bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐A‐BRB‐04: Real‐Time Catheter Tracking for HDR Prostate Implant Using an Electromagnetic 3D Guidance Device
Authors: Zhou J , Sebastian E , Ghilezan M , Martinez A , Yan D
Published: November 2011

Purpose: In order to increase the accuracy and speed of catheter reconstruction in an HDR prostate implant procedure, an automatic tracking system has been developed using an electromagnetic device. The performance of the system was investigated. Methods: A transmitter with detection range of 36 cm and a sensor with diameter of 0.9 mm were used for needle position tracking during a HDR prostate implant. Due to substantial interference in the electromagnetic field from the surgical table, implant stepper/stabilizer etc, a calibration algorithm using a scattered data interpolation scheme was implemented to correct tracking location error. Reproducibility of the calibration algorithm was determined under various equipment arrangements. A QA phantom with straight catheters was constructed for deriving calibration profiles, and for investigating the accuracy of the system. Tracking of catheter positions was conducted at distances between 140 mm and 280 mm from the transmitter. In addition, the QA phantom was inserted 17 needles with curved trajectories to simulate a typical prostate implant. Needle reconstruction time was recorded and compared to general ultrasound reconstruction times while reconstruction positions were compared to CT reconstructions of the phantom to validate the system. Results: Average tracking accuracies after calibration were 0.4 ± 0.3 mm and 2.4 ±1.7 mm without calibration. The max standard deviation was 0.9 mm in the test range for the reproducibility test. The total tracking time for the 17 catheters was less than 4 minutes and the reconstruction result matches CT data within 2.0 mm. Conclusions: Compared to conventional ultrasound based real‐time catheter reconstruction method in the HDR prostate implant, the system can reduce the error from > 3 mm to < 1.5 mm, shorten the time from 15–60 minutes to < 4 minutes. Furthermore, this technique can also be used for other HDR implants.
WE‐A‐BRB‐06: Detecting Afterloaded Brachytherapy Errors in a Phantom Using Real‐Time Fiber‐Coupled Luminescence Dosimetry
Authors: Kertzscher G , Andersen C E , Siebert F‐A , Nielsen S K , Lindegaard J C , Tanderup K
Published: November 2011

Purpose: To explore the ability of a new dosimetry system to identify imposed PDR and HDR brachytherapy errors (needle swaps and displacements) in a phantom. Methods: The new dosimeter is based on the radioluminescence of a fiber‐coupled carbon doped aluminum oxide crystal. Treatment plans previously used for cervix PDR and prostate HDR brachytherapy in the hospital were replicated by mounting interstitial titanium needles on a perineal template. One needle carried the 1 mm diameter dosimeter probe, positioned in the reconstructed tumor region. The remaining needles were connected to PDR and HDR Varian GammaMed Plus afterloaders, carrying 192‐Ir sources. Irradiations were conducted with all needles submerged in water. Relative crystal and source dwell positions, used for reference TG43 dose calculations, were acquired from CT images of the HDR setup. Several errors were imposed by swapped needle pairs and 2, 5, 10, 20 or 30 mm displacements. Results: Dose measurements that deviated from the null case by more than three standard deviations were defined as potential treatment errors. The standard uncertainty, calculated as the quadrature sum of the repeatability and the position uncertainty, was smaller than 5.7% and 4.4% for all channels and the integrated dose for the PDR and HDR measurements, respectively. Comparisons on a channel‐to‐channel basis correctly revealed imposed treatment errors in 25 PDR cases out of 32. Only five errors were revealed based on the integrated dose comparisons for the complete pulse. The HDR measurements correctly identified 61 out of 72 possible guide tube connection errors. The 11 unidentified errors involved channels with similar dwell times and relative needle‐to‐dosimeter distances. Conclusions: The study demonstrated that time resolved dosimetry can detect errors in brachytherapy that are unseen by integrated dose measurements. The new system correctly identified over 8 out of 10 tested and clinically relevant PDR and HDR brachytherapy errors.
WE‐A‐BRB‐07: Characterization and Use of a 2D‐Array of Ion Chambers for Brachytherapy Dosimetric Quality Assurance
Authors: Yewondwossen M
Published: November 2011

