bluuebunny/crossref_metadata_2025_split huggingface dataset:
TU‐C‐AUD‐03: Comparing the Expected Effectiveness of Helical Tomotherapy and MLC‐Based IMRT Using Biological Measures
Authors: Mavroidis P , Ferreira B , Shi C , Lind B , Stathakis S , Papanikolaou N 
Published: July 2007

Purpose: Presently, the radiobiological parameters of the different tumours and normal tissues are typically not taken into account during dose prescription and optimization of a treatment plan. In this study, to investigate a more comprehensive treatment plan evaluation, the biologically effective uniform dose (D̿) is applied together with the complication‐free tumour control probability (P+).Material and Methods: Three different cancer types at different anatomical sites were investigated: head & neck, lung and prostate cancers. For each cancer type, a linac MLC‐based step‐and‐shoot IMRT plan and a Helical Tomotherapy plan were developed. By using D̿ as the common prescription point of the treatment plans and plotting the tissue response probabilities vs. D̿ for a range of prescription doses, a number of plan trials can be compared based on radiobiological measures. Results: The applied plan evaluation method shows that in the head & neck cancer case the HT treatment gives better results than the MLC‐based IMRT (P+ of 62.2% and 46.0%, D̿ to the internal target volume (ITV) of 72.3Gy and 70.7Gy, respectively). In the lung cancer and prostate cancer cases, the MLC‐based IMRT plans are better. For the lung cancer case, the HT and MLC‐based IMRT plans give a P+ of 66.9% and 72.9%, D̿ to the ITV of 64.0Gy and 66.9Gy, respectively. Similarly, for the prostate cancer case, the two radiation modalities give a P+ of 68.7% and 72.2%, D̿ to the ITV of 86.0Gy and 85.9Gy, respectively.Discussion and Conclusions: Both MLC based‐IMRT and HT can encompass the often large ITV required while they minimize the volume of the organs at risk receiving high dose. There may exist clinical cases, which may look dosimetrically similar but in radiobiological terms may be quite different. In such situations, traditional dose based evaluation tools can be complemented by the use of P+ − D̿ diagrams to compare treatment plans.
TU‐C‐L100E‐01: Funding and Protecting Biomedical Research
Authors: Hendee W , Deye J , Farahani K 
Published: July 2007

Biomedical research is supported principally by two sources: the National Institutes of Health (NIH) and industry. For research in medical physics, the National Cancer Institute (NCI) and the National Institute of Biomedical Imaging and Bioengineering (NIBIB) are the two principal supporting agencies within the NIH. These agencies have a number of funding programs that are designed for specific purposes. Applications for support from them are prepared according to specific guidelines and must match the intent of a specific program. Writing a winning application is an art as well as a science, and counsel from experienced grantees is invaluable during the preparation of an application. It is also important to understand the review process that ensues after an application is submitted, and the criteria by which a final decision about funding of the application is reached.The second source of support, industry, is much less structured and usually requires a personal relationship between the investigator and the company providing the research funding. Negotiating a research agreement between the investigator, the investigator's institution, and the company can be challenging, because it involves issues such as the publication of research results, ownership of intellectual property, and indemnification of each party against wrongdoing by the other. At times these negotiations break down because the parties cannot agree on the issues, often because one party (frequently the institution) assumes an unreasonable position. Successful negotiating an industry research agreement requires diplomacy and sensitivity as well as objectivity and focus.In all research grants and agreements, the protection of intellectual property (IP) is of overriding importance, especially now that institutions are viewed increasingly as engines for economic development through technology licenses and the formation of start‐up companies. IP protection is less arcane than it may seem, but it does require dedicated time and effort by the investigator and a willingness to work with attorneys and the institution's technology transfer office.
TU‐D‐L100F‐01: MR Biomarkers: Current Applications and Unmet Needs
Authors: Jackson E 
Published: July 2007

