- Browse by Date Submitted
Department of Radiation Oncology Works
Permanent URI for this collection
Browse
Browsing Department of Radiation Oncology Works by browse.metadata.dateaccessioned
Now showing 1 - 10 of 186
Results Per Page
Sort Options
Item Characterization of a new commercial single crystal diamond detector for photon- and proton-beam dosimetry(Oxford, 2015-08) Akinio, Yuichi; Gautam, Archana; Coutinho, Len; Würfel, Jan; Das, Indra J.; Department of Radiation Oncology, IU School of MedicineA synthetic single crystal diamond detector (SCDD) is commercially available and is characterized for radiation dosimetry in various radiation beams in this study. The characteristics of the commercial SCDD model 60019 (PTW) with 6- and 15-MV photon beams, and 208-MeV proton beams, were investigated and compared with the pre-characterized detectors: Semiflex (model 31010) and PinPoint (model 31006) ionization chambers (PTW), the EDGE diode detector (Sun Nuclear Corp) and the SFD Stereotactic Dosimetry Diode Detector (IBA). To evaluate the effects of the pre-irradiation, the diamond detector, which had not been irradiated on the day, was set up in the water tank, and the response to 100 MU was measured every 20 s. The depth–dose and profiles data were collected for various field sizes and depths. For all radiation types and field sizes, the depth–dose data of the diamond chamber showed identical curves to those of the ionization chambers. The profile of the diamond detector was very similar to those of the EDGE and SFD detectors, although the Semiflex and PinPoint chambers showed volume-averaging effects in the penumbrae region. The temperature dependency was within 0.7% in the range of 4–41°C. A dose of 900 cGy and 1200 cGy was needed to stabilize the chamber to the level within 0.5% and 0.2%, respectively. The PTW type 60019 SCDD detector showed suitable characteristics for radiation dosimetry, for relative dose, depth–dose and profile measurements for a wide range of field sizes. However, at least 1000 cGy of pre-irradiation will be needed for accurate measurements.Item Biological Dose Estimation Model for Proton Beam Therapy(Scientific Research, 2015-05) Anferov, Vladimir; Das, Indra J.; Department of Radiation Oncology, IU School of MedicinePurpose: The recommended value for the relative biological effectiveness (RBE) of proton beams is currently assumed to be 1.1. However, there is increasing evidence that RBE increases towards the end of proton beam range that may increase the biological effect of proton beam in the distal regions of the dose deposition. Methods: A computational approach is presented for estimating the biological effect of the proton beam. It includes a method for calculating the dose averaged linear energy transfer (LET) along the measured Bragg peak and published LET to RBE conversion routine. To validate the proposed method, we have performed Monte Carlo simulations of the pristine Bragg peak at various beam energies and compared the analysis with the simulated results. A good agreement within 5% is observed between the LET analysis of the modeled Bragg peaks and Monte Carlo simulations. Results: Applying the method to the set of Bragg peaks measured at a proton therapy facility we have estimated LET and RBE values along each Bragg peak. Combining the individual RBE-weighted Bragg peaks with known energy modulation weights we have calculated the RBE-weighted dose in the modulated proton beam. The proposed computational method provides a tool for calculating dose averaged LET along the measured Bragg peak. Conclusions: Combined with a model to convert LET into RBE, this method enables calculation of RBE-weighted dose both in pristine Bragg peak and in modulated beam in proton therapy.Item Dosimetric Comparison of Treatment Techniques: Brachytherapy, Intensity- Modulated Radiation Therapy, and Proton Beam in Partial Breast Irradiation(2015) Hansen, Tara M.; Bartlett, Gregory K.; Mannina, Edward M. Jr.; Srivastava, Shiv P.; Cox, John A.; Das, Indra J.; Department of Radiation Oncology, IU School of MedicinePurpose: To perform a dosimetric comparison of 3 accelerated partial breast irradiation techniques: catheter-based brachytherapy (BT), intensity-modulated radiation therapy (IMRT), and proton beam therapy (PBT). Patients and Methods: Twelve patients with left-sided