The authors would like to thank Lux Luka Foundation for supporting this work.

The study was approved by the local ethics committee for animal experiments (ECD 18/21).&#160;Anesthesia monitoring is performed by acquiring the respiratory rate of the animals using a sensor.
1. F98 GB rat cell model
<ol>
	<li>Culture the F98 GB cells in a monolayer using Dulbecco&#39;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 &#176;C).</li>
	<li>Inocul...

<ol>
	<li>Louis, D. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+2016+World+Health+Organization+classification+of+tumors+of+the+central+nervous+system:+a+summary.">The 2016 World Health Organization classification of tumors of the central nervous system: a summary.</a> Acta Neuropathologica. 131 (6), 803-820 (2016).</li><li>Wadajkar, A. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumor-targeted+nanotherapeutics:+Overcoming+treatment+barriers+for+glioblastoma.">Tumor-targeted nanotherapeutics: Overcoming treatment barriers for glioblastoma.</a> Wiley Interdisciplinary Reviews. Nanomedicine &amp; Nanobiotechnology. 9 (4), (2016).</li><li>Lim, M., Xia, Y., Bettegowda, C., Weller, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+state+of+immunotherapy+for+glioblastoma.">Current state of immunotherapy for glioblastoma.</a> Nature Reviews. Clinical Oncology. 15 (7), 422 (2018).</li><li>McGranahan, T., Li, G., Nagpal, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=History+and+current+state+of+immunotherapy+in+glioma+and+brain+metastasis.">History and current state of immunotherapy in glioma and brain metastasis.</a> Therapeutic Advances in Medical Oncology. 9 (5), 347-368 (2017).</li><li>Stupp, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radiotherapy+plus+concomitant+and+adjuvant+temozolomide+for+glioblastoma.">Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma.</a> The New England Journal of Medicine. 352 (10), 987-996 (2005).</li><li>Von Neubeck, C., Seidlitz, A., Kitzler, H. H., Beuthien-Baumann, B., Krause, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glioblastoma+multiforme:+Emerging+treatments+and+stratification+markers+beyond+new+drugs.">Glioblastoma multiforme: Emerging treatments and stratification markers beyond new drugs.</a> The British Journal of Radiology. 88 (1053), 20150354 (2015).</li><li>Mann, J., Ramakrishna, R., Magge, R., Wernicke, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+radiotherapy+for+glioblastoma.">Advances in radiotherapy for glioblastoma.</a> Frontiers in Neurology. 8, 748 (2018).</li><li>Ling, C. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+multidimensional+radiotherapy+(MD-CRT):+Biological+imaging+and+biological+conformality.">Towards multidimensional radiotherapy (MD-CRT): Biological imaging and biological conformality.</a> International Journal of Radiation Oncolology, Biology, Physics. 47 (3), 551-560 (2000).</li><li>Bentzen, S. M., Gregoire, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+imaging-based+dose+painting:+a+novel+paradigm+for+radiation+therapy+prescription.">Molecular imaging-based dose painting: a novel paradigm for radiation therapy prescription.</a> Seminars in Radiation Oncology. 21 (2), 101-110 (2011).</li><li>Bentzen, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theragnostic+imaging+for+radiation+oncology:+Dose-painting+by+numbers.">Theragnostic imaging for radiation oncology: Dose-painting by numbers.</a> The Lancet. Oncology. 6 (2), 112-117 (2005).</li><li>Wong, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution,+small+animal+radiation+research+platform+with+X-ray+tomographic+guidance+capabilities.">High-resolution, small animal radiation research platform with X-ray tomographic guidance capabilities.</a> International Journal of Radiation Oncolology, Biology, Physics. 71 (5), 1591-1599 (2008).</li><li>Van Hoof, S. J., Granton, P. V., Verhaegen, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+validation+of+a+treatment+planning+system+for+small+animal+radiotherapy:+SmART-Plan.">Development and validation of a treatment planning system for small animal radiotherapy: SmART-Plan.</a> Radiotherapy and Oncology. 109 (3), 361-366 (2013).</li><li>Verhaegen, F., Granton, P., Tryggestad, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small+animal+radiotherapy+research+platforms.">Small animal radiotherapy research platforms.</a> Physics in Medicine &amp; Biology. 56 (12), 55-83 (2011).</li><li>Butterworth, K. T., Prise, K. M., Verhaegen, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small+animal+image-guided+radiotherapy:+Status,+considerations+and+potential+for+translational+impact.">Small animal image-guided radiotherapy: Status, considerations and potential for translational impact.