bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐GG‐T‐513: The Prediction of Output Factor of Range Modulated Bragg Peak Using Patient and Beam Data
Authors: Kim D , Lee S , Lim Y , Kwak J , Park S , Shin D , Yoon M , Park S , Cho K
Published: July 2008

Purpose: In proton therapy, the patient quality assurance (QA) is performed by measuring the beam range, spread‐out bragg peak (SOBP) and the output factor. There is a method to get the output factor without patient QA procedure but predicted output factor from other patient's QA data. The purpose of this study is that we estimate the output factor prediction conformity and study the method which has no statistical limitation of patient QA data. Method and Materials: To evaluate the prediction conformity, We compare the predicted output factor which is came from the function of r = (Range‐SOBP)/SOBP, with measured output factor by patient QA. The parameters of the output factor function are calculated by fitting 2‐dimensional graph which is consisted of r and output factor. This study is base on 100 patients QA data at National Cancer Center (NCC) in Korea. In addition, we tried to find another method of output factor expectation by measuring 10 points of data set at each options. This method will be from statistical limitation of patient data. Results: The output prediction from patient QA data shows less than 2% of discrepancy. The output prediction using beam data set provides good agreement as less than 2% of discrepancy from real measurement. Conclusion: The beam data based output prediction is well matched with measurement as patient data based prediction which has statistical limitation.
SU‐GG‐T‐515: The Effect of Changes in the Content of Air in the Small Bowel On Dose Distributions in Proton and Photon Therapy for Pancreatic Cancer
Authors: Ingram M , Kassaee A , McDonough J , Metz J , Weilliver M
Published: July 2008

Purpose: To determine how changes in the content of air in the small bowel affects dose distributions for conformal, IMRT, and proton therapy in the treatment of pancreatic cancer. Method and Materials: Treatment plans were developed for six post‐operative pancreatic cancer patients using conformal, IMRT, and proton scattered beam planning. Plans were first calculated (using inhomogeneities) and normalized so that 95% of the volume received the prescription dose. The air in the small bowel was then contoured and given a Hounsfield unit of zero. The original plans were then recalculated on the edited CT set (again using inhomogeneities) with identical beam line parameters and monitor units. This case corresponds to the situation where the patient is planned with air in the small bowel but then treated with no air. In the second case, plans were generated on the CT sets with all air given a HU of zero and then recalculated on the original CT (containing air). Changes in dose homogeneity and coverage were compared for the two cases for each patient. Results: When plans were recalculated on the CT set with no air, the protons plans saw a large decrease in dose homogeneity while photons plans changed very little. Dose coverage also decreased more for proton plans than for the photon plans. Proton plans were less sensitive in the case where plans were recalculated on the CT set containing air but still had worse coverage and generally a greater decrease in target homogeneity than did the photon plans. Conclusion: Proton plans are greatly sensitive to changes in the content of air in the patient when treating pancreatic cancer while photon plans are minimally affected. Changes in the content of air may cause proton plans to under dose the target or overdose normal tissue.
SU‐GG‐T‐518: Comparison of Measured and Calculated Dose to the Contralateral Breast During Breast Irradiation with Tangential Fields
Authors: Novak J , Kassaee A , Both S , Styles T
Published: July 2008

Purpose: To compare calculated and measured dose to the contralateral breast for breast irradiation with tangential fields. Method and Materials: Doses to 14 points distributed throughout the contralateral breast were calculated and measured in a female anthropomorphic RANDO phantom for tangential‐field breast treatment. Traditional and forward tangential treatment plans with 6 MV and 15 MV beams were generated for the target breast using the Varian Eclipse (version 7.7.51, algorithm PBC) and Nucletron Oncentra MasterPlan (OTP) (version 1.4.3.1) treatment planning systems. Doses were measured in the contralateral breast by placing thermoluminescent dosimeters (TLDs) at the 14 points during radiation delivery of the plans. The target breast was treated to a dose of 180 cGy per fraction for each plan. Results: For 6 MV beams, the mean measured dose was 4.1 cGy, and the Eclipse‐ and OTP‐calculated mean doses were 2.5 and 5.3 cGy, respectively. For 15 MV beams, the mean measured dose was 5.2 cGy, and the Eclipse‐ and OTP‐calculated doses were 1.8 and 5.6 cGy, respectively. However, the OTP‐calculated doses were in better agreement with the measured doses: the mean percent differences between the Eclipse‐calculated and measured doses were −67%, and −40% for the 6 MV beams and 15 MV beams, respectively, while the mean percent differences for OTP were 29% and 6%. In addition, the percent difference between the Eclipse‐calculated and measured doses increased with increasing distance from midline, while for OTP this difference diminished. Conclusion: Calculation of the dose outside the primary radiation field is difficult for most model‐based treatment planning systems unless a Monte‐Carlo‐based algorithm is used. The Eclipse‐calculated dose to the contralateral breast was less than the measured dose, while for 83% of the points the OTP‐calculated dose was greater than the measured dose. However, the OTP‐calculated dose was in better agreement with the measured dose.
SU‐GG‐T‐522: Reducing Stray Radiation Dose for a Pediatric Patient Receiving Craniospinal Irradiation with Protons
Authors: Taddei P , Mirkovic D , Fontenot J , Giebeler A , Zheng Y , Titt U , Woo S , Newhauser W
Published: July 2008

