bluuebunny/crossref_metadata_2025 huggingface dataset:
TU‐F‐201‐01: General Aspects of Radiochromic Film Dosimetry
Authors: Niroomand‐Rad A.
Published: June 2015

Since the introduction of radiochromic films (RCF) for radiation dosimetry, the scope of RCF dosimetry has expanded steadily to include many medical applications, such as radiation therapy and diagnostic radiology. The AAPM Task Group (TG) 55 published a report on the recommendations for RCF dosimetry in 1998. As the technology is advancing rapidly, and its routine clinical use is expanding, TG 235 has been formed to provide an update to TG‐55 on radiochromic film dosimetry. RCF dosimetry applications in clinical radiotherapy have become even more widespread, expanding from primarily brachytherapy and radiosurgery applications, and gravitating towards (but not limited to) external beam therapy (photon, electron and protons), such as quality assurance for IMRT, VMAT, Tomotherapy, SRS/SRT, and SBRT. In addition, RCF applications now extend to measurements of radiation dose in particle beams and patients undergoing medical exams, especially fluoroscopically guided interventional procedures and CT. The densitometers/scanners used for RCF dosimetry have also evolved from the He‐Ne laser scanner to CCD‐based scanners, including roller‐based scanner, light box‐based digital camera, and flatbed color scanner. More recently, multichannel RCF dosimetry introduced a new paradigm for external beam dose QA for its high accuracy and efficiency. This course covers in detail the recent advancements in RCF dosimetry.

Learning Objectives:

Introduce the paradigm shift on multichannel film dosimetry

Outline the procedures to achieve accurate dosimetry with a RCF dosimetry system

Provide comprehensive guidelines on RCF dosimetry for various clinical applications

One of the speakers has a research agreement from Ashland Inc., the manufacturer of Gafchromic film.
TU‐F‐201‐02: Applications in SRS, SBRT, IMRT, VMAT, and KV Imaging
Authors: Chiu‐Tsao S.
Published: June 2015

Since the introduction of radiochromic films (RCF) for radiation dosimetry, the scope of RCF dosimetry has expanded steadily to include many medical applications, such as radiation therapy and diagnostic radiology. The AAPM Task Group (TG) 55 published a report on the recommendations for RCF dosimetry in 1998. As the technology is advancing rapidly, and its routine clinical use is expanding, TG 235 has been formed to provide an update to TG‐55 on radiochromic film dosimetry. RCF dosimetry applications in clinical radiotherapy have become even more widespread, expanding from primarily brachytherapy and radiosurgery applications, and gravitating towards (but not limited to) external beam therapy (photon, electron and protons), such as quality assurance for IMRT, VMAT, Tomotherapy, SRS/SRT, and SBRT. In addition, RCF applications now extend to measurements of radiation dose in particle beams and patients undergoing medical exams, especially fluoroscopically guided interventional procedures and CT. The densitometers/scanners used for RCF dosimetry have also evolved from the He‐Ne laser scanner to CCD‐based scanners, including roller‐based scanner, light box‐based digital camera, and flatbed color scanner. More recently, multichannel RCF dosimetry introduced a new paradigm for external beam dose QA for its high accuracy and efficiency. This course covers in detail the recent advancements in RCF dosimetry.

Learning Objectives:

Introduce the paradigm shift on multichannel film dosimetry

Outline the procedures to achieve accurate dosimetry with a RCF dosimetry system

Provide comprehensive guidelines on RCF dosimetry for various clinical applications

One of the speakers has a research agreement from Ashland Inc., the manufacturer of Gafchromic film.
TU‐F‐201‐03: Applications in Brachytherapy
Authors: Trichter S.
Published: June 2015

Since the introduction of radiochromic films (RCF) for radiation dosimetry, the scope of RCF dosimetry has expanded steadily to include many medical applications, such as radiation therapy and diagnostic radiology. The AAPM Task Group (TG) 55 published a report on the recommendations for RCF dosimetry in 1998. As the technology is advancing rapidly, and its routine clinical use is expanding, TG 235 has been formed to provide an update to TG‐55 on radiochromic film dosimetry. RCF dosimetry applications in clinical radiotherapy have become even more widespread, expanding from primarily brachytherapy and radiosurgery applications, and gravitating towards (but not limited to) external beam therapy (photon, electron and protons), such as quality assurance for IMRT, VMAT, Tomotherapy, SRS/SRT, and SBRT. In addition, RCF applications now extend to measurements of radiation dose in particle beams and patients undergoing medical exams, especially fluoroscopically guided interventional procedures and CT. The densitometers/scanners used for RCF dosimetry have also evolved from the He‐Ne laser scanner to CCD‐based scanners, including roller‐based scanner, light box‐based digital camera, and flatbed color scanner. More recently, multichannel RCF dosimetry introduced a new paradigm for external beam dose QA for its high accuracy and efficiency. This course covers in detail the recent advancements in RCF dosimetry.

