bluuebunny/crossref_metadata_2025 huggingface dataset:
TU‐C‐110‐01: Patient Dose in CT: Calculating Patient Specific Doses in CT(Joint with Education)
Authors: McNitt‐Gray M , Xu X , Samei E
Published: November 2011

In light of recent events involving dose to patients undergoing CT exams, many efforts to record patient dose have been initiated. Many national and international groups (FDA, NIBIB, ACR, IAEA, and NIH intramural programs) have called for recording “dose”, or required that CT equipment report dose. In California, a state law [SB1237] was recently passed that requires (as of July 1, 2012) the reporting of one of the following: “The computed tomography index volume (CTDIvol) and dose length product (DLP), as defined by the International Electrotechnical Commission (IEC) and recognized by the federal Food and Drug Administration (FDA); The dose unit as recommended by the American Association of Physicists in Medicine”.

While these reporting/recording efforts are well‐meaning, the only dose metrics currently available for reporting are CTDIvol and DLP. While CTDIvol values are highly standardized and recognized around the world, they actually are measures of scanner output, and as such they do not reflect the actual patient dose or the irradiation burden of the exam. This misconception of CTDI is commonplace and has led to misinterpretation of the dosimetry values being reported at the scanner and recorded into patient records.

The purpose of this symposium is to describe methods to more accurately estimate the radiation dose to various organs, and ultimately the radiation risk, to patients undergoing CT exams. The symposium covers methods aimed towards more patient‐specific estimates that take into account: (a) scanner related factors (CT manufacturer and model specifics), (b) exam related specifics (anatomic coverage, use of dose reduction methods such as tube current modulation) and (c) patient related factors such as age, gender, size, and shape.

The learning objectives of this symposium include the following:

1. To understand the limitations of current metrics (e.g. CTDIvol) and methods in estimating patient dose

2. To understand the methods to more accurately estimate radiation dose that take into account scanner, exam and patient specific factors

3. To understand the role of Computational Phantoms and Monte Carlo simulation methods in developing patient‐specific organ dose estimates

4. To understand methods to estimate patient‐specific organ doses, effective doses, and radiation risk for comparison and optimization purposes
TU‐C‐211‐01: Automatic Digital Gain Control for a New Dual EMCCD‐Based Modular Fluoroscopic Detector Using An Arbitrary‐Shaped Operator‐Selected Region of Interest
Authors: Qu B , Huang Y , Wang W , Panse A , Cartwright A , Titus A , Bednarek D , Rudin S
Published: November 2011

Purpose: To report on the design and operation of a fluoroscopic automatic gain control (AGC) system with arbitrary‐shaped operator‐selected region of interest (ROI) for a new high resolution detector consisting of an array of two EMCCD‐based modules. Methods: A solid‐state x‐ray imager consisting of dual EMCCD‐based modules was built to provide high resolution (effective pixel size 26.4 um) and wide dynamic range (55dB) in fluoroscopy. A graphic user interface was employed based on LabVIEW to display the 2K × 1K 12‐bit digital images. The image from the second sensor was digitally rotated and shifted so as to maintain image registration with the image from the first sensor. The AGC system consisting of a real‐ time feed‐back loop and a universal asynchronous receiver/transmitter platform was implemented to enable control by comparing the current average digital values in the operator‐selected ROI with a preset desired value resulting in a step by step change of the EMCCD built‐in gains to achieve the desired image brightness. A standard aluminum step wedge was used to demonstrate the response speed and a head phantom was employed to provide a realistic complex structure, rich in contrast variations. Results: The operator‐selected ROI was able to be positioned anywhere in the full 1K × 2K field of view, even with parts in each module. The settling time for smoothly reaching stable brightness was in the range of 10 to 20 frames. A video sequence demonstrates a smooth brightness transition to the desired value when the head phantom is arbitrarily moved across the field of view of the detector. Conclusions: We introduce a new real‐time AGC design for a unique custom‐built high resolution modular array detector. Stable levels of brightness within the ROI were demonstrated. Operators can set up an arbitrary shaped ROI in advance or during the procedure.

Support: NIH Grants R01‐EB008425, R01‐EB002873
TU‐C‐211‐02: Characterizing the Dynamic Range and Noise Performance of a High‐Resolution EMCCD‐Based X‐Ray Detector Having Large Variable Electronic Gain Enabling Use in Both Fluoroscopy and Angiography
Authors: Huang Y , Qu B , Jain A , Wang W , Bednarek D R , Titus A H , Rudin S
Published: November 2011

