bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐P‐19: A National Collaborative Academic Medical Physics Network: Structure, Activity and Outcomes
Authors: Thwaites D
Published: June 2015

Purpose:

A national Australian inter‐university medical physics (MP) group was formed in 2011/12, supported by Department of Health Better Access to Radiation Oncology BARO) seed funding. Core membership includes the six universities providing postgraduate MP courses. Objectives include increasing capacity, development and efficiency of national academic MP structures/systems and hence supporting education, clinical training and research, for the MP workforce support. Although the BARO scheme focuses on Radiation Oncology, the group has wider MP interests.

Methods:

Two further BARO seed grants were achieved: 1) for networked academic activities, including shared‐resource teaching, eg using virtual reality systems; MP outreach to schools and undergraduates; developing web‐based student and registrar education/resources, etc.; and 2) for conjoint ‘translational research’ posts between universities and partner hospitals, to clinically progress advanced RT technologies and to support students and registrars. Each university received 0.5 FTE post from each grant over 2 years (total: $1.75M) and leveraged local additional partner funds.

Results:

Total funding: $4–5M. Overall there have been 35 (mainly overseas) postholders bringing specific expertise, beginning in early 2013. Periods in Australia have been from 0.25–2 years (median=1). As well as the education activities, research projects include lung/spine SBRT, 4D RT, FFF beams, technology assessment, complex treatment planning, imaging for radiation oncology, DIR, adaptive breast, datamining, radiomics,etc. Observed positive impacts include: increased interest in MP courses, training support, translational research infrastructure and/or clinical practice in the hospitals involved, plus increased collaboration and effectiveness between the universities. Posts are continuing beyond grant end using leveraged funds, providing the basis for sustainability of some posts.

Conclusion:

The BARO‐funded projects have cost‐effectively produced a range of positive impacts on training, research and practice in hospitals and between universities. The evaluation of the specific post roles and activities, and their outcomes, has produced focused recommendations on continuation and sustainability.

Funding was from the Australian federal Department of Health; leveraged funding was from partner universities and hospitals
SU‐E‐P‐30: Clinical Applications of Spatially Fractionated Radiation Therapy (GRID) Using Helical Tomotherapy
Authors: Zhang X , Penagaricano J , Liang X , Morrill S , Yan Y , Corry P , Griffin R , Paudel N , Vaneerat V Ratanatharathorn
Published: June 2015

Purpose:

To present the first clinical applications of Helical Tomotherapy‐based spatially fractionated radiotherapy (HT‐GRID) for deep seated tumors and associated dosimetric study.

Methods:

Ten previously treated GRID patients were selected (5 HT‐GRID and 5 LINAC‐GRID using a commercially available GRID block). Each case was re‐planned either in HT‐GRID or LINAC‐GRID for a total of 10 plans for both techniques using same prescribed dose of 20 Gy to maximum point dose of GRID GTV. For TOMO‐GRID, a programmable virtual TOMOGRID template mimicking a GRID pattern was generated. Dosimetric parameters compared included: GRID GTV mean dose (Dmean) and equivalent uniform dose (EUD), GRID GTV dose inhomogeneity (Ratio(valley/peak)), normal tissue Dmean and EUD, and other organs‐at‐risk(OARs) doses.

Results:

The median tumor volume was 634 cc, ranging from 182 to 4646 cc. Median distance from skin to the deepest part of tumor was 22cm, ranging from 8.9 to 38cm. The median GRID GTV Dmean and EUD was 10.65Gy (9.8–12.5Gy) and 7.62Gy (4.31–11.06Gy) for HT‐GRID and was 6.73Gy (4.44–8.44Gy) and 3.95Gy (0.14–4.2Gy) for LINAC‐GRID. The median Ratio(valley/peak) was 0.144(0.05–0.29) for HT‐GRID and was 0.055(0.0001–0.14) for LINAC‐GRID. For normal tissue in HT‐GRID, the median Dmean and EUD was 1.24Gy (0.34–2.54Gy) and 5.45 Gy(3.45–6.89Gy) and was 0.61 Gy(0.11–1.52Gy) and 6Gy(4.45–6.82Gy) for LINAC‐GRID. The OAR doses were comparable between the HT‐GRID and LINAC‐GRID. However, in some cases it was not possible to avoid a critical structure in LINAC‐GRID; while HT‐GRID can spare more tissue doses for certain critical structures.

Conclusion:

HT‐GRID delivers higher GRID GTV Dmean, EUD and Ratio(valley/peak) compared to LINAC‐GRID. HT‐GRID delivers higher Dmean and lower EUD for normal tissue compared to LINAC‐GRID. TOMOGRID template can be highly patient‐specific and allows adjustment of the GRID pattern to different tumor sizes and shapes when they are deeply‐seated and cannot be safely treated with LINAC‐GRID.
SU‐E‐P‐47: Evaluation of Improvement of Esophagus Sparing in SBRT Lung Patients with Biologically Based IMRT Optimization
Authors: Liang X , Penagaricano J , Paudel N , Zhang X , Morrill S , Corry P , Han E , Hardee M , Ratanatharathorn V
Published: June 2015

Purpose:

To study the potential of improving esophageal sparing for stereotactic body radiation therapy (SBRT) lung cancer patients by using biological optimization (BO) compared to conventional dose‐volume based optimization (DVO) in treatment planning.

