bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐C‐204‐01: A Fast Analytical Approach for Prompt Gamma and PET Predictions in a TPS for Proton Range Verification
Authors: Kroniger K , Herzog M , Landry G , Traneus E , Dedes G , Parodi K
Published: June 2015

Purpose:

We describe and demonstrate a fast analytical tool for prompt‐gamma emission prediction based on filter functions applied on the depth dose profile. We present the implementation in a treatment planning system (TPS) of the same algorithm for positron emitter distributions.

Methods:

The prediction of the desired observable is based on the convolution of filter functions with the depth dose profile. For both prompt‐gammas and positron emitters, the results of Monte Carlo simulations (MC) are compared with those of the analytical tool. For prompt‐gamma emission from inelastic proton‐induced reactions, homogeneous and inhomogeneous phantoms alongside with patient data are used as irradiation targets of mono‐energetic proton pencil beams. The accuracy of the tool is assessed in terms of the shape of the analytically calculated depth profiles and their absolute yields, compared to MC. For the positron emitters, the method is implemented in a research RayStation TPS and compared to MC predictions. Digital phantoms and patient data are used and positron emitter spatial density distributions are analyzed.

Results:

Calculated prompt‐gamma profiles agree with MC within 3 % in terms of absolute yield and reproduce the correct shape. Based on an arbitrary reference material and by means of 6 filter functions (one per chemical element), profiles in any other material composed of those elements can be predicted. The TPS implemented algorithm is accurate enough to enable, via the analytically calculated positron emitters profiles, detection of range differences between the TPS and MC with errors of the order of 1–2 mm.

Conclusion:

The proposed analytical method predicts prompt‐gamma and positron emitter profiles which generally agree with the distributions obtained by a full MC. The implementation of the tool in a TPS shows that reliable profiles can be obtained directly from the dose calculated by the TPS, without the need of full MC simulation.
SU‐C‐204‐02: Improved Patient‐Specific Optimization of the Stopping Power Calibration for Proton Therapy Planning Using a Single Proton Radiography
Authors: Rinaldi I , Parodi K , Krah N
Published: June 2015

Purpose:

We present an improved method to calculate patient‐specific calibration curves to convert X‐ray computed tomography (CT) Hounsfield Unit (HU) to relative stopping powers (RSP) for proton therapy treatment planning.

Methods:

By optimizing the HU‐RSP calibration curve, the difference between a proton radiographic image and a digitally reconstructed X‐ray radiography (DRR) is minimized. The feasibility of this approach has previously been demonstrated. This scenario assumes that all discrepancies between proton radiography and DRR originate from uncertainties in the HU‐RSP curve. In reality, external factors cause imperfections in the proton radiography, such as misalignment compared to the DRR and unfaithful representation of geometric structures (“blurring”). We analyze these effects based on synthetic datasets of anthropomorphic phantoms and suggest an extended optimization scheme which explicitly accounts for these effects. Performance of the method is been tested for various simulated irradiation parameters. The ultimate purpose of the optimization is to minimize uncertainties in the HU‐RSP calibration curve. We therefore suggest and perform a thorough statistical treatment to quantify the accuracy of the optimized HU‐RSP curve.

Results:

We demonstrate that without extending the optimization scheme, spatial blurring (equivalent to FWHM=3mm convolution) in the proton radiographies can cause up to 10% deviation between the optimized and the ground truth HU‐RSP calibration curve. Instead, results obtained with our extended method reach 1% or better correspondence. We have further calculated gamma index maps for different acceptance levels. With DTA=0.5mm and RD=0.5%, a passing ratio of 100% is obtained with the extended method, while an optimization neglecting effects of spatial blurring only reach ∼90%.

Conclusion:

Our contribution underlines the potential of a single proton radiography to generate a patient‐specific calibration curve and to improve dose delivery by optimizing the HU‐RSP calibration curve as long as all sources of systematic incongruence are properly modeled.
SU‐C‐204‐03: In‐Vivo Range Verification and Tissue Response to Proton Radiotherapy Using Prompt Gamma Volume Histograms
Authors: Polf J , Lin M
Published: June 2015

Purpose:

To study if prompt gamma (PG) volume histograms created from PG images acquired during treatment delivery can be used to identify changes to beam range and tissue composition in response to proton radiotherapy.

Methods:

Monte Carlo simulations of a single field from a single treatment fraction (100 cGy) for prostate cancer were performed for the cases of: 1) an ideal patient setup, 1) a setup shift in the superior direction and 2) a reduction in oxygen concentration in the tumor. For each case, the 3 ‐Dimsional dose delivery and elemental PG emission in the patient for the treatment fraction were recorded and imported into a commercial treatment planning system. Changes in the dose volume histograms (DVH), as well as the PG volume histograms (PG‐VH) for the PG emission from oxygen and for the total PG emission (from all elements) were analyzed.

Results:

For the 1 cm superior shift, the prostate DVH and total PG‐VH both shifted toward lower doses with the shape of the curves remaining nearly unchanged, resulting in the DVH V95 dropping from 100 cGy to 90 cGy. For the total PG‐VH, the V95 fell from 50 to 38. For the reduced oxygen case, both the DVH and PG‐VH had a much different shape than for the ideal case, with a significant downward slope in the curves as a function of dose.