Purpose: The 2D ionization chamber array MatriXX Evolution is one of the 2D ionization chamber arrays developed for megavoltage real‐time absolute 2D dosimetry and verification of IMRT. The purpose of this study is to evaluate the performance of ion chamber array for sub‐megavoltage range brachytherapy beam dose verification and quality assurance. Methods: The dose linearity and energy dependence of the 2D ion chamber array was studied using kilovoltage X‐ray beams (100 to 300 kVp). For the Ir‐192 brachytherapy HDR source dosimetric evaluation the detector response (kuser) factor was determined using 300 kVp beam. The phantom used for this measurement consists of multiple catheters, the IBA MatriXX detector and a slab of RW3 to provide full scattering conditions. The treatment planning system dose distribution was calculated on the CT scan of this phantom. The measured and TPS calculated distributions were compared in IBA Dosimetry OmniPro‐IˈmRT software. The quality of agreement was quantified by the gamma index for nine sets of plans. Using a dedicated phantom capable of receiving 5 brachytherapy intralumenal catheters a QA procedure was developed for end‐to‐end dosimetric evaluation for routine quality assurance checks. Results: The 2D ion chamber array dose dependence was found to be linear for 100 to 300 kVp and kuser showed strong energy dependence for 100 to 300 kVp energy ranges. The maximum mean difference between ion chamber array measured and TPS calculated was 3.7%. Comparisons of dose distribution for different test patterns have shown agreement with greater than 94.5 % for γ ≤ 1 (with 3% delta dose and distance criterion of 2 mm). Dosimetric QA can be performed with the 2D ion chamber array. Conclusions: The MatriXX Evolution ionization chamber array has been found to be reliable for measurement of both absolute dose and relative dose distributions for the Ir‐192 brachytherapy HDR source.
WE‐A‐BRB‐08: Comparison of Brachytherapy Dose Distribution Using the Gamma‐Index Method
Authors: Yang Y , Rivard M J
Published: November 2011

Purpose: The gamma‐index method was developed to quantitatively compare treatment planning system (TPS)‐derived dose distributions for external‐beam radiotherapy with measured dose distributions. However, the clinical medical physicist does not measure brachytherapy dose distributions and the use of this method for brachytherapy appears novel. The purpose of this study was to evaluate the accuracy of several TPS‐derived brachytherapy dose distributions in comparison to reference brachytherapy dose distributions, and suggest dose and distance criteria such as those recommended in the AAPM Task Group 56 report. Methods: Reference brachytherapy dose distributions from Monte Carlo (MC) simulations were commissioned into the Pinnacle TPS. MC and TPS dose distributions for several HDR and LDR sources were imported into the OmniPro IˈmRT software and compared. Sensitivity of distance‐to‐agreement for 1 mm =< delta(d) =< 5 mm and dose difference for 1% =< delta(D) =< 10% were investigated. TPS dose characterization was considered successful when at least 98% of all pixels examined satisfied a pass tolerance r =<1.00. Results: At least 98% pixels passed for delta(d) = 2 mm and delta(D) = 2%. For delta(d) >= 3 mm and delta(D) >= 3% criteria, r =< 1.00 for all pixels. Failure regions were located within the brachytherapy source, near the brachytherapy source surface, or in high dose‐gradient regions (>50%/mm). A potentially useful standard is delta(d) = 2 mm and delta(D) = 2%. Conclusions: The gamma‐index method was used to evaluate brachytherapy dose distribution comparisons, and agreement criteria were proposed. The medical physics community may further investigate this method and consider standardized criteria for brachytherapy dosimetry.
WE‐A‐BRB‐09: Brachytherapy Using Pyroelectric Based X‐Ray Sources
Authors: Klopfer M.J. , Satchouk V. , Yu F. , Molloi S
Published: November 2011

Purpose: To assess the feasibility of a miniature pyroelectric electron and x‐ray sources for brachytherapy applications. Methods: Polarized z‐cut lithium niobate crystals that initially measured 1 cm̂3 were cut into various thicknesses. Samples were placed individually in a glass chamber held at 1×10̂‐3 Torr, and heat propagation measurements were taken on opposing z‐axis crystal faces. For electron and x‐ray measurements, crystals were mounted to a 200 micron thick 1 cm̂2 substrate of high carbon steel. A 35° copper electron wedge target was placed 0.8 cm from the crystal face. The crystal substrate was heated with a Fluxeon Royer‐based induction heater operating at 62 KHz. The liberated electron current was measured using a Keithley 614 electrometer. X‐ray spectroscopy and count rate measurements were made using an Ortec 905‐3 NaI(Tl) detector with an Ortec Trump‐32 MCA and a PC based Geiger‐Muller counter, respectively. Results: Induction heating with a total device current of 212W produced an initial substrate heating of 2.3°C per second from 23°C to 125°C with a maximum tempreture of 149°C in 67 seconds during material testing. Linear heating of the 1 cm thick crystal on the face opposite the substrate was observed (0.182°C/s rise) between 32°C and 68°C over the course of 240 seconds. Heating of 0.33 °C/s was measured during device operation from 22°C to 149°C. Crystals of 1 cm thickness produced x‐ray emissions with a maximum energy of 39 keV. Emission calculations indicate that 7.8×10̂1 1 electrons were produced. This corresponds to an equivalent peak source activity of 0.6 mCi, assuming a 1 % conversion of electrons to X‐ray photons. During the heating period, an emission in packed bursts with a peak current of 4×10̂‐10A was measured. Conclusions: Pyroelectric based emitters could potentially be used as miniature electron and x‐ray sources for radiation therapy and imaging applications.
WE‐A‐BRB‐11: Evaluation of Cervical Cancer Radiation Therapy Using External Beam Therapy and Brachytherapy
Authors: Biggers T , Esquivel C , Stathakis S , Gutiérrez A , Papanikolaou N
Published: November 2011