Purpose: Proton therapy is an emerging treatment modality for pediatric cancer patients because of its advantageous depth‐dose relationship. Although proton dose distributions conform to the target volume, stray neutrons deliver low doses to healthy tissues throughout the body. These exposures may increase the risk of radiation carcinogenesis, particularly for pediatric patients. The aim of this study was to quantify stray radiation dose for a pediatric patient receiving proton craniospinal irradiation and to evaluate methods of reducing stray radiation dose to the patient. Method and Materials: Equivalent dose to each organ and effective dose from stray radiation was estimated for a 30.6 Gy craniospinal treatment using Monte Carlo simulations of a passively‐scattered proton nozzle and a human phantom. The treatment plan and phantom were based on CT images of a 10‐year‐old boy treated for medulloblastoma. Comparisons were made between the existing nozzle, an idealized nozzle with no stray radiation, and the existing nozzle with modest modifications to suppress stray radiation. The existing nozzle was modified by increasing the distance from the patient to the primary external neutron source and enhancing the local shielding. Results: Effective dose from stray radiation was 396 mSv and 74 mSv for the existing and idealized nozzles, respectively, while modest modifications to the nozzle reduced effective dose emanating from the nozzle by 43%. Conclusion: These results add to the body of evidence supporting the suitability of passively‐scattered proton beams for the treatment of pediatric cancer and confirm that the effective dose from stray radiation was not excessive and can be substantially reduced by modest enhancements to the nozzle. Conflict of Interest (only if applicable): We would like to disclose that a similar presentation will be given to a largely different audience at the International Conference on Radiation Shielding in April 2008.
SU‐GG‐T‐527: Multi‐Objective IMRT Planning Which Produces Deliverable Plans
Authors: Craft D , Carlsson F , Bortfeld T , Rehbinder H
Published: July 2008

Purpose: To demonstrate the first instance of the direct production of deliverable plans using multi‐objective IMRT treatment planning. Method and Materials: Three clinical IMRT cases are studied: a pancreas, prostate, and brain. The research software ORBIT Workstation is used to create a database of Pareto optimal treatment plans. For each case, N+1 plans are generated, where N is the number of objective functions. N=6, 8, and 9 for the pancreas, prostate, and brain, respectively. The N+1 plans are the N anchor points solutions (each objective individually minimized) and a single equally weighted solution. For all runs, a minimum dose to the target of approximately 90% of Rx dose is used as a constraint to ensure that each plan has some target coverage. The resulting plan database is navigated with a graphical user interface that allows users to improve any objective by appropriately mixing the plans in the database in real time. The final averaged plan is then used as the input to a dose matching algorithm in ORBIT, which achieves that plan using direct machine parameter optimization (DMPO). Results: We find that the database of size N+1 is adequate to explore the treatment tradeoffs and select a treatment plan. The selected plan can be reproduced with DMPO, and in fact the normal tissue sparing is typically improved during this step. Conclusion: Since smooth navigation of Pareto optimal plans involves averaging plans, navigation can be done only before the plans are sequenced. We demonstrate the success of a two step approach, where first plans are generated and navigated in beamlet space and then the selected mixed plan is made deliverable by a DMPO dose mimicking algorithm. Conflict of Interest: Work done in collaboration with RaySearch Laboratories.
SU‐GG‐T‐534: Investigation of Electron Beam Collimated by Motorized Electron Multi Leaf Collimator (eMLC) Designed for Fixed and Modulated Electron Beam Therapy
Authors: Eldib A , Jin L , Fan J , Lin T , Li J , Ma C
Published: July 2008

Purpose: Investigate the electron beam characteristics after been collimated by a motorized eMLC and study its feasibility for modulated electron radiation therapy. In addition we aimed at accurately simulating the eMLC and verify dose calculations for the inverse treatment planning system for MERT. Method and Materials: A motorized eMLC was developed for beam delivery for fixed beam delivery and MERT. The eMLC leafs are positioned at 82 cm source collimator distance. Film and ion chamber measurement were conducted in this study to investigate the characteristics of electron beam collimated by the eMLC. Measurement was done at 89 cm source surface distance allowing for 5cm gap between the eMLC and the surface of the phantom. Leakage from the eMLC was measured. Abutments of fields formed by eMLC were investigated. Comparison is also done between this new generation of motorized eMLC and our first generation of manually driven eMLC. Monte Carlo simulation was performed to accurately model the eMLC. Results: Profiles from the eMLC shows very close penumbra to that from the applicator for all energies. Film measurement showed that one leaf is still distinguished in a cross profile. In addition the leaf width is shown to be appropriate for defining a beamlet. Leakage from 16MeV beam through the eMLC was found to be 1.8%. The abutment fields showed enhancement at junction point which is blurred with depth. Good agreement was achieved between Monte Carlo simulations and measurements for profiles collimated by both electron applicators/cutouts and by the eMLC for all electron energies. Conclusion: The electron beam characteristics from the motorized eMLC were examined. Measurement done for this motorized eMLC showed promising results and a potential for modulated electron therapy. Monte Carlo code with the source represented by phase space files is capable of accurately modeling electron beam delivery with the eMLC.
SU‐GG‐T‐544: A Laser‐Ion Accelerator for Radiation Therapy Application
Authors: Ma C , Fourkal E , Veltchev I , Li J , Fan J , Lin T , Guemnie A
Published: July 2008

