Effect of blood activity on dosimetric calculations for radiopharmaceuticals

Zvereva, Alexandra; Petoussi-Henss, Nina; Li, Wei Bo; Schlattl, Helmut; Oeh, Uwe; Zankl, M.; Graner, Frank Philipp; Hoeschen, Christoph; Nekolla, Stephan G.; Parodi, Katia; Schwaiger, Markus

doi:10.1088/0031-9155/61/21/7688

Cited by 5 publications

(9 citation statements)

References 16 publications

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“…Two sources of uncertainties were investigated: the interindividual variability in the TIACs and the differences among the anatomical models employed for dosimetry. The TIACs were computed based on the individual‐specific pharmacokinetic models in our previous work . The pharmacokinetic models were assumed to be fixed.…”

Section: Discussionmentioning

confidence: 99%

“…The TIACs were computed based on the individual-specific pharmacokinetic models in our previous work. 24 The pharmacokinetic models were assumed to be fixed. Thus, the uncertainties associated with the model structure were neglected.…”

Section: Discussionmentioning

confidence: 99%

“…The activity data were initially acquired by Smolarz et al . from five healthy volunteers (two men, three women) and used for the development of the compartmental pharmacokinetic models for this agent, as reported elsewhere . The 11 source regions for 18 F‐FSPG included kidneys, bladder content, heart, thyroid, salivary glands, pancreas, stomach wall, liver, spleen, rest of body and blood.…”

Section: Methodsmentioning

confidence: 99%

“…The values of TIACs employed here were originally computed as the area under the organ time‐activity curves predicted by compartmental pharmacokinetic models elsewhere for the case of blood being a distinct source region. For 18 F‐FSPG 11 TIAC input factors were considered, that is equal to the number of the source regions.…”

Section: Methodsmentioning

confidence: 99%

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Impact of interpatient variability on organ dose estimates according to MIRD schema: Uncertainty and variance‐based sensitivity analysis

Zvereva¹,

Kamp

Schlattl

et al. 2018

Medical Physics

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Global variance-based SA has been for the first time applied to the MIRD schema for internal dose calculation. Our findings suggest that uncertainties in computed organ doses can be substantially reduced by performing an accurate determination of TIACs in the source regions, accompanied by the estimation of individual source region masses along with the usage of an appropriate blood distribution in a patient's body and, in a few cases, the cross-fire SAFs from proximal source regions.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Impact of interpatient variability on organ dose estimates according to MIRD schema: Uncertainty and variance‐based sensitivity analysis

Zvereva¹,

Kamp

Schlattl

et al. 2018

Medical Physics

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“…It was previously shown that blood activity has a substantial effect on absorbed doses for highly vascular organs, which are not source regions [40]. As mentioned above, total blood as source region consists of blood vessels and RBVs.…”

Section: Monte Carlo Calculationsmentioning

confidence: 95%

Feasibility of reducing differences in estimated doses in nuclear medicine between a patient-specific and a reference phantom

et al. 2017

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The feasibility of reducing the differences between patient-specific internal doses and doses estimated using reference phantoms was evaluated. Relatively simple adjustments to a polygon-surface ICRP adult male reference phantom were applied to fit selected individual dimensions using the software Rhinoceros®4.0. We tested this approach on two patient-specific phantoms: the biggest and the smallest phantoms from the Helmholtz Zentrum München library. These phantoms have unrelated anatomy and large differences in body-mass-index. Three models approximating each patient's anatomy were considered: the voxel and the polygon-surface ICRP adult male reference phantoms and the adjusted polygon-surface reference phantom. The Specific Absorbed Fractions (SAFs) for internal photon and electron sources were calculated with the Monte Carlo code EGSnrc. Employing the time-integrated activity coefficients of a radiopharmaceutical (S)-4-(3-F-fluoropropyl)-l-glutamic acid and the calculated SAFs, organ absorbed-dose coefficients were computed following the formalism promulgated by the Committee on Medical Internal Radiation Dose. We compared the absorbed-dose coefficients between each patient-specific phantom and other models considered with emphasis on the cross-fire component. The corresponding differences for most organs were notably lower for the adjusted reference models compared to the case when reference models were employed. Overall, the proposed approach provided reliable dose estimates for both tested patient-specific models despite the pronounced differences in their anatomy. To capture the full range of inter-individual anatomic variability more patient-specific phantoms are required. The results of this test study suggest a feasibility of estimating patient-specific doses within a relative uncertainty of 25% or less using adjusted reference models, when only simple phantom scaling is applied.

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Specific absorbed fractions for a revised series of the UF/NCI pediatric reference phantoms: internal photon sources

et al. 2021

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Assessment of radiation absorbed dose to internal organs of the body from the intake of radionuclides, or in the medical setting through the injection of radiopharmaceuticals, is generally performed based upon reference biokinetic models or patient imaging data, respectively. Biokinetic models estimate the time course of activity localized to source organs. The time-integration of these organ activity profiles are then scaled by the radionuclide S-value, which defines the absorbed dose to a target tissue per nuclear transformation in various source tissues. S-values are computed using established nuclear decay information (particle energies and yields), and a parameter termed the specific absorbed fraction (SAF). The SAF is the ratio of the absorbed fraction—fraction of particle energy emitted in the source tissue that is deposited in the target tissue—and the target organ mass. While values of the SAF may be computed using patient-specific or individual-specific anatomic models, they have been more widely available through the use of computational reference phantoms. In this study, we report on an extensive series of photon SAFs computed in a revised series of the University of Florida and the National Cancer Institute pediatric reference phantoms which have been modified to conform to the specifications embodied in the ICRP reference adult phantoms of Publication 110 (e.g. organs modeled, organ ID numbers, blood contribution to elemental compositions). Following phantom anatomical revisions, photon radiation transport simulations were performed using MCNPX v2.7 in each of the ten phantoms of the series—male and female newborn, 1 year old, 5 year old, 10 year old, and 15 year old—for 60 different tissues serving as source and/or target regions. A total of 25 photon energies were considered from 10 keV to 10 MeV along a logarithm energy grid. Detailed analyses were conducted of the relative statistical errors in the Monte Carlo target tissue energy deposition tallies at low photon energies and over all energies for source–target combinations at large intra-organ separation distances. Based on these analyses, various data smoothing algorithms were employed, including multi-point weighted data smoothing, and log–log interpolation at low energies (1 keV and 5 keV) using limiting SAF values based upon target organ mass to bound the interpolation interval. The final dataset is provided in a series of ten electronic supplemental files in MS Excel format. The results of this study were further used as the basis for assessing the radiative component of internal electron source SAFs as described in our companion paper (Schwarz et al 2021) for this same pediatric phantom series.

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Effect of blood activity on dosimetric calculations for radiopharmaceuticals

Cited by 5 publications

References 16 publications

Impact of interpatient variability on organ dose estimates according to MIRD schema: Uncertainty and variance‐based sensitivity analysis

Impact of interpatient variability on organ dose estimates according to MIRD schema: Uncertainty and variance‐based sensitivity analysis

Feasibility of reducing differences in estimated doses in nuclear medicine between a patient-specific and a reference phantom

Specific absorbed fractions for a revised series of the UF/NCI pediatric reference phantoms: internal photon sources

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