Irradiation Device Research Articles

Fabrication of PEG Hydrogel and PDMS Microstructures by a Simple UV Curing Process for Nanobio-Chip Applications

Polyethylene glycol (PEG) hydrogel microstructures with various shapes and sizes on a glass chip were prepared by a simple and rapid ultraviolet (UV) irradiation method using a metal mask. Photocurable PEG solution prepared by mixing 95 wt.% polyethylene glycol diacrylate and 5 wt.% 2-hydroxy-2-methylpropiophenone as a photo-initiator was injected to the gap between bottom and upper glasses in a simply assembled glass chip. After a metal mask with line-and-space or complex patterns was placed on the glass chip, UV light from a spot UV irradiation device was exposed to the glass chip through the metal mask for 7 seconds at UV intensity of 26 mW/cm2. Then the PEG hydrogel micropatterns on the glass chip were obtained after removing unreacted PEG solution by air blowing. To prepare more rigid microstructure, the prepared PEG micropatterned chip was exposed under UV light for 20 seconds. Then the PEG hydrogel micropattern chip was fabricated by a simple and rapid procedure. Micropattern transferring was performed from the PEG hydrogel chip to polydimethyl siloxane (PDMS) replica by a solution casting. The prepared micropatterned PDMS replicas showed similar shape and size of microstructures compared to that of the corresponded PEG hydrogel chip. Thus the PEG hydrogel microstructures on a glass chip could be used as a mold to fabricate micropattern PDMS chips for nanobio-chip applications. Furthermore, the present method provides large scale chip fabrication, more than 4 cm-length and 4 cm-width in a single step, not only PEG hydrogel chips but also PDMS chips.

WE-D-BRE-01: A Sr-90 Irradiation Device for the Study of Cutaneous Radiation Injury

Purpose: To determine dosimetric character for a custom-built Sr-90 beta irradiator designed for the study of Cutaneous Radiation Injury (CRI) in a porcine animal model. In the event of a radiological accident or terrorist event, Sr-90, a fission by-product, will likely be produced. CRI is a main concern due to the low energy and superficial penetration in tissue of beta particles from Sr-90. Seven 100 mCi plaque Sr-90 radiation sources within a custom-built irradiation device create a 40 mm diameter region of radiation-induced skin injury as part of a larger project to study the efficacy of a topical keratin-based product in CRI healing. Methods: A custom-built mobile irradiation device was designed and implemented for in vivo irradiations. Gafchromic™ EBT3 radiochromic film and a PTW Markus chamber type 23343 were utilized for dosimetric characterization of the beta fluence at the surface produced by this device. Films were used to assess 2-dimensional dose distribution and percent depth dose characteristics of the radiation field. Ion chamber measurements provided dose rate data within the field. Results: The radiation field produced by the irradiation device is homogeneous with high uniformity (∼5%) and symmetry (∼3%) with a steep dose fall-off with depth from the surface. Dose rates were determined to be 3.8 Gy/min and 3.3 Gy/min for film and ion chamber measurements, respectively. A dose rate of 3.4 Gy/min was used to calculate irradiation times for in vivo irradiations. Conclusion: The custom-built irradiation device enables the use of seven Sr-90 beta sources in an array to deliver a 40 mm diameter area of homogeneous skin dose with a dose rate that is useful for research purposes and clinically relevant for the induction of CRI. Doses of 36 and 42 Gy successfully produce Grade III CRI and are used in the study of the efficacy of KeraStat™. This project has been funded in whole or in part with Federal funds from the Biomedical Advanced Research and Development Authority, Office of the Assistant Secretary for Preparedness and Response, Office of the Secretary, Department of Health and Human Services, under Contract No. HHSO100201200007C.

Using TRIGA Mark II research reactor for irradiation with thermal neutrons

Recently a series of test irradiations was performed at the JSI TRIGA Mark II reactor for the Fission Track-Thermoionization Mass Spectrometry (FT-TIMS) method, which requires a well thermalized neutron spectrum for sample irradiation. For this purpose the Monte Carlo N-Particle Transport Code (MCNP5) was used to computationally support the design of an irradiation device inside the TRIGA model and to support the actual measurements by calculating the neutron fluxes inside the major ex-core irradiation facilities. The irradiation device, filled with heavy water, was designed and optimized inside the Thermal Column and the additional moderation was placed inside the Elevated Piercing Port. The use of the device improves the ratio of thermal neutron flux to the sum of epithermal and fast neutron flux inside the Thermal Column Port by 390% and achieves the desired thermal neutron fluence of 1015neutrons/cm2 in irradiation time of 20h.

