bluuebunny/crossref_metadata_2025_split huggingface dataset:
TH‐E‐BRF‐01: Exploiting Tumor Shrinkage in Split‐Course Radiotherapy
Authors: Unkelbach J , Craft D , Hong T , Papp D , Ramakrishnan J , Salari E , Wolfgang J , Bortfeld T 
Published: July 2014

Purpose:In split‐course radiotherapy, a patient is treated in several stages separated by weeks or months. This regimen has been motivated by radiobiological considerations. However, using modern image‐guidance, it also provides an approach to reduce normal tissue dose by exploiting tumor shrinkage. In this work, we consider the optimal design of split‐course treatments, motivated by the clinical management of large liver tumors for which normal liver dose constraints prohibit the administration of an ablative radiation dose in a single treatment.Methods:We introduce a dynamic tumor model that incorporates three factors: radiation induced cell kill, tumor shrinkage, and tumor cell repopulation. The design of splitcourse radiotherapy is formulated as a mathematical optimization problem in which the total dose to the liver is minimized, subject to delivering the prescribed dose to the tumor. Based on the model, we gain insight into the optimal administration of radiation over time, i.e. the optimal treatment gaps and dose levels.Results:We analyze treatments consisting of two stages in detail. The analysis confirms the intuition that the second stage should be delivered just before the tumor size reaches a minimum and repopulation overcompensates shrinking. Furthermore, it was found that, for a large range of model parameters, approximately one third of the dose should be delivered in the first stage. The projected benefit of split‐course treatments in terms of liver sparing depends on model assumptions. However, the model predicts large liver dose reductions by more than a factor of two for plausible model parameters.Conclusion:The analysis of the tumor model suggests that substantial reduction in normal tissue dose can be achieved by exploiting tumor shrinkage via an optimal design of multi‐stage treatments. This suggests taking a fresh look at split‐course radiotherapy for selected disease sites where substantial tumor regression translates into reduced target volumes.
TH‐E‐BRF‐09: Gaussian Mixture Model Analysis of Radiation‐Induced Parotid‐Gland Injury: An Ultrasound Study of Acute and Late Xerostomia in Head‐And‐Neck Radiotherapy
Authors: Liu T , Yu D , Beitler J , Tridandapani S , Bruner D , Curran W , Yang X 
Published: July 2014

Purpose:Xerostomia (dry mouth), secondary to parotid‐gland injury, is a distressing side‐effect in head‐and‐neck radiotherapy (RT). This study's purpose is to develop a novel ultrasound technique to quantitatively evaluate post‐RT parotid‐gland injury.Methods:Recent ultrasound studies have shown that healthy parotid glands exhibit homogeneous echotexture, whereas post‐RT parotid glands are often heterogeneous, with multiple hypoechoic (inflammation) or hyperechoic (fibrosis) regions. We propose to use a Gaussian mixture model to analyze the ultrasonic echo‐histogram of the parotid glands. An IRB‐approved clinical study was conducted: (1) control‐group: 13 healthy‐volunteers, served as the control; (2) acutetoxicity group − 20 patients (mean age: 62.5 ± 8.9 years, follow‐up: 2.0±0.8 months); and (3) late‐toxicity group − 18 patients (mean age: 60.7 ± 7.3 years, follow‐up: 20.1±10.4 months). All patients experienced RTOG grade 1 or 2 salivary‐gland toxicity. Each participant underwent an ultrasound scan (10 MHz) of the bilateral parotid glands. An echo‐intensity histogram was derived for each parotid and a Gaussian mixture model was used to fit the histogram using expectation maximization (EM) algorithm. The quality of the fitting was evaluated with the R‐squared value.Results:(1) Controlgroup: all parotid glands fitted well with one Gaussian component, with a mean intensity of 79.8±4.9 (R‐squared>0.96). (2) Acute‐toxicity group: 37 of the 40 post‐RT parotid glands fitted well with two Gaussian components, with a mean intensity of 42.9±7.4, 73.3±12.2 (R‐squared>0.95). (3) Latetoxicity group: 32 of the 36 post‐RT parotid fitted well with 3 Gaussian components, with mean intensities of 49.7±7.6, 77.2±8.7, and 118.6±11.8 (R‐squared>0.98).Conclusion:RT‐associated parotid‐gland injury is common in head‐and‐neck RT, but challenging to assess. This work has demonstrated that the Gaussian mixture model of the echo‐histogram could quantify acute and late toxicity of the parotid glands. This study provides meaningful preliminary data from future observational and interventional clinical research.
TH‐E‐17A‐02: High‐Pitch and Sparse‐View Helical 4D CT Via Iterative Image Reconstruction Method Based On Tensor Framelet
Authors: Guo M , Nam H , Li R , Xing L , Gao H 
Published: July 2014

