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and CTDIvol. The CTDIvol, which was recorded from the scanner console during dose measurements,
ranged from 4.90 mGy to 40.3 mGy. Corresponding lens of the eye dose ranged from 4.21 mGy to 42.8
mGy across all scanners and phantoms. Linear regression analysis of average lens dose and CTDIvol yielded
a slope of 0.974 and a R2 value of 0.935. The lens of the eye dose for pediatric neuroradiology CT protocols
may differ by a factor of 10 with variation between protocols, scanners, and patient age. There was an
excellent linear correlation between lens of the eye radiation dose and CTDIvol for CT scanners from three
different vendors, which suggests an estimation of lens dose could be made from the reported CTDIvol.
This methodology provides an opportunity for a retrospective investigation of radiation dose to the lens
of the eye in pediatric CT scans.
(PS6-29) Neupogen® efficacy in the context of concurrent gastrointestinal and hematopoietic acute
radiation subsyndromes in rhesus macaques. Alexander Bennett; Cheryl Taylor-Howell; Kyle C.
O'Donnell; Ann M. Farese; Cassandra P. Smith; Karl Prado; Allison Gibbs; Kory R. Barrow; Travon A. Baxter;
Sean R. Kearney; Kaitlyn Kieta; Taymin O'Brien; Elisa Swartz; and Thomas J. MacVittie
University of Maryland, Department of Radiation Oncology, Baltimore, MD
A nonhuman primate (NHP) model was developed to assess the effect of Neupogen® on the
morbidity and mortality of acute gastrointestinal radiation syndrome (GI-ARS) and its ability to stimulate
granulopoiesis when administered at increasing intervals between irradiation and treatment initiation.
Randomized NHP (n=48) were exposed to 10 or 11 Gy partial-body irradiation sparing 5% of bone marrow
(PBI/BM5) utilizing 6MV LINAC derived photons at 0.80 Gy/min, myeloablating approximately 95% of BM
and inducing GI-ARS. All NHP received medical management. NHP were dosed daily with control article
(CA) initiated on day (d) 1 post-exposure or Neupogen® (test article [TA]) (10 µg/kg) initiated on d1, d3,
or d5 until recovery (absolute neutrophil count [ANC] > 1000/µL for 3 consecutive days). The respective
mortality due to GI-ARS at d15 in the 10 Gy CA and TA cohorts starting on d1 or d3 was 0%, 20%, and 0%.
The overall mortality in the TA cohort was 13% (2/15). The mortality at d15 in the 11 Gy CA and TA cohorts
starting on d1, d3, or d5 was 14%, 20%, 0%, and 0% respectively. This is approximate to the respective
mortalities of 10% (10 Gy) and 15% (11 Gy), previously observed in the PBI/BM5 model. These data
suggest that Neupogen® does not affect GI-ARS lethality. The ability of Neupogen® to stimulate
granulopoiesis was assessed by evaluating the duration of neutropenia (ANC<500/µL) and recovery time.
Historical controls (n=24) were included in this analysis. The duration of neutropenia was 13d in the 10
Gy CA cohort, versus 4 and 6d in the d1 and d3 TA cohorts, respectively. The respective ANC nadirs were
91/µL, 220/µL, and 243/µL for the CA and d1 and d3 TA cohorts. Recovery time was 22d for CA, versus 8d
(TA d1) and 11d (TA d3). The duration of neutropenia was 13d in the 11 Gy CA cohort, versus 3d, 4d, and
4d in the d1, d3, and d5 TA cohorts, respectively. The respective ANC nadirs for the CA, and d1, d3, and
d5 TA cohorts were 112/µL, 292/µL, 236/µL, and 226/µL. ANC recovery time was 20d for CA, compared
to 8d (TA d1), 9d (TA d3), and 10d (TA d5). The acceleration of granulopoiesis by Neupogen® in this model
is independent of the time interval between radiation exposure and treatment initiation up to 5d. The
PBI/BM5 model can be used to assess medical countermeasure efficacy in the context of the concurrent
GI and hematopoietic ARS. Supported by HHSN272201000046C.