Purpose: Evaluate the treatment of cervical cancer using High Dose Rate Iridium‐192 tandem and ovoids with the addition of external beam sidewall boosts was evaluated using deformable registration software. Methods: High dose rate tandem and ovoids treatments were planned using Oncentra 4.0 and an HDR Iridium‐192 source. Each patient was treated with five to six fractions with total dose to ICRU 38ˈs point A ranging from 28 Gy to 35 Gy. Following the HDR treatment, patients received external beam pelvic sidewall boosts created in Pinnacle 9.0 to a prescription dose of 3.4 to 9 Gy. Using Velocity AI software, the image sets from each tandem and ovoid plan were registered to the external beam treatment plan using either rigid or deformable registration. The dose files were added together using the registration created between the T&O CT sets and the sidewall boost CTs. Contours were exported from the treatment planning system for the bladder, rectum and uterus. Dose volume histograms were created to evaluate the treatments delivered. Results: Using dose volume histograms, the average doses to the rectum and bladder were determined for volumes of 0.1cc, 1cc and 2cc. For one representative patient, the total dose to 1cc of the bladder was 74.12 Gy and 1cc of rectum average was 33.46 Gy. The combined dose to five percent of the uterus volume was 100.07 Gy. Conclusions: The rectum average dose corresponded to approximately half of the average bladder dose for the three volumes measured. The doses for these two structures were well below the dose limits given in Emami, et al. The Velocity AI is a useful deformable registration tool for evaluating HDR and external beam treatments to the pelvic region.
WE‐A‐211‐02: An Analysis of Recent Literature regarding Radiation Risk
Authors: Wagner L , Boice J
Published: November 2011

The peer review process screens scientific articles for merit prior to acceptance or rejection for publication. After publication the process continues with scrutiny by other researchers as expressed in letters to the editor and other scientific research that either affirms or denies findings. Research into radiation effects directly affects the use of ionizing radiations in medicine. The quality of peer review of articles on radiation effects is therefore critical to the practice of medicine. This presentation will examine adequacy of peer review regarding recent articles on radiation effects that have appeared in the peer‐reviewed literature. The purpose is to examine what factors in research techniques and analyses contribute to the quality and believability of the findings.

Learning objectives:

1. To gain insight into the critical evaluation of scientific literature on bioeffects

2. To understand how to distinguish causation from correlation or association
WE‐A‐211‐03: BEIR VII: What It Does and Doesnˈt Say
Authors: OˈConnor M
Published: November 2011

Background: Over the last 2 years, there has been considerable attention focused on the potential cancer risks from medical imaging procedures, particularly with the widespread use of multislice CT. Almost all studies rely upon the BEIR VII report (Biological Effects of Ionizing Radiation panel formed under the auspices of the National Academy of Sciences) to generate an estimate of the risk of cancer from a given procedure. In doing so, most studies treat the BEIR VII report as a solid basis of scientific evidence for estimation of cancer risk. In reality, a close reading of this report shows that there are a large number of assumptions inherent in all aspects of the estimates of cancer risk — a fact that is often and clearly stated in the report.

This presentation will review some of the assumptions used by the BEIR panel to calculate cancer risk, including the impact of different models (excess absolute risk vs. excess relative risk), the dose and dose rate effectiveness factor (DDREF) and relative biological effectiveness (RBE), on cancer estimates.

Often lost in the discussion on medical exposure is a reference level by which exposure levels can be compared to something that unavoidable and impacts everyone on earth — background radiation. This presentation will review the consequences of applying the BEIR model to background radiation and known variations in levels of background radiation throughout the U.S., and how the cancer rate from background compares with that from medical imaging.

Learning Objectives

1. Understand the assumptions underlying the BEIR VII report

2. Be able to compare the relative risks of medical imaging procedures to that from background radiation
WE‐A‐301‐01: Characterization of an Adaptive Statistical Iterative Reconstruction (ASiRTM) Algorithm in CT: A Pediatric Perspective
Authors: Brady S , Kaufman R
Published: November 2011

Purpose: This study sought to characterize the effect on image quality and the potential for dose reduction in computed tomography (CT) scanning with an adaptive statistical iterative reconstruction (ASiR™) technique. Methods: The study consisted of (1) characterizing image quality metrics established by the American College of Radiology (ACR) CT accreditation program as a function of ASiR™; (2) calculating the noise power spectrum (NPS) to assess the effect of ASiR™ on noise quality and texture in the reconstructed images; (3) establishing theoretical and practical maximum dose reduction limits with ASiR™ reconstruction for a pediatric population ranging from 1 year old through adolescence. Results: ASiR™ was shown to have no deleterious effects on image quality as assessed by ACR criteria. The assessment of low contrast resolution was found to improve due to reductions of noise magnitude in the reconstructed images. The NPS was calculated for (0–100)% ASiR™ reconstruction. The 0% ASiR™ NPS was centered at 3.2 lp cm‐1 and the 100% ASiR™ spectrum was shown to have shifted to 1.6 lp cm‐1 with a 50% diminished noise power spectral peak. As the noise spectrum shifted towards lower frequencies, the noise texture took on a coarser graininess. When compared with 0% ASiR™, lower frequency reconstructed images (50%, and 100%) ASiR™ demonstrated increased object boundary blurring of (0.3 and 0.5) mm, respectively. For the entire pediatric population, a maximum dose reduction of (50–55)% was demonstrated at (60–70)% ASiR™, but with low contrast boundary blurring of ∼0.4 mm; however, 40% ASiR™ had dose reductions between (20–31)% with a blurring of ∼0.1 mm. Conclusions: All image quality tests were found to meet ACR criteria. A dose reductions of (20–31)% can be achieved for pediatric populations with no change in image quality, little impact on low contrast object boundary blurring, or change in noise texture quality.
WE‐A‐301‐02: Four‐Dimensional Cone Beam CT Reconstruction and Enhancement with a Temporal Non‐Local Means Method
Authors: Jia X , Tian Z , Lou Y , Jiang S
Published: November 2011