Purpose: This project is aimed at developing a practical laser‐particle radiation therapy system as an alternative to conventional accelerators for particle therapy. Method and Materials: A significant effort has been made through federal, industrial and institutional funding to develop cost‐effective alternatives to conventional accelerator‐based particle therapy. We have established a laser‐ion acceleration facility that consists of a commercial 150 TW laser, custom‐made laser‐pulse compression and target chambers, particle selection and beam collimating devices, dosimetry monitoring systems and shielding constructions. We have performed initial laser‐proton acceleration experiments with thin aluminum and plastic foils as target materials. The maximum proton energy was measured using CR‐39 film and a Thomson parabola ion analyzer. Particle‐in‐cell (PIC) simulations were carried out to investigate the optimal laser parameters and target configurations to facilitate laser‐proton acceleration and dosimetric studies. Results: The primary particles resulting from the laser‐target interaction are positive ions and electrons. Our initial testing with a 1018 W/cm2 laser intensity (at 20 TW) produced up to 4 MeV protons with a broad energy spectrum. PIC simulations confirmed these results demonstraing a scalability of the maximum ion energy and laser intensity. A compact shielding designed was investigated using Monte carlo simulations that allows for the installation of the particle therapy head on a small rotating gantry. Conclusion: An experimental laser‐ion accelerator has been established for radiation therapy studies and for future applications. Initial experimental studies have demonstrated proton acceleration at low laser power levels. Further studies with laser intensities up to 2 × 1020 W/cm2 are being conducted with different target materials and configurations.
SU‐GG‐T‐547: Optimization and Evaluation of Accuracy of Harvesting Backscattering Electrons Technique
Authors: Moskvin V , Kuros‐Zolnierczuk J , Cao M , Das I
Published: July 2008

Purpose: The applicability of harvesting backscattering electron for treatment of superficial small lesions of skin, oral cavity and rectum as described by Das et al., IJROBP, 33, 695, 1995 requires additional modification for the scattering angle optimization. The scattering angle by positioning the external scattering foil relative the irradiated surface is studied for scattering angle optimization for harvesting backscattering electrons. Method and Materials: Backscatter electrons were achieved from the primary electron beams of 6 MeV from a Varian accelerator. The chamber response as a function of lead foil as well as a chamber position angle was studied. The primary electrons were scattered off lead foil placed 120 cm from the source. A parallel plate ion chamber was placed 20 cm from foil. Results: Backscatter electrons have wide angular spread. The dose profile versus scattering angle showed a plateau that peaks around 30–60 degree. The chamber response was dependent on the lead angle with dose variation of 10–20% from chamber angle. It was found that the orientation of the chamber was optimum at 45–60 deg. This provides opportunity to optimize and harvest electrons for clinical use. Conclusion: The dose uniformity could be achieved for lead orientation angle from 30 to 60 deg. The prescription dose to 80 or 90% isodose can compensate the angular dependence of targeting point (chamber position), that will decrease influence of small variations in targeting area orientation. There is a maximum in delivered dose in the dependence of the foil orientation for a given position of targeting area. Although there are individual trend in the dependence of the chamber response of the lead position for each chamber position. However, the optimal angle of 60 deg for lead foil can be recommended. Additional work using Monte Carlo simulation for the optimization of foil angle is being carried out.
SU‐GG‐T‐548: Exclusion of Seminal Vesicles (SV) Spares Bladder More Than Rectum During IMRT for Prostate Cancer
Authors: Reddy N , Nori D , Ravi A , Sood B , Chang H
Published: July 2008

Purpose: To study the relationship between SV volumes versus dose to SV, rectum and bladder during 81 Gy IMRT to prostate, either excluding SV or including SV to 45 or 81 Gy. Method and Materials: SV, prostate, rectum and bladder were contoured on CT images. Proximal SV was defined as SV including 2‐cuts superior to prostate. Prescription with two IMRT plans was 45 and 36‐Gy to prostate+SV and to prostate, respectively, with 0.5–1 cm margins. Dose‐volume constraints were to keep dose to 70%, 50% and 30% of bladder and rectum less than 30%, 50% and 70% of 81‐Gy. Priority: PTV>rectum>bladder. DVH data from plans with no SV, or SV to 45 or to 81‐Gy were compared for 42 patients. Linear regression and paired ‘t’ test were used for statistical analysis. Results: Mean (±SD) and (range) of volumes (cc): SV: 11.7±5.14, (1.9–22.8); prostate: 53.3±24, (17.2–139); rectum: 124±24, (50–235), and bladder: 207±129, (25–561). Dose to rectum and bladder was not related to SV volumes (P>0.05). Inclusion of SV to 45‐Gy increased dose to rectum and bladder up to 30% but not at 10% volume. Dose (Gy) to 30% bladder, and rectum with no SV: B‐27.8±16.8, R‐40.4±6.7; SV to 45‐Gy: B‐35.6±14.2, R‐44±5.2; and SV to 81‐Gy: B‐42.4±14.7, R‐48.9±5.5, respectively. Excluding SV spared bladder (53%) more than rectum (21%) at 30% volume (P<0.001). Mean dose to SV to 45‐Gy: entire SV − 68.3±6 (57.4–79.4) and proximal SV − 74.5±2.5 (66.8–79.4). For small SV volumes, dose to bladder and rectum was same with SV to 45 or 81‐Gy. Conclusion: Margins, priority and inverse‐optimization might be reasons for sparing bladder more than rectum with SV exclusion during IMRT. Single plan to 81‐Gy for small SV cases would reduce planning and QA time to half. These results suggest reevaluation of reasons for inclusion/exclusion of SV during IMRT.
SU‐HH‐AUD C‐03: Machine Learning Tools for Predicting Clinical Complications in a Multi‐Plan IMRT Framework
Authors: Zhang H , Meyer R , Shi L , D'Souza W
Published: July 2008