Methods:

Three NSCLC patients (PTV (62.3cc, 65.1cc, and 125.1cc) adjacent to the heart) previously treated with SBRT were re‐planned using Varian Eclipse TPS (V11) using DVO and BO. The prescription dose was 60 Gy in 5 fractions normalized to 95% of the PTV volume. Plans were evaluated by comparing esophageal maximum doses, PTV heterogeneity (HI= D5%/D95%), and Paddick's conformity (CI) indices. Quality of the plans was assessed by clinically‐used IMRT QA procedures.

Results:

By using BO, the maximum dose to the esophagus was decreased 1384 cGy (34.6%), 502 cGy (16.5%) and 532 cGy (16.2%) in patient 1, 2 and 3 respectively. The maximum doses to spinal cord and the doses to 1000 cc and 1500 cc of normal lung were comparable in both plans. The mean doses (Dmean_hrt) and doses to 15cc of the heart (V15_hrt) were comparable for patient 1 and 2. However for patient 3, with the largest PTV, Dmean_hrt and V15_hrt increased by 62.2 cGy (18.3%) and 549.9 cGy (24.9%) respectively for the BO plans. The mean target HI of BO plans (1.13) was inferior to the DVO plans (1.07). The same trend was also observed for mean CI in BO plans (0.77) versus DVO plans (0.83). The QA pass rates (3%, 3mm) were comparable for both plans.

Conclusion:

This study demonstrated that the use of biological models in treatment planning optimization can substantially improve esophageal sparing without compromising spinal cord and normal lung doses. However, for the large PTV case (125.1cc) we studied here, Dmean_hrt and V15_hrt increased substantially. The target HI and CI were inferior in the BO plans.
SU‐E‐U‐01: Automatic Quantitative Analysis of Chronic Liver Disease Employing Shear Wave Ultrasound Elastography
Authors: Gatos I , Tsantis S , Skouroliakou A , Theotokas I , Zoumpoulis P , Kagadis G
Published: June 2015

Purpose:

The purpose of this study was to quantify liver elastic heterogeneity in Shear Wave Elastography (SWE) by using textural features and evaluating their diagnostic performance on differentiating healthy from chronic liver disease patients, taking biopsy results as the gold standard.

Methods:

Clinical material includes 16 healthy (F0) and 15 with Chronic Liver Disease (F1,F2,F3,F4) patients according to the Metavir staging system. All exams were performed using the Aixplorer ultrasound system with a SuperCurved SC6‐1 transducer. From the SWE‐QBox the RGB displayed elasticity data of Young's modulus were transformed from RGB color space into an elasticity matrix of gray tones, whose values varied from zero to the maximum elasticity measurement. Every pixel with no RGB‐values was set to ‘−1’ due to non‐valid elasticity value for that pixel. From the elastogram map 185 textural features were computed (5 from the gray‐tone histogram, 26 second order statistic features, extracted from the co‐occurrence matrices and 10 features extracted from the run‐length matrices over four directions (00,450,900,1350) and distances of (d=1,3,5,7,9) pixels). Stepwise multi‐linear regression analysis was utilized to avoid feature redundancy leading to a feature subset feeding a Support Vector Machine (SVM) classifier. SVM‐model evaluation was performed by means of the leave‐one‐out method.

Results:

Maximum classification accuracy (93.5%) in distinguishing healthy from chronic liver disease patients was obtained employing three textural features (Standard Deviation, Sum‐Variance, Contrast) that describe the elastogram's contrast, variability and complexity. Sensitivity and specificity values were 93.3% and 94.0% respectively.

Conclusion:

The proposed classification scheme can provide reproducibility and reliability of liver SWE application in clinical practice. It can also assist the interpretation of SWE measurements which is considered as a difficult task due to absence of guidelines in the literature and to decrease the time/cost of diagnosis and the need for patients to undergo invasive examination.

This research has been co‐financed by the European Union (European Social Fund ESF) and Greek national funds through the Operational Program ’Education and Lifelong Learning’ of the National Strategic Reference Framework (NSRF) Research Funding Program: ARCHIMEDES III. Investing in knowledge society through the European Social Fund.
SU‐E‐U‐03: Noncontact Ultrasound Spectroscopy of Cortical Bone Phantoms: Reproducibility
Authors: Ganezer K , Bulman J , Halcrow P , Neeson I
Published: June 2015

Purpose:

In this study we update our studies presented in a talk in the ultrasound symposium in 2014 on the topic of noncontact ultrasound spectroscopy applied to cortical bone phantoms in which we found we found a high correlation between the BUA parameter and the Bone Mineral densities of the phantoms that was provided a linear regression with a r^₂as high as 0.96. The purpose of our current study was to have two separate ultrasound analyzers one at CSUDH in Carson California and a second analyzer at VN and associates in Elizabethtown, Ontario, Canada, in which the two analyzers only had minor differences in the transducers, pulse generators, and other hardware and software. Our goal was to compare the BUA parameters, speed of sound(SOS), attenuation, and spectra. We also considered changes in speed of sound, and attenuation taken 4 years ago with similar measurements made recently.

Methods:

We used Matlab shell files to compute SOS for 2 different methods, BUA, and attenuation for 15 or 16 phantoms that ranged in BMD from 150–1700 gm/m^3. Linear regressions were calculated for sets of two parameters. Some of the phantoms were scanned using a pixelized grid.

Results:

The two systems behaved similarly. There seemed to be only small changes in SOS with larger changes in BUA, that might be attributed to oxidation and loss of water.