Purpose: Four‐dimensional Cone Beam Computer Tomography (4DCBCT) can provide respiratory phase resolved volumetric images in image guided radiation therapy. However, the undersampling of projections in each phase results in obvious streaking artifacts under the conventional FDK algorithm. In this work, we propose a novel iterative 4DCBCT reconstruction algorithm and an enhancement algorithm utilizing temporal nonlocal mean (TNLM) method. Methods: For reconstruction, we introduce a TNLM term in the optimization model. Such a term favors those 4DCBCT images such that any anatomical features at one spatial point in one phase can be found in a nearby spatial point in neighboring phases. As for the image enhancement, 4DCBCT images obtained from the FDK algorithm are enhancement by minimizing the TNLM function while requiring that the solution is close to the FDK results. A forward‐backward splitting algorithm and a Gauss‐Jacobi iteration method are employed to solve the problems. The algorithms are implemented on GPU to achieve a high computational speed. Our algorithms have been tested on a digital NCAT phantom and a clinical patient case. Results: Our reconstruction algorithm and the enhancement algorithm generate visually similar 4DCBCT images, but both better than FDK results. Quantitative evaluations indicate that, compared to the FDK reconstruction results, our reconstruction method improves contrast‐to‐noise‐ratio (CNR) by a factor of 2.56∼3.13 and our enhancement method increases CNR by 2.75∼3.33 times. The enhancement method also removes over 80% of the streak artifacts from the FDK reconstruction results. The total computation time is ∼460 sec and ∼610 sec on an NVIDIA Tesla C1060 GPU card for the reconstruction and the enhancement algorithm, respectively. Conclusions: Our new reconstruction and enhancement algorithms can effectively reduce the image artifacts in 4DCBCT. Comparing the two algorithms, the resulted image qualities are similar. The shorter computation time makes the enhancement algorithm more attractive.
WE‐A‐301‐06: Adaptive Prior Image Constrained Compressed Sensing‐Based CBCT Reconstruction Algorithm
Authors: Lee H , Xing L , Lee R
Published: November 2011

Purpose: Cone‐beam CT (CBCT) images are acquired repeatedly during a course of radiation therapy and a natural question to ask is whether CBCT images obtained earlier in the process can be utilized as prior knowledge to reduce patient imaging dose in subsequent scans. The purpose of this work is to develop an adaptive prior image constrained compressed sensing (APICCS) method to solve this problem. Methods: The smoothed prior images are utilized as an initial guess and are incorporated into the objective function under the PICCS framework. The clustered prior images are additionally employed to detect any possible mismatched areas compared with the current images that are classified by the k‐means algorithm at each iteration step. A distance transformation is then introduced to convert the mismatched information into a weighted relaxation map for an adaptive update. In constructing the relaxation map, the matched regions between the prior and current images are assigned with smaller values and thus are much less influenced by the sparse projections, thereby leading to fewer streaking artifacts. On the other hand, mismatched regions are associated with larger values and the regions are updated more by the new projections, thus avoiding any possible adverse effects of prior images. The APICCS approach was assessed by using patient data acquired under standard‐ and low‐dose protocols. Results: The APICCS method provides an effective way to enhance the image quality at the matched regions between the prior and current images compared to the existing PICCS algorithm. In addition, the APICCS algorithm allows an imaging dose reduction of 10 to 40 times due to the greatly reduced number of projections and X‐ray tube current. Conclusions:The APICCS technique allows us to effectively take advantage of previously obtained CBCT images and provides high quality CBCT images with sparse projections.

This work was supported in part by Mid‐career Researcher Program (2009‐0085999) through NRF grant funded by the MEST and in part by the Industrial Strategic Technology Development Program (10035495) funded by the Ministry of Knowledge Economy (MKE, Korea).
WE‐A‐301‐08: In Vivo Evaluation of a Strategy to Reduce Partial Scan Reconstruction Artifacts in Myocardial Perfusion Computed Tomography
Authors: Ramirez‐Giraldo J C , Jorgensen S M , Ritman E L , Kantor B , McCollough C H.
Published: November 2011