Purpose: To apply machine learning algorithms to predict clinical outcomes (saliva flow rate, rectal bleeding, EUD, NTCP and PUC) for treatment plans taking into account dose and dose‐volume information. Method and Materials: One hundred twenty‐five (125) plans were generated for a representative head and neck case by varying the input dose‐volume constraints on the OARs (left parotid, right parotid and cord). The method that we used to predict continuous saliva flow rate from the treatment input constraint settings is a sequential minimal optimization algorithm for training a support vector regression model. Two hundred fifty‐six (256) plans were generated for the whole pelvis case by varying the input dose‐volume constraints on the rectum, bladder and bowel. We use the threshold of 66%/50Gy in conjunction with binary classification to predict rectal bleeding. The binary classification method employed is an optimized decision tree. We also calculated the EUD, NTCP, TCP and PUC for both 125 head and neck cases and 256 pelvic cases. Both Lyman‐Kutcher‐Burman (LKB) and Kallam and Agren‐Cronqvist's NTCP models were used. Both continuous and categorical values of these biological measures were predicted by modeling the planning surface using quadratic models and solving with linear programming with three different objective functions: minimizing maximum relative error, absolute error and sum of absolute errors. Results: We repeated the 10‐fold cross‐validation process 10 times and obtained a mean absolute error of 0.00078 with a 95% confidence interval [0.000769, 0.000792] for normalized saliva flow rate. We achieved an average correct prediction percentage of 97.35% and a 95% confidence interval for the correct prediction percentage as [96.89%, 97.81%]. Categorical correct prediction percentages for EUD, NTCP and PUC ranged from 75% to 96%. Conclusion: Our results indicate that machine learning techniques provide invaluable tools for the prediction of treatment complications from input constraints in a multi‐plan environment.
SU‐HH‐AUD C‐07: Classification of Breast Carcinoma Subtypes Using Computer‐Extracted Morphological and Kinetic Features in DCE‐MRI
Authors: Bhooshan N , Giger M , Chen W , Jansen S , Li H , Lan L , Newstead G
Published: July 2008

Purpose: To assess the performance of computer‐extracted morphological and kinetic features in differentiating different types of breast lesions, specifically ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC), in DCE‐MRI. Method and Materials: Breast MR images were obtained with a T1‐weighted SPGR sequence using Gd‐DTPA on a 1.5T GE MRI scanner. Each case has one precontrast and five postcontrast series at intervals of 68 seconds, and each series contains 60 coronal slices. The database contains 83 benign breast lesions and 98 malignant breast lesions including 24 DCIS, 32 IDC, 18 combined DCIS/IDC, 10 invasive lobular carcinoma (ILC) and 14 non‐categorizable lesions. All lesions were verified pathologically. Only pure DCIS and IDC lesions were used. Each lesion was segmented and its characteristic kinetic curve was extracted using the fuzzy c‐means method. Twenty‐nine features including textural, morphological, kinetic, and variance kinetic features were extracted and stepwise linear discriminant analysis using a Wilks lambda cost function was used for feature selection. The selected features were merged using round‐robin Bayesian neural network and the classification performance was evaluated using receiver‐operating characteristics (ROC) analysis. Results: Distinguishing DCIS lesions from IDC lesions using selected features gave an AUC value of 0.95. AUC values of 0.85 and 0.87 were obtained in differentiating between DCIS and benign lesions, and between IDC and benign lesions with merged features, respectively. Conclusion: Computer‐aided diagnosis for breast MRI can be extended from malignant vs. benign classification to distinguishing different subcategories of breast carcinomas, in particular DCIS and IDC.
SU‐HH‐AUD C‐10: The Imaging and Dosimetric Capabilities of a Novel CT/MR‐Suitable, Anatomically Adaptive, Shielded HDR/PDR Intracavitary Brachytherapy Applicator for the Treatment of Cervical Cancer
Authors: Price M , Eifel P , Gifford K , Zhang M , Followill D , Gillin M , Mourtada F
Published: July 2008

