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

Preparation of 125I brachytherapy seeds by iodinating carbon bars with a silver coating

A method for preparing ¹²⁵I brachytherapy seeds is presented. Carbon bars were used as the substrates, on which a silver coating was deposited by electroless plating, and then, ¹²⁵I was adsorbed by iodinating the silver coating so as to prepare source cores. The radioactive cores were sealed individually in the titanium capsule to fabricate the ¹²⁵I brachytherapy seeds. Quality control checking of the encapsulated ¹²⁵I seeds for dimension, leakage and surface contamination were performed. And the ¹²⁵I seeds using carbon bar as the core substrate underwent computed tomography (CT) scan and X-ray imaging to determine the visualization. This paper provides valuable experiences and data for the preparation of ¹²⁵I brachytherapy seeds.

Combination of Permanent Interstitial 125I-Seed Brachytherapy and Surgery for the Treatment of Large Hepatocellular Carcinoma

The treatment methods available for large primary hepatocellular carcinomas (diameter >5 cm) are inadequate. Here, we report the successful management of 80 cases of large hepatocellular carcinoma, using a combination of custom-designed permanent interstitial iodine-125 seed brachytherapy and palliative surgery. Patients were enrolled in the study between 2011 and 2014. All patients underwent surgical treatment along with permanent interstitial iodine-125 seed brachytherapy; for the latter, patients received minimum doses covering 90% of the target (D90 s) of iodine-125 seeds ranging from 100 to 160 Gy (median: 110 Gy). All patients received 6 cycles of chemotherapy and were followed up at 6, 12, 24, and 36 months postoperatively. The clinical symptom remission rate was 95.3% (61 of 64). Alanine aminotransferase and aspartate aminotransferase levels decreased to normal in 80% (50 of 60) and 75% of the patients (45 of 60), respectively. The posttreatment alpha-fetoprotein levels decreased by 50% in 80% of the patients (40 of 50). The effective therapy rates were 80% (76 of 95) for 95 tumor nodules (diameters 5-10 cm) and 78.6% (33 of 42) for 42 tumor nodules (diameters >10 cm). The 3-year disease-free survival rate was 66.6%. Palliative surgery plus permanent interstitial iodine-125 seed brachytherapy appears to be a reasonable therapeutic alternative for large hepatocellular carcinoma.

Highly efficient method for production of radioactive silver seed cores for brachytherapy

A simple and highly efficient (shorter reaction time and almost no rework) method for production of iodine based radioactive silver seed cores for brachytherapy is described. The method allows almost quantitative deposition of iodine-131 on dozens of silver substrates at once, with even distribution of activity per core and insignificant amounts of liquid and solid radioactive wastes, allowing the fabrication of cheaper radioactive iodine seeds for brachytherapy.

Radiation dose to the surgeon during plaque brachytherapy

PURPOSE

To evaluate the radiation dose to a surgeon's hands during I eye plaque procedures.

METHODS

Sixteen consecutive patients with uveal melanomas were scheduled for eye plaque brachytherapy. The same surgeon wore thermoluminescent dosimeters on the dominant index finger and thumb while placing and removing the eye plaque to measure radiation dose. Additional laboratory experiments were performed to measure unobstructed (by surgical gloves or other parts of the hand) radiation exposure from a plaque.

RESULTS

Hand radiation doses during eye plaque brachytherapy are very low, but measurable, with plaques containing an average of 1.3 GBq of 125I.

CONCLUSION

Using these data, a surgeon would need to perform more than 1,000 cases each year to approach or exceed the annual regulatory radiation dose limits for the extremities.

Development of a 125I source for its application in bone densitometry

This paper describes a method for the preparation of (125)I sources for their use in bone densitometer. The process consists of preparation of silver pellets of size ∼2.5 mm (ϕ) × 0.6 mm (l) by 'Cold die compaction technique', palladium coating of the silver pellets, adsorption of (125)I on the palladium coated silver pellets and encapsulation source matrix in a titanium capsule [ 3 mm (ϕ) × 10 mm(l)] using Nd:YAG laser. The texture and morphology of the source matrix were examined by SEM and EDS analyses. Encapsulated sources containing (125)I activity up to ∼1.85 GBq (50 mCi) were prepared. Quality control tests that were necessary before application were performed and gave satisfactory results.

A dosimetry study of the Oncoseed 6711 using glass rod dosimeters and EGS5 Monte Carlo code in a geometry lacking radiation equilibrium scatter conditions

PURPOSE

The aim of this study was to develop a dose calculation method which is applicable to the interseed attenuation and the geometry lacking the equilibrium radiation scatter conditions in brachytherapy.

METHODS

The dose obtained from measurement with a radiophotoluminescent glass rod dosimeter (GRD) was compared to the dose calculated with the Monte Carlo (MC) code "EGS5," using the 125I source structure detailed in by Kennedy et al. The GRDs were irradiated with 125I Oncoseed 6711 in a human head phantom. The phantom was a cylinder made of 2 mm thick PMMA with a diameter of 18 cm and length of 16 cm. Some of the GRD positions were so close to the phantom surface that the backscatter margin was less than 5 cm, insufficient for photons.

RESULTS

The EGS5 simulations were found to reproduce the relative dose distributions as measured with the GRDs to within 25% uncertainty in the geometry lacking the equilibrium radiation scatter conditions. The absolute value of the GRD measurement agreed with the American Association of Physicist in Medicine Task Group No 43 Updated Protocol (AAPM-TG43U1) formalism to within 3% of the reference point (r = 1 cm, theta = 90 degrees), where the TG43U1 is especially reliable because of the abundant data accumulation in composing the formalism. The factor to normalize the measured or calculated dose to the TG43U1 estimate at the reference point was evaluated to be 0.97 for the GRD measurement and 1.8 for the MC calculation, which uses the integration of the apparent activity with the time as the amount of disintegration during the irradiation. Also, F(r,theta) and g(r) estimated by this calculation method were consistent with those proposed in the TG43U1.

CONCLUSIONS

The results of this investigation support the validity of both the MC calculation method and GRD measurement in this study as well as the TG-43U1 formalism. Also, this calculation is applicable to interseed attenuation and the geometry lacking the equilibrium radiation scatter.

Internal radiotherapy techniques using radiolanthanide praseodymium-142: a review of production routes, brachytherapy, unsealed source therapy

Radionuclides of rare earth elements are gaining importance as emerging therapeutic agents in nuclear medicine. β(-)-particle emitter 142Pr [T (1/2) = 19.12 h, E(-)β = 2.162 MeV (96.3%), Eγ = 1575 keV (3.7%)] is one of the praseodymium-141 (100% abundant) radioisotopes. Production routes and therapy aspects of 142Pr will be reviewed in this paper. However, 142Pr produces via 141Pr(n, γ) 142Pr reaction by irradiation in a low-fluence reactor; 142Pr cyclotron produced, could be achievable. 142Pr due to its high β(-)-emission and low specific gamma γ-emission could not only be a therapeutic radionuclide, but also a suitable radionuclide in order for biodistribution studies. Internal radiotherapy using 142Pr can be classified into two sub-categories: (1) unsealed source therapy (UST), (2) brachytherapy. UST via 142Pr-HA and 142Pr-DTPA in order for radiosynovectomy have been proposed. In addition, 142Pr Glass seeds and 142Pr microspheres have been utilized for interstitial brachytherapy of prostate cancer and intraarterial brachytherapy of arteriovenous malformation, respectively.