Purpose: The quantitative accuracy of CT numbers in myocardial perfusion computed tomography (MPCT) is degraded by artifacts arising from the use of partial scan reconstruction (PSR), which is used in cardiac CT to improve temporal resolution. PSR artifacts appear because of inconsistencies in the angular range of projection data used for PSR. The purpose of this study was to demonstrate the ability of targeted spatial frequency filtration (TSFF) to reduce PSR artifacts in animal studies. Methods: TSFF superposes the high frequency information from a PSR, which contains optimal temporal resolution, with the low frequency information from a full (360‐deg) scan, which contains optimal CT number accuracy. We scanned 4 pigs with an MPCT protocol that had x‐rays continuously on, using 120kVp and 90mAs/rotation. Animals were scanned under two conditions: locked and unlocked. In the locked condition, the animalˈs heart was paced in synchrony with gantry rotation, guaranteeing consistent angular ranges in the projection data for the desired position in the RR interval. This avoids PSR artifacts. In the unlocked condition, cardiac pacing was not used, leading to variations in the angular projection range associated with any specific point in the RR interval. Filtered backprojection was used to reconstruct partial and full scans at 70% of the RR interval. Time attenuation curves (TACs) were calculated in the myocardium and back muscle. Results: TACs in the back muscle, which should have been flat, had a mean standard deviation of 13.9HU, 2.29HU and 1.12HU over all 4 animals, for the unlocked, locked and unlocked+TSFF conditions, respectively. For the myocardium, the root mean squared error was 5.9HU and 2.45HU for the unlocked and unlocked+TSFF corrected images with respect to the gold standard (locked condition). Conclusions: The TSFF algorithm effectively suppressed PSR artifacts in vivo, improving the accuracy of CT numbers in MPCT.

This work was supported in part by the American Heart Association Predoctoral Fellowship No. 10PRE2560028 and by the NIH Opus CT Imaging Resource Construction Grant No. R018898.
WE‐B‐110‐02: Diagnostic Exposure Tracking in the Medical Record
Authors: Seibert JA
Published: November 2011

The Electronic Medical Record (EMR) represents the collection of diagnostic tests and procedural test information related to an individual patientˈs history of care at a health center. In the context of medical diagnostic imaging, this relates to the access to imaging procedures, the written diagnoses from the imaging experts, and of increasing relevance and importance, the radiation dose reports for the procedures. The EMR is also emerging as the gateway for computerized order entry for imaging exams, in which the imaging history and accumulated radiation dose will be made available for the referring physician from various imaging procedures, such as interventional radiology and cardiology, computed tomography, and nuclear medicine. Integrating the Healthcare Enterprise (IHE) Radiation Exposure Monitoring (REM) profile specifies how information related to dose can be extracted from modalities that are compliant with the DICOM Radiation Dose Structured Report (RDSR). However, once the information is collected via the RDSR, appropriate steps must be taken to parse the data according to exam types, body area scanned, and dose metrics provided in order to apply conversion factors to estimate an effective dose for a procedure. Effective dose estimates can be considerably under or overestimated, depending on the modality, the patient size, machine calibration errors, and a host of issues that are under current investigation. In this presentation, a review of the various dose metrics for the modalities is discussed, as are current methods to calculate the effective dose. Ultimately, to post the dose information in the EMR, a dose‐management actor described by the IHE REM profile captures the pertinent dose information from each modality and study, parses the data and computes the effective dose according to defined conversion methods. Each individual dose report message transmitted to the EMR is stored in the patient dose report file defined by medical record number, which updates the dose index raw data (e.g., DAP in Interventional radiology, CTDIvol, DLP in CT), the calculated effective dose per procedure, and total cumulative effective dose for the patient.

Learning objectives:

1. Understand the various dose metrics produced by the imaging modalities.

2. Determine how effective dose can be estimated for a given procedure with the dose index values provided by a modality.

3. Understand limitations of effective dose calculations, the wide range of under/over estimates that can occur for a specific procedure, and the limitations of the total cumulative patient effective dose.
WE‐B‐220‐03: Treatment of Localized Prostate Cancer Using Magnetic Resonance Imaging‐Controlled Ultrasound Therapy
Authors: Chopra R
Published: November 2011

Widespread PSA screening and transrectal biopsy has led to an increase in the diagnosis of localized prostate cancer in younger men, and at an earlier stage of disease. While treatment at this stage is associated with good long‐term survival rates, existing therapies are burdened with high complication rates to sexual, urinary and bowel function. Furthermore, diagnosis of prostate cancer is based on sampling of less than 1% of the glandular volume, and many men are overtreated for a disease that is clinically insignificant. Improvements to the localization of prostate cancer within the gland would lead to better decisions with respect to treatment. The introduction of minimally‐invasive treatments for localized prostate cancer with reduced complications would also be an attractive option for patients and healthcare providers.

Our group has been exploring the role of MRI in both the diagnosis and treatment of localized prostate cancer for over a decade. Multi‐parametric MRI has been shown to provide good spatial localization of disease through a combination of multiple complementary tissue parameters. In this realm, our group has been exploring the potential of integrating tissue stiffness measurements through a technique known as MR elastography. Current efforts are focused on translating endorectal MRE into preliminary human evaluation. With respect to treatments, our focus for the past 10 years has been on the development of MRI‐guided transurethral ultrasound therapy, a minimally‐invasive approach for the delivery of high‐intensity ultrasound to the gland. This technology has been translated from concept to clinic by our research group, and preliminary results indicate the approach is feasible, and has the potential for precise thermal destruction of the whole prostate, or sub‐volumes within the gland.