Purpose: To design and investigate the imaging and dosimetric capabilities of a novel, CT/MR‐suitable, anatomically adaptive, shielded cervical HDR/PDR brachytherapy applicator. Method and Materials: An applicator was constructed featuring an inter‐colpostat shield that can translate/rotate about the colpostat's long‐axis. Artifact‐free CT imaging was achieved using a “step‐and‐shoot” technique; pausing the scanner midway through the scan and moving the shield out of the beam's path. Artifact‐free MRI imaging was achieved by utilizing MRI‐compatible ovoid components and pulse‐sequences that minimize susceptibility artifacts. The applicator's imaging capabilities were demonstrated acquiring images using phantoms that positioned the novel and Fletcher‐Williamson ICBT applicators in clinically‐applicable geometries for both modalities. Artifacts were qualitatively compared. To evaluate any dosimetric advantages, Monte‐Carlo models of the novel and FW applicators were first validated. Anatomies of patients that have undergone ICBT for cervical disease were modeled using Monte‐Carlo and spatially registered with models of both applicators using SolidWorks; a CAD software suite. Equivalent, clinically‐applicable loadings were simulated for both applicators using Monte‐Carlo techniques. The novel applicator shield's rotation and translation was adjusted for each dwell position in order to minimize dose to the rectum and superimposed for comparison to equivalent FW treatments. Rectal dose (rate and absolute) volume histograms were determined for both applicators and compared. Results: Using a “step‐and‐shoot” CT scanning method and MR compliant materials and optimal pulse‐sequences, images of the novel applicator were artifact‐free using both modalities. Additionally, for the patient case presented, there is a 26% and 13% reduction of d90 and d50, respectively, and a 13% reduction in overall absolute dose to the rectum when compared to equivalent Fletcher‐Williamson ICBT treatments. Conclusion: A novel ICBT applicator can be imaged using CT/MR without artifact and reduce dose to the rectum compared to the current state‐of‐the‐art, FW ICBT applicator. Conflict‐of‐Interest: Work partially supported by Nucletron Corp.
MO‐A‐350‐01: Out‐Of‐Field Dosimetry for Secondary Cancer Studies: Past Experience and Future Needs
Authors: Xu X George , Followill David
Published: July 2008

Patients treated with ionizing radiation carry a risk of developing second cancers in their life times. Factors contributing to the recently renewed concern about this risk include improved cancer survival rates, younger patient pool, as well as emerging treatment modalities such as IMRT and proton therapy that can potentially prolong secondary exposures to healthy tissues or expose patients to neutrons. In the past 20 years, external beam treatment technologies have evolved significantly, and there is an overwhelming amount of data on both dosimetry and epidemiological studies. This lecture reviews historical studies related to the assessment of scatter and leakage radiation from classical radiation therapy, 3D‐Conformal x‐ray therapy, intensity‐modulated x‐ray therapy (IMRT and tomotherapy), and proton therapy. The concept of high‐, intermediate‐ and low‐dose regions outside the primary treatment field is introduced. Terms such as “secondary cancers,” “organ‐average equivalent dose,” “out‐of‐field,” and “peripheral dose” are reviewed. Comparison of secondary doses from different treatment modalities, make/energy of accelerator and for adult and pediatric treatments is also made. Concomitant dose from IGRT localization and verification procedures involving cone‐beam CT is briefly discussed. This is followed by a detailed review on methods of performing measurements in physical phantoms using different types of radiation detectors, as well as Monte Carlo simulations using gender‐ and age‐specific “virtual patient” computational models. Finally future needs on dosimetry and epidemiological studies are discussed.

Educational Objectives:

1. Understand the importance of secondary cancer risk in radiation treatment.

2. Understand basic concepts in radiation dosimetry associated with secondary cancer studies.

3. Understand practical methods of measurement and Monte Carlo simulation for the assessment of organ‐average equivalent doses for various treatment modalities.
MO‐A‐AUD A‐01: Review of AAPM Task Group Report No. 105
Authors: Chetty IJ , Rogers DWO
Published: July 2008

A special class of Monte Carlo (MC)‐based dose calculation codes optimized for photon and electron beams in patient‐specific geometries has invigorated interest in the use of MC‐based dose calculations for radiotherapy treatment planning. In general, this class of “second generation” codes, including VMC++, XVMC, and DPM, among others, employ electron‐step algorithms that converge faster, i.e. fewer condensed‐history steps are required for the same precision versus “first‐generation” codes (such as EGS and MCNP). These advances, coupled with the use of sophisticated variance reduction techniques (e.g. directional bremsstrahlung splitting), have made it possible to perform MC‐based photon beam dose calculations, in some instances, of the entire linear accelerator treatment head and patient‐geometry, within minutes on a single processor. Consequently, several commercial vendors have released or are currently in the process of releasing MC algorithms for photon and/or electron beam treatment planning. With the impending availability of MC‐based dose calculation algorithms for routine clinical treatment planning, it is important that strategies and paradigms for clinical commissioning and implementation of these systems be formulated and discussed. We provide a review of AAPM Task Group Report No. 105 (Med. Phys. 34 (2007) 4818–4853), a document which outlines the important aspects of a MC‐based dose calculation algorithm, from the basic aspects of the use of the MC method for radiation transport to the application of this approach in routine clinical photon and electron beam treatment planning.