Learning Objectives:

Introduce the paradigm shift on multichannel film dosimetry

Outline the procedures to achieve accurate dosimetry with a RCF dosimetry system

Provide comprehensive guidelines on RCF dosimetry for various clinical applications

One of the speakers has a research agreement from Ashland Inc., the manufacturer of Gafchromic film.
TU‐F‐201‐04: Applications in Small Fields and Proton Beams
Authors: Das I.
Published: June 2015

Since the introduction of radiochromic films (RCF) for radiation dosimetry, the scope of RCF dosimetry has expanded steadily to include many medical applications, such as radiation therapy and diagnostic radiology. The AAPM Task Group (TG) 55 published a report on the recommendations for RCF dosimetry in 1998. As the technology is advancing rapidly, and its routine clinical use is expanding, TG 235 has been formed to provide an update to TG‐55 on radiochromic film dosimetry. RCF dosimetry applications in clinical radiotherapy have become even more widespread, expanding from primarily brachytherapy and radiosurgery applications, and gravitating towards (but not limited to) external beam therapy (photon, electron and protons), such as quality assurance for IMRT, VMAT, Tomotherapy, SRS/SRT, and SBRT. In addition, RCF applications now extend to measurements of radiation dose in particle beams and patients undergoing medical exams, especially fluoroscopically guided interventional procedures and CT. The densitometers/scanners used for RCF dosimetry have also evolved from the He‐Ne laser scanner to CCD‐based scanners, including roller‐based scanner, light box‐based digital camera, and flatbed color scanner. More recently, multichannel RCF dosimetry introduced a new paradigm for external beam dose QA for its high accuracy and efficiency. This course covers in detail the recent advancements in RCF dosimetry.

Learning Objectives:

Introduce the paradigm shift on multichannel film dosimetry

Outline the procedures to achieve accurate dosimetry with a RCF dosimetry system

Provide comprehensive guidelines on RCF dosimetry for various clinical applications

One of the speakers has a research agreement from Ashland Inc., the manufacturer of Gafchromic film.
TU‐G‐213‐02: IEC Subcommittee 62B (Diagnostic Imaging Equipment): Recent and Active Projects
Authors: Supanich M.
Published: June 2015

The International Electrotechnical Commission (IEC) writes standards that manufacturers of electrical equipment must comply with. Medical electrical equipment, such as medical imaging, radiation therapy, and radiation dosimetry devices, fall under Technical Committee 62. Of particular interest to medical physicists are the standards developed within Subcommittees (SC) 62B, which addresses diagnostic radiological imaging equipment, and 62C, which addresses equipment for radiation therapy, nuclear medicine and dosimetry. For example, a Working Group of SC 62B is responsible for safety and quality assurance standards for CT scanners and a Working Group of SC 62C is responsible for standards that set requirements for dosimetric safety and accuracy of linacs and proton accelerators. IEC standards thus have an impact on every aspect of a medical physicist's job, including equipment testing, shielding design, room layout, and workflow. Consequently, it is imperative that US medical physicists know about existing standards, as well as have input on those under development or undergoing revision.

The structure of the IEC and current standards development work will be described in detail. The presentation will explain how US medical physicists can learn about IEC standards and contribute to their development.

Learning Objectives:

Learn about the structure of the IEC and the influence that IEC standards have on the design of equipment for radiology and radiation therapy.

Learn about the mechanisms by which the US participates in the development and revision of standards.

Understand the specific requirements of several standards having direct relevance to diagnostic and radiation therapy physicists.
TU‐G‐BRD‐03: IMRT Dosimetry Differences in An Institution with Community and Academic Model
Authors: Srivastava S , Andersen A , Cheng C , Das I
Published: June 2015

Purpose:

Radiation outcome among institutions can be interpreted meaningfully if the dose delivery and prescription to the target volume is documented accurately and consistently. ICRU‐83 recommended specific guidelines in IMRT for target volume definitions and dose reporting. This retrospective study evaluates the pattern of IMRT dose prescription and recording in an academic institution (AI) and a community hospital (CH) models in a single institution with reference to ICRU‐83 recommendation.

Materials & Methods:

Dosimetric information of 625 (500 from academic and 125 from community) patients treated with IMRT was collected retrospectively from the AI and a CH. The dose‐volume histogram (DVH) for the target volume of each patient was extracted. Standard dose parameters such as D2, D50, D95, D98, D100, as well as the homogeneity index (HI) defined as (D2‐D98)/D50 and monitor units (MUs) were collected.

Results:

Significant dosimetric variations were observed in disease sites and between AI and CH. The variation in the mean value of D95 for AI is 98.48±4.12 and for CH is 96.41±4.13. A similar pattern was noticed for D50 (104.18±6.04 for AI and 101.05±3.49 for CH). Thus, nearly 95% of patients received dosage higher than 100% to the site viewed by D50 and varied between AI and CH models. The average variation of HI is found to be 0.12±0.08 and 0.11±0.08 for AI and CH model, showing better IMRT treatment plans for academic model compared to community.

Conclusion:

Even with the implementation of ICRU‐83 guidelines, there is a large variation in dose prescription and delivery in IMRT. The variation is institution and site specific. For any meaningful comparison of the IMRT outcome, strict guidelines for dose reporting should be maintained in every institution.
TU‐G‐BRD‐06: The Imaging and Radiation Oncology Core Houston (IROC Houston) QA Center International Activities Outside North America
Authors: Followill D , Kry S , Molineu A , Lowenstein J , Alvarez P , Taylor P , Nguyen H , Hernandez N , Lujano C , Nguyen T , Keith T , Roll J , Tailor A
Published: June 2015

Purpose:

To describe the extent of IROC Houston's (formerly the RPC) QA activities and audit results for radiotherapy institutions outside of North America (NA).