Purpose:4D CT is routinely performed during radiation therapy treatment planning of thoracic and abdominal cancers. Compared with the cine mode, the helical mode is advantageous in temporal resolution. However, a low pitch (∼0.1) for 4D CT imaging is often required instead of the standard pitch (∼1) for static imaging, since standard image reconstruction based on analytic method requires the low‐pitch scanning in order to satisfy the data sufficient condition when reconstructing each temporal frame individually. In comparison, the flexible iterative method enables the reconstruction of all temporal frames simultaneously, so that the image similarity among frames can be utilized to possibly perform high‐pitch and sparse‐view helical 4D CT imaging. The purpose of this work is to investigate such an exciting possibility for faster imaging with lower dose.Methods:A key for highpitch and sparse‐view helical 4D CT imaging is the simultaneous reconstruction of all temporal frames using the prior that temporal frames are continuous along the temporal direction. In this work, such a prior is regularized through the sparsity transform based on spatiotemporal tensor framelet (TF) as a multilevel and high‐order extension of total variation transform. Moreover, GPU‐based fast parallel computing of X‐ray transform and its adjoint together with split Bregman method is utilized for solving the 4D image reconstruction problem efficiently and accurately.Results:The simulation studies based on 4D NCAT phantoms were performed with various pitches (i.e., 0.1, 0.2, 0.5, and 1) and sparse views (i.e., 400 views per rotation instead of standard >2000 views per rotation), using 3D iterative individual reconstruction method based on 3D TF and 4D iterative simultaneous reconstruction method based on 4D TF respectively.Conclusion:The proposed TF‐based simultaneous 4D image reconstruction method enables high‐pitch and sparse‐view helical 4D CT with lower dose and faster speed.
TH‐E‐17A‐03: Development and Evaluation of a 4D‐CBCT Scheme Based On Simultaneous Motion Estimation and Image Reconstruction
Authors: Dang J , Gu X , Ouyang L , Pan T , Wang J 
Published: July 2014

Purpose:To develop and evaluate the performance of a novel 4D‐CBCT reconstruction scheme based on simultaneous motion estimation and image reconstruction (SMEIR) through patient studies.Methods:The SMEIR algorithm consists of two alternating steps: 1) motion‐compensated CBCT reconstruction; and 2) motion model estimation from the projections directly. In step 1, projections from all phases are used to reconstruct a reference phase 4D‐CBCT by explicitly considering the motion models between different phases. In step 2, updated inverse consistent motion models are obtained directly from projections by matching the measured projections to the forward projection of the deformed reference phase 4D‐CBCT. Motion model estimation was implemented on GPU to increase the computation efficiency. Two lung cancer patients were scanned for 4.5 and 5.7 minutes. Totally 1679 and 1982 projections were acquired and grouped into 10 phases. To evaluate SMEIR algorithm performance on conventional 1‐minute CBCT scan, projections at each phase were down‐sampled by factors ranging from 2 to 10. 4D‐CBCT were reconstructed from down‐sampled projections using FDK, total variation minimization (TV) and SMEIR. Using 4D‐CBCT reconstructed from fully sampled projections as a reference, relative errors of image and tumor motion trajectory were analyzed to quantify performances of different reconstruction algorithms.Results:SMEIR algorithm outperforms FDK and TV in both reconstruction accuracy and tumor tracking accuracy. When averaged projection number per phase decreases to 18 in two patients, relative reconstruction errors for FDK, TV and SMEIR are 38.00%, 11.72% and 9.59%, respectively. The maximum tumor tracking errors are 2.53 mm, 2.05 mm, and 0.68 mm for FDK, TV and SMEIR, respectively.Conclusion:Patient studies show that the SMEIR algorithm achieves 1‐mm tumor tracking accuracy when the average projection number per phase reduces to 18. SMEIR algorithm enables the use of conventional 1‐minute CBCT for accurate motion modeling and 4D‐CBCT reconstruction.
TH‐E‐17A‐08: Estimation of Image Quality of 4‐Dimensional Computed Tomography (4DCT) Via Fourier Analysis of Corresponding 1D Breathing Surrogate
Authors: Caraveo M , Wei J , McNamara J , Rimner A , Yorke E , Li G 
Published: July 2014

