Browsing by Author "DesRosiers, Colleen"
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Item Challenges of dosimetry of ultra-short pulsed very high energy electron beams(Elsevier, 2017-10-01) Subiel, Anna; Moskvin, Vadim; Welsh, Gregor H.; Cipiccia, Silvia; Reboredo, David; DesRosiers, Colleen; Jaroszynski, Dino A.; Radiation Oncology, School of MedicineVery high energy electrons (VHEE) in the range from 100 to 250MeV have the potential of becoming an alternative modality in radiotherapy because of their improved dosimetric properties compared with 6–20MV photons generated by clinical linear accelerators (LINACs). VHEE beams have characteristics unlike any other beams currently used for radiotherapy: femtosecond to picosecond duration electron bunches, which leads to very high dose per pulse, and energies that exceed that currently used in clinical applications. Dosimetry with conventional online detectors, such as ionization chambers or diodes, is a challenge due to non-negligible ion recombination effects taking place in the sensitive volumes of these detectors. FLUKA and Geant4 Monte Carlo (MC) codes have been employed to study the temporal and spectral evolution of ultrashort VHEE beams in a water phantom. These results are complemented by ion recombination measurements employing an IBA CC04 ionization chamber for a 165MeV VHEE beam. For comparison, ion recombination has also been measured using the same chamber with a conventional 20MeV electron beam. This work demonstrates that the IBA CC04 ionization chamber exhibits significant ion recombination and is therefore not suitable for dosimetry of ultrashort pulsed VHEE beams applying conventional correction factors. Further study is required to investigate the applicability of ion chambers in VHEE dosimetry.Item Genetic Variations in the Transforming Growth Factor-β1 Pathway May Improve Predictive Power for Overall Survival in Non-small Cell Lung Cancer(Frontiers Media, 2021-07-07) Zhang, Hong; Wang, Weili; Pi, Wenhu; Bi, Nan; DesRosiers, Colleen; Kong, Fengchong; Cheng, Monica; Monica, Li; Yang, Li; Lautenschlaeger, Tim; Jolly, Shruti; Jin, Jianyue; Kong, Feng-Ming (Spring); Radiation Oncology, School of MedicinePurpose: Transforming growth factor-β1 (TGF-β1), a known immune suppressor, plays an important role in tumor progression and overall survival (OS) in many types of cancers. We hypothesized that genetic variations of single nucleotide polymorphisms (SNPs) in the TGF-β1 pathway can predict survival in patients with non-small cell lung cancer (NSCLC) after radiation therapy. Materials and Methods: Fourteen functional SNPs in the TGF-β1 pathway were measured in 166 patients with NSCLC enrolled in a multi-center clinical trial. Clinical factors, including age, gender, ethnicity, smoking status, stage group, histology, Karnofsky Performance Status, equivalent dose at 2 Gy fractions (EQD2), and the use of chemotherapy, were first tested under the univariate Cox's proportional hazards model. All significant clinical predictors were combined as a group of predictors named "Clinical." The significant SNPs under the Cox proportional hazards model were combined as a group of predictors named "SNP." The predictive powers of models using Clinical and Clinical + SNP were compared with the cross-validation concordance index (C-index) of random forest models. Results: Age, gender, stage group, smoking, histology, and EQD2 were identified as significant clinical predictors: Clinical. Among 14 SNPs, BMP2:rs235756 (HR = 0.63; 95% CI:0.42-0.93; p = 0.022), SMAD9:rs7333607 (HR = 2.79; 95% CI 1.22-6.41; p = 0.015), SMAD3:rs12102171 (HR = 0.68; 95% CI: 0.46-1.00; p = 0.050), and SMAD4: rs12456284 (HR = 0.63; 95% CI: 0.43-0.92; p = 0.016) were identified as powerful predictors of SNP. After adding SNP, the C-index of the model increased from 84.1 to 87.6% at 24 months and from 79.4 to 84.4% at 36 months. Conclusion: Genetic variations in the TGF-β1 pathway have the potential to improve the prediction accuracy for OS in patients with NSCLC.Item Histology, Tumor Volume, and Radiation Dose Predict Outcomes in NSCLC Patients After Stereotactic Ablative Radiotherapy(Elsevier, 2018) Shiue, Kevin; Cerra-Franco, Alberto; Shapiro, Ronald; Estabrook, Neil; Mannina, Edward M.; Deig, Christopher R.; Althouse, Sandra; Liu, Sheng; Wan, Jun; Zang, Yong; Agrawal, Namita; Ioannides, Pericles; Liu, Yongmei; Zhang, Chen; DesRosiers, Colleen; Bartlett, Greg; Ewing, Marvene; Langer, Mark P.; Watson, Gordon; Zellars, Richard; Kong, Feng-Ming; Lautenschlaeger, Tim; Radiation Oncology, School of MedicineIntroduction It remains unclear if histology should be independently considered when choosing stereotactic ablative body radiotherapy dose prescriptions for NSCLC. Methods The study population included 508 patients with 561 lesions between 2000 and 2016, of which 442 patients with 482 lesions had complete dosimetric information. Eligible patients had histologically or clinically diagnosed early-stage NSCLC and were treated with 3 to 5 fractions. The primary endpoint was in-field tumor control censored by either death or progression. Involved lobe control was also assessed. Results At 6.7 years median follow-up, 3-year in-field control, involved lobe control, overall survival, and progression-free survival rates were 88.1%, 80.0%, 49.4%, and 37.2%, respectively. Gross tumor volume (GTV) (hazard ratio [HR] = 1.01 per mL, p = 