Effects of Preloading of Stannous Compounds on the Distribution of 99mTc-Pertechnetate

99mTc-pertechnetate distribution studies were performed in rabbits and mice following pretreatment between 5—336 hours with various routinely used stannous complexes (HSA, MAA, GHT, DTPA, PYPs) containing different amounts of Sn++ (0.17 —15.0 μ mg/kg). Beyond a concentration of 0.26 mg/kg of Sn++ an alteration in 99mTc-pertechnetate distribution was observed. The red blood cell was found to be the most prominent target. An in-vivo reduction of 99mTc-pertechnetate apparently occurred by the presence of stannous ion within the red blood cell. Preloading time period between 5—24 hours did not alter the uptake of RBC/plasma ratio. Beyond that period it decreased slowly and still persisted up to 2 weeks following pretreatment. RBC/ plasma ratio of 99mTcO4 - increased with increased Sn++ content of various commercially available pharmaceutical kits.

Biochemical effects of two different hyaluronic acid products in a co-culture model of osteoarthritis

OBJECTIVES

To compare the effects of two hyaluronic acid (HA) formulations on mediators of matrix turnover and inflammation in an IL-1-treated cartilage-synovium co-culture model with the aim of elucidating mechanisms by which viscosupplementation exerts beneficial effects in osteoarthritic joints.

DESIGN

A co-culture model (100 ng/ml interleukin-1beta (IL-1beta) added to canine synovial and cartilage explants) was used to investigate the effects of HA on cartilage-synovium interactions. Three concentrations (1x, 0.5x, and 0.1x) of two commercial sources of HA (A: Synvisc [hylan G-F 20]; B: Hyalgan [sodium hyaluronate]) were used. Co-cultures without IL-1beta (negative) or with IL-1beta (positive) but neither HA product served as controls. The liquid media were collected every 3 days and explants of cartilage and synovium were collected on days 3, 6, and 20. Media and explants were analyzed histologically, biochemically, and immunohistochemically.

RESULTS

Glycosaminoglycan (GAG) content was measured in cartilage explants. GAG content in explants was higher in both HA groups at the beginning and the conclusion of the study compared to the IL-1beta-treated group. GAG content of the media was significantly (P<0.05) lower in the Synvisc group than all other groups early. The Hyalgan group demonstrated progressively less GAG release later in the study. The addition of Synvisc did not decrease the matrix metalloproteinase (MMP)-3 concentrations at any point. MMP-3 concentrations were significantly (P<0.05) lower among the 1x and 0.5x Hyalgan groups on day 20 compared to the IL-1beta-treated group. On day 3, prostaglandin E(2) concentrations were significantly (P<0.05) higher in the IL-1beta-treated group compared to other groups. Both HA groups had less nitric oxide production than the control groups throughout the study.

CONCLUSIONS

This study supports two potential mechanisms for viscosupplementation: a biosynthetic-chondroprotective mechanism, with a possible delay in onset depending on the form of HA; and an anti-inflammatory mechanism.

An improved neutron collimator for brain tumor irradiations in clinical boron neutron capture therapy

To improve beam penetration into a head allowing the treatment of deeper seated tumors, two neutron collimators were built sequentially and tested for use in the clinical boron neutron capture therapy (BNCT) program at the epithermal neutron irradiation facility of the Brookhaven Medical Research Reactor. The collimators were constructed from lithium-impregnated polyethylene, which comprises Li2CO3 powder (approximately 93% enriched isotopic 6Li) uniformly dispersed in polyethylene to a total 6Li content of 7.0 wt. %. The first collimator is 7.6 cm thick with a conical cavity 16 cm in diameter on the reactor core side tapering to 8 cm facing the patient's head. The second collimator is 15.2 cm thick with a conical cavity 20 cm in diameter tapering to 12 cm. A clinical trial of BNCT for patients with malignant brain tumors is underway using the first collimator. Results of phantom dosimetry and Monte Carlo computations indicate that the new 15.2 cm thick collimator will improve the neutron beam penetration. Thus, the second collimator was made and will be used in an upcoming clinical trial. In-air and in-phantom mixed-field dosimetric measurements were compared to Monte Carlo computations for both collimators. The deeper penetration is achieved but at a sacrifice in beam intensity. In this report, a performance comparison of both collimators regarding various fluence rate and absorbed dose distributions in a head model is presented and discussed.

