bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐E‐10: Statistical Process Control for VMAT Pre‐Treatment Verification QA Using ArcCHECK and Mobius3D
Authors: Alani S , Schlocker A , Honig N
Published: June 2015

Purpose:

Process capability indices (PCI) are intended to provide single number assessment of ability to meet specification limits on quality characteristics of interest. It can be deduced from the multiple literature citations that PCI are both an effective and excellent means of measuring quality and performance, and have been widely used in the manufacturing industry. This work applied PCI to establish the control limits of the gamma analysis pass rate percentage for patient specific volumetric modulated arc therapy (VMAT) quality assurance (QA), and to evaluate the efficiency of the QA process by using the process capability performance measurement index (Cpm).

Methods:

335 QA plans were measured and evaluated with Mobius3D, a software designed to be an independent treatment plan evaluation tool, and ArcCHECK, a hardware/software product designed for measurement‐based patient‐specific plan QA analysis. The Γ‐(3%/3mm) criteria were used to evaluate the QA plans.

Results:

A statistical analysis of the Γ‐(3%/3mm) passing rates was performed. The Cpm calculated to evaluate QA the capabilities and suitability of the Mobius3D and ArcCHECK QA.The Cpm values of Mobius3D QA was 1.73 and ArcCHECK QA was 1.82 The average Γ‐(3%/3mm)pass was 96.2 +/−2.9 % for ArcCHECK and 95.3 +/−2.1 % for Mobius3D.

Conclusion:

Statistical process controls are useful to quantifiably demonstrate the QA process conformance to specifications. Systematic errors were greater with the ArcCHECK QA process than with the Mobius3D QA process. We speculate that this is due to the physical effort/manual intervention required to setup the ArcCHECK phantom for the measurements.Both the Mobius3D and ArcCHECK QA processes have proven to be acceptable because the values are higher than 1.0
SU‐E‐P‐01: Adaptation of Commercial, Web‐Based, Medical Residency Management Software (MedHub, Inc.) for a Medium‐Sized Medical Physics Residency Program
Authors: Medin P , Pompos A , Britton L , Foster R
Published: June 2015

Purpose:

Management of a CAMPEP‐accredited medical physics residency program (CaMPRP) is demanding. In our experience, the time required to manage a CaMPRP increased linearly with the number of residents. Managing our paper‐based CaMPRP became unwieldy and inefficient when we increased in size from three to four residents resulting in the purchase of commercial, web‐based residency management software (MedHub, Inc).

Methods:

All documentation for our CaMPRP was converted into a format that fits the MedHub structure including: all assessments, procedure participation, mentor/resident meeting summaries, director/resident meeting summaries, journals, tumor board and departmental meeting attendance, written reports, presentations, resident/faculty/staff evaluations, didactic coursework approval, licenses, absence tracking, and ethics/professionalism coursework. The conversion process was performed over a 4‐month period and required approximately 120 hours of director time and 100 hours of administrator time. Task assignments and documentation required of residents and faculty are now scheduled and dispersed through MedHub via email. Regular reminders are automatically emailed from MedHub for incomplete documentation. The MedHub server is maintained centrally by a university‐wide system administrator. Data is encrypted and meets FERPA and HIPAA standards.

Results:

MedHub is a repository for all documentation required of a CaMPRP and is viewable from supported internet browsers. Resident progress and compliance is transparent and viewable in real‐time by residents and administration. Resident and faculty compliance with required documentation and attendance have increased dramatically, approaching 100%. Management of our CaMPRP is now consistent with the medical residency programs who use Medhub campus‐wide. Anonymity is preserved for evaluations of personnel. Lost paper documentation is no longer a concern. Data mining tools are being created to analyze documentation to help increase focus and productivity.

Conclusion:

Medical residency management software has been successfully adapted by a CaMPRP. This management tool has been very useful toward increasing compliance, access, transparency, anonymity and productivity.
SU‐E‐P‐20: Personnel Lead Apparel Integrity Inspection: Where We Are and What We Need?
Authors: Smith S , Zhang J , Anaskevich L , Oates E
Published: June 2015

Purpose:

In recent years, tremendous efforts have been devoted to radiation dose reduction, especially for patients who are directly exposed to primary radiation or receive radiopharmaceuticals. Limited efforts have been focused on those personnel who are exposed to secondary radiation while fulfilling their work responsibilities associated with diagnostic imaging and image‐guided interventions. Occupational exposure is compounded in daily practice and can lead to a significant radiation dose over time. Personnel lead apparel is a well‐accepted engineering control to protect healthcare workers when radiation is inevitable. The question is, do we have a nationally established program to protect personnel? This study is to investigate the lead apparel inspection programs among the USA.

Methods:

A series of surveys of state regulations, the University Health System Consortium, and federal regulations and regulations determined by accrediting bodies were conducted. The surveys were used to determine the current status of lead apparel programs regarding integrity inspections. Based on the survey results, a thorough program was proposed accordingly.

Results:

Of 50 states, seventeen states and Washington D.C. require lead apparel integrity inspections within their state regulations. Eleven of these states specify that the inspection is required on an annual basis. Two of these states require lead apron integrity checks to be performed semi‐annually. Eleven out of the two hundred academic medical centers surveyed responded. The results show that the method (visually vs. fluoroscopy) used to conduct lead apparel integrity checks differ greatly amongst healthcare organizations. The FDA, EPA, CRCPD and NCRP require lead apparel integrity checks. However, the level of policies is different. A standard program is not well established and clearly there is a lack of standardization.

