Master in Medical Physics 2015 to 2016

Practical Report Non-imaging Instrumentation QC

Francisco J. Hernandez Flores

International Centre for Theoretical Physics

franciscohernandez_f2010@hotmail.com

December 29, 2015

Abstract

This task is relationship with Radiopharmaceuticals are radioactively labeledcompounds fulfilling the requirements of pharmaceutical products, used in ra-dio diagnosis or radiotherapy. One essential parameter in the quality control ofradiopharmaceuticals is the radionuclidic purity. In this work, we present as-pects regarding the radionuclidic purity determination for the radiopharmaceuticalproducts: Sodium Iodide (131I) solution; Sodium Iodide (131I) capsules for radio-diagnosis; Sodium Pertechnetate (99mTc) injection (non-fission). radionuclidicpurity, radiopharmaceuticals, nuclear medicine, gamma-ray spectrometry.

I. Introduction

Radiopharmaceuticals are radioactively labeled compounds fulfilling the re-quirements for pharmaceutical products, used in radiodiagnosis or radiotherapy.In order to become a radiopharmaceutical product, a chemical product under-goes a labeling procedure using a certain radionuclide with the adequatenuclear characteristics for the desired use in nuclear medicine. The selectionof a radionuclide for radiodiagnosis and radiotherapy must take account someaspects: the radionuclide must have specific nuclear characteristics, for thegamma radiation energy to allow the aquisition of good scintigraphies;

• the radionuclide must have adequate radiation energies and half-life suchthat the internal irradiation dose delivered to the patient after admin-istration of radiopharmaceutical, for the whole duration of the medicalprocedure, to be as low as possible.

• The radionuclide must have certain chemical properties enabling its bi-ological behavior to answer the desired purposes (localization only inthe targeted organ) and the time until its clearance form the organism(biologic half- life) to be as short as possible. The product must have aselective affinity toward certain organs or groups of organs and in somespecific cases to be metabolized, being physiologically inert and non toxic

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Master in Medical Physics 2015 to 2016

II. Theory

I. Spectrometry

The term spectroscopy, literally the viewing of a spectrum, is a detection systemthat yields information about the energy distribution of the incident radiation.Most of the radiation measurement systems used in nuclear medicine usepulse-height analysis to sort out the different radiation energies striking thedetector. This is called pulse-height or energy spectrometry. It is used todiscriminate against background radiation, scattered radiation, and so on, andidentify the emission energies of unknown radionuclides. Monochromaticlight of wavelength λ is incident on a grating with N apertures each of widthD and separated by a distance d. The light diffracts into equally spaced sincfunctions (called "orders") modulated by an "envelope" sinc function. Each orderhas angular width w ≈ 2λ/Nd and the angular separation between orders is≈ 2λ/d . Different frequencies are separated because the location of an orderdepends on λ.

Figure 1: spectro of diferent energies

III. Materials and Methods

To bring about this practice we were used the following instrumentation.Gamma probe, High purity Germanium detector see fig. 3

Radionuclidic generator of 99Mo-99mTc consists of:

• Generator column filled with alumina on which molybdenum-99 (en-riched molybdenum-98) is adsorbed. [1] The bottom end of the columnis provided with a glass filter to prevent any leakage of alumina fromthe column. Top and bottom ends of the column are closed with rubberstoppers and caps;

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Master in Medical Physics 2015 to 2016

• A set of stainless steel needles which connects generator column with theeluent bottle and eluate vials;

• The column and the needles are placed inside lead shielding of 35 or 50mm wall thickness. This shielding protects personnel from radiation andallows easy operation of the generator. The thickness of the lead walldepends on the Molybdenum-99 activity adsorbed on the column 2.

Figure 2: The column Elution

The radiation detector used in the hospital uses a high purity Germaniumdetector to make gamma spectrometry, see Fig. 3. This can be done in order tohave a quality control for radionuclide generators (99Mo-99mTc), this provides amore accurate quality control of the purity, but it is off-line, delayed measure,and when Tc is decayed significantly, also it is possible to search for othercontaminants.

Figure 3: High purity Germanium detector

IV. discussion and results

This practical class was descriptive and discus about the process of the use ofequipment used in nuclear medicine, talked about functioning of high purityGermanium used in medicine for detect the impurity in the 99mTc.

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Master in Medical Physics 2015 to 2016

Radio nuclidic purity. The European Pharmacopeia and national regulatoryagencies recommend determination of 99Mo in the primary elute to assure highquality of generator eluates (DIN 6854).

Generators are eluted after shipment before administration of eluates topatient. The primary eluate contains the highest concentration of chemicalimpurities and of carrier 99Tc (decay product).also parent 99Mo is highest in thefirst eluate (Hammer-mayer et al.1986).

Less than 0.1% of the total 99Tc activity is due to the parent 99Mo and nomore than 0.01% is due to the other radionuclidic impurities the table 1 showthe percentage of different material . these limits are however never observedwith the available generator system.

% of total activity99Mo ≤ 0.1%131 I ≤ 5 × 10−3%

103Ru ≤ 5 × 10−3%%89Sr ≤ 6 × 10−5%90Sr ≤ 6 × 10−6%

α emitting impurities ≤ 1 × 10−7%γ emitting impurities ≤ 0.01%

Table 1: EUROPEAN PHARMACOPOEIA IV - 2002 Sodium Pertechnetate 99Tc Injection [1]

V. Conclusion

• The radionuclidic purity is an essential parameter in the quality control ofradiopharmaceuticals. The radionuclidic purity for radiopharmaceuticalproducts must be higher than 95%, according to the European Pharma-copoeia.

HPGe (n-type, coaxial) detectors are at present the best γ-ray detectors (inthe energy range 0.1 to 10 MeV) due to:

• The high energy resolution of the semiconductor Ge material, and

• The high full energy efficiency of large detectors. For typical nuclearstructure experiments with high γ-ray multiplicities, such detectors arearranged in large arrays.

References

[1] Formasier M.R, Lecture Nuclear Medicine , ICTP, Trieste Italy, 3rd trimester2015.

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