Positron Emission Tomography-based Dose Painting Radiation Therapy in a Glioblastoma Rat Model using the Small Animal Radiation Research Platform

Summary

Here we present a protocol to perform preclinical positron emission tomography-based radiotherapy in a rat glioblastoma model using algorithms developed in-house to optimize the accuracy and efficiency.

Abstract

A rat glioblastoma model to mimic chemo-radiation treatment of human glioblastoma in the clinic was previously established. Similar to the clinical treatment, computed tomography (CT) and magnetic resonance imaging (MRI) were combined during the treatment-planning process. Positron emission tomography (PET) imaging was subsequently added to implement sub-volume boosting using a micro-irradiation system. However, combining three imaging modalities (CT, MRI, and PET) using a micro-irradiation system proved to be labor-intensive because multimodal imaging, treatment planning, and dose delivery have to be completed sequentially in the preclinical setting. This also results in a workflow that is more prone to human error. Therefore, a user-friendly algorithm to further optimize preclinical multimodal imaging-based radiation treatment planning was implemented. This software tool was used to evaluate the accuracy and efficiency of dose painting radiation therapy with micro-irradiation by using an in silico study design. The new methodology for dose painting radiation therapy is superior to the previously described method in terms of accuracy, time efficiency, and intra- and inter-user variability. It is also an important step towards the implementation of inverse treatment planning on micro-irradiators, where forward planning is still commonly used, in contrast to clinical systems.

Introduction

Glioblastoma (GB) is a malignant and very aggressive primary brain tumor. GB is a solid heterogeneous tumor typically characterized by infiltrative boundaries, nuclear atypia, and necrosis¹. The presence of the blood-brain-barrier and the brain's status as an immune-privileged site makes the discovery of novel targets for chemo- and immunotherapy a daunting task^2,3,4. It is noteworthy that the treatment of GB patients has barely changed since the introduction, in 2005, of the Stupp protocol that combines external beam radiation therapy (RT) with co....

Protocol

The study was approved by the local ethics committee for animal experiments (ECD 18/21). Anesthesia monitoring is performed by acquiring the respiratory rate of the animals using a sensor.

1. F98 GB rat cell model

1. Culture the F98 GB cells in a monolayer using Dulbecco's Modified Eagle Medium, supplemented with 10% calf serum, 1% penicillin, 1% streptomycin, and 1% L-glutamine, and place them in a CO₂ incubator (5% CO₂ and 37 °C).
2. Inoculate the glioma cells into the brain of female Fischer F344 rats (body weight 170 g).
   NOTE: Use sterile instruments and wear sterile gloves at a....

Results

The feasibility of PET- and MRI-guided irradiation in a glioblastoma rat model using the SARRP to mimic the human treatment strategy has been previously described^20,21,22. While the animal was fixed on a multimodality bed made in-house, it was possible to create an acceptable radiation treatment plan combining three imaging modalities: PET, MRI, and CT. In these methods, an external software package (see the Table of Mat.......

Discussion

A rat GB model to mimic the chemo-radiation treatment in the clinic for glioblastoma patients was previously described²⁰. Similar to the clinical method, CT and MRI were combined during the treatment-planning process to obtain more precise irradiation. A multimodality bed to minimize (head) movement was used when the animal was moved from one imaging system to another. Subsequently, PET imaging was added to the treatment-planning process, and PET-based sub-volume boosting could be successfully imp.......

Materials

Name	Company	Catalog Number	Comments
Cell culture
F98 Glioblastoma Cell Line	ATCC	CRL-2397	https://www.lgcstandards-atcc.org/products/all/CRL-2397
Dulbeco's Modified Eagle Medium	Thermo Fisher Scientific	22320-030
Cell culture flasks	Thermo Fisher Scientific	178883	75 cm²
FBS	Thermo Fisher Scientific	10270106
L-Glutamine	Thermo Fisher Scientific	25030-032	200 mM
Penicilline-Streptomycin	Thermo Fisher Scientific	15140-148	10,000 U/mL
Phosphate-Buffered Saline (PBS)	Thermo Fisher Scientific	14040-224
Trypsin-EDTA	Thermo Fisher Scientific	25300-062	0.05%
GB Rat Model
Ball-shaped burr	Foredom	A-228	1.8 mm
Bone Wax	Aesculap	1029754	https://www.aesculapusa.com/en/healthcare-professionals/or-solutions/or-solutions-cranial-closure/hemostatic-bone-wax.html
Ethilon	Ethicon	662G/662H	FS-2, 4-0, 3/8, 19 mm
Fischer F344/Ico crl Rats	Charles River	-
Insulin Syringe Microfine	Beckton-Dickinson	320924	1 mL, 29 G
IR Lamp	Philips	HP3616/01
Meloxicam (Metacam)	Boehringer Ingelheim	-	2 mg/mL
Micromotor rotary tool	Foredom	K.1090-22
Micropump system	Stoelting Co.	53312	Stoelting Stereotaxic Injector
Stereotactic frame	Stoelting Co.	51600
Xylocaine (1%, with adrenaline 1:200,000)	Aspen	-	1%, with adrenaline 1:200,000
Xylocaine gel (2%)	Aspen	-	2%
Animal Irradiation
Micro-irradiator	X-Strahl	SARRP	Version 4.2.0
Software	X-Strahl	Muriplan	Preclinical treatment planning system (PCTPC), version 2.2.2
Small Animal PET
[18F]FET	Inhouse made	-	PET tracer; along with Prohance: MRI/PET agent
Micro-PET	Molecubes	Beta-Cube	https://www.molecubes.com/b-cube/
Small Animal MRI
Micro-MRI	Bruker Biospin	Pharmascan 70/16	https://www.bruker.com/products/mr/preclinical-mri/pharmascan.html
30 G Needle for IV injection	Beckton-Dickinson	305128
PE 10 Tubing	Instech Laboratories Inc	BTPE-10	BTPE-10, polyethylene tubing 0.011 x 0.024 in (0.28 x 60 mm), non sterile, 30 m (98 ft) spool, Instech laboratories, Inc Plymouth meeting PA USA- (800) 443-4227- http://www.instechlabs.com
Prohance contrast agent	Bracco Imaging	-	279.3 mg/mL, gadolinium-contrast agent (along with [18F]FET: MRI/PET agent)
Tx/Rx Rat Brain - Mouse Whole Body Volumecoil	Bruker Biospin	-	40 mm diameter
Water-based Heating Unit	Bruker Biospin	MT0125
Consumables
Isoflurane	Zoetis	B506	Anesthesia
Insulin Syringe Microfine	Beckton-Dickinson	320924	1 mL, 29 G
Image Analysis
MATLAB	Mathworks	-	Version R2019b
PMOD	PMOD technologies LLC		Preclinical and molecular imaging software