Educational Objectives:

1. To provide an educational review of the physics of the MC method including discussion of the approaches used for coupled photon and electron transport.

2. To review the methods used to improve the MC simulation efficiency.

3. To briefly review the vendor transport codes currently used for clinical treatment planning.

4. To describe the development of beam models for clinical treatment planning.

5. To discuss the factors associated with MC dose calculation within the patient‐specific geometry, such as statistical uncertainties, CT‐number to material density assignments, and reporting of dose‐to‐medium versus dose‐to‐water.

6. To discuss the issues associated with experimental verification of MC algorithms.

7. To briefly review the potential clinical implications of MC calculated dose distributions.

8. To provide example timing comparisons of the major vendor MC codes in the clinical setting.
MO‐A‐AUD C‐02: Clinical Implementation of Respiration Motion Correlated Imaging, Treatment Planning and Delivery
Authors: Vedam S
Published: July 2008

Respiratory motion is a significant factor in determining a suitable planning target volume (PTV) that surrounds the demonstrable gross tumor volume (GTV) in the radiotherapy of mobile lesions. The advent of respiratory phase correlation (4D) and multi‐slice CT technology has enabled patient‐specific determination of both demonstrable tumor volume and its motion from a single acquisition. Management of such additional information during treatment planning and delivery however presents several challenges. Furthermore, guidelines for establishing clinical treatment planning and delivery protocols based on respiratory correlated imaging data differ from one institution to the other. The purpose of this presentation is to educate the community on the different respiratory correlated radiotherapy approaches currently available and compare the benefits and pitfalls in each case. Special focus will be on treatment planning, dose calculation and treatment delivery related issues.

Educational Objectives:

1. Understand the different respiratory correlated treatment planning and delivery approaches.

2. Compare the benefits and pitfalls of each of the above approaches.

3. Develop and establish respiratory correlated imaging, treatment planning and delivery appropriate to the available equipment.
MO‐A‐351‐01: Digital Mammography Update: Design and Characteristics of Current Systems
Authors: Kanal K
Published: July 2008

Full Field Digital Mammography (FFDM) systems are fast becoming popular and replacing conventional film‐screen mammography systems. FFDM systems use a digital detector instead of screen‐film to capture the image of the breast. Several FFDM systems based on different digital detector design and materials are currently available. Some systems are characterized as direct conversion detectors and some are based on indirect conversion process. The digital detectors can be characterized by image quality metrics such as detector quantum efficiency (DQE) and modulation transfer function (MTF).

In this lecture, the physics and technology of the digital detectors used in FFDM will be discussed as well as the advantages and applications arising due to the availability of these systems will be presented. The most recent commercially available systems will also be discussed.

Educational Objectives:

1. Understand the physics of digital detector technology.

2. Understand the image quality metrics such as DQE and MTFRecognize that vendors use varying detector technology in FFDM systems.

3. Appreciate the advantages and disadvantages of digital mammography systems.
MO‐SAMS‐332‐02: Introduction to Magnetic Resonance Spectroscopy of Breast and Prostrate Cancer: Current Applications
Authors: Jacobs MA
Published: July 2008

Magnetic resonance spectroscopy (MRS) and magnetic resonance spectroscopy imaging (MRSI) is increasing being utilized as adjuncts for differentiating benign from malignant lesions in the clinical setting. MRS has the ability to probe intracellular metabolites, such as, choline (Cho), Creatine (Cr), citrate (Ci) and N‐acetylaspartate (NAA). The observation of a high Choline signal appears to be the spectroscopic hallmark of cancer. This additional information can be very useful in cases of indeterminate findings in suspicious lesions, for example, in breast or prostrate cancer. Indeed, recent advances have moved the use MRS into the clinical realm for detection and classification of these tumors and more importantly, monitoring response to neoadjuvant chemotherapy treatment. This presentation will review the principles of MRS, including, pulse sequences, MRS data collection, data analysis, quantification, and quality assurance. Three major topics are considered. Introduction of relevant intracellular metabolites and their biological and medical significance in cancer, the principles underlying each quantity are given. Second, major pulse sequences used for MRS, e.g., PRESS or STEAM in breast and prostrate cancer. Finally, MRS data analysis and quantification of the results with pathological observations will be also compared with MRS‐derived quantities where appropriate.

This presentation is intended as an introduction to the field of MRS for anyone who desires to use the scope of modern MRS techniques, its application and use for monitoring therapy. It will be of interest to medical physicists who are considering undertaking quantitative MRS, as well as those already in the field.

Educational Objectives:

1. Identify the clinically important quantities (e.g. metabolites) that can be measured with MRS.

2. Be familiar with the methods and techniques used for MRS acquisition.

3. Basic understanding of the application of MRS to breast and prostrate cancer.
MO‐B‐342‐01: Magnitude of Medical Radiation Exposures to US Population with Focus On CT and Nuclear Medicine Doses
Authors: Mahesh M
Published: July 2008

This presentation will examine the current trends in medical x‐ray imaging procedures in the United States. It will also examine the magnitude of radiation doses for various x‐ray imaging procedures. Special emphasis will be given to CT and nuclear medicine procedures.