The application of MR imaging biomarkers in pre‐clinical studies as well as Phase I/II clinical trials has greatly expanded over the past few years. Such MR biomarkers include measures obtained from dynamic contrast agent enhanced MRI (DCE‐MRI), dynamic susceptibility change MRI (DSC‐MRI), diffusion MRI, blood oxygen level dependent (BOLD) MRI, and in vivo spectroscopy. The symposium session will introduce each of these techniques and provide representative pre‐clinical and clinical trial results using each technique. In addition, more novel applications, such as MR molecular imaging techniques, will be introduced. Finally, a summary of unmet needs of MR imaging biomarkers, specifically the need for standardization, quality control, and change assessment criteria, will be presented. These needs must be addressed in order toEducational Objectives:1. To understand the physical basis, applications, and current limitations of DCE‐MRI, DSC‐MRI, diffusion MRI, BOLD MRI, and MR spectroscopy techniques currently employed to obtain non‐invasive MR biomarkers.2. To understand the need for standardization, quality control, and change assessment tools/criteria development.
TU‐D‐BRA‐03: Laser‐Accelerated Electrons for Radiation Therapy
Authors: Malka V , Fuchs T , Oelfke U , Szymanowski H , Faure J , Glinec Y , Rechatin C 
Published: July 2007

Laser plasma accelerators provide electron beams with parameters of interest in many fields and in particular for radiotherapy. A short review of progress achieved recently including bubble [1] and colliding [2] schemes will be presented. Using the last improvements of laser‐plasma accelerators, we performed dose deposition simulations using a quasi‐monoenergetic electron beam in the 200 MeV range [3]. It is shown that electron beam properties offer advantageous dosimetric characteristics compare to those calculated with high energy photons. The depth dose curve shows a broad maximum at large depths (> 20 cm). The lateral penumbra of treatment fields for focused electron beams is smaller compared to 6 MeV photons at depths smaller than 10 cm. These advantages result in an improvement of the quality of a clinically approved prostate treatment plan. While the target coverage is the same or even slightly better for 250 MeV electrons compared to photons the dose sparing of sensitive structures is improved. E.g. the dose to the rectum is reduced by 19% for 250 MeV, focused electrons. These findings agree with previous results regarding very high energy electrons as a treatment modality [4, 5, 6].The lack of compact and cost‐efficient electron accelerators could be overcome by laser‐plasma systems.Educational Objectives:1. Understand the origin electron injection in plasma.2. Understand the acceleration process and to motivate this approach which uses extremely high electric field.3. Understand the issues related to clinical application for radiotherapy.
TU‐EE‐A1‐04: Dimension Reduction Analysis of Dose Volume Histogram And Its Potential Application In Predicting Normal Tissue Complication Probability
Authors: Zhou S , Das S , Chen S , Zhang J , Marks L 
Published: July 2007

Purpose: Radiation pneumonitis (RP) is a major concern for patients receiving radiotherapy for lung cancer. The present study assesses the possibility of using multiple dose‐volume‐histogram (DVH) based metrics to predict the likelihood of grade ⩾ 2 RP. MATERIALS AND METHODS: The lung DVH and clinical outcome data from 235 patients were studied. Two linear and four nonlinear statistical dimension reduction analysis methods were applied to the lung DVH to map the data from the original feature space into a 2D or 3D manifold. Then, the question of whether the lung DVH could uniquely predict the likelihood of grade ⩾ 2 RP was mapped to the feasibility of separating the populations with and without RP in the 2D/3D manifold. Results: None of the statistical dimension reduction techniques which preserve the local geometric properties of the original DVH curves was able to clearly separate the patients with and without grade ⩾ 2 RP in the 2D/3D manifold. Among the techniques tested, the Local Tangent Space Alignment (LTSA) performed the best. It could almost reduce the original DVH data into a one dimension manifold. Unfortunately the order the LTSA assigned to the lung DVH curves did show clear correlation with patient RP grades. Conclusions: The dimension reduction analysis like LTSA which preserve the distance information between DVH curves can be useful in characterizing the complexity of patient DVH data from a lung toxicity study. The lack of clear segmentation between the grade ⩾ 2 RP patients and other patients in the dimension‐reduced manifold indicates that using lung DVH data only can not generate a satisfactory result in predicting the occurrence of grade ⩾ 2 RP among the lung cancer patients after 3D‐CRT radiotherapy treatment.This work was partially funded by NIH grants R01 CA69579 and R01 CA115748.
WE‐C‐L100J‐08: Charge Trapping in a Prototype Active Matrix Flat Panel Dosimeter and Its Implications
Authors: Chen Y , Moran J , Roberts D , El‐Mohri Y , Antonuk L , Fraass B 
Published: July 2007