Conclusion:

There was a high degree of reproducibility in most of our measurements
SU‐E‐I‐01: Iterative CBCT Reconstruction with a Feature‐Preserving Penalty
Authors: Lyu Q , Li B , Ma J , Wang J
Published: June 2015

Purpose:

Low‐dose CBCT is desired in various clinical applications. Iterative image reconstruction algorithms have shown advantages in suppressing noise in low‐dose CBCT. However, due to the smoothness constraint enforced during the reconstruction process, edges may be blurred and image features may lose in the reconstructed image. In this work, we proposed a new penalty design to preserve image features in the image reconstructed by iterative algorithms.

Methods:

Low‐dose CBCT is reconstructed by minimizing the penalized weighted least‐squares (PWLS) objective function. Binary Robust Independent Elementary Features (BRIEF) of the image were integrated into the penalty of PWLS. BRIEF is a general purpose point descriptor that can be used to identify important features of an image. In this work, BRIEF distance of two neighboring pixels was used to weigh the smoothing parameter in PWLS. For pixels of large BRIEF distance, weaker smooth constraint will be enforced. Image features will be better preserved through such a design. The performance of the PWLS algorithm with BRIEF penalty was evaluated by a CatPhan 600 phantom.

Results:

The image quality reconstructed by the proposed PWLS‐BRIEF algorithm is superior to that by the conventional PWLS method and the standard FDK method. At matched noise level, edges in PWLS‐BRIEF reconstructed image are better preserved.

Conclusion:

This study demonstrated that the proposed PWLS‐BRIEF algorithm has great potential on preserving image features in low‐dose CBCT.
SU‐E‐I‐02: Characterizing Low‐Contrast Resolution for Non‐Circular CBCT Trajectories
Authors: Davis A , Pearson E , Pan X , Pelizzari C
Published: June 2015

Purpose:

The use of non‐circular scanning trajectories with optimization‐basedreconstruction algorithms can be used in conjunction with non‐planaracquisition geometries for axial field‐of‐view (FOV) extension incone‐beam CT (CBCT). To evaluate the utility of these trajectories,quantitative image quality metrics should be evaluated. Low‐contrastresolution (LCR) and CT number accuracy are significant challenges forCBCT. With unprecedented axial coverage provided by thesetrajectories, measuring such metrics throughout the axial range iscritical. There are currently no phantoms designed to measurelow‐contrast resolution over such an extended volume.

Methods:

The CATPHAN (The Phantom Laboratory, Salem NY) is the current standardfor image quality evaluation. While providing several useful modulesfor different evaluation metrics, each module was designed to beevaluated in a single slice and not for comparison across axialpositions. To characterize the LCR and HU accuracy over an extendedaxial length, we have designed and built a phantom with evaluationmodules at multiple and adjustable axial positions.

Results:

The modules were made from a cast polyurethane resin. Holes rangingfrom 1/8 to 5/8 inch were added at a constant radius from the modulecenter into which rods of two different plastic materials were pressedto provide two nominal levels of contrast (1.0% and 0.5%). Largerholes were bored to accept various RMI plugs with known electrondensities for HU accuracy evaluation. The modules can be inserted intoan acrylic tube long enough to cover the entire axial FOV and theirpositions adjusted to desired evaluation points.

Conclusion:

This phantom allows us to measure the LCR and HU accuracy across theaxial coverage within a single acquisition. These metrics can be usedto characterize the impact different trajectories and reconstructionparameters have on clinically relevant image quality performancemetrics.

Funding was provided in part by Varian Medical Systems and NIH R01 Grants Nos. CA158446, CA182264, EB018102, and EB000225. The contents of this poster are solely the responsibility of the authors and do not necessarily represent the official view of any of the supporting organizations.
SU‐E‐I‐03: Lateral Truncation Artifact Correction for 4DCBCT‐Based Motion Modeling and Dose Assessment
Authors: Dhou S , Cifter F , Myronakis M , Berbeco R , Lewis J , Cai W
Published: June 2015

Purpose:

To allow accurate motion modeling and dose assessment based on 4DCBCT by addressing the limited field of view (FOV) and lateral truncation artifacts in current clinical CBCT systems. Due to the size and geometry of onboard flat panel detects, CBCT often cannot cover the entire thorax of adult patients. We implement method to extend the images generated from 4DCBCT‐based motion models and correct lateral truncation artifacts.

Methods:

The method is based on deforming a reference 4DCT image containing the entire patient anatomy to the (smaller) CBCT image within the higher quality CBCT FOV. Next, the displacement vector field (DVF) derived inside the CBCT FOV is smoothly extrapolated out to the edges of the body. These extrapolated displacement vectors are used to generate a new body contour and HU values outside of the CBCT FOV. This method is applied to time‐varying volumetric images (3D fluoroscopic images) generated from a 4DCBCT‐based motion model at 2 Hz. Six XCAT phantoms are used to test this approach and reconstruction accuracy is investigated.

Results:

The normalized root mean square error between the corrected images generated from the 4DCBCT‐based motion model and the ground truth XCAT phantom at each time point is generally less than 20%. These results are comparable to results from 4DCT‐based motion models. The anatomical structures outside the CBCT FOV can be reconstructed with an error comparable to that inside the FOV. The resulting noise is comparable to that of 4DCT.