breast cancer treated with SAVI (Strut-Adjusted Volume Implant) were selected in this study. The original BT plans were compared with optimum plans using IMRT and PBT for 34 Gy (RBE) with 1.1 RBE in 10 fractions using identical parameters for target and organs at risk. Results: Significant reduction in maximum dose to the ipsilateral breast was observed with PBT and IMRT (mean 108.58% [PBT] versus 107.78% [IMRT] versus 2194.43% [BT], P = .001 for both PBT and IMRT compared to BT). The mean dose to the heart was 0%, 1.38%, and 3.85%, for PBT, IMRT, and BT, respectively (P < .001 and P = .026). The chest wall mean dose was 10.07%, 14.65%, and 29.44% for PBT, IMRT, and BT, respectively (P = .001 and .013 compared to BT). The PBT was superior in reducing the mean ipsilateral lung dose (mean 0.04% versus 2.13% versus 5.4%, P = .025 and P < .001). There was no statistically significant difference in the maximum dose to the ipsilateral lung, chest wall, 3-mm skin rind or in the mean ipsilateral breast V50% among the 3 techniques (P = .168, .405, .067, and .780, respectively). PBT exhibited the greatest mean dose homogeneity index of 4.75 compared to 7.18 for IMRT (P = .001) and 195.82 for BT (P < .001). All techniques resulted in similar dose conformality (P = .143). Conclusion: This study confirms the dosimetric feasibility of PBT and IMRT to lower dose to organs at risk while still maintaining high target dose conformality. Though the results of this comparison are promising, continued clinical research is needed to better define the role of PBT and IMRT in the accelerated partial breast irradiation treatment of early-stage breast cancer.Item Invasive adenoma and pituitary carcinoma: a SEER database analysis(Springer, 2014-04) Hansen, Tara M.; Batra, Sachin; Lim, Michael; Gallia, Gary L.; Burger, Peter C.; Salvatori, Roberto; Wand, Gary; Quinones-Hinojosa, Alfredo; Kleinberg, Lawrence; Redmond, Kristin J.; Department of Radiation Oncology, IU School of MedicineInvasive pituitary adenomas and pituitary carcinomas are clinically indistinguishable until identification of metastases. Optimal management and survival outcomes for both are not clearly defined. The purpose of this study is to use the Surveillance, Epidemiology, and End Results (SEER) database to report patterns of care and compare survival outcomes in a large series of patients with invasive adenomas or pituitary carcinomas. One hundred seventeen patients diagnosed between 1973 and 2008 with pituitary adenomas/adenocarcinomas were included. Eighty-three invasive adenomas and seven pituitary carcinomas were analyzed for survival outcomes. Analyzed prognostic factors included age, sex, race, histology, tumor extent, and treatment. A significant decrease in survival was observed among carcinomas compared to invasive adenomas at 1, 2, and 5 years (p=0.047, 0.001, and 0.009). Only non-white race, male gender, and age ≥65 were significant negative prognostic factors for invasive adenomas (p=0.013, 0.033, and <0.001, respectively). There was no survival advantage to radiation therapy in treating adenomas at 5, 10, 20, or 30 years (p=0.778, 0.960, 0.236, and 0.971). In conclusion, pituitary carcinoma patients exhibit worse overall survival than invasive adenoma patients. This highlights the need for improved diagnostic methods for the sellar phase to allow for potentially more aggressive treatment approaches.Item Monitoring the Effects of Anti-angiogenesis on the Radiation Sensitivity of Pancreatic Cancer Xenografts Using Dynamic Contrast-Enhanced CT(Elsevier, 2014-02-01) Cao, Ning; Cao, Minsong; Chin-Sinex, Helen; Mendonca, Marc; Ko, Song-Chu; Stantz, Keith M; Department of Radiation Oncology, IU School of MedicinePurpose To image the intra-tumor vascular physiological status of pancreatic tumors xenografts and their response to anti-angiogenic therapy using Dynamic Contrast-Enhanced CT (DCE-CT), and to identify parameters of vascular physiology associated with tumor X-ray sensitivity following anti-angiogenic therapy. Methods and Materials Nude mice bearing human BxPC-3 pancreatic tumor xenografts were treated with 5Gy of radiation therapy (RT), either a low-dose (40mg/kg) or a high-dose (150mg/kg) of DC101, the anti-VEGF receptor-2 anti-angiogenesis antibody, or with combination of low or high dose DC101 and 5Gy RT (DC101-plus-RT). DCE-CT