Purpose: This work models charge trapping behavior of a prototype Active Matrix Flat Panel Dosimeter (AMFPD) using three parameters and explains a number of published observations. An understanding of charge trapping and release is necessary to estimate non‐linearities in the AMFPD response due to trapping and to correct artifacts in the resulting dose image. Method and Materials: The AMFPD consisted of an amorphous silicon flat panel imaging array operated without a phosphor screen. Fluoroscopic and radiographic modes were used to obtain a series of fixed field dosimetric measurements at different doses and dose rates. Data were acquired in order to test the assumptions upon which the model was based:(1) Trapped charge density in the metastable defects can be described by a stretched exponential function, .(2) Trapped charge starts to release from the trapping centers when the photodiode is recharged.(3) Charge release is not affected by subsequent irradiations when the dose per frame is small.(4) The charge trapping rate depends on bias voltage and varies slowly with dose when the dose is small.Model stretch parameter β, time constant τ, and the charge trapping rate p were determined from a fit to the pixel signal decay following irradiation. These parameters were then applied to simulate results for the AMFPD operated in fluoroscopic mode based on the above assumptions. Results: The simulated results agreed well with the measurements. It was determined that β is constant for a detector array, τ depends on bias voltage, and the charge trapping rate depends on bias voltage and dose. Furthermore, the model qualitatively explains observations reported in published papers on charge trapping. Conclusion: A three parameter model was found to successfully describe the behavior of charge trapping and release at different values of bias voltage, frame rate, dose rate and dose.
WE‐D‐M100F‐01: Introduction of Imaging for Treatment Assessment
Authors: Cao Y 
Published: July 2007

In vivo biomedical imaging for assessment of therapeutic response is becoming an increasingly important field. Early assessment and prediction of treatment response allow for individualized re‐optimization of therapy, which represents a novel concept and a paradigm shift from conventional clinical trials. Recent Phase I/II trials have shown that biomedical imaging, including CT, MRI, PET, can provide an indication of therapeutic response, and possibly prior to the radiographic changes. In vivo biomedical imaging for assessment of therapeutic response is a dynamic and fast growing field. Many new trials are ongoing or in the design phase. The complicity of imaging technologies provides an opportunity for more AAPM members to engage in either single center trials or multi‐center trials in coming years. This symposium will provide overviews on PET/SPECT, MRI/MRS and the integration of multimodality imaging in clinical trials for assessment of treatment response.The objectives of this symposium are:1. What imaging modalities have shown potential value in phase I/II trials for assessment of therapeutic responses;2. What are the advantages and limitations of using in vivo functional and metabolic imaging in clinical trials compared to conventional paradigms;
WE‐D‐M100F‐02: PET for Chemo/radiation Therapy Response Assessment
Authors: Jeraj R 
Published: July 2007

