bluuebunny/crossref_metadata_2025 huggingface dataset:
MO‐DE‐207‐04
Authors: Krishnamurthy R.
Published: June 2015

This imaging educational program will focus on solutions to common pediatric imaging challenges. The speakers will present collective knowledge on best practices in pediatric imaging from their experience at dedicated children's hospitals. The educational program will begin with a detailed discussion of the optimal configuration of fluoroscopes for general pediatric procedures. Following this introduction will be a focused discussion on the utility of Dual Energy CT for imaging children. The third lecture will address the substantial challenge of obtaining consistent image post ‐processing in pediatric digital radiography. The fourth and final lecture will address best practices in pediatric MRI including a discussion of ancillary methods to reduce sedation and anesthesia rates.

Learning Objectives:

To learn techniques for optimizing radiation dose and image quality in pediatric fluoroscopy

To become familiar with the unique challenges and applications of Dual Energy CT in pediatric imaging

To learn solutions for consistent post‐processing quality in pediatric digital radiography

To understand the key components of an effective MRI safety and quality program for the pediatric practice
MO‐PIS‐Exhibit Hall‐2: GE Healthcare, Global Dose and Education Services
Authors: Miller D.
Published: June 2015

No Abstract provided
MO‐PIS‐Exhibit Hall‐3: Proactive Changes through Dose Analysis
Authors: Judd I.
Published: June 2015

No Abstract provided
MO‐E‐213‐00: What Is Medical Physics Without Radiation Safety?
Authors: Rehani Madan
Published: June 2015

The focus of work of medical physicists in 1980's was on quality control and quality assurance. Radiation safety was important but was dominated by occupational radiation protection. A series of over exposures of patients in radiotherapy, nuclear medicine and observation of skin injuries among patients undergoing interventional procedures in 1990's started creating the need for focus on patient protection. It gave medical physicists new directions to develop expertise in patient dosimetry and dose management. Publications creating awareness on cancer risks from CT in early part of the current century and over exposures in CT in 2008 brought radiation risks in public domain and created challenging situations for medical physicists. Increasing multiple exposures of individual patient and patient doses of few tens of mSv or exceeding 100 mSv are increasing the role of medical physicists. Expansion of usage of fluoroscopy in the hands of clinical professionals with hardly any training in radiation protection shall require further role for medical physicists. The increasing publications in journals, recent changes in Safety Standards, California law, all increase responsibilities of medical physicists in patient protection. Newer technological developments in dose efficiency and protective devices increase percentage of time devoted by medical physicists on radiation protection activities. Without radiation protection, the roles, responsibilities and day‐to‐day involvement of medical physicists in diagnostic radiology becomes questionable. In coming years either medical radiation protection may emerge as a specialty or medical physicists will have to keep major part of day‐to‐day work on radiation protection.

Learning Objectives:

To understand how radiation protection has been increasing its role in day‐to‐day activities of medical physicist

To be aware about international safety Standards, national and State regulations that require higher attention to radiation protection than in past

To be aware about possible emergence of medical radiation protection as a specialty and challenges for medical physicists.
MO‐E‐213‐01: Increasing Role of Medical Physicist in Radiation Protection
Authors: Rehani M.
Published: June 2015

The focus of work of medical physicists in 1980's was on quality control and quality assurance. Radiation safety was important but was dominated by occupational radiation protection. A series of over exposures of patients in radiotherapy, nuclear medicine and observation of skin injuries among patients undergoing interventional procedures in 1990's started creating the need for focus on patient protection. It gave medical physicists new directions to develop expertise in patient dosimetry and dose management. Publications creating awareness on cancer risks from CT in early part of the current century and over exposures in CT in 2008 brought radiation risks in public domain and created challenging situations for medical physicists. Increasing multiple exposures of individual patient and patient doses of few tens of mSv or exceeding 100 mSv are increasing the role of medical physicists. Expansion of usage of fluoroscopy in the hands of clinical professionals with hardly any training in radiation protection shall require further role for medical physicists. The increasing publications in journals, recent changes in Safety Standards, California law, all increase responsibilities of medical physicists in patient protection. Newer technological developments in dose efficiency and protective devices increase percentage of time devoted by medical physicists on radiation protection activities. Without radiation protection, the roles, responsibilities and day‐to‐day involvement of medical physicists in diagnostic radiology becomes questionable. In coming years either medical radiation protection may emerge as a specialty or medical physicists will have to keep major part of day‐to‐day work on radiation protection.

Learning Objectives:

To understand how radiation protection has been increasing its role in day‐to‐day activities of medical physicist

To be aware about international safety Standards, national and State regulations that require higher attention to radiation protection than in past

To be aware about possible emergence of medical radiation protection as a specialty and challenges for medical physicists.
MO‐E‐213‐03: Newer Radiation Protection Requirements in Last Decade
Authors: Clements J.
Published: June 2015

The focus of work of medical physicists in 1980's was on quality control and quality assurance. Radiation safety was important but was dominated by occupational radiation protection. A series of over exposures of patients in radiotherapy, nuclear medicine and observation of skin injuries among patients undergoing interventional procedures in 1990's started creating the need for focus on patient protection. It gave medical physicists new directions to develop expertise in patient dosimetry and dose management. Publications creating awareness on cancer risks from CT in early part of the current century and over exposures in CT in 2008 brought radiation risks in public domain and created challenging situations for medical physicists. Increasing multiple exposures of individual patient and patient doses of few tens of mSv or exceeding 100 mSv are increasing the role of medical physicists. Expansion of usage of fluoroscopy in the hands of clinical professionals with hardly any training in radiation protection shall require further role for medical physicists. The increasing publications in journals, recent changes in Safety Standards, California law, all increase responsibilities of medical physicists in patient protection. Newer technological developments in dose efficiency and protective devices increase percentage of time devoted by medical physicists on radiation protection activities. Without radiation protection, the roles, responsibilities and day‐to‐day involvement of medical physicists in diagnostic radiology becomes questionable. In coming years either medical radiation protection may emerge as a specialty or medical physicists will have to keep major part of day‐to‐day work on radiation protection.