Purpose: To quantitatively characterize the dynamic range and noise performance of a new custom‐built, 1k by 1k, 26.4 micron square pixel, high‐resolution, solid‐state EMCCD‐based x‐ray detector. Methods: We performed two sets of experiments: higher‐exposure angiographic imaging with lower gain (< 200), and lower‐exposure fluoroscopic imaging with higher gain (> 200). For each experiment, 150 flat‐field images are acquired over the range of exposures for each multiplication gain. Average signal digital number (DN) versus exposure, and average variance (DN) versus exposure or signal are plotted and linearly fitted to quantitatively characterize the electronic gain, background or dark noise equivalent rms electrons, and instrumentation noise equivalent exposure (INEE), respectively. Results: For the low gain measurements, the noise electron rms value and INEE decreases with increasing gain virtually eliminating the effect of read‐noise, which is the main source of noise for conventional detectors. When the gain is increased for the low exposure measurements, dark noise from dark current and clock induced charge (CIC), which are constant with gain, become dominant and set the detection limit. With the same procedure, an additional experiment is performed to evaluate the dark noise and INEE at high gain with cooling. At room temperature, the dark noise is 1.03 e‐ rms and the INEE is 1.46 microR. Cooling the sensor effectively reduces the noise electrons (0.66 e‐ rms at 200mA pelticooler current and 0.50 e‐ rms at 400mA pelticooler current) and INEE (0.52 microR at 200mA pelticooler current and 0.33 microR at 400mA pelticooler current). Conclusions: The EMCCD‐based x‐ray detector with large variable gain has linear performance over a wide range of exposures with a low noise floor that can be further decreased by moderate cooling. The INEE for this unique detector is substantially less than the 2 to 3 microR of conventional flat panels.

Support: NIH Grants R01‐EB008425, R01‐EB002873
TU‐C‐211‐03: Increasing X‐Ray Tube Output for Small Focal Spot, Region‐Of‐Interest Imaging
Authors: Gupta S , Bednarek D , Rudin S
Published: November 2011

Purpose: High‐resolution region‐of‐interest (ROI) imaging requires the use of a small focal spot with sufficient output to maintain spatial and contrast resolution. We investigate methods to increase the x‐ray output while maintaining the focal‐spot size for a small field‐of‐view (FOV) as needed for endovascular‐image‐guided interventions (EIGIs).

Materials and Methods: We evaluated the increase in tube output made possible by reducing the anode angle and lengthening the filament for the small focal spot to maintain a constant effective focal‐spot size. Since the area of heat deposition on the anode is increased, tube‐loading capacity increases and the mA can be increased proportionally if the electron flux density at the target is unchanged. “Spek Calc” software was used to calculate the change in inherent tube filtration and in x‐ray spectrum and intensity as a function of anode angle. The gain in tube output achievable while maintaining focal‐spot size was determined for the small‐FOV of our custom high‐resolution, ROI imager. When the same tube is used for both large‐FOV imager and the small‐FOV ROI imager, angling the tube and adjusting filament length can allow a tradeoff between spatial resolution, tube loading and FOV. Results: For the 5‐cm FOV needed in neurovascular ROI imaging, the x‐ray output could be increased substantially with decreasing anode angle while the focal‐spot size and FOV is maintained. Considering both increased anode‐target area and increased inherent anode filtration, a net output increase of 3.3 times could be achieved with a 2‐ degree anode angle compared to the standard 8‐degree target with an increase of 4 times in filament length. Conclusions: For EIGIs where high resolution is essential but only over a small FOV, higher tube output while maintaining a small focal spot should be achievable with only small modification of standard x‐ray tube geometry.

Support: NIH Grants R01‐EB008425, R01‐EB002873
TU‐C‐211‐04: Time‐Resolved Cone‐Beam CT for Cardiac Interventions
Authors: Lauzier P Theriault , Tang J , Chen G‐H
Published: November 2011

Purpose: To obtain artifact‐free 3D images with high temporal resolution from truncated projection data recorded using a cardiac interventional system with a slowly rotating gantry and a small flat‐panel detector. Methods: In order to reconstruct time‐resolved cardiac images from truncated projections, one must be able to achieve ultra‐high temporal resolution, while also mitigating truncation artifacts. Both of these goals can be achieved using an adapted implementation of the prior image constrained compressed sensing (PICCS) algorithm. To demonstrate this, a canine animal model was scanned in vivo using an interventional C‐arm system with a 40×40 sq cm detector in a single rotation 14‐second acquisition. The projections were artificially truncated to simulate the use of a 20×20 sq cm detector commonly used in many cardiac intervention suites. The projections were gated retrospectively using the recorded ECG signal into 20 cardiac phases. The data from each phase were reconstructed using the PICCS algorithm. The reconstruction accuracy was assessed by evaluating image quality of both truncated and non‐truncated datasets. Results: The images reconstructed from truncated data using the PICCS algorithm resulted in a root mean square deviation of about 2.5% with respect to the non‐truncated data. Furthermore, the truncated PICCS reconstructions did not contain artifacts that plagued the images reconstructed using the FDK algorithm from the same datasets. The temporal resolution achieved in this study was about 33 ms. The PICCS reconstructions were generated in under 2 minutes per phase for a 256×256×128 image volume using a GPU‐based implementation. Note that the reconstruction of each phase can be processed in parallel. Conclusions: Artifact‐free time‐resolved cardiac imaging is achievable using a cardiac intervention C‐arm system with a slowly rotating gantry and the PICCS algorithm. Further optimization could bring the reconstruction time to a level adequate for the interventional setting.

