bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐P‐31: Quantifying the Amount of Missing Tissue in a Digital Breast Tomosynthesis
Authors: Goodenough D , Olafsdottir H , Olafsson I , Fredriksson J , Mallozzi R , Kristinsson S , Healy A , Oskarsdottir G , Kristbjornsson A , Levy J
Published: June 2015

Purpose:

To automatically quantify the amount of missing tissue in a digital breast tomosynthesis system using four stair‐stepped chest wall missing tissue gauges in the Tomophan™ from the Phantom Laboratory and image processing from Image Owl.

Methods:

The Tomophan™ phantom incorporates four stair‐stepped missing tissue gauges by the chest wall, allowing measurement of missing chest wall in two different locations along the chest wall at two different heights. Each of the four gauges has 12 steps in 0.5 mm increments rising from the chest wall. An image processing algorithm was developed by Image Owl that first finds the two slices containing the steps then finds the signal through the highest step in all four gauges. Using the signal drop at the beginning of each gauge the distance to the end of the image gives the length of the missing tissue gauge in millimeters.

Results:

The Tomophan™ was imaged in digital breast tomosynthesis (DBT) systems from various vendors resulting in 46 cases used for testing. The results showed that on average 1.9 mm of 6 mm of the gauges are visible. A small focus group was asked to count the number of visible steps for each case which resulted in a good agreement between observer counts and computed data.

Conclusion:

First, the results indicate that the amount of missing chest wall can differ between vendors. Secondly it was shown that an automated method to estimate the amount of missing chest wall gauges agreed well with observer assessments. This finding indicates that consistency testing may be simplified using the Tomophan™ phantom and analysis by an automated image processing named Tomo QA. In general the reason for missing chest wall may be due to a function of the beam profile at the chest wall as DBT projects through the angular sampling.

Research supported by Image Owl, Inc., The Phantom Laboratory, Inc. and Raforninn ehf; Mallozzi and Healy employed by The Phantom Laboratory, Inc.; Goodenough is a consultant to The Phantom Laboratory, Inc.; Fredriksson, Kristbjornsson, Olafsson, Oskarsdottir and Olafsdottir are employed by Raforninn, Ehf
SU‐E‐P‐34: Dose Perturbation Caused by Sun Nuclear QED Diode When Used for Very Small Electron Fields
Authors: Klash S , Steinman J , Stanley T
Published: June 2015

Purpose:

Diodes are utilized by radiotherapy departments to help verify that treatment fields are being delivered correctly to the patient. Some treatment fields utilize electron beams along with a cerrobend cutout to shape the beam to the area to be treated. Cerrobend cutouts can sometimes be very small < 2×2‐cm2. Some published work has addressed diode perturbation for cutout sizes down to 1.5‐cm, this work addresses the diode perturbation of the Sun Nuclear QEDTM diode for cutouts as small as 0.5‐cm in diameter.

Methods:

Measurements were taken with an A16 Exradin micro‐chamber in Solid Water to 100‐cm SSD. Dmax was determined for each cutout using various amounts of Solid Water in 1–2 mm increments to account for the dmax shifting in small fields. The diode was placed on top of the solid water to 100‐cm SSD in the center of the cutout. Measurements were taken with no diode for comparison. The cutouts ranged in diameter from 0.5‐cm to 5.0‐cm and included the open 6×6 insert. Measurements were made for energies 6, 9, 12, 15,&18 MeV.

Results:

For 6 MeV, the percent dose reduction from the diode in the cutout field compared to the field without the diode ranged from 35% to 25% as a function of cutout size. For higher energies, this percentage decreased and generally was 25% to 15%. It was observed that dmax shifts significantly upstream for very small cutouts (<2‐cm diameter) to less than 1 cm for all energies.

Conclusion:

The presence of diodes in small electron fields is enough to cause significant dose perturbation to the target volume. It is recommended that diodes for very small electron fields be used sparingly or possibly with a dose correction per treatment fraction(s), if the total projected delivered dose is going to be significantly different from that prescribed by the physician.
SU‐E‐P‐35: Real‐Time Patient Transit Dose Verification of Volumetric Modulated Arc Radiotherapy by a 2D Ionization Chamber Array
Authors: Liu X
Published: June 2015

Purpose:

To explore the real‐time dose verification method in volumetric modulated arc radiotherapy (VMAT) with a 2D array ion chamber array.

Methods:

The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source‐detector distance (SDD)was 140cm. 8mm RW3 solid water was added to the detector panel to achieve maximum readings.The patient plans for esophageal, prostate and liver cancers were selected to deliver on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real‐time patient transit dose measurements were performed at each fraction. Dose distributions wereevaluated using gamma index criteria of 3mm DTA and 3% dose difference referred to the firsttime Result.

Results:

The gamma index pass rate in the Cheese phantom were about 98%; The gamma index pass rate for esophageal, liver and prostate cancer patient were about 92%,94%, and 92%, respectively; Gamma pass rate for all single fraction were more than 90%.

Conclusion:

The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.
SU‐E‐P‐36: Evaluation of MLC Positioning Errors in Dynamic IMRT Treatments by Analyzing Dynalog Files
Authors: Olasolo J , Pellejero S , Gracia M , Gallardo N , Martin M , Lozares S , Maneru F , Bragado L , Miquelez S , Rubio A
Published: June 2015

Purpose:

To assess the accuracy of MLC positioning in Varian linear accelerator, in dynamic IMRT technique, from the analysis of dynalog files generated by the MLC controller.