Learning Objectives:

To understand how radiation protection has been increasing its role in day‐to‐day activities of medical physicist

To be aware about international safety Standards, national and State regulations that require higher attention to radiation protection than in past

To be aware about possible emergence of medical radiation protection as a specialty and challenges for medical physicists.
MO‐E‐BRD‐03
Authors: Libby B.
Published: June 2015

Is Non‐invasive Image‐Guided Breast Brachytherapy Good? – Jess Hiatt, MS

Non‐invasive Image‐Guided Breast Brachytherapy (NIBB) is an emerging therapy for breast boost treatments as well as Accelerated Partial Breast Irradiation (APBI) using HDR surface breast brachytherapy. NIBB allows for smaller treatment volumes while maintaining optimal target coverage. Considering the real‐time image‐guidance and immobilization provided by the NIBB modality, minimal margins around the target tissue are necessary.

Accelerated Partial Breast Irradiation in brachytherapy: is shorter better? ‐ Dorin Todor, PhD VCU

A review of balloon and strut devices will be provided together with the origins of APBI: the interstitial multi‐catheter implant. A dosimetric and radiobiological perspective will help point out the evolution in breast brachytherapy, both in terms of devices and the protocols/clinical trials under which these devices are used. Improvements in imaging, delivery modalities and convenience are among the factors driving the ultrashort fractionation schedules but our understanding of both local control and toxicities associated with various treatments is lagging. A comparison between various schedules, from a radiobiological perspective, will be given together with a critical analysis of the issues.

to review and understand the evolution and development of APBI using brachytherapy methods

to understand the basis and limitations of radio‐biological ‘equivalence’ between fractionation schedules

to review commonly used and proposed fractionation schedules

Intra‐operative breast brachytherapy: Is one stop shopping best?‐ Bruce Libby, PhD. University of Virginia

A review of intraoperative breast brachytherapy will be presented, including the Targit‐A and other trials that have used electronic brachytherapy. More modern approaches, in which the lumpectomy procedure is integrated into an APBI workflow, will also be discussed.

Learning Objectives:

To review past and current clinical trials for IORT

To discuss lumpectomy‐scan‐plan‐treat workflow for IORT
MO‐E‐BRB‐04: Real‐Time Exit‐Fluence Delivery Validation
Authors: Siebers J.
Published: June 2015

Recent high profile reports of technical failures and human errors causing severe radiation‐ induced injuries and deaths come in support of the sustained efforts to ensure patient safety in the delivery of radiation treatments. In addition, highly conformal radiation therapies and escalated fraction doses mandate increased and sustained accuracy of the entire radiotherapy process. Consequently, and as a Result of AAPM and ASTRO led efforts patient specific quality assurance for specialized radiation treatments such as IMRT, SRS/SBRT and Arc Therapy had become a three‐tier process: Pre‐treatment, during treatment, and post treatment patient specific QA. Traditional patient QA consists of pre‐treatment data transfer integrity dosimetric verifications and during‐treatment geometric verifications. However, as treatment adaptation becomes closer to deployment in the clinics, during treatment validation via exit detectors had become a realistic QA option, permitting plan assessment in near real time. Post‐treatment, machine logs allow comparisons of a range of mechanical parameters. A combination of these techniques could be used in evaluating inter‐fraction, and intra‐fraction delivery over a long time period such as an year, to evaluate the significant errors per site, per treatment technique. This type of data mining over longer periods of time provides the potential to recognize suboptimal radiation treatments, while allowing to identify systematic, possibly significant errors. This would allow creation of a data base of realized errors, small and large in dosimetry that could be for process or equipment improvement. This educational symposium will describe and review patient QA techniques, results, and strategies for patient specific quality assurance.

Learning Objectives:

review the goals of pre‐treatment QA for various specialized procedures

review methods and means for pre‐treatment QA, limitations and tolerances

review the scenarios where Varian/Tomo Log files could be used.

review error detection via log file analysis

Learn how exit detector signal recorded in log file could be used to improve patient safety

understand real‐time EPID‐based transmission dosimetry methods

understand the goals of real‐time delivery monitoring

CMS Innovation grant. Rapid response supportive and palliative care program for patients with advanced cancer, starts July, 2012; Accuray Inc. Exit detector based QA software evaluation, Sept, 2012‐Sept, 2013; ROI GRant from ASTRO “Safety and Quality: IMRT treatment delivery accuracy”
MO‐FG‐BRD‐00: Real‐Time Imaging and Tracking Techniques for Intrafractional Motion Management
Authors: Fahimian Benjamin
Published: June 2015