Observation of Ferromagnetic Resonance in Magnetic Exchange Force Microscopy (MExFM)

The atomic spin interaction is very important for understanding the superficially magnetic feature of nanostructure at atomic level. Magnetic exchange force microscopy (MExFM) is an innovative means of measuring surface spin force. But it is difficult to separate the surface topography and spin information. We develop the magnetic exchange force microscopy using ferromagnetic resonance (FMR-MExFM). The theoretical and experimental results demonstrate that this method can separate the two kinds of information effectively. Here, in order to obtain the high sensitivity in detecting the ferromagnetic resonance, we fabricate the microwave irradiation device to optimize the position between the device and the cantilever. We have succeeded in observing the ferromagnetic resonance effect and determining its resonant frequency using the homemade microwave irradiation device and the network analyzer. This research is very important for developing FMR-MExFM and novel magnetic sensor, detecting the magnetic information, etc.

Corneal stroma demarcation line after standard and high-intensity collagen crosslinking determined with anterior segment optical coherence tomography

To use anterior segment optical coherence tomography (AS-OCT) to compare corneal stroma demarcation line depth after corneal collagen crosslinking (CXL) with 2 treatment protocols. Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. Prospective comparative interventional case series. Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm(2) according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm(2) of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the corneal stroma demarcation line using AS-OCT. Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean corneal stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the corneal stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 (P=.0058, t test for unpaired data). The corneal stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation.

Partial body irradiation of small laboratory animals with an industrial X-ray tube

AimsDedicated precise small laboratory animal irradiation sources are needed for basic cancer research and to meet this need expensive high precision radiation devices have been developed. To avoid such expenses a cost efficient way is presented to construct a device for partial body irradiation of small laboratory animals by adding specific components to an industrial X-ray tube. Methods and materialsA custom made radiation field tube was added to an industrial 200kV X-ray tube. A light field display as well as a monitor ionization chamber were implemented. The field size can rapidly be changed by individual inserts of MCP96 that are used for secondary collimation of the beam. Depth dose curves and cross sectional profiles were determined with the use of a custom made water phantom. More components like positioning lasers, a custom made treatment couch, and a commercial isoflurane anesthesia unit were added to complete the system. ResultsWith the accessories described secondary small field sizes down to 10 by 10 mm2 (secondary collimator size) could be achieved. The dosimetry of the beam was constructed like those for conventional stereotactical clinical linear accelerators. The water phantom created showed an accuracy of 1mm and was well suited for all measurements. With the anesthesia unit attached to the custom made treatment couch the system is ideal for the radiation treatment of small laboratory animals like mice. ConclusionIt was feasible to shrink the field size of an industrial X-ray tube from whole animal irradiation to precise partial body irradiation of small laboratory animals. Even smaller secondary collimator sizes than 10 by 10 mm2 are feasible with adequate secondary collimator inserts. Our custom made water phantom was well suited for the basic dosimetry of the X-ray tube.

Clinical Experience with a Miniature Accelerated Partial Breast Irradiation Device: A 5-Year Single Institution Comprehensive Study

Clinical Experience with a Miniature Accelerated Partial Breast Irradiation Device: A 5-Year Single Institution Comprehensive Study

SP-0360: Image guidance and treatment planning for a small animal precision irradiation device

SP-0360: Image guidance and treatment planning for a small animal precision irradiation device

IRRADIATION DEVICE FOR IRRADIATION TESTING OF COATED PARTICLE FUEL AT HANARO

The Korean Nuclear-Hydrogen Technology Development (NHTD) Plan will be performing irradiation testing of coated particle fuel at HANARO to support the development of VHTR in Korea. This testing will be carried out to demonstrate and qualify TRISO-coated particle fuel for use in VHTR. The testing will be irradiated in an inert gas atmosphere without on-line temperature monitoring and control combined with on-line fission product monitoring of the sweep gas. The irradiation device contains two test rods, one has nine fuel compacts and the other five compacts and eight graphite specimens. Each compact contains about 260 TRISO-coated particles. The irradiation device is being loaded and irradiated into the OR5 hole of the in HANARO core from August 2013. The device will be operated for about 150 effective full-power days at a peak temperature of about 1030°C in BOC (Beginning of Cycle) during irradiation testing. After a peak burn-up of about 4 atomic percentage and a peak fast neutron fluence of about 1.7×10 21 n/cm 2 , PIE (Post-Irradiation Examination) of the irradiated coated particle fuel will be performed at IMEF (Irradiated Material Examination Facility). This paper reviews the design of test rod and irradiation device for coated particle fuel, and discusses the technical results for irradiation testing at HANARO.