Methods:

In Clinac accelerators (pre‐TrueBeam technology), control system has an approximately 50ms delay (one control cycle time). Then, the system compares the measured position to the planned position corresponding to the next control cycle. As it has been confirmed by Varian technical support, this effect causes that measured positions appear in dynalogs one cycle out of phase with respect to the planned positions. Around 9000 dynalogs have been analyzed, coming from the three linear accelerators of our center (one Trilogy and two Clinac 21EX) equipped with a Millennium 120 MLC. In order to compare our results to recent publications, leaf positioning errors (RMS and 95th percentile) are calculated with and without delay effect. Dynalogs have been analyzed using a in‐house Matlab software.

Results:

The RMS errors were 0.341, 0.339 and 0.348mm for each Linac; being the average error 0.343 mm. The 95th percentiles of the error were 0.617, 0.607 and 0.625; with an average of 0.617mm. A recent multi‐institution study carried out by Kerns et al. found a mean leaf RMS error of 0.32mm and a 95th percentile error value of 0.64mm.Without delay effect, mean leaf RMS errors obtained were 0.040, 0.042 and 0.038mm for each treatment machine; being the average 0.040mm. The 95th percentile error values obtained were 0.057, 0.058 and 0.054 mm, with an average of 0.056mm.

Conclusion:

Results obtained for the mean leaf RMS error and the mean 95th percentile were consistent with the multi‐institution study. Calculated error statistics with delay effect are significantly larger due to the speed proportional and systematic leaf offset. Consequently it is proposed to correct this effect in dynalogs analysis to determine the MLC performance.
SU‐E‐P‐41: Imaging Coordination of Cone Beam CT, On‐Board Image Conjunction with Optical Image Guidance for SBRT Treatment with Respiratory Motion Management
Authors: Liu Y , Campbell J
Published: June 2015

Purpose:

To spare normal tissue for SBRT lung/liver patients, especially for patients with significant tumor motion, image guided respiratory motion management has been widely implemented in clinical practice. The purpose of this study was to evaluate imaging coordination of cone beam CT, on‐board X‐ray image conjunction with optical image guidance for SBRT treatment with motion management.

Methods:

Currently in our clinic a Varian Novlis Tx was utilized for treating SBRT patients implementing CBCT. A BrainLAB X‐ray ExacTrac imaging system in conjunction with optical guidance was primarily used for SRS patients. CBCT and X‐ray imaging system were independently calibrated with 1.0 mm tolerance. For SBRT lung/liver patients, the magnitude of tumor motion was measured based‐on 4DCT and the measurement was analyzed to determine if patients would be beneficial with respiratory motion management. For patients eligible for motion management, an additional CT with breath holding would be scanned and used as primary planning CT and as reference images for Cone beam CT. During the SBRT treatment, a CBCT with pause and continuing technology would be performed with patients holding breath, which may require 3–4 partially scanned CBCT to combine as a whole CBCT depending on how long patients capable of holding breath. After patients being setup by CBCT images, the ExactTrac X‐ray imaging system was implemented with patients’ on‐board X‐ray images compared to breath holding CT‐based DRR.

Results:

For breath holding patients SBRT treatment, after initially localizing patients with CBCT, we then position patients with ExacTrac X‐ray and optical imaging system. The observed deviations of real‐time optical guided position average at 3.0, 2.5 and 1.5 mm in longitudinal, vertical and lateral respectively based on 35 treatments.

Conclusion:

The respiratory motion management clinical practice improved our physician confidence level to give tighter tumor margin for sparing normal tissue for SBRT lung/liver patients.
SU‐E‐P‐42: Benefit of Equivalent Uniform Dose in Prostate IMRT Planning to Reduce Bladder Toxicity
Authors: Zhu J , Simon A , Haigron P , Lafond C , Acosta O , Shu H , Castelli J , Li B , De Crevoisier R
Published: June 2015

Purpose:

To assess the benefit of bladder wall sub‐volume equivalent uniform dose (EUD) constrains in prostate cancer IMRT planning

Methods:

The bladder wall was defined by the volume between the external manually delineated wall and a contraction of 7 mm from this external wall. This bladder wall was then separated into two parts: the internal‐bladder wall (bla‐in) represented by the portion of the bladder wall that intersected with the planning target volume (PTV) plus 5 mm extension; the external‐bladder wall (bla‐ex) represented by the remaining part of the bladder wall. Two IMRT plans, with and without using EUD constraints, were generated and compared for 53 prostate cancer patients, to deliver 80Gy to the prostate PTV (V95>95%). In the plan with EUD constraints, the values of the “a” parameter of the EUD models were: 10.0 for bla‐in and 2.3 for bla‐ex., and 5 for the rectum.

Results:

The use of bladder EUD objectives increased significantly the conformal index (0.73±0.04 vs. 0.93±0.02) and decreased both the doses in the bladder wall (V70: 22.66% vs. 18.88%, Dmean: 39.40Gy vs. 35.04Gy) and the bladder wall NTCP values (NTCP at 3 years bladder toxicity >= LENT/SOMA Grade2: 16.68% vs. 14.48%, NTCP at 3 years bladder bleeding: 7.16% vs. 5.88%, NTCP at 5 years bladder toxicity >= LENT/SOMA Grade2: 20.15% vs. 17.75%, NTCP at 5 years bladder bleeding: 10.38% vs. 8.36%). The use of bladder EUD objectives, although slightly decreasing the dose to the rectum wall (Dmax: 75.19Gy vs. 75.05Gy, V72: 12.95Gy vs. 12.72Gy) as well, increased however the dose in the femoral heads (V55‐femoral head left: 0.06% vs. 0.30%, V55‐femoral head right: 0.04% vs. 0.21%).