Conclusions:

The shift in the prostate PG‐VH for a superior shift in the patient setup correlated well with the DVH indicating it is possible to detect setup errors by analyzing the PG‐VH from prompt gamma images obtained during daily proton treatment delivery. Additionally, it may be possible to detect changes in the elemental concentrations of irradiated tissues by analyzing the shape of the PG‐VH.
SU‐C‐207‐01: Four‐Dimensional Inverse Geometry Computed Tomography: Concept and Its Validation
Authors: Kim K , Kim D , Kim T , Kang S , Cho M , Shin D , Suh T
Published: June 2015

Purpose:

In past few years, the inverse geometry computed tomography (IGCT) system has been developed to overcome shortcomings of a conventional computed tomography (CT) system such as scatter problem induced from large detector size and cone‐beam artifact. In this study, we intend to present a concept of a four‐dimensional (4D) IGCT system that has positive aspects above all with temporal resolution for dynamic studies and reduction of motion artifact.

Methods:

Contrary to conventional CT system, projection data at a certain angle in IGCT was a group of fractionated narrow cone‐beam projection data, projection group (PG), acquired from multi‐source array which have extremely short time gap of sequential operation between each of sources. At this, for 4D IGCT imaging, time‐related data acquisition parameters were determined by combining multi‐source scanning time for collecting one PG with conventional 4D CBCT data acquisition sequence. Over a gantry rotation, acquired PGs from multi‐source array were tagged time and angle for 4D image reconstruction. Acquired PGs were sorted into 10 phase and image reconstructions were independently performed at each phase. Image reconstruction algorithm based upon filtered‐backprojection was used in this study.

Results:

The 4D IGCT had uniform image without cone‐beam artifact on the contrary to 4D CBCT image. In addition, the 4D IGCT images of each phase had no significant artifact induced from motion compared with 3D CT.

Conclusion:

The 4D IGCT image seems to give relatively accurate dynamic information of patient anatomy based on the results were more endurable than 3D CT about motion artifact. From this, it will be useful for dynamic study and respiratory‐correlated radiation therapy.

This work was supported by the Industrial R&D program of MOTIE/KEIT [10048997, Development of the core technology for integrated therapy devices based on real‐time MRI guided tumor tracking] and the Mid‐career Researcher Program (2014R1A2A1A10050270) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.
SU‐C‐201‐01: Investigation of the Effects of Scintillator Surface Treatment On Light Output Measurements with SiPM Detectors
Authors: Valenciaga Y , Prout D , Chatziioannou A
Published: June 2015

Purpose:

To examine the effect of different scintillator surface treatments (BGO crystals) on the fraction of scintillation photons that exit the crystal and reach the photodetector (SiPM).

Methods:

Positron Emission Tomography is based on the detection of light that exits scintillator crystals, after annihilation photons deposit energy inside these crystals. A considerable fraction of the scintillation light gets trapped or absorbed after going through multiple internal reflections on the interfaces surrounding the crystals. BGO scintillator crystals generate considerably less scintillation light than crystals made of LSO and its variants. Therefore, it is crucial that the small amount of light produced by BGO exits towards the light detector. The surface treatment of scintillator crystals is among the factors affecting the ability of scintillation light to reach the detectors. In this study, we analyze the effect of different crystal surface treatments on the fraction of scintillation light that is detected by the solid state photodetector (SiPM), once energy is deposited inside a BGO crystal. Simulations were performed by a Monte Carlo based software named GATE, and validated by measurements from individual BGO crystals coupled to Philips digital‐SiPM sensor (DPC‐3200).

Results:

The results showed an increment in light collection of about 4 percent when only the exit face of the BGO crystal, is unpolished; compared to when all the faces are polished. However, leaving several faces unpolished caused a reduction of at least 10 percent of light output when the interaction occurs as far from the exit face of the crystal as possible compared to when it occurs very close to the exit face.

Conclusion:

This work demonstrates the advantages on light collection from leaving unpolished the exit face of BGO crystals. The configuration with best light output will be used to obtain flood images from BGO crystal arrays coupled to SiPM sensors.
SU‐D‐204‐07: Comparison of AAPM TG150 Draft Image Receptor Tests with Vendor Automated QC Tests for Five Mobile DR Units
Authors: Li G , Greene T , Nishino T , Willis C
Published: June 2015

Purpose:

To determine the consistency of digital detector (DR) tests recommended by AAPM TG150 and tests provided by commercially available DirectView Total Quality Tool (TQT).

Methods:

The DR tests recommended by the TG150 Detector Subgroup[1] were performed on 4 new Carestream DRX‐Revolution and one Carestream DRX1C retrofit of a GE AMX‐4 that had been in service for three years. After detector calibration, flat‐field images plus images of two bar patterns oriented parallel and perpendicular to the A‐C axis, were acquired at conditions recommended by TG150. Raw images were harvested and then analyzed using a MATLAB software previously validated[2,3,4]. Data were analyzed using ROIs of two different dimensions: 1) 128 × 128 ROIs matching the detector electronics; and 2) 256 × 256 ROIs, each including 4 adjacent smaller ROIs. TG150 metrics from 128 × 128 ROIs were compared to TQT metrics, which are also obtained from 128 × 128 ROIs[5].