Grant from GE Healthcare (Waukesha, WI)
TU‐C‐211‐07: Fiducial‐Based Registration of Digital Histopathology to Ex Vivo Prostate MRI
Authors: Gibson E , Crukley C , Gomez JA , Moussa M , Chin JL , Bauman G , Fenster A , Ward AD
Published: November 2011

Purpose: An accurate determination of stage and grade from in vivo prostate cancer imaging would support improved biopsy guidance, therapy selection and, possibly, focal therapy guidance. Validation of prostate cancer imaging modalities ideally requires accurate registration of in vivo imaging to histopathology, where accurate diagnoses can be made. An important intermediate component of this registration aligns ex vivo imaging to histology. This work describes and evaluates a simplified approach, developed in our laboratory, to the registration of digital prostate histopathology to ex vivo magnetic resonance (MR) images. Our approach obviates three elements typical of existing methods: (1) guidance of specimen slicing, (2) imaging/photography of sliced tissue blocks, and (3) dependence on the appearance of salient structures within the image to guide registration. Methods: Six resected prostate specimens were marked with strand‐shaped fiducials, imaged with T1‐ and T2‐weighted MRI before and after image‐guided specimen slicing, and then processed for histology as whole mount specimens. Direct fiducial‐based registration from histology to whole specimen ex vivo MRI was performed by establishing a correspondence between fiducial cross‐sections on histology and fiducial space curves on whole specimen MRI. The target registration error (TRE) of 93 intrinsic landmarks across 21 histology images was calculated for this method, for an indirect registration using tissue block MRI and for a registration based on image‐guidance of slicing. Results: The image‐guided, indirect and direct registrations yielded TREs of 1.2 mm, 0.8 mm and 0.8 mm respectively. A two‐tail paired t‐test failed to show a significant difference between direct and indirect registration mean TREs (p = 0.8, 95% confidence interval, −0.08 to 0.10 mm), and showed that both TREs were lower than that of the image‐guided registration (p = 0.0001). Conclusions: The direct registration is a suitable replacement for existing, more complex registration methods for aligning histopathology to ex vivo imaging.
TU‐C‐211‐08: Optimization of a Deformable Registration Algorithm for Matching MRI with Histology for Clinical Prostatectomy
Authors: Samavati N , McGrath D , Lee J , VanderKwast T , Ménard C , Brock K
Published: November 2011

Purpose: Optimize and evaluate a biomechanical model‐based deformable image registration algorithm incorporating specimen‐specific changes in material properties for correlating histology of clinical prostatectomy specimens with invivo MRI. Methods: An in‐house biomechanical model‐ based deformable registration based on finite element modeling was developed for accurate correlative pathology for clinical prostatectomy. Five image sets were acquired for 4 prostatectomy patients: 1) invivo T2 MRI, 2) exvivo fresh (before fixation) T2 MR, 3) exvivo fixed (after fixation), 4) digital photographs of gross slices after sectioning, and 5) digital whole‐ mount histology images of the slices. A 2D landmark based deformable registration technique is used to accurately reconstruct 3D histology volume based on fixed and gross image sets. A 3‐step deformable registration based on biomechanics calculates the transformations between histology and fixed, fixed and fresh, and fresh and invivo. Magnetic Resonance Elastography performed on the exvivo tissue provided a specimen specific element‐based Youngˈs modulus map for the fresh and fixed tissue accounting for changes due to fixation. The accuracy of the algorithm was quantified by identifying naturally occurring fiducials in each image and evaluating the Dice overlap index of contoured regions within the prostate. The accuracy was compared to a rigid registration technique. Results: The average absolute error based on fiducial points in Left‐Right (LR), Anterior‐Posterior (AP), Superior‐ Inferior (SI) directions was 1.3, 1.1, and 1.0 respectively compared to 1.7 (LR), 1.3 (AP), and 1.3 (SI) [mm] achieved with rigid registration. The maximum absolute error was also reduced from 5.4 with rigid to 3.6 mm with deformable registration. A DICE index of 0.67 was achieved using the deformable registration, compared to 0.49 with rigid registration. Conclusions: A biomechanical model‐based deformable registration algorithm which incorporates tissue specific changes in material properties has been developed and evaluated on prostatectomy samples, showing marked improvement over rigid registration.
TU‐C‐211‐09: Quantitative Total Bone Imaging Methodology and Its Sensitivity to Thresholding
Authors: Morrison C , Liu G , Jeraj R
Published: November 2011

Purpose: Prostate cancer is the most prevalent cancer among males in the US, and over 90% of patients develop bone metastases. Current treatment response evaluation metrics, such as RECIST, are not suited for assessing bone lesions. The aim of this work is to present an automated segmentation method that identifies and characterizes bone lesions and determine its sensitivity to thresholding. Methods: Patients with metastatic prostate cancer were treated with molecular target therapy and received whole body [F‐18]NaF (bone imaging) PET/CT scans during the course of treatment. Scans were evaluated using the Quantitative Total Bone Imaging (QTBI) methodology, which assesses total bone and individual bone lesions in patients with bone metastases. Individual lesions were segmented using thresholds ranging from 20% to 80% of the maximum standardized uptake value (SUV) in bone. The mean SUV, total SUV, and volume of the total bone and individual lesions were determined as well as the number of lesions. Treatment response was assessed as the percent change in the imaging metrics relative to pre‐treatment. Results: The QTBI methodology was able to identify and characterize bone lesions. Of the treatment response metrics, change in number of lesions showed the greatest dependence on the threshold. The standard deviation of patient responses ranged from 13.5 to 34.5. Change in mean SUV had the least sensitivity to threshold (SD=0.5–2.0). Change in total SUV and volume both showed intermediate variation (SD=7.5–11.5 and 11.0–12.5, respectively). Conclusions: The QTBI methodology is able to identify and characterize bone lesions. However, because most imaging metric responses vary with different thresholds, careful selection of SUV threshold for segmentation is necessary to accurately identify and characterize bone lesions and assess treatment response. With further refinement, this methodology can be a clinically useful tool to improve patient care and test new therapies for use in metastatic bone disease.
TU‐C‐211‐12: Performance of a Novel Region Growing Segmentation Method for Nuclear Medicine
Authors: McGurk R , Smith T , Das S
Published: November 2011

