A microdosimetric analysis of absorbed dose to tumor as a function of number of microspheres per unit volume in 90Y Radioembolization

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Abstract

Differences in maximum tolerable absorbed dose to normal liver between 90Y radioembolization and external-beam radiation therapy have been explained by citing differences in absorbed-dose heterogeneity at the microscopic level. We investigated microscopic absorbed-dose heterogeneity in radioembolization as a function of the number of microspheres per unit volume in tumor. The goal was to determine what effect the number of microspheres may have, if any, on tumor control in 90Y radioembolization. Methods: 90Y PET/CT data were combined with microscopic probability-density functions describing microsphere clustering to provide realistic simulation using Monte Carlo modeling on both a macroscopic and a microscopic level. A complete microdosimetric analysis using 100-μm voxels was performed on the basis of 90Y PET/CT data from 19 tumors treated using radioembolization. Simulations were performed with average tumor microsphere-number densities from 200 to 70,000 spheres/mL. Monte Carlo simulations of each tumor and number density were repeated 20 times to establish SE. A 2-way balanced ANOVA was used to determine whether differences in microsphere-number density affected common tumor-dose metrics. Results: Decreasing the microsphere-number density resulted in a decrease in D70, the minimum dose to 70% of the tumor. The slope of the dose-volume histogram also decreased with decreasing microsphere-number density in all tumors. Compared with a density of 50,000 spheres/mL, decreases in D70 were statistically significant below 20,000 spheres/mL. However, these differences are unlikely to have clinical significance until the density decreases to below 5,000 spheres/mL. Although D70 was decreased at a low microsphere-number density, one can compensate for decreases by an increase in the average tumor-absorbed dose, that is, by increasing the radioembolization treatment dose. Conclusion: Differences in microsphere-number density may have an effect on microscopic tumor absorbed-dose inhomogeneity. These results begin to explain differences in treatment planning strategies between glass and resin radioembolization devices.

Original languageEnglish (US)
Pages (from-to)1020-1026
Number of pages7
JournalJournal of Nuclear Medicine
Volume57
Issue number7
DOIs
StatePublished - Jul 1 2016

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Microspheres
Neoplasms
Tumor Burden
Glass
Cluster Analysis
Analysis of Variance
Radiotherapy
Equipment and Supplies
Liver

All Science Journal Classification (ASJC) codes

  • Radiology Nuclear Medicine and imaging

Cite this

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title = "A microdosimetric analysis of absorbed dose to tumor as a function of number of microspheres per unit volume in 90Y Radioembolization",
abstract = "Differences in maximum tolerable absorbed dose to normal liver between 90Y radioembolization and external-beam radiation therapy have been explained by citing differences in absorbed-dose heterogeneity at the microscopic level. We investigated microscopic absorbed-dose heterogeneity in radioembolization as a function of the number of microspheres per unit volume in tumor. The goal was to determine what effect the number of microspheres may have, if any, on tumor control in 90Y radioembolization. Methods: 90Y PET/CT data were combined with microscopic probability-density functions describing microsphere clustering to provide realistic simulation using Monte Carlo modeling on both a macroscopic and a microscopic level. A complete microdosimetric analysis using 100-μm voxels was performed on the basis of 90Y PET/CT data from 19 tumors treated using radioembolization. Simulations were performed with average tumor microsphere-number densities from 200 to 70,000 spheres/mL. Monte Carlo simulations of each tumor and number density were repeated 20 times to establish SE. A 2-way balanced ANOVA was used to determine whether differences in microsphere-number density affected common tumor-dose metrics. Results: Decreasing the microsphere-number density resulted in a decrease in D70, the minimum dose to 70{\%} of the tumor. The slope of the dose-volume histogram also decreased with decreasing microsphere-number density in all tumors. Compared with a density of 50,000 spheres/mL, decreases in D70 were statistically significant below 20,000 spheres/mL. However, these differences are unlikely to have clinical significance until the density decreases to below 5,000 spheres/mL. Although D70 was decreased at a low microsphere-number density, one can compensate for decreases by an increase in the average tumor-absorbed dose, that is, by increasing the radioembolization treatment dose. Conclusion: Differences in microsphere-number density may have an effect on microscopic tumor absorbed-dose inhomogeneity. These results begin to explain differences in treatment planning strategies between glass and resin radioembolization devices.",
author = "Alexander Pasciak and Austin Bourgeois and Yong Bradley",
year = "2016",
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doi = "10.2967/jnumed.115.163444",
language = "English (US)",
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T1 - A microdosimetric analysis of absorbed dose to tumor as a function of number of microspheres per unit volume in 90Y Radioembolization