Intrafraction target motion is a prominent complicating factor in the accurate targeting of radiation within the body. Methods compensating for target motion during treatment, such as gating and dynamic tumor tracking, depend on the delineation of target location as a function of time during delivery. A variety of techniques for target localization have been explored and are under active development; these include beam‐level imaging of radio‐opaque fiducials, fiducial‐less tracking of anatomical landmarks, tracking of electromagnetic transponders, optical imaging of correlated surrogates, and volumetric imaging within treatment delivery. The Joint Imaging and Therapy Symposium will provide an overview of the techniques for real‐time imaging and tracking, with special focus on emerging modes of implementation across different modalities. In particular, the symposium will explore developments in 1) Beam‐level kilovoltage X‐ray imaging techniques, 2) EPID‐based megavoltage X‐ray tracking, 3) Dynamic tracking using electromagnetic transponders, and 4) MRI‐based soft‐tissue tracking during radiation delivery.

Learning Objectives:

Understand the fundamentals of real‐time imaging and tracking techniques

Learn about emerging techniques in the field of real‐time tracking

Distinguish between the advantages and disadvantages of different tracking modalities

Understand the role of real‐time tracking techniques within the clinical delivery work‐flow
MO‐FG‐BRD‐03: Real‐Time Imaging and Tracking Techniques for Intrafractional Motion Management: EM Tracking
Authors: Keall P.
Published: June 2015

Intrafraction target motion is a prominent complicating factor in the accurate targeting of radiation within the body. Methods compensating for target motion during treatment, such as gating and dynamic tumor tracking, depend on the delineation of target location as a function of time during delivery. A variety of techniques for target localization have been explored and are under active development; these include beam‐level imaging of radio‐opaque fiducials, fiducial‐less tracking of anatomical landmarks, tracking of electromagnetic transponders, optical imaging of correlated surrogates, and volumetric imaging within treatment delivery. The Joint Imaging and Therapy Symposium will provide an overview of the techniques for real‐time imaging and tracking, with special focus on emerging modes of implementation across different modalities. In particular, the symposium will explore developments in 1) Beam‐level kilovoltage X‐ray imaging techniques, 2) EPID‐based megavoltage X‐ray tracking, 3) Dynamic tracking using electromagnetic transponders, and 4) MRI‐based soft‐tissue tracking during radiation delivery.

Learning Objectives:

Understand the fundamentals of real‐time imaging and tracking techniques

Learn about emerging techniques in the field of real‐time tracking

Distinguish between the advantages and disadvantages of different tracking modalities

Understand the role of real‐time tracking techniques within the clinical delivery work‐flow
MO‐FG‐BRB‐00: The Global Cancer Challenge: What Can We Do?
Authors: Van Dyk Jacob
Published: June 2015

The global burden of cancer is growing rapidly with an estimated 15 million new cases per year worldwide in 2015, growing to 19 million by 2025 and 24 million by 2035. The largest component of this growth will occur in low‐to‐middle income countries (LMICs). About half of these cases will require radiation treatment. The gap for available cancer treatment, including radiation therapy, between high‐income countries (HICs) and LMICs is enormous. Accurate data and quantitative models to project the needs and the benefits of cancer treatment are a critical first step in closing the large cancer divide between LMICs and HICs. In this context, the Union for International Cancer Control (UICC) has developed a Global Task Force on Radiotherapy for Cancer Control (GTFRCC) with a charge to answer the question as to what it will take to close the gap between what exists today and reasonable access to radiation therapy globally by 2035 and what the potential clinical and economic benefits are for doing this. The Task Force has determined the projections of cancer incidence and the infrastructure required to provide access to radiation therapy globally. Furthermore it has shown that appropriate investment not only yields improved clinical outcomes for millions of patients but that it also provides an overall economic gain throughout all the income settings where this investment is made. This symposium will summarize the facets associated with this global cancer challenge by reviewing the cancer burden, looking at the requirements for radiation therapy, reviewing the benefits of providing such therapy both from a clinical and economic perspective and finally by looking at what approaches can be used to aid in the alleviation of this global cancer challenge. The speakers are world renowned experts in global public health issues (R. Atun), medical physics (D. Jaffray) and radiation oncology (N. Coleman).

Learning Objectives:

To describe the global cancer challenge and the corresponding potential benefits of addressing this challenge.

To describe what radiation therapy infrastructure, in terms of facilities, equipment and personnel, will be required to address this challenge.

To describe models of addressing personnel and infrastructure mobilization and capacity building within regions where significant cancer treatment disparities exist.
MO‐FG‐BRB‐02: Uniform Access to Radiation Therapy by 2035: Global Task Force on Radiotherapy for Cancer Control
Authors: Jaffray D.
Published: June 2015

The global burden of cancer is growing rapidly with an estimated 15 million new cases per year worldwide in 2015, growing to 19 million by 2025 and 24 million by 2035. The largest component of this growth will occur in low‐to‐middle income countries (LMICs). About half of these cases will require radiation treatment. The gap for available cancer treatment, including radiation therapy, between high‐income countries (HICs) and LMICs is enormous. Accurate data and quantitative models to project the needs and the benefits of cancer treatment are a critical first step in closing the large cancer divide between LMICs and HICs. In this context, the Union for International Cancer Control (UICC) has developed a Global Task Force on Radiotherapy for Cancer Control (GTFRCC) with a charge to answer the question as to what it will take to close the gap between what exists today and reasonable access to radiation therapy globally by 2035 and what the potential clinical and economic benefits are for doing this. The Task Force has determined the projections of cancer incidence and the infrastructure required to provide access to radiation therapy globally. Furthermore it has shown that appropriate investment not only yields improved clinical outcomes for millions of patients but that it also provides an overall economic gain throughout all the income settings where this investment is made. This symposium will summarize the facets associated with this global cancer challenge by reviewing the cancer burden, looking at the requirements for radiation therapy, reviewing the benefits of providing such therapy both from a clinical and economic perspective and finally by looking at what approaches can be used to aid in the alleviation of this global cancer challenge. The speakers are world renowned experts in global public health issues (R. Atun), medical physics (D. Jaffray) and radiation oncology (N. Coleman).