The results are based on the work done within the framework of National Council of Radiation of Protection Scientific Committee 6.2 formed to work on the estimation of radiation exposure to the US population from all sources. The intended goal of the Committee is to update the NCRP report 93 published in 1987. The subcommittee examined variety of data sources including commercial surveys, Medicare, Veterans Administration and insurance carrier data. Radiation exposure to the US population from medical exposures was then estimated based on the number of medical procedures grouped by modality and body parts and the radiation doses associated with each procedure.

According to the preliminary results, the medical radiation exposure to US population has increased by nearly 5.5 times compared to the previous NCRP publication (NCRP 93). The largest contributor to the collective dose to US population is seen with CT and Nuclear Medicine procedures. It is found that the CT procedures accounts for 14% of all medical x‐ray imaging procedures but contribute to nearly 49% of collective dose to US population. Similarly, the nuclear medicine procedure accounts to only 4% of all procedures but contribute to nearly 26% of collective dose to US population.

Educational Objectives:

1. To familiarize with the types and distribution of medical imaging procedures in US.

2. To learn the magnitude of medical radiation exposure to US population.

3. To examine the magnitude and distribution of procedures and doses from CT.
MO‐E‐332‐07: Instrumentation Noise Equivalent Exposure (INEE) for Routine Quality Assurance: INEE Measurements On a Clinical Flat Panel Detector
Authors: Szczykutowicz T , Kuhls‐Gilcrist A , Bednarek D , Rudin S
Published: July 2008

Purpose: To measure the instrumentation‐noise equivalent exposure (INEE) of a clinical digital imaging system under various modes of operation. Method and Materials: The INEE is defined as the exposure at which the quantum‐noise equals the instrumentation‐noise and is measured from the plot of pixel gray‐level‐value variance versus detector entrance exposure. The intercept of such a plot represents the instrumentation‐noise in gray‐level values and the slope provides the conversion factor from these arbitrary units to equivalent exposure. Sequences of 90 flat‐field images in DA and DSA modes were acquired at 1 frame‐per‐second using a Varian PaxScan 2020 flat panel detector, both with image processing enabled and disabled. Image receptor input exposure was measured using an ionization chamber and effects of uncertainties in exposure calibration on the resulting INEE were investigated. Results: The INEE was observed to vary depending on the mode used and was measured to be 0.9±0.2 and 44±6 μR in DA and DSA modes, respectively, with image processing disabled. Exposure calibration error will result in additional proportionate INEE error. With image processing enabled the variance was highly nonlinear with exposure in DA mode indicating a need to have access to linear, unprocessed data. The difference in integration capacitance between DA and DSA modes, 0.5 and 4 pF respectively, helps explain the change in the INEE between these modes. Conclusion: INEE measurements were done on a clinical digital image receptor and were found to be dependent on the operational mode used. The importance of disabling image processing during INEE measurement was demonstrated. Due to the ease in gathering and analyzing the necessary data, we found the INEE to be a useful quality assurance tool for assessing a system's instrumentation‐noise in terms of a clinically relevant measure of exposure. (Support: NIH Grants R01‐ NS43924, R01‐EB002873, Toshiba Medical Systems Corporation).
MO‐E‐352‐01: CR Mammography — What You Need to Know
Authors: Martin M
Published: July 2008

The approval by the FDA of the Fuji FCRm in November 2006 allowed many facilities the opportunity to enter the era of Full‐Field digital imaging in mammography while utilizing their existing equipment previously using a film/screen imaging system. Although the mammography equipment producing the images spans the complete range of currently approved units from systems more than 10 years old to relatively new units, the image quality requirements for the Fuji FCRm system is independent of the equipment used to produce the images. The qualified medical physicist providing services to these facilities must be familiar with all aspects of the FCRm system to set up and oversee the Quality Control Requirements and to complete the required acceptance test procedures. This workshop will cover the required tests and evaluations of the FCRm system to be performed by the physicist covering the image producing equipment, the softcopy review workstations and the laser printer. Practical tips for performing these tests will be presented along with suggested worksheets.

Educational Objectives:

1. Attendees will know the Annual Tests required to be performed by the medical physicist to meet MQSA and ACR accreditation requirements.

2. Attendees will be aware of methods to be used to perform the required tests of the Fuji FCRm system to meet accreditation requirements.

3. Attendees will know the acceptable range of values required for each of the tests to be performed by the medical physicist to meet accreditation requirements and values to be used to establish the ongoing Quality Control program.
TU‐A‐AUD C‐01: Margins in Radiation Therapy
Authors: Low DA , Litzenberg DW
Published: July 2008

Conformal radiation therapy has historically used margins to account for geometrical uncertainties in the position of a target volume. The margins, in their simplest form, are simply expansions to the shape of a treatment beam, to ensure that dosimetric planning criteria are met in the presence of inter‐ and intra‐fraction setup variations. Historically, the size of the margin in a given treatment site was difficult to determine due to the available technology and the time and effort required to obtaining accurate data. Consequently, margins were estimated to accommodate a population of patients. As new technologies have emerged, target volume position errors have become easier to measure, their accuracy has increased, and the measurements can be made much more frequently. As the quantity and quality of data has increased for patient populations, and even for individual patients, the conceptual basis of employing margins has evolved. Strategies for ensuring dosimetric coverage may now be individualized to a specific patient's geometric uncertainty characteristics with customized margins, or they may incorporate geometric correction based on predefined action levels. Other strategies may incorporate continuous monitoring to gate or modify the beam. And finally, other strategies seek to eliminate margins by including the estimated geometrical uncertainty into the development of the dose distribution.