Conclusion:

Separating bladder wall into two parts with appropriate bladder EUD objectives may reduce bladder toxicity, while keeping high dose to the prostate.
SU‐E‐P‐43: A Knowledge Based Approach to Guidelines for Software Safety
Authors: Salomons G , Kelly D
Published: June 2015

Purpose:

In the fall of 2012, a survey was distributed to medical physicists across Canada. The survey asked the respondents to comment on various aspects of software development and use in their clinic. The survey revealed that most centers employ locally produced (in‐house) software of some kind. The respondents also indicated an interest in having software guidelines, but cautioned that the realities of cancer clinics include variations, that preclude a simple solution. Traditional guidelines typically involve periodically repeating a set of prescribed tests with defined tolerance limits. However, applying a similar formula to software is problematic since it assumes that the users have a perfect knowledge of how and when to apply the software and that if the software operates correctly under one set of conditions it will operate correctly under all conditions

Methods:

In the approach presented here the personnel involved with the software are included as an integral part of the system. Activities performed to improve the safety of the software are done with both software and people in mind. A learning oriented approach is taken, following the premise that the best approach to safety is increasing the understanding of those associated with the use or development of the software.

Results:

The software guidance document is organized by areas of knowledge related to use and development of software. The categories include: knowledge of the underlying algorithm and its limitations; knowledge of the operation of the software, such as input values, parameters, error messages, and interpretation of output; and knowledge of the environment for the software including both data and users.

Conclusion:

We propose a new approach to developing guidelines which is based on acquiring knowledge‐rather than performing tests. The ultimate goal is to provide robust software guidelines which will be practical and effective.
SU‐E‐P‐48: Evaluation of Intensity Modulated Radiotherapy (IMRT) with Three Different Commercial Planning Systems for the Treatment of Cervical Cancer
Authors: Liu D , Chi Z , Yang H , Miao M , Jing Z
Published: June 2015

Purpose:

To investigate the performances of three commercial treatment planning systems (TPS) for intensity modulated radiotherapy (IMRT) optimization regarding cervical cancer.

Methods:

For twenty cervical cancer patients, three IMRT plans were retrospectively re‐planned: one with Pinnacle TPS,one with Oncentra TPS and on with Eclipse TPS. The total prescribed dose was 50.4 Gy delivered for PTV and 58.8 Gy for PTVnd by simultaneous integrated boost technique. The treatments were delivered using the Varian 23EX accelerator. All optimization schemes generated clinically acceptable plans. They were evaluated based on target coverage, homogeneity (HI) and conformity (CI). The organs at risk (OARs) were analyzed according to the percent volume under some doses and the maximum doses. The statistical method of the collected data of variance analysis was used to compare the difference among the quality of plans.

Results:

IMRT with Eclipse provided significant better HI, CI and all the parameters of PTV. However, the trend was not extension to the PTVnd, it was still significant better at mean dose, D50% and D98%, but plans with Oncentra showed significant better in the hight dosage volume, such as maximum dose and D2%. For the bladder wall, there were not notable difference among three groups, although Pinnacle and Oncentra systems provided a little lower dose sparing at V50Gy of bladder and rectal wall and V40Gy of bladder wall, respectively. V40Gy of rectal wall (p=0.037), small intestine (p=0.001 for V30Gy, p=0.010 for maximum dose) and V50Gy of right‐femoral head (p=0.019) from Eclipse plans showed significant better than other groups.

Conclusion:

All SIB‐IMRT plans were clinically acceptable which were generated by three commercial TPSs. The plans with Eclipse system showed advantages over the plans with Oncentra and Pinnacle system in the overwhelming majority of the dose coverage for targets and dose sparing of OARs in cervical cancer.
SU‐E‐P‐49: Evaluation of Image Quality and Radiation Dose of Various Unenhanced Head CT Protocols
Authors: Chen L , Khan M , Alapati K , Hsieh M , Barry K
Published: June 2015

Purpose:

To evaluate the diagnostic value of various unenhanced head CT protocols and predicate acceptable radiation dose level for head CT exam.

Methods:

Our retrospective analysis included 3 groups, 20 patients per group, who underwent clinical routine unenhanced adult head CT examination. All exams were performed axially with 120 kVp. Three protocols, 380 mAs without iterative reconstruction and automAs, 340 mAs with iterative reconstruction without automAs, 340 mAs with iterative reconstruction and automAs, were applied on each group patients respectively. The images were reconstructed with H30, J30 for brain window and H60, J70 for bone window. Images acquired with three protocols were randomized and blindly reviewed by three radiologists. A 5 point scale was used to rate each exam The percentage of exam score above 3 and average scores of each protocol were calculated for each reviewer and tissue types.