Results:

The results show that both TG150 and TQT measurements were consistent among these detectors. Differences between TG150 and TQT values appear systematic. Compared with 128 × 128 ROIs, noise and SNR non‐uniformity were lower with 256 × 256 ROIs, although signal non‐uniformity was similar, indicating detectors were appropriately calibrated for gain and offset. MTF of the retrofit unit remained essentially the same between 2012 and 2015, but was inferior to the new units. The older generator focal spot is smaller (0.75mm vs. 1.2mm), and the SID for acquisition is 182cm as well, so focal spot dimensions cannot explain the difference. The difference in MTF may be secondary to differences in generator X‐ray spectrum or by unannounced changes in detector architecture. Further investigation is needed.

Conclusion:

The study shows that both TG150 and TQT tests are consistent. The numerical value of some metrics are dependent on ROI size.
SU‐D‐207‐01: Markerless Respiratory Motion Tracking with Contrast Enhanced Thoracic Cone Beam CT Projections
Authors: Chao M , Brousmiche S , Yuan Y , Rosenzweig K , Lo Y
Published: June 2015

Purpose:

To develop a novel technique to enhance the image contrast of clinical cone beam CT projections and extract respiratory signals based on anatomical motion using the modified Amsterdam Shroud (AS) method to benefit image guided radiation therapy.

Methods:

Thoracic cone beam CT projections acquired prior to treatment were preprocessed to increase their contrast for better respiratory signal extraction. Air intensity on raw images was firstly estimated and then applied to correct the projections to generate new attenuation images that were subsequently improved with deeper anatomy feature enhancement through taking logarithm operation, derivative along superior‐inferior direction, respectively. All pixels on individual post‐processed two dimensional images were horizontally summed to one column and all projections were combined side by side to create an AS image from which patient's respiratory signal was extracted. The impact of gantry rotation on the breathing signal rendering was also investigated. Ten projection image sets from five lung cancer patients acquired with the Varian Onboard Imager on 21iX Clinac (Varian Medical Systems, Palo Alto, CA) were employed to assess the proposed technique.

Results:

Application of the air correction on raw projections showed that more than an order of magnitude of contrast enhancement was achievable. The typical contrast on the raw projections is around 0.02 while that on attenuation images could greater than 0.5. Clear and stable breathing signal can be reliably extracted from the new images while the uncorrected projection sets failed to yield clear signals most of the time.

Conclusion:

Anatomy feature plays a key role in yielding breathing signal from the projection images using the AS technique. The air correction process facilitated the contrast enhancement significantly and attenuation images thus obtained provides a practical solution to obtaining markerless breathing motion tracking.
SU‐D‐207‐04: GPU‐Based 4D Cone‐Beam CT Reconstruction Using Adaptive Meshing Method
Authors: Zhong Z , Gu X , Iyengar P , Mao W , Guo X , Wang J
Published: June 2015

Purpose:

Due to the limited number of projections at each phase, the image quality of a four‐dimensional cone‐beam CT (4D‐CBCT) is often degraded, which decreases the accuracy of subsequent motion modeling. One of the promising methods is the simultaneous motion estimation and image reconstruction (SMEIR) approach. The objective of this work is to enhance the computational speed of the SMEIR algorithm using adaptive feature‐based tetrahedral meshing and GPU‐based parallelization.

Methods:

The first step is to generate the tetrahedral mesh based on the features of a reference phase 4D‐CBCT, so that the deformation can be well captured and accurately diffused from the mesh vertices to voxels of the image volume. After the mesh generation, the updated motion model and other phases of 4D‐CBCT can be obtained by matching the 4D‐CBCT projection images at each phase with the corresponding forward projections of the deformed reference phase of 4D‐CBCT. The entire process of this 4D‐CBCT reconstruction method is implemented on GPU, resulting in significantly increasing the computational efficiency due to its tremendous parallel computing ability.

Results:

A 4D XCAT digital phantom was used to test the proposed mesh‐based image reconstruction algorithm. The image Result shows both bone structures and inside of the lung are well‐preserved and the tumor position can be well captured. Compared to the previous voxel‐based CPU implementation of SMEIR, the proposed method is about 157 times faster for reconstructing a 10 ‐phase 4D‐CBCT with dimension 256×256×150.

Conclusion:

The GPU‐based parallel 4D CBCT reconstruction method uses the feature‐based mesh for estimating motion model and demonstrates equivalent image Result with previous voxel‐based SMEIR approach, with significantly improved computational speed.
SU‐D‐201‐05: Phantom Study to Determine Optimal PET Reconstruction Parameters for PET/MR Imaging of Y‐90 Microspheres Following Radioembolization
Authors: Maughan N , Conti M , Parikh P , Faul D , Laforest R
Published: June 2015

Purpose:

Imaging Y‐90 microspheres with PET/MRI following hepatic radioembolization has the potential for predicting treatment outcome and, in turn, improving patient care. The positron decay branching ratio, however, is very small (32 ppm), yielding images with poor statistics even when therapy doses are used. Our purpose is to find PET reconstruction parameters that maximize the PET recovery coefficients and minimize noise.