Conclusions:

The proposed approach can effectively correct the artifact due to lateral truncation in 4DCBCT‐based motion models. The quality of the resulting images is comparable to images generated from 4DCT‐based motion models. Capturing the body contour and anatomy outside the CBCT FOV makes more reasonable dose calculations possible.
SU‐E‐I‐07: Response Characteristics and Signal Conversion Modeling of KV Flat‐Panel Detector in Cone Beam CT System
Authors: Wang Yu , Cao Ruifen , Pei Xi , Wang Hui , Hu Liqin ,   FDS Team
Published: June 2015

Purpose:

The flat‐panel detector response characteristics are investigated to optimize the scanning parameter considering the image quality and less radiation dose. The signal conversion model is also established to predict the tumor shape and physical thickness changes.

Methods:

With the ELEKTA XVI system, the planar images of 10cm water phantom were obtained under different image acquisition conditions, including tube voltage, electric current, exposure time and frames. The averaged responses of square area in center were analyzed using Origin8.0. The response characteristics for each scanning parameter were depicted by different fitting types. The transmission measured for 10cm water was compared to Monte Carlo simulation. Using the quadratic calibration method, a series of variable‐thickness water phantoms images were acquired to derive the signal conversion model. A 20cm wedge water phantom with 2cm step thickness was used to verify the model. At last, the stability and reproducibility of the model were explored during a four week period.

Results:

The gray values of image center all decreased with the increase of different image acquisition parameter presets. The fitting types adopted were linear fitting, quadratic polynomial fitting, Gauss fitting and logarithmic fitting with the fitting R‐Square 0.992, 0.995, 0.997 and 0.996 respectively. For 10cm water phantom, the transmission measured showed better uniformity than Monte Carlo simulation. The wedge phantom experiment show that the radiological thickness changes prediction error was in the range of (‐4mm, 5mm). The signal conversion model remained consistent over a period of four weeks.

Conclusion:

The flat‐panel response decrease with the increase of different scanning parameters. The preferred scanning parameter combination was 100kV, 10mA, 10ms, 15frames. It is suggested that the signal conversion model could effectively be used for tumor shape change and radiological thickness prediction.

Supported by National Natural Science Foundation of China (81101132, 11305203) and Natural Science Foundation of Anhui Province (11040606Q55, 1308085QH138)
SU‐E‐I‐11: A New Cone‐Beam CT System for Bedside Head Imaging
Authors: Sun H , Zeng W , Xu P , Wang Z , Xing X , Sun M
Published: June 2015

Purpose:

To design and develop a new mobile cone‐beam CT (CBCT) system for head imaging with good soft‐tissue visibility, to be used bedside in ICU and neurosurgery department to monitor treatment and operation outcome in brain patients.

Methods:

The imaging chain consists of a 30cmx25cm amorphous silicon flat panel detector and a pulsed, stationary anode monoblock x‐ray source of 100kVp at a maximal tube current of 10mA. The detector and source are supported on motorized mechanisms to provide detector lateral shift and source angular tilt, enabling a centered digital radiographic imaging mode and half‐fan CBCT, while maximizing the use of the x‐ray field and keep the source to detector distance short. A focused linear anti‐scatter grid is mounted on the detector, and commercial software with scatter and other corrective algorithms is used for data processing and image reconstruction. The gantry rotates around a horizontal axis, and is able to adjust its height for different patient table positions. Cables are routed through a custom protective sleeve over a large bore with an in‐plane twister band, facilitating single 360‐degree rotation without a slip‐ring at a speed up to 5 seconds per rotation. A UPS provides about 10 minutes of operation off the battery when unplugged. The gantry is on locked casters, whose brake is control by two push handles on both sides for easy reposition. The entire system is designed to have a light weight and a compact size for excellent maneuverability.

Results:

System design is complete and main imaging components are tested. Initial results will be presented and discussed later in the presentation.

Conclusion:

A new mobile CBCT system for head imaging is being developed. With its compact size, a large bore, and quality design, it is expected to be a useful imaging tool for bedside uses.

The work is supported by a grant from Chinese Academy of Sciences.
SU‐E‐I‐15: Quantitative Evaluation of Dose Distributions From Axial, Helical and Cone‐Beam CT Imaging by Measurement Using a Two‐Dimensional Diode‐Array Detector
Authors: Chacko M , Aldoohan S , Sonnad J , Ahmad S , Ali I
Published: June 2015

Purpose:

To evaluate quantitatively dose distributions from helical, axial and cone‐beam CT clinical imaging techniques by measurement using a two‐dimensional (2D) diode‐array detector.

Methods:

2D‐dose distributions from selected clinical protocols used for axial, helical and cone‐beam CT imaging were measured using a diode‐array detector (MapCheck2). The MapCheck2 is composed from solid state diode detectors that are arranged in horizontal and vertical lines with a spacing of 10 mm. A GE‐Light‐Speed CT‐simulator was used to acquire axial and helical CT images and a kV on‐board‐imager integrated with a Varian TrueBeam‐STx machine was used to acquire cone‐beam CT (CBCT) images.

Results:

The dose distributions from axial, helical and cone‐beam CT were non‐uniform over the region‐of‐interest with strong spatial and angular dependence. In axial CT, a large dose gradient was measured that decreased from lateral sides to the middle of the phantom due to large superficial dose at the side of the phantom in comparison with larger beam attenuation at the center. The dose decreased at the superior and inferior regions in comparison to the center of the phantom in axial CT. An asymmetry was found between the right‐left or superior‐inferior sides of the phantom which possibly to angular dependence in the dose distributions. The dose level and distribution varied from one imaging technique into another. For the pelvis technique, axial CT deposited a mean dose of 3.67 cGy, helical CT deposited a mean dose of 1.59 cGy, and CBCT deposited a mean dose of 1.62 cGy.