Methods:

The IROC Houston's QA program components were designed to audit the radiation dose calculation chain from the NIST traceable reference beam calibration, to inclusion of dosimetry parameters used to calculate tumor doses, to the delivery of the radiation dose. The QA program provided to international institutions includes: 1) remote TLD/OSLD audit of machine output, 2) credentialing for advanced technologies, and 3) review of patient treatment records. IROC Houston uses the same standards and acceptance criteria for all of its audits whether for North American or international sites.

Results:

IROC Houston's QA program has reached out to radiotherapy sites in 43 different countries since 2013 through their participation in clinical trials. In the past two years, 2,778 international megavoltage beam outputs were audited with OSLD/TLD. While the average IROC/Inst ratio is near unity for all sites monitored, there are international regions whose results are significantly different from the NA region. In the past 2 years, 477 and 87 IMRT H&N phantoms were irradiated at NA and international sites, respectively. Regardless of the OSLD beam audit results, the overall pass rate (87 percent) for all international sites (no region separation) is equal to the NA sites. Of the 182 international patient charts reviewed, 10.7 percent of the dose calculation points did not meet our acceptance criterion as compared to 13.6 percent for NA sites. The lower pass rate for NA sites results from a much larger brachytherapy component which has been shown to be more error prone.

Conclusion:

IROC Houston has expanded its QA services worldwide and continues a long history of improving radiotherapy dose delivery in many countries.

Funding received for QA audit services from the Korean GOG, DAHANCA, EORTC, ICON and CMIC Group
TU‐G‐BRD‐07: A Statistical Learning Approach to the Accurate Prediction of MLC Positional Errors During VMAT Delivery
Authors: Carlson J , Park J , Park S , Park J , Choi Y , Ye S
Published: June 2015

Purpose:

To quantify and predict the magnitude of multi‐leaf collimator (MLC) positional errors in volumetric modulated arc therapy (VMAT) plans using statistical learning techniques to allow more accurate representation of the dose distribution expected to be delivered.

Methods:

A total of 74 VMAT plans used for patient treatments from three separate institutions were acquired. All plans were delivered using a Varian Millennium 120 MLC. The plans were split into training (N=3), validation (N=6) and testing (N=65) sets. From these, numerical features such as individual leaf position and velocity, and categorical features such as whether the leaf was moving towards or away from the isocenter, the bank the leaf was a part of, and the control point (CP) at which the error occurred were extracted. The differences between planned and delivered leaf positions in the training data were used as a target response for the development of a linear regression model, a decision tree model, and a random forest model. Optimized model parameters were found using cross‐validation on the validation set. Performance of each model in predicting the positional errors was assessed using mean absolute error (MAE) and root mean square error (RMSE) on the held‐out test set.

Results:

The MAE between planned and delivered positions for moving MLCs was 1.27 mm (RMSE = 1.60 mm). The decision tree model had the best performance, the predictions of which had MAE for moving MLCs of 0.27 mm (RMSE = 0.39 mm). Leaf velocity significantly predicted position errors, (β = 0.128, p<0.0001), and explained a significant amount of the variance (r2=0.90, p<0.0001).

Conclusion:

The decision tree model accurately predicted actual MLC leaf positions during delivery. Incorporating predicted errors into the planned MLC positions leads to a more realistic representation of the leaf locations which can be expected during treatment delivery to the patient.
TU‐G‐BRD‐08: In‐Vivo EPID Dosimetry: Quantifying the Detectability of Four Classes of Errors
Authors: Ford E , Phillips M , Bojechko C
Published: June 2015

Purpose:

EPID dosimetry is an emerging method for treatment verification and QA. Given that the in‐vivo EPID technique is in clinical use at some centers, we investigate the sensitivity and specificity for detecting different classes of errors. We assess the impact of these errors using dose volume histogram endpoints. Though data exist for EPID dosimetry performed pre‐treatment, this is the first study quantifying its effectiveness when used during patient treatment (in‐vivo).

Methods:

We analyzed 17 patients; EPID images of the exit dose were acquired and used to reconstruct the planar dose at isocenter. This dose was compared to the TPS dose using a 3%/3mm gamma criteria. To simulate errors, modifications were made to treatment plans using four possible classes of error: 1) patient misalignment, 2) changes in patient body habitus, 3) machine output changes and 4) MLC misalignments. Each error was applied with varying magnitudes. To assess the detectability of the error, the area under a ROC curve (AUC) was analyzed. The AUC was compared to changes in D99 of the PTV introduced by the simulated error.

Results:

For systematic changes in the MLC leaves, changes in the machine output and patient habitus, the AUC varied from 0.78–0.97 scaling with the magnitude of the error. The optimal gamma threshold as determined by the ROC curve varied between 84–92%. There was little diagnostic power in detecting random MLC leaf errors and patient shifts (AUC 0.52–0.74). Some errors with weak detectability had large changes in D99.

Conclusion:

These data demonstrate the ability of EPID‐based in‐vivo dosimetry in detecting variations in patient habitus and errors related to machine parameters such as systematic MLC misalignments and machine output changes. There was no correlation found between the detectability of the error using the gamma pass rate, ROC analysis and the impact on the dose volume histogram.

