38 by means of a small cyclotron. Sodium chloride is mounted on a water-cooled tantalum plate, by evaporation from an aqueous solution. It is bombarded with 14.7 MeV helium-4 ions, at 50 microA. The K-38 is produced free of other radionuclides. For intravenous injection the bombarded NaCl is dissolved in sufficient pyrogen-free water to make an isotonic saline solution, which then is sterilized by filtration. Other methods of production investigated were the bombardment of: carbon tetrachloride with He-4 ions; calcium oxide with 7.8-MeV deuterons; and potassium chloride with 23-MeV He-3 ions. These gave products that were unsuitable for clinical applications. Chiefly because of the short half-life of K-38, the whole-body radiation exposure is estimated to be only about 12 mrad/mCi, and exposures to the heart and kidneys are approximately ten times greater.

The passage of Florida's Statute on Assisted Reproductive Technology.

Until 1993, there were no statutes in the United States covering gestational surrogacy contracts, disposition of stored embryos and gametes, parentage of children born from donated gametes and embryos, and the inheritance rights of cryopreserved embryos of deceased donors. In March 1993, the Florida Assisted Reproductive Technology Act was passed to address some of these issues and to minimize the expense and emotional cost of related courtroom proceedings. Authors of the bill believed that motherhood of a newborn in the eyes of the law should be determined by two factors: genetic inheritance and the original intent of the woman to become the parent of record. The bill included the assumption that, in the cases of children born of gestational surrogacy, the commissioning genetic parents would be the "natural parents" of the child. Some of the reasons for legislative success of the statute include: 1) clear need for statutory guidance in cases involving reproductive technology, 2) relevance of the issue to cost containment (ie, judicial costs) in an era of health care reform, 3) careful use of scientific terminology and the support of the medical community, 4) involvement of a skilled legislative team, 5) participation of physician specialists in the development of the bill (ie, practicing gynecologists in assisted reproductive technology programs), 6) participation of the State of Florida legislative staff, and 7) consultation with appropriate lobbying groups (eg, Florida Catholic Conference). The successful legislative process that was followed to achieve passage of this bill can serve as an example for other states to emulate.

PET tomography in studies of distributions of 7.6-min potassium 38 in the dog heart.

Potassium 38 emits a 2.68-MeV (max) positron, followed promptly by a 2.17-MeV gamma-ray in 99.8% of its disintegrations. A positron is emitted also, followed by a 3.94-MeV gamma-ray, in 0.2% of the decays. The pairs of 511-keV PET +/- gamma-quanta, which are emitted at 180 +/- 0.3 degrees to each other, are in true coincidence with the prompt gamma-rays emitted by the daughter nucleus, within the resolving time of PET instrumentation. Studies made with phantoms by means of a commercial version of the MGH PET camera demonstrated that quantitatively satisfactory images are derived, despite the presence of the prompt gamma-rays. Two-dimensional (2-D) focal-plane images reveal high uptake of 38K promptly in the myocardium of dogs, under barbiturate sedation. Third-dimensional (3-D) transverse section PET tomographic images, through four 1.0-cm-thick heart "slices" orthogonal to the plane of the 2-D images and with 1.4-cm sequential spacing, show 38K uptake to be concentrated especially highly in the left ventricle, as expected. Peak levels of activity were observed over the myocardium at 12 s after intravenous bolus injection of ionic 38K. Dynamic mode 2-D images were taken at intervals as short as 0.5 s and extending to 1 h.

PET tomographic imaging of the human heart, pancreas, and liver with nitrogen-13 derived from [13N]-L-glutamate.

The first commercial version of the Massachusetts General Hospital (MGH) positron camera was used to image the relative distributions of 13N (T1/2 = 9.96 min) in the human heart, pancreas, and liver after intravenous administration of [13N]-L-glutamate. The instrument was operated in two imaging modes. Conventional 2-dimensional (2-D) focal-plane images showed high concentrations of 13N in the heart and pancreas, and lower levels in the liver. Five PET tomographic transverse section (3-D) images were made through the heart and three through the pancreas. Our results suggest that further studies designed to gain an improved understanding of the biochemistry of [13N]-L-glutamate aided by PET imaging, especially with newer instrumentation, are worthy of further investigation.