Conclusions:

MapCheck2 provides a robust tool to measure directly 2D‐dose distributions for CT imaging with high spatial resolution detectors in comparison with ionization chamber that provides a single point measurement or an average dose to the phantom. The dose distributions measured with MapCheck2 consider medium heterogeneity and can represent specific patient dose.
SU‐E‐I‐18: Evaluation of a Lung Density CT Standard Reference Material
Authors: Chen‐Mayer H , Avila R , John L , Levine Z , Yankelevitz D
Published: June 2015

Purpose:

To evaluate quantitative lung density CT using a Standard Reference Material (SRM) with SI traceable physical densities in a clinical setting free from physiological noise.

Methods:

The 5‐density (0.06 to 0.23 g/cc) suite of polyurethane foams developed as a CT lung density reference (SRM‐2088) was measured inside an anthropomorphic chest phantom in a 64‐row scanner, to assess the mean HU value and its distribution. Two tube current settings (200 mA and 50 mA) were used to represent high‐ and low‐dose CT clinically, with back‐to‐back repeat scans, and for each scan the image reconstruction was performed at slice thicknesses of 0.625 mm and 1.25 mm. A volume histogram was generated for the entire suite, and was fitted to a function with 5 Gaussian peaks, each reporting a centroid (mean HU) and standard deviation (SD in HU) as a measure of the accuracy and precision of the measurement. Statistical analysis was performed using the two levels of mA and recon slice thickness as factors to study the effect on the centroid and the SD.

Results:

Neither dose nor thickness has significant effect on the centroid, but both have significant effect on the SD. At 200 mA, the observed average SD is about half of that at 50 mA. With the thickness doubled, the SD decreased by a factor of 1.17, providing a parameter relating spatial resolution and noise. The SD is more than 3 times higher when compared to the SRM in‐air measurement (without the attenuation and scattering from the chest wall) performed earlier, whereas for the centroid excellent agreement was observed.

Conclusion:

The study provides the underlying uncertainty assessment for these standard references in the lung density range in a set of scanning conditions, forming the basis for estimating the sensitivity to changes in lung density in a clinical setting.

Dr. David Yankelevitz receives royalty payments from General Electric Company.
SU‐E‐I‐84: Accuracy Comparison of Multi‐Modality Image‐Based Volumes of Rodent Solid Tumors Using In‐Air Micro‐CT Image Volume
Authors: Lee Y , Fullerton G , Goins B
Published: June 2015

Purpose:

Tumor volume is considered as a better predictor for therapy response monitoring and tumor staging over Response Evaluation Criteria In Solid Tumors (RECIST) or World Health Organization (WHO) criteria. In this study, the accuracy of subcutaneous rodent tumor volumes using preclinical magnetic resonance imaging (MRI), micro‐computed tomography (micro‐CT) and ultrasound (US) equipment and with an external caliper was compared using in‐air micro‐CT image volume of excised tumors determined as reference tumor volume in our prior study.

Methods:

MR, US and micro‐CT images of subcutaneous SCC4 head and neck tumor xenografts were acquired 4, 6, 9, 11 and 13 days after tumor cell inoculation. Before MR and US scans, caliper measurements were made. After tumors were excised, in‐air micro‐CT imaging and ex vivo caliper measurements were performed. Tumor volumes were calculated using formula V = (π/6)*a*b*c where a, b and c are the maximum diameters in three perpendicular dimensions determined by the three image modalities and caliper, and compared with reference tumor volume by linear regression analysis as well as Bland‐Altman plots. A one‐way Analysis of Variance (ANOVA) test was also performed to compare volumes among caliper measurements.

Results:

The correlation coefficients (R2) of the regression lines for tumor volumes measured by the three imaging modalities and caliper were 0.9939, 0.9669, 0.9806, 0.9274, 0.9619 and 0.9819 for MRI, US and micro‐CT, caliperbeforeMRI, caliperbeforeUS and ex vivo caliper respectively. In Bland‐Altman plots, the average of tumor volume difference from reference tumor volume (bias) was significant for caliper and micro‐ CT, but not for MRI and US. Comparison of caliper measurements showed a significant difference (p < 0.05).

Conclusion:

Using the in‐air micro‐CT image volume, tumor volume measured by MRI was the most accurate among the three imaging modalities. In vivo caliper volume measurements showed unreliability while ex vivo caliper measurements reduced errors.
SU‐E‐I‐89: The Role of Reflectance Confocal Microscopy in the Screening of Hypo‐Pigmented Mycosis Fungoides
Authors: Gao M , Liu H , Fan T
Published: June 2015

Purpose:

Hypopigmented mycosis fungoides (HMF) is a rare variant of cutaneous T‐cell lymphoma(CTCL), and the diagnosis of HMF is often missed due to its low incidence and lack of clinical suspicion. Thus, the misdiagnosis and failure to obtain biopsies lead to a long latency period from onset of hypopigmented patches to diagnosis and treatment. In this study,we aimed to establish a new evaluation system of psoriasis by imaging the ultrastructures of the lesions with reflectance confocal microscopy(RCM).