Purpose: To investigate the performance improvement of a novel region growing (SRG) and “segmentation‐by‐consensus” (SBC) technique for delineation of lesions in FDG‐PET. Further, the improvement in lesion segmentation using time‐of‐flight (TOF) PET was investigated. Methods: The NEMA image quality phantom was filled to give 3:1 and 7:1 contrast ratios between spheres (0.44 – 27.13 cc) and background. Contrast added to the sphere volumes and a hi‐resolution CT allowed segmentation of the true activity distribution. Ten minute list‐mode scans were acquired on a GE Discovery 690 PET/CT system. Images were reconstructed representing 1, 2 and 5 minute acquisitions using TOF and NTF methods. Four commonly used segmentation methods, 40%max 50%max, K‐means, fuzzy C‐means, and the SRG technique, were used to segment the six spheres. The SBC approach creates volumes from voxels segmented by a majority of the techniques. Absolute volume differences and volume overlap were metrics for evaluating each algorithmˈs performance. Results: All techniques performed poorly for the small (0.44 & 1.08 cc) spheres with mean volume errors between 10–30 cc (3:1 contrast), and 5.5–12 cc (7:1). SRG consistently had lower average volume errors (4.25–6.30 cc) but 40%max had the highest absolute volume overlap for the largest sphere (0.7795– 0.8090). However, SRG dramatically outperformed 40%max for the 1.08 cc sphere (0.4338–0.4952 vs. 0.0124–0.0173). For the high (7:1) contrast, k‐ means consistently gave lower average volume errors (0.09–6.95 cc) and higher average volume overlap (0.4741–0.5765) than SRG (8.57–10.15 cc and 0.3543–0.3967). No noticeable difference with TOF was observed. SBC gave results within the above ranges for both 3:1 and 7:1 with less variation and was close to the highest performing technique in each scenario. Conclusions: TOF offers comparable results to NTF PET for the volumes segmented. The SRG technique provided lower mean volume errors and good volume overlap in low contrast situations.
TU‐C‐301‐01: Going Paperless in a Radiation Oncology Clinic
Authors: Jani S
Published: November 2011

There are numerous important advantages of going paperless in a radiotherapy clinic. This process can be challenging in many ways. In this session, we share practical details on how a clinic can go paperless. In the first presentation, I will describe this process with Elekta Mosaiq software. The second presentation covers the process with Varian Aria software.

The MosaiQ software V2.0 supports three radiotherapy departments, two infusion centers and a specialty wound care clinic at Sharp Healthcare system. All the facilities are within 20 miles from each other. Prior to initiating the paperless process, we acquired a crucial software program, Adobe Acrobat 9 Pro with multiple licenses. We also purchased Fujitsu fi‐ 6130 document scanners, another critical component in our success.

The first section to go paperless was the Physics/Dosimetry area. All treatment plans from ADAC Pinnacle and BrainLab BrainScan are converted to PDF files, electronically signed by the planner and stored in MosaiQ under Diagnosis and Interventions. These documents can then be approved by the radiation oncologist and physicist prior to treatment. We also created Word templates in the document section to support billing and special procedures, such as physics consults, special treatment procedure notes, and QA documents.

Making full use of the Quality Check List feature was next. Simulation orders, dosimetry tasks, new patient QA, chart checks, chart rounds and close‐out QA of electronic charts are all performed electronically through MosaiQ. For each of these steps, a Quality Check List (QCL) was created and employed so that no critical procedures go un‐documented.

Billing has been electronic using HL7 interface for many years at Sharp Healthcare.

Finally, the outside reports such as imaging and surgical notes, past H & P, nursing notes, etc, from applications like Cerner, Synapse, are transferred to MosaiQ using the “Print to File” function of Acrobat 9 Pro. Any remaining documents can be scanned and saved as PDF in the patientˈs EMR.

In our experience, the first 5% and last 5% of going paperless took the longest. The process has been painless as well as fun. If there is one factor above all, though, to ensure success, it is having the staff on‐board. Everyone, from the radiation oncologists to the front office personnel, recognizes the value in eliminating paper charts in the department, and has helped to make it happen seamlessly and successfully.