Physical and biological doses produced from neutron capture in a 235U foil

As a follow-on study to the feasibility of neutron capture therapy (NCT) with 235U brachytherapy seeds, physical doses were calculated and measured for the radiation from a 235U foil in a lucite phantom which was irradiated at the epithermal neutron irradiation port of the Brookhaven Medical Research Reactor. In addition, cell survival experiments were performed to obtain the relative biological effectiveness (RBE) for the neutron part of the radiation. The calculated absorbed doses agree with the measured ones. From cell survival experiments, it is deduced that the fission neutrons from the 235U foil have a RBE of 3.0 while the fast neutrons in the beam have a RBE of 3.8. Also observed is that, with the cells 7 mm from the foil, a significant amount of absorbed dose comes from the beta rays of 235U fission events. This absorbed dose from beta rays is a significant addition to the therapeutic dose. Due to the limited ranges of beta rays in tissue, this absorbed dose is restricted to the vicinity of the foil. This is the first demonstration of beta rays as part of NCT.

Enhancement of the epithermal neutron beam used for boron neutron capture therapy

PURPOSE

This report describes a study to enhance the epithermal neutron beam at the Brookhaven Medical Research Reactor by increasing the epithermal neutron flux and/or reducing contamination by fast neutrons.

METHODS AND MATERIALS

The beam was reevaluated using Monte Carlo calculations and flux and dose measurements in air and in an ellipsoidal head phantom at the patient irradiation port. Changes in its geometry and materials were considered, including rearranging the fuel elements in the reactor core and redesigning the moderator and the patient irradiation port.

RESULTS

Calculations of the new fluxes and doses at the patient irradiation port showed that the epithermal neutron flux can be increased by 100%, while the fast neutron dose per epithermal neutron can be reduced by 38%. In 1992, some of the proposed changes were made. In June 1992, measurements were made after one additional fuel element was added to replace a graphite spacer block on the epithermal beam side of the reactor core. The results show that the epithermal neutron flux increased by 18%, as predicted by the Monte Carlo calculations. In October 1992, the fuel elements in the reactor core were rearranged by placing four new fuel elements in the first row facing the epithermal port; the intensity of the epithermal neutron beam increased by 50% and the fast neutron and gamma doses per epithermal neutron may have decreased slightly.

CONCLUSION

The epithermal neutron beam at the Brookhaven Medical Research Reactor has gained a 50% increase in the epithermal neutron flux and the fast neutron and gamma doses per epithermal neutron are reduced slightly after the rearrangement of the fuel elements in the core.

Microautoradiographic studies on the cellular localization of radiothallium

201Tl-chloride and 204Tl-nitrate were similarly distributed in organs of mice 10 min and 60 min after intravenous injection. Autoradiographic studies were carried out with 204Tl-nitrate in rats (injected intraperitoneally) as well as in mice and dogs (injected intravenously). Thallium localized in the cells of proximal and distal convoluted tubules and collecting tubules of the kidney. In the intestines, it was distributed mostly in the cells of the smooth musculature and surface epithelium of the villi. Some silver grains were seen in the goblet cells and in the lumen as well. It localized in the sarcoplasm of the myocardium and the skeletal muscle cells. In thyroid, most of the thallium was seen in the colloidal part of the follicle. In testes, silver grains were seen in and around the cells of Sertoli and in the lumen of the seminiferous tubules. Some localized concentration in the interstitial cells of the testes was also observed.

Effects of preloading of stannous compounds on the distribution of 99mTc-pertechnetate

99MTc-pertechnetate distribution studies were performed in rabbits and mice following pretreatment between 5--336 hours with various routinely used stannous complexes (HSA, MAA, GHT, DTPA, PYPs) containing different amounts of Sn++ (0.17--15.0 mu mg/kg). Beyond a concentration of 0.26 mu mg/kg of Sn++ an alteration in 99mTc-ertechnetate distribution was observed. The red blood cell was found to be the most prominent target. An in-vivo reduction of 99mTc-pertechnetate apparently occurred by the presence of stannous ion within the red blood cell. Preloading time period between 5--24 hours did not alter the uptake of RBC/plasma ratio. Beyond that period it decreased slowly and still persisted up to 2 weeks following pretreatment. RBC/plasma ratio of 99mTcO4-increased with increased Sn++ content of various commercially available pharmaceutical kits.