Methods:

An initial 7.5 GBq of Y‐90 chloride solution was used to fill an ACR phantom for measurements with a PET/MRI scanner (Siemens Biograph mMR). Four hot cylinders and a warm background activity volume of the phantom were filled with a 10:1 ratio. Phantom attenuation maps were derived from scaled CT images of the phantom and included the MR phased array coil. The phantom was imaged at six time points between 7.5–1.0 GBq total activity over a period of eight days. PET images were reconstructed via OP‐OSEM with 21 subsets and varying iteration number (1–5), post‐reconstruction filter size (5–10 mm), and either absolute or relative scatter correction. Recovery coefficients, SNR, and noise were measured as well as total activity in the phantom.

Results:

For the 120 different reconstructions, recovery coefficients ranged from 0.1–0.6 and improved with increasing iteration number and reduced post‐reconstruction filter size. SNR, however, improved substantially with lower iteration numbers and larger post‐reconstruction filters. From the phantom data, we found that performing 2 iterations, 21 subsets, and applying a 5 mm Gaussian post‐reconstruction filter provided optimal recovery coefficients at a moderate noise level for a wide range of activity levels.

Conclusion:

The choice of reconstruction parameters for Y‐90 PET images greatly influences both the accuracy of measurements and image quality. We have found reconstruction parameters that provide optimal recovery coefficients with minimized noise. Future work will include the effects of the body matrix coil and off‐center measurements.
SU‐D‐210‐01: Automated Depth of Penetration Measurements for Quality Assurance in Ultrasound
Authors: Rubert N , Zagzebski J
Published: June 2015

Purpose:

Subjective assessment of image quality metrics is a current limitation of most ultrasound quality assurance (QA) programs. Here, depth of penetration (DOP) assessments for sensitivity checks are routinely done. We demonstrate the performance of an automated method for DOP measurement for ultrasound QA.

Methods:

Subjective DOP was assessed by examining an image of a QA phantom and determining the depth where the echo data fades into noise. To assess DOP objectively, a phantom image was recorded followed by a second, “noise image” with the transducer held in air. Phantom and noise images were laterally averaged; the DOP was the depth where phantom image pixel value intersected 1.4X noise image values. During annual QA, DOP was evaluated subjectively by a single observer on a number of probes and compared with objective DOP measurements. Additionally, the objective method's measurement variance and sensitivity to transmit power was examined using a linear‐array transducer. To examine variance, the DOP measurement was repeated with 25 phantom images recorded at uncorrelated planes with transmit power at either 100% or 1%. DOP was also measured as the transmit power was varied in fine steps between 0.1% and 100%.

Results:

Agreement within 10% of the mean DOP was found between objective and subjective methods for most cases. A small number of cases showed a difference between 10% and 18%. Using the linear‐array, DOP was found to fall off as a power law with the transmit power. At 100% and 1% transmit power, the standard deviation of the DOP measurement was found to be 0.9 mm at DOP's of 8.16 and 6.30 mm on average.

Conclusion:

Objective image quality assessment is necessary to improve the utility of routine ultrasound QA. We found that objective DOP measurements show good agreement with subjective assessments of DOP while showing little variance.
SU‐D‐210‐05: The Accuracy of Raw and B‐Mode Image Data for Ultrasound Speckle Tracking in Radiation Therapy
Authors: O'shea T , Bamber J , Harris E
Published: June 2015

Purpose:

For ultrasound speckle tracking there is some evidence that the envelope‐detected signal (the main step in B‐mode image formation) may be more accurate than raw ultrasound data for tracking larger inter‐frame tissue motion. This study investigates the accuracy of raw radio‐frequency (RF) versus non‐logarithmic compressed envelope‐detected (B‐mode) data for ultrasound speckle tracking in the context of image‐guided radiation therapy.

Methods:

Transperineal ultrasound RF data was acquired (with a 7.5 MHz linear transducer operating at a 12 Hz frame rate) from a speckle phantom moving with realistic intra‐fraction prostate motion derived from a commercial tracking system. A normalised cross‐correlation template matching algorithm was used to track speckle motion at the focus using (i) the RF signal and (ii) the B‐mode signal. A range of imaging rates (0.5 to 12 Hz) were simulated by decimating the imaging sequences, therefore simulating larger to smaller inter‐frame displacements. Motion estimation accuracy was quantified by comparison with known phantom motion.

Results:

The differences between RF and B‐mode motion estimation accuracy (2D mean and 95% errors relative to ground truth displacements) were less than 0.01 mm for stable and persistent motion types and 0.2 mm for transient motion for imaging rates of 0.5 to 12 Hz. The mean correlation for all motion types and imaging rates was 0.851 and 0.845 for RF and B‐mode data, respectively. Data type is expected to have most impact on axial (Superior‐Inferior) motion estimation. Axial differences were <0.004 mm for stable and persistent motion and <0.3 mm for transient motion (axial mean errors were lowest for B‐mode in all cases).

