A colloid having a component that consists of radioactive atoms.



a colloid whose dispersed phase is made up of radioactive substances of low solubility in extremely dilute solutions. As established by the work of I. E. Starik and other investigators, radiocolloids possess a dual nature. One way of regarding radiocolloids is as ordinary colloids with solid particles (dispersed phase) consisting of molecules containing radioactive atoms. Such radiocolloids, known as true radiocolloids, arise only when the content of the radioactive substance in solution exceeds the concentration corresponding to a saturated solution. For poorly soluble substances, the saturation concentration may be very low (1010 mole/liter and lower); thus, the formation of colloid particles is possible in extremely dilute solutions.

A second way of regarding radiocolloids is as a system arising from the sorption of radioactive atoms or the ions and molecules containing these atoms on the solid ultramicroscopic particles that are usually present in water. Radiocolloids of this type, or pseudoradiocolloids, may exist in solutions of radioactive substances having concentrations both above and below the concentration of a saturated solution. The conditions necessary for forming true radiocolloids differ from those for pseudoradiocolloids, and a mixture of both types of radiocolloids is usually present in a solution.

As a result of the formation of radiocolloids, the behavior of radioactive atoms changes markedly. The atoms will no longer enter into chemical reactions or will react at very low rates. The existence of colloid particles in extremely dilute solutions depends mainly on the physicochemical properties of an element and not on the element’s radioactivity. Under analogous conditions, both radioactive and stable atoms of a given element form colloids similar in nature.


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In order to facilitate identification of SLN, blue dye was used in conjunction with radiocolloid, using the same method as in the first 30 patients.
A lymph node was recognised as an SLN when it was stained blue, had a blue afferent lymphatic and/or had a radioactive count measured by the gamma probe to be >10% of the highest count at the radiocolloid injection site.
The "very preliminary" pilot data indicate that the intraoperative combination of isosulfan blue dye and gamma probe detection of radiocolloid may be a diagnostically accurate method of detecting lymph node disease in patients with stage IB1 cervical cancer (less than 4 cm in size).
The combined use of radiocolloid and dye for SLNBX in HNSCC has been described in three reports.
In 1993, Krag and coworkers[9] reported successful localization of sentinel node in breast cancer patients with the use of radiocolloid injection and gamma probe localization; in this study, the status of the sentinel node correctly predicted the status of the rest of the axilla.
The research funded by US Military Cancer Institute, the Clinical Breast Care Project, and the Army Regional Anesthesia and Pain Management Initiative, examined standard versus pH-adjusted and lidocaine supplemented radiocolloid for patients undergoing sentinel-lymph-node mapping and biopsy for early breast cancer (PASSION-P trial).
Sentinel lymph node mapping for breast-cancer currently incorporates the use of both radiocolloid (technetium-labeled sulfur colloid) and lymphazurin blue dye injected intraparenchymally into the breast.
Lymphoscintigraphy with radiocolloid enables the surgeon to locate the hot spot in the axilla prior to making any skin incision.
Because the amount of radiocesium deposited on the leaves was so small and carrier-free, the nuclides behaved like radiocolloids or as if they were electronically adsorbed onto the tissue.
The researchers are currently trying to produce gold nanoparticles in different shapes and sizes, to label them with other radiocolloids, and to study tissue distribution of the labeled nanoparticles.