The Dosimetric Effect of Tumor Size and Position in Prone Radiation Therapy of Breast Using a Novel Stereotactic Breast Irradiation Device

ionization chamber array system (2D array) was used for dose measurement. Measurement sampling time of the 2D array was set to 50 ms, and a sensitivity correction that depended on gantry angle was applied. The dose difference on the central coronal plane between SSVMAT delivery and the original VMAT delivery was analyzed. The dose at the isocenter was also compared using the center chamber of the 2D array. Pass rate was calculated from the dose difference with a criterion of 1% for a region that delivered a dose higher than 10% of the maximum dose. Results: Mean differences in doses at the isocenter between VMAT and SSVMAT were not significant (0.5 0.5% for 10 s interval, 0.2 0.3% for 15 s interval, 0.2 0.2% for 20 s interval, 0.0 0.1% for 30 s interval, and 0.0 0.1% for 40 s interval, p > 0.05). Pass rates based on dose difference were 85 17% for 10 s interval, 99.9 0.2% for 15 s interval, 100 0% for 20 s interval, 100 0% for 30 s interval, and 100 0% for 40 s interval. SSVMAT with the breath-hold interval of 10 s had a significantly reduced pass rate (p Z 0.017). Conclusions: In the present study, a practical irradiation method that can be used to divide VMAT delivery into feasible breath-hold intervals was developed. Analysis of dose verification revealed that SSVMAT deliveries with intervals of 15 s or longer provided accurate doses. Author Disclosure: K. Noto: None. S. Ueda: None. T. Takanaka: None. A. Takemura: None.

Proteomic analysis on the alteration of protein expression in the early-stage placental villous tissue of electromagnetic fields associated with cell phone exposure.

To explore the possible adverse effects and search for cell phone electromagnetic field (EMF)-responsive proteins in human early reproduction, a proteomics approach was employed to investigate the changes in protein expression profile induced by cell phone EMF in human chorionic tissues of early pregnancy in vivo. Volunteer women about 50 days pregnant were exposed to EMF at the average absorption rate of 1.6 to 8.8 W/kg for 1 hour with the irradiation device placed 10 cm away from the umbilicus at the midline of the abdomen. The changes in protein profile were examined using 2-dimensional electrophoresis (2-DE). Up to 15 spots have yielded significant change at least 2- to 2.5-folds up or down compared to sham-exposed group. Twelve proteins were identified- procollagen-proline, eukaryotic translation elongation factor 1 delta, chain D crystal structure of human vitamin D-binding protein, thioredoxin-like 3, capping protein, isocitrate dehydrogenase 3 alpha, calumenin, Catechol-O-methyltransferase protein, proteinase inhibitor 6 (PI-6; SerpinB6) protein, 3,2-trans-enoyl-CoA isomerase protein, chain B human erythrocyte 2,3-bisphosphoglycerate mutase, and nucleoprotein. Cell phone EMF might alter the protein profile of chorionic tissue of early pregnancy, during the most sensitive stage of the embryos. The exposure to EMF may cause adverse effects on cell proliferation and development of nervous system in early embryos. Furthermore, 2-DE coupled with mass spectrometry is a promising approach to elucidate the effects and search for new biomarkers for environmental toxic effects.

Dosimetric comparison between intra-cavitary breast brachytherapy techniques for accelerated partial breast irradiation and a novel stereotactic radiotherapy device for breast cancer: GammaPod™

The GammaPod™ device, manufactured by Xcision Medical Systems, is a novel stereotactic breast irradiation device. It consists of a hemispherical source carrier containing 36 Cobalt-60 sources, a tungsten collimator with two built-in collimation sizes, a dynamically controlled patient support table and a breast immobilization cup also functioning as the stereotactic frame for the patient. The dosimetric output of the GammaPod™ was modelled using a Monte Carlo based treatment planning system. For the comparison, three-dimensional (3D) models of commonly used intra-cavitary breast brachytherapy techniques utilizing single lumen and multi-lumen balloon as well as peripheral catheter multi-lumen implant devices were created and corresponding 3D dose calculations were performed using the American Association of Physicists in Medicine Task Group-43 formalism. Dose distributions for clinically relevant target volumes were optimized using dosimetric goals set forth in the National Surgical Adjuvant Breast and Bowel Project Protocol B-39. For clinical scenarios assuming similar target sizes and proximity to critical organs, dose coverage, dose fall-off profiles beyond the target and skin doses at given distances beyond the target were calculated for GammaPod™ and compared with the doses achievable by the brachytherapy techniques. The dosimetric goals within the protocol guidelines were fulfilled for all target sizes and irradiation techniques. For central targets, at small distances from the target edge (up to approximately 1 cm) the brachytherapy techniques generally have a steeper dose fall-off gradient compared to GammaPod™ and at longer distances (more than about 1 cm) the relation is generally observed to be opposite. For targets close to the skin, the relative skin doses were considerably lower for GammaPod™ than for any of the brachytherapy techniques. In conclusion, GammaPod™ allows adequate and more uniform dose coverage to centrally and peripherally located targets with an acceptable dose fall-off and lower relative skin dose than the brachytherapy techniques considered in this study.