Purpose:Motion artifacts are common in patient 4DCT, leading to an illdefined tumor volume with variation up to 110% or setting up a poor foundation with low imaging fidelity for tumor motion study. We developed a method to estimate 4DCT image quality by establishing a correlation between the severity of motion artifacts in 4DCT images and the periodicity of corresponding 1D respiratory wave‐function (1DRW) surrogate used for 4DCT reconstruction.Methods:Fast Fourier Transformation (FFT) was applied to analyze 1DRW periodicity, defined as the sum of the 5 largest Fourier coefficients, ranging in 0–1. Distortional motion artifacts of cine‐scan 4DCT at the junctions of adjacent couchposition scans around the diaphragm were identified in 3 categories: incomplete, overlapping and duplicate. To quantify these artifacts, the discontinuity of the diaphragm at the junctions was measured in distance and averaged along 6 directions in 3 orthogonal views. Mean and sum artifacts per junction (APJ) across the entire diaphragm were calculated in each breathing phase. To make the APJ inter‐patient comparable, patientspecific motion was removed from APJ by dividing patient‐specific diaphragmatic velocity (displacement divided by the mean period, from FFT analysis of the 1DRW) and the normalized APJ was defined as motion artifact severity (MAS). Twenty‐five patients with free‐breathing 10‐phase 4DCT and corresponding 1DRW surrogate datasets were studied.Results:A mild correlation of 0.56 was found between 1DRW periodicity and 4DCT artifact severity. Higher MAS tends to appear around mid inhalation and mid exhalation and the lowest MAS tends to be around full exhalation. The breathing periodicity of >0.8 possesses minimal motion artifacts.Conclusion:The 1D‐4D correlation provides a fast means to estimate 4DCT image quality. Using 1DRW signal, we can retrospectively screen out high‐quality 4DCT images for clinical research (periodicity>0.8) and prospectively identify poor breathers as candidates of breath coaching prior to 4DCT scan.This research is in part supported by NIH (U54CA137788/132378). MC would like to thank MSKCC summer medical student research program supported by National Cancer Institute and hosted by Department of Medical Physics at MSKCC.
TH‐E‐17A‐10: Markerless Lung Tumor Tracking Based On Beams Eye View EPID Images
Authors: Chiu T , Rozario T , Bereg S , Klash S , Kearney V , Liu H , Jiang L , Foster R , Mao W 
Published: July 2014

Purpose:Dynamic tumor tracking or motion compensation techniques have proposed to modify beam delivery following lung tumor motion on the flight. Conventional treatment plan QA could be performed in advance since every delivery may be different. Markerless lung tumor tracking using beams eye view EPID images provides a best treatment evaluation mechanism. The purpose of this study is to improve the accuracy of the online markerless lung tumor motion tracking method.Methods:The lung tumor could be located on every frame of MV images during radiation therapy treatment by comparing with corresponding digitally reconstructed radiograph (DRR). A kV‐MV CT corresponding curve is applied on planning kV CT to generate MV CT images for patients in order to enhance the similarity between DRRs and MV treatment images. This kV‐MV CT corresponding curve was obtained by scanning a same CT electron density phantom by a kV CT scanner and MV scanner (Tomotherapy) or MV CBCT. Two sets of MV DRRs were then generated for tumor and anatomy without tumor as the references to tracking the tumor on beams eye view EPID images.Results:Phantom studies were performed on a Varian TrueBeam linac. MV treatment images were acquired continuously during each treatment beam delivery at 12 gantry angles by iTools. Markerless tumor tracking was applied with DRRs generated from simulated MVCT. Tumors were tracked on every frame of images and compared with expected positions based on programed phantom motion. It was found that the average tracking error were 2.3 mm.Conclusion:This algorithm is capable of detecting lung tumors at complicated environment without implanting markers. It should be noted that the CT data has a slice thickness of 3 mm. This shows the statistical accuracy is better than the spatial accuracy.This project has been supported by a Varian Research Grant.
TH‐E‐17A‐11: Tracking Tumor’s Boundary in MV Image Sequences for Image‐Guided Radiation Therapy
Authors: Zhang X , Homma N , Narita Y , Takai Y , Ichiji K , Abe M , Sugita N , Yoshizawa M 
Published: July 2014