340 | P a g e
ranged from 4.90 mGy to 40.3 mGy. Corresponding lens of the eye dose ranged from 4.21 mGy to 42.8
mGy across all scanners and phantoms. Linear regression analysis of average lens dose and CTDIvol yielded
a slope of 0.974 and a R2 value of 0.935. The lens of the eye dose for pediatric neuroradiology CT protocols
may differ by a factor of 10 with variation between protocols, scanners, and patient age. There was an
excellent linear correlation between lens of the eye radiation dose and CTDIvol for CT scanners from three
different vendors, which suggests an estimation of lens dose could be made from the reported CTDIvol.
This methodology provides an opportunity for a retrospective investigation of radiation dose to the lens
of the eye in pediatric CT scans.
(PS6-29) Neupogen® efficacy in the context of concurrent gastrointestinal and hematopoietic acute
radiation subsyndromes in rhesus macaques. Alexander Bennett; Cheryl Taylor-Howell; Kyle C.
O'Donnell; Ann M. Farese; Cassandra P. Smith; Karl Prado; Allison Gibbs; Kory R. Barrow; Travon A. Baxter;
Sean R. Kearney; Kaitlyn Kieta; Taymin O'Brien; Elisa Swartz; and Thomas J. MacVittie
University of Maryland, Department of Radiation Oncology, Baltimore, MD
A nonhuman primate (NHP) model was developed to assess the effect of Neupogen® on the
morbidity and mortality of acute gastrointestinal radiation syndrome (GI-ARS) and its ability to stimulate
granulopoiesis when administered at increasing intervals between irradiation and treatment initiation.
Randomized NHP (n=48) were exposed to 10 or 11 Gy partial-body irradiation sparing 5% of bone marrow
(PBI/BM5) utilizing 6MV LINAC derived photons at 0.80 Gy/min, myeloablating approximately 95% of BM
and inducing GI-ARS. All NHP received medical management. NHP were dosed daily with control article
(CA) initiated on day (d) 1 post-exposure or Neupogen® (test article [TA]) (10 µg/kg) initiated on d1, d3,
or d5 until recovery (absolute neutrophil count [ANC] > 1000/µL for 3 consecutive days). The respective
mortality due to GI-ARS at d15 in the 10 Gy CA and TA cohorts starting on d1 or d3 was 0%, 20%, and 0%.
The overall mortality in the TA cohort was 13% (2/15). The mortality at d15 in the 11 Gy CA and TA cohorts
starting on d1, d3, or d5 was 14%, 20%, 0%, and 0% respectively. This is approximate to the respective
mortalities of 10% (10 Gy) and 15% (11 Gy), previously observed in the PBI/BM5 model. These data
suggest that Neupogen® does not affect GI-ARS lethality. The ability of Neupogen® to stimulate
granulopoiesis was assessed by evaluating the duration of neutropenia (ANC<500/µL) and recovery time.
Historical controls (n=24) were included in this analysis. The duration of neutropenia was 13d in the 10
Gy CA cohort, versus 4 and 6d in the d1 and d3 TA cohorts, respectively. The respective ANC nadirs were
91/µL, 220/µL, and 243/µL for the CA and d1 and d3 TA cohorts. Recovery time was 22d for CA, versus 8d
(TA d1) and 11d (TA d3). The duration of neutropenia was 13d in the 11 Gy CA cohort, versus 3d, 4d, and
4d in the d1, d3, and d5 TA cohorts, respectively. The respective ANC nadirs for the CA, and d1, d3, and
d5 TA cohorts were 112/µL, 292/µL, 236/µL, and 226/µL. ANC recovery time was 20d for CA, compared
to 8d (TA d1), 9d (TA d3), and 10d (TA d5). The acceleration of granulopoiesis by Neupogen® in this model
is independent of the time interval between radiation exposure and treatment initiation up to 5d. The
PBI/BM5 model can be used to assess medical countermeasure efficacy in the context of the concurrent
GI and hematopoietic ARS. Supported by HHSN272201000046C.
340 | P a g e