Results:

For protocols without automAs, the average scores of bone window with iterative reconstruction were higher than those without iterative reconstruction for each reviewer although the radiation dose was 10 percentage lower. 100 percentage exams were scored 3 or higher and the average scores were above 4 for both brain and bone reconstructions. The CTDIvols are 64.4 and 57.8 mGy of 380 and 340 mAs, respectively. With automAs, the radiation dose varied with head size, resulting in 47.5 mGy average CTDIvol between 39.5 and 56.5 mGy. 93 and 98 percentage exams were scored great than 3 for brain and bone windows, respectively. The diagnostic confidence level and image quality of exams with AutomAs were less than those without AutomAs for each reviewer.

Conclusion:

According to these results, the mAs was reduced to 300 with automAs OFF for head CT exam. The radiation dose was 20 percentage lower than the original protocol and the CTDIvol was reduced to 51.2 mGy.
SU‐E‐P‐50: Automated Uniformity Measurements Using a Comprehensive Tomosynthesis QA Phantom
Authors: Olafsdottir H , Goodenough D , Oskarsdottir G , Olafsson I , Fredriksson J , Mallozzi R , Healy A , Kristbjornsson A , Kristinsson S , Levy J
Published: June 2015

Purpose:

The purpose of this study is to look at an automated approach to measure uniformity in DBT using a comprehensive QA phantom versus using a separate uniformity phantom. Our question is whether the uniformity can be reasonably measured within the backdrop of the other test objects?

Methods:

Using the Tomophan ™ from The Phantom Laboratory, both the regional uniformity and the global uniformity was studied. The uniform ROIs are selected carefully to minimize the effect from other test targets.To measure the regional uniformity two large (10mm radius) regions of interest (ROI) are placed in an anterior and lateral position within the phantom image. The locations of the ROIs are shown in figures 1 and 2. Both the mean value and standard deviation of the pixel value within those regions is computed and observed in the slice (z) direction. The results of the global uniformity test indicate how well the imaging system performs in preserving the uniformity within a given slice. The global uniformity looks at the mean value and standard deviation of the pixel value within five ROIs all with a radius of 5 mm placed at various locations within the phantom. The five smaller ROIs indicate how well the imaging device performs in preserving the uniformity within the slice. Because tomosynthesis systems do not use a set pixel value scale, such as the Hounsfield scale in CT, the percentage of the maximum absolute difference between uniformity regions was used for vendor comparison.

Results:

Comparison of 49 cases from six different vendors showed that the uniformity measurements can differ somewhat between scans for the same vendor and between vendors.

Conclusion:

By carefully selecting regions of interest, valuable information can be gained offering information on tomosynthesis image uniformity by using phantom that also contains other targets.

Research supported by Image Owl, Inc., The Phantom Laboratory, Inc. and Raforninn ehf.; Authors Mallozzi and Healy employed by The Phantom Laboratory, Inc.; Author Goodenough is a consultant to The Phantom Laboratory, Inc.; Authors Fredriksson, Kristbjornsson, Olafsson, Oskarsdottir, and Olafsdottir are employeed by Raforninn ehf.
SU‐E‐P‐51: Dosimetric Comparison to Organs at Risk Sparing Using Volumetric‐Modulated Arc Therapy Versus Intensity‐Modulated Radiotherapy in Postoperative Radiotherapy of Left‐Sided Breast Cancer
Authors: Qiao L , Xie J , Cheng J , Liang N , Deng G , Zhang J , Zhang J , Luo H
Published: June 2015

Purpose:

To compare the dosimetric characteristics of volumetric‐modulated arc therapy (VMAT) and intensity‐modulated radiotherapy (IMRT) techniques in treatment planning for left‐sided breast cancer patients with modified radical mastectomy.

Methods:

Twenty‐four left‐sided breast cancer patients treated with modified radical mastectomy were selected in this study. The planning target volume (PTV) was generated by using 7‐mm uniform expansion of the clinical target volume (CTV) in all direction except the skin surface. The organs at risk (OARs) included heart, left lung, right lung, and right breast. Dose volume histograms (DVHs) were utilized to evaluate the dose distribution in PTV and OARs.

Results:

Both VMAT and IMRT plans met the requirement of PTV coverage. VMAT was superior to IMRT in terms of conformity, with a statistically significant difference (p=0.024). Mean doses, V5 and V10 of heart and both lungs in VMAT plans were significantly decreased compared to IMRT plans (P<0.05), but in terms of heart volume irradiated by high doses (V30 and V45), no significant differences were observed (P>0.05). For right breast, VMAT showed the reduction of V5 in comparison with IMRT (P<0.05). Additionally, the mean number of monitor units (MU) and treatment time in VMAT (357.21, 3.62 min) were significantly less than those in IMRT (1132.85, 8.74 min).

Conclusion:

VMAT showed similar PTV coverage and significant advantage in OARs sparing compared with IMRT, especially in terms of decreased volumes irradiated by low doses, while significantly reducing the treatment time and MU number.
SU‐E‐P‐57: Radiation Doses Assessment to Paediatric Patients for Some Digital Diagnostic Radiology Examination in Emergency Department in Qatar
Authors: Abdallah I , Aly A , Al Naemi H
Published: June 2015

Purpose:

The aim of this study was to evaluate radiation doses to pediatric patients undergoing standard radiographic examinations using Direct Digital Radiography (DDR) in Paediatric emergency center of Hamad General Hospital (HGH) in state of Qatar and compared with regional and international Dose Reference Levels (DRLs).

