Dose Equivalent Rate Constants and Barrier Transmission Data for Nuclear Medicine Facility Dose Calculations and Shielding Design

Abstract

A primary goal of nuclear medicine facility design is to keep public and worker radiation doses As Low As Reasonably Achievable (ALARA). To estimate dose and shielding requirements, one needs to know both the dose equivalent rate constants for soft tissue and barrier transmission factors (TFs) for all radionuclides of interest. Dose equivalent rate constants are most commonly calculated using published air kerma or exposure rate constants, while transmission factors are most commonly calculated using published tenth-value layers (TVLs). Values can be calculated more accurately using the radionuclide's photon emission spectrum and the physical properties of lead, concrete, and/or tissue at these energies. These calculations may be non-trivial due to the polyenergetic nature of the radionuclides used in nuclear medicine. In this paper, the effects of dose equivalent rate constant and transmission factor on nuclear medicine dose and shielding calculations are investigated, and new values based on up-to-date nuclear data and thresholds specific to nuclear medicine are proposed. To facilitate practical use, transmission curves were fitted to the three-parameter Archer equation. Finally, the results of this work were applied to the design of a sample nuclear medicine facility and compared to doses calculated using common methods to investigate the effects of these values on dose estimates and shielding decisions. Dose equivalent rate constants generally agreed well with those derived from the literature with the exception of those from NCRP 124. Depending on the situation, Archer fit TFs could be significantly more accurate than TVL-based TFs. These results were reflected in the sample shielding problem, with unshielded dose estimates agreeing well, with the exception of those based on NCRP 124, and Archer fit TFs providing a more accurate alternative to TVL TFs and a simpler alternative to full spectral-based calculations. The data provided by this paper should assist in improving the accuracy and tractability of dose and shielding calculations for nuclear medicine facility design.

Quality and Quantity Assessment of Tomographic Exams That Can Be Performed on Existing Hybrid Equipment at Botucatu Medical School Nuclear Medicine Services

“…To determine the shielding thickness, Archer's equation was used. The parameters adopted for the predicted energies and the reduction factors used were obtained from a paper published in the journal Health Physics, by Kusano and Caldwell [14].…”

Shielding commissioning factors in nuclear medicine facilities

“…In the AAPM 108 report [3], the shielding requirements for PET facilities are specified in terms of effective dose by the federal code of regulations 10 CFR20 [9]. In nuclear medicine, however, a formal consensus is yet to be reached, individual groups have proposed the use of air kerma [8], equivalent dose to soft tissue [4,10,11] or ambient equivalent dose [12,13] in shielding calculation. To be in line with the AAPM 108 report [3] and the ICRP dose limits, the authors aim to apply the effective dose as the dose quantity of choice for nuclear medicine shielding considerations.…”

“…The decay data to derive the dose rate constants was from the Brookhaven Laboratory National Nuclear Data Centre Decay Data Compendium [16]. Only the penetrating radiations: gamma and x-ray emissions were considered with an energy threshold of 20 keV, which is consistent with other published works [11,17,18]. The mass absorption coefficients and the effective dose conversion factors were obtained using log-log cubic spline and linear interpolations, respectively, from their corresponding sources: Hubbell and Seltzer [19] and ICRP 116 [20].…”

“…Comparison of the air kerma rate constants derived in this work with published results.Air kerma rate constant (μGy m 2 h −1 GBq −1 )Radionuclide Wasserman[18] Ninkovic[19] Kusano[11] This work…”

Evaluation of X-ray spectra transmitted by different concrete compositions

“…The Archer model was adopted by NCRP (National Council on Radiation Protection, 2004) as the adequate method for fitting transmission data from shielding materials applied on diagnostic imaging facilities. Additionally, the model was adopted for shielding purposes on Nuclear Medicine (Kusano and Caldwell, 2014) and PET/CT (Madsen et al, 2006) installations. The Model is represented by the equation:…”