Sanjay Kumar Saxena

Development of a new design 125I-brachytherapy seed for its application in the treatment of eye and prostate cancer

Palladium coated silver beads of 0.5mm (slashed circle) were used to adsorb (125)I and encapsulated inside a titanium capsule by Nd:YAG laser, for use as a brachytherapy source. Experimental conditions were optimized for maximum adsorption of (125)I and uniformity of radioactivity was ascertained. Leachability of (125)I was found to be<0.01%. The dose rate constant of the new source was estimated to be 1.045cGyh(-1)U(-1). This newly developed source could be an alternative to other (125)I sources.

Potential 166Ho radiopharmaceuticals for endovascular radionuclide therapy. II. Preparation and evaluation of 166Ho-DTPA.

166Ho, with its favourable radiation characteristics of t1/2 26.8 h and Eβ 1.85 and 1.75 MeV, is proposed as a suitable choice for the endovascular radionuclide therapy (EVRT) technique of liquid filled, low pressure balloon angioplasty. 166Ho was produced by the (n,γ) reaction on a natural Ho2O3 target. The specific activity obtained was ∼100 mCi·mg−1 when irradiated at a flux of 2×1013 n·cm−2s−1 for ∼7 days, and the possible contaminant 166Hom was not detected. 166Ho was easily complexed with diethylenetriaminepentaacetic acid (DTPA) at a ligand to metal molar ratio ([L] : [M]) of 1 : 1 at room temperature (22-23°C) and a reaction time of a few minutes. The radiochemical purity was >99%, as determined by paper chromatography using a mixture of pyridine, ethanol and water (1 : 2 : 4) as solvent. The complex had good stability up to 72 h at 37°C in a serum environment. In a study using Swiss mice >85% of the injected dose was cleared into the urine within 30 min post-injection, with insignificant retention in any major tissues. The studies show that the 166Ho-DTPA complex could be an alternative to the more expensive and difficult to access 188Re based products for EVRT, and provide adequate uniform radiation dose for the arterial vessel wall under treatment.

Bioevaluation studies of 32P incorporated mould brachytherapy sources for potential application in treatment of superficial tumors.

AimTo prepare 32P-based user-friendly mould brachytherpy sources for the treatment of superficial tumors. Methods32P as orthophosphoric acid was adsorbed on 15–25 mm (diameter) circular sheets of cellulose-based adsorbent paper to prepare sources containing approximately 37–74 MBq of 32P per cm2 of strip. The sources were immobilized between plastic sheets of 40 μm thickness. Autoradiography studies were carried out to determine the uniformity of 32P deposition in the source. Dosimetric evaluation of the sources was also carried out. Bioevaluation studies were carried out in C57BL6 mice bearing melanoma using 37–74 MBq sources. ResultsCellulose-based sources containing 37–74 MBq of 32P per cm2 could be prepared from which no radioactivity leakage could be detected in water or saline. Autoradiography studies revealed 32P to be uniformly distributed in these sources. Dosimetric evaluation showed that the contact dose imparted was 10 Gy/h, sufficient for treatment of superficial tumors. In mice bearing melanoma, complete tumor regression could be achieved with two applications of 37–74 MBq sources, at an interval of 3 days. Histopathological examination of the skin tissue from the treated area proved the absence of tumor as compared with the controls. ConclusionPreparation of 32P sources of various shapes and sizes (based on the tumor size) having uniform 32P activity distribution could be achieved. Efficacy of these sources in treating melanoma tumors could be established in the animal model.

Nafion–Zirconium Phosphate Composite Membrane: A New Approach to Prepare 32P Patches for Superficial Brachytherapy Applications

This article describes a method for the preparation of (32)P patch for the treatment of skin cancer. It is based on the surface modification of a Nafion film by treatment with ZrOCl(2) solution, impregnation of a predicted quantity of (32)P into the film, and its subsequent immobilization into a nonleachable matrix by lamination. The effect of variations of critical parameters on the incorporation of (32)P into the membrane, such as solution pH, contact time, reaction volume, inactive carrier concentration of the feed, reaction temperature, and so on, was investigated to arrive at the conditions resulting in optimum retention of (32)P activity. The morphology of the membrane was evaluated by scanning electron microscope and energy dispersive spectral analyses. Quality control tests were carried out to ensure nonleachability, uniform distribution of activity, and stability of the patches.