scans were longitudinally acquired over three week period post-DC101 treatment. Parametric maps of tumor perfusion and fractional plasma volume (Fp) were calculated and their averaged values and histogram distributions evaluated and compared to controls, from which a more homogeneous physiological window was observed 1-week post-DC101. Mice receiving a combination of DC101-plus-RT(5Gy) were imaged baseline prior to receiving DC101 and 1-week after DC101 (prior to RT). Changes in perfusion and Fp were compared with alternation in tumor growth delay for RT and DC101-plus-RT(5Gy) treated tumors. Results Pretreatment with low or high doses of DC101 prior to RT significantly delayed tumor growth by an average 7.9 days compared to RT alone (p≤0.01). The increase in tumor growth delay for the DC101-plus-RT treated tumors was strongly associated with changes in tumor perfusion (ΔP>−15%) compared to RT treated tumors alone (p=0.01). In addition, further analysis revealed a trend linking the tumor’s increased growth delay to its tumor volume-to-DC101 dose ratio. Conclusions DCE-CT is capable of monitoring changes in intra-tumor physiological parameter of tumor perfusion in response to anti-angiogenic therapy of a pancreatic human tumor xenograft that was associated with enhanced radiation response.Item Radiation therapy in the last month of life(Elsevier, 2013-10-16) Patel, Anand; Dunmore-Griffith, Jacquelyn; Lutz, Stephen; Johnstone, Peter A.S.; Department of Radiation Oncology, IU School of MedicineAim We sought to survey a large, multi-center patient sample to better characterize/quantify RT utilization at the end of life. Background Few objective data exist for radiation therapy (RT) delivery at end of life (EOL). Materials and methods Data were retrieved for all patients receiving RT in calendar year 2010 in the Department of Radiation Oncology at Indiana University (IU) and Howard University (HU) hospitals. Specific attention was made of the group of patients receiving RT in the last 30 days of life. Results A total of 852 patients received all or part of their RT during 2010 (HU: 139, IU: 713). At time of analysis in early 2012, 179 patients had died (21%). Fifty-four patients (6.3% of total; 30% of expired patients) died within 30 days of receiving their last treatment. Twenty patients (2.3% of total; 11.2% of expired patients) received RT within their last week of life. For both sites, the median time until death from completion of therapy was 12.5 days (range 2–30 days). Conclusions Radiation in the last month of life is likely to provide minimal palliation or survival benefit. This, coupled with the financial implications, time investment, and physical costs, suggests that physicians and patients should more strongly consider hospice, and minimize duration of palliative RT courses as far as possible. As with chemotherapy, RT utilization at EOL should be considered for collection as an overuse metric.Item Proton therapy for atypical meningiomas(Springer, 2015-05) McDonald, Mark W.; Plankenhorn, David A.; McMullen, Kevin P.; Henderson, Mark A.; Dropcho, Edward J.; Shah, Mitesh V.; Cohen-Gadol, Aaron A.; Department of Radiation Oncology, IU School of MedicineWe report clinical outcomes of proton therapy in patients with World Health Organization grade 2 (atypical) meningiomas. Between 2005 and 2013, 22 patients with atypical meningiomas were treated to a median dose of 63 Gy (RBE) using proton therapy, as an adjuvant therapy after surgery (n = 12) or for recurrence or progression of residual tumor (n = 10). Six patients had presumed radiation-induced meningiomas, but none had received prior radiotherapy for their meningioma. The median follow-up time after radiation was 39 months (range 7–104) and all patients remain alive at last follow-up. The 5-year estimate of local control was 71.1 % (95 % CI 49.3–92.9 %). The 5-year estimate of local control was 87.5 % following a radiation dose >60 Gy (RBE), compared to 50.0 % for ≤60 Gy (RBE) (p = 0.038). The 5-year estimate of neuraxis dissemination was 5 % (95 % CI 0–14.6 %) and 6.2 % (95 % CI 0–18.2 %) for metastases outside of the central nervous system. Radiation necrosis was observed in one patient with a history of prior cranial irradiation. Fractionated proton therapy was associated with favorable tumor control rates for grade 