This seminar will describe our efforts to exploit MRI for both diagnostic and therapeutic applications in prostate cancer management.
WE‐C(SAM)‐BRC‐01: Quality Management Systems in Radiotherapy: Making Treatments Safer
Authors: Ford E , Mutic S
Published: November 2011

Though all medical physicists appreciate the need for safe high‐quality radiation treatments, most have no formal training in quality management or error proofing. This educational course will explore two quality improvement tools that are considered standard in other industries: incident learning and prospective hazard analysis. The focus will be on practical methods that can be employed across a variety of clinics. With slight variations, these same tools can also be applied to the diagnostic setting. In other areas of medicine the systematic use of such tools has brought about measureable improvements in patient safety and treatment quality, and it is expected that radiation oncology can benefit in a similar fashion. The learning objectives of this educational SAMS course are: understand the benefit of incident learning and the pitfalls associated with it, understand the principles of how to construct an effective incident reporting system, understand the tools available for prospective hazard analysis and how to streamline their use.
WE‐C(SAM)‐211‐02: Magnetic Resonance Safety Guidelines: Update, 2011
Authors: Kanal E
Published: November 2011

Adverse events involving magnetic resonance safety breaches have helped to bring the topic of MR safety into sharp focus in the professional as well as lay press. In response to these events, the American College of Radiology formed a Blue Ribbon Panel on MR Safety — the ACR MR Safety Committee ‐ to review current state of the art for MR safety practices and standards, and issue recommendations that might help sites establish their own MR Safe Practice Guidelines, Practices, and Policies. This presentation will present specific recommendations incorporated into the ACR MR Safe Practice Guidelines document, initially released in 2001 and subsequently updated in 2004, 2007, and now again in 2011. These include site access restrictions and the four zone concept surrounding all MR installations, MR safety education recommendations, and specific patient practices designed to standardize our collective approach to dealing with the unique safety considerations associated with clinical and research MR sites throughout the world today.
WE‐C‐BRA‐03: Acceptance Testing and Commissioning of a Commercial 3D Surface Matching Video System
Authors: Al‐Hallaq HA
Published: November 2011

Non‐invasive 3D surface matching systems have become commercially available forinitial patient positioning and real‐time monitoring during radiotherapy treatment. Some systems are capable of providing surface motion surrogates that can be used for respiratory gating. All systems must undergo commissioning and acceptance prior to clinical use. First, clinical implementation of these systems requires the establishment of routine quality control proceduresthat range from phantom studies to monitoring clinical setups.In particular, the congruence of the surface imaging isocentermust be compared to both the imaging and treatment radiation isocenters. Isocenter congruence accuracy limitations may need to be tailored to the treatment site. For example, tighter accuracy is expected of isocenter congruence for treatment monitoring ofstereotactic radiosurgery patients compared to monitoring of breast patients due to the smaller planning target volume margins. For clinical commissioning studies, the correlation of 3D surface matching compared to the routinely‐used image‐guided procedures should be well characterized. Furthermore, understanding the accuracy, robustness, and limitations of the algorithms used to register two 3D surfaces is key to understanding the expected clinical results. We will summarize our institutional experience with acceptance testing and commissioning the AlignRT (VisionRT Ltd., London, UK) 3D surface matching system and its clinical implementation for positioningpatients receiving whole breast radiotherapy.

Learning Objectives:

1. List some acceptance testing procedures for surface imaging systems

2. Understand the commissioning process of surface imaging systems for whole breast radiotherapy

3. Understand how surface imagingisocenter congruence testing must be incorporated into ongoing quality assurance of image‐guided RT (IGRT)
WE‐C‐BRB‐06: Analyzing the Impact of Intra‐Fraction Motion: Correlation of IMRT QA Metrics with D95%
Authors: Waghorn B , Meeks S , Langen K
Published: November 2011

Purpose: Motion‐encoded dose distributions, taking into account intra‐fraction motion during intensity modulated radiation therapy (IMRT), can be determined both computationally and experimentally, with a number of analysis techniques available to quantify the dosimetric changes. The analysis results can provide important information regarding the clinical impact of motion and the appropriateness of a given treatment plan. This study provides a comparison of different analysis techniques performed on computationally predicted motion‐encoded dose distributions. Methods: A total of 3,768 motion‐encoded dose distributions were calculated computationally for 38 step‐and‐shoot and 38 compensator IMRT plans across 9 lung patients. The motion‐encoded dose distributions were compared to static dose distributions using four analysis techniques: 2D and 3D gamma, histogram (looking at the fraction of voxels with a dose deviation exceeding 3% of the prescription dose) and dose volume histogram (DVH) analyses. Tests were also implemented to separate failing voxels caused by either over‐dosing or under‐dosing. In addition tests were performed both globally (not taking into account the planning regions of interest) and within restricted regions of interest, such as the target volume. Results: Global analysis techniques did not accurately predict clinically relevant dosimetric changes in the target D95%. Three‐dimensional gamma and histogram analyses, localized within the target and considering only voxels experiencing decreased doses due to motion, provided the strongest correlations with changes in D95% (r,2=0.68 and r,2=0.71 respectively). A global 2D gamma analysis correlated less well with changes in D95% (r,2=0.44), and was both less specific and sensitive. Conclusions: This study suggests that any clinical decisions based solely on 2D or global measurement techniques may not provide adequate dosimetric information about the effect of motion on IMRT delivery. Care needs to be taken in determining the appropriate analysis technique and in interpreting the results in order to understand the relevant dosimetric changes caused by motion.