Learning objectives are:

1. understand the benefit of going paperless in radiotherapy clinic

2. understand the steps required and optimal sequence to transition from paper to electronic medical records

3. understand the value of safeguards such as redundancies, double‐ checks, etc that should be placed for safe delivery of radiation
TU‐C‐220‐08: Assessing Intra‐Tumor Hemodynamics and Oxygen Concentration Using Photoacoustic Computed Tomography
Authors: Stantz K , Cao N , Shaffer M , Miller KD
Published: November 2011

Purpose: The goal is to develop a method to non‐invasively assess intra‐tumor pO2 using photoacoustic imaging. It is well established that the oxygen status of a tumor plays a critical role in the therapeutic response and resistance, resulting in treatment failure and poor disease‐free and overall survival. Clinical techniques, such as polarographic electrode, photoluminescence‐quenching, or pimonidazole, are invasive and lack the patho‐physiological etiology leading to hypoxia. A biophysical model is proposed to determine local pO2 based on fusing hemodynamic measurements acquired from dynamic contrast‐enhanced and spectroscopic photoacoustic imaging (DCE‐PCT and PCT‐S). Methods: MCF7 and MCF7/VEGF xenograft breast tumors were first scanned within a prototype PCT scanner to obtain parametric maps of oxygen saturation and hemoglobin concentration and within a clinical CT scanner to obtain dynamic contrast‐enhanced data (DCE‐CT) to obtain parametric maps of perfusion, fractional‐plasma‐volume, and fractional‐interstitial‐volume. These maps were fused based on a mathematical model of tissue oxygen delivery, and compared to measurements taken with an OxyLite probe. To replace DCE‐CT, a new generation of PCT scanner was developed to acquire DCE‐PCT data and realize physiological maps. Mice with MDA‐ MB‐231 xenograft breast tumors were i.v. injected with ICG, and scanned prior to and every 12‐seconds for up to 4‐minutes and at 15‐minutes post‐injection. These contrast‐enhance curves were fit compartmental models to obtain maps of tumor perfusion and fractional plasma volumes. Results: Preliminary results comparing pO2 measurements implementing biophysical models and PCT‐S and DCE‐CT and OxyLite probe measured a linear correlation of R2=0.82, and a slope of 0.975(±0.10) and an intercept of −0.093(±2.2)mmHg. The first parametric maps of tumor perfusion and fractional plasma volume using DCE‐PCT will be presented and compared to DCE‐CT, and ICG kinematics identifying regions of high extravasation. Conclusions: A biophysical model of pO2 based on hemodynamic data and physiological maps in breast tumors obtained from photoacoustic imaging has been demonstrated.
TU‐E(SAM)‐211‐02: Role of the Medical Physicist in Clinical Implementation of Breast Tomosynthesis
Authors: Liu B
Published: November 2011

FDA recently approved Hologic Selenia Dimensions Tomosynthesis system for 3 dimensional breast imaging. Many new systems will be installed in the near future. To properly support the implementation of this new modality, clinical physicists need to understand unique operation conditions of the tomosynthesis system, shielding requirements, factors affecting image quality and patient dose, sources of image artifacts, in addition to knowing the basic principles of tomosynthesis image acquisition and reconstruction.

This talk will focus on the implementation and acceptance test of Hologic Selenia Dimensions tomosynthesis system. The operation modes, typical acquisition parameters, x‐ray beam characteristics, system performance in terms of image quality and patient dose will be described. The impact of unique imaging acquisition parameters on shielding requirements will be discussed. The acceptance tests which are unique to the tomo modes will be illustrated.

Learning objectives:

1. Understand the typical operation modes of Hologic tomo system and image acquisition parameter range.

2. Understand the achievable system performance of Hologic tomo system in terms of image quality and patient dose.

3. Understand the impact of the unique tomo image acquisition parameters on room shielding requirement

4. Understand major factors influencing the image quality and patient dose

5. Know how to perform the acceptance test.
TU‐E‐224‐01: The Role of Voluntary versus Mandatory Regulatory Standards
Authors: Balter S
Published: November 2011

The patientˈs skin and the lens of the eye are the critical tissues for most fluoroscopically guided interventional procedures. Risks include hair loss, skin toxicity, and radiogenic cataracts. Appropriate dosimetric feedback to the operator contributes to optimizing benefit‐risk. Ideally, interventional fluoroscopes should provide real‐time feedback via a continuously updated dose maps and accurate estimates of peak skin dose. Such technology is not generally available in 2011. However, a variety of real‐time and post‐procedure tools are currently available for managing fluoroscopic skin irradiation. Equipment conforming to IEC 60601‐2‐43 (2000, 2010) displays fluoroscopic time, PKA and Ka,r at the operatorˈs working position. All fluoroscopes sold in the USA after mid 2006 displays fluoro‐time and Ka,r. Various film and detector arrays have been used to obtain post‐procedure dose maps for more than a decade.

Newer fluoroscopes and third‐party dose monitoring systems are beginning to offer useful proprietary dose mapping in angular space (defined by gantry angles) in both real‐time and post‐procedure flavors. Initial commercial deliveries of the DICOM Radiation Dose Structured Report (RDSR) provide detailed post‐procedure procedural information in enough detail to facilitate detailed dose reconstruction. Data in the RDSR is in defined public fields to facilitate accessibility. The relevant DICOM and IEC standards include specifications for real‐time streaming of the data. This will facilitate the development of independent real‐time dose modeling. This lecture will review the technologies available in 2011 and will provide an estimate of future time‐lines in this area. It will also include a discussion of the use of complete sets of dosimetric data as part of the quality process.