Funded by grant R18HS022244 from AHRQ
TU‐G‐BRB‐01: Topic Introduction: Do We Need Clinical Trials in Particle Therapy and How Can Medical Physics Support Them?
Authors: Schulte R.
Published: June 2015

Proton therapy, in particular, and ion therapy, just beginning, are becoming an increasing focus of attention in clinical radiation oncology and medical physics. Both modalities have been criticized of lacking convincing evidence from randomized trials proving their efficacy, justifying the higher costs involved in these therapies.

This session will provide an overview of the current status of clinical trials in proton therapy, including recent developments in ion therapy. As alluded to in the introductory talk by Dr. Schulte, opinions are diverging widely as to the usefulness and need for clinical trials in particle therapy and the challenge of equipoise. The lectures will highlight some of the challenges that surround clinical trials in particle therapy. One, presented by Dr. Choy from UT Southwestern, is that new technology and even different types of particles such as helium and carbon ions are introduced into this environment, increasing the phase space of clinical variables. The other is the issue of medical physics quality assurance with physical phantoms, presented by Mrs. Taylor from IROC Houston, which is more challenging because 3D and 4D image guidance and active delivery techniques are in relatively early stages of development. The role of digital phantoms in developing clinical treatment planning protocols and as a QA tool will also be highlighted by Dr. Lee from NCI.

The symposium will be rounded off by a panel discussion among the Symposium speakers, arguing pro or con the need and readiness for clinical trials in proton and ion therapy.

Learning Objectives:

To get an update on the current status of clinical trials allowing or mandating proton therapy.

Learn about the status of planned clinical trials in the U.S. and worldwide involving ion therapy.

Discuss the challenges in the design and QA of clinical trials in particle therapy.

Learn about existing and future physical and computational anthropomorphic phantoms for charged particle clinical trial development and support.

Research reported in this presentation is supported by the National Cancer Institute of the National; Institutes of Health under Award Number P20CA183640.
TU‐G‐BRB‐02: Clinical Trials in Particle Therapy ‐ Open Questions
Authors: Choy H.
Published: June 2015

Proton therapy, in particular, and ion therapy, just beginning, are becoming an increasing focus of attention in clinical radiation oncology and medical physics. Both modalities have been criticized of lacking convincing evidence from randomized trials proving their efficacy, justifying the higher costs involved in these therapies.

This session will provide an overview of the current status of clinical trials in proton therapy, including recent developments in ion therapy. As alluded to in the introductory talk by Dr. Schulte, opinions are diverging widely as to the usefulness and need for clinical trials in particle therapy and the challenge of equipoise. The lectures will highlight some of the challenges that surround clinical trials in particle therapy. One, presented by Dr. Choy from UT Southwestern, is that new technology and even different types of particles such as helium and carbon ions are introduced into this environment, increasing the phase space of clinical variables. The other is the issue of medical physics quality assurance with physical phantoms, presented by Mrs. Taylor from IROC Houston, which is more challenging because 3D and 4D image guidance and active delivery techniques are in relatively early stages of development. The role of digital phantoms in developing clinical treatment planning protocols and as a QA tool will also be highlighted by Dr. Lee from NCI.

The symposium will be rounded off by a panel discussion among the Symposium speakers, arguing pro or con the need and readiness for clinical trials in proton and ion therapy.

Learning Objectives:

To get an update on the current status of clinical trials allowing or mandating proton therapy.

Learn about the status of planned clinical trials in the U.S. and worldwide involving ion therapy.

Discuss the challenges in the design and QA of clinical trials in particle therapy.

Learn about existing and future physical and computational anthropomorphic phantoms for charged particle clinical trial development and support.

Research reported in this presentation is supported by the National Cancer Institute of the National; Institutes of Health under Award Number P20CA183640.
TU‐G‐BRB‐03: IROC Houston's Proton Beam Validation for Clinical Trials
Authors: Taylor P.
Published: June 2015

Proton therapy, in particular, and ion therapy, just beginning, are becoming an increasing focus of attention in clinical radiation oncology and medical physics. Both modalities have been criticized of lacking convincing evidence from randomized trials proving their efficacy, justifying the higher costs involved in these therapies.

This session will provide an overview of the current status of clinical trials in proton therapy, including recent developments in ion therapy. As alluded to in the introductory talk by Dr. Schulte, opinions are diverging widely as to the usefulness and need for clinical trials in particle therapy and the challenge of equipoise. The lectures will highlight some of the challenges that surround clinical trials in particle therapy. One, presented by Dr. Choy from UT Southwestern, is that new technology and even different types of particles such as helium and carbon ions are introduced into this environment, increasing the phase space of clinical variables. The other is the issue of medical physics quality assurance with physical phantoms, presented by Mrs. Taylor from IROC Houston, which is more challenging because 3D and 4D image guidance and active delivery techniques are in relatively early stages of development. The role of digital phantoms in developing clinical treatment planning protocols and as a QA tool will also be highlighted by Dr. Lee from NCI.

The symposium will be rounded off by a panel discussion among the Symposium speakers, arguing pro or con the need and readiness for clinical trials in proton and ion therapy.

Learning Objectives:

To get an update on the current status of clinical trials allowing or mandating proton therapy.

Learn about the status of planned clinical trials in the U.S. and worldwide involving ion therapy.

Discuss the challenges in the design and QA of clinical trials in particle therapy.

