Equilibration and disequilibration between monazite and garnet: indication from phase-composition and quantitative texture analysis

The integration of information which can be gained from accessory [i.e. age (t)] and rock-forming minerals [i.e. temperature (T) and pressure (P)] requires a more profound understanding of the equilibration kinetics during metamorphic processes. This paper presents an approach comparing conventional P-T estimate from equilibrated assemblages of rock-forming minerals with temperature data derived from yttrium-garnet-monazite (YGM) and yttrium-garnet-xenotime (YGX) geothermometry. Such a comparison provides an initial indication on differences between equilibration of major and trace elements. Regarding this purpose, two migmatites, two polycyclic and one monocyclic gneiss from the Central Alps (Switzerland, northern Italy) were investigated. While the polycyclic samples exhibit trace-element equilibration between monazite and garnet grains assigned to the same metamorphic event, there are relics of monazite and garnet obviously surviving independent of their textural position. These observations suggest that surface processes dominate transport processes during equilibration of those samples. The monocyclic gneiss, on the contrary, displays rare isolated monazite with equilibration of all elements, despite comparably large transport distances. With a nearly linear crystal-size distribution of the garnet grain population, growth kinetics, related to the major elements, were likely surface-controlled in this sample. In contrast to these completely equilibrated examples, the migmatites indicate disequilibrium between garnet and monazite with a change in REE patterns on garnet transects. The cause for this disequilibrium may be related to a potential disequilibrium initiated by a changing bulk chemistry during melt segregation. While migmatite environments are expected to support high transport rates (i.e. high temperatures and melt presence), the evolution of equilibration in migmatites is additionaly related to change in chemistry. As a key finding, surface-controlled equilibration kinetics seem to dominate transport-controlled processes in the investigated samples. This may be decisive information towards the understanding of age data derived from monazite.

Phase III trial of consolidation therapy with yttrium-90-ibritumomab tiuxetan compared with no additional therapy after first remission in advanced follicular lymphoma.

PURPOSE: We conducted an international, randomized, phase III trial to evaluate the efficacy and safety of consolidation with yttrium-90 ((90)Y)-ibritumomab tiuxetan in patients with advanced-stage follicular lymphoma in first remission. PATIENTS AND METHODS: Patients with CD20(+) stage III or IV follicular lymphoma, who achieved a complete response (CR)/unconfirmed CR (CRu) or partial response (PR) after first-line induction treatment, were randomly assigned to receive (90)Y-ibritumomab tiuxetan (rituximab 250 mg/m(2) on day -7 and day 0 followed on day 0 by (90)Y-ibritumomab tiuxetan 14.8 MBq/kg; maximum of 1,184 MBq) or no further treatment (control). The primary end point was progression-free survival (PFS), which was calculated from the time of random assignment. RESULTS: A total of 414 patients (consolidation, n = 208; control, n = 206) were enrolled at 77 centers. (90)Y-ibritumomab tiuxetan consolidation significantly prolonged median PFS (after a median observation time of 3.5 years) in all patients (36.5 v 13.3 months in control arm; hazard ratio [HR] = 0.465; P < .0001) and regardless of whether patients achieved PR (29.3 v 6.2 months in control arm; HR = 0.304; P < .0001) or CR/CRu (53.9 v 29.5 months in control arm; HR = 0.613; P = .0154) after induction treatment. Median PFS with consolidation was prolonged in all Follicular Lymphoma International Prognostic Index risk subgroups. After (90)Y-ibritumomab tiuxetan consolidation, 77% of patients in PR after induction converted to CR/CRu, resulting in a final CR rate of 87%. The most common toxicity with (90)Y-ibritumomab tiuxetan was hematologic, and grade 3 or 4 infections occurred in 8% of patients. CONCLUSION: Consolidation of first remission with (90)Y-ibritumomab tiuxetan in advanced-stage follicular lymphoma is highly effective with no unexpected toxicities, prolonging PFS by 2 years and resulting in high PR-to-CR conversion rates regardless of type of first-line induction treatment.

Radiolabeling of monoclonal antibody against carcinoembryonic antigen with 88Y and biodistribution studies.

The biodistribution of the 202 monoclonal antibody against CEA labeled with 88Y by the bicyclic DTPA anhydride method was studied in normal Balb/c mice. The in vitro binding to 1 X 10(7) CO112, LS174T and WiDR colon cancer cells was 21.0, 27.3 and 18.8%, respectively. The binding to an equal number of KM-3 leukemia cells and normal human lymphocytes was 8.9 and 3.2%, respectively. Liver, spleen, kidney and blood were the tissues that showed the highest uptake of radiolabeled antibody in vivo.

Activity measurements of 18F and 90Y with commercial radionuclide calibrators for nuclear medicine in Switzerland.

The activity of radiopharmaceuticals in nuclear medicine is measured before patient injection with radionuclide calibrators. In Switzerland, the general requirements for quality controls are defined in a federal ordinance and a directive of the Federal Office of Metrology (METAS) which require each instrument to be verified. A set of three gamma sources (Co-57, Cs-137 and Co-60) is used to verify the response of radionuclide calibrators in the gamma energy range of their use. A beta source, a mixture of (90)Sr and (90)Y in secular equilibrium, is used as well. Manufacturers are responsible for the calibration factors. The main goal of the study was to monitor the validity of the calibration factors by using two sources: a (90)Sr/(90)Y source and a (18)F source. The three types of commercial radionuclide calibrators tested do not have a calibration factor for the mixture but only for (90)Y. Activity measurements of a (90)Sr/(90)Y source with the (90)Y calibration factor are performed in order to correct for the extra-contribution of (90)Sr. The value of the correction factor was found to be 1.113 whereas Monte Carlo simulations of the radionuclide calibrators estimate the correction factor to be 1.117. Measurements with (18)F sources in a specific geometry are also performed. Since this radionuclide is widely used in Swiss hospitals equipped with PET and PET-CT, the metrology of the (18)F is very important. The (18)F response normalized to the (137)Cs response shows that the difference with a reference value does not exceed 3% for the three types of radionuclide calibrators.