Browsing by Subject "dosimetry"

Now showing 1 - 7 of 7
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    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 Medicine
    A 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.
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    Functional liver-image guided hepatic therapy (FLIGHT): A technique to maximize hepatic functional reserve
    (Elsevier, 2020-06) Furukawa, Yukie; Long, David E.; Ellsworth, Susannah G.; Radiation Oncology, School of Medicine
    Introduction: Radiation planning approaches for liver radiation often do not consider the regional variation that can exist in liver function. This study dosimetrically compares functional liver image-guided hepatic therapy (FLIGHT) to standard stereotactic body radiation therapy (SBRT) plans. In the FLIGHT plans, functional data from hepatobiliary iminodiacetic acid (HIDA) single photon emission computed tomography (SPECT) scans serve as a road map to guide beam arrangement. While meeting the same target volume coverage, plans are optimized to reduce dose to high-functioning liver. Materials and Methods: The study included 10 patients with hepatocellular carcinoma (HCC) with baseline HIDA SPECT imaging. Standard SBRT plans which did not systematically incorporate these scans had previously been completed on all 10 plans. Retrospectively, FLIGHT plans were created based on the use of contours of relative liver function from the HIDA SPECT as avoidance structures. Resulting dose to each relative functional liver structure was examined and compared qualitatively and using Wilcoxin rank-sum tests. Target coverage, doses to organs at risk (OARs), conformity index (CI), and gradient index (GI) were also evaluated. Results: While maintaining the same target coverage, FLIGHT plans reduced the mean dose to the high functioning liver by a median of 3.0 Gy (range 0.7 to 4.6 Gy), which represented a 31.4% mean reduction compared to standard planning. FLIGHT plans reduced the volume of high functioning liver receiving 15 Gy by a mean of 59.3 cc (range 7 to 170 cc), for a mean reduction of 41.9%. The mean dose to areas of liver function defined by 25% to 100% and 50% to 100% maximum was reduced with FLIGHT from 10.5 Gy to 8.5 Gy and from 10.5 Gy to 7.5 Gy, respectively ( p < 0.005 for both comparisons). The FLIGHT plans’ mean CI and GI did not differ significantly from the standard plans’ ( p = 0.721 and 0.169, respectively). Conclusion: FLIGHT SBRT allows for field design and plan optimization individualized to a patient's baseline regional liver function to maximize hepatic functional reserve. This personalized approach is achieved without compromising target coverage or OAR sparing.
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    Patient specific quality assurance of volumetric modulated arc therapy of synchronous bilateral breast cancer
    (Elsevier, 2024) Djoumessi Zamo, Francis C.; Njeh, Christopher F.; Colliaux, Anthony; Blot-Lafond, Valérie; Moyo, M. Ndontchueng; Radiation Oncology, School of Medicine
    Synchronous bilateral breast cancers (SBBC) present a considerable issue in external beam radiotherapy because of large fields size and large target volumes. Mono-isocentric volumetric modulated arc therapy (VMAT) appears as an appropriate irradiation technique for these types of tumors. The aim of this study was to demonstrate the utility of a 3D DVH pretreatment quality assurance program in VMAT of SBBC cases. Twenty SBBC patients who underwent radiation therapy in our department were retrospectively enrolled in this study. Fifteen patients were treated exclusively to the mammary glands. Five patients benefited from a dose boost on the tumor bed (60Gy). Nine patients were irradiated on the supraclavicular nodes (50Gy). This dose was delivered in 25 fractions and integrated boost was used when appropriate. Depending on the complexity of the treatment plans; 2 or 4 arcs VMAT plans were used in a mono-isocentric technique. The patient specific quality assurance (PSQA) was evaluated using COMPASS measured data, COMPASS reconstructed (CR) and COMPASS computed (CC) dose compared to treatment planning system (TPS) dose. Clinical evaluation was based on DVH metrics for target volumes and organ at risks. The maximum average dose deviation between TPS, CC, and CR was below 3%. The paired t-test between TPS, CC, and CR shows a strong agreement (p < 0.001). The 3DVH dose distribution comparison between TPS and COMPASS were also performed with good gamma score for global analysis. COMPASS was successfully evaluated as a 3DVH pretreatment system for SBBC despite the large fields size and complex target volumes. It allows the verification of the plan in 3D patient anatomy and the evaluation of dose discrepancies.
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    Pediatric Phantom Dosimetry Evaluation of a New Rectangular Collimator
    (American Academy of Pediatric Dentistry, 2023) Martinez, Amanda; Yepes, Juan F.; Jones, James E.; Wong, Phillip; Johnson, K. Brandon; Canady, Sarah; Tang, Qing; Pediatric Dentistry, School of Dentistry
    Purpose: To compare the effective dose (E) of the Tru-Image® rectangular collimator and the universal round collimator of a Planmeca® wall-mounted radiograph unit for two bitewing radiographs (right and left) on a pediatric phantom. Methods: Absorbed doses utilizing the Tru-Image ®rectangular collimator and universal round collimator were acquired using an anthropomorphic 10-year-old child phantom. Each set of 24 dosimeters was exposed to two bitewing exposures with the manufacturer's child settings. Fifty clinical exposures were completed for each set and three sets were exposed for each collimator. The average E per exposure was calculated. Results: The overall E for the Tru-Image ®rectangular collimator and the universal round collimator were 6.3 microsieverts (μSv) and 25.3 μSv, respectively. This difference was statistically significant (P <0.001). The highest equivalent dose for both collimators was delivered to the oral mucosa. When compared to the universal round collimator, the Tru-Image ® rectangular collimator had significant dose reduction at all locations (P <0.05). When normalized and adjusted to the same source-to-end distance, there was an overall 65 percent dose reduction with the rectangular collimator. Conclusion: The average effective dose was significantly reduced with the use of the Tru-Image ®rectangular collimator. Clinical use of this rectangular collimator should be considered in the pediatric population.