Learn about existing and future physical and computational anthropomorphic phantoms for charged particle clinical trial development and support.

Research reported in this presentation is supported by the National Cancer Institute of the National; Institutes of Health under Award Number P20CA183640.
TU‐G‐BRB‐04: Digital Phantoms for Developing Protocols in Particle Therapy
Authors: Lee C.
Published: June 2015

Proton therapy, in particular, and ion therapy, just beginning, are becoming an increasing focus of attention in clinical radiation oncology and medical physics. Both modalities have been criticized of lacking convincing evidence from randomized trials proving their efficacy, justifying the higher costs involved in these therapies.

This session will provide an overview of the current status of clinical trials in proton therapy, including recent developments in ion therapy. As alluded to in the introductory talk by Dr. Schulte, opinions are diverging widely as to the usefulness and need for clinical trials in particle therapy and the challenge of equipoise. The lectures will highlight some of the challenges that surround clinical trials in particle therapy. One, presented by Dr. Choy from UT Southwestern, is that new technology and even different types of particles such as helium and carbon ions are introduced into this environment, increasing the phase space of clinical variables. The other is the issue of medical physics quality assurance with physical phantoms, presented by Mrs. Taylor from IROC Houston, which is more challenging because 3D and 4D image guidance and active delivery techniques are in relatively early stages of development. The role of digital phantoms in developing clinical treatment planning protocols and as a QA tool will also be highlighted by Dr. Lee from NCI.

The symposium will be rounded off by a panel discussion among the Symposium speakers, arguing pro or con the need and readiness for clinical trials in proton and ion therapy.

Learning Objectives:

To get an update on the current status of clinical trials allowing or mandating proton therapy.

Learn about the status of planned clinical trials in the U.S. and worldwide involving ion therapy.

Discuss the challenges in the design and QA of clinical trials in particle therapy.

Learn about existing and future physical and computational anthropomorphic phantoms for charged particle clinical trial development and support.

Research reported in this presentation is supported by the National Cancer Institute of the National; Institutes of Health under Award Number P20CA183640.
TU‐G‐BRB‐05: Panel Discussion: Clinical Trials in Proton and Ion Therapy ‐ Are We Ready?
Authors: Schulte R.
Published: June 2015

Proton therapy, in particular, and ion therapy, just beginning, are becoming an increasing focus of attention in clinical radiation oncology and medical physics. Both modalities have been criticized of lacking convincing evidence from randomized trials proving their efficacy, justifying the higher costs involved in these therapies.

This session will provide an overview of the current status of clinical trials in proton therapy, including recent developments in ion therapy. As alluded to in the introductory talk by Dr. Schulte, opinions are diverging widely as to the usefulness and need for clinical trials in particle therapy and the challenge of equipoise. The lectures will highlight some of the challenges that surround clinical trials in particle therapy. One, presented by Dr. Choy from UT Southwestern, is that new technology and even different types of particles such as helium and carbon ions are introduced into this environment, increasing the phase space of clinical variables. The other is the issue of medical physics quality assurance with physical phantoms, presented by Mrs. Taylor from IROC Houston, which is more challenging because 3D and 4D image guidance and active delivery techniques are in relatively early stages of development. The role of digital phantoms in developing clinical treatment planning protocols and as a QA tool will also be highlighted by Dr. Lee from NCI.

The symposium will be rounded off by a panel discussion among the Symposium speakers, arguing pro or con the need and readiness for clinical trials in proton and ion therapy.

Learning Objectives:

To get an update on the current status of clinical trials allowing or mandating proton therapy.

Learn about the status of planned clinical trials in the U.S. and worldwide involving ion therapy.

Discuss the challenges in the design and QA of clinical trials in particle therapy.

Learn about existing and future physical and computational anthropomorphic phantoms for charged particle clinical trial development and support.

Research reported in this presentation is supported by the National Cancer Institute of the National; Institutes of Health under Award Number P20CA183640.
TU‐G‐BRA‐01: Assessing Radiation‐Induced Reductions in Regional Lung Perfusion Following Stereotactic Radiotherapy for Lung Cancer
Authors: McGurk R , Schreiber E , Das S , Zagar T , Green R , Lawrence M , Sheikh A , McCartney W , Rivera P , Marks L
Published: June 2015

Purpose:

The dose‐dependent nature of radiation therapy (RT)‐induced lung injury following hypo‐fractionated stereotactic RT is unclear. We herein report preliminary results of a prospective study assessing the magnitude of RT‐induced reductions in regional lung perfusion following hypo‐fractionated stereotactic RT.

Methods:

Four patients undergoing hypo‐fractionated stereotactic lung RT (SBRT: 12 Gy × 4 fractions or 10 Gy × 5 fractions) had a pre‐treatment SPECT (single‐photon emission computed tomography) perfusion scan providing a 3D map of regional lung perfusion. Scans were repeated 3–6 months post‐treatment. Pre‐ and post SPECT scans were registered to the planning CT scan (and hence the 3D dose data). Changes in regional perfusion (counts per cc on the pre‐post scans) were computed in regions of the lung exposed to different doses of radiation (in 5 Gy intervals), thus defining a dose‐response function. SPECT scans were internally normalized to the regions receiving <5 Gy.