Conclusions:

Using the RF or B‐mode signal for speckle motion estimation is comparable for translational prostate motion. B‐mode image formation may involve other signal‐processing steps which also influence motion estimation accuracy. A similar study for respiratory‐induced motion would also be prudent.

This work is support by Cancer Research UK Programme Grant C33589/A19727.
SU‐D‐210‐06: Feasibility for Monitoring the Head of the Pancreas Motion Through a Surrogate Using Ultrasound During Radiation Therapy Delivery
Authors: Omari E , Noid G , Ehlers C , Erickson B , Quiroz F , Cooper D , Lachaine M , Li X
Published: June 2015

Purpose:

Substantial target motion during the delivery of radiation therapy (RT) for pancreatic cancer is well recognized as a major limiting factor on RT effectiveness. The aim of this work is to monitor intra‐fractional motion of the pancreas using ultrasound during RT delivery.

Methods:

Transabdominal Ultrasound B‐mode images were collected from 5 volunteers using a research version of the Clarity Autoscan System (Elekta). The autoscan transducer with center frequency of 5 MHz was utilized for the scans. Imaging parameters were adjusted to acquire images at the desired depth with good contrast and a wide sweep angle. Since well‐defined boundaries of the pancreas can be difficult to find on ultrasound B‐mode images, the portal vein was selected as a surrogate for motion estimation of the head of the pancreas. The selection was due to its anatomical location posterior to the neck of the pancreas and close proximity to the pancreas head. The portal vein was contoured on the ultrasound images acquired during simulation using the Clarity Research AFC Workstation software. Volunteers were set up in a similar manner to the simulation for their monitoring session and the ultrasound transducer was mounted on an arm fixed to the couch. A video segment of the portal vein motion was captured.

Results:

The portal vein was visualized and segmented. Successful monitoring sessions of the portal vein were observed. In addition, our results showed that the ultrasound transducer itself reduces breathing related motion. This is analogous to the use of a compression plate to suppress respiration motion during thorax or abdominal irradiation.

Conclusion:

We demonstrate the feasibility of tracking the pancreas through the localization of the portal vein using abdominal ultrasound. This will allow for real‐time tracking of the intra‐fractional motion to justify PTV‐margin and to account for unusual motions, thus, improving normal tissue sparing.

This research was funding in part by Elekta Inc.
SU‐E‐E‐05: Improving Contouring Precision and Consistency for Physicians‐In‐Training with Simple Lab Experiments
Authors: Ma L , Larson D A
Published: June 2015

Purpose:

Target contouring for high‐dose treatments such as radiosurgery of brain metastases is highly critical in eliminating marginal failure and reducing complications as shown by recent clinical studies. In order to improve contouring accuracy and practice consistency for the procedure, we introduced a self‐assessed physics lab practice for the physicians‐in‐training.

Methods:

A set of commercially acquired high‐precision PMMA plastic spheres were randomly embedded in a Styrofoam block and then scanned with the CT/MR via the clinical procedural imaging protocol. A group of first‐year physicians‐in‐training (n=6) from either neurosurgery or radiation oncology department were asked to contour the scanned objects (diameter ranged from 0.4 cm to 3.8 cm). These user‐defined contours were then compared with the ideal contour sets of object shape for self assessments to determine the maximum areas of the observed discrepancies and method of improvements.

Results:

The largest discrepancies from initial practice were consistently found to be located near the extreme longitudinal portions of the target for all the residents. Discrepancy was especially prominent when contouring small objects < 1.0 cm in diameters. For example, the mean volumes rendered from the initial contour data set differed from the ideal data set by 7.7%±6.6% for the participants (p> 0.23 suggesting agreement cannot be established). However, when incorporating a secondary imaging scan such as reconstructed coronal or sagittal images in a repeat practice, the agreement was dramatically improved yielding p<0.02 in agreement with the reference data set for all the participants.

Conclusion:

A simple physics lab revealed a common pitfall in contouring small metastatic brain tumors for radiosurgical procedures and provided a systematic tool for physicians‐in‐training in improving their clinical contouring skills.

Dr Ma is current a board member of international stereotactic radiosurgical society
SU‐E‐E‐07: An Adaptable Approach for Education On Medical Physics at Undergraduate and Postgraduate Levels
Authors: Miller‐Clemente R , Mendez‐Perez L
Published: June 2015

Purpose:

To contribute to the professional profile of future medical physicists, technologists and physicians, and implement an adaptable educational strategy at both undergraduate and postgraduate levels.

Methods:

The Medical Physics Block of Electives (MPBE) designed was adapted to the Program of B.S. in Physics. The conferences and practical activities were developed with participatory methods, with interdisciplinary collaboration from research institutions and hospitals engaged on projects of Research, Development and Innovation (RDI). The scientific education was implemented by means of critical analysis of scientific papers and seminars where students debated on solutions for real research problems faced by medical physicists. This approach included courses for graduates not associated to educational programs of Medical Physics (MP).

