PURPOSE: To develop and test the suitability and performance of a comprehensive quality assurance (QA) phantom for the Small Animal Radiation Research Platform (SARRP). METHODS AND MATERIALS: A QA phantom was developed for carrying out daily, monthly and annual QA...
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Modeling a superficial radiotherapy X-ray source for relative dose calculations
The purpose of this study was to empirically characterize and validate a kilovoltage (kV) X-ray beam source model of a superficial X-ray unit for relative dose calculations in water and assess the accuracy of the British Journal of Radiology Supplement 25 (BJR 25)...
Systematic calibration of an integrated x-ray and optical tomography system for preclinical radiation research
PURPOSE: The cone beam computed tomography (CBCT) guided small animal radiation research platform (SARRP) has been developed for focal tumor irradiation, allowing laboratory researchers to test basic biological hypotheses that can modify radiotherapy outcomes in ways...
Xstrahl introduces RADiant to the European market at ESTRO
Xstrahl Medical will introduce the exciting new Photoelectric Therapy system to the European Market at the start of the 3rd European Society for Radiotherapy and Oncology (ESTRO) forum in Barcelona, Spain on Friday 24th April. Xstrahl (Stand 3700) have worked with clinicians to develop a system that will allow an even greater number of patients to choose this surgery free, non-invasive treatment option.
MRI-Only Based Radiotherapy Treatment Planning for the Rat Brain on a Small Animal Radiation Research Platform (SARRP).
Computed tomography (CT) is the standard imaging modality in radiation therapy treatment planning (RTP). However, magnetic resonance (MR) imaging provides superior soft tissue contrast, increasing the precision of target volume selection. We present MR-only based RTP for a rat brain on a small animal radiation research platform (SARRP) using probabilistic voxel classification with multiple MR sequences. Six rat heads were imaged, each with one CT and five MR sequences. The MR sequences were: T1-weighted, T2-weighted, zero-echo time (ZTE), and two ultra-short echo time sequences with 20 μs (UTE1) and 2 ms (UTE2) echo times. CT data were manually segmented into air, soft tissue, and bone to obtain the RTP reference. Bias field corrected MR images were automatically segmented into the same tissue classes using a fuzzy c-means segmentation algorithm with multiple images as input. Similarities between segmented CT and automatic segmented MR (ASMR) images were evaluated using Dice coefficient. Three ASMR images with high similarity index were used for further RTP. Three beam arrangements were investigated. Dose distributions were compared by analysing dose volume histograms. The highest Dice coefficients were obtained for the ZTE-UTE2 combination and for the T1-UTE1-T2 combination when ZTE was unavailable. Both combinations, along with UTE1-UTE2, often used to generate ASMR images, were used for further RTP. Using 1 beam, MR based RTP underestimated the dose to be delivered to the target (range: 1.4%-7.6%). When more complex beam configurations were used, the calculated dose using the ZTE-UTE2 combination was the most accurate, with 0.7% deviation from CT, compared to 0.8% for T1-UTE1-T2 and 1.7% for UTE1-UTE2. The presented MR-only based workflow for RTP on a SARRP enables both accurate organ delineation and dose calculations using multiple MR sequences. This method can be useful in longitudinal studies where CT’s cumulative radiation dose might contribute to the total dose.
Shandra Gutierrez, Benedicte Descamps, Christian Vanhove
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Stereotactic Radiation Therapy Augments Antigen-Specific PD-1-Mediated Antitumor Immune Responses via Cross-Presentation of Tumor Antigen
The immune-modulating effects of radiotherapy (XRT) have gained considerable interest recently, and there have been multiple reports of synergy between XRT and immunotherapy. However, additional preclinical studies are needed to demonstrate the antigen-specific nature...
MRI-guided 3D conformal arc micro-irradiation of a F98 glioblastoma rat model using the Small Animal Radiation Research Platform (SARRP).
Current glioblastoma (GB) small animal models for cranial radiation therapy (RT) use simple single beam technologies, which differ from the advanced conformal image-guided radiation techniques used in clinical practice. This technological disparity presents a major disadvantage for the development of new therapeutic approaches. Hence, we established a F98 GB rat model using magnetic resonance imaging (MRI)-guided three-dimensional (3D)-conformal arc RT with the Small Animal Radiation Research Platform (SARRP). Ten Fischer rats were inoculated with F98 tumor cells. When the tumor reached a volume of approximately 27 mm(3) on T2-weighted MR images, the animals were randomized into a treatment group (n = 5) receiving RT and concomitant temozolomide, and a sham group (n = 5) receiving control injections. For the treated animals, contrast-enhanced T1-weighted MR images were acquired followed by a cone-beam computed tomography (CBCT) on the SARRP system. Both scans were co-registered; MRI was used to define the target whereas CBCT was used for calculating a dose plan (20 Gy, three non-coplanar arc beams, 3 × 3 mm collimator). Tumor volumes were evaluated on follow-up contrast-enhanced T1-weighted MR images. Verification of treatment accuracy with γH2AX immunohistochemical staining was performed. Tumors in the control animals showed rapid proliferation during follow-up, encompassing almost the entire right cerebral hemisphere at day 12-15. Treated animals showed no significant tumor growth from 2 to 9 days post RT. γH2AX results confirmed the accuracy of dose delivery. This model, which is quite similar to the approach in the clinic, is valid for combined RT and chemotherapy of GB in rats.
Bolcaen J, Descamps B, Deblaere K, Boterberg T, Hallaert G, Van den Broecke C, Decrock E, Vral A, Leybaert L, Vanhove C, Goethals I.
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Positron Emission Tomography for Pre-Clinical Sub-Volume Dose Escalation
PURPOSE: This dissertation focuses on establishment of pre-clinical methods facilitating the use of PET imaging for selective sub-volume dose escalation. Specifically the problems addressed are 1.) The difficulties associated with comparing multiple PET images, 2.)...
PTH1-34 Alleviates Radiotherapy-induced Local Bone Loss by Improving Osteoblast and Osteocyte Survival
Cancer radiotherapy is often complicated by a spectrum of changes in the neighboring bone from mild osteopenia to osteoradionecrosis. We previously reported that parathyroid hormone (PTH, 1–34), an anabolic agent for osteoporosis, reversed bone structural...