2 meningiomas. Prospective studies are needed to define the optimal radiation dose for high-grade meningiomas.Item Resection of a Catecholamine-Elaborating Retroperitoneal Paraganglioma Invading the Inferior Vena Cava(Hindawi Publishing Corporation, 2014-12-28) Mannina, E. M.; Xiong, Z.; Self, R.; Kandil, E.; Department of Radiation Oncology, IU School of MedicineParagangliomas are rare tumors originating outside of the adrenal medulla which can be associated with catecholamine secretion or mass effect, one of which typically leads to their discovery. The differences between these tumors and traditional intra-adrenal pheochromocytomas are a subject of recent investigations. Standard of care therapy is medical management and surgical resection of the tumor. When tumors are biochemically active, medical optimization of the autonomic nervous system is a critical component to a safe, definitive resection. Tumors arising in the retroperitoneum present technical challenges for the surgeon as they are often large and difficult to access, making an oncologic resection much more difficult. Lastly, these tumors are mostly benign and rarely invade adjacent structures—an operative finding not always predicted by preoperative imaging—which, if present, adds significant complexity and risk to the resection. A case illustrating these challenges in the management of a biochemically active retroperitoneal paraganglioma invading the inferior vena cava follows.Item Why Does Treatment Fidelity Matter?(2015-07) Stone, Jennifer A. M.; Department of Radiation Oncology, IU School of MedicineTreatment fidelity is a relatively new concept in intervention research and has been discussed in scientific literature only in the last 25 y. Intervention fidelity improves power by reducing unintended variability in treatment effect, and it supports external validity by allowing for replication. As more self-administered complementary and alternative medicine (CAM) treatments are being studied, the issue of fidelity concerns is becoming more of a burden to researchers. Despite the critical role of fidelity, no comprehensive, structured guide exists.Item Dose perturbation effect of metallic spinal implants in proton beam therapy(2015) Jia, Yingcui; Zhao, Li; Cheng, Chee-Wei; McDonald, Mark W.; Das, Indra J.; Department of Radiation Oncology, IU School of MedicineThe purpose of this study was to investigate the effect of dose perturbations for two metallic spinal screw implants in proton beam therapy in the perpendicular and parallel beam geometry. A 5.5 mm (diameter) by 45 mm (length) stainless steel (SS) screw and a 5.5 mm by 35 mm titanium (Ti) screw commonly used for spinal fixation were CT-scanned in a hybrid phantom of water and solid water. The CT data were processed with an orthopedic metal artifact reduction (O-MAR) algorithm. Treatment plans were generated for each metal screw with a proton beam oriented, first parallel and then perpendicular, to the longitudinal axis of the screw. The calculated dose profiles were compared with measured results from a plane-parallel ion chamber and Gafchromic EBT2 films. For the perpendicular setup, the measured dose immediately downstream from the screw exhibited dose enhancement up to 12% for SS and 8% for Ti, respectively, but such dose perturbation was not observed outside the lateral edges of the screws. The TPS showed 5% and 2% dose reductions immediately at the interface for the SS nd Ti screws, respectively, and up to 9% dose enhancements within 1 cm outside of the lateral edges of the screws. The measured dose enhancement was only observed within 5 mm from the interface along the beam path. At deeper depths, the lateral dose profiles appeared to be similar between the measurement and TPS, with dose reduction in the screw shadow region and dose enhancement within 1–2 cm outside of the lateral edges of the metals. For the parallel setup, no significant dose perturbation was detected at lateral distance beyond 3 mm away from both screws. Significant dose discrepancies exist between TPS calculations and ion chamber and film measurements in close proximity of high-Z inhomogeneities. The observed dose enhancement effect with proton therapy is not correctly modeled by TPS. An extra measure of caution should be taken when evaluating dosimetry with spinal metallic implants.