Methods:

We used the RCM to screen the hypopigmented lesions, and those lesions were biopsied and analyzed if there was some specific findings in the RCM images. In 2014,we performed RCM imaging of 150 cases with hypopigmented lesions and 15 cases of which were confirmed with histological analysis.

Results:

Based on the RCM findings,there was no significant melanin and melanocytes changes in the hypopigmented — to‐achromic lesions, or sometimes even with a vitiligo‐like aspect, compared with the peri‐lesional normal skin, and mononuclear inflammatory cells in the epidermis and upper dermis is the most valuable clue for the suspicious of MF. Then the histology analysis confirmed the diagnosis of HMF. Those 15 cases suspicious of MF under RCM image were all diagnosed as MF by histological analysis.

Conclusions:

The RCM findings correlated well with the histology results in the screening of HMF, which provides an important tool in the evaluation of HMF.
SU‐E‐I‐90: Characterizing Small Animal Lung Properties Using Speckle Observed with An In‐Line X‐Ray Phase Contrast Benchtop System
Authors: Garson A , Gunsten S , Guan H , Vasireddi S , Brody S , Anastasio M
Published: June 2015

Purpose:

We demonstrate a novel X‐ray phase‐contrast (XPC) method for lung imaging representing a paradigm shift in the way small animal functional imaging is performed. In our method, information regarding airway microstructure that is encoded within speckle texture of a single XPC radiograph is decoded to produce 2D parametric images that will spatially resolve changes in lung properties such as microstructure sizes and air volumes. Such information cannot be derived from conventional lung radiography or any other 2D imaging modality. By computing these images at different points within a breathing cycle, dynamic functional imaging will be readily achieved without the need for tomography. Methods: XPC mouse lung radiographs acquired in situ with an in‐line X‐ray phase contrast benchtop system. The lung air volume is varied and controlled with a small animal ventilator. XPC radiographs will be acquired for various lung air volume levels representing different phases of the respiratory cycle. Similar data will be acquired of microsphere‐based lung phantoms containing hollow glass spheres with known distributions of diameters. Image texture analysis is applied to the data to investigate relationships between texture characteristics and airspace/microsphere physical properties.

Results:

Correlations between Fourier‐based texture descriptors (FBTDs) and regional lung air volume indicate that the texture features in 2D radiographs reveal information on 3D properties of the lungs. For example, we find for a 350 × 350 πm2 lung ROI a linear relationship between injected air volume and FBTD value with slope and intercept of 8.9×105 and 7.5, respectively.

Conclusion:

We demonstrate specific image texture measures related to lung speckle features are correlated with physical characteristics of refracting elements (i.e. lung air spaces). Furthermore, we present results indicating the feasibility of implementing the technique with a simple imaging system design, short exposures, and low dose which provides potential for widespread use in laboratory settings for in vivo studies.

This research was supported in part by NSF Award CBET1263988.
SU‐E‐J‐06: Additional Imaging Guidance Dose to Patient Organs Resulting From X‐Ray Tubes Used in CyberKnife Image Guidance System
Authors: Sullivan A , Ding G
Published: June 2015

Purpose:

The use of image‐guided radiation therapy (IGRT) has become increasingly common, but the additional radiation exposure resulting from repeated image guidance procedures raises concerns. Although there are many studies reporting imaging dose from different image guidance devices, imaging dose for the CyberKnife Robotic Radiosurgery System is not available. This study provides estimated organ doses resulting from image guidance procedures on the CyberKnife system.

Methods:

Commercially available Monte Carlo software, PCXMC, was used to calculate average organ doses resulting from x‐ray tubes used in the CyberKnife system. There are seven imaging protocols with kVp ranging from 60 – 120 kV and 15 mAs for treatment sites in the Cranium, Head and Neck, Thorax, and Abdomen. The output of each image protocol was measured at treatment isocenter. For each site and protocol, Adult body sizes ranging from anorexic to extremely obese were simulated since organ dose depends on patient size. Doses for all organs within the imaging field‐of‐view of each site were calculated for a single image acquisition from both of the orthogonal x‐ray tubes.

Results:

Average organ doses were <1.0 mGy for every treatment site and imaging protocol. For a given organ, dose increases as kV increases or body size decreases. Higher doses are typically reported for skeletal components, such as the skull, ribs, or clavicles, than for softtissue organs. Typical organ doses due to a single exposure are estimated as 0.23 mGy to the brain, 0.29 mGy to the heart, 0.08 mGy to the kidneys, etc., depending on the imaging protocol and site.

Conclusion:

The organ doses vary with treatment site, imaging protocol and patient size. Although the organ dose from a single image acquisition resulting from two orthogonal beams is generally insignificant, the sum of repeated image acquisitions (>100) could reach 10–20 cGy for a typical treatment fraction.
SU‐E‐J‐08: Comparison of Unintended Radiation Doses to Organs at Risk Resulting From the Out‐Of‐Field Therapeutic Beams and From Image‐Guidance X‐Ray Procedures
Authors: Ding G , Wang L
Published: June 2015

Purpose:

The unintended radiation dose to organs at risk (OAR) can be contributed from imaging guidance procedures as well as from leakage and scatter of therapeutic beams. This study compares the imaging dose with the unintended out‐of‐field therapeutic dose to patient sensitive organs.