SU‐E‐J‐12: Evaluation of Setup Uncertainties for Electron Boost Field Treated Using Compression Device for Breast Cancer Irradiation

Purpose: To investigate uncertainties of patient setup for electron boost field using an in‐house breast compression device for breast cancer irradiation. Method: Ten early stage breast cancer patients with deep seated tumor beds treated with post‐lumpectomy radiation were randomly selected. The patients underwent resimulation and treatment with the compression device to decrease the depth of tumor bed. A cone beam computed tomography (CBCT) scan was performed for each patient before treatment and fused with the simulation CT. Four surgical clips located in superior, inferior, left and right of tumor bed were identified in both CT and CBCT data sets for each patient. Set‐up uncertainties were estimated based on differences in the positions of the clips between scans relative to the marked isocenter. Results: For each patient, all clips shifted consistently in the same direction superior‐inferior (SI) and left‐right (LR) direction, but not in the anterior‐posterior (AP) direction because of the perturbation of the compression device. 50% of clips (20 out of 40 clips) shifted anteriorly, 60% shifted inferiorly, and 70% shifted left. Clip shifts in AP direction were smaller than in SI and LR direction. The 55% of clips shifted >1 cm, 18% of clips shifted > 1.5 cm, and only one clip shifted > 2cm which was out of the intended isodose coverage. The average shift of 4 clips for each patient in LR direction was correlated with the breast volume (R2=0.406), but the average shifts of 4 clips in AP and SI direction were not correlated breast volume (R2>0.02). Conclusion: For most patients whose breast boosts were treated with a compression device, a 2cm margin was sufficient to ensure target coverage based on set‐up uncertainties observed in this study. A larger margin might be necessary for electron boost fields for patients with large (volume >2000cc) and/or pendulous breasts.

Dosimetric and geometric evaluation of a novel stereotactic radiotherapy device for breast cancer: The GammaPod™

A dedicated stereotactic gamma irradiation device, the GammaPod™ from Xcision Medical Systems, was developed specifically to treat small breast cancers. This study presents the first evaluation of dosimetric and geometric characteristics from the initial prototype installed at University of Maryland Radiation Oncology Department. The GammaPod™ stereotactic radiotherapy device is an assembly of a hemi-spherical source carrier containing 36 (60)Co sources, a tungsten collimator, a dynamically controlled patient support table, and the breast immobilization system which also functions as a stereotactic frame. The source carrier contains the sources in six columns spaced longitudinally at 60° intervals and it rotates together with the variable-size collimator to form 36 noncoplanar, concentric arcs focused at the isocenter. The patient support table enables motion in three dimensions to position the patient tumor at the focal point of the irradiation. The table moves continuously in three cardinal dimensions during treatment to provide dynamic shaping of the dose distribution. The breast is immobilized using a breast cup applying a small negative pressure, where the immobilization cup is embedded with fiducials also functioning as the stereotactic frame for the breast. Geometric and dosimetric evaluations of the system as well as a protocol for absorbed dose calibration are provided. Dosimetric verifications of dynamically delivered patient plans are performed for seven patients using radiochromic films in hypothetical preop, postop, and target-in-target treatment scenarios. Loaded with 36 (60)Co sources with cumulative activity of 4320 Ci, the prototype GammaPod™ unit delivers 5.31 Gy/min at the isocenter using the largest 2.5 cm diameter collimator. Due to the noncoplanar beam arrangement and dynamic dose shaping features, the GammaPod™ device is found to deliver uniform doses to targets with good conformity. The spatial accuracy of the device to locate the radiation isocenter is determined to be less than 1 mm. Single shot profiles with 2.5 cm collimator are measured with radiochromic film and found to be in good agreement with respect to the Monte Carlo based calculations (congruence of FWHM less than 1 mm). Dosimetric verifications corresponding to all hypothetical treatment plans corresponding to three target scenarios for each of the seven patients demonstrated good agreement with gamma index pass rates of better than 97% (99.0% ± 0.7%). Dosimetric evaluation of the first GammaPod™ stereotactic breast radiotherapy unit was performed and the dosimetric and spatial accuracy of this novel technology is found to be feasible with respect to clinical radiotherapy standards. The observed level of agreement between the treatment planning system calculations and dosimetric measurements has confirmed that the system can deliver highly complex treatment plans with remarkable geometric and dosimetric accuracy.