Learning Objectives:

To describe the global cancer challenge and the corresponding potential benefits of addressing this challenge.

To describe what radiation therapy infrastructure, in terms of facilities, equipment and personnel, will be required to address this challenge.

To describe models of addressing personnel and infrastructure mobilization and capacity building within regions where significant cancer treatment disparities exist.
MO‐FG‐BRA‐03: A Monte‐Carlo Study of Cellular Dosimetry of Radioactive Gold‐Palladium Nanoparticles
Authors: Ma Y , Michaud F , Fortin M , Beaulieu L
Published: June 2015

Purpose:

Radioactive gold‐palladium nanoparticles (1⁰3Pd:Pd@Au NPs) are being developed for prostate cancer brachytherapy. Photons emitted by the radioisotope palladium (photon energy: 20.1 and 23.0 keV), interacting with gold‐coating of NPs, lead to enhanced energy distribution in nucleus. Here, a simple cellular model was studied using detailed track‐structure method.

Methods:

Geant4‐DNA was used with auger electrons enabled. Biological cell was modeled as a sphere of radius r=5 µm that were immersed in a fluid containing large number of NPs at different concentrations (S=1, 2.15, 5.1, 17.2 mg‐Au/g‐H2O). Nucleus was modeled as a concentric sphere (r=3µm). Thickness of gold‐coating on 1⁰3Pd core was 15nm, 20nm and 25nm, respectively. A scenario of NP diffusion was investigated, where S=5.1 mg‐Au/g‐H2O outside cell and S=1 mg‐Au/g‐H2O in cytoplasm. 101⁰ 1⁰3Pd decays were simulated for each combination of NP concentration and gold‐coating.

Results:

A uniform increase in energy deposition (Edep) is observed in cell nucleus and the energy enhancement ratio (EER) is 1.16, 1.22 and 1.3 for 15nm, 20nm and 25nm of gold ‐coatings, respectively. Edep at the center of nucleus is increased by a factor of 1.47, 2.51 and 5.54 when the NP concentration in the cytoplasm increases from 1 mg‐Au/g‐H2O to 2.15, 5.10 and 17.2 mg‐Au/g‐H2O, respectively. When NPs diffuse into cytoplasm, the mean value of Edep in nucleus increases from 0.42 to 1.13 MeV per 10⁹ decays (GBq‐Second) of 1⁰3Pd and the maximum value increases from 0.54 to 2.5 MeV per GBq‐Second.

Conclusion:

These results suggest that 1⁰3Pd:Pd@Au NPs constitute a promising nanotherapeutic agent. Ongoing studies use transmission electron microscopy (TEM) images of prostate cancer.
MO‐FG‐BRA‐05: Next Generation Radiotherapy Biomaterials Loaded With Gold Nanoparticles
Authors: Cifter G , Sajo E , Korideck H , Kumar R , Sridhar S , Cormack R , Makrigiorgos G , Ngwa W
Published: June 2015

Purpose:

It has been proposed that routinely used inert radiotherapy (RT) biomaterials (e.g. fiducials, spacers) can be upgraded to smarter ones by coating/loading them with radiosensitizing gold nanoparticles (GNPs), for sustained in‐situ release after implantation to enhance RT. In this work, we developed prototypes of such RT biomaterials and investigated the sustained release of GNPs from the biomaterials as a function of design parameters.

Methods:

Prototype smart biomaterials were produced by incorporating the GNPs in poly(D,L‐lactide‐co‐glycolide) (PLGA) polymer millirods during the gel phase of production. For comparison, commercially available spacers were also coated with a polymer film loaded with fluorescent GNP. Optical/spectroscopy methods were used to monitor in vitro release of GNPs over time as a function of different design parameters: polymer weighting, type, and initial (loading) GNP concentrations. Inductively coupled plasma mass spectrometry was employed to verify GNP release.

Results:

Results showed that gold nanoparticles could be successfully loaded in the new RT biomaterial prototypes. Burst release of GNPs could be achieved within 1 to 25 days depending on the preparation approach. Burst release was followed by sustained release profile over time. The amount of released GNP increased with increasing loading concentration as expected. The release profiles could also be customized as a function of polymer weighting, or preparation approaches.

Conclusion:

Considered together, our results highlight potential for the development of next generation RT biomaterials loaded with GNPs customizable to different RT schedules. Such biomaterials could be employed as needed instead of currently used inert spacers/fiducials at no additional inconvenience to patients, to enhance RT.
MO‐FG‐BRA‐06: Material Optimisation for Nanoparticle‐Sensitized Radiotherapy
Authors: McMahon S , Paganetti H , Prise K
Published: June 2015

Purpose:

To evaluate the potential applications of nanoparticles of different elemental compositions as X‐ray radiosensitizers.