Learning Objectives:

1. Understand the advantages and disadvantages of currently available dose monitoring technologies.

2. Understand the evolution toward real‐time skin dose mapping.

3. Understand how standardized dosimetry can be incorporated into a QA program.
TU‐E‐224‐02: The Role of Voluntary versus Mandatory Regulatory Standards
Authors: Pizzutiello R
Published: November 2011

Standards are essential to providing practitioners with a uniform set of tools to use to deliver healthcare to the public. Image the limitations imposed in previous generations when radiation dose was “measured” by the “Skin Erythema Dose.” The development and widespread use of the concept of absorbed dose to organs created a new paradigm that opened the door to the modern era of Radiation Medicine.

The current absence of uniform standards for dose display limits our ability to use dosimetry information effectively in the clinical decision support process. The development of Standards has historically evolved from Educational, through Voluntary and ultimately to Regulatory implementation. Our experience with Mammography since the late 1980ˈs provides helpful context. When MQSA was enacted, only 25% of the mammography facilities in the USA were accredited.

Todayˈs Regulatory Standards in the USA start with the familiar FDA Product Standards, and are now supplemented and strengthened by emerging Professional and Reimbursement Standards.

How can AAPM, COMP and other members of the Radiation Medicine community help to create Dose Display standards that are meaningful, practical, and most importantly support the clinical decision making process?
TU‐E‐224‐03: The Role of Voluntary versus Mandatory Regulatory Standards
Authors: Bolch W
Published: November 2011

In its Report No. 160, the National Council on Radiation Protection and Measurement (NCRP) reported that the average value of the effective dose to exposed individuals has increased by a factor of 1.7 over the time period 1982 to 2006, with the contribution of medical exposures correspondingly increasing by a factor of 5.7. At present, medical contributors to the effective dose include computed tomography (50% of total medical exposure), nuclear medicine (25%), interventional fluoroscopy (15%), and conventional radiography and diagnostic fluoroscopy (10%). The assignment of organ doses to patients in has increasingly relied on the use of computational anatomical phantoms. In this presentation, we review the various phantom format types — stylized, voxel, and hybrid — as well as phantom morphometric categories — reference, patient‐dependent, patient‐ sculpted, and patient‐specific. Specific emphasis is given to hybrid phantoms — those defined through the use of combinations of polygon mesh and NURBS surfaces. The concept of a patient‐dependent phantom is reviewed in which phantoms of non‐50th percentile heights and weights are designed from population‐based morphometric databases and provided as a larger library of phantoms for patient matching and lookup of refined organ doses. Specific examples of the use of hybrid phantoms are given for nuclear medicine (MIRD schema), computed tomography, and interventional radiology dose assessment.
TU‐E‐BRA‐02: How Should We Verify Complex Radiation Therapy Treatments ?
Authors: Ibbott G , Oldham M , Mijnheer B , Zhu T
Published: November 2011

The critical importance of comprehensive treatment verification to patient safety is a topic of major current interest. The increase in complexity of modern treatments has created a direct need for correspondingly more sophisticated and comprehensive verification tools. A variety of new dosimetry techniques, QA devices, and verification rationale have recently emerged with potential to transform the process of both commissioning and routine patient treatment verification. A common goal of many of these systems is a more comprehensive measurement of the delivered dose in 3‐dimensions (3D) with high accuracy and spatial resolution. Several of these 3D or semi‐3D systems can also measure delivered dose in moving phantoms, and can therefore address important verification questions in 4D. Other approaches are capable of estimating the in‐vivo dose delivered to patients by back‐projecting measured exit fluence acquired during treatment. This symposium aims to review both the clinical rationale and clinical implementation of these important developments in complex treatment verification. Speakers will address the following topics in the context of clinical verification of advanced treatments like IMRT, VMAT/RapidArc, tomotherapy, and SRS/SBRT etc): 1) EPID dosimetry — both in‐vivo and ex‐vivo, 2) dosimetry with diode and chamber arrays, 3) 3D dosimetry with radiochromic plastics and gels, 4) computational algorithms for independent verification. The characteristics, state‐of‐the‐art, limitations, and clinical experience from these techniques will be reviewed.

Learning objectives:

1. gain insight into the dosimetric challenges posed by advanced radiation treatment techniques

2. appreciate the importance of comprehensive treatment verification to patient safety

3. understand the rationale and capabilities of dosimetry techniques for comprehensive treatment verification, both in‐vivo and ex‐vivo
TU‐E‐BRB‐02: Monte Carlo Optimized Composition and Structure of a Novel Energy‐Independent Radiochromic Film
Authors: Sarfehnia A , Singh K , Devic S , Seuntjens J
Published: November 2011