Conclusion:

A program led by legislative (state or federal government) and with specific frequency, methods, tracking and criteria is needed to ensure the integrity of personnel lead apparel.
SU‐E‐P‐21: Impact of MLC Position Errors On Simultaneous Integrated Boost Intensity‐Modulated Radiotherapy for Nasopharyngeal Carcinoma
Authors: Chengqiang L , Yin Y , Chen L
Published: June 2015

Purpose:

To investigate the impact of MLC position errors on simultaneous integrated boost intensity‐modulated radiotherapy (SIB‐IMRT) for patients with nasopharyngeal carcinoma.

Methods:

To compare the dosimetric differences between the simulated plans and the clinical plans, ten patients with locally advanced NPC treated with SIB‐IMRT were enrolled in this study. All plans were calculated with an inverse planning system (Pinnacle3, Philips Medical System₎. Random errors −2mm to 2mm₎,shift errors₍ 2mm,1mm and 0.5mm) and systematic extension/ contraction errors (±2mm, ±1mm and ±0.5mm) of the MLC leaf position were introduced respectively into the original plans to create the simulated plans. Dosimetry factors were compared between the original and the simulated plans.

Results:

The dosimetric impact of the random and system shift errors of MLC position was insignificant within 2mm, the maximum changes in D95% of PGTV,PTV1,PTV2 were‐0.92±0.51%,1.00±0.24% and 0.62±0.17%, the maximum changes in the D0.1cc of spinal cord and brainstem were 1.90±2.80% and −1.78±1.42%, the maximum changes in the Dmean of parotids were1.36±1.23% and −2.25±2.04%.However,the impact of MLC extension or contraction errors was found significant. For 2mm leaf extension errors, the average changes in D95% of PGTV,PTV1,PTV2 were 4.31±0.67%,4.29±0.65% and 4.79±0.82%, the averaged value of the D0.1cc to spinal cord and brainstem were increased by 7.39±5.25% and 6.32±2.28%,the averaged value of the mean dose to left and right parotid were increased by 12.75±2.02%,13.39±2.17% respectively.

Conclusion:

The dosimetric effect was insignificant for random MLC leaf position errors up to 2mm. There was a high sensitivity to dose distribution for MLC extension or contraction errors.We should pay attention to the anatomic changes in target organs and anatomical structures during the course,individual radiotherapy was recommended to ensure adaptive doses.
SU‐E‐P‐23: What Can the Medical Physics Field Learn From the Open Source Hardware Community?
Authors: Wootton L , Therriault‐Proulx F , Beddar S
Published: June 2015

Purpose:

To introduce the Medical Physics community to the up‐and‐coming open hardware movement, and discuss what lessons can be learned from it and how it could be useful to our field.

Methods:

By definition, open source hardware is “hardware whose design is made publicly available so that anyone can study, modify, distribute, make, and sell the design or hardware based on that design”. Arduino microcontroller boards and the evolution in 3d printing technologies are among the most successful open hardware examples. These examples showed that both collaboration and competition are factors facilitating and accelerating innovations. They also help universalizing research by decreasing costs and enabling higher‐level manufacturing. Participation in open source projects in academia has also shown to have multiple advantages. The project gets massively peer reviewed through its online publication, and the comments generally lead to improvement of the design and better performance. It also increases the visibility of the work, therefore increasing the chance for citations and funding.

Results:

The development in‐house of a motorized detector positioning device that can be mounted to a water tank will be open‐sourced and presented as an example of open source project that could be useful to others in the Medical Physics field, whether it is for research or clinical work. The common aspects to share when open‐sourcing a project will be discussed. A device for regulating the temperature inside a water phantom will also be presented and open‐sourced to the community. Finally, the development of a project‐sharing web platform specially designed for the Medical Physics community will be discussed.

Conclusion:

The open source hardware movement is gaining in popularity and the Medical Physics field could benefit from a similar collaborative open‐framework. It would definitely help driving and accelerating innovations in the field as well as decreasing some of the associated costs.

Part of this research was supported by the Odyssey Program at The University of Texas MD Anderson Cancer Center.
SU‐E‐P‐27: Efficient Process for AccuBoost Planning and Treatment Delivery to Minimize Patient Compression Time
Authors: Iftimia I , Talmadge M , Halvorsen P
Published: June 2015

Purpose:

To implement an efficient and robust process for AccuBoost planning and treatment delivery that can be safely performed by a single Physicist while minimizing patient's total session time.

Methods:

Following a thorough commissioning and validation process, templates were created in the brachytherapy planning system for each AccuBoost applicator. Tables of individual and total nominal dwell times for each applicator as a function of separation were generated to streamline planning while an Excel‐based nomogram provided by the vendor functions as a secondary verification of the treatment parameters. Tables of surface dose as a function of separation and applicator, along with concise guidance documents for applicator selection, are readily available during the planning process. The entire process is described in a set of detailed Standard Operating Procedures which, in addition to the items described above, include a verbal time‐out between the primary planner and the individual performing the secondary verification as well as direct visual confirmation of applicator placement using an articulated mirror. Prior to treatment initiation, a final time‐out is conducted with the Radiation Oncologist. Chart documentation is finalized after the patient is released from compression following completion of the treatment.

Results:

With the aforementioned procedures, it has been possible to consistently limit the time required to prepare each treatment such that the patient is typically under compression for less than 10 minutes per orientation prior to the initiation of the treatment, which is particularly important for APBI cases. This process can be overseen by a single physicist assisted by a dosimetrist and has been optimized during the past 16 months, with 180 treatment sessions safely completed to date.