</a> The British Journal of Radiology. 88 (1045), 20140634 (2015).</li><li>Nasr, A., Habash, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dosimetric+analytic+comparison+of+inverse+and+forward+planned+IMRT+techniques+in+the+treatment+of+head+and+neck+cancer.">Dosimetric analytic comparison of inverse and forward planned IMRT techniques in the treatment of head and neck cancer.</a> Journal of the Egyptian National Cancer Institute. 26 (3), 119-125 (2014).</li><li>Matinfar, M., Iyer, S., Ford, E., Wong, J., Kazanzides, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Image+guided+complex+dose+delivery+for+small+animal+radiotherapy.">Image guided complex dose delivery for small animal radiotherapy.</a> IEEE International Symposium on Biomedical Imaging: From Nano to Macro. , 1243-1246 (2009).</li><li>Matinfar, M., Iordachita, I., Wong, J., Kazanzides, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Robotic+delivery+of+complex+radiation+volumes+for+small+animal+research.">Robotic delivery of complex radiation volumes for small animal research.</a> IEEE International Conference on Robotics and Automation. , 2056-2061 (2010).</li><li>Balvert, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+framework+for+inverse+planning+of+beam-on+times+for+3D+small+animal+radiotherapy+using+interactive+multi-objective+optimisation.">A framework for inverse planning of beam-on times for 3D small animal radiotherapy using interactive multi-objective optimisation.</a> Physics in Medicine &amp; Biology. 60 (14), 5681-5698 (2015).</li><li>Cho, N. B., Wong, J., Kazanzides, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dose+Painting+with+a+Variable+Collimator+for+the+Small+Animal+Radiation+Research+Platform+(SARRP).">Dose Painting with a Variable Collimator for the Small Animal Radiation Research Platform (SARRP).</a> The Midas Journal. , 1-8 (2014).</li><li>Bolcaen, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MRI-guided+3D+conformal+arc+micro-irradiation+of+a+F98+glioblastoma+rat+model+using+the+Small+Animal+Radiation+Research+Platform+(SARRP).">MRI-guided 3D conformal arc micro-irradiation of a F98 glioblastoma rat model using the Small Animal Radiation Research Platform (SARRP).</a> Journal of Neuro-oncology. 120 (2), 257-266 (2014).</li><li>Bolcaen, J., Descamps, B., Boterberg, T., Vanhove, C., Goethals, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PET+and+MRI+guided+irradiation+of+a+glioblastoma+rat+model+using+a+micro-irradiator.">PET and MRI guided irradiation of a glioblastoma rat model using a micro-irradiator.</a> Journal of Visualized Experiments: JoVE. (130), e56601 (2017).</li><li>Verhoeven, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Technical+feasibility+of+[18F]FET+and+[18F]FAZA+PET+guided+radiotherapy+in+a+F98+glioblastoma+rat+model.">Technical feasibility of [18F]FET and [18F]FAZA PET guided radiotherapy in a F98 glioblastoma rat model.</a> Radiation Oncology. 14 (1), 89 (2019).</li><li>Hutterer, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FET+PET:+a+valuable+diagnostic+tool+in+neuro-oncology,+but+not+all+that+glitters+is+glioma.">FET PET: a valuable diagnostic tool in neuro-oncology, but not all that glitters is glioma.</a> Neuro-oncology. 15 (3), 341-351 (2013).</li><li>Stockhammer, F., Plotkin, M., Amthauer, H., Landeghem, F. K. H., Woiciechowsky, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+of+F-18-fluoro-ethyl-tyrosin+uptake+with+vascular+and+cell+density+in+non-contrast-enhancing+gliomas.">Correlation of F-18-fluoro-ethyl-tyrosin uptake with vascular and cell density in non-contrast-enhancing gliomas.</a> Journal of Neuro-oncology. 88 (2), 205-210 (2008).</li><li>. Mricron dicom to nifti converter. neuroimaging informatics tools and resources clearinghouse (nitrc) Available from: <a target="_blank" href="https://www.nitrc.org/projects/mricron">https://www.nitrc.org/projects/mricron</a> (2015)</li><li>. SPM12 Manual Available from: <a target="_blank" href="https://www.fil.ion.ucl.ac.uk/spm/doc/spm12_manual.pdf">https://www.fil.ion.ucl.ac.uk/spm/doc/spm12_manual.pdf</a> (2014)</li><li>Espa&#241;a, S., Marcinkowski, R., Keereman, V., Vandenberghe, S., Van Holen, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DigiPET:+Sub-millimeter+spatial+resolution+small-animal+PET+imaging+using+thin+monolithic+scintillators.">DigiPET: Sub-millimeter spatial resolution small-animal PET imaging using thin monolithic scintillators.</a> Physics in Medicine &amp; Biology. 59 (13), 3405-3420 (2014).</li></ol>