Fabrication of Cesium-137 Brachytherapy Sources Using Vitrification Technology

137Cs source in solid matrix encapsulated in stainless-steel at MBq (mCi) levels are widely used as brachytherapy sources for the treatment of carcinoma of cervix uteri. This article describes the large-scale preparation of such sources. The process of fabrication includes vitrification of 137Cs-sodium borosilicate glass, its transformation into spheres of 5-6 mm diameter, casting of glass spheres into a cylinder of 1.5 mm (varphi) x 80 mm (l) in a platinum mould, cutting of the moulds into 5-mm-long pieces, silver coating on the sources, and finally, encapsulation in stainless steel capsules. Development of safety precautions used to trap 137Cs escaping during borosilicate glass preparation is also described. The leach rates of the radioactive sources prepared by the above technology were within permissible limits, and the sources could be used for encapsulation in stainless steel capsules and supplied for brachytherapy applications. This development was aimed at promoting the potential utility of 137Cs-brachytherapy sources in the country and reducing the users reliance on imported sources. Since its development, more than 1000 such sources have been made by using 4.66 TBq(126 Ci) of 137Cs.

Dosimetry and treatment planning of Occu-Prosta I-125 seeds for intraocular lesions.

Intraocular malignant lesions are frequently encountered in clinical practice. Plaque brachytherapy represents an effective means of treatment for intraocular lesions. Recently Radiopharmaceutical Division, BARC, Mumbai, has indigenously fabricated reasonable-cost I-125 sources. Here we are presenting the preliminary experience of dosimetry of sources, configuration of treatment planning system (TPS) and quality assurance (QA) for eye plaque therapy with Occu-Prosta I-125 seeds, treated in our hospital, for a patient with ocular lesions. I-125 seeds were calibrated using well-type chamber. BrachyVision TPS was configured with Monte Carlo computed radial dose functions and anisotropy functions for I-125 sources. Dose calculated by TPS at different points in central axis and off axis was compared with manually calculated dose. Eye plaque was fabricated of 17 karat pure gold, locally. The seeds were arranged in an outer ring near the edge of the plaque and in concentric rings throughout the plaque. The sources were manually digitized on the TPS, and dose distribution was calculated in three dimensions. Measured activity using cross-calibrated well-type chamber was within ±10% of the activity specified by the supplier. Difference in TPS-calculated dose and manually calculated dose was within 5%. Treatment time calculated by TPS was in concordance with published data for similar plaque arrangement.

Development of a Spherical 125I-Brachytherapy Seed for Its Application in the Treatment of Eye and Prostate Cancer

Palladium-coated silver beads of 0.5 mm (phi) were used to adsorb (125)I, encapsulated inside a titanium capsule by an Nd:YAG laser, for use as a brachytherapy source. Experimental conditions, such as feed activity, carrier concentration, and reaction time, were optimized for the maximum adsorption of (125)I. Uniform distribution of radioactivity on the source core was ascertained by the autoradiography technique. Leachability of (125)I was found to be <0.01%. The dose-rate constant of the new source was estimated to be 1.045 cGyh(-1)U(-1). This newly developed source could be an alternative to other (125)I sources.

Studies on the development of 169Yb-brachytherapy seeds: New generation brachytherapy sources for the management of cancer

This paper describes development of (169)Yb-seeds by encapsulating 0.6-0.65 mm (ϕ) sized (169)Yb2O3 microspheres in titanium capsules. Microspheres synthesized by a sol-gel route were characterized by XRD, SEM/EDS and ICP-AES. Optimization of neutron irradiation was accomplished and (169)Yb-seeds up to 74 MBq of (169)Yb could be produced from natural Yb2O3 microspheres, which have the potential for use in prostate brachytherapy. A protocol to prepare (169)Yb-brachytherapy sources (2.96-3.7 TBq of (169)Yb) with the use of enriched targets was also formulated.

Column Chromatography Using Nano-Sorbent: A Viable Approach Towards Post-Processing Concentration of 125I for Medical Applications

Successful use of ion-exchange chromatographic technique using nano-zirconia (t-ZrO2), to concentrate 125I solution obtained from wet chemical distillation method to levels required for preparation of 125I brachytherapy sources, is reported. A careful scrutiny of the sorption parameters of t-ZrO2 was carried out and implemented to arrive at conditions resulting in optimum retention of 125I from its solution of low radioactive concentration on a tiny column containing t-ZrO2, followed by its elution in a small volume of eluent. The developed procedure was validated using samples containing varying amounts of 125I activity in the feed and the concentration factors (CF) of 125I > 5 could be obtained. The overall recovery of 125I was >90% with appropriate radiochemical purity. The compatibility of the product in the preparation of 125I brachytherapy sources was found to be satisfactory.

A novel approach to prepare 90Y–EGMP patches for superficial brachytherapy

A novel method to prepare (90)Y-EGMP patches has been developed for brachytherapy applications.EGMP films of 1cmx1cm size, incorporating approximately 185MBq of (90)Y were prepared and sealed between thin plastic sheets with uniform distribution of (90)Y. The leachability of (90)Y from radioactive patches was less than 0.01%. There was no leakage of radioactivity from radioactive patches, when tested in water or saline. The studies related to establish therapeutic efficacy of these patches are warranted.