Radioactive seeds

The radiation source used in radiation therapy may be inside or outside the body. In almost all cases, radiation therapy uses gamma radiation emitted by radioisotopes. Any alpha or beta radiation that is emitted concurrently can be blocked by appropriate packaging. For example, is often administered as seeds consisting of a core of radioactive isotope coated with 0.1 mm of platinum metal. The platinum coating stops the alpha and beta rays, but the gamma rays penetrate it readily. The radioactive seeds can be surgically implanted in a tumor. 

These advances in US imaging and robotic systems can be utilized to perform improved image-guided robot-assisted prostate brachytherapy, which may lead to more accurate and convenient ways of delivering the radioactive seeds, thus translating into improved clinical outcomes, reduced side effects, and reduced radiation exposure time. 

In general, tumor ablation can be divided into two main categories. The first one is chemical ablation, the second one is thermal ablation. Additionally, other interventional oncological therapeutic approaches have to he defined, such as the percutaneous dehvery of radioactive seeds and the transcatheter delivery of chemotherapy and chemoemho-lization. 

FIGURE 7 The position of the radioactive seeds implanted within the prostate as is seen in coronal MR images. 

Some biomedical applications Catheters, scaffolds,... Biosensors,... Surgical tools, lead bering prostheses Stents, dental implants, radioactive seeds,... 

Radon, sealed in small capsules called seeds , has been used as a radioactive substance in medicine, but is being superseded by more convenient artificially-produced radioisotopes. 

Brachytherapy A procedure in which radioactive material, sealed in needles, seeds, wires, or catheters, is placed directly into or near a tumor. Also called internal radiation, implant radiation, or interstitial radiation therapy. 

Iodine-131-labeled Lipiodol, a polyiodinated poppy seed oil which becomes particulate on dispersion in aqueous media, has been used for some time in treatment of hepatocellular carcinoma by arterial injection. This targeting approach has been coupled with the superior radioactivity properties of rhenium radioisotopes by exploiting the lipid solubility of... 

Mephosfolan. The metabolic fate of mephosfolan in cotton plants and in rice plants grown in a paddy environment was studied. Cotton plants were grown from seeds (Delta pine smooth leaf variety). Six-week-old plants containing 4 to 6 leaves were treated foliarly with C-mephosfolan. Plants were analyzed at periodic intervals. The distribution of radioactivity in cotton plants after foliar application of C-mephosfolan is summarized in Table V. The metabolic pathways of mephosfolan in cotton plants involve oxidation, hydrolysis and conjugation to yield glucosides (Figure 2). 

Radon can be isolated from radium by several methods. An aqueous solution of radium salt such as radium bromide is heated, liberating radon. Radioactive bombardment then decomposes water to oxygen and hydrogen. Radon is separated from the gaseous mixture by condensation in tiny tubes placed in liquid air. The tubes then are sealed by melting. A gold or platinum coating is applied to form the radon seeds used in radiation therapy. 

Sodium iodide is an iodine supplement in food, an expectorant, cloud seed to cause rain, and solubilizes iodine in aqueous solution for analytical work. The radioactive iodide salt of sodium, Na(I-131) is used to diagnose thyroid function. 

Approximately 2 x 105 normal and FH homozygous fibroblasts were seeded in 60 mm petri dishes and grown for 6 days in MEM containing 10% fetal bovine serum. Subsequently, the medium was removed, monolayers washed and 2 ml of fresh MEM containing 5% LPDS, 1% FCS and 2 uCi each of the above isotopes added and incubated for 48 hrs. Subsequently, medium was removed, the mono-layers washed twice with 5 ml of PBS and 2% BSA and thrice with PBS. The entire monolayer was solubilized in 1 ml of 1 N NaOH. Suitable aliquots of the cell extracts were used for protein and radioactivity measurements. 

Of great importance, for these studies, was knowledge of both pool size and turnover. This knowledge permitted calculation of the specific activity of the applied isotopically labeled compound at any desired time. Thus, radioactivity, from a labeled compound applied to the endosperm and appearing in the shoot could be translated in amounts of compound moved from seed to shoot. 

For example, it was demonstrated by such methods that phosphorus assimilated from the soil by tomato plants tends to concentrate in the stems and certain parts of the leaves. Similarly, radioactive zinc was used to show that this element localizes in the seeds of tomatoes. The rate of absorption of iodine by the thyroid gland was established by the use of radioactive iodine this and related work did much to add to the understanding of the diagnosis and treatment of goiter. These and many similar uses of radioactive isotopes show that these substances have been of inestimable value in the study of the mechanism of chemical reactions, problems relating to plant and animal metabolism, and the diagnosis and treatment of diseases. 

Scintillation vials require 1 ml medium and, although more difficult to handle in large quantities, offer the advantage that at the end of the experiment the labelled cells require fewer manipulations prior to estimation of the extent of radioactive incorporation. Alternatively several coverslips may be placed in a 5 cm plastic Petri dish prior to seeding cells. 

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