The most commonly used method to assess treatment response relies on measuring tumor sizes before and after treatment and classifying tumor anatomical shrinkage according to RECIST or WHO criteria. However, there is a considerable variability between individual studies and the same response rate can be associated with completely different survival rates. Furthermore, it is known that changes in tumor biological function significantly precede gross anatomical tumor changes. Positron emission tomography (PET) is the most sensitive, specific and versatile imaging modality that can be used for this purpose.‐Fluoro‐deoxyglucose (FDG) is the most commonly used PET imaging agent for treatment assessment. FDG shows regions of active glucose metabolism, which are typically decreased after tumor cells die in response to antineoplastic therapies. Besides FDG, several other PET agents exist, which are more specific in cell targeting, and can image different aspects of biological response to therapy. Cell proliferation, apoptosis and angiogenesis are processes that are typically affected by antineoplastic therapies. Currently, the most promising non‐FDG agent is ‐Fluorodeoxythymidine (FLT) as a marker of cell proliferation. PET imaging agents of apoptosis and angiogenesis are still mostly limited to preclinical studies. Use of PET imaging for treatment assessment imposes special requirements on image acquisition, reconstruction and analysis.FDG‐PET has shown an extreme promise to assess treatment efficacy, both after, as well as during the course of therapy. Depending on the metabolic response, it is possible to classify patients into metabolic responders, which have typically much longer survival rates than metabolic non‐responders. Unfortunately, FDG is not without problems. Two of the most severe are (1) radiation‐induced inflammation during radiation therapy and (2) metabolic flare that occurs early after the start of some chemotherapies. FLT‐PET, which assesses proliferative response, seems to overcome these problems; however, more clinical studies are needed to prove its wider applicability. Reproducible and accurate PET image acquisition, reconstruction and analysis are the key components required for quantitative PET imaging, which provides foundation for treatment assessment.This symposium reviews the status of treatment assessment studies that involve repeat PET imaging during and after therapy. It discusses advantages and disadvantages of FDG and non‐FDG‐PET imaging for treatment assessment. It also emphasizes importance of the appropriate PET imaging acquisition, reconstruction and analysis that forms the basis for PET image quantification.Educational Objectives:1. Overview of FDG‐PET imaging for treatment assessment.2. Overview of non‐FDG‐PET imaging for treatment assessment.3. Review PET image acquisition, reconstruction and analysis for treatment assessment.4. Discuss future of PET imaging for treatment assessment.
WE‐D‐M100F‐04: Integration of Multi‐modality Imaging in Clinical Trials
Authors: Lawrence T 
Published: July 2007

Treatment responses and late normal tissue injury are conventionally assessed months or years after the completion of therapy by standard clinical endpoints, such as local progression free survival or late fibrosis. This conventional paradigm presents two major weaknesses. First, at the time of the treatment outcomes being determined, it is often too late to change the outcome of patients. Secondly, takes a large number of patients and a long time to determine the efficacy of the tested treatment. It is urgent for clinical scientists to change this conventional paradigm and to assess the therapeutic response early, i.e. prior to the end of planned therapy. For early assessment of therapeutic responses, conventional clinical endpoints are no longer adequate. Functional, metabolic, and molecular imaging could provide a means or a marker for early assessment of normal tissue injury or of treatment responses prior to anatomic measurements of disease progression, thereby permitting re‐optimization of individual patient treatment strategies. This lecture will provide examples how to integrate multi‐modality imaging in clinical trials for early assessment of treatment response and normal tissue toxicity. The implications of the results will also be discussed.Learning Objectives:1. Understand the time courses of response and toxicity.2. Appreciate windows of opportunity for early assessment.3. Introduce clinical trial design issues for early assessment.
WE‐D‐AUD‐01: Clincal Evaluation of An Independent Dose Check Algorithm for Helical TomoTherapy
Authors: Gibbons J , Smith K , Cheek D , Rosen I 
Published: July 2007

Purpose: To determine the clinical acceptability of an algorithm developed to independently verify doses calculated by the TomoTherapy treatment planning system. Method and Materials: Point doses from treatment plans for 97 patients treated on a TomoTherapy system were compared to an independent dose calculation algorithm developed at our facility. All patient plans for which treatment sinograms were available were included in the comparison, which represented a variety of treatment sites and plan parameters. For each treatment plan, the calculation point was selected to be in the geometric center of the primary PTV, where beam modulation and high dose‐gradients were expected to be minimal. If this process put the point into a high dose‐gradient region or very near a tissue interface region, the point was manually repositioned. Results: Comparisons of our calculation to the TomoTherapy‐predicted point doses for the patient treatment plans showed good agreement. For sites other than lung and superficial PTVs, agreement between the calculations was within 2% for 94% of the patient calculations (64 of 68). Our independent calculations within the lung or superficial PTVs overestimated the dose by an average of 3.1% (σ =2.4%) and 3.2% (σ=2.2%), respectively. Conclusion: Systematic errors at points within lung are probably the result of the known weakness of the radiological path length method for correcting for missing tissue and/or tissue density heterogeneities. Errors encountered at points within superficial PTVs are probably the result of our algorithm overestimating the scatter dose at points near the surface of the patient. For the majority of cases, the algorithm demonstrates sufficient accuracy for clinical use and may be used to independently verify patient treatment plans.Supported in part by a research agreement with TomoTherapy, Inc.
WE‐D‐M100J‐01: Enhancement of Cell Killing by X‐Ray Irradiation in the Presence of Gold Nanoparticles
Authors: Kulkarni R , Sramek B , Lisle A , Boote E , Caldwell C , Katti K 
Published: July 2007