This work was supported in part by .decimal, Inc.
WE‐C‐BRB‐08: Independent Dose Calculation Followed by Dynalog File Analysis as an Alternative for Measurement Based IMRT QA
Authors: Sun B , Boddu S , Goddu S , Yang D , Rangaraj D , Mutic S
Published: November 2011

Purpose: Experimental methods are commonly used for patient‐specific IMRT verification. The aim of this work is to investigate the possibility of substituting the time and labor intensive IMRT QA with calculation based dose verification and log file analysis. Method: 11 IMRT plans (5 head and neck plans, 3 rectum plans, 3 breast plans and 5 prostate plans) made using Pinnacle were recalculated using a QA phantom. All the plans were verified by ICs and 2D MapCheck measurements and compared to the independent dose calculation using Eclipse. The deviations between dosimetric measurements and independent dose calculation in a QA phantom were evaluated. The plans with patient anatomy were imported to Eclipse for 3D dose calculations. The DVHs and point doses calculated by Pinnacle and Eclipse are evaluated for PTV and critical structures. To verify data transfer and performance of the delivery unit dynalog file analysis was performed.

Results: Average deviation between IC measurements and point dose calculations with Pinnalce and Eclipse for Head and Neck were 1.1±1.3% and 1.4±1.6%, respectively. For MapCheck measurement, the mean gamma value with 3% dose difference and 3 mm distance‐to‐agreement were within 1.5% for most plans. The mean 3D dose differences calculated from two different treatment systems are with 3 % for Head‐and‐Neck cases and are within 2% for other plans. The dynalog analysis shows that the gantry angle, jaw position, collimator angle and MLC positions have the passing rate of above 97%. The independent dose calculation with the dynalog analysis takes only 37 minutes, while experimental approach, which takes up to 3 hours. Conclusion: Independent dose calculation followed by dynalog file analysis is a reliable tool to verify the IMRT treatment. With the IMRT QA program becoming more mature, independent dose calculations and dynalog analysis may be used to replace experimental based verification methods.
WE‐C‐214‐02: Six‐Sigma Tools for a “No‐Fly”Patient Safety Oriented, Quality‐Checklist Driven, Paperless Multi‐Center Radiation Medicine Department
Authors: Kapur A , Potters L , Mallalieu L Brewster
Published: November 2011

Purpose: The purpose of this study was to develop six‐sigma practices towards the enhancement of patient safety in an electronic, quality checklist (QCL) driven, multi‐center, paperless radiation medicine department. Methods:A baseline QCL process map (QPM), stratified into consultation through treatment‐completion stages was incorporated into the Mosaiq Oncology‐Information‐Systems platform. A cross‐functional quality management team conducted Quality‐Function‐Deployment (QFD) and DMAIC [Define/Measure/Analyze/Improve/Control] six‐sigma exercises with a focus on patient safety. QPM procedures were ranked in order of patient‐safety risk with Failure‐Modes‐and‐Effects‐Analysis (FMEA). Quantitative metrics for a grouped set of nine highest‐risk procedures were established. These included procedural delays, associated standard deviations and Z‐scores. Custom Crystal reports to extract QCL procedural data from Mosaiq were created. Baseline performance of the QPM was established over the previous year of usage. Data driven analysis led to simplification, standardization and refinement of the QPM with standard deviation, slip‐day reduction and Z‐score enhancement goals. In addition to standard‐deviation reduction, a No‐Fly‐Policy (NFP) for patient safety was introduced at the control DMAIC phase, with a process‐map interlock imposed on treatment initiation in the event of FMEA‐identified high risk tasks being delayed or not completed. The NFP was introduced in a pilot study with specific stopping rules and the same metrics used for performance assessments. A custom root‐cause‐analysis (RCA) database was deployed to monitor patient safety events. Results: Relative to the baseline phase, average slip days and standard deviations for the risk‐enhanced QPM procedures improved by over three‐fold factors in the NFP phase. Z‐scores improved by 25%. A trend for proactive delays instead of reactive hard stops was observed with no adverse effects of the NFP. Conclusions: With complex technologies, resource‐compromised staff and pressures to hasten treatment initiation, the use of six‐sigma driven process interlocks may mitigate patient safety risks as demonstrated in this study.
WE‐C‐110‐01: Volume‐of‐Interest Scanning Technique in Multi‐Slice CT: A Feasibility Study
Authors: Chen L , Yu L , Leng S , McCollough C
Published: November 2011