Conclusion:

This work demonstrates the implementation of an efficient and robust process for real‐time‐planned AccuBoost treatments that effectively minimizes the time that the patient is under compression.
SU‐E‐P‐28: Mammography System Collimation Assessment Using Unfors/RaySafe DXR+: How to Increase the Measurement Accuracy
Authors: Wang W , Erdi Y
Published: June 2015

Purpose:

Unfors DXR rulers (Hopkinton, MA) are used to measure the X‐ray field to light field coincidence for mammography systems with a small SID of approximately 66cm. However, due to its bulky size (14.5mm thick with 2.5mm sensors) thickness correction is needed.

Methods:

Unfors DXR rulers were used to evaluate the collimation of three mammography systems: GE Essential, GE 2000D, and Hologic Selenia with various compression paddles. When measuring the X‐ray field to light‐field coincidence using DXR rulers, the light‐field is aligned to the zero mark on top of the ruler which is 14.5mm from the base of the ruler, while the X‐ray sensor inside the ruler is at 7mm from the base of the ruler. Error occurs because of this 7.5mm difference. To resolve this problem, the error is projected to different reference planes for GE and Hologic mammography systems and the correction factors (CFs) are generated. In order to generate the CFs, the image size at the image receptor is measured/calculated for GE and Hologic mammography systems with various compression paddles using the images stored in PACS. For the shifting compression paddle, the movement is also measured at the image receptor plane and CFs are generated based on the X‐ray field locations.

Results:

The generated CFs were used to calculate the X‐ray field to light field coincidence. The CFs ranges from 1.0mm for Hologic Selenia with 18×24cm compression paddle to 2.9mm for GE Essential with 24×30.7cm compression paddle.

Conclusion:

CFs were generated for 3 mammography systems with various compression paddles when measuring the X‐ray field to light field coincidence using Unfors DXR rulers. The application of these correction factors adjusts the X‐ray field to light field misalignment calculation up to 0.55% of the SID which is over a quarter of the 2% SID pass/fail criteria for mammography systems.
SU‐E‐P‐33: Critical Role of T2‐Weighted Imaging Combined with Diffusion‐Weighted Imaging of MRI in Diagnosis of Loco‐Regional Recurrent Esophageal Cancer After Radical Surgery
Authors: Deng G , Liang N , Xie J , Zhang J , Qiao L , Luo H , Zhang J
Published: June 2015

Purpose:

We perform this study to investigate the diagnostic efficacy of T2‐weighted MRI (T2WI) and diffusion‐weighted MRI (DWI) in confirming local relapses of esophageal cancer in patients highly suspected of recurrence after eradicating surgery.

Methods:

Forty‐two postoperative esophageal cancer patients with clinical suspicions of cancer recurrence underwent 3.0T MRI applying axial, coronal, sagittal T2WI and axial DWI sequences. Two experienced radiologists (R1 and R2) both used two methods (T2WI, T2WI+DWI) to observe the images, and graded the patients ranging from 1 to 5 to represent severity of the disease based on visual signal intensity (patients equal to or more than grade 3 was confirmed as recurrent disease)

Results:

27/42patients were verified of recurrent disease by pathologic findings and/or imaging findings during follow‐up. The sensitivity, specificity and accuracy of R1 applying T2WI+DWI are 96%, 87% and 93% versus 81%, 80% and 77% on T2WI, these figures by R2 were 96%, 93% and 95% versus 89%, 93% and 90%. The receiver operating curve (ROC) analyses suggest that both of the two readers can obtain better accuracy when adding DWI to T2WI compared with T2WI alone. Kappa test between R1 and R2 indicates excellent inter‐observer agreement on T2WI+DWI.

Conclusion:

Standard T2WI in combination DWI can achieve better accuracy than T2WI alone in diagnosing local recurrence of esophageal cancer, and improve consistency between different readers.
SU‐E‐P‐46: Clinical Acceptance Testing and Implementation of a Portable CT Unit
Authors: LaFrance M , Marsh S , Hicks R , O'Donnell‐Moran G
Published: June 2015

Purpose:

Planning for the first installation in New England of a new portable CT unit to be used in the Operating Room required the integration of many departments including Surgery, Neurosurgery, Information Services, Clinical Engineering, Radiology and Medical Physics/Radiation Safety. Acceptance testing and the quality assurance procedures were designed to optimize image quality and patient and personnel radiation exposure.

Methods:

The vendor's protocols were tested using the CT Dosimetry phantoms. The system displayed the CTDIw instead of the CTDIvol while testing the unit. Radiation exposure was compared to existing CT scanners from installed CT units throughout the facility. Brainlab measures all 4 periphery slots on the CT Dosimetry phantom. The ACR measures only the superior slot for the periphery measurement. A comprehensive radiation survey was also performed for several locations.

Results:

The CTDIvol measurements were comparable for the following studies: brain, C‐Spine, and sinuses. However, the mobile CT measurements were slightly higher than other CT units but within acceptable tolerance if measured using the ACR method.Based on scatter measurements, it was determined if any personnel were to stay in the OR Suite during image acquisition that the appropriate lead apron and thyroid shields had to be worn.In addition, to reduce unnecessary scatter, there were two mobile 6 foot wide shields (1/16″ lead equivalent) available to protect personnel in the room and adjacent areas.