Methods:

The Monte Carlo EGSnrc user codes, BEAMnrc and DOSXYZnrc, were used to simulate kV X‐ray sources from imaging devices as well as the therapeutic IMRT/VMAT beams and to calculate doses to target and OARs on patient treatment planning CT images. The accuracy of the Monte Carlo simulations was benchmarked against measurements in phantoms. The dose‐volume histogram was utilized in analyzing the patient organ doses.

Results:

The dose resulting from Standard Head kV‐CBCT scans to bone and soft tissues ranges from 0.7 to 1.1 cGy and from 0.03 to 0.3 cGy, respectively. The dose resulting from Thorax scans on the chest to bone and soft tissues ranges from 1.1 to 1.8 cGy and from 0.3 to 0.6 cGy, respectively. The dose resulting from Pelvis scans on the abdomen to bone and soft tissues range from 3.2 to 4.2 cGy and from 1.2 to 2.2 cGy, respectively. The out‐of‐field doses to OAR are sensitive to the distance between the treated target and the OAR. For a typical Head‐and‐Neck IMRT/VMAT treatment the out‐of‐field doses to eyes are 1–3% of the target dose, or 2–6 cGy per fraction.

Conclusion:

The imaging doses to OAR are predictable based on the imaging protocols used when OARs are within the imaged volume and can be estimated and accounted for by using tabulated values. The unintended out‐of‐field doses are proportional to the target dose, strongly depend on the distance between the treated target and OAR, and are generally higher comparing to the imaging dose.

This work was partially supported by Varian research grant VUMC40590.
SU‐E‐J‐15: Automatically Detect Patient Treatment Position and Orientation in KV Portal Images
Authors: Qiu J , Yang D
Published: June 2015

Purpose:

In the course of radiation therapy, the complex information processing workflow will Result in potential errors, such as incorrect or inaccurate patient setups. With automatic image check and patient identification, such errors could be effectively reduced. For this purpose, we developed a simple and rapid image processing method, to automatically detect the patient position and orientation in 2D portal images, so to allow automatic check of positions and orientations for patient daily RT treatments.

Methods:

Based on the principle of portal image formation, a set of whole body DRR images were reconstructed from multiple whole body CT volume datasets, and fused together to be used as the matching template. To identify the patient setup position and orientation shown in a 2D portal image, the 2D portal image was preprocessed (contrast enhancement, down‐sampling and couch table detection), then matched to the template image so to identify the laterality (left or right), position, orientation and treatment site.

Results:

Five day's clinical qualified portal images were gathered randomly, then were processed by the automatic detection and matching method without any additional information. The detection results were visually checked by physicists. 182 images were correct detection in a total of 200kV portal images. The correct rate was 91%.

Conclusion:

The proposed method can detect patient setup and orientation quickly and automatically. It only requires the image intensity information in KV portal images. This method can be useful in the framework of Electronic Chart Check (ECCK) to reduce the potential errors in workflow of radiation therapy and so to improve patient safety. In addition, the auto‐detection results, as the patient treatment site position and patient orientation, could be useful to guide the sequential image processing procedures, e.g. verification of patient daily setup accuracy.

This work was partially supported by research grant from Varian Medical System.
SU‐E‐J‐16: Automatic Image Contrast Enhancement Based On Automatic Parameter Optimization for Radiation Therapy Setup Verification
Authors: Qiu J , Li H. Harlod , Zhang T , Ma F , Yang D
Published: June 2015

Purpose:

In RT patient setup 2D images, tissues often cannot be seen well due to the lack of image contrast. Contrast enhancement features provided by image reviewing software, e.g. Mosaiq and ARIA, require manual selection of the image processing filters and parameters thus inefficient and cannot be automated. In this work, we developed a novel method to automatically enhance the 2D RT image contrast to allow automatic verification of patient daily setups as a prerequisite step of automatic patient safety assurance.

Methods:

The new method is based on contrast limited adaptive histogram equalization (CLAHE) and high‐pass filtering algorithms. The most important innovation is to automatically select the optimal parameters by optimizing the image contrast. The image processing procedure includes the following steps: 1) background and noise removal, 2) hi‐pass filtering by subtracting the Gaussian smoothed Result, and 3) histogram equalization using CLAHE algorithm. Three parameters were determined through an iterative optimization which was based on the interior‐point constrained optimization algorithm: the Gaussian smoothing weighting factor, the CLAHE algorithm block size and clip limiting parameters. The goal of the optimization is to maximize the entropy of the processed Result.

Results:

A total 42 RT images were processed. The results were visually evaluated by RT physicians and physicists. About 48% of the images processed by the new method were ranked as excellent. In comparison, only 29% and 18% of the images processed by the basic CLAHE algorithm and by the basic window level adjustment process, were ranked as excellent.

Conclusion:

This new image contrast enhancement method is robust and automatic, and is able to significantly outperform the basic CLAHE algorithm and the manual window‐level adjustment process that are currently used in clinical 2D image review software tools.
SU‐E‐J‐21: Setup Variability of Colorectal Cancer Patients Treated in the Prone Position and Dosimetric Comparison with the Supine Position
Authors: Kim A , Foster J , Chu W , Karotki A
Published: June 2015

Purpose:

Many cancer centers treat colorectal patients in the prone position on a belly board to minimize dose to the small bowel. That may potentially Result in patient setup instability with corresponding impact on dose delivery accuracy for highly conformal techniques such as IMRT/VMAT. Two aims of this work are 1) to investigate setup accuracy of rectum patients treated in the prone position on a belly board using CBCT and 2) to evaluate dosimetric impact on bladder and small bowel of treating rectum patients in supine vs. prone position.

