bluuebunny/crossref_metadata_2025 huggingface dataset:
TH‐E‐BRE‐08: GPU‐Monte Carlo Based Fast IMRT Plan Optimization
Authors: Li Y , Tian Z , Shi F , Jiang S , Jia X
Published: July 2014

Purpose:

Intensity‐modulated radiation treatment (IMRT) plan optimization needs pre‐calculated beamlet dose distribution. Pencil‐beam or superposition/convolution type algorithms are typically used because of high computation speed. However, inaccurate beamlet dose distributions, particularly in cases with high levels of inhomogeneity, may mislead optimization, hindering the resulting plan quality. It is desire to use Monte Carlo (MC) methods for beamlet dose calculations. Yet, the long computational time from repeated dose calculations for a number of beamlets prevents this application. It is our objective to integrate a GPU‐based MC dose engine in lung IMRT optimization using a novel two‐steps workflow.

Methods:

A GPU‐based MC code gDPM is used. Each particle is tagged with an index of a beamlet where the source particle is from. Deposit dose are stored separately for beamlets based on the index. Due to limited GPU memory size, a pyramid space is allocated for each beamlet, and dose outside the space is neglected. A two‐steps optimization workflow is proposed for fast MC‐based optimization. At first step, rough beamlet dose calculations is conducted with only a small number of particles per beamlet. Plan optimization is followed to get an approximated fluence map. In the second step, more accurate beamlet doses are calculated, where sampled number of particles for a beamlet is proportional to the intensity determined previously. A second‐round optimization is conducted, yielding the final Result.

Results:

For a lung case with 5317 beamlets, 105 particles per beamlet in the first round, and 108 particles per beam in the second round are enough to get a good plan quality. The total simulation time is 96.4 sec.

Conclusion:

A fast GPU‐based MC dose calculation method along with a novel two‐step optimization workflow are developed. The high efficiency allows the use of MC for IMRT optimizations.
TH‐E‐BRE‐11: Adaptive‐Beamlet Based Finite Size Pencil Beam (AB‐FSPB) Dose Calculation Algorithm for Independent Verification of IMRT and VMAT
Authors: Park C , Arhjoul L , Yan G , Lu B , Li J , Liu C
Published: July 2014

Purpose:

In current IMRT and VMAT settings, the use of sophisticated dose calculation procedure is inevitable in order to account complex treatment field created by MLCs. As a consequence, independent volumetric dose verification procedure is time consuming which affect the efficiency of clinical workflow. In this study, the authors present an efficient Pencil Beam based dose calculation algorithm that minimizes the computational procedure while preserving the accuracy.

Methods:

The computational time of Finite Size Pencil Beam (FSPB) algorithm is proportional to the number of infinitesimal identical beamlets that constitute the arbitrary field shape. In AB‐FSPB, the dose distribution from each beamlet is mathematically modelled such that the sizes of beamlets to represent arbitrary field shape are no longer needed to be infinitesimal nor identical. In consequence, it is possible to represent arbitrary field shape with combinations of different sized and minimal number of beamlets.

Results:

On comparing FSPB with AB‐FSPB, the complexity of the algorithm has been reduced significantly. For 25 by 25 cm2 squared shaped field, 1 beamlet of 25 by 25 cm2 was sufficient to calculate dose in AB‐FSPB, whereas in conventional FSPB, minimum 2500 beamlets of 0.5 by 0.5 cm2 size were needed to calculate dose that was comparable to the Result computed from Treatment Planning System (TPS). The algorithm was also found to be GPU compatible to maximize its computational speed. On calculating 3D dose of IMRT (∼30 control points) and VMAT plan (∼90 control points) with grid size 2.0 mm (200 by 200 by 200), the dose could be computed within 3∼5 and 10∼15 seconds.

Conclusion:

Authors have developed an efficient Pencil Beam type dose calculation algorithm called AB‐FSPB. The fast computation nature along with GPU compatibility has shown performance better than conventional FSPB. This completely enables the implantation of AB‐FSPB in the clinical environment for independent volumetric dose verification.
TH‐E‐BRF‐06: Kinetic Modeling of Tumor Response to Fractionated Radiotherapy
Authors: Zhong H , Gordon J , Chetty I
Published: July 2014

Purpose:

Accurate calibration of radiobiological parameters is crucial to predicting radiation treatment response. Modeling differences may have a significant impact on calibrated parameters. In this study, we have integrated two existing models with kinetic differential equations to formulate a new tumor regression model for calibrating radiobiological parameters for individual patients.