AU - Pasciak, Alexander

AU - Bourgeois, Austin

AU - Bradley, Yong

PY - 2016/7/1

Y1 - 2016/7/1

N2 - Differences in maximum tolerable absorbed dose to normal liver between 90Y radioembolization and external-beam radiation therapy have been explained by citing differences in absorbed-dose heterogeneity at the microscopic level. We investigated microscopic absorbed-dose heterogeneity in radioembolization as a function of the number of microspheres per unit volume in tumor. The goal was to determine what effect the number of microspheres may have, if any, on tumor control in 90Y radioembolization. Methods: 90Y PET/CT data were combined with microscopic probability-density functions describing microsphere clustering to provide realistic simulation using Monte Carlo modeling on both a macroscopic and a microscopic level. A complete microdosimetric analysis using 100-μm voxels was performed on the basis of 90Y PET/CT data from 19 tumors treated using radioembolization. Simulations were performed with average tumor microsphere-number densities from 200 to 70,000 spheres/mL. Monte Carlo simulations of each tumor and number density were repeated 20 times to establish SE. A 2-way balanced ANOVA was used to determine whether differences in microsphere-number density affected common tumor-dose metrics. Results: Decreasing the microsphere-number density resulted in a decrease in D70, the minimum dose to 70% of the tumor. The slope of the dose-volume histogram also decreased with decreasing microsphere-number density in all tumors. Compared with a density of 50,000 spheres/mL, decreases in D70 were statistically significant below 20,000 spheres/mL. However, these differences are unlikely to have clinical significance until the density decreases to below 5,000 spheres/mL. Although D70 was decreased at a low microsphere-number density, one can compensate for decreases by an increase in the average tumor-absorbed dose, that is, by increasing the radioembolization treatment dose. Conclusion: Differences in microsphere-number density may have an effect on microscopic tumor absorbed-dose inhomogeneity. These results begin to explain differences in treatment planning strategies between glass and resin radioembolization devices.

AB - Differences in maximum tolerable absorbed dose to normal liver between 90Y radioembolization and external-beam radiation therapy have been explained by citing differences in absorbed-dose heterogeneity at the microscopic level. We investigated microscopic absorbed-dose heterogeneity in radioembolization as a function of the number of microspheres per unit volume in tumor. The goal was to determine what effect the number of microspheres may have, if any, on tumor control in 90Y radioembolization. Methods: 90Y PET/CT data were combined with microscopic probability-density functions describing microsphere clustering to provide realistic simulation using Monte Carlo modeling on both a macroscopic and a microscopic level. A complete microdosimetric analysis using 100-μm voxels was performed on the basis of 90Y PET/CT data from 19 tumors treated using radioembolization. Simulations were performed with average tumor microsphere-number densities from 200 to 70,000 spheres/mL. Monte Carlo simulations of each tumor and number density were repeated 20 times to establish SE. A 2-way balanced ANOVA was used to determine whether differences in microsphere-number density affected common tumor-dose metrics. Results: Decreasing the microsphere-number density resulted in a decrease in D70, the minimum dose to 70% of the tumor. The slope of the dose-volume histogram also decreased with decreasing microsphere-number density in all tumors. Compared with a density of 50,000 spheres/mL, decreases in D70 were statistically significant below 20,000 spheres/mL. However, these differences are unlikely to have clinical significance until the density decreases to below 5,000 spheres/mL. Although D70 was decreased at a low microsphere-number density, one can compensate for decreases by an increase in the average tumor-absorbed dose, that is, by increasing the radioembolization treatment dose. Conclusion: Differences in microsphere-number density may have an effect on microscopic tumor absorbed-dose inhomogeneity. These results begin to explain differences in treatment planning strategies between glass and resin radioembolization devices.

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