0.0044) and histology (p = 0.0225) were independently associated with involved lobe failure. GTV (HR = 1.013, p = 0.001) and GTV dose (cutoff of 110 Gy, biologically effective dose with α/β = 10 [BED10], HR = 2.380, p = 0.0084) were independently associated with in-field failure. For squamous cell carcinomas, lower prescription doses were associated with worse in-field control (12 Gy × 4 or 10 Gy × 5 versus 18 Gy or 20 Gy × 3: HR = 3.530, p = 0.0447, confirmed by propensity score matching) and was independent of GTV (HR = 1.014 per mL, 95% confidence interval: 1.005–1.022, p = 0.0012). For adenocarcinomas, there were no differences in in-field control observed using the above dose groupings (p = 0.12 and p = 0.31, respectively). Conclusions In the absence of level I data, GTV and histology should be considered to personalize radiation dose for stereotactic ablative body radiotherapy. We suggest lower prescription doses (i.e., 12 Gy × 4 or 10 G × 5) should be avoided for squamous cell carcinomas if normal tissue tolerances are met.Item Laser-plasma generated very high energy electrons (VHEEs) in radiotherapy(SPIE, 2017-05) Kokurewicz, Karolina; Welsh, G. H.; Brunetti, E.; Wiggins, S. Mark; Boyd, M.; Sorensen, A.; Chalmers, A.; Schettino, G.; Subiel, Anna; DesRosiers, Colleen; Jaroszynski, Dino A.; Radiation Oncology, School of MedicineAs an alternative modality to conventional radiotherapy, electrons with energies above 50 MeV penetrate deeply into tissue, where the dose can be absorbed within a tumour volume with a relatively small penumbra. We investigate the physical properties of VHEEs and review the state-of-the-art in treatment planning and dosimetry. We discuss the advantages of using a laser wake eld accelerator (LWFA) and present the characteristic features of the electron bunch produced by the LWFA and compare them with that from a conventional linear accelerator.Item Very High Energy Electron Laser Plasma Accelerators for use in Radiotherapy(Office of the Vice Chancellor for Research, 2010-04-09) DesRosiers, Colleen; Moskvin, Vadim; Stewart, KeithVery high energy electron beams, greater than 150 MeV, have been shown to have potential benefit in radiotherapy applications. Laser plasma technology is a highly efficient electron accelerator and this technology may be used to design an optimal radiotherapy accelerator.Item VMAT partial arc technique decreases dose to organs at risk in whole pelvic radiotherapy for prostate cancer when compared to full arc VMAT and IMRT(Elsevier, 2023-03) Bartlett, Gregory K.; Njeh, Christopher F.; Huang, Ke C.; DesRosiers, Colleen; Guo, Gordon; Radiation Oncology, School of MedicineWhole pelvic radiotherapy (WPRT) can sterilize microscopic lymph node metastases in treatment of prostate cancer. WPRT, compared to prostate only radiotherapy (PORT), is associated with increased acute gastrointestinal, and hematological toxicities. To further explore minimizing normal tissue toxicities associated with WPRT in definitive IMRT for prostate cancer, this planning study compared dosimetric differences between static 9-field-IMRT, full arc VMAT, and mixed partial-full arc VMAT techniques. In this retrospective study, 12 prostate cancer patients who met the criteria for WPRT were randomly selected for this study. The initial volume, PTV46, included the prostate, seminal vesicles, and pelvic nodes with margin and was prescribed to 4600 cGy. The cone-down volume, PTV78, included the prostate and proximal seminal vesicles with margin to a total dose of 7800 cGy. For each CT image set, 3 plans were generated for each of the PTVs: an IMRT plan, a full arc (FA) VMAT plan, and a mixed partial-full arc (PFA) VMAT plan, using 6MV photons energy. According to RTOG protocols none of the plans had a major Conformity Index (CI) violation by any of the 3 planning techniques. PFA plan had the best mean CI index of 1.00 and significantly better than IMRT ( p = 0.03) and FA ( p = 0.007). For equivalent PTV coverage, the average composite gradient index of the PFA plans was better than the IMRT and the FA plans with values 1.92, 2.03, and 2.01 respectively. The difference was statistically significant between PFA/IMRT and PFA/FA, with p - values of < 0.001. The IMRT plans and the PFA plans provided very similar doses to the rectum, bladder, sigmoid colon, and femoral heads, which were lower than the dose in the FA plans. There was a significant decrease in the mean dose to the rectum from 4524 cGy with the FA to 4182 cGy with the PFA and 4091 cGy with IMRT ( p < 0.001). The percent of rectum receiving 4000 cGy was also the highest with FA at 66.1% compared to 49.9% (PFA) and 47.5% (IMRT). There was a significant decrease in the mean dose to the bladder from 3922 cGy (FA) to 3551 cGy (PFA) and 3612 cGy (IMRT) ( p < 0.001). The percent of bladder receiving 4000 cGy was also the highest with FA at 45.4% compared to 36.6% (PFA) and 37.4% (IMRT). The average mean dose to the sigmoid colon decreased from 4177 cGy (FA) to 3893 cGy (PFA) and 3819 cGy (IMRT). The average mean dose to the femoral heads decreased from 2091 cGy (FA) to 2026 cGy (PFA) and 1987 cGy (IMRT). Considering the improvement in plan quality indices recorded in this study including the dose gradient and the dose to organs at risk, mixed partial-full arc plans may be the preferred VMAT treatment technique over full arc plans for prostate cancer treatments that include nodal volumes.