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Characterization of Radiation Response of MRI-Guided 3D Conformal Treatment of U251 and 9L Glioblastoma Rat Models Using a Small Animal Radiation Research Platform (SARRP)

G Valadie12*, G Cabral2, S Shadaia2, K Farmer2, S Panda2, N Tavarekere2, I Lee2, R Knight2, M Joiner1, S Brown2, J Ewing2, (1) Wayne State University, Detroit, MI, (2) Henry Ford Health System


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library


The radiation response of two established orthotopic brain tumor models are characterized following procedures that mimic clinical therapy practices.


A total of 72 Fischer 344 rats and 52 RNU athymic rats were implanted with rat 9L and human U251 cells (10^3 cells in 5uL), respectively in equal numbers of males and females. At approximately 9 days for 9L and 18 days for U251, rats were imaged using MRI contrast-enhanced (CE). At 4-5 mm in maximum diameter, tumors were irradiated using a Small Animal Radiation Research Platform (SARRP). Rat orientation was assessed using cone-beam CT and tumor location was co-registered from MRI-CE-T1 images. Treatment planning using MuriPlan software allowed the delivery of four non-coplanar arcs with an identical isocenter located, by eye, at the position of tumor implantation. Tumors were treated to the 80% isodose. Rats were imaged and irradiated under isoflurane anesthesia and warmed via a temperature-controlled cradle. The SARRP operated at 220 kV and 13 mA. With the Cu filter, the effective energy was approximately 70 keV. The resultant dose rate was ~2.5 Gy per minute. Gafchromic film was placed on each animal’s skulls during treatment to confirm radiation was delivered (yes/no). Rats were monitored daily after irradiation for weight loss and behavioral changes. Study endpoint was animal survival (defined as weight loss greater than 20% of the maximum weight).


Radiation treatment isodose and DVHs will be presented. The calculation of the tumor control doses (TCD50) from Kaplan-Meier survival curves are ongoing. To date, a dose of 20 Gy to U251 tumors achieved 60.8% +/- 8.2% survival and 25 Gy to 9L tumors resulted in 40.1% +/- 7.3% survival. No significant difference between males and females was detected.


The radiation response of two reproducible models of human brain response were presented.

Funding Support, Disclosures, and Conflict of Interest: The studies presented were supported by NIH CA218596 (co-P1s: Ewing, Brown)


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