Educational Objectives:

1. To provide an educational review of the technologies and methods of measuring target volume positioning errors.

2. To review methods of determining population margins from measured data.

3. To review corrective and intervention strategies for patients with individualized margins.

4. To briefly review planning strategies which seek to eliminate margins.

Conflict of Interest: DA Low: Research sponsored by Tomotherapy and Varian; DW Litzenberg: Research sponsored by Calypso Medical Technologies, Inc.
TU‐SAMS‐332‐02: Digital Mammography Detector QC, Tips and Problems
Authors: Berns E
Published: July 2008

Digital mammography is quickly becoming the technology of choice for breast imaging with several FDA‐approved systems already available and more on the way. Digital detectors in mammography have different characteristics compared to the traditional screen‐film systems and require by the FDA different Quality Control tests. This lecture is going to discuss the practical issues for the medical physicist who wants to learn the differences in these Quality Control tests and how they impact the mammography facility and ACR accreditation. The lecture will be broken into several parts. The first will review currently available FFDM equipment and their respective Quality Control tests. The second part will compare similar QC tests and discuss the key differences. The third part will review quality control for review workstations and laser printers designed for digital mammography.

Educational Objectives:

1. To describe current quality control procedures for FFDM systems.

2. To describe current quality control procedures for review workstations in digital mammography.

3. To describe current quality control procedures for laser printers in digital mammography.

4. To review the impact of QC on ACR accreditation for FFDM systems.
TU‐A‐342‐01: Quality Assurance Testing of Gamma Camera and SPECT Systems
Authors: Halama J
Published: July 2008

Routine maintenance, calibration, and quality control of gamma camera and SPECT imaging systems is crucial for providing the nuclear physician or radiologist images of high quality without artifact. This lecture will provide an overview of the gamma camera and SPECT calibrations, performance measurements, and quality assurance tests, whether they are for routine quality control or annual physics surveys as defined by the ACR accreditation program. A discussion of common artifacts and how to avoid and correct them will be included.

Gamma camera and SPECT performance measurements are well defined in documents published by MITA/NEMA and in AAPM Task Group reports. Unfortunately, many of the specified tests cannot be easily done on installed systems in the field. Modifications become necessary, and as a result performance measurements and quality assurance testing of gamma camera and SPECT systems have been quite variable. Not included in the published documents are calibration procedures that are vendor specific. Improper calibrations, particularly uniformity calibration, also lead to unwanted artifacts. It is the burden of the physicist to know which performance tests are critical in the field and to also become familiar with specific calibration procedures of our gamma camera and SPECT systems.

Educational Objectives:

1. Learn the basic gamma camera and SPECT performance measurements and quality assurance test procedures.

2. Become familiar with calibration procedures of current systems.

3. Become familiar with the test procedures and the frequency of testing prescribed by the ACR accreditation programs.

4. Be able to identify common gamma camera and SPECT image artifacts and how to correct them.
TU‐B‐AUD C‐01: Deformable Image Registration: Methods and Clinical Endpoints
Authors: Kessler M
Published: July 2008

Acquisition of anatomic and functional data from magnetic resonance imaging and nuclear medicine studies is becoming increasingly common for patient management in radiation therapy. These data can help improve tumor localization and normal tissue delineation for treatment planning and may provide information about treatment efficacy during or after a course of radiotherapy. Time series data from serial and 4D CT before and during the treatment course, including CT data acquired in the treatment room at the time of treatment, is also helping to estimate motion and shape changes of relevant anatomy. In order to fully realize the benefits of these data, the different imaging studies must be registered to each other or to a common coordinate system. The geometric transformation required to register the different image data can range from simple rotate‐translate to account for differences in patient orientation to 3D or 4D deformation models to account for changes in internal anatomy during and over the course of therapy. Once registered, data derived from the various studies such as anatomic outlines and computed dose can be integrated or fused to help construct a more complete and accurate representation of the patient.

This lecture will focus on the mechanics of registering and displaying data from different imaging studies using distinct modalities or a single modality over time. A taxonomy of the different methods will be described. Methods for display and interaction with multimodality data will also be presented. The overall goal is to provide the basic knowledge required to understand what is happening “under‐the‐hood” of the different registration systems one might encounter in the clinic, the different ways these systems are being used for patient management and their limitations.

Educational Objectives:

1. Understand the basic mechanics of deformable image registration and data fusion techniques.

2. Understand the tools used to combine, display & interact with multimodality/4D image and dose data.

3. Understand the clinical use and limitations of these techniques for Tx planning, Tx delivery and plan adaptation.