Methods:

Geant4 Monte Carlo models were used to model the interactions of 10 nm radius nanoparticles of elements ranging from silicon to mercury with either monoenergetic keV X‐rays or a 6 MV Linac spectrum. Secondary electron spectra emitted from nanoparticles and resulting radial doses were calculated. Potential biological impacts were evaluated through the use of the Local Effect Model.

Results:

For keV radiation, fluoresence photons and energetic photoelectrons deposit the majority of energy emitted by nanoparticles, over long ranges. However, short‐range energy deposition is dominated by Auger electrons. While total energy deposition increases with atomic number, short‐range energy deposition has a more complex behaviour, with local maxima around germanium (Z=32) and gadolinium (Z=64). For megavoltage radiation, Compton electrons deposit the majority of energy, but short‐ range depositions are dominated by interactions with secondary electrons. As a Result, energy deposition following ionising events following Linac irradiation is largely independent of atomic number.When analysed through the Local Effect Model, these effects translate into significant variations in predicted cell killing with atomic number for keV exposures, but comparatively limited effects for megavoltage exposures.

Conclusions:

Although heavier elements typically lead to greater increases in dose within target volumes, on the nanometre scale effects are typically dominated by low‐energy secondary electrons, whose distribution has a complex relationship with both nanoparticle composition and beam energy.These results suggest that maximum radiosensitization may not necessarily be achieved through maximizing atomic number, but rather a balance between overall interaction cross‐section and local dose distribution. The different behaviours seen when comparing keV and MV behaviours may also provide future mechanisms for separating physical and biological mechanisms of nanoparticle sensitisation, a key step in their development as a potential therapeutic agent.
MO‐FG‐BRA‐08: A Preliminary Study of Gold Nanoparticles Enhanced Diffuse Optical Tomography
Authors: Xu K , Dogan N , Yang Y
Published: June 2015

Purpose:

To develop an imaging method by using gold nanoparticles (GNP) to enhance diffuse optical tomography (DOT) for better tumor detection.

Methods:

Experiments were performed on a tissue‐simulating cylindrical optical phantom (30mm diameter, 60mm length). The GNP used are gold nanorods (10nm diameter, 44nm length) with peak light absorption at 840nm. 0.085ml GNP colloid of 96nM concentration was loaded into a 6mm diameter cylindrical hole in the phantom. An 856nm laser beam (14mW) was used as light source to irradiate the phantom at multiple locations through rotating and elevating the phantom. A CCD camera captured the light transmission through the phantom for each irradiation with total 40 projections (8 rotation angles in 45degree steps and 5 elevations with 3mm apart). Cone beam CT of the phantom was used to generate the three‐dimensional mesh for DOT reconstruction and to identify the true location of the GNP volume. A forward simulation was performed with known phantom optical properties to establish a relationship between the absorption coefficient and concentration of the GNP by matching the simulated and measured transmission. DOT image reconstruction was performed to restore the GNP within the phantom. In addition, a region‐constrained reconstruction was performed by confining the solutions within the GNP volume detected from CT.

Results:

The position of the GNP volume was reconstructed with <2mm error. The reconstructed average GNP concentration within an identical volume was 104nM, 8% difference from the truth. When the CT was used as “a priori”, the reconstructed average GNP concentration was 239nM, about 2.5 times of the true concentration.

Conclusion:

This study is the first to demonstrate GNP enhanced DOT with phantom imaging. The GNP can be differentiated from their surrounding background. However, the reconstruction methods needs to be improved for better spatial and quantification accuracy.
MO‐FG‐303‐03: Demonstration of Universal Knowledge‐Based 3D Dose Prediction
Authors: Shiraishi S , Moore K L
Published: June 2015

Purpose:

To demonstrate a knowledge‐based 3D dose prediction methodology that can accurately predict achievable radiotherapy distributions.

Methods:

Using previously treated plans as input, an artificial neural network (ANN) was trained to predict 3D dose distributions based on 14 patient‐specific anatomical parameters including the distance (r) to planning target volume (PTV) boundary, organ‐at‐risk (OAR) boundary distances, and angular position ( θ,φ). 23 prostate and 49 stereotactic radiosurgery (SRS) cases with ≥1 nearby OARs were studied. All were planned with volumetric‐modulated arc therapy (VMAT) to prescription doses of 81Gy for prostate and 12–30Gy for SRS. Site‐specific ANNs were trained using all prostate 23 plans and using a 24 randomly‐selected subset for the SRS model. The remaining 25 SRS plans were used to validate the model. To quantify predictive accuracy, the dose difference between the clinical plan and prediction were calculated on a voxel‐by‐voxel basis δD(r,θ,φ)=Dclin(r,θ,φ)‐Dpred(r, θ,φ). Grouping voxels by boundary distance, the mean <δ Dr>=(1/N)Σ _θ,φ D(r,θ,φ) and inter‐quartile range (IQR) quantified the accuracy of this method for deriving DVH estimations. The standard deviation (σ) of δ D quantified the 3D dose prediction error on a voxel‐by‐voxel basis.