Purpose: To develop an energy‐independent Gafchromic film through optimization of the film absorbed dose energy response using accurate Monte Carlo modeling. Methods: A prototype radiochromic film (similar in construction to EBT2) was simulated accurately using the DOSRZnrc of EGSnrcMP Monte Carlo user‐code. The composition of the film active layer was changed according to physical limits set by the manufacturer. The dose to film was scored in a 3cm radius region of active layer centered on the central beam axis. The film was simulated inside a large body of solid water for megavoltage beams, while at kilovoltage energies, the film was modeled in air. The simulations were repeated to score the dose to water as well as water kerma in air for megavoltage and kilovoltage beams, respectively. Results: The absorbed dose energy dependence f(Q) was studied in detail for a wide variety of film active layer compositions in a 10keV–100keV energy range as well as at Co‐60. Addition of bromine was found to affect f(Q) in the 40–50keV region, while chlorine significantly affected the lowest energies. We determined that intrinsic (LET‐dependent) energy dependence kbq(Q) also plays an important role on the total energy dependence of Gafchromic films and cannot be ignored. Subsequent measurements unexpectedly showed changes in kbq(Q) as a function of chlorine and bromine content. Intrinsic energy dependence was determined indirectly by measuring the total energy‐dependence of prototype films and taking out the calculated extrinsic portion. This formed the basis for an iterative process for film development. Conclusions: Through numerical optimization of the composition of the active layer of a new prototype radiochromic film, we have thus far been able to compensate for intrinsic energy response of the films and produce a new film with a total response of+2% to −6% in 50kVp to Co‐60 energy range.
TU‐E‐BRB‐03: A Treatment Planning System for Contrast‐Enhanced Stereotactic Synchrotron Radiation Therapy Clinical Trials
Authors: Vautrin M , Prezado Y , Martinez‐Rovira I , Deman P , Edouard M , Elleaume H , Benkebil M , Esteve F , Adam J
Published: November 2011

Purpose: Contrast‐enhanced stereotactic synchrotron radiation therapy (SSRT) is an innovative technique based on localized dose‐enhancement effects obtained by reinforced photoelectric absorption in the target. Medium energy monochromatic x‐rays (50 –100 keV) are used for irradiating tumors previously loaded with high‐Z elements. SSRT clinical trials are being prepared at the European Synchrotron Radiation Facility. The first patients are scheduled in summer‐autumn 2011. They should be treated at 80 keV, with 10 conformational beams. A dedicated treatment planning system (TPS) was developed for this purpose, based on the ISOgray commercial TPS (Dosisoft, Cachan, France).Methods: The PENELOPE‐based Monte Carlo virtual simulation module was adapted to SSRT specificities: simulation of lower energy photons and electrons (100 keV and lower) and polarized photons. The synchrotron beamline geometry was modeled. Dedicated Phase Space Files were built. Additional materials were implemented in the patient voxelized geometry, to model the high‐Z element biodistribution in the tumor. A dedicated computation method for irradiation times (instead of monitor units) was implemented. The simulation process was optimized and parallelized. This dedicated TPS was validated with depth dose curves, dose profiles and absolute dose measurements performed at the ESRF in a water tank and in solid water phantoms with or without bone slabs. A PTW semiflex ionization chamber (0.125 cm3) and gafchromic films were used for the measurements. Results: Computations and measurements in water match within 2 % or 2 mm both in depth and laterally. Computations including a bone slab also match within 2 % in depth, and 3 % or 3 mm laterally. Conclusions: The treatment planning system was validated for dose computations in water and in presence of bone heterogeneities. The last step before treating the first patients is to validate the TPS on dedicated clinical cases, with the presence of contrast media in the tumor.
TU‐E‐BRB‐04: Fast Monte Carlo Calculations in Magnetic Fields with GPUMCD for the MRI‐Linac
Authors: Hissoiny S , Després P , Ozell B , Raaymakers BW
Published: November 2011

Purpose: To develop a fast Monte Carlo code dedicated to a new hybrid imaging‐treatment modality, the MRI‐Linac, involving the irradiation of a patient in the presence of a strong magnetic field (MF). These conditions require a dose calculation engine capable of coping with the effect of the MF on the dose distribution during the planning stage. It is not likely that analytical solutions such as pencil beams calculations can be efficiently adapted for dose calculations within a MF. Monte Carlo simulations seem more appropriate but are typically too slow for a routine clinical utilization, let alone an online image‐based replanning approach. Methods: GPUMCD, a fast GPU‐based Monte Carlo dose calculation platform, was adapted to handle dose calculations within a magnetic field. The code was benchmarked and validated through comparisons with experimental measurements in two cases where large magnetic field induce significant dose effects at air‐tissue interfaces. The validation also included a timing benchmark in a clinically representative prostate case to evaluate if online dose calculation is possible. Results: GPUMCD was found to produce accurate dose distributions, according to a 2%‐2mm gamma analysis, when compared to experimental measurements. Furthermore, execution times of less than 0.4 seconds were achieved for one beam in a prostate case phantom for a 2% statistical uncertainty while 0.8 seconds are required for a 7 beams plan having the same uncertainty. Conclusions: These results suggest that GPUMCD is an interesting candidate for dose calculations for a hybrid MRI‐Linac modality. Its accuracy has been validated against experimental measurements and its speed let envision online replanning based on changes in anatomy found at the time of treatment.
TU‐E‐BRB‐06: Monte Carlo Simulations of a Novel Kilovoltage Radiotherapy Source
Authors: Bazalova M , Weil M , Graves E
Published: November 2011