Purpose: To evaluate the feasibility of Volume‐of‐Interest (VOI) scanning in multi‐slice CT to reduce radiation dose while maintaining image quality within the VOI. Methods: Scanning patients with a limited scan field‐of‐ view can substantially reduce radiation dose but usually cause severe truncation artifacts. VOI scanning involves adding a filter in the x‐ray beam to strongly attenuate peripheral photons, so that much lower x‐ray intensity is delivered to the region outside a preselected VOI while allowing the original intensity within the VOI. A semi‐anthropomorphic abdominal phantom was sequentially scanned with 240, 180, 120, 60, 30, 15 and 10 mAs at 120 kVp on a dual source CT scanner. A 10‐cm diameter cylindrical VOI was selected at the center of phantom. Six rods with various attenuation levels were located within the VOI. Projection data outside the VOI were replaced with data acquired with lower mAs to simulate VOI projection data. CT images were reconstructed using same reconstruction kernels as the full dose scan. CT numbers and noise were measured on images with and without the VOI filter. Radiation dose with and without the VOI filter was estimated using 16 projection views over a 180 range where the VOI filter was manually placed in the x‐ray beam.. A simulated VOI study was also performed using patient data. Results: CT numbers and noise inside the VOI were comparable to those obtained with a full dose scan for mAs level outside the VOI as low as 6.25% of the full mAs. Radiation dose outside the VOI was reduced up to 50%‐65%, while dose inside the VOI was reduced by 25%–30%. Diagnostic information within the VOI appeared to be preserved, although only large anatomic structures outside the VOI were visible. Conclusions: VOI scanning is feasible in multi‐slice CT and may substantially reduce patient dose, while preserving image quality inside the VOI.
WE‐C‐110‐05: The Influence of Beam Filtration and Collimation on CT Number Accuracy in the ACR CT Accreditation Process
Authors: Olariu E , Supanich M , Bakalyar D
Published: November 2011

Purpose: The ACR accreditation process requires the submission of images of the 200 mm ACR phantom to evaluate CT number accuracy using the institutionˈs adult abdomen protocol. Difficulties in obtaining CT numbers that fall within the allowed limits may be due to the use of a protocol designed for a body significantly larger than the phantom. We show that adjusting the sFOV to a size appropriate for the phantom significantly shifts the CT numbers toward the expected values. We also show that consistent with the hypothesis that an over‐correction for scatter results in the increased CT numbers, a reduced collimation, where less scatter correction is required for reconstruction, also shifts the CT numbers in the right direction. Methods: The ACR Gammex phantom was scanned on a 64‐slice GE LightSpeed‐VCT scanner with various bowtie filters, beam collimation and sFOV using our institution`s routine adult abdomen protocol. Results: Our results show that the CT numbers for water and polyethylene fall well outside the required range if we rigidly adhere to scanning the ACR phantom with the standard protocol. The observed inaccuracy in reported CT numbers is believed to originate from over‐corrections due to scatter contributions and beam hardening effects as the phantom is significantly smaller than a typical adult abdomen. CT number accuracy was improved when a small bowtie filter was used instead of the large one. The CT number dropped to 4.02 HU for water and to −87.32 for polyethylene. CT number accuracy further improved when scanning the phantom with a 20 mm beam collimation instead of 40 mm. Conclusions: In performing the ACR image quality assessment task, the employment of a bowtie filter consistent with the size of the phantom resulted in a significant improvement in achieving the CT number accuracy requirements of the ACR.
WE‐C‐110‐10: Reducing Dose to Breast Glandular Tissue by Adjusting the Tube Start Angle and Table Height in Helical CT Scans
Authors: Zhang D , Khatonabadi M , Turner A , Cagnon C , DeMarco J , McNitt‐Gray M
Published: November 2011

Purpose: To investigate potential radiation dose reduction to peripheral organs (such as glandular breast tissue) of the patient during helical CT exams by adjusting the tube start angle and table height. Methods: A Radcal 0.6cc ionization chamber was placed on the anterior surface of an anthropomorphic thorax phantom. Helical CT scans were performed on a Siemens Sensation 64 CT scanner using 24×1.2mm collimation, 120kVp, 100mAs with a pitch of 1.5. CareDose4D was turned off. The table was set to a variety of heights (table height of 100mm, 130mm, 160mm, 200mm, and 255mm) to investigate the effect of table height on peripheral organ doses. Since the tube start angle is random and is not under the userˈs control for helical scans, 24 helical scans were performed under each table height to yield a variety of tube start angles. The exposure of the ionization chamber for each scan was recorded. After scanning, the raw projection data were extracted and read in by a Siemens proprietary MATLAB code to obtain the tube start angle for each scan. Results: At a fixed table height, the exposure varies by more than a factor of two depending on the tube start angle. As the table moves higher (the ionization chamber closer to the top of the gantry), the exposure decreases. While keeping all the scanning parameters (kVp, mAs, pitch) the same, by just adjusting the table height and the tube start angle, the lowest measured exposure is 732mR, while the highest measured exposure is 2810mR. Conclusions: The uncontrolled tube start angle in current commercial CT scanners results in great uncertainties in dose to peripheral organs. Moving the table up decreases anterior organ doses. By adjusting both the tube start angle the table height, dose to a point in glandular breast tissue could be reduced by 74%.