The authors have no conflicts of interest to disclose.

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...

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&#39;s status as an immune-privileged site makes the discovery of novel targets for chemo- and immunotherapy a daunting task2,3,4. 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 concomitant temozolomide, usually followed by adjuvant temozolomide5. Typically, the Stupp protocol is preceded by maximal surgical resection. Therefore, alternative treatment approaches are of pivotal importance.
Current radiation therapy for glioblastoma patients delivers a uniform radiation dose to the defined tumor volume. In radiation oncology, there is an important dose-response correlation for glioblastoma with increasing dose, which seems to cap around 60 Gy, due to increased toxicity to the normal brain6,7. However, tumors can be very (radiobiologically) heterogeneous, with gradients of oxygen level and/or large differences in cellular density. Metabolic imaging techniques, such as PET, can visualize these biological features and can be utilized to customize the dose prescription. This approach is known as dose painting RT. This term was introduced by Ling et al. in 2000. The authors defined dose painting RT as producing &#34;exquisitely conformal dose distributions within the constraints of radiation propagation and scatter&#34;8.
There are two types of dose painting RT, dose painting by contours (DPBC), by which a dose is prescribed to a set of nested sub-volumes, and dose painting by numbers (DPBN), whereby a dose is prescribed at the voxel level. The dose distribution for DPBN RT can be extracted from functional images. The dose in each voxel is determined by the intensity I of the corresponding voxel in the image, with a lower and upper limit, to make sure that, on the one hand, a sufficient dose is delivered to every part of the tumor. On the other hand, doses&#160;do not exceed an upper limit to protect organs at risk and avoid toxicity. The most straightforward method is a linear interpolation (see Eq. 1) between minimum dose&#160;Dmin and maximum dose Dmax, proportionally varying between minimum intensity Imax and maximum intensity within the target volume9,10
<img alt="Equation 1" src="/files/ftp_upload/62560/62560eq01.jpg" />&#160;Eq. 1
Because there is some skepticism about the quality assurance of DPBN RT, the deposition of the dose should be verified through preclinical and clinical research10. However, only limited data can be acquired from clinical trials, and it has been hypothesized that more insights can be obtained by downscaling to laboratory animals11,12. Hence, preclinical studies utilizing precision image-guided radiation research platforms that allow coupling with some very specific techniques, such as autoradiography, are suited for examining open issues and paving the way towards personalized medicine and novel treatment strategies, such as dose painting RT13,14. However, the interpretation of preclinical data must be performed with caution, and drawbacks of these preclinical setups have to be considered14.