Conclusion:

Intraoperative CT provides the physician new opportunities for evaluation of the progression of surgical resections and device placement at the cost of increasing the amount of trained personnel required to perform this procedure. It also brings with it challenges to keep the radiation exposure to the patients and staff within reasonable limits.
SU‐E‐P‐53: A Plan Quality Comparison for Volumetric‐Modulated Arc Therapy by Different Maximum Delivery Time Setting for Cervical and Upper Thoracic Esophageal Cancer
Authors: Yang J , Liu D , Miao M , Jing Z , Li Z
Published: June 2015

Purpose:

To evaluate and compare the treatment plan quality of volumetric modulated arc therapy (VMAT) plans using different constrain conditions of delivery time for cervical and upper thoracic esophageal cancer.

Methods:

In this retrospective study, single‐arc VMAT plans were generated with the Oncentra 4.3v system for twenty cervical and upper thoracic esophageal cancer cases. The maximum delivery time were set systematically various as 80s, 110s and 150s. Planning objectives were to deliver 60 Gy in 30 fractions to 95% of PTV, with maximum doses of spinal cord <45 Gy, V5Gy<50%, V10Gy<40%, V20Gy<25% and V30Gy<20% to the lung tissue. All of the three groups of VMAT plans were clinical acceptable. For plan evaluation statistics, PTVDmax, PTVDmin, PTVDmean, PTVD100∼D2, PTVV110∼V90, CordDmax, CordD2, CORDD40, LungDmean, LungV5∼V40 were analyzed and compared by SPSS 20.0.

Results:

The dose distribution quality of plans generated by different maximum delivery time settings was assessed by anova and non‐parametric tests. No significant differences were found for target and OAR parameters except for the hight dose volume of PTV. The maximum dose (p = 0.034) and D2% (p = 0.030) of PTV in plans with 80s setting were detected significant lower than other plans by anova analysis. And for the maximum dose (p = 0.039) of PTV, it was showed the same results by non‐parametric tests.

Conclusion:

Considering of the quality of VMAT plans and the treatment time, 80s as the initial parameters of the maximum delivery time would be a better choice than 110s and 150s for cervical and upper esophageal cancer.
SU‐E‐I‐20: Comprehensive Quality Assurance Test of Second Generation Toshiba Aquilion Large Bore CT Simulator Based On AAPM TG‐66 Recommendations
Authors: Zhang D
Published: June 2015

Purpose:

AAPM radiation therapy committee task group No. 66 (TG‐66) published a report which described a general approach to CT simulator QA. The report outlines the testing procedures and specifications for the evaluation of patient dose, radiation safety, electromechanical components, and image quality for a CT simulator. The purpose of this study is to thoroughly evaluate the performance of a second generation Toshiba Aquilion Large Bore CT simulator with 90 cm bore size (Toshiba, Nasu, JP) based on the TG‐66 criteria. The testing procedures and results from this study provide baselines for a routine QA program.

Methods:

Different measurements and analysis were performed including CTDIvol measurements, alignment and orientation of gantry lasers, orientation of the tabletop with respect to the imaging plane, table movement and indexing accuracy, Scanogram location accuracy, high contrast spatial resolution, low contrast resolution, field uniformity, CT number accuracy, mA linearity and mA reproducibility using a number of different phantoms and measuring devices, such as CTDI phantom, ACR image quality phantom, TG‐66 laser QA phantom, pencil ion chamber (Fluke Victoreen) and electrometer (RTI Solidose 400).

Results:

The CTDI measurements were within 20% of the console displayed values. The alignment and orientation for both gantry laser and tabletop, as well as the table movement and indexing and scanogram location accuracy were within 2mm as specified in TG66. The spatial resolution, low contrast resolution, field uniformity and CT number accuracy were all within ACR's recommended limits. The mA linearity and reproducibility were both well below the TG66 threshold.

Conclusion:

The 90 cm bore size second generation Toshiba Aquilion Large Bore CT simulator that comes with 70 cm true FOV can consistently meet various clinical needs. The results demonstrated that this simulator complies with the TG‐66 protocol in all aspects including electromechanical component, radiation safety component, and image quality component.

Employee of Toshiba America Medical Systems
SU‐E‐I‐86: Ultra‐Low Dose Computed Tomography Attenuation Correction for Pediatric PET CT Using Adaptive Statistical Iterative Reconstruction (ASiR™)
Authors: Brady S , Shulkin B
Published: June 2015

Purpose:

To develop ultra‐low dose computed tomography (CT) attenuation correction (CTAC) acquisition protocols for pediatric positron emission tomography CT (PET CT).

Methods:

A GE Discovery 690 PET CT hybrid scanner was used to investigate the change to quantitative PET and CT measurements when operated at ultra‐low doses (10–35 mAs). CT quantitation: noise, low‐contrast resolution, and CT numbers for eleven tissue substitutes were analyzed in‐phantom. CT quantitation was analyzed to a reduction of 90% CTDIvol (0.39/3.64; mGy) radiation dose from baseline. To minimize noise infiltration, 100% adaptive statistical iterative reconstruction (ASiR) was used for CT reconstruction. PET images were reconstructed with the lower‐dose CTAC iterations and analyzed for: maximum body weight standardized uptake value (SUVbw) of various diameter targets (range 8–37 mm), background uniformity, and spatial resolution. Radiation organ dose, as derived from patient exam size specific dose estimate (SSDE), was converted to effective dose using the standard ICRP report 103 method. Effective dose and CTAC noise magnitude were compared for 140 patient examinations (76 post‐ASiR implementation) to determine relative patient population dose reduction and noise control.