Results:

The implementation of the MPBE began in September 2014, with the electives of Radiation MP and Introduction to Nuclear Magnetic Resonance. The students of second year received an Introduction to MP. This initiative was validated by the departmental Methodological Workshop, which promoted the full implementation of the MPBE. Both postgraduated and undergraduate trainees participated in practices with our DICOM viewer system, a local prototype for photoplethysmography and a home‐made interface for ROC analysis, built with MATLAB. All these tools were designed and constructed in previous RDI projects. The collaborative supervision of University's researchers with clinical medical physicists will allow to overcome the limitations of residency in hospitals, to reduce the workload for clinical supervisors and develop appropriate educational activities.

Conclusion:

We demonstrated the feasibility of adaptable educational strategies, considering available resources. This provides an innovative way for prospective medical physicists, technologists and radiation oncologists. This strategy can be implemented in several regions without formal programs of MP, like most of developing countries. Starting with undergraduate students would allow to reach appropriate certification faster than most of traditional or alternative approaches for education on MP.

The authors acknowledge Radiation Consulting Group, LLC, an Arizona Corporation which promotes the use of ionizing radiation in the healing arts, for the “Oscar Luis Caballero” travel grant. The authors thanks to professors Meisbel Daudinot, David Adame and Alexander Pascau for the practices through imagis, imageROC and ANGIODIN PD3000 respectively.
SU‐E‐E‐08: Applications of the Quantization of Coupled Circuits in Radiation Physics (design of Klystron, Bremsstrahlung, Synchrotron)
Authors: Ulmer W
Published: June 2015

Purpose:

During the past decade the quantization of coupled/forced electromagnetic circuits with or without Ohm's resistance has gained the subject of some fundamental studies, since even problems of quantum electrodynamics can be solved in an elegant manner, e.g. the creation of quantized electromagnetic fields. In this communication, we shall use these principles to describe optimization procedures in the design of klystrons, synchrotron irradiation and high energy bremsstrahlung.

Methods:

The base is the Hamiltonian of an electromagnetic circuit and the extension to coupled circuits, which allow the study of symmetries and perturbed symmetries in a very apparent way (SU2, SU3, SU4). The introduction resistance and forced oscillators for the emission and absorption in such coupled systems provides characteristic resonance conditions, and atomic orbitals can be described by that. The extension to virtual orbitals leads to creation of bremsstrahlung, if the incident electron (velocity v nearly c) is described by a current, which is associated with its inductivitance and the virtual orbital to the charge distribution (capacitance). Coupled systems with forced oscillators can be used to amplify drastically the resonance frequencies to describe klystrons and synchrotron radiation.

Results:

The cross‐section formula for bremsstrahlung given by the propagator method of Feynman can readily be derived. The design of klystrons and synchrotrons inclusive the radiation outcome can be described and optimized by the determination of the mutual magnetic couplings between the oscillators induced by the currents.

Conclusions:

The presented methods of quantization of circuits inclusive resistance provide rather a straightforward way to understand complex technical processes such as creation of bremsstrahlung or creation of radiation by klystrons and synchrotrons. They can either be used for optimization procedures and, last but not least, for pedagogical purposes with regard to a qualified understanding of radiation physics for students.
SU‐E‐E‐11: Novel Matching Module for Respiration‐Gated Motion Tumor of Cone‐Beam Computed Tomography (CBCT) to 4DCT
Authors: Yu P , Tsai Y , Nien H , Chiu Y , Chang H , Lin C , Fu P , Chang C , Wu C
Published: June 2015

Purpose:

Four dimensional computed tomography (4DCT) scans reliably record whole respiratory phase and generate internal target volumes (ITV) for radiotherapy planning. However, image guiding with cone‐beam computed tomography (CBCT) cannot acquire all or specific respiratory phases. This study was designed to investigate the correlation between average CT and Maximum Intensity Projection (MIP) from 4DCT and CBCT.

Methods:

Retrospective respiratory gating were performed by GE Discovery CT590 RT. 4DCT and CBCT data from CRIS Dynamic Thorax Phantom with simulated breathing mode were analyzed. The lung tissue equivalent material encompassed 3 cm sphere tissue equivalent material. Simulated breathing cycle period was set as 4 seconds, 5 seconds and 6 seconds for representing variation of patient breathing cycle time, and the sphere material moved toward inferior and superior direction with 1 cm amplitude simulating lung tumor motion during respiration.

Results:

Under lung window, the volume ratio of CBCT scans to ITVs derived from 10 phases average scans was 1.00 ± 0.02, and 1.03 ± 0.03 for ratio of CBCT scans to MIP scans. Under abdomen window, the ratio of CBCT scans to ITVs derived from 10 phases average scans was 0.39 ± 0.06, and 0.06 ± 0.00 for ratio of CBCT scans to MIP scans. There was a significant difference between lung window Result and abdomen window Result. For reducing image guiding uncertainty, CBCT window was set with width 500 and level‐250. The ratio of CBCT scans to ITVs derived from 4 phases average scans with abdomen window was 1.19 ± 0.02, and 1.06 ± 0.01 for ratio of CBCT to MIP scans.