Purpose:To develop a level set method (LSM)‐based algorithm to track the tumor’s boundary in MV image sequences for image‐guided radiation therapy (IGRT).Method:Four MV image sequences, each of which consists of 100 frames at frame rate of 7.5 Hz, are acquired by using the electronic portal imaging device (EPID) (Varian Medical Systems, Pal Alto, USA) during the treatment of lung cancer. In the first frame of each sequence, we roughly delineate an initial contour of the target tumor by hand. Using a LSM‐based algorithm, the initial contour can automatically shape itself to fit the tumor, and eventually detect the tumor’s boundary. We then employ the tumor’s boundary obtained from the previous frame as the initial contour in the subsequent frame, so that the LSM‐based method can drive this initial contour to the tumor’s boundary quickly and fulfill a tracking task.Results:The proposed method has been evaluated on four MV image sequences. The mean tracking errors were 0.23, 0.29, 0.37, and 1.18 mm, and their corresponding standard deviations were 0.97, 0.75, 1.2 and 1.48 mm, respectively.Conclusion:Compared with conventional tumor tracking techniques, the proposed system is capable not only of tracking the tumor’s position, but also of detecting the tumor’s boundary varying with the respiration during the treatment. Considering current radiation therapy technique, for example, dynamical multi‐leaf collimator (DMLC) has been widely applied in clinical treatment, this study indicates the potential for significant accuracy improvement in radiation therapy.This work was partially supported by a research grant from Varian Medical Systems (Palo Alto, California).
SU‐A‐BRF‐01: Education Council Symposium: Online Education in Medical Physics
Authors: Dobbins J , Prisciandaro J , Bloch C , Gingold E , Starkschall G , Oldham M , Sprawls P , Xiao Y 
Published: July 2014

Online education is rapidly becoming an important means of communicating content in educational activities across a broad spectrum of fields, including medical physics. We are currently at a point of broad change in educational strategies and methodologies, and the use of online content is likely to play an increasingly important role in medical physics education going forward. This symposium, sponsored by the AAPM Education Council, will consider the current state of online educational opportunities in medical physics as well as what options may become available in the near future.Specific topics to be covered include an overview of the scope and opportunity of online education in medical physics; current resources including available online content, the AAPM Virtual Library and Online Learning Center, AAPM/RSNA online educational modules, and software tools for creating online content; and considerations of future uses of massively‐open online courses in medical physics education. Finally, a collaborative model of medical physics education using online resources will be described.Learning Objectives:

Understand the range of opportunities available for online education in medical physics
Learn of existing resources available for medical physics education
Understand how to use software tools to create online educational content
Understand a collaborative model of medical physics education using online resources
SU‐C‐16A‐03: Direction Modulated Brachytherapy for HDR Treatment of Cervical Cancer
Authors: Han D , Webster M , Scanderbeg D , Yashar C , Choi D , Song B , Devic S , Ravi A , Song W 
Published: July 2014