Results:

CT numbers were constant to within 10% from the non‐dose reduced CTAC image down to 90% dose reduction. No change in SUVbw, background percent uniformity, or spatial resolution for PET images reconstructed with CTAC protocols reconstructed with ASiR and down to 90% dose reduction. Patient population effective dose analysis demonstrated relative CTAC dose reductions between 62%–86% (3.2/8.3−0.9/6.2; mSv). Noise magnitude in dose‐reduced patient images increased but was not statistically different from pre dose‐reduced patient images. Conclusion: Using ASiR allowed for aggressive reduction in CTAC dose with no change in PET reconstructed images while maintaining sufficient image quality for co‐localization of hybrid CT anatomy and PET radioisotope uptake.
SU‐E‐I‐91: Quantitative Assessment of Early Hepatocellular Carcinoma and Cavernous Hemangioma of Live Using In‐Line Phase‐Contrast X‐Ray Imaging
Authors: Duan J
Published: June 2015

Purpose:

To investigate the potential utility of in‐line phase‐contrast imaging (ILPCI) technique with synchrotron radiation in detecting early hepatocellular carcinoma and cavernous hemangioma of live using in vitro model system.

Methods:

Without contrast agents, three typical early hepatocellular carcinoma specimens and three typical cavernous hemangioma of live specimens were imaged using ILPCI. To quantitatively discriminate early hepatocellular carcinoma tissues and cavernous hemangioma tissues, the projection images texture feature based on gray level co‐occurrence matrix (GLCM) were extracted. The texture parameters of energy, inertia, entropy, correlation, sum average, sum entropy, difference average, difference entropy and inverse difference moment, were obtained respectively.

Results:

In the ILPCI planar images of early hepatocellular carcinoma specimens, vessel trees were clearly visualized on the micrometer scale. Obvious distortion deformation was presented, and the vessel mostly appeared as a ‘dry stick’. Liver textures appeared not regularly. In the ILPCI planar images of cavernous hemangioma of live specimens, typical vessels had not been found compared with the early hepatocellular carcinoma planar images. The planar images of cavernous hemangioma of live specimens clearly displayed the dilated hepatic sinusoids with the diameter of less than 100 microns, but all of them were overlapped with each other. The texture parameters of energy, inertia, entropy, correlation, sum average, sum entropy, and difference average, showed a statistically significant between the two types specimens image (P<0.01), except the texture parameters of difference entropy and inverse difference moment(P>0.01).

Conclusion:

The results indicate that there are obvious changes in morphological levels including vessel structures and liver textures. The study proves that this imaging technique has a potential value in evaluating early hepatocellular carcinoma and cavernous hemangioma of live.
SU‐E‐J‐01: MR Guided Pulsed Focused Ultrasound Mediated Targeted Chemotherapeutic‐Agent Delivery in Management of Prostate Cancer
Authors: Chen L , Cvetkovic D , Gupta R , Wang B , Ma C
Published: June 2015

Purpose:

The purpose of this study is to investigate an innovative approach to prostate cancer therapy using nanodroplet‐encapsulated drugs combined with pulsed high intensity focused ultrasound (pFUS) treatment. Pulsed FUS treatment improves localized drug release from the carrier and enhances intracellular uptake, which ensures temporal and spatial control of local drug delivery while reducing systemic toxicity from the drugs. Methods: LNCaP cells were implanted into the prostates of nude mice. Tumor growth was monitored using MRI. The tumor—bearing mice were randomly divided into 5 groups (n=5 for each group). Group 1, animals were treated with an IV injection of docetaxel (DTX)‐encapsulated nanodroplets (ND‐DTX) + pFUS. Animals in Group 2 were treated with pFUS alone. Animals in Group 3 were injected (IV) with DTX‐encapsulated nanodroplets alone, Group 4 received free DTX alone and Group 5 was used as a control group. After treatment, animals were allowed to survive for 3 weeks. Tumor growth delay was monitored by MRI (resolution: <0.2mm). The formulation of the DTX‐encapsulated nanodroplets was: DTX dose 20 mg/kg, Nanoemulsion composition 0.5% PTX, 1% perfluorocarbon and 2% stabilizing block copolymer. Ultrasound treatment parameters were 1MHz, 25W acoustic power, 10% duty cycle and 60 sec for each sonication.

Results:

Our results showed that Group 1, in which animals were treated with an IV injection of ND‐DTX + pFUS, exhibited the most tumor growth control (50%–30%) among all groups. All other groups showed similar tumor growth to that of the control group after the treatment (within statistical uncertainties).

Conclusion:

Our preliminary results showed a great potential for prostate cancer therapy using targeted DTX+ nanodroplets, which could be activated by pFUS. Further animal studies are warranted to confirm the results. The enhancement effect of pFUS on targeted drug delivery needs to be investigated quantitatively.
SU‐E‐J‐05: Use of a 6D Couch for Real‐Time Full Translational and Rotational Head Motion Correction During Stereotactic Radiosurgery: A Feasibility Study
Authors: Liu X , Belcher AH , Grelewicz Z , Wiersma RD
Published: June 2015

Purpose:

This work presents a methodology for correcting full translational and rotational head motion deviations during frameless image‐guided stereotactic radiosurgery (SRS) procedures with a robotic 6D couch. The main objective is to design control algorithms which optimize the correction motion of a 6D couch when sub‐millimeter/sub‐degree accuracy requirements are necessary in SRS.