Results:

At 3 months post‐RT, the changes in perfusion are highly variable. At 6 months, there is a consistent dose‐dependent reduction in regional perfusion. The average percent decline in regional perfusion was 10% at 15–20 Gy, 20% at 20–25 Gy, and 30% at 25–30 Gy representing a relatively linear dose response with an approximate 2% reduction per Gray for doses in excess of 10 Gy. There was a subtle increase in perfusion in the lung receiving <10 Gy.

Conclusion:

Hypo‐fractionated stereotactic RT appears to cause a dose‐dependent reduction in regional lung perfusion. There appears to be a threshold effect with no apparent perfusion loss at doses <10 Gy, though this might be in part due to the normalization technique used. Additional data is needed from a larger number of patients to better assess this issue. This sort of data can be used to assist optimizing RT treatment plans that minimize the risk of lung injury.

Partly supported by the NIH (CA69579) and the Lance Armstrong Foundation
TU‐G‐BRA‐02: Can We Extract Lung Function Directly From 4D‐CT Without Deformable Image Registration?
Authors: Kipritidis J , Hofman M , Siva S , Callahan J , Le Roux P , Woodruff H , Counter W , Hardcastle N , Keall P
Published: June 2015

Purpose:

Dynamic CT ventilation imaging (CT‐VI) visualizes air volume changes in the lung by evaluating breathing‐induced lung motion using deformable image registration (DIR). Dynamic CT‐VI could enable functionally adaptive lung cancer radiation therapy, but its sensitivity to DIR parameters poses challenges for validation. We hypothesize that a direct metric using CT parameters derived from Hounsfield units (HU) alone can provide similar ventilation images without DIR. We compare the accuracy of Direct and Dynamic CT‐VIs versus positron emission tomography (PET) images of inhaled ⁶⁸Ga‐labelled nanoparticles (‘Galligas’).

Methods:

25 patients with lung cancer underwent Galligas 4D‐PET/CT scans prior to radiation therapy. For each patient we produced three CT‐ VIs. (i) Our novel method, Direct CT‐VI, models blood‐gas exchange as the product of air and tissue density at each lung voxel based on time‐averaged 4D‐CT HU values. Dynamic CT‐VIs were produced by evaluating: (ii) regional HU changes, and (iii) regional volume changes between the exhale and inhale 4D‐CT phase images using a validated B‐spline DIR method. We assessed the accuracy of each CT‐VI by computing the voxel‐wise Spearman correlation with free‐breathing Galligas PET, and also performed a visual analysis.

Results:

Surprisingly, Direct CT‐VIs exhibited better global correlation with Galligas PET than either of the dynamic CT‐VIs. The (mean ± SD) correlations were (0.55 ± 0.16), (0.41 ± 0.22) and (0.29 ± 0.27) for Direct, Dynamic HU‐based and Dynamic volume‐based CT‐VIs respectively. Visual comparison of Direct CT‐VI to PET demonstrated similarity for emphysema defects and ventral‐to‐dorsal gradients, but inability to identify decreased ventilation distal to tumor‐obstruction.

Conclusion:

Our data supports the hypothesis that Direct CT‐VIs are as accurate as Dynamic CT‐VIs in terms of global correlation with Galligas PET. Visual analysis, however, demonstrated that different CT‐VI algorithms might have varying accuracy depending on the underlying cause of ventilation abnormality.

This research was supported by a National Health and Medical Research Council (NHMRC) Australia Fellowship, an Cancer Institute New South Wales Early Career Fellowship 13‐ECF‐1/15 and NHMRC scholarship APP1038399. No commercial funding was received for this work.
TU‐G‐303‐01: Radiomics: Quantitative Imaging in the Service of Improved Treatment Decision Making
Authors: Deasy J.
Published: June 2015

‘Radiomics’ refers to studies that extract a large amount of quantitative information from medical imaging studies as a basis for characterizing a specific aspect of patient health. Radiomics models can be built to address a wide range of outcome predictions, clinical decisions, basic cancer biology, etc. For example, radiomics models can be built to predict the aggressiveness of an imaged cancer, cancer gene expression characteristics (radiogenomics), radiation therapy treatment response, etc. Technically, radiomics brings together quantitative imaging, computer vision/image processing, and machine learning. In this symposium, speakers will discuss approaches to radiomics investigations, including: longitudinal radiomics, radiomics combined with other biomarkers (‘pan‐omics’), radiomics for various imaging modalities (CT, MRI, and PET), and the use of registered multi‐modality imaging datasets as a basis for radiomics. There are many challenges to the eventual use of radiomics‐derived methods in clinical practice, including: standardization and robustness of selected metrics, accruing the data required, building and validating the resulting models, registering longitudinal data that often involve significant patient changes, reliable automated cancer segmentation tools, etc. Despite the hurdles, results achieved so far indicate the tremendous potential of this general approach to quantifying and using data from medical images. Specific applications of radiomics to be presented in this symposium will include: the longitudinal analysis of patients with low‐grade gliomas; automatic detection and assessment of patients with metastatic bone lesions; image‐based monitoring of patients with growing lymph nodes; predicting radiotherapy outcomes using multi‐modality radiomics; and studies relating radiomics with genomics in lung cancer and glioblastoma.

Learning Objectives:

Understanding the basic image features that are often used in radiomic models.

Understanding requirements for reliable radiomic models, including robustness of metrics, adequate predictive accuracy, and generalizability.

Understanding the methodology behind radiomic‐genomic (‘radiogenomics’) correlations.