Methods:

Entrance Skin Dose (ESD) was measured for 2739 patients for two common X‐ray examinations namely: Chest AP/PA, Abdomen. Exposure factors such as kV, mAs and Focal to Skin Distance (FSD) were recorded for each patient. Tube Output was measured for a range of selected kV values. ESD for each individual patient was calculated using the tube output and the technical exposure factors for each examination. The ESD values were compared with the some international Dose Reference Levels (DRL) for all types of examinations.

Results:

The most performed procedure during the time of this study was chest PA/PA (85%). The mean ESD values obtained from AP chest, PA chest and AP abdomen ranged 91–120, 80–84 and 209 – 659 µGy per radiograph for different age's groups respectively. Two protocols have been used for chest AP and PA using different radiological parameters, and the different of ESD values for chest PA and were 41% for 1 years old child, 57% for 5 years old for chest AP.

Conclusion:

The mean ESD were compared with those found in literature and were found to be comparable. The radiation dose can be reduced more for Chest AP and PA examination by optimization of each investigation and hence more studies are required for this task. The results presented will serve as a baseline data needed for deriving local reference doses for pediatric X‐ray examinations in this local department and hence it can be applied in the whole Qatar.
SU‐E‐P‐58: Dosimetric Study of Conventional Intensity‐Modulated Radiotherapy and Knowledge‐Based Radiation Therapy for Postoperation of Cervix Cancer
Authors: Ma C , Yin Y
Published: June 2015

Purpose:

To compare the dosimetric difference of the target volume and organs at risk(OARs) between conventional intensity‐modulated radiotherapy(C‐IMRT) and knowledge‐based radiation therapy (KBRT) plans for cervix cancer.

Methods:

39 patients with cervical cancer after surgery were randomly selected, 20 patient plans were used to create the model, the other 19 cases used for comparative evaluation. All plans were designed in Eclipse system. The prescription dose was 30.6Gy, 17 fractions, OARs dose satisfied to the clinical requirement. A paired t test was used to evaluate the differences of dose‐volume histograms (DVH).

Results:

Comparaed to C‐IMRT plan, the KBRT plan target can achieve the similar target dose coverage, D98,D95,D2,HI and CI had no difference (P≥0.05). The dose of rectum, bladder and femoral heads had no significant differences(P≥0.05). The time was used to design treatment plan was significant reduced.

Conclusion:

This study shows that postoperative radiotherapy of cervical KBRT plans can achieve the similar target and OARs dose, but the shorter designing time.
SU‐E‐P‐59: A Graphical Interface for XCAT Phantom Configuration, Generation and Processing
Authors: Myronakis M , Cai W , Dhou S , Cifter F , Hurwitz M , Lewis J
Published: June 2015

Purpose:

To design a comprehensive open‐source, publicly available, graphical user interface (GUI) to facilitate the configuration, generation, processing and use of the 4D Extended Cardiac‐Torso (XCAT) phantom.

Methods:

The XCAT phantom includes over 9000 anatomical objects as well as respiratory, cardiac and tumor motion. It is widely used for research studies in medical imaging and radiotherapy. The phantom generation process involves the configuration of a text script to parameterize the geometry, motion, and composition of the whole body and objects within it, and to generate simulated PET or CT images. To avoid the need for manual editing or script writing, our MATLAB‐based GUI uses slider controls, drop‐down lists, buttons and graphical text input to parameterize and process the phantom.

Results:

Our GUI can be used to: a) generate parameter files; b) generate the voxelized phantom; c) combine the phantom with a lesion; d) display the phantom; e) produce average and maximum intensity images from the phantom output files; f) incorporate irregular patient breathing patterns; and f) generate DICOM files containing phantom images. The GUI provides local help information using tool‐tip strings on the currently selected phantom, minimizing the need for external documentation. The DICOM generation feature is intended to simplify the process of importing the phantom images into radiotherapy treatment planning systems or other clinical software.

Conclusion:

The GUI simplifies and automates the use of the XCAT phantom for imaging‐based research projects in medical imaging or radiotherapy. This has the potential to accelerate research conducted with the XCAT phantom, or to ease the learning curve for new users. This tool does not include the XCAT phantom software itself.

We would like to acknowledge funding from MRA, Varian Medical Systems Inc.
SU‐E‐U‐02: The Development of a Practical Ultrasonic System for Cross‐Sectional Imaging of Small Animals
Authors: Kamp J , Malyarenko E , Chen D , Wydra A , Maev R
Published: June 2015

Purpose:

To test the feasibility of developing a practical medium frequency ultrasound tomography method for small animal imaging. The ability to produce cross‐sectional or full body images of a live small animal using a low‐cost tabletop ultrasound scanner without any special license would be very beneficial to long term biological studies, where repeated scanning is often required over an extended period of time.

Methods:

The cross sectional images were produced by compounding multiple B‐scans of a laboratory phantom or an animal acquired at different projection angles. Two imaging systems were used to test the concept. The first system included a programmable 64‐channel phased array controller driving a 128‐channel, 5–10 MHz linear probe to produce 143 B‐Mode projections of the spinning object. The second system designed and manufactured in house, produced 64 or 128 B‐Mode projections with a single unfocused 8 MHz transducer scanning with a 0.116 mm step size.