Micro-irradiation systems, such as the Small Animal Radiation Research Platform (SARRP), are equipped with similar technologies as their clinical counterpart. They include on-board cone-beam CT (CBCT) imaging, a preclinical treatment-planning system (PCTPS), and provide sub-millimeter precision. Clinical dose calculations are performed by inverse treatment planning, whereby one initiates from the desired dose distribution to determine the beams via an iterative algorithm. Preclinical irradiators often use forward planning. In forward planning, the required amount and angle of the beams are selected, and the PCTPS then calculates the dose distribution. The optimization of the plans is performed by manual iteration, which is labor-intensive15.
After 2009, novel developments have made the implementation of inverse planning on these research platforms possible16,17,18. To increase the similarity with the clinical method, a motorized variable rectangular collimator (MVC) was developed as a preclinical counterpart of the multi-leaf collimator. A two-dimensional dose painting method utilizing a variable collimator was published by Cho et al.19. This research group implemented a three-dimensional (3D) inverse treatment-planning protocol on a micro-irradiator and determined minimum and maximum doses for the target volume and a maximum dose for the organs at risk. These techniques have mainly been evaluated in silico, and their preclinical applications need to be explored.
This paper presents an in silico study to compare two methodologies for [18F]-fluoro-ethyl-L-tyrosine ([18F]FET) PET-based dose painting in a GB rat model20,21,22 using a small animal radiation research platform. These two methodologies are (1) sub-volume boosting using predefined beam sizes and (2) dose painting using a motorized variable collimator where jaw dimensions are modified based on the PET tracer uptake in the tumor volume. [18F]FET is a PET tracer often used in neuro-oncology because of its ability to detect brain tumors23. [18F]FET is an artificial amino acid that is internalized into tumoral cells but not incorporated into cell proteins. [18F]FET uptake corresponds with cell proliferation rate, tumor cell density, and angiogenesis24. As this is the most commonly used oncologic brain PET tracer in these authors&#39; institute, this radiotracer was chosen to evaluate the new workflow.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Cell culture</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>F98 Glioblastoma Cell Line</td>
			<td>ATCC</td>
			<td>CRL-2397</td>
			<td>https://www.lgcstandards-atcc.org/products/all/CRL-2397</td>
		</tr>
		<tr>
			<td>Dulbeco&#39;s Modified Eagle Medium</td>
			<td>Thermo Fisher Scientific</td>
			<td>22320-030</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture flasks</td>
			<td>Thermo Fisher Scientific</td>
			<td>178883</td>
			<td>75 cm&#178;</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>Thermo Fisher Scientific</td>
			<td>10270106</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Thermo Fisher Scientific</td>
			<td>25030-032</td>
			<td>200 mM</td>
		</tr>
		<tr>
			<td>Penicilline-Streptomycin</td>
			<td>Thermo Fisher Scientific</td>
			<td>15140-148</td>
			<td>10,000 U/mL</td>
		</tr>
		<tr>
			<td>Phosphate-Buffered Saline (PBS)</td>
			<td>Thermo Fisher Scientific</td>
			<td>14040-224</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA</td>
			<td>Thermo Fisher Scientific</td>
			<td>25300-062</td>
			<td>0.05%</td>
		</tr>
		<tr>
			<td>GB Rat Model</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ball-shaped burr</td>
			<td>Foredom</td>
			<td>A-228</td>
			<td>1.8 mm</td>
		</tr>
		<tr>
			<td>Bone Wax</td>
			<td>Aesculap</td>
			<td>1029754</td>