Conclusion:

CBCT images with suitable window width and level can efficiently reduce image guiding uncertainty for patient with mobile tumor. By our setting, we can match motion tumor to gating tumor location on planning CT more accurately neglecting other motion artifacts during CBCT scans.
SU‐E‐E‐16: The Application of Texture Analysis for Differentiation of Central Cancer From Atelectasis
Authors: Gao M , Fan T , Duan J
Published: June 2015

Purpose:

Prospectively assess the potential utility of texture analysis for differentiation of central cancer from atelectasis.

Methods:

0 consecutive central lung cancer patients who were referred for CT imaging and PET‐CT were enrolled. Radiotherapy doctor delineate the tumor and atelectasis according to the fusion imaging based on CT image and PET‐CT image. The texture parameters (such as energy, correlation, sum average, difference average, difference entropy), were obtained respectively to quantitatively discriminate tumor and atelectasis based on gray level co‐occurrence matrix (GLCM)

Results:

The texture analysis results showed that the parameters of correlation and sum average had an obviously statistical significance(P<0.05).

Conclusion:

the results of this study indicate that texture analysis may be useful for the differentiation of central lung cancer and atelectasis.
SU‐E‐P‐03: The Australian Clinical Dosimetry Service, a Bespoke National Solution
Authors: Williams I , Lehmann J , Lye J , Kenny J , Alves A , Dunn L , Kron T
Published: June 2015

Purpose:

The Australian Clinical Dosimetry Service, (ACDS) was a pilot program to enable the Australian Government to determine whether a locally designed audit program was suitable for mitigating dosimetric error risk to radiotherapy patients within Australia. The outcomes from four years of operations will be presented and discussed with a focus why and how the pilot requirements were met. The consequnces of success will be considered, the lessons learnt from the pilot program and how they are impacting the future ACDS design, operation and engagement with stakeholders.

Methods:

The ACDS was designed over 2010/11 by experts drawn from the three professions in consultation with the national Department of Health. The list of outcomes required over a three year pilot was expressed in a Memorandum of Understanding, (MoU) between Health and the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) which hosted the ACDS.

Results:

The ACDS has achieved all the MoU requirements. This paper describes how the staff within the ACDS engaged with the professional clinical workforce and provided a successful and functioning audit service. It identifies the strengths and weaknesses within the MoU and the ACDS structure and how the ACDS resolved a number of conflicting issues. It identifies the successes within the ACDS and how these were achieved. It provides details to assist and advise those seeking to design or modify national or regional auditing programs. Finally the paper reviews potential futures for the ACDS.

Conclusion:

The raw number of audits and outcomes indicate that the ACDS has met the MoU auditing requirements. The reasons for the ACDS’ success are highly dependent on: attracting quality staff who can respond with agility to changing situations, a high level of communication with the professional community, a high level of engagement by the community and an interested and engaged Federal Department.

The Australian Clinical Dosimetry Service is a joint initiative between the Australian Department of Health and the Australian Radiation Protection and Nuclear Safety Agency.
SU‐E‐P‐09: Compliance With Evidence‐Based Treatment Planning DVH Guidelines In An Academic Multi‐Site Radiation Oncology Practice Setting
Authors: D'souza W , Zhang B , Feigenberg S , D'souza G , Prado K , Regine W
Published: June 2015

Purpose:

To evaluate the compliance with evidence‐based treatment planning organ‐at‐risk (OAR) guidelines in a single institution with four practice sites.

Methods:

Two hundred thirteen head and neck cancer patients treated between September 2009 and September 2013 were retrospectively selected. Consensus treatment planning guidelines, including OAR dose constraints, were established based on institutional experience and published data. Data spanned a time period of 2 years prior to (n=112) and 2 years post‐enactment (n=101) of the guidelines. We investigated the differences in the frequency with which (1) OARs were contoured and (2) OAR DVH goals were met. Trends in the proportion with OAR contours over time was tested using linear regression. Trends in the proportion of contoured OARs achieving clinical DVH goals were similarly tested. The proportion of patients contoured and meeting DVH goals before and after guidelines was compared using a test of proportions.

Results:

When the proportion of cases with OAR contours before and after guidelines were compared, we observed an increase from 75% to 87% (p=0.02) for the brainstem, decrease from 97% to 88% (p=0.01) for the cord and increase from 47% to 77% (p<0.001) for the mandible. For the proportion of cases with OAR contours in which clinical goals were met, a significant decrease from 99% to 90% was observed for the cord V48<0.3% (p=0.001). A significant decrease in the proportion of cases with left parotid contours (from 92% to 73% (p=0.03)) was observed over 2 years after guideline enactment and the proportion meeting the clinical DVH goal of V30<50% increased significantly from 36% to 50% (p=0.007) over the 2 years after guidelines.

Conclusion:

The enactment of OAR planning guidelines resulted in an increase in OAR contour compliance, overall. In cases with OAR contours, there was little to no change in the proportion that met clinical goals.
SU‐E‐P‐11: Comparison of Image Quality and Radiation Dose Between Different Scanner System in Routine Abdomen CT
Authors: Liao S , Wang Y , Weng H
Published: June 2015

Purpose

To evaluate image quality and radiation dose of routine abdomen computed tomography exam with the automatic current modulation technique (ATCM) performed in two different brand 64‐slice CT scanners in our site.