Purpose:To investigate a new Directional Modulated Brachytherapy (DMBT) intra‐uterine tandem using various 192‐Ir after‐loaders.Methods:Dose distributions from the 192‐Ir sources were modulated using a 6.3mm diameter tungsten shield (18.0g/cm3). The source moved along 6 longitudinal grooves, each 1.3mm in diameter, evenly spaced along periphery of the shield, The tungsten rod was enclosqed by 0.5mm thick Delrin (1.41g/cc). Monte Carlo N particle (MCNPX) was used to calculate dose distributions. 51million particles were calculated on 504 cores of a supercomputer. Fifteen different patients originally treated with a traditional tandem‐and‐ovoid applicator, with 5 fractions each, (15 patients X 5 fxs = 75 plans) were re‐planned with the DMBT applicator combined with traditional ovoids, on an in‐house developed HDR brachytherapy planning platform, which used intensity modulated planning capabilities using a constrained gradient optimization algorithm. For all plans the prescription dose was 6 Gy and they were normalized to match the clinical treated V100.Results:Generally, the DMBT plan quality was a remarkable improvement from conventional T&O plans because of the anisotropic dose distribution of DMBT. The largest difference was to the bladder which had a 0.59±0.87 Gy (8.5±28.7%) reduction in dose. This was because of the the horseshoe shape (U‐shape) of the bladder. The dose reduction to rectum and sigmoid were 0.48±0.55 Gy (21.1±27.2%) and 0.10±0.38 Gy (40.6±214.9%), respectively. The D90 to the HRCTV was 6.55±0.96 Gy (conventional T&O) and 6.59±1.06 Gy (DMBT).Conclusion:For image guided adaptive brachytherapy, greater flexibility of radiation intensity is essential and DMBT can be the solution.
SU‐C‐19A‐01: A Simple Deep Inspiration Breath Hold System
Authors: Rasmussen B , Duelge J , Baldwin B , Valenti M , Hunsader A , Kaznowski L , Blackburn J , Chu K 
Published: July 2014

Purpose:Deep Inspiration Breath Hold (DIBH) Radiation therapy for left sided breast can reduce dose to the lungs and heart. The purpose of this work is to illustrate how to implement a simple method of DIBH for simulation and treatment using equipment readily available in most radiation oncology clinics.Methods:For simulation and treatment, a foam block is placed on the patient's abdomen or chest and a horizontal laser mounted on a movable slide is aimed at the center of the foam block. After a coaching session the block is marked at the average free breathing position and average DIBH position. The position of block relative to laser can be seen by the patient via prism glasses as well as the radiation therapists via a video camera system. Simulation CT scans and treatment delivery are performed under DIBH conditions. Imaging and treatment are performed by manually turning the beam on once the patient has achieved DIBH after being given verbal instructions.Results:Manually triggered imaging was used daily to verify DIBH reproducibility for all patients treated using this system. Sets of before and during port images were used to ensure patient position was appropriate for treatment. Results of the laser on block method were compared to a sister facility using surface mapping techniques for DIBH and the two methods were found to have clinically equivalent reproducibility.Conclusion:The laser and block system was found to be simple to implement and robust during patient treatment. This system can be created from readily available materials at low cost and provides adequate feedback to patient and therapists. During treatment images document the reproducibility of setup and give confidence to clinicians that this method is reproducible from day to day.
SU‐C‐19A‐07: Influence of Immobilization On Plan Robustness in the Treatment of Head and Neck Cancer with IMPT
Authors: Bues M , Anand A , Morse B , Kruse J , Liu W , Shen J , Keole S , Patel S 
Published: July 2014

Purpose:We evaluated the effect of interposing immobilization devices into the beam's path on the robustness of a head and neck plan.Methods:An anthropomorphic head phantom was placed into a preliminary prototype of a specialized head and neck immobilization device for proton beam therapy. The device consists of a hard low density shell, a custom mold insert, and thermoplastic mask to immobilize the patient's head in the shell. This device was provided by CIVCO Medical Solutions for the purpose of evaluation of suitability for proton beam therapy. See Figure 1. Two pairs of treatment plans were generated. The first plan in each pair was a reference plan including only the anthropomorphic phantom, and the second plan in each pair included the immobilization device. In all other respects the plans within the pair were identical.Results:In the case of the simple plan the degradation of plan robustness was found to be clinically insignificant. In this case, target coverage in the worst case scenario was reduced from 95% of the target volume receiving 96.5% of prescription dose to 95% of the target volume receiving 96.3% of prescription dose by introducing the immobilization device. In the case of the complex plan, target coverage of the boost volume in the worst case scenario was reduced from 95% of the boost target volume receiving 97% of prescription dose to 95% of the boost target volume receiving 83% of prescription dose by introducing the immobilization device. See Figure 2.Conclusion:Immobilization devices may have a deleterious effect on plan robustness. Evaluation of the preliminary prototype revealed a variable impact on the plan robustness depending of the complexity of the case.Brian Morse is an employee of CIVCO Medical Solutions.