			<td>https://www.aesculapusa.com/en/healthcare-professionals/or-solutions/or-solutions-cranial-closure/hemostatic-bone-wax.html</td>
		</tr>
		<tr>
			<td>Ethilon</td>
			<td>Ethicon</td>
			<td>662G/662H</td>
			<td>FS-2, 4-0, 3/8, 19 mm</td>
		</tr>
		<tr>
			<td>Fischer F344/Ico crl Rats</td>
			<td>Charles River</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin Syringe Microfine</td>
			<td>Beckton-Dickinson</td>
			<td>320924</td>
			<td>1 mL, 29 G</td>
		</tr>
		<tr>
			<td>IR Lamp</td>
			<td>Philips</td>
			<td>HP3616/01</td>
			<td></td>
		</tr>
		<tr>
			<td>Meloxicam (Metacam)</td>
			<td>Boehringer Ingelheim</td>
			<td>-</td>
			<td>2 mg/mL</td>
		</tr>
		<tr>
			<td>Micromotor rotary tool</td>
			<td>Foredom</td>
			<td>K.1090-22</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropump system</td>
			<td>Stoelting Co.</td>
			<td>53312</td>
			<td>Stoelting Stereotaxic Injector</td>
		</tr>
		<tr>
			<td>Stereotactic frame</td>
			<td>Stoelting Co.</td>
			<td>51600</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylocaine (1%, with adrenaline 1:200,000)</td>
			<td>Aspen</td>
			<td>-</td>
			<td>1%, with adrenaline 1:200,000</td>
		</tr>
		<tr>
			<td>Xylocaine gel (2%)</td>
			<td>Aspen</td>
			<td>-</td>
			<td>2%</td>
		</tr>
		<tr>
			<td>Animal Irradiation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro-irradiator</td>
			<td>X-Strahl</td>
			<td>SARRP</td>
			<td>Version 4.2.0</td>
		</tr>
		<tr>
			<td>Software</td>
			<td>X-Strahl</td>
			<td>Muriplan</td>
			<td>Preclinical treatment planning system (PCTPC), version 2.2.2</td>
		</tr>
		<tr>
			<td>Small Animal PET</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>[18F]FET</td>
			<td>Inhouse made</td>
			<td>-</td>
			<td>PET tracer; along with Prohance: MRI/PET agent</td>
		</tr>
		<tr>
			<td>Micro-PET</td>
			<td>Molecubes</td>
			<td>Beta-Cube</td>
			<td>https://www.molecubes.com/b-cube/</td>
		</tr>
		<tr>
			<td>Small Animal MRI</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro-MRI</td>
			<td>Bruker Biospin</td>
			<td>Pharmascan 70/16</td>
			<td>https://www.bruker.com/products/mr/preclinical-mri/pharmascan.html</td>
		</tr>
		<tr>
			<td>30 G Needle for IV injection</td>
			<td>Beckton-Dickinson</td>
			<td>305128</td>
			<td></td>
		</tr>
		<tr>
			<td>PE 10 Tubing</td>
			<td>Instech Laboratories Inc</td>
			<td>BTPE-10</td>
			<td>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</td>
		</tr>
		<tr>
			<td>Prohance contrast agent</td>
			<td>Bracco Imaging</td>
			<td>-</td>
			<td>279.3 mg/mL, gadolinium-contrast agent (along with [18F]FET: MRI/PET agent)</td>
		</tr>
		<tr>
			<td>Tx/Rx Rat Brain - Mouse Whole Body Volumecoil</td>
			<td>Bruker Biospin</td>
			<td>-</td>
			<td>40 mm diameter</td>
		</tr>
		<tr>
			<td>Water-based Heating Unit</td>
			<td>Bruker Biospin</td>
			<td>MT0125</td>
			<td></td>
		</tr>
		<tr>
			<td>Consumables</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Zoetis</td>
			<td>B506</td>
			<td>Anesthesia</td>
		</tr>
		<tr>
			<td>Insulin Syringe Microfine</td>
			<td>Beckton-Dickinson</td>
			<td>320924</td>
			<td>1 mL, 29 G</td>
		</tr>
		<tr>
			<td>Image Analysis</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>Mathworks</td>
			<td>-</td>
			<td>Version R2019b</td>
		</tr>
		<tr>
			<td>PMOD</td>
			<td>PMOD technologies LLC</td>
			<td></td>
			<td>Preclinical and molecular imaging software</td>
		</tr>
	</tbody>
</table>