Purpose: To study the depth‐dose delivery of a novel kilovoltage source using Monte Carlo (MC) simulations. Methods: The large area scanning beam x‐ray source (SBDX) designed for fluoroscopic imaging was modeled for diverging and converging beamlets. The MC model of SBDX was built in the EGSnrc/BEAMnrc code and validated against EBT Gafchromic film measurements in the DOSXYZnrc code. The SBDX was modeled as a number of highly collimated 120 kV x‐ray sources distributed along a line. Simulations were performed of the source arcing around a target beneath the surface in a soft tissue human‐sized phantom. The design of the source was optimized to minimize skin dose with a high beam output. A comprehensive study of the source design included the investigation of incident electron beam arrangement, and collimator design, as well as x‐ray delivery setup, such as the source‐to‐surface distance and beam angles. Results: SBDX depth dose curves for three energies simulated by MC agreed with the measured ones to within 5%. The comprehensive study of the sourceˈs design parameters and x‐ray delivery setup determined optimum parameters for high depth‐to‐skin ratios and beam output of the novel 120 kV source. With these parameters, a 4‐cm diameter, subsurface target was covered with a 75% isodose line, and the corresponding target‐to‐skin ratio was 2.74. Another set of source parameters resulted in a target‐to‐skin ratio of 3.03, however, the beam output was by 80% lower. Conclusions: The dose distributions created with a novel kilovoltage source have been studied using MC simulations, and a possible design for clinical use has been determined.

Sirius Medicine, LLC provided the presenting author with financial support to conduct the research.
TU‐E‐BRB‐08: Dosimetric Impact of Metal Artifact Reduction in Treatment Planning: Phantom and Clinical Studies
Authors: Chen D , Chetty I , Glide‐Hurst C
Published: November 2011

Purpose: To systematically evaluate, in phantom and patient, dosimetric differences obtained by applying metal‐artifact reduction (MAR) algorithm in CT for treatment planning algorithms. Method and Materials: Helical CTs were acquired for six phantom configurations and three patient cases (bilateral hip prostheses, femur, humerus rods). MAR was applied to reconstructed images using Matlab (v7.8) integrated into Extended Brilliance Workspace research platform (Philips Healthcare, Cleveland, OH). Two Cerrobend rods were fabricated for CIRS thorax phantom to investigate interfaces and simulated clinical configurations including bilateral hip prostheses. Dose was calculated on original and MAR‐corrected CTs using Anisotropic Analytic Algorithm (AAA), Pencil Beam Convolution (PBC) in Eclipse, Pencil Beam Convolution (PBC‐BL) and Monte Carlo (MC) algorithms in Brainlab, with and without heterogeneity correction. Dose matrices were evaluated. Statistics from the same regions of interest evaluated sensitivity and accuracy of algorithms between original and MAR‐corrected CTs. Results: In phantom, with heterogeneity correction off, no appreciable dose differences were observed between original and MAR‐corrected CTs. ∼4.0% mean dose difference was observed between original and MAR‐corrected scans for single Cerrobend rod interfaced with lung‐mimicking tissue when calculated with MC. For double Cerrobend configuration, lung‐metal‐bone interfaces yielded 3.0% and 5.0% difference in mean dose for AAA and MC, respectively. For the patient data, dose differences between the original and MAR‐corrected CT scans could be substantial. With the exception of PBC in Eclipse, up to 8 +/− 24% mean dose differences were observed for the 3D conformal plans. The most substantial dosimetric changes were revealed for the MAR‐ corrected bilateral hip prostheses scan, with 12 +/− 29% mean dose differences observed for both PBC and MC implemented in Brainlab. Conclusion: Dosimetric differences revealed between original and MAR corrected CT scans can be substantial, and the results can be used to facilitate implementation of MAR corrected images in treatment planning.

Henry Ford Health Systems holds a research agreement with Philips Medical Systems.
TU‐E‐BRB‐09: Development of a GPU‐Based Monte Carlo Dose Calculation Package for Cancer Radiotherapy
Authors: Jia X , Gu X , Graves Y , Jiang S
Published: November 2011

Purpose: Monte Carlo (MC) simulation is commonly considered as the most accurate dose calculation method in radiotherapy. However, its efficiency still requires improvement for many routine clinical applications. The goal of this work is to develop a GPU‐based MC dose calculation package, gDPM. It utilizes the parallel computation ability of a GPU to achieve high efficiency, while maintaining same particle transport physics as in the original DPM code and hence simulation accuracy.Methods: The gDPM code is implemented on GPU architecture under CUDA platform. In GPU computing, divergence of execution paths between threads can considerably reduce the efficiency. Since photons and electrons undergo different physics and hence attain different execution path, we design a simulation scheme where photon transport and electron transport are separated to partially relieve the thread divergence issue. High performance random number generator and hardware linear interpolation are also utilized. We have also developed various components to account for fluence map and linac geometry, so that gDPM can be used to compute dose for real IMRT or VMAT treatment plans. The gDPM is tested for its accuracy and efficiency in both phantoms and realistic patient cases. Results: In all cases, the average relative uncertainties are less than 1%. Dose difference between CPU and GPU results is less than 3% of maximum dose in over 98% high dose region. A t‐test is also performed and the dose difference is not statistically significant in over 98% high dose region. Speed up factors of 57.3∼75.5 have been observed using an NVIDIA Tesla C2050 GPU card against a 2.27GHz Intel Xeon CPU processor. Dose calculation for a real IMRT head‐and‐neck plan and a VMAT prostate plan can be finished in 48sec and 46sec, respectively. Conclusions: The gDPM package has achieved high computation efficiency on GPU without losing accuracy.

This work is supported in part by the University of California Lab Fees Research Program. GPU cards are partly provided by NVIDIA.