Results:

The phased array system provided good penetration through the phantoms/mice (with the exception of the lungs) and allowed to acquire data in a very short time. The cross‐sectional images have enough resolution and dynamic range to detect both high‐ and low‐contrast organs. The single transducer system takes longer to scan, and the data require more sophisticated processing. To date, our images allow seeing details as small as 1–2 mm in the phantoms and in small animals, with the contrast mostly due to highly reflecting bones and air inclusions.

Conclusion:

The work indicates that very detailed and anatomically correct images can be created by relatively simple and inexpensive means. With more advanced algorithms and improved system design, scan time can be reduced considerably, enabling high‐resolution full 3D imaging. This will allow for quick and easy scans that can help monitor tumor growth and/or regression without contributing any dose to the animal.

The authors would like to acknowledge the financial and engineering support from Tessonics.
SU‐E‐I‐04: Improving CT Quality for Radiation Therapy of Patients with High Body Mass Index Using Iterative Reconstruction Algorithms
Authors: Noid G , Tai A , Li X
Published: June 2015

Purpose:

Iterative reconstruction (IR) algorithms are developed to improve CT image quality (IQ) by reducing noise without diminishing spatial resolution or contrast. The CT IQ for patients with a high Body Mass Index (BMI) can suffer from increased noise due to photon starvation. The purpose of this study is to investigate and to quantify the IQ enhancement for high BMI patients through the application of IR algorithms.

Methods:

CT raw data collected for 6 radiotherapy (RT) patients with BMI, greater than or equal to 30 were retrospectively analyzed. All CT data were acquired using a CT scanner (Somaton Definition AS Open, Siemens) installed in a linac room (CT‐on‐rails) using standard imaging protocols. The CT data were reconstructed using the Sinogram Affirmed Iterative Reconstruction (SAFIRE) and Filtered Back Projection (FBP) methods. IQ metrics of the obtained CTs were compared and correlated with patient depth and BMI. The patient depth was defined as the largest distance from anterior to posterior along the bilateral symmetry axis.

Results:

IR techniques are demonstrated to preserve contrast and reduce noise in comparison to traditional FBP. Driven by the reduction in noise, the contrast to noise ratio is roughly doubled by adopting the highest SAFIRE strength. A significant correlation was observed between patient depth and IR noise reduction through Pearson's correlation test (R = 0.9429/P = 0.0167). The mean patient depth was 30.4 cm and the average relative noise reduction for the strongest iterative reconstruction was 55%.

Conclusion:

The IR techniques produce a measureable enhancement to CT IQ by reducing the noise. Dramatic noise reduction is evident for the high BMI patients. The improved CT IQ enables more accurate delineation of tumors and organs at risk and more accuarte dose calculations for RT planning and delivery guidance.

Supported by Siemens
SU‐E‐I‐05: A Correction Algorithm for Kilovoltage Cone‐Beam Computed Tomography Dose Calculations in Cervical Cancer Patients
Authors: Zhang J , Zhang W , Lu J
Published: June 2015

Purpose:

To investigate the accuracy and feasibility of dose calculations using kilovoltage cone beam computed tomography in cervical cancer radiotherapy using a correction algorithm.

Methods:

The Hounsfield units (HU) and electron density (HU‐density) curve was obtained for both planning CT (pCT) and kilovoltage cone beam CT (CBCT) using a CIRS‐062 calibration phantom. The pCT and kV‐CBCT images have different HU values, and if the HU‐density curve of CBCT was directly used to calculate dose in CBCT images may have a deviation on dose distribution. It is necessary to normalize the different HU values between pCT and CBCT. A HU correction algorithm was used for CBCT images (cCBCT). Fifteen intensity‐modulated radiation therapy (IMRT) plans of cervical cancer were chosen, and the plans were transferred to the pCT and cCBCT data sets without any changes for dose calculations. Phantom and patient studies were carried out. The dose differences and dose distributions were compared between cCBCT plan and pCT plan.

Results:

The HU number of CBCT was measured by several times, and the maximum change was less than 2%. To compare with pCT, the CBCT and cCBCT has a discrepancy, the dose differences in CBCT and cCBCT images were 2.48%±0.65% (range: 1.3%∼3.8%) and 0.48%±0.21% (range: 0.1%∼0.82%) for phantom study, respectively. For dose calculation in patient images, the dose differences were 2.25%±0.43% (range: 1.4%∼3.4%) and 0.63%±0.35% (range: 0.13%∼0.97%), respectively. And for the dose distributions, the passing rate of cCBCT was higher than the CBCTs.

Conclusion:

The CBCT image for dose calculation is feasible in cervical cancer radiotherapy, and the correction algorithm offers acceptable accuracy. It will become a useful tool for adaptive radiation therapy.
SU‐E‐I‐06: A Dose Calculation Algorithm for KV Diagnostic Imaging Beams by Empirical Modeling
Authors: Chacko M , Aldoohan S , Sonnad J , Ahmad S , Ali I
Published: June 2015

Purpose:

To develop accurate three‐dimensional (3D) empirical dose calculation model for kV diagnostic beams for different radiographic and CT imaging techniques.

Methods:

Dose was modeled using photon attenuation measured using depth dose (DD), scatter radiation of the source and medium, and off‐axis ratio (OAR) profiles. Measurements were performed using single‐diode in water and a diode‐array detector (MapCHECK2) with kV on‐board imagers (OBI) integrated with Varian TrueBeam and Trilogy linacs. The dose parameters were measured for three energies: 80, 100, and 125 kVp with and without bowtie filters using field sizes 1×1–40×40 cm2 and depths 0–20 cm in water tank.