Results:

The ANNs were highly accurate in predictive ability for both prostate and SRS plans. For prostate, <δDr> ranged from −0.8% to +0.6% (max IQR=3.8%) over r=0–32mm, while 3D dose prediction accuracy averaged from σ=5–8% across the same range. For SRS, from r=0–34mm the training set <δDr> ranged from −3.7% to +1.5% (max IQR=4.4%) while the validation set <δDr> ranged from −2.2% to +5.8% (max IQR=5.3%). 3D dose prediction accuracy averaged σ=2.5% for the training set and σ=4.0% over the same interval.

Conclusion:

The study demonstrates this technique's ability to predict achievable 3D dose distributions for VMAT SRS and prostate. Future investigations will attempt to separate and quantify modeling error and plan quality variations in the statistical noise.

Research funding support from Varian Medical Systems
MO‐FG‐303‐05: A Feasibility Study of Using a Cherenkov Detector Material with the Prompt Gamma Range Verification Technique in Proton Therapy
Authors: Lau A , Ahmad S , Chen Y
Published: June 2015

Purpose:

To simulate the feasibility of a Cherenkov glass material for the determination of the penetration depth of therapeutic proton beams in water.

Methods:

Proton pencil beams of various energies incident onto a water phantom with dimensions of 5 × 5 × 30 cm3 were used for simulation with the Geant4 toolkit. The model used standard electromagnetic packages, packages based on binary‐cascade nuclear model, several decay modules (G4Decay, G4DecayPhysics, and G4RadioactiveDecayPhysics), and optical photon components (G4OpticalPhysics). A Cherenkov glass material was modeled as the detector medium (7.2 g of In2O3 + 90 g cladding, density of 2.82 g/cm3, Zeff = 33.7, index of refraction n(600 nm) = 1.56, and energy threshold of production Eth = 156 keV ). The emitted secondary particles are analyzed characterizing their timing, energy, and angular distributions. A feasibility analysis was conducted for a simplistic detector system using this material to locate the position of the Bragg Peak.

Results:

The escaping neutrons have energies ranging from thermal to the incident proton energy and the escaping photons have energies >10 MeV. Photon peaks between 4 and 6 MeV were attributed to originate from direct proton interactions with 12C (∼ 4.4 MeV) and 1⁶O (∼ 6 MeV), respectively. The escaping photons are emitted isotropically, while low (≤10 MeV) and high (>10 MeV) neutrons are isotropic and forward‐directional, respectively. The emissions of photons are categorized into prompt (∼ns) and delayed (∼min) where the prompt photons include the 4.4 and 6 MeV. The Cherenkov material had on average <2% of neutron interactions while LYSO and BGO scintillators had a minimum of ∼50%. Our simplistic detector system was capable of discerning Bragg Peak locations using a timing discrimination of ∼50 ns.

Conclusion:

We investigate the viability of using the Cherenkov material for MeV photon detection medium for the prompt gamma technique.
MO‐FG‐303‐06: Evaluation of the Performance of Very High‐Energy Electron (VHEE) Beams in Radiotherapy: Five Clinical Cases
Authors: Palma B , Bazalova‐Carter M , Hardemark B , Hynning E , Qu B , Loo B , Maxim P
Published: June 2015

Purpose:

To evaluate the performance of 100–120 MeV very‐high energy electron (VHEE) scanning pencil beams to radiotherapy by means of Monte Carlo (MC) simulations.

Methods:

We selected five clinical cases with target sizes of 1.2 cm3 to 990.4 cm3. We calculated VHEE treatment plans using the MC EGSnrc code implemented in a MATLAB‐based graphical user interface developed by our group. We generated phase space data for beam energies: 100 and 120 MeV and pencil beam spot sizes of 1, 3, and 5 mm at FWHM. The number of equidistant beams considered in this work was 16 or 32. Dose was calculated and then imported into a research version of RayStation where treatment plan optimization was performed. We compared the VHEE plans with the clinically delivered volumetric modulated arc therapy (VMAT) plan to evaluate VHEE plans performance.

Results:

VHEE plans provided the same PTV coverage and dose homogeneity than VMAT plans for all the cases. In average, the mean dose to organs at risk (OARs) was 24% lower for the VHEE plans. The structures that benefited the most from using VHEE were: large bowel for the esophagus case, chest wall for the liver case, brainstem for the acoustic case, carina for the lung case, and genitalia for the anal case, with 23.7–34.6% lower dose. VHEE dose distributions were more conformal than VMAT solution as confirmed by conformity indices CI100 and CI50. Integral dose to the body was in average 19.6% (9.2%–36.5%) lower for the VHEE plans.

Conclusion:

We have shown that VHEE plans resulted in similar or superior dose distributions compared to clinical VMAT plans for five different cases and a wide range of target volumes, including a case with a small target (1.2 cm3), which represents a challenge for VMAT planning and might require the use of more complex non‐coplanar VMAT plans.

B Palma: None. M Bazalova: None. B Hardemark: Employee, RaySearch Laboratories AB. E Hynning: Employee, RaySearch Laboratories AB. B Qu: None. B Loo Jr.: Research support, RaySearch, Varian. P Maxim: Research support, RaySearch, Varian
MO‐FG‐303‐07: Quality Assurance of OAR Segmentation Using Machine Learning And Statistical Shape Models
Authors: Schreibmann E , Elder E
Published: June 2015

Purpose:

Automating the quality assurance of OAR segmentations is technically a challenging task due to the natural anatomical variations that cannot be easily quantified by computer algorithms. We report on QA method for OAR segmentations that uses recent advances in machine learning to automate the currently‐used manual interpretation of segmentation quality.