Materials and Methods

A retrospective review of routine abdomen CT exam performed with two scanners; scanner A and scanner B in our site. To calculate standard deviation of the portal hepatic level with a region of interest of 12.5 mm × 12.5mm represented to the image noise. The radiation dose was obtained from CT DICOM image information. Using Computed tomography dose index volume (CTDIv) to represented CT radiation dose. The patient data in this study were with normal weight (about 65–75 Kg).

Results

The standard deviation of Scanner A was smaller than scanner B, the scanner A might with better image quality than scanner B. On the other hand, the radiation dose of scanner A was higher than scanner B(about higher 50–60%) with ATCM. Both of them, the radiation dose was under diagnostic reference level.

Conclusion

The ATCM systems in modern CT scanners can contribute a significant reduction in radiation dose to the patient. But the reduction by ATCM systems from different CT scanner manufacturers has slightly variation. Whatever CT scanner we use, it is necessary to find the acceptable threshold of image quality with the minimum possible radiation exposure to the patient in agreement with the ALARA principle.
SU‐E‐P‐15: Technique Factor Modulation and Reference Plane Air Kerma Rates in Response to Simulated Patient Thickness Variations for a Sample of Current Generation Fluoroscopes
Authors: Wunderle K , Rakowski J , Dong F
Published: June 2015

Purpose:

To evaluate and compare approaches to technique factor modulation and air kerma rates in response to simulated patient thickness variations for four state‐of‐the‐art and one previous‐generation interventional fluoroscopes.

Methods:

A polymethyl methacrylate (PMMA) phantom was used as a tissue surrogate for the purposes of determining fluoroscopic reference plane air kerma rates, kVp, mA, and spectral filtration over a wide range of simulated tissue thicknesses. Data were acquired for each fluoroscopic and acquisition dose curve within a default abdomen or body imaging protocol.

Results:

The data obtained indicated vendor‐ and model‐specific variations in the approach to technique factor modulation and reference plane air kerma rates across a range of tissue thicknesses. Some vendors have made hardware advances increasing the radiation output capabilities of their fluoroscopes; this was evident in the acquisition air kerma rates. However, in the imaging protocol evaluated, all of the state‐of‐the‐art systems had relatively low air kerma rates in the fluoroscopic low‐dose imaging mode as compared to the previous‐generation unit. Each of the newest‐generation systems also employ copper filtration in the selected protocol in the acquisition mode of imaging; this is a substantial benefit, reducing the skin entrance dose to the patient in the highest dose‐rate mode of fluoroscope operation.

Conclusion:

Understanding how fluoroscopic technique factors are modulated provides insight into the vendor‐specific image acquisition approach and provides opportunities to optimize the imaging protocols for clinical practice. The enhanced radiation output capabilities of some of the fluoroscopes may, under specific conditions, may be beneficial; however, these higher output capabilities also have the potential to lead to unnecessarily high dose rates. Therefore, all parties involved in imaging, including the clinical team, medical physicists, and imaging vendors, must work together to ensure that adequate but not excessive radiation doses are used.
SU‐E‐P‐16: A Feasibility Study of Using Eclipse AAA for SRS Treatement
Authors: Lim S , LoSasso T
Published: June 2015

Purpose:

To commission Varian Eclipse AAA for SRS treatment and compare the accuracy with Brainlab iPlan system for clinical cases measured with radiochromic film.

Methods:

A 6MV AAA clinical model for a Varian TrueBeam STx is used as baseline. The focal spot and field size of the baseline model(BASE) are (1.75,0.75) and 40×40cm2 respectively. Maximum field sizes, output factors(St), FWHM focal spot and secondary source sizes are systematically adjusted to obtain an optimized model(OPT) by comparing the calculated PDD's, profiles, and output factors with measurements taken with a stereotactic diode(SD) and, cc01 and cc04 ion chambers in Blue Phantom. In‐phantom dose distributions of clinical SRS fields are calculated using the OPT and the clinical Brainlab iPlan pencil‐beam. Within the 90% isodose‐line(ROI), the average dose difference between the calculations and radiochromic film measurements are assessed.

Results:

The maximum field, focal spot and secondary source sizes for the OPT are 15×15cm2, (0,0), and 32.3mm respectively. The OPT St input at 1.0 and 2.0cm fields are increased by 4.5% and 1.5% from BASE. The calculated output of the BASE and OPT underestimate by 16.1%–3.2% respectively at 0.5×0.5cm2 field and 3.1%−0.02% respectively at 1.0×1.0cm2 field. The depth doses at 10cm are within 3.5% and 0.4% of measurements for 0.5×0.5 and 1.0×1.0cm2. The ROI dose of OPT and iPlan are within 1.6% and 0.6% of film measurements for 3.0cm clinical fields. For 1.0cm fields, the ROI dose of OPT underestimate 0.0–2.0% and iPlan overestimates 1.7–2.9% relative to measurements.

Conclusion:

The small field dose calculation of Eclipse AAA algorithm can be significantly improved by carefully adjusting the input parameters. The larger deviation of the OPT for 0.5×0.5cm2 field from measurements can be attributed to the lowest 1.0cm field size input limit of AAA. The OPT compares reasonably well with the iPlan pencil‐beam and measurements.