Miguel A. Avila-Rodriguez

Production of [124I]-iodine on an 11 MeV cyclotron

Summary The radiohalogen, 124I, was produced by the 124Te(p,n) reaction from a glassy 124TeO2/6%Al2O3 melt on an 11 MeV proton cyclotron. A 20-degree inclined target withstands beam currents up to 20 μA with no physical damage to the substrate surface. Radioiodine was removed from the glassy melt by dry distillation techniques and trapped on cooled platinum wire. The radiochemical purity, determined by ion chromatography, shows a stable product in the iodide form over a lifetime of weeks.

18F-labeled resin microspheres as surrogates for 90Y resin microspheres used in the treatment of hepatic tumors: a radiolabeling and PET validation study

(90)Y-labeled resin microspheres (SIR-Spheres) are currently used to treat patients with primary and metastatic solid liver tumors. This treatment is typically palliative since patients have exhausted all other standard treatment options. Improving the quality of life and extending patient survival are typical benchmarks for tracking patient response. However, the current method for predicting microsphere biodistributions with (99m)Tc-labeled macroaggregated albumin (MAA) does not correlate well with patient response. This work presents the development of a new (18)F-labeled resin microsphere to serve as a surrogate for the treatment microsphere and to employ the superior resolution and sensitivity of positron emission tomography (PET). The (18)F microsphere biodistributions were determined in a rabbit using PET imaging and histological review. The PET-based uptake ratio was shown to agree with the histological findings to better than 3%. In addition, the radiolabeling process was shown to be rapid, efficient and relatively stable in vivo.

Assaying and PET Imaging of Ytrrium-90: 1>>34ppm>0

Yttrium-90 is widely used to label radiopharmaceuticals with curative, or at least palliative intent. At present, both the quantitative assay, ±10% variation, and the in vivo imaging observe bremstrahllung from the 2.3 MeV β - . Detection of the positron, which is created in the E0-decay of the 1.78 MeV excited state with a 34 ± 4 ppm branching ratio, are resolved with two detector systems. A high purity Ge spectrometer with calibrated efficiency clearly resolves the 511 keV annihilation with a 2/1 peak over the continuous bremstrahllung, providing ±5% precision in 10min of multichannel analysis. Secondly, a simple NaI detector pair in fast coincidence yields similar precision, with trues/randoms ≈ 1000/1 evident in the time spectrum and the on/off-axis counting rate. The Ge detector, more tolerant to distributed sources, was used to assay the filling of a micro-Derenzo phantom, charged with 50 MBq/ml of Y-90 chloride, imperfectly stripped from unused µ-spheres. Phantoms were scanned with a Concorde µPET P4 and a CTI 933/04. The phantoms 1.6-2.4-3.2-4.0-4.8 mm holes are clearly resolved, and particulate residue is evident as a settled deposit. The µPET sensitivity to a centered 37 MBq point source of Y-90 is ≈ 24 cps trues, 37 cps randoms and 270 kcps singles, with the 4-decade drop being the result of the miniscule positron branching. Imaging is slow, but the promise of quantitative dosimetry is essential for a rational application of Y- 90 radiotherapeutic agents.

86Y and 89Zr as PET Imaging Surrogates for 90Y: A Comparative Study

A comparative study of radioactive properties, production and microPET imaging performance issues between 86Y and 89Zr is made.