Purpose: This investigation was initiated to determine the radiobiologic enhancement for x‐ray irradiation of cells in the presence of citrate‐stabilized gold nanoparticles. Method and materials: Citrate‐stabilized gold nanoparticles were added to a strain of lymphoma cells in suspension at a concentration of 0.017 mg of gold per ml. Cell suspensions prepared included a two sham controls, and two samples with gold nanoparticles. One sham and one gold nanoparticle based sample were irradiated with x‐ray photons from a clinical x‐ray device (120 kVp, 6.67 mm Al equivalent beam). A total dose of 0.91 Gy was delivered in two approximately equal parts (24 hour separation). The non‐irradiated cell suspensions were treated identically. Cell survival for non‐irradiated cell suspensions and irradiated cell suspensions were determined over 72 hours using methylene blue dye exclusion. Results: The ratio of live:dead cells for all cell suspensions was 7.5:1 at the start of the experiment. After 72 hours, the irradiated cells exhibited a ratio approximately 50% lower than the non‐irradiated cells. The irradiated cell suspension with gold nanoparticles showed enhanced cell killing. Conclusions: Even at the low gold concentration and low x‐ray energy, gold nanoparticles exhibit some enhancement of cell killing. Further studies are ongoing using increasing gold concentrations and varying radiation doses. It is likely that the presence of higher Z materials contributes to secondary electron dose in a way that may be described only through microdosimetry methods.Gold nanoparticle‐enhanced radiation therapy is a possible outcome of this work. Additional effort is directed toward functionalized gold nanoparticles using targeting moieties for specific cancers. This work contributes toward an understanding of the therapeutic enhancement that may be expected with specific concentrations of gold nanoparticles.Supported by: NIH R01 CA119412‐01.
WE‐D‐BRA‐03: Cyberknife Experience
Authors: Dieterich S 
Published: July 2007

Purpose: The purpose of this presentation is to show in selected case studies where differential dose planning is used in Cyberknife treatments, and which challenges are associated with each approach. Method and Materials: Three case studies were selected to demonstrate different situations were differential dose planning would be used in Cyberknife SRS. Case1: Multiple, anatomically close cranial lesions of varying sizes. As experience with Gammaknife SRS has shown, the risk of complications in treating brain metastasis is correlated with dose and lesion size. Lesions larger than 2 cm in diameter are typically treated with a lower dose. In the situation were multiple lesions of different size are located closely together in the brain, creating separate treatment plans on the Cyberknife would lead to longer treatment times, higher whole‐body dose due to scatter and leakage, and difficulty to asses multiple plan dose overlays.Case 2: The second situation involved mostly head and neck cancers where the GTV and CTV are treated to different doses as a boost after conventional IMRT treatments. Typically, the GTV encompasses the PET positive areas. Around the GTV, a CTV enclosing the microscopic extension of the disease as determined by the physician based on the case history.Case 3: Unusual cases. A patient with pituitary adenoma was also diagnosed with Graves disease. Because of the proximity of the lesion and the orbital muscles affected by Graves disease, the tumor and orbital muscles were treated at the same time with different dose. Results: All three categories could be planned to the physicians' satisfaction. In case 1 patients, attention has to be paid to minimizing the dose to the healthy brain between the lesions. This can be achieved by using tuning structures or tuning shells around the tumors. In Case 2, the limiting factor is the dose fall‐off outside the GTV. A fraction of the CTV will be treated at a higher dose than planned. In case 3, the combined planning of the Graves disease and the pituitary adenoma achieved good dose sparing of the optic apparatus. Conclusion: The Cyberknife software is very flexible and allows relatively easy planning for complex situations.