Methods:

A system of differential equations that characterizes the birth‐and‐death process of tumor cells in radiation treatment was analytically solved. The solution of this system was used to construct an iterative model (Z‐model). The model consists of three parameters: tumor doubling time Td, half‐life of dying cells Tr and cell survival fraction SFD under dose D. The Jacobian determinant of this model was proposed as a constraint to optimize the three parameters for six head and neck cancer patients. The derived parameters were compared with those generated from the two existing models, Chvetsov model (C‐model) and Lim model (L‐model). The C‐model and L‐model were optimized with the parameter Td fixed.

Results:

With the Jacobian‐constrained Z‐model, the mean of the optimized cell survival fractions is 0.43±0.08, and the half‐life of dying cells averaged over the six patients is 17.5±3.2 days. The parameters Tr and SFD optimized with the Z‐model differ by 1.2% and 20.3% from those optimized with the Td‐fixed C‐model, and by 32.1% and 112.3% from those optimized with the Td‐fixed L‐model, respectively.

Conclusion:

The Z‐model was analytically constructed from the cellpopulation differential equations to describe changes in the number of different tumor cells during the course of fractionated radiation treatment. The Jacobian constraints were proposed to optimize the three radiobiological parameters. The developed modeling and optimization methods may help develop high‐quality treatment regimens for individual patients.
SU‐A‐BRE‐01: AAPM Medical Physics Student Meeting
Authors: Pizzutiello R , Svatos M
Published: July 2014

The purpose of this meeting is to emphasize entrepreneurship and opportunities in industry as a valuable part of our profession, bringing the benefits of new ideas and techniques generated by the basic scientists to the broad patient population. Thinking outside the traditional “clinical Medical Physics box”, there are a variety of ways that individuals can use their medical physics training/experience in entrepreneurial endeavors. Whether as an individual, a small group of medical physicists, or part of an industry (corporate) environment, the speakers will explore how current students and trainees can make a veritable impact to our profession in a non‐clinical setting. Our distinguished speakers will also be happy to answer general questions from the audience.
SU‐C‐16A‐06: Optimum Radiation Source for Radiation Therapy of Skin Cancer
Authors: Safigholi Habib , Meigooni A S.
Published: July 2014

Purpose:

Recently, different applicators are designed for treatment of the skin cancer such as scalp and legs, using Ir‐192 HDR Brachytherapy Sources (IR‐HDRS), Miniature Electronic Brachytherapy Sources (MEBXS), and External Electron Beam Radiation Therapy (EEBRT). Although, all of these methodologies may deliver the desired radiation dose to the skin, the dose to the underlying bone may become the limiting factor for selection of the optimum treatment technique. In this project the radiation dose delivered to the underlying bone has been evaluated as a function of the radiation source and thickness of the underlying bone.

Methods:

MC simulations were performed using MCNP5 code. In these simulations, the mono‐energetic and non‐divergent photon beams of 30 keV, 50 keV, and 70 keV for MEBXS, 380 keV photons for IR‐HDRS, and 6 MeV mono‐energetic electron beam for EEBRT were modeled. A 0.5 cm thick soft tissue (0.3 cm skin and 0.2 cm adipose) with underlying 0.5 cm cortical bone followed by 14 cm soft tissue are utilized for simulations.

Results:

Dose values to bone tissue as a function of beam energy and beam type, for a delivery of 5000 cGy dose to skin, were compared. These results indicate that for delivery of 5000 cGy dose to the skin surface with 30 keV, 50 keV, 70 keV of MEBXS, IR‐HDRS, and EEBRT techniques, bone will receive 31750 cGy, 27450 cGy, 18550 cGy, 4875 cGy, and 10450 cGy, respectively.

Conclusion:

The results of these investigations indicate that, for delivery of the same skin dose, average doses received by the underlying bone are 5.2 and 2.2 times larger with a 50 keV MEBXS and EEBRT techniques than IR‐HDRS, respectively.
SU‐C‐16A‐07: Sculpting Isodose Lines: Design of An Internally Shielded Tandem for Cervical Cancer Brachytherapy
Authors: Zhang M , Mo X , Yue N , Zou J
Published: July 2014

Purpose:

With the prescription method moving from point A to 3D volume based in cervical cancer HDR brachytherapy, the traditional pear‐shaped isodose lines are desired to be sculptured to conform to the irregular shaped target. The standard single channel tandem cannot generate asymmetric isodose lines. Most of the directionally shielded sources proposed in literature are challenging to manufacture and operate. In this study, we proposed a novel internally shielded tandem applicator design which gave users more freedom to manipulate isodose lines while planning.