Results:

The measured DD decreased with depth in water because of photon attenuation, while it increased with field size due to increased scatter radiation from medium. DD curves varied with energy and filters where they increased with higher energies and beam hardening from half‐fan and full‐fan bowtie filters. Scatter radiation factors increased with field sizes and higher energies. The OAR was with 3% for beam profiles within the flat dose regions. The heal effect of this kV OBI system was within 6% from the central axis value at different depths. The presence of bowtie filters attenuated measured dose off‐axis by as much as 80% at the edges of large beams. The model dose predictions were verified with measured doses using single point diode and ionization chamber or two‐dimensional diode‐array detectors inserted in solid water phantoms.

Conclusion:

This empirical model enables fast and accurate 3D dose calculation in water within 5% in regions with near charge‐particle equilibrium conditions outside buildup region and penumbra. It considers accurately scatter radiation contribution in water which is superior to air‐kerma or CTDI dose measurements used usually in dose calculation for diagnostic imaging beams. Considering heterogeneity corrections in this model will enable patient specific dose calculation.
SU‐E‐I‐08: Investigation of Deconvolution Methods for Blocker‐Based CBCT Scatter Estimation
Authors: Zhao C , Ouyang L , Wang J , Jin M
Published: June 2015

Purpose:

To investigate whether deconvolution methods can improve the scatter estimation under different blurring and noise conditions for blocker‐based scatter correction methods for cone‐beam X‐ray computed tomography (CBCT).

Methods:

An “ideal” projection image with scatter was first simulated for blocker‐based CBCT data acquisition by assuming no blurring effect and no noise. The ideal image was then convolved with long‐tail point spread functions (PSF) with different widths to mimic the blurring effect from the finite focal spot and detector response. Different levels of noise were also added. Three deconvolution

Methods:

1) inverse filtering; 2) Wiener; and 3) Richardson‐Lucy, were used to recover the scatter signal in the blocked region. The root mean square error (RMSE) of estimated scatter serves as a quantitative measure for the performance of different methods under different blurring and noise conditions.

Results:

Due to the blurring effect, the scatter signal in the blocked region is contaminated by the primary signal in the unblocked region. The direct use of the signal in the blocked region to estimate scatter (“direct method”) leads to large RMSE values, which increase with the increased width of PSF and increased noise. The inverse filtering is very sensitive to noise and practically useless. The Wiener and Richardson‐Lucy deconvolution methods significantly improve scatter estimation compared to the direct method. For a typical medium PSF and medium noise condition, both methods (∼20 RMSE) can achieve 4‐fold improvement over the direct method (∼80 RMSE). The Wiener method deals better with large noise and Richardson‐Lucy works better on wide PSF.

Conclusion:

We investigated several deconvolution methods to recover the scatter signal in the blocked region for blocker‐based scatter correction for CBCT. Our simulation results demonstrate that Wiener and Richardson‐Lucy deconvolution can significantly improve the scatter estimation compared to the direct method.
SU‐E‐I‐10: Investigation On Detectability of a Small Target for Different Slice Direction of a Volumetric Cone Beam CT Image
Authors: Lee C , Han M , Baek J
Published: June 2015

Purpose:

To investigate the detectability of a small target for different slice direction of a volumetric cone beam CT image and its impact on dose reduction.

Methods:

Analytic projection data of a sphere object (1 mm diameter, 0.2/cm attenuation coefficient) were generated and reconstructed by FDK algorithm. In this work, we compared the detectability of the small target from four different backprojection

Methods:

hanning weighted ramp filter with linear interpolation (RECON 1), hanning weighted ramp filter with Fourier interpolation (RECON2), ramp filter with linear interpolation (RECON 3), and ramp filter with Fourier interpolation (RECON4), respectively. For noise simulation, 200 photons per measurement were used, and the noise only data were reconstructed using FDK algorithm. For each reconstructed volume, axial and coronal slice were extracted and detection‐SNR was calculated using channelized Hotelling observer (CHO) with dense difference‐of‐Gaussian (D‐DOG) channels.

Results:

Detection‐SNR of coronal images varies for different backprojection methods, while axial images have a similar detection‐SNR. Detection‐SNR2 ratios of coronal and axial images in RECON1 and RECON2 are 1.33 and 1.15, implying that the coronal image has a better detectability than axial image. In other words, using coronal slices for the small target detection can reduce the patient dose about 33% and 15% compared to using axial slices in RECON 1 and RECON 2.

Conclusion:

In this work, we investigated slice direction dependent detectability of a volumetric cone beam CT image. RECON 1 and RECON 2 produced the highest detection‐SNR, with better detectability in coronal slices. These results indicate that it is more beneficial to use coronal slice to improve detectability of a small target in a volumetric cone beam CT image.

This research was supported by the MSIP (Ministry of Science, ICT and Future Planning), Korea, under the IT Consilience Creative Program (NIPA‐2014‐H0201‐14‐1002) supervised by the NIPA (National IT Industry Promotion Agency). Authors declares that s/he has no conflict of Interest in relation to the work in this abstract.
SU‐E‐I‐14: Avoiding a Common Pitfall in Performing MTF Measurements with High Resolution Kernels
Authors: Rubert N , Szczykutowicz T , Ranallo F
Published: June 2015

Purpose:

The modulation transfer function (MTF) is frequently used to assess high contrast spatial resolution for routine quality assurance in CT imaging. High resolution reconstruction kernels provide new challenges for MTF estimation. The purpose of this work is to demonstrate the effect of CT number saturation on MTF estimation.