Development of steady/transient dual plasma irradiation device using a plasma gun

Abstract Synergistic effects of steady state plasma irradiation and transient heat/particle loads to plasma facing materials are an important plasma surface interaction issue in future fusion devices. To investigate the effects systematically, a new plasma gun device was developed and was combined to the linear plasma device NAGDIS-I. Fundamental characteristics of the plasma gun device are revealed in this paper. The amount of tungsten released from the electrode was measured with a material probe method. Also, the emissions from the impurities were investigated spectroscopically. To measure the plasma density, an interferometer measurement was developed; the ion temperature was measured spectroscopically. Moreover, a preliminary irradiation test of the plasma pulse to a tungsten sample was done, and the surface morphology change was shown with the analysis by a scanning electron microscope.

Disinfection of Wastewater by Infiltration-Percolation Coupled to UV Irradiation in an Arid Tunisian Area

This paper aimed to the study of microbiological quality of wastewater effluents issued from a sand filter system used as a secondary treatment; this sand filter was coupled to UV irradiation system as a tertiary treatment to assume their possible application as alternatives to chemical disinfection of municipal wastewater before agronomic utilization. For that reason, an infiltration basin of 100 m² of area equipped with two wells of sampling, in the center and in the periphery, has been constructed on the irrigated perimeter of Dissa in Gabes (south east of Tunisia). A comparative study was undertaken concerning the quality of effluents obtained from the sand filter as secondary effluent and from the UV irradiation disinfection system as a tertiary municipal wastewater treatment. Both the combined systems gave effluent of excellent microbiological quality (almost total absence of E. coli, faecal coliforms and P. aeruginosa). However, if the microbiological quality of effluent remained constant in the case of a sand filter system which depends only on the quality of the influent, while with the UV-disinfection process, microbiological quality of tertiary effluent was shown to depend on the quality of secondary effluent. The monitoring of the UV irradiation device using a UV dose of around 96 mW.s.cm-2 and corresponding to an exposure time of 16 sec, for the secondary effluent at the outlet of Sand Filter, showed that the average bacterial inactivation rate was around 3 U-Log for E. coli, faecal coliforms and P. aeruginosa, respectively. Therefore, the average concentration remaining in the effluent at the output of the UV reactor, was less than a 100 cfu/ 100 ml for E. coli and faecal coliforms, and less than a 100 bacteria/ 100 ml for P. aeruginosa. These values coincided with the range recommended by several standardized international guidelines.

Characteristics of the compact plasma device AIT‐PID with multicusp magnetic confinement

AbstractA unique plasma‐generation device called the “Aichi Institute of Technology‐Plasma Irradiation Device” has been developed for plasma–wall interaction (PWI) studies toward realization of a fusion reactor. It has power‐saving characteristics as well as compactness due to the employment of a multicusp magnetic field configuration instead of a strong axial magnetic field. Helium as well as argon plasmas are generated, showing an outstanding property of production of the hot‐electron component which can be controlled by changing the working gas pressure. Utilizing such outstanding properties, some typical studies on PWI are introduced. An azimuthally asymmetric confinement depending on the direction of magnetic field lines, particularly for energetic electrons, has been found. Some discussions on the physical mechanisms are given. IEEJ Trans 2011 DOI: 10.1002/tee.21801

Ultraviolet irradiance measurement and modeling for evaluating the effectiveness of in-duct ultraviolet germicidal irradiation devices