Methods:

The system includes 6D position tracking and a 6D couch with three serially connected platforms. The bottom platform controls yaw compensation (around the z axis), the middle one generates full 3D translational motion, and the top platform controls both pitch (around X) and roll (around Y) motion with two linear actuators. Based on the 6D position of the head and the couch at each moment, the desired 6D couch position for correction is calculated, with the required 6 actuator outputs computed by an inverse algorithm accordingly. To minimize their responsive motion, the actuators take action only after the head position deviates beyond certain predetermined thresholds, and for each action the head is returned to the center of desired 6D treatment position.

Results:

With computer simulation, head motion of an SRS patient was modeled and the simulated couch was used to compensate for this motion in real‐time. For a 15‐minute test with a 0.3 mm and 0.15 degree target position tolerance, the corrected 6D head position was within tolerance over 99.5% of the time. The actuators moved approximately 80 times during the simulation, and the total actuator motion for translational correction was around 205 mm.

Conclusion:

We investigated a control approach for full translational and rotational head motion correction with a 6D couch. The simulations demonstrated that with moderate correction motion of a 6D couch, the control performance meets real‐time submillimeter and sub‐degree accuracy requirement of frameless SRS.

The research is funded by the American Cancer Society (ACS) grant. The grant name is: Frameless SRS Based on Robotic Head Motion Cancellation. The grant number is: RSG‐13‐313‐01‐CCE
SU‐E‐J‐07: IGRT Gently: Evaluating Imaging Dose in Phantoms of Different Sizes
Authors: Morris B , Duggar W , Stanford J , Yang C
Published: June 2015

Purpose:

IGRT imaging procedures have emerged as a common method of patient position verification in radiotherapy, though imaging dose is generally neglected in the treatment plan. Consequently, evaluating and optimizing the dose from these procedures is worthwhile. This process is especially important for children, who are more radiosensitive than adults. The aim of this work was to gain some understanding of the relative doses involved with various XVI‐preset parameters for an “adult” and “child” phantom set, with the hopes that imaging dose for a child can be reduced.

Methods:

32 and 16cm CTDI‐phantoms were used as surrogates for adult and child torsos, respectively. Dose was measured in the central and peripheral chamber positions of the phantoms. CBCT scans were made for both phantoms using Elekta's Chest‐preset to establish a dose baseline. The child‐phantom was then scanned using the Elekta Head and Neck (HN) preset. A modified HN‐preset (named Peds Abd‐pelvis) was also created with a doubled mAs to maintain a reduction in dose to the child‐phantom (relative to the baseline), while providing clinically‐usable image quality.

Results:

The baseline dose to the child‐phantom from the Chest‐preset was 310% that of the adult‐phantom for the center chamber position and 150% at the periphery. An average dose reduction of 97% was obtained in the childphantom by switching from the Chest‐preset to the HN‐preset, while the Peds Abd‐pelvis‐preset similarly reduced the dose by an average of 92%.

Conclusion:

XVI‐preset parameters significantly affect dose, and should be optimized to reduce dose, while ensuring clinically‐usable image quality. Using a modified imaging preset (Peds Abd‐pelvis‐preset) greatly reduced the dose to the child‐phantom compared to the dose for the Chest‐preset for both the child and adult‐phantoms. This outcome provides support for the development of child‐specific protocols for IGRT imaging in pediatric patients.
SU‐E‐J‐09: Image Quality Comparison and Dose Quantification for 2.5 MV
Authors: Stowe M , DiCostanzo D , Ayan A , Woollard J , Gupta N
Published: June 2015

Purpose:

To compare the image quality of the 2.5MV imaging beam (2.5X‐IMB) to that of a 6MV beam and to quantify the imaging dose of a 2.5X‐IMB for constancy as specified by AAPM TG‐142

Methods:

The image quality of the 2.5X‐IMB was compared to the 6MV imaging beam using the SNC ImagePro MV‐QA phantom and the Varian supplied Las Vegas phantom (LVP). High resolution (1280×1280×16, 2 frames at 1.5MU/frame) and low resolution (640×640×16, 2 frames at 0.75MU/frame) images were compared for each phantom. MV‐QA phantom images were evaluated quantitatively, and the LVP images were evaluated qualitatively. The imaging dose for 2.5X‐IMB was quantified using the procedure outlined in TG51. PTWCC13‐31013 chambers were used to measure a percent depth dose (PDD) curve for the 2.5X‐IMB. All the factors described in TG51 were calculated using the 2.5X‐IMB and a PTW30013 farmer chamber.

Results:

A comparison between 2.5X‐IMB and 6MV image quality was performed both visually and with DoseLab software. The optimal window and level were set for each image of the LVP by the user. Visual inspection showed greater contrast resolution with the 2.5MV beam, but no significant difference with the change in imaging resolution. DoseLab reported similar spatial resolutions between the two energies, but the contrast‐to‐noise ratio (CNR) was greater for 2.5MV. The PDDx(10cm) for a 10x10cm2 field was measured to be 51.5%. Although this PDD value is off the scale of Figure 4 in TG51, the trend of the curve corresponding to the PTW31003 (equivalent) chamber led to an approximate kQ value of 1.00.