Research supported by NIH (US), CIHR (Canada), and NSERC (Canada)
TU‐G‐303‐03: Machine Learning to Improve Human Learning From Longitudinal Image Sets
Authors: Veeraraghavan H.
Published: June 2015

‘Radiomics’ refers to studies that extract a large amount of quantitative information from medical imaging studies as a basis for characterizing a specific aspect of patient health. Radiomics models can be built to address a wide range of outcome predictions, clinical decisions, basic cancer biology, etc. For example, radiomics models can be built to predict the aggressiveness of an imaged cancer, cancer gene expression characteristics (radiogenomics), radiation therapy treatment response, etc. Technically, radiomics brings together quantitative imaging, computer vision/image processing, and machine learning. In this symposium, speakers will discuss approaches to radiomics investigations, including: longitudinal radiomics, radiomics combined with other biomarkers (‘pan‐omics’), radiomics for various imaging modalities (CT, MRI, and PET), and the use of registered multi‐modality imaging datasets as a basis for radiomics. There are many challenges to the eventual use of radiomics‐derived methods in clinical practice, including: standardization and robustness of selected metrics, accruing the data required, building and validating the resulting models, registering longitudinal data that often involve significant patient changes, reliable automated cancer segmentation tools, etc. Despite the hurdles, results achieved so far indicate the tremendous potential of this general approach to quantifying and using data from medical images. Specific applications of radiomics to be presented in this symposium will include: the longitudinal analysis of patients with low‐grade gliomas; automatic detection and assessment of patients with metastatic bone lesions; image‐based monitoring of patients with growing lymph nodes; predicting radiotherapy outcomes using multi‐modality radiomics; and studies relating radiomics with genomics in lung cancer and glioblastoma.

Learning Objectives:

Understanding the basic image features that are often used in radiomic models.

Understanding requirements for reliable radiomic models, including robustness of metrics, adequate predictive accuracy, and generalizability.

Understanding the methodology behind radiomic‐genomic (‘radiogenomics’) correlations.

Research supported by NIH (US), CIHR (Canada), and NSERC (Canada)
TU‐G‐204‐09: The Effects of Reduced‐ Dose Lung Cancer Screening CT On Lung Nodule Detection Using a CAD Algorithm
Authors: Young S , Lo P , Kim G , Hsu W , Hoffman J , Brown M , McNitt‐Gray M
Published: June 2015

Purpose:

While Lung Cancer Screening CT is being performed at low doses, the purpose of this study was to investigate the effects of further reducing dose on the performance of a CAD nodule‐detection algorithm.

Methods:

We selected 50 cases from our local database of National Lung Screening Trial (NLST) patients for which we had both the image series and the raw CT data from the original scans. All scans were acquired with fixed mAs (25 for standard‐sized patients, 40 for large patients) on a 64‐slice scanner (Sensation 64, Siemens Healthcare). All images were reconstructed with 1‐mm slice thickness, B50 kernel. 10 of the cases had at least one nodule reported on the NLST reader forms. Based on a previously‐published technique, we added noise to the raw data to simulate reduced‐dose versions of each case at 50% and 25% of the original NLST dose (i.e. approximately 1.0 and 0.5 mGy CTDIvol). For each case at each dose level, the CAD detection algorithm was run and nodules greater than 4 mm in diameter were reported. These CAD results were compared to “truth”, defined as the approximate nodule centroids from the NLST reports. Subject‐level mean sensitivities and false‐positive rates were calculated for each dose level.

Results:

The mean sensitivities of the CAD algorithm were 35% at the original dose, 20% at 50% dose, and 42.5% at 25% dose. The false‐positive rates, in decreasing‐dose order, were 3.7, 2.9, and 10 per case. In certain cases, particularly in larger patients, there were severe photon‐starvation artifacts, especially in the apical region due to the high‐attenuating shoulders.

Conclusion:

The detection task was challenging for the CAD algorithm at all dose levels, including the original NLST dose. However, the false‐positive rate at 25% dose approximately tripled, suggesting a loss of CAD robustness somewhere between 0.5 and 1.0 mGy.

NCI grant U01 CA181156 (Quantitative Imaging Network); Tobacco Related Disease Research Project grant 22RT‐0131.
TU‐G‐207‐00: Emerging Applications of X‐Ray Imaging
Authors: Xing Lei
Published: June 2015

Last few years has witnessed the development of novel of X‐ray imaging modalities, such as spectral CT, phase contrast CT, and X‐ray acoustic/fluorescence/luminescence imaging. This symposium will present the recent advances of these emerging X‐ray imaging modalities and update the attendees with knowledge in various related topics, including X‐ray photon‐counting detectors, X‐ray physics underlying the emerging applications beyond the traditional X‐ray imaging, image reconstruction for the novel modalities, characterization and evaluation of the systems, and their practical implications. In addition, the concept and practical aspects of X‐ray activatable targeted nanoparticles for molecular X‐ray imaging will be discussed in the context of X‐ray fluorescence and luminescence CT.

Learning Objectives:

Present background knowledge of various emerging X‐ray imaging techniques, such as spectral CT, phase contrast CT and X‐ray fluorescence/luminescence CT.

Discuss the practical need, technical aspects and current status of the emerging X‐ray imaging modalities.

