Aim of this work is evaluate the performance of LiF detectors, TLD-100H, used for both environmental and radiodiagnostic dosimetry. General-Order kinetics (GOK) expressions were applied to experimental glow curves of TLDs 100H (LiF. Mg, P, Cu), that were irradiated with an X-ray tube at 140 kVp and reading with a Riso TL/OSL-DA-10 system. New tests were introduced such as the Recuperation test, for evaluate the residual luminescent after each measurement cycle, the Recycling test, aimed to evaluate any systematic errors in the calibration curve and, at last, the Recovery test, with the purpose of evaluate the accuracy of the measured dose from each single dosimeter. The results obtained show an accuracy on the various measured doses ranging from 1.20% to 2.56%.
A: The patient dose in radiodiagnostic is currently monitored through an ionizing radiation exposure index named Volume Computed Tomography Dose Index (CTDI vol ) and the Dose-Length Product (DLP), displayed by CT scanner and measurable through a 100 mm long pencil ionization chamber, inserted in a homogeneous cylindrical PMMA phantom. The phantom is 14 cm long and has a diameter of 16 (32) cm that represents the adult head (body). One of the main flaws of such a method is that it does not return any information on the dose distribution to organs, and the average absorbed dose value, due to the material and dimensions of both the phantom and the ionization chamber, might be either underestimated or overestimated depending upon the patient size. With the aim to obtain complementary information, this work presents a method to estimate organ dose in the thoracic area of an anthropomorphic woman phantom in CT, by employing Gafchromic TM XR-QA2 and computational 3-D reconstruction methods. Lungs, heart, and spinal cord have been chosen as a dosimetry case study. XR-QA2 films have been placed between the phantom slabs in the thoracic area and scanned with a multi-slice CT scanner. 2-D and 3-D absorbed dose distributions for each organ have been analyzed, by means of a custom code in Matlab ® . Critical aspects in the dose distributions have been found for the spinal-cord case (serial organ) where the dose distribution is non normal and the maximum dose value is ∼ 30 mGy while a maximum dose value between 26 and 28 mGy has been measured elsewhere.
K: Dosimetry concepts and apparatus; Computerized Tomography (CT) and Computed Radiography (CR); Medical-image reconstruction methods and algorithms, computer-aided diagnosis 1Corresponding author.
Multiple brain metastases single-isocenter stereotactic radiosurgery (SRS) treatment is increasingly employed in radiotherapy department. Before its use in clinical routine, it is recommended to perform end-to-end tests. In this work, we report the results of five HyperArcTM treatment plans obtained by both ionization chamber (IC) and polymer gel. The end-to-end tests were performed using a water equivalent Mobius Verification PhantomTM (MVP) and a 3D-printed anthropomorphic head phantom PseudoPatient® (PP) (RTsafe P.C., Athens, Greece); 2D and 3D dose distributions were evaluated on the PP phantom using polymer gel (RTsafe). Gels were read by 1.5T magnetic resonance imaging (MRI). Comparison between calculated and measured distributions was performed using gamma index passing rate evaluation by different criteria (5% 2 mm, 3% 2 mm, 5% 1 mm). Mean point dose differences of 1.01% [min −0.77%–max 2.89%] and 0.23% [min 0.01%–max 2.81%] were found in MVP and PP phantoms, respectively. For each target volume, the obtained results in terms of gamma index passing rate show an agreement > 95% with 5% 2 mm and 3% 2 mm criteria for both 2D and 3D distributions. The obtained results confirmed that the use of a single isocenter for multiple lesions reduces the treatment time without compromising accuracy, even in the case of target volumes that are quite distant from the isocenter.
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