Materials and Methods:

The approach relies on building a statistical model of an organ's shapes and variation across patients from a set of high‐quality contours representative for the anatomy. When presented with a new OAR segmentation for evaluation, the QA procedure fits the shape to the statistical model to mark outlier contours and suggest a correction for their location based on the statistics inferred from the training datasets. Technically, the statistical model of OAR variation is build using a probabilistic PCA model where deformations between learning shapes are modeled as a Gaussian process to create a general non‐parametric model that is flexible in capturing inter‐patient variations.

Results:

The algorithm was tested in clinical practice by creating custom software that intercepts DICOM RT segmentation files send to the treatment planning system, verifies them against the statistical model, and presents to original and corrected segmentations side‐by‐side in the treatment planning for evaluating changes suggested by the QA procedure. Segmentation quality is quantified through the Dice and Hausdorff distance between the initial and corrected shape.

Conclusion:

Abnormalities in critical structures delineation can be quantified by a shape model derived from a database of verified segmentation to create a software tool that detects and quantifies point‐by point variations from a normal segmentation. The approach was used to verify OAR segmentation and streamline clinical practice.
MO‐FG‐204‐02: Reference Image Selection in the Presence of Multiple Scan Realizations
Authors: Ruan D , Dou T , Thomas D , Low D
Published: June 2015

Purpose:

Fusing information from multiple correlated realizations (e.g., 4DCT) can improve image quality. This process often involves ill‐conditioned and asymmetric nonlinear registration and the proper selection of a reference image is important. This work proposes to examine post‐registration variation indirectly for such selection, and develops further insights to reduce the number of cross‐registrations needed.

Methods:

We consider each individual scan as a noisy point in the vicinity of an image manifold, related by motion. Nonrigid registration “transports” a scan along the manifold to the reference neighborhood, and the residual is a surrogate for local variation. To test this conjecture, 10 thoracic scans from the same session were reconstructed from a recently developed low‐dose helical 4DCT protocol. Pairwise registration was repeated bi‐directionally (81 times) and fusion was performed with each candidate reference. The fused image quality was assessed with SNR and CNR. Registration residuals in SSD, harmonic energy, and deformation Jacobian behavior were examined. The semi‐symmetry is further utilized to reduce the number of registration needed.

Results:

The comparison of image quality between single image and fused ones identified reduction of local intensity variance as the major contributor of image quality, boosting SNR and CNR by 5 to 7 folds. This observation further suggests the criticality of good agreement across post‐registration images. Triangle inequality on the SSD metric provides a proficient upper‐bound and surrogate on such disagreement. Empirical observation also confirms that fused images with high residual SSD have lower SNR and CNR than the ones with low or intermediate SSDs. Registration SSD is structurally close enough to symmetry for reduced computation.

Conclusion:

Registration residual is shown to be a good predictor of post‐fusion image quality and can be used to identify good reference centers. Semi‐symmetry of the registration residual further reduces computation cost.

Supported by in part by NIH R01 CA096679.
MO‐FG‐204‐03: Using Edge‐Preserving Algorithm for Significantly Improved Image‐Domain Material Decomposition in Dual Energy CT
Authors: Zhao W , Niu T , Xing L , Xiong G , Elmore K , Zhu J , Wang L , Min J
Published: June 2015

Purpose:

To significantly improve dual energy CT (DECT) imaging by establishing a new theoretical framework of image‐domain material decomposition with incorporation of edge‐preserving techniques.

Methods:

The proposed algorithm, HYPR‐NLM, combines the edge‐preserving non‐local mean filter (NLM) with the HYPR‐LR (Local HighlY constrained backPRojection Reconstruction) framework. Image denoising using HYPR‐LR framework depends on the noise level of the composite image which is the average of the different energy images. For DECT, the composite image is the average of high‐ and low‐energy images. To further reduce noise, one may want to increase the window size of the filter of the HYPR‐LR, leading resolution degradation. By incorporating the NLM filtering and the HYPR‐LR framework, HYPR‐NLM reduces the boost material decomposition noise using energy information redundancies as well as the non‐local mean. We demonstrate the noise reduction and resolution preservation of the algorithm with both iodine concentration numerical phantom and clinical patient data by comparing the HYPR‐NLM algorithm to the direct matrix inversion, HYPR‐LR and iterative image‐domain material decomposition (Iter‐DECT).

Results:

The results show iterative material decomposition method reduces noise to the lowest level and provides improved DECT images. HYPR‐NLM significantly reduces noise while preserving the accuracy of quantitative measurement and resolution. For the iodine concentration numerical phantom, the averaged noise levels are about 2.0, 0.7, 0.2 and 0.4 for direct inversion, HYPR‐LR, Iter‐ DECT and HYPR‐NLM, respectively. For the patient data, the noise levels of the water images are about 0.36, 0.16, 0.12 and 0.13 for direct inversion, HYPR‐LR, Iter‐DECT and HYPR‐NLM, respectively. Difference images of both HYPR‐LR and Iter‐DECT show edge effect, while no significant edge effect is shown for HYPR‐NLM, suggesting spatial resolution is well preserved for HYPR‐NLM.

Conclusion:

HYPR‐NLM provides an effective way to reduce the generic magnified image noise of dual–energy material decomposition while preserving resolution.