This study uses ray-tracing software to calculate the fluence distribution in ultraviolet germicidal irradiation devices with different surface reflectivities and lamp configurations. Of five validation cases considered, one incorporating anisotropic duct surface reflectivity and wind-chill correction of lamp output gave the best agreement with planar irradiance measurements (mean error –3%, standard deviation 9%). The ray-tracing software was used as a validated design tool to evaluate two typical in-duct ultraviolet germicidal irradiation devices (Cases 6 and 7). Four identical UVC lamps were modeled inside a rectangular duct. The lamps were either arranged in parallel or cross flow, and spherical irradiance values along the flow path were compared. Without accounting for the thermal effect on lamp output, an ultraviolet germicidal irradiation device placed in a cross flow would give a higher average UV irradiance. This benefit would be practical when a sufficient straight run is provided in a ventilation system. However, a lamp in parallel flow would produce a more uniform UV irradiance field near the center of the device. Changing the thermal conditions would have significant impact on lamp outputs. Arranging lamps in a parallel flow would provide a higher total irradiance at low temperature and high flow conditions, especially for lamps with outputs lower than the simulated lamps and lamps without sleeves.

TU-C-BRB-07: Comparison of Preclinical and Clinical Conformal Radiation Therapy Techniques and Protocols to Establish a Translational Pathway

Purpose: The purpose of this study was to compare the techniques and protocols used in clinical radiation therapy and recently developed preclinical image guided micro irradiation to establish a link between small animal conformal irradiation and clinical treatment protocols. This work will establish protocols that, according to treatment site, will facilitate the translation of conclusions from radiobiological experiments to clinical applications, fostering the advancement of radiotherapy.Methods: Data was gathered using our small animal image guided micro irradiation device, the microIGRT, as an example of preclinical techniques which mimic equivalent clinical treatment protocols. The microIGRT utilizes fractionated treatments, multibeam irradiations, modulated beams, image guided treatment verification, and doses to emulate clinical protocols. Consequently, it is well suited to establish parametric comparisons between clinical and preclinical techniques. In this study, we concentrated on two treatment sites, brain and lung, to define treatment conformality index, homogeneity, penumbra, PDD, and fractionated doses to establish a link to guide radiobiological experiments using clinical protocols as a gold standard. Results: Three and five beam irradiations were delivered to a small animal body and head phantom with radiochromic film to simulate lung and braintreatment. A three beam irradiation to the lung yielded a 625 um penumbra. Compare this value with a human treatment penumbra of 1 cm, and penumbra scales as the ratio between body sizes. The homogeneity of our system is similar to the 10% typically used in clinical treatment planning.Conclusions: By comparing preclinical and clinical treatment metrics, the extent of translation can be determined and improved, leading to better understanding of preclinical results and improved correlation with clinical procedures. This will lead to more clinically based preclinical experiments and improve translation efficiency between the two testing environments, thus providing new clinical treatment strategies and improved human cancer treatment.

SU-E-T-399: Dosimetric and Geometric Evaluation of a Novel Stereotactic Radiotherapy Device for Breast Cancer: The GammaPod.

A dedicated stereotactic irradiation device, the GammaPodTM, was developed to treat early stage breast cancer. This study presents the first description of the dosimetric and geometric characteristics from the prototype unit. The GammaPod stereotactic radiotherapy device is an assembly of a hemi-spherical source carrier containing 36 Co-60 sources, a tungsten collimator, a dynamically controlled treatment table and a breast immobilization cup embedded with a stereotactic coordinate system. The source carrier and the variable-size collimator rotate synchronously to form 36 non-coplanar, concentric arcs focused at the isocenter. The treatment table enables motion in three dimensions facilitating continuous dose painting in comparison to a sphere packing approach. Geometric and dosimetric evaluations and a method for absorbed dose calibration are provided. Dosimetric verifications of the dynamically delivered plans are performed for eight patients in hypothetical pre-op, post-op and dose painting treatment scenarios. Loaded with a cumulative activity of 4320 Ci, the GammaPod unit delivers 5.31 Gy/min at the isocenter. Due to non-coplanar beam arrangement and dynamic dose shaping features, the GammaPod delivers uniform doses to the targets with excellent conformity. The spatial accuracy of the device is less than 1 mm. Single shot profiles with the 25 mm collimator are measured with radiochromic film and found to be in good agreement with respect to the MC based calculations (congruence of FWHM less than 1 mm). Dosimetric verifications corresponding to all treatment plans corresponding to three target scenarios for each of the eight patients demonstrated Gamma index pass rates greater than 97%. The first description of the dosimetric and geometric evaluation of the GammaPod was performed. The observed level of agreement between the treatment planning system calculations and dosimetric measurements has confirmed that the system can deliver highly complex treatment plans with remarkable geometric and dosimetric accuracy. C Yu and J Zhang have commercial affiliations with Xcision Medical Systems.