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Deviation in the predefined calibration factors of the dose calibrators and the associated inaccuracy in the radioactivity measurements of beta-gamma emitters.

Sharma S, Singh B, Koul A, Mittal BR - Indian J Nucl Med (2015 Apr-Jun)

Bottom Line: A deviation of ± 5.0% was observed when radioactivity of (177)Lu and (153)Sm was measured over a wide range (4.0 MBq to 2.1 GBq) for time intervals equivalent to 4.5 half-lives of each of the two radionuclides.A deviation of ± 5% was observed when radioactivity was counted in different dilution volumes and in syringes of varying size.These variations could lead to a cumulative error of about 20.0% toward the inaccuracy in the radioactivity measurements of the beta-gamma emitters and thus predefined calibration factors of the dose calibrators may require experimental re-setting of these parameters and periodic checking to provide accurate radioactivity estimates of beta-gamma emitters in a given clinical setting.

View Article: PubMed Central - PubMed

Affiliation: Department of Nuclear Medicine and PET, PGIMER, Chandigarh, India.

ABSTRACT

Aim: To determine whether the predefined calibration factors of the dose calibrators can provide accurate radioactivity measurements of beta-gamma emitters used in routine therapeutic nuclear medicine procedures.

Materials and methods: Two models of dose calibrators were used in the present study for radioactivity measurements of (153)Sm ethylenediamine-N, N, N', N'-tetrakis methylene phosphonic acid (EDTMP) and (177)Lu (EDTMP). A known (precalibrated) activity of each of the two beta emitters received by us from our National Supplier for administration to the patients with extensive bony metastases for bone pain palliation, was used for experiments.

Results: When we used the manufacturers' provided dial setting of 450 × 10, each of the dose calibrators underestimated the radioactivity of (177)Lu by about 9.0%. Dial settings of 403 × 10 and 408 × 10 for (177)Lu on CRC-15R and CRC-ultra dose calibrators respectively were calculated experimentally using an iterative approach. The radioactivity measurements made at these settings provided an excellent agreement with the specified values. Likewise, a dial setting of 230 for each of the two dose calibrators was calculated for (153)Sm, which provided a good agreement between the experimentally derived radioactivity values and the certified values. A deviation of ± 5.0% was observed when radioactivity of (177)Lu and (153)Sm was measured over a wide range (4.0 MBq to 2.1 GBq) for time intervals equivalent to 4.5 half-lives of each of the two radionuclides. A deviation of ± 5% was observed when radioactivity was counted in different dilution volumes and in syringes of varying size.

Conclusion: These variations could lead to a cumulative error of about 20.0% toward the inaccuracy in the radioactivity measurements of the beta-gamma emitters and thus predefined calibration factors of the dose calibrators may require experimental re-setting of these parameters and periodic checking to provide accurate radioactivity estimates of beta-gamma emitters in a given clinical setting.

No MeSH data available.


Related in: MedlinePlus

The percentage deviations between the measured and calibrated activity of Sm-153 on different calibration factors for both CRC-15R and CRC-ultra dose calibrators
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Figure 2: The percentage deviations between the measured and calibrated activity of Sm-153 on different calibration factors for both CRC-15R and CRC-ultra dose calibrators

Mentions: To start with the calibration process, 153Sm radioactivity measurements were made on each of the dose calibrator using the calibration factors of technetium-99 m (80), iodine-131 (151) and thallium-201 (205). The observed readings at these settings were significantly different from the calibrated activity of the radionuclide. These channel numbers and their response factors when used in equation-1 provided a value of 230 as the dial setting factor for 153Sm measurements on both the dose calibrators. As a part of the calibration procedure, BRIT, BARC certified amount of 153Sm-EDTMP solution was measured in a glass vial on each dose calibrator using different dial settings/calibration factors ranging from 80 to 250. A minimum percent difference in the measured and certified radioactivity of 153Sm was observed with the dial settings of 229 and 232 on both the dose calibrators [Figure 2]. At a dial setting of 230, the difference in the measured and the certified activity was negligible (<0.55%). This dial setting factor was used for all further radioactivity measurements of 153Sm on both the dose calibrators. A linearity check (at dial setting of 230, for four and half half-lives [210 h]) performed on each dose calibrator over an activity range 4 MBq to 2.1 GBq of 153Sm showed maximum difference of ± 5% as shown in Figure 3a.


