Updated Age-Specific External Dose and Exposure Rate Coefficients for 131i Patient Release

Aziz, L; Dewji, Shaheen

doi:10.1093/rpd/ncac049

Cited by 1 publication

(8 citation statements)

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“…Although the value λ th = 0.07 d −1 produces good agreement between the clinical data and the computed biokinetics, it is much lower than values typically cited in the literature for DTC patients (typically ∼1.04 d −1 representing 5% thyroid uptake: Aziz and Dewji 2022), which may be attributable to individual ESRD patient metabolic behavior. It is also worth noting that Pahlka and Sonnad (2006) used a value of λ = 0.15 d −1 for 5% uptake, suggesting that the choice of λ th has served as a reference value in such kinetics modeling.…”

Section: Resultsmentioning

confidence: 58%

“…Normalizing by the individual patient’s residual thyroid function was preferable, but thyroid uptake cannot be easily estimated from a single blood marker, unlike GFR, which is easily estimated from serum creatinine. Additionally, applying average values found in the literature, e.g., λ th = 1.04 d −1 corresponding to an uptake of 5% (Aziz and Dewji 2022) for DTC patients, resulted in non-convergence of the computed biokinetics and clinical data regardless of the fit parameter λ bd . Empirically, after the first two HD sessions, the majority of the retained activity was contained in the thyroid (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The Monte Carlo N-Particle Transport Code version 6.2 (MCNP 6.2) (Werner 2017), along with the Oak Ridge National Laboratory (ORNL) adult stylized computational hermaphroditic phantoms, were used to calculate external dose rates in probable exposure scenarios. Originally developed by Cristy and Eckerman at ORNL and later modified by Han et al (2006) to refine elemental compositions of constituent organs and tissues, the stylized phantoms contain all necessary organs for calculating effective dose according to ICRP Publication 103 methodology except for the extrathoracic region and the lymphatic system, for which the thymus is an effective surrogate (Han et al 2006; Aziz and Dewji 2022). The masses, compositions, and densities of tissues and organs constituting the phantoms are consistent with ICRP 89 (ICRP 2002) and the International Commission on Radiation Units and Measurements (ICRU) Report 46 (Scott 1993).…”

Section: Methodsmentioning

confidence: 99%

“…For calculations of effective dose rate coefficients, two directly facing adult phantoms were placed at various distances from each other, between 10 and 300 cm, one phantom representing the patient and the other the exposed member of the public, as given in (Aziz and Dewji 2022). Using an F6 tally for energy deposition (Werner 2017), the absorbed dose and organ dose concentrations were estimated in the receptor.…”

Section: Methodsmentioning

confidence: 99%

“…Likewise, Dewji et al (2015) determined that the point-source model overestimated the external dose rate to an exposed adult between 10 and 300 cm regardless of time post 131 I administration and calculated an overestimation by a factor of 1.9 at 8 h post-administration at 1 m and 3.3 at 8 h for a DTC patient (Dewji et al 2015). Aziz and Dewji (2022) similarly calculated an overestimation by a factor of 24.22 for the dose to an exposed adult from an adult with DTC undergoing RAI therapy at 48 h post-administration. Compared to Rev.…”

Section: Proposed Revisionmentioning

confidence: 99%

See 4 more Smart Citations

Radiation Protection Considerations for Cancer Patients with End-stage Renal Disease Receiving 131I Treatment

Louis,

Mate-Kole,

Aziz

et al. 2023

Health Physics

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Differentiated thyroid cancer (DTC) is commonly treated first with a partial or complete thyroidectomy, followed by radioiodine (RAI) ablative therapy to eliminate remaining cancer cells. In such treatments, physical decay and urinary excretion are the primary means of 131I. As such, patients with impaired urinary ability clearance, such as patients with end-stage renal disease (ESRD) whose urinary ability is impaired by dysfunction, can retain abnormally high activities of RAI, posing a concern to both the patient and those with whom the patient interacts. Additionally, ESRD patients are commonly administered dialysis therapy, wherein their blood is externally cycled through a dialyzer (hemodialysis) or filtered by instilling a dialysate fluid into the peritoneum (peritoneal dialysis) to filter uremic toxins from their blood that accumulate due to kidney dysfunction. These factors make determining release and dosing for ESRD patients receiving RAI therapy dependent on a plurality of variables. An evaluation of the current patient release guidelines, as given in US Nuclear Regulatory Commission (US NRC) Regulatory Guide 8.39 Rev. 1 for ESRD patients receiving RAI, has yet to be addressed. In this study, a biokinetic model for 131I in ESRD patients receiving dialysis has been developed, improving on traditional two-compartment models, reflective of kinetics from multi-compartment models with updated transfer coefficients modified to reflect the different physiological functions of compartments. This updated biokinetic model was integrated with Monte Carlo radiation transport calculations using stylized computational hermaphroditic phantoms to calculate dose rate coefficients in exposure scenarios and compared with those of the point source models of NRC Reg Guide 8.39 Rev. 1 (and the proposed verbiage in Rev. 2). Results demonstrated that the baseline models of Rev. 1 and Rev. 2 overestimated the effective dose rate to an exposed individual for the majority of time post-administration, where both models overestimated the total dose to the maximally exposed individual. However, the application of several patient-specific modifying factors to the Rev. 2 model resulted in an overestimation by only a factor of 1.25, and in general, the results produced with the patient-specific modifications provide improved convergence with the dose rate coefficients computed in this study for ESRD patients.

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Section: Resultsmentioning

confidence: 58%

Section: Methodsmentioning

confidence: 99%