Methods:

The proposed tandem design has one centrally located lead cylindrical rod of 8 mm in diameter serving as the internal shield. Multiple source channels with the diameter of 2 mm are evenly spaced and engraved on the central cylindrical rod. The overall diameter of the tandem with polymer encapsulation was kept to be 10 mm. Various number of channels and engraving depths have been tested in the design process. Geant4 Monte Carlo toolkit was used for dose calculation assuming a Varian VS2000 source was placed inside the applicator. A Monte Carlo based planning system has been developed in‐house to generate brachytherapy plans. Test plans by using this internally shielded tandem were generated for 3 clinical cases.

Results:

Water phantom results shown the dose distribution from a VS2000 source in the tandem was strongly distorted towards one direction due to the presence of shielding material. Conformal plans with asymmetric isodose distributions around the tandem can be generated by optimizing dwell times in different channels.

Conclusion:

An effective and easy‐to‐use internally shielded tandem was developed. It gave user the freedom to sculpt isodose lines to generate conformal plans for cervical cancer brachytherapy.
SU‐C‐19A‐05: Treatment Chairs for Modern Radiation Therapy Treatments
Authors: Court L , Fullen D , Tharp K , Palmer J , Ungchusri G , Reyes L , Tong T , Nguyen S , Phillips T , Balter P
Published: July 2014

Purpose:

Treating patients in a seated position has potential advantages including improved comfort, increased lung volume, and reduced respiratory motion. We compared chair designs for head and neck, thoracic and breast patients for use with either IGRT linacs or a proposed low‐cost fixed horizontal beam‐line machine.

Methods:

Three treatment chairs were designed and constructed. Two of the chairs are based on a massage‐chair, with the patient angled slightly forwards and knee rests used to minimize intra‐fraction slouch. The third chair design is more conventional; the patient is angled backwards, with indexed positioning devices and the ability to attach thermoplastic masks. Patient geometries, including PTV location and patient sizes, were extracted from 137 CTs of past patients were used to model the probability of collision between the patient and the linac for various seated positions. All chairs were designed around the weight limits for couches on our linacs. At the time of writing we have just received IRB approval for imaging studies to evaluate comfort, and intra‐ and interfraction reproducibility.

Results:

The geometric analysis showed that head and neck patients and thoracic patients could be treated without collision. However, there is very limited space between the patient and the treatment/imaging devices, so careful design of the chair is essential. The position of the treatment target and extended arm positioning means that this is a particular concern for thoracic and breast patients. This was demonstrated for one of the prototype chairs designed for breast treatment where the arm holders would collide with the kV detector. The extra clearance of a dedicated fixed‐beam linac would overcome these difficulties. Intra‐ and inter‐fraction reproducibility results will be presented at the meeting.

Conclusion:

To take advantage of the clinical advantages of seated treatments, appropriate treatment chairs are needed. A dedicate fixed‐beam linac may enable more options.

This work was partially funded by Varian Medical Systems
SU‐C‐BRE‐02: BED Vs. Local Control: Radiobiological Effect of Tumor Volume in Monte Carlo (MC) Lung SBRT Planning
Authors: Pokhrel D , Badkul R , Jiang H , Estes C , Park J , Kumar P , Wang F
Published: July 2014

Purpose:

SBRT with hypofractionated dose schemata has emerged a compelling treatment modality for medically inoperable early stage lung cancer patients. It requires more accurate dose calculation and treatment delivery technique. This report presents the relationship between tumor control probability(TCP) and size‐adjusted biological effective dose(sBED) of tumor volume for MC lung SBRT patients.

Methods:

Fifteen patients who were treated with MC‐based lung SBRT to 50Gy in 5 fractions to PTVV100%=95% were studied. ITVs were delineated on MIP images of 4DCT‐scans. PTVs diameter(ITV+5mm margins) ranged from 2.7–4.9cm (mean 3.7cm). Plans were generated using non‐coplanar conformal arcs/beams using iPlan XVMