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in-vivo dosimetry

Inge van der Kroon, Wietske Woliner-van der Weg, Maarten Brom, Lieke Joosten, Cathelijne Frielink, Mark W Konijnenberg, Eric P Visser, Martin Gotthardt
Radiolabeled exendin is used for non-invasive quantification of beta cells in the islets of Langerhans in vivo. High accumulation of radiolabeled exendin in the islets raised concerns about possible radiation-induced damage to these islets in man. In this work, islet absorbed doses resulting from exendin-imaging were calculated by combining whole organ dosimetry with small scale dosimetry for the islets. Our model contains the tissues with high accumulation of radiolabeled exendin: kidneys, pancreas and islets...
January 9, 2017: Scientific Reports
Jacob L Houghton, Rosemery Membreno, Dalya Abdel-Atti, Kristen M Cunanan, Sean Carlin, Wolfgang W Scholz, Pat B Zanzonico, Jason S Lewis, Brian M Zeglis
The pretargeting system based on the inverse electron demand Diels-Alder reaction (IEDDA) between trans-cyclooctene (TCO) and tetrazine (Tz) combines the favorable pharmacokinetic properties of radiolabeled small molecules with the affinity and specificity of antibodies. This strategy has proven to be an efficient method for the molecularly targeted delivery of pharmaceuticals, including isotopes for radiological imaging. Despite encouraging results from in vivo PET imaging studies, this promising system has yet to be thoroughly evaluated for pretargeted radioimmunotherapy (PRIT)...
January 2017: Molecular Cancer Therapeutics
T Sullivan, A Diak, M Surucu, J Yacoub, M Harkenrider, S Shea
PURPOSE: The use of MR to plan and evaluate brachytherapy treatment for cervical cancer is increasing given the availability of MR conditional or safe applicators and MRI's proven superiority to CT for characterizing soft tissue lesions. The titanium applicators, however, cause geometric distortions or imaging artifacts, which reduce the utility of MRI for dosimetry. We sought to quantify the observed volume of the same applicator on a previously optimized T2 sequence in comparison to the conventional T2 sequence and CT obtained for brachytherapy planning...
June 2016: Medical Physics
E P Pappas, N Papanikolaou, G Kalaitzakis, T Boursianis, D Makris, V Lahanas, I Genitsarios, S Stathakis, L Watts, T Maris, E Pappas
PURPOSE: To validate dose calculation and delivery accuracy of a recently introduced mono-isocentric technique for the treatment of multiple brain metastases in a realistic clinical case. METHODS: Anonymized CT scans of a patient were used to model a hollow phantom that duplicates anatomy of the skull. A 3D printer was used to construct the phantom of a radiologically bone-equivalent material. The hollow phantom was subsequently filled with a polymer gel 3D dosimeter which also acted as a water-equivalent material...
June 2016: Medical Physics
J Rottmann
There has been increased deployment of gantry-mounted linacs with onboard kilovoltage x-ray imagers. Despite this trend, most clinics still employ beam's-eye-view (BEV) imaging using flat panel electronic portal imaging devices (EPIDs) as a highly useful means of verifying geometric localization pre- and post-delivery. In recent years, there has been increased interest in the use of EPIDs for a variety of clinical and investigational applications ranging from megavoltage cone-beam CT, in vivo dosimetry, patient-specific QA to real-time target localization for dynamic MLC-based tumor tracking...
June 2016: Medical Physics
A Riegel, M Tariq, C Gomez, E Klein
PURPOSE: Optically-stimulated luminescent dosimeters (OSLDs) are increasingly utilized for in vivo dosimetry of complex radiation delivery techniques such as intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT). Evaluation of clinical uncertainties such as placement error has not been performed. This work retrospectively investigates the magnitude of placement error using conebeam computed tomography (CBCT) and its effect on measured/planned dose agreement...
June 2016: Medical Physics
H Kaur, S Kumar, B Sarkar, T Ganesh, U Giri, K Jassal, S Rathinamuthu, G Gulia, V Gopal, B Mohanti, A Munshi
PURPOSE: This study was performed to analyze the agreement between optically stimulated luminescence (OSL) nanoDots measured doses and 0.6 cc Farmer type ionization chamber measured doses during total body irradiation (TBI). METHODS: In-vivo dose measurements using OSL nanoDots and Farmer chamber were done in a total of twelve patients who received TBI at our center by bilateral parallel-opposed beams technique. In this technique, the patient is kept inside the TBI box which is filled with rice bags and irradiated using two bilateral parallel opposed beams of 40×40 cm(2) size with 45° collimator rotation at an SSD of 333...
June 2016: Medical Physics
F Therriault-Proulx, Z Wen, G Ibbott, S Beddar
PURPOSE: To study the effect of a strong magnetic field on the scintillation and the stem effect from a plastic scintillation detector (PSD) and evaluate its accuracy to measure dose. METHODS: A plastic scintillation detector and a bare plastic fiber were placed inside a magnet of adjustable field strength (B=0-1.5T) and irradiated by a 6-MV photon beam (Elekta Versa HD LINAC). The PSD was built in-house using a scintillating fiber (BCF-60, 3-mm long × 1-mm diameter) coupled to an optical fiber similar to the bare fiber (PMMA, 12-m long, 1-mm diameter)...
June 2016: Medical Physics
B Hernandez Reyes, E Rodriguez Perez, M Sosa Aquino
PURPOSE: To implement a back-projection algorithm for 2D dose reconstructions for in vivo dosimetry in radiation therapy using an Electronic Portal Imaging Device (EPID) based on amorphous silicon. METHODS: An EPID system was used to calculate dose-response function, pixel sensitivity map, exponential scatter kernels and beam hardenig correction for the back-projection algorithm. All measurements were done with a 6 MV beam. A 2D dose reconstruction for an irradiated water phantom (30×30×30 cm(3) ) was done to verify the algorithm implementation...
June 2016: Medical Physics
C Venencia, A Germanier, E Garrigo, P Castro Pena, J Torres, S Zunino
PURPOSE: The elective irradiation of pelvis lymph node for prostate cancer is still controversial. Including pelvic lymph node as part of the planning target volume could increase the testicular scatter dose, which could have a clinical impact. The objective of this work was to measure testicular scatter dose for prostate SBRT treatment with and without pelvic lymph nodes using TLD dosimetry. METHODS: A 6MV beam (1000UM/min) produce by a Novalis TX (BrainLAB-VARIAN) equipped HDMLC was used...
June 2016: Medical Physics
J L Oacutepez-Tarjuelo
PURPOSE: To initiate a discussion on the current and evolving role of Medical Physicists based on author's professional and research experience in patient safety and quality control. METHODS: Several professionals of the departments of Medical Physics and Radiation Oncology, chiefly devoted to clinical tasks, began a research program on patient safety and quality control in a framework provided by the implementation of intraoperative radiotherapy (IORT). We performed studies on virtual simulation for IORT, in vivo dosimetry, failure mode and effect analysis (FMEA), statistical process control (SPC), and receiver operating characteristics of dosimetric equipment...
June 2016: Medical Physics
P Greer
There has been increased deployment of gantry-mounted linacs with onboard kilovoltage x-ray imagers. Despite this trend, most clinics still employ beam's-eye-view (BEV) imaging using flat panel electronic portal imaging devices (EPIDs) as a highly useful means of verifying geometric localization pre- and post-delivery. In recent years, there has been increased interest in the use of EPIDs for a variety of clinical and investigational applications ranging from megavoltage cone-beam CT, in vivo dosimetry, patient-specific QA to real-time target localization for dynamic MLC-based tumor tracking...
June 2016: Medical Physics
Gopiraj Annamalai, Yoichi Watanabe
PURPOSE: To develop a simple method for estimating the mid-plane dose (MPD) of a patient using Electronic Portal imaging Device (EPID). METHODS: A Varian TrueBeam with aSi100 EPID was used in this study. The EPID images were acquired for a 30 cm × 30 cm homogeneous slab phantom and a 30 cm diameter 20 cm thick cylindrical phantom in the continuous dosimetry mode. The acquired EPID images in XIM format were imported into in-house MATLAB program for the data analysis...
June 2016: Medical Physics
A Rea, A Kuruvilla, G Gill, A Riegel, E Klein
PURPOSE: The purpose of this study was to observe the effect of an electromagnetic array used for patient localization and tumor tracking on optically-stimulated luminescent in-vivo dosimetry. METHODS: A linear accelerator equipped with four photon energies was used to irradiate optically stimulated luminescent dosimeters (OSLDs) at the respective dmax depths and in the buildup region, with and without the presence of an electromagnetic array used for tumor tracking and patient localization...
June 2016: Medical Physics
M Kydonieos, A Folgueras, L Florescu, T Cybulski, N Marinos, G Thompson, A Sayeed, R Rozendaal, I Olaciregui-Ruiz, A Subiel, I Silvestre Patallo
PURPOSE: Elekta recently developed a solution for in-vivo EPID dosimetry (iViewDose, Elekta AB, Stockholm, Sweden) in conjunction with the Netherlands Cancer Institute (NKI). This uses a simplified commissioning approach via Template Commissioning Models (TCMs), consisting of a subset of linac-independent pre-defined parameters. This work compares the performance of iViewDose using a TCM commissioning approach with that corresponding to full commissioning. Additionally, the dose reconstruction based on the simplified commissioning approach is validated via independent dose measurements...
June 2016: Medical Physics
K Legge, D Cutajar, A Wilfert, J Martin, A Rozenfeld, D J O'Connor, P Greer
PURPOSE: To provide in vivo measurements of dose to the anterior rectal wall during prostate SBRT boost treatments using MOSFET detectors. METHODS: Dual MOSkin detectors were attached to a Rectafix rectal sparing device and inserted into patients during SBRT boost treatments. Patients received two boost fractions, each of 9.5-10 Gy and delivered using 2 VMAT arcs. Measurements were acquired for 12 patients. MOSFET voltages were read out at 1 Hz during delivery and converted to dose...
June 2016: Medical Physics
A Pasciak, L Nodit, A Bourgeois, B Paxton, A Arepally, Y Bradley
PURPOSE: In Yttrium-90 (90Y) radioembolization, non-target embolization (NTE) to the stomach or small bowel can result in ulceration, a rare but difficult to manage clinical complication. However, dosimetric thresholds for toxicity to these tissues from radioembolization have never been evaluated in a controlled setting. We performed an analysis of the effect of 90Y radioembolization in a porcine model at different absorbed-dose endpoints. METHODS: Under approval of the University of Tennessee IACUC, 6 female pigs were included in this study...
June 2016: Medical Physics
J Lah, J Son, G Kim, D Shin
PURPOSE: To evaluate the possibility of a fiber-optic Cerenkov radiation sensor (FCRS) for in vivo dose verification in proton therapy. METHODS: The Cerenkov radiation due to the proton beam was measured using a homemade phantom, consisting of a plastic optical fiber (POF, PGSCD1001-13-E, Toray, Tokyo, Japan) connected to each channel of a multianode photomultiplier tube (MAPMT:H7546, Hamamatsu Photonics, Shizuoka, Japan). Data were acquired using a multi-anode photomultiplier tube with the NI-DAQ system (National Instruments Texas, USA)...
June 2016: Medical Physics
S Souri, X Qian, G Gill, A Jamshidi, Y Cao, Y Chen
PURPOSE: To investigate energy dependent effects of different dosimetry systems which can be used as in vivo dosimetry monitoring for intraoperative radiotherapy in therapeutic soft x-ray energy range. METHODS: Three dosimetry systems were evaluated in therapeutic soft x-ray energy range: optically stimulated luminescent dosimeter (OSLD) nanoDots, radiochromic EBT2 and EBT3 films. The x-ray photons were produced by a Zeiss Intrabeam 50 kV x-ray radiotherapy system...
June 2016: Medical Physics
M Held, J Cheung, F Husson, O Morin
PURPOSE: To commission and evaluate an in vivo EPID-based transit dosimetry software (EPIgray, DOSIsoft, Cachan, France) using simple fields and TG119-based IMRT treatment plans. METHODS: EPIgray was commissioned on a Truebeam based on finite tissue-maximum ratio (fTMR) measurements with solid water blocks of thicknesses between 0 and 37 cm. Field sizes varied from 2×2 to 20×20 cm(2) . Subsequently, treatment plans of single and opposed beams with field sizes between 4×4 and 15×15 cm(2) as well as IMRT plans were measured to evaluate the dose reconstruction accuracy...
June 2016: Medical Physics
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