Deviation in the predefined calibration factors of the dose calibrators and the associated inaccuracy in the radioactivity measurements of beta-gamma emitters.

Sharma S, Singh B, Koul A, Mittal BR - Indian J Nucl Med (2015 Apr-Jun)

The percentage deviations between the measured and calibrated activity of Sm-153 on different calibration factors for both CRC-15R and CRC-ultra dose calibrators
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4379670&req=5

Figure 2: The percentage deviations between the measured and calibrated activity of Sm-153 on different calibration factors for both CRC-15R and CRC-ultra dose calibrators
Mentions: To start with the calibration process, 153Sm radioactivity measurements were made on each of the dose calibrator using the calibration factors of technetium-99 m (80), iodine-131 (151) and thallium-201 (205). The observed readings at these settings were significantly different from the calibrated activity of the radionuclide. These channel numbers and their response factors when used in equation-1 provided a value of 230 as the dial setting factor for 153Sm measurements on both the dose calibrators. As a part of the calibration procedure, BRIT, BARC certified amount of 153Sm-EDTMP solution was measured in a glass vial on each dose calibrator using different dial settings/calibration factors ranging from 80 to 250. A minimum percent difference in the measured and certified radioactivity of 153Sm was observed with the dial settings of 229 and 232 on both the dose calibrators [Figure 2]. At a dial setting of 230, the difference in the measured and the certified activity was negligible (<0.55%). This dial setting factor was used for all further radioactivity measurements of 153Sm on both the dose calibrators. A linearity check (at dial setting of 230, for four and half half-lives [210 h]) performed on each dose calibrator over an activity range 4 MBq to 2.1 GBq of 153Sm showed maximum difference of ± 5% as shown in Figure 3a.

Bottom Line: A deviation of ± 5.0% was observed when radioactivity of (177)Lu and (153)Sm was measured over a wide range (4.0 MBq to 2.1 GBq) for time intervals equivalent to 4.5 half-lives of each of the two radionuclides.A deviation of ± 5% was observed when radioactivity was counted in different dilution volumes and in syringes of varying size.These variations could lead to a cumulative error of about 20.0% toward the inaccuracy in the radioactivity measurements of the beta-gamma emitters and thus predefined calibration factors of the dose calibrators may require experimental re-setting of these parameters and periodic checking to provide accurate radioactivity estimates of beta-gamma emitters in a given clinical setting.

View Article: PubMed Central - PubMed

Affiliation: Department of Nuclear Medicine and PET, PGIMER, Chandigarh, India.

ABSTRACT

Aim: To determine whether the predefined calibration factors of the dose calibrators can provide accurate radioactivity measurements of beta-gamma emitters used in routine therapeutic nuclear medicine procedures.

Materials and methods: Two models of dose calibrators were used in the present study for radioactivity measurements of (153)Sm ethylenediamine-N, N, N', N'-tetrakis methylene phosphonic acid (EDTMP) and (177)Lu (EDTMP). A known (precalibrated) activity of each of the two beta emitters received by us from our National Supplier for administration to the patients with extensive bony metastases for bone pain palliation, was used for experiments.

Results: When we used the manufacturers' provided dial setting of 450 × 10, each of the dose calibrators underestimated the radioactivity of (177)Lu by about 9.0%. Dial settings of 403 × 10 and 408 × 10 for (177)Lu on CRC-15R and CRC-ultra dose calibrators respectively were calculated experimentally using an iterative approach. The radioactivity measurements made at these settings provided an excellent agreement with the specified values. Likewise, a dial setting of 230 for each of the two dose calibrators was calculated for (153)Sm, which provided a good agreement between the experimentally derived radioactivity values and the certified values. A deviation of ± 5.0% was observed when radioactivity of (177)Lu and (153)Sm was measured over a wide range (4.0 MBq to 2.1 GBq) for time intervals equivalent to 4.5 half-lives of each of the two radionuclides. A deviation of ± 5% was observed when radioactivity was counted in different dilution volumes and in syringes of varying size.

Conclusion: These variations could lead to a cumulative error of about 20.0% toward the inaccuracy in the radioactivity measurements of the beta-gamma emitters and thus predefined calibration factors of the dose calibrators may require experimental re-setting of these parameters and periodic checking to provide accurate radioactivity estimates of beta-gamma emitters in a given clinical setting.

No MeSH data available.


Related in: MedlinePlus