Conclusion:

When compared to 6MV imaging, 2.5X‐IMB results in a better CNR. At low resolution, the DoseLab results for the two energies are comparable, but visual analysis favors the 2.5X‐IMB images. Imaging dose was quantified for the 2.5X‐IMB after following the TG51 methodology with appropriate approximations.
SU‐E‐J‐11: Measurement of Eye Lens Dose for Varian On‐Board Imaging with Different CBCT Acquisition Techniques
Authors: Deshpande S , Dhote D , Kumar R , Thakur K
Published: June 2015

Purpose:

To measure actual patient eye lens dose for different cone beam computed tomography (CBCT) acquisition protocol of Varian's On Board Imagining (OBI) system using Optically Stimulated Luminescence (OSL) dosimeter and study the eye lens dose with patient geometry and distance of isocenter to the eye lens

Methods:

OSL dosimeter was used to measure eye lens dose of patient. OSL dosimeter was placed on patient forehead center during CBCT image acquisition to measure eye lens dose. For three different cone beam acquisition protocol (standard dose head, low dose head and high quality head) of Varian On‐Board Imaging, eye lens doses were measured. Measured doses were correlated with patient geometry and distance between isocenter to eye lens.

Results:

Measured eye lens dose for standard dose head was in the range of 1.8 mGy to 3.2 mGy, for high quality head protocol dose was in range of 4.5mGy to 9.9 mGy whereas for low dose head was in the range of 0.3mGy to 0.7mGy. Dose to eye lens is depends upon position of isocenter. For posterioraly located tumor eye lens dose is less.

Conclusion:

From measured doses it can be concluded that by proper selection of imagining protocol and frequency of imaging, it is possible to restrict the eye lens dose below the new limit set by ICRP. However, undoubted advantages of imaging system should be counter balanced by careful consideration of imaging protocol especially for very intense imaging sequences for Adoptive Radiotherapy or IMRT
SU‐E‐J‐17: Intra‐Fractional Prostate Movement Correction During Treatment Delivery Period for Prostate Cancer Using the Intra‐Fractional Orthogonal KV‐MV Image Pairs
Authors: Zhang J , Azawi S , Cho‐Lim J , Wei R , Williams R , Frank E
Published: June 2015

Purpose:

To evaluate the intra‐fractional prostate movement range during the beam delivery and implement new IGRT method to correct the prostate movement during the hypofractionated prostate treatment delivery.

Methods:

To evaluate the prostate internal motion range during the beam delivery, 11 conventional treatments were utilized. Two‐arc RapidArc plans were used for the treatment delivery. Orthogonal KV imaging is performed in the middle of the treatment to correct intra‐fractional prostate movement. However, it takes gantry‐mounted on‐board imaging system relative long time to finish the orthogonal KV imaging because of gantry rotation. To avoid gantry movement and accelerate the IGRT processing time, orthogonal KV‐MV image pair is tested using the OBI daily QA Cube phantom.

Results:

The average prostate movement between two orthogonal KV image pairs was 0.38cm (0.20cm ∼ 0.85cm). And the interval time between them was 6.71 min (4.64min ∼ 9.22 min). 2‐arc beam delivery time is within 3 minutes for conventional RapidArc treatment delivery. Hypofractionated treatment or SBRT need 4 partial arc and possible non‐coplanar technology, which need much longer beam delivery time. Therefore prostate movement might be larger. New orthogonal KV‐MV image pair is a new method to correct the prostate movement in the middle of the beam delivery if real time tracking method is not available. Orthogonal KV‐MV image pair doesn't need gantry rotation. Images were acquired quickly which minimized possible new prostate movement. Therefore orthogonal KV‐MV image pair is feasible for IGRT.

Conclusion:

Hypofractionated prostate treatment with less PTV margin always needs longer beam delivery time. Therefore prostate movement correction during the treatment delivery is critical. Orthogonal KV‐MV imaging pair is efficient and accurate to correct the prostate movement during treatment beam delivery. Due to limited fraction number and high dose per fraction, the MV imaging dose is negligible.
SU‐E‐J‐23: Characteristics of X‐Rays From ExacTrac and Patient Dose From Imaging Procedures
Authors: Ding G
Published: June 2015

Purpose:

The purpose of this investigation is 1) provide the beam characteristics of x‐rays produced by a Novalis TX ExacTrac system; 2) present a method to commission such beams, 3) present radiation dose to patients resulting from the imaging procedures.

Methods:

The Monte Carlo simulations were used to obtain the characteristics of kV beams and validated by measurements. The calculated beam HVLs, profiles and depth‐dose curves were benchmarked against measurements. Twelve different image acquisition protocols were studied. The x‐ray tube voltage ranges from 70 ‐ 145 kV and milliampere‐second (mAs) ranges from 8 ‐ 80 mAs depending on the selection of Cranium, Head & Neck, Thorax or Abdomen imaging protocols. The beam output of each image acquisition protocol was determined by using an ionization chamber. The air kerma calibration factors of the ion chamber were obtained from an Accredited Dosimetry Calibration Laboratory for specified HVLs.

Results:

The agreements between measured and simulated results were within the uncertainties for HVLs, dose profiles and depth‐dose curves. When %dd was normalized at 1 cm depth, its values at depth of 5 cm ranged from 45% to 66% of in water for kV beams range from 70 kVp to 145 kVp respectively. For head images, a typical dose to eye resulting from single projection ranged from 0.008 cGy to 0.025 cGy depending on the cranial image protocols selected. For a single pelvic image the skin dose could reach up to 0.1 cGy from an abdominal protocol.

Conclusion:

Although multiple pairs of x‐ray images are commonly acquired during a daily patient treatment, the imaging doses to patients resulting from the sum of these projected x‐rays are generally much less than 0.5 cGy. The knowledge obtained from this investigation can be used to estimate the image dose and optimize the used of the system.
SU‐E‐J‐31: Monitor Interfractional Variation of Tumor Respiratory Motion Using 4D KV Conebeam Computed Tomography for Stereotactic Body Radiation Therapy of Lung Cancer
Authors: Tai A , Prior P , Gore E , Johnstone C , Li X
Published: June 2015

Purpose:

4DCT has been widely used to generate internal tumor volume (ITV) for a lung tumor for treatment planning. However, lung tumors may show different respiratory motion on the treatment day. The purpose of this study is to evaluate 4D KV conebeam computed tomography (CBCT) for monitoring tumor interfractional motion variation between simulation and each fraction of stereotactic body radiation therapy (SBRT) for lung cancer.

Methods:

4D KV CBCT was acquired with the Elekta XVI system. The accuracy of 4D KV CBCT for image‐guided radiation therapy (IGRT) was tested with a dynamic thorax motion phantom (CIRS, Virginia) with a linear amplitude of 2 cm. In addition, an adult anthropomorphic phantom (Alderson, Rando) with optically stimulated luminescence (OSL) dosimeters embedded at the center and periphery of a slab of solid water was used to measure the dose of 4D KV CBCT and to compare it with the dose with 3D KV CBCT. The image registration was performed by aligning\ each phase images of 4D KV CBCT to the planning images and the final couch shifts were calculated as a mean of all these individual shifts along each direction.A workflow was established based on these quality assurance tests for lung cancer patients.

Results:

4D KV CBCT does not increase imaging dose in comparison to 3D KV CBCT. Acquisition of 4D KV CBCT is 4 minutes as compared to 2 minutes for 3D KV CBCT. Most of patients showed a small daily variation of tumor respiratory motion about 2 mm. However, some patients may have more than 5 mm variations of tumor respiratory motion.

Conclusion:

The radiation dose does not increase with 4D KV CBCT. 4D KV CBCT is a useful tool for monitoring interfractional variations of tumor respiratory motion before SBRT of lung cancer patients.
SU‐E‐J‐48: Imaging Origin‐Radiation Isocenter Coincidence for Linac‐Based SRS with Novalis Tx
Authors: Geraghty C , Workie D , Hasson B
Published: June 2015

Purpose

To implement and evaluate an image‐based Winston‐Lutz (WL) test to measure the displacement between ExacTrac imaging origin and radiation isocenter on a Novalis Tx system using RIT V6.2 software analysis tools. Displacement between imaging and radiation isocenters was tracked over time. The method was applied for cone‐based and MLC‐based WL tests.

Methods

The Brainlab Winston‐Lutz phantom was aligned to room lasers. The ExacTrac imaging system was then used to detect the Winston‐ Lutz phantom and obtain the displacement between the center of the phantom and the imaging origin. EPID images of the phantom were obtained at various gantry and couch angles and analyzed with RIT calculating the phantom center to radiation isocenter displacement. The RIT and Exactrac displacements were combined to calculate the displacement between imaging origin and radiation isocenter. Results were tracked over time.

Results

Mean displacements between ExacTrac origin and radiation isocenter were: VRT: −0.1mm ± 0.3mm, LNG: 0.5mm ± 0.2mm, LAT: 0.2mm ± 0.2mm (vector magnitude of 0.7 ± 0.2mm). Radiation isocenter was characterized by the mean of the standard deviations of the WL phantom displacements: σVRT: 0.2mm, σLNG: 0.4mm, σLAT: 0.6mm. The linac couch base was serviced to reduce couch walkout. This reduced σLAT to 0.2mm. These measurements established a new baseline of radiation isocenter‐imaging origin coincidence.

Conclusion

The image‐based WL test has ensured submillimeter localization accuracy using the ExacTrac imaging system. Standard deviations of ExacTrac‐radiation isocenter displacements indicate that average agreement within 0.3mm is possible in each axis. This WL test is a departure from the tradiational WL in that imaging origin/radiation isocenter agreement is the end goal not lasers/radiation isocenter.
SU‐E‐J‐51: The Impact of Off‐Center Position On Image Quality of Megavoltage CT
Authors: Zhang K , Hu ZH , Dai JR
Published: June 2015

Purpose

To quantify the impact of off‐center position on image quality of megavoltage CT in head and neck tumor patient and body tumor patient.

Methods

A Catphan 600 phantom and a Cheese phantom were imaged by TomoHD at the center and off‐center positions stepped by 5cm in AP and LR directions until the phantom edge approaching the imaging edge with fine, normal and coarse scan modes. Both phantoms incorporate image uniformity module, spatial resolution module and CT number linearity module. The CT number linearity module of Cheese phantom was set to simulate Catphan 600 phantom in a larger size. According to AAPM TG‐148 report, noise, image uniformity, spatial resolution and CT number variation were assessed for MVCT image quality. Centers of peripheral ROIs for noise and uniformity were about 4cm from phantom edge.

Results

Noise in all positions was within the criteria except the peripheral regions for Cheese phantom at off‐center scan positions. Image uniformity for most positions was acceptable, and all failed data were from the ROIs near imaging edge area. Spatial resolution degraded with off‐center scanning, and scan mode also made it worse with wider slice thickness, but just 1 level at most. CT number change with and without image uniformity correction for all positions were all less than tolerance, but it was close to the red line for water‐equivalent material.

Conclusion

This work indicates that if depth of lesions is below 4cm and MVCT are used for dose calculations, the ipsilateral body edge should be 5cm within imaging edge. Otherwise, image uniformity should be concerned.