Methods:

For the setup accuracy study, 10 patients were selected. Weekly CBCTs were acquired and matched to bone. The CBCT‐determined shifts were recorded. For the dosimetric study, 7 prone‐setup patients and 7 supine‐setup patients were randomly selected from our clinical database. Various clinically relevant dose volume histogram values were recorded for the small bowel and bladder.

Results:

The CBCT‐determined rotational shifts had a wide variation. For the dataset acquired at the time of this writing, the ranges of rotational setup errors for pitch, roll, and yaw were [−3.6° 4.7°], [−4.3° 3.2°], and [−1.4° 1.4°]. For the dosimetric study: the small bowel V(45Gy) and mean dose for the prone position was 5.6±12.1% and 18.4±6.2Gy (ranges indicate standard deviations); for the supine position the corresponding dose values were 12.9±15.8% and 24.7±8.8Gy. For the bladder, the V(30Gy) and mean dose for prone position were 68.7±12.7% and 38.4±3.3Gy; for supine position these dose values were 77.1±13.7% and 40.7±3.1Gy.

Conclusion:

There is evidence of significant rotational instability in the prone position. The OAR dosimetry study indicates that there are some patients that may still benefit from the prone position, though many patients can be safely treated supine.
SU‐E‐J‐22: A Feasibility Study On KV‐Based Whole Breast Radiation Patient Setup
Authors: Huang Q , Zhang M , Yue N , Chen T
Published: June 2015

Purpose:

In room kilovoltage x‐ray (kV) imaging provides higher contrast than Megavoltage (MV) imaging with faster acquisition time compared with on‐board cone‐beam computed tomography (CBCT), thus improving patient setup accuracy and efficiency. In this study we evaluated the clinical feasibility of utilizing kV imaging for whole breast radiation patient setup.

Methods:

For six breast cancer patients with whole breast treatment plans using two opposed tangential fields, MV‐based patient setup was conducted by aligning patient markers with in room lasers and MV portal images. Beam‐eye viewed kV images were acquired using Varian OBI system after the set up process. In house software was developed to transfer MLC blocks information overlaying onto kV images to demonstrate the field shape for verification. KV‐based patient digital shift was derived by performing rigid registration between kV image and the digitally reconstructed radiography (DRR) to align the bony structure. This digital shift between kV‐based and MV‐based setup was defined as setup deviation.

Results:

Six sets of kV images were acquired for breast patients. The mean setup deviation was 2.3mm, 2.2mm and 1.8mm for anterior‐posterior, superior‐inferior and left‐right direction respectively. The average setup deviation magnitude was 4.3±1.7mm for six patients. Patient with large breast had a larger setup deviation (4.4–6.2mm). There was no strong correlation between MV‐based shift and setup deviation.

Conclusion:

A preliminary clinical workflow for kV‐based whole breast radiation setup was established and tested. We observed setup deviation of the magnitude below than 5mm. With the benefit of providing higher contrast and MLC block overlaid on the images for treatment field verification, it is feasible to use kV imaging for breast patient setup.
SU‐E‐J‐28: Gantry Speed Significantly Affects Image Quality and Imaging Dose for 4D Cone‐Beam Computed Tomography On the Varian Edge Platform
Authors: Santoso A , Song K , Gardner S , Chetty I , Wen N
Published: June 2015

Purpose:

4D‐CBCT facilitates assessment of tumor motion at treatment position. We investigated the effect of gantry speed on 4D‐CBCT image quality and dose using the Varian Edge On‐Board Imager (OBI).

Methods:

A thoracic protocol was designed using a 125 kVp spectrum. Image quality parameters were obtained via 4D acquisition using a Catphan phantom with a gating system. A sinusoidal waveform was executed with a five second period and superior‐inferior motion. 4D‐CBCT scans were sorted into 4 and 10 phases. Image quality metrics included spatial resolution, contrast‐to‐noise ratio (CNR), uniformity index (UI), Hounsfield unit (HU) sensitivity, and RMS error (RMSE) of motion amplitude. Dosimetry was accomplished using Gafchromic XR‐QA2 films within a CIRS Thorax phantom. This was placed on the gating phantom using the same motion waveform.

Results:

High contrast resolution decreased linearly from 5.93 to 4.18 lp/cm, 6.54 to 4.18 lp/cm, and 5.19 to 3.91 lp/cm for averaged, 4 phase, and 10 phase 4DCBCT volumes respectively as gantry speed increased from 1.0 to 6.0 degs/sec. CNRs decreased linearly from 4.80 to 1.82 as the gantry speed increased from 1.0 to 6.0 degs/sec, respectively. No significant variations in UIs, HU sensitivities, or RMSEs were observed with variable gantry speed. Ion chamber measurements compared to film yielded small percent differences in plastic water regions (0.1–9.6%), larger percent differences in lung equivalent regions (7.5–34.8%), and significantly larger percent differences in bone equivalent regions (119.1–137.3%). Ion chamber measurements decreased from 17.29 to 2.89 cGy with increasing gantry speed from 1.0 to 6.0 degs/sec.

Conclusion:

Maintaining technique factors while changing gantry speed changes the number of projections used for reconstruction. Increasing the number of projections by decreasing gantry speed decreases noise, however, dose is increased. The future of 4DCBCT's clinical utility relies on further investigation of image optimization.