Describe utility and future impact of the new generation of X‐ray imaging applications.
TU‐G‐207‐01: CT Imaging Using Energy‐Sensitive Photon‐Counting Detectors
Authors: Taguchi K.
Published: June 2015

Last few years has witnessed the development of novel of X‐ray imaging modalities, such as spectral CT, phase contrast CT, and X‐ray acoustic/fluorescence/luminescence imaging. This symposium will present the recent advances of these emerging X‐ray imaging modalities and update the attendees with knowledge in various related topics, including X‐ray photon‐counting detectors, X‐ray physics underlying the emerging applications beyond the traditional X‐ray imaging, image reconstruction for the novel modalities, characterization and evaluation of the systems, and their practical implications. In addition, the concept and practical aspects of X‐ray activatable targeted nanoparticles for molecular X‐ray imaging will be discussed in the context of X‐ray fluorescence and luminescence CT.

Learning Objectives:

Present background knowledge of various emerging X‐ray imaging techniques, such as spectral CT, phase contrast CT and X‐ray fluorescence/luminescence CT.

Discuss the practical need, technical aspects and current status of the emerging X‐ray imaging modalities.

Describe utility and future impact of the new generation of X‐ray imaging applications.
TU‐G‐201‐03: Imaging Systems in Radiotherapy: Buying, Installing, and Using
Authors: Hunt M.
Published: June 2015

This session will update therapeutic physicists on technological advancements and radiation oncology features of commercial CT, MRI, and PET/CT imaging systems. Also described are physicists’ roles in every stage of equipment selection, purchasing, and operation, including defining specifications, evaluating vendors, making recommendations, and optimal and safe use of imaging equipment in radiation oncology environment.

The first presentation defines important terminology of CT and PET/CT followed by a review of latest innovations, such as metal artifact reduction, statistical iterative reconstruction, radiation dose management, tissue classification by dual energy CT and spectral CT, improvement in spatial resolution and sensitivity in PET, and potentials of PET/MR. We will also discuss important technical specifications and items in CT and PET/CT purchasing quotes and their impacts.

The second presentation will focus on key components in the request for proposal for a MRI simulator and how to evaluate vendor proposals. MRI safety issues in radiation Oncology, including MRI scanner Zones (4‐zone design), will be discussed. Basic MR terminologies, important functionalities, and advanced features, which are relevant to radiation therapy, will be discussed.

In the third presentation, justification of imaging systems for radiation oncology, considerations in room design and construction in a RO department, shared use with diagnostic radiology, staffing needs and training, clinical/research use cases and implementation, will be discussed. The emphasis will be on understanding and bridging the differences between diagnostic and radiation oncology installations, building consensus amongst stakeholders for purchase and use, and integrating imaging technologies into the radiation oncology environment.

Learning Objectives:

Learn the latest innovations of major imaging systems relevant to radiation therapy

Be able to describe important technical specifications of CT, MRI, and PET/CT

Understand the process of budget request, equipment justification, comparisons of technical specifications, site visits, vendor selection, and contract development
TU‐F‐CAMPUS‐T‐05: Replacement Computational Phantoms to Estimate Dose in Out‐Of‐Field Organs and Tissues
Authors: Gallagher K , Tannous J , Nabha R , Feghali J , Ayoub Z , Jalbout W , Youssef B , Taddei P
Published: June 2015

Purpose:

To estimate the absorbed dose in organs and tissues at risk for radiogenic cancer for children receiving photon radiotherapy for localized brain tumors (LBTs) by supplementing their missing body anatomies with those of replacement computational phantoms. Applied beyond the extent of the RT Images collected by computed tomography simulation, these phantoms included RT Image and RT Structure Set objects that encompassed sufficient extents and contours for dosimetric calculations.

Method:

Nine children, aged 2 to 14 years, who received three‐dimensional conformal radiotherapy for low‐grade LBTs, were randomly selected for this study under Institutional‐Review‐Board protocol. Because the extents of their RT Images were cranial only, they were matched for size and sex with patients from a previous study with larger extents and for whom contours of organs at risk for radiogenic cancer had already been delineated. Rigid fusion was performed between the patients’ data and those of the replacement computational phantoms using commercial software. In‐field dose was calculated with a clinically‐commissioned treatment planning system, and out‐of‐field dose was estimated with an analytical model.

Results:

Averaged over all nine children and normalized for a therapeutic dose of 54 Gy prescribed to the PTV, where the PTV is the GTV, the highest mean organ doses were 3.27, 2.41, 1.07, 1.02, 0.24, and 0.24 Gy in the non‐tumor remainder, red bone marrow, thyroid, skin, breasts, and lungs, respectively. The mean organ doses ranged by a factor of 3 between the smallest and largest children.

Conclusion:

For children receiving photon radiotherapy for LBTs, we found their doses in organs at risk for second cancer to be non‐negligible, especially in the non‐tumor remainder, red bone marrow, thyroid, skin, breasts, and lungs. This study demonstrated the feasibility for patient dosimetry studies to augment missing patient anatomy by applying size‐ and sex‐matched replacement computational phantoms with pre‐contoured organs.

Funding is in part by the Fogarty International Center award K01TW008409, and the Portland Chapter of the Achievement Rewards for College Scientists. The content is solely the responsibility of the authors, and does not necessarily represent the official views of the sponsors. The authors declare no conflict of interest.