Methods:

A small bead contained in a CATPHAN 600 phantom was imaged at two different slice thicknesses, 2.5 mm and 5.0 mm, on a GE CT 750 HD scanner using an HD Bone Plus reconstruction algorithm in a high resolution scan mode. The resulting images were 2‐D point spread functions (PSF's), which were integrated to create line spread functions, and Fourier transformed to yield MTF's.

Results:

Using a high resolution reconstruction algorithm and the 2.5 mm slice thickness, it was found that the CT number for several pixels in the PSF reached 3071, the maximum value allowed for this system. Using the same algorithm with the 5.0 mm slice, no pixel values reached the CT number limit. Comparing the two MTF's it was found that the MTF affected by CT number saturation had a 10% cut‐off that was shifted downwards, from 15.6 lp/cm to 14.9 lp/cm. Additionally, the MTF affected by CT number saturation exhibited a spurious lobe beyond the true limiting resolution of the CT scanner.

Conclusion:

The downwards shift in MTF cut‐off is a subtle but important effect to consider when attempting to measure MTF for routine quality assurance. While a downwards shift in MTF cut‐off is not easily identified, CT number saturation is readily identified in by examining the entire MTF curve and identifying the spurious lobe produced. CT number saturation is an important consideration when examining test objects to be used for MTF estimation when the algorithm being used is high resolution.

This work was supported by the AAPM grant for Diagnostic Imaging Residencies
SU‐E‐I‐17: Evaluation of Commercially Available Extension Plates for the ACR CT Accreditation Phantom
Authors: Greene‐Donnelly K , Ogden K
Published: June 2015

Purpose:

To evaluate the impact of commercially available extension plates on Hounsfield Unit (HU) values in the ACR CT accreditation phantom (Model 464, Gammex Inc., Middleton, Wi). The extension plates are intended to improve water HU values in scanners where the traditional solution involves scanning the phantom with an adjacent water or CTDI phantom.

Methods:

The Model 464 phantom was scanned on 9 different CT scanners at 8 separate sites representing 16 and 64 slice MDCT technology from four CT manufacturers. The phantom was scanned with and without the extension plates (Gammex 464 EXTPLT‐KIT) in helical and axial modes. A water phantom was also scanned to verify water HU calibration. Technique was 120 kV tube potential, 350 mAs, and 210 mm display field of view. Slice thickness and reconstruction algorithm were based on site clinical protocols. The widest available beam collimation was used. Regions of interest were drawn on the HU test objects in Module 1 of the phantom and mean values recorded.

Results:

For all axial mode scans, water HU values were within limits with or without the extension plates. For two scanners (both Lightspeed VCT, GE Medical Systems, Waukesha WI), axial mode bone HU values were above the specified range both with and without the extension plates though they were closer to the specified range with the plates installed. In helical scan mode, two scanners (both GE Lightspeed VCT) had water HU values above the specified range without the plates installed. With the plates installed, the water HU values were within range for all scanners in all scan modes.

Conclusion:

Using the plates, the Lightspeed VCT scanners passed the water HU test when scanning in helical mode. The benefit of the extension plates was evident in helical mode scanning with GE scanners using a nominal 4 cm beam.

Disclosure: The extension plates evaluated in this work were provided free of charge to the authors. The authors have no other financial interest in Gammex Inc.
SU‐E‐I‐23: A General KV Constrained Optimization of CNR for CT Abdominal Imaging
Authors: Weir V , Zhang J
Published: June 2015

Purpose:

While Tube current modulation has been well accepted for CT dose reduction, kV adjusting in clinical settings is still at its early stage. This is mainly due to the limited kV options of most current CT scanners. kV adjusting can potentially reduce radiation dose and optimize image quality. This study is to optimize CT abdomen imaging acquisition based on the assumption of a continuous kV, with the goal to provide the best contrast to noise ratio (CNR).

Methods:

For a given dose (CTDIvol) level, the CNRs at different kV and pitches were measured with an ACR GAMMEX phantom. The phantom was scanned in a Siemens Sensation 64 scanner and a GE VCT 64 scanner. A constrained mathematical optimization was used to find the kV which led to the highest CNR for the anatomy and pitch setting. Parametric equations were obtained from polynomial fitting of plots of kVs vs CNRs. A suitable constraint region for optimization was chosen. Subsequent optimization yielded a peak CNR at a particular kV for different collimations and pitch setting.

Results:

The constrained mathematical optimization approach yields kV of 114.83 and 113.46, with CNRs of 1.27 and 1.11 at the pitch of 1.2 and 1.4, respectively, for the Siemens Sensation 64 scanner with the collimation of 32 × 0.625mm. An optimized kV of 134.25 and 1.51 CNR is obtained for a GE VCT 64 slice scanner with a collimation of 32 × 0.625mm and a pitch of 0.969. At 0.516 pitch and 32 × 0.625 mm an optimized kV of 133.75 and a CNR of 1.14 was found for the GE VCT 64 slice scanner.

Conclusion:

CNR in CT image acquisition can be further optimized with a continuous kV option instead of current discrete or fixed kV settings. A continuous kV option is a key for individualized CT protocols.