This work is supported in part by NIH grants 7R01HL111141 and 1R01‐EB016777. This work is also supported by the Natural Science Foundation of China (NSFC Grant No. 81201091), Fundamental Research Funds for the Central Universities in China, and Fund Project for Excellent Abroad Scholar Personnel in Science and Technology.
MO‐FG‐204‐04: How Iterative Reconstruction Algorithms Affect the NPS of CT Images
Authors: Li G , Liu X , Dodge C , Jensen C , Rong J
Published: June 2015

Purpose:

To evaluate how the third generation model based iterative reconstruction (MBIR) compares with filtered back‐projection (FBP), adaptive statistical iterative reconstruction (ASiR), and the second generation MBIR based on noise power spectrum (NPS) analysis over a wide range of clinically applicable dose levels.

Methods:

The Catphan 600 CTP515 module, surrounded by an oval, fat‐equivalent ring to mimic patient size/shape, was scanned on a GE HD750 CT scanner at 1, 2, 3, 6, 12 and 19mGy CTDIvol levels with typical patient scan parameters: 120kVp, 0.8s, 40mm beam width, large SFOV, 0.984 pitch and reconstructed thickness 2.5mm (VEO3.0: Abd/Pelvis with Texture and NR05). At each CTDIvol level, 10 repeated scans were acquired for achieving sufficient data sampling. The images were reconstructed using Standard kernel with FBP; 20%, 40% and 70% ASiR; and two versions of MBIR (VEO2.0 and 3.0). For evaluating the effect of the ROI spatial location to the Result of NPS, 4 ROI groups were categorized based on their distances from the center of the phantom.

Results:

VEO3.0 performed inferiorly comparing to VEO2.0 over all dose levels. On the other hand, at low dose levels (less than 3 mGy), it clearly outperformed ASiR and FBP, in NPS values. Therefore, the lower the dose level, the relative performance of MBIR improves. However, the shapes of the NPS show substantial differences in horizontal and vertical sampling dimensions. These differences may determine the characteristics of the noise/texture features in images, and hence, play an important role in image interpretation.

Conclusion:

The third generation MBIR did not improve over the second generation MBIR in term of NPS analysis. The overall performance of both versions of MBIR improved as compared to other reconstruction algorithms when dose was reduced. The shapes of the NPS curves provided additional value for future characterization of the image noise/texture features.
MO‐FG‐204‐08: Optimization‐Based Image Reconstruction From Unevenly Distributed Sparse Projection Views
Authors: Xie Huiqiao , Niu Tianye , Ren Yi , Yang Yi , Tang Xiangyang
Published: June 2015

Purpose:

Optimization‐based reconstruction has been proposed and investigated for reconstructing CT images from sparse views, as such the radiation dose can be substantially reduced while maintaining acceptable image quality. The investigation has so far focused on reconstruction from evenly distributed sparse views. Recognizing the clinical situations wherein only unevenly sparse views are available, e.g., image guided radiation therapy, CT perfusion and multi‐cycle cardiovascular imaging, we investigate the performance of optimization‐based image reconstruction from unevenly sparse projection views in this work.

Methods:

The investigation is carried out using the FORBILD and an anthropomorphic head phantoms. In the study, 82 views, which are evenly sorted out from a full (360°) axial CT scan consisting of 984 views, form sub‐scan I. Another 82 views are sorted out in a similar manner to form sub‐scan II. As such, a CT scan with sparse (164) views at 1:6 ratio are formed. By shifting the two sub‐scans relatively in view angulation, a CT scan with unevenly distributed sparse (164) views at 1:6 ratio are formed. An optimization‐based method is implemented to reconstruct images from the unevenly distributed views. By taking the FBP reconstruction from the full scan (984 views) as the reference, the root mean square (RMS) between the reference and the optimization‐based reconstruction is used to evaluate the performance quantitatively.

Results:

In visual inspection, the optimization‐based method outperforms the FBP substantially in the reconstruction from unevenly distributed, which are quantitatively verified by the RMS gauged globally and in ROIs in both the FORBILD and anthropomorphic head phantoms. The RMS increases with increasing severity in the uneven angular distribution, especially in the case of anthropomorphic head phantom.

Conclusion:

The optimization‐based image reconstruction can save radiation dose up to 12‐fold while providing acceptable image quality for advanced clinical applications wherein only unevenly distributed sparse views are available.

Research Grants: W81XWH‐12‐1‐0138 (DoD), Sinovision Technologies.
MO‐FG‐207‐02: Technological Advances and Challenges: Experience with Time‐Of‐Flight PET Combined with 3‐Tesla MRI
Authors: Jansen F.
Published: June 2015

The use of integrated PET/MRI systems in clinical applications can best benefit from understanding their technological advances and limitations. The currently available clinical PET/MRI systems have their own characteristics. Thorough analyses of existing technical data and evaluation of necessary performance metrics for quality assurances could be conducted to optimize application‐specific PET/MRI protocols. This Symposium will focus on technical advances and limitations of clinical PET/MRI systems, and how this exciting imaging modality can be utilized in applications that can benefit from both PET and MRI.

Learning Objectives:

To understand the technological advances of clinical PET/MRI systems

To correctly identify clinical applications that can benefit from PET/MRI

To understand ongoing work to further improve the current PET/MRI technology

Floris Jansen is a GE Healthcare employee.