positron emission tomography-based dose painting radiation therapy in a glioblastoma rat model using the small animal radiation research platform

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.

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 described20,21,22. 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...

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

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.

A rat glioblastoma model to mimic chemo-radiation treatment of human glioblastoma in the clinic was previously established. Similar to the clinical ...

The protocol describes an optimized workflow for preclinical PET-based radiotherapy in a rat glioblastoma model using in-house developed algorithms. The optimized approach favors automation and is less time consuming when compared to the previously developed workflow. After anesthetizing an F98 glioblastoma rat harboring a seven to eight millimeter diameter tumor, inject 10 to 12 megabecquerel of fluorine-18 FET dissolved in 200 microliters of saline in the lateral tail vein one hour before PET acquisition.Let the animal regain consciousness while the tracer gets distributed throughout the body. Meanwhile, fix a capillary filled with the MRI PET agent for easier co-registration. Then anesthetize the animal again and place it on a multi-modality bed.Secure the animal using hook and loop fasteners to maintain a fixed position during the imaging and micro-irradiation, then wrap the animal in bubble wrap to preserve its body temperature during the multi-modality imaging and therapy. One hour after the injection of the PET tracer, perform a PET scan. Reconstruct the PET scan into a 3D volume with a 0.4 millimeter voxel size using 30 iterations of the maximum likelihood expectation maximization algorithm.Next, inject an MRI contrast agent into the tail vein, then place the rat still fixed on the multi-modality bed in the animal holder of the MRI scanner. Perform a localizer scan followed by a contrast enhanced T1 weighted spin echo sequence. Then place the animal still fixed on the multi-modality bed on a plastic holder secured onto the four-axis robotic positioning table on the micro-irradiator.Perform a high-resolution treatment planning cone beam CT requiring a total of 360 projections over 360 degrees. Reconstruct the CT images with an isotropic voxel size of 0.275 millimeters. For image co-registration, place the three image modalities into one folder, then import the converted images into MATLAB.Next, run the dose painting co-registration MATLAB script which converts the DICOM images to the NIfTI format, filters the PET image with a one millimeter full width half max Gaussian filter, crops the PET image and moves the image centers close to each other and performs the actual rigid body co-registration using statistical parametric mapping. Evaluate the result of the automatic co-registration before proceeding to treatment planning. To apply method one, run the dose painting radiation planning MATLAB script and load the three different imaging modalities into the MATLAB app.Next, place a generous bounding box around the contrast enhancement on the transverse, sagittal and frontal views of the T1 weighted MRI scan. Save the location of the bounding box, then finalize the box. Determine the contrast enhanced volume using a threshold.If multiple regions have been selected, select only the largest volume, the center of which is considered as the first isocenter to deliver a prescribed dose for radiation therapy. Expand the previously determined MRI contrast enhancement by 10 pixels in each direction. If multiple regions are detected, retain only the largest PET volume, the center of which is considered the second isocenter to deliver a prescribed dose for radiation therapy.For the first isocenter, deliver a prescribed dose of 2, 000 centigray using three non-coplanar arcs at couch positions zero, negative 45 and negative 90 degrees with a gantry rotation of 120, 120, and 60 degrees respectively. Use a fixed collimator size of 10 by 10 millimeters. However, for smaller tumors, use an appropriate size such as five by five millimeters.For the second isocenter, deliver a prescribed dose of 800 centigray using three non-coplanar arcs at couch positions zero, negative 45 and negative 90 degrees with a gantry rotation of 120, 120, and 60 degrees respectively. Use a fixed collimator size of one millimeter. Calculate the dose distribution within the animal and the beam delivery parameters.To apply method two, load the three different imaging modalities into the MATLAB app as demonstrated earlier, then place a generous bounding box around the contrast enhancement on the transverse, sagittal and frontal views of the fluorine-18 FET PET image and save the locations of the bounding box. After finalizing the bounding box, use the appropriate MATLAB script to determine V50, V60, V70, V80, and V90 in the isocenters and the jaw dimensions for each beam required to guide the motorized variable collimator. To deliver a prescribed dose of 2, 000 centigray distributed over 16 beams for V50 and a dose of 800 centigray distributed over 40 beams for V60 to V90, select the output file generated by the MATLAB script and import the 56 beams into the treatment planning software.After verifying that all 56 beams have been imported correctly, calculate the dose distribution within the animal and the beam delivery parameters. Both methods of PET-based dose painting radiation therapy were applied to three different cases. Case one has a spherical homogenous PET uptake while cases two and three have a ring-shaped uptake where the reduced PET uptake is most likely necrotic tissue.The dose volume histograms for method two are systematically closer to the ideal dose distribution than those for method one. A substantial tumor volume receives insufficient irradiation in cases two and three when treated with method one. The D90 and D50 values are considerably lower for method one than for method two.Ideally, Q volume histograms make a sharp drop at a Q value equal to one. Method two always results in dose distributions that are closer to the dose objective than method one. Furthermore, the overall Q factors for method two were superior to those for method one.This methodology is a crucial step towards inverse planning which is generally used in clinical routine and further narrows the gap between preclinical radiation research and the clinic.

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Cancer Research

2.7K visualizações.  Ghent University. O protocolo descreve um fluxo de trabalho otimizado para radioterapia pré-clinical baseada em PET em um modelo de glioblastoma de rato usando algoritmos desenvolvidos internamente. A abordagem otimizada favorece a automação e é menos demorada quando comparada com o fluxo de trabalho previamente desenvolvido. Depois de anestesiar um rato de glioblastoma F98 abrigando um tumor de sete a oito milímetros de diâmetro, injete de 10 a 12 megabecquerel de flúor-18 FET dissolvido em 200 microli...

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