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    Pediatric Phantom Dosimetry Evaluation of the Extraoral Bitewing
    (American Academy of Pediatric Dentistry, 2020-01) Wiley, Dillon; Yepes, Juan F.; Sanders, Brian J.; Jones, James E.; Johnson, K. Brandon; Tang, Qing; Pediatric Dentistry, School of Dentistry
    Purpose: This study’s purpose was to evaluate the effective dose (E) and equivalent dose (HT) of exposing a pediatric phantom to the extraoral bitewing programs of the Planmeca ProMax 2D S3 (ProMax) and Instrumentarium Orthopantomograph OP30 (OP30) and compare these results with dosimetry associated with the intraoral bitewing and panoramic radiograph. Methods: Dosimetry was acquired by placing 24 dosimeters in tissues of interest in a 10-year-old phantom. Manufacturer child settings were used for all scans. Repeat exposures of 20 scans were utilized. The average values of E and HT were calculated. Results: The E for the ProMax and OP30 units, respectively, were 16.84 μSv and 5.82 μSv. The highest E for both units was delivered to the thyroid, remainder tissues, and salivary glands. The highest HT for both units was delivered to the oral mucosa, salivary glands, extrathoracic airway, and thyroid. The mean differences between units were statistically significant (P<0.05). Conclusions: The average effective dose of the ProMax was higher than for the OP30. The effective dose of the pediatric extraoral bitewing is three to 11 times higher than that of the intraoral bitewing and comparable to the traditional panoramic radiograph of a pediatric phantom. Pediatric extraoral bitewing radiation protection guidelines are recommended.
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    Pediatric Phantom Dosimetry of Kodak 9000 Cone-beam Computed Tomography
    (American Academy of Pediatric Dentistry, 2017-05) Yepes, Juan F.; Booe, Megan R.; Sanders, Brian J.; Jones, James E.; Ehrlich, Ygal; Ludlow, John B.; Johnson, Brandon; Pediatric Dentistry, School of Dentistry
    Purpose: The purpose of the study was to evaluate the radiation dose of the Kodak 9000 cone-beam computed tomography (CBCT) device for different anatomical areas using a pediatric phantom. Methods: Absorbed doses resulting from maxillary and mandibular region three by five cm CBCT volumes of an anthropomorphic 10-year-old child phantom were acquired using optical stimulated dosimetry. Equivalent doses were calculated for radiosensitive tissues in the head and neck area, and effective dose for maxillary and mandibular examinations were calculated following the 2007 recommendations of the International Commission on Radiological Protection (ICRP). Results: Of the mandibular scans, the salivary glands had the highest equivalent dose (1,598 microsieverts [μSv]), followed by oral mucosa (1,263 μSv), extrathoracic airway (pharynx, larynx, and trachea; 859 μSv), and thyroid gland (578 μSv). For the maxilla, the salivary glands had the highest equivalent dose (1,847 μSv), followed closely by oral mucosa (1,673 μSv), followed by the extrathoracic airway (pharynx, larynx, and trachea; 1,011 μSv) and lens of the eye (202 μSv). Conclusion: Compared to previous research of the Kodak 9000, completed with the adult phantom, a child receives one to three times more radiation for mandibular scans and two to 10 times more radiation for maxillary scans.
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    Rapid RBE-Weighted Proton Radiation Dosimetry Risk Assessment
    (Sage, 2016-10) Qutub, Mohammad A. Z.; Klein, Susan B.; Buchsbaum, Jeffrey C.; Department of Radiation Oncology, IU School of Medicine
    Proton therapy dose is affected by relative biological effectiveness differently than X-ray therapies. The current clinically accepted weighting factor is 1.1 at all positions along the depth–dose profile. However, the relative biological effectiveness correlates with the linear energy transfer, cell or tissue type, and the dose per fraction causing variation of relative biological effectiveness along the depth–dose profile. In this article, we present a simple relative biological effectiveness-weighted treatment planning risk assessment algorithm in 2-dimensions and compare the results with those derived using the standard relative biological effectiveness of 1.1. The isodose distribution profiles for beams were accomplished using matrices that represent coplanar intersecting beams. These matrices were combined and contoured using MATLAB to achieve the distribution of dose. There are some important differences in dose distribution between the dose profiles resulting from the use of relative biological effectiveness = 1.1 and the empirically derived depth-dependent values of relative biological effectiveness. Significant hot spots of up to twice the intended dose are indicated in some beam configurations. This simple and rapid risk analysis could quickly evaluate the safety of various dose delivery schema.