Bolus elution

Elution and Breakthrough Characteristics of the Generator. The fractional elution yield and cumulative yield of Rb-82 are shown in Figure 5a,b for 2% saline bolus elutions at a flow rate of 1 ml/sec. Nine 3 ml fractions were collected over 27 sec. Each value is the mean of 3 determinations. Fractions 3-5 contain 70% of the Rb-82 available from the Sr-82 on the alumina column. The total elution yield is about 95% in nine fractions. 

The experimental conditions for the bolus elution mode are identical to the conditions described above except that the sample is collected from the beginning of the elution. The first milliliters contain the elutable portion of the... 

If four half-lives (Tly ) occur between two successive bolus elutions, the growth of daughter activity will correspond to 94% of the maximum possible per bolus and the total waiting time will be defined by equation (17). 

The Rb-82 generator permits serial studies in the same patient as often as every 10 minutes with 20-60 mCi of Rb-82 for rapid bolus intravenous infusion. Inherent in the administration of high levels of Rb-82 activity is the need for precise flow control from an automated system to deliver the desired amount of radioactivity. The development of the alumina column parameters and the elution protocol as well as the automated microprocessor system controller are presented here. Some of the details of this system have been discussed in earlier publications (15,21). Generator produced Rb-82 is used as a diffusible flow tracer in myocardial perfusion studies and as a nondiffusible tracer in brain studies to assess blood brain barrier permeability changes in patients with brain tumors or Alzheimer s type dementia. 

Figure T. Elution time in s to deliver 20 mCi of Kb-82 for bolus infusion studies at a flow rate of 1 mL/s. (Reproduced with permission from Ref. 21. Copyright 1981, J. Nucl. Med.)...

Elution Methods. For every generator, the separation of the daughter nuclide from the parent can be performed by the continuous (steady state) method or the discontinuous (bolus) method. The continuous method involves the elution of the daughter nuclide from the generator as it is formed and direct administration as a gas or liquid phase. The bolus method involves the elution at one time of the available daughter... 

Fractional elution may be indicated when small volumes of high activity are needed for bolus injection or for labeling. In the case of generator I, it will suffice to elute a total volume of 3 ml, while two 3-ml fractions should be obtained in the case of generator II, since the main activity peak is collected in the second fraction. 

In the most widely used generator, Mo is loaded onto a column of alumina and Tc is eluted fi om the column with normal saline. The required bolus volume for the quantitative elution of obviously depends on the size of the column which in turn is inversely... 

The automated elution system (Geimaro et al. 1984 Knapp and Butler 1984) provides Rb for direct intravenous bolus injection, with an average dose of about 1.9 GBq ( 50 mCi) for cardiac PET and sequential rest versus stress studies, is used to identify normal versus abnormal myocardium in patients with suspected myocardial infi action, as well as for the assessment of coronary blood flow, degree of stenosis, viability assessment, and to monitor recovery and maintenance. The generator is routinely used in clinical practice (e.g., Williams et al. 1994 Alvarez-Diez et al. 1999). Rb infusion systems for quantitative perfusion imaging were developed (Epstein et al. 2004 Klein et al. 2007). 

When the volume of injection solvent is small, the dilution with the supercritical fluid mobile phase leads to conditions of elution for the solutes which are almost identical to the conditions of elution with the supercritical fluid itself. As the volume of injection is increased there is less dilution of the bolus of solvent by the mobile phase and the solvent acts as a second eluting mobile phase for part of the solute, giving rise to an adjacent earlier eluted peak. The amplitude of the band broadening depends on the nature of the sample solvent. 

Isolation and purification of Toxin-PC - Protein precipitated with 50% ammonium sulphate saturation possessed lethality (MED 46 pg/20 gm mice, iv. bolus). The fold of purification achieved by the process was 1.95 (Table 1). The same precipitate of the venom was loaded on DEAE cellulose column. Seven distinct protein peaks were eluted. Peak 7 eluted with 0.2 M acetate buffer pH 5.0 and possessed lethality. The fold of purification was found to be 15 with a yield of 8.8% (Table 1), and it was provisionally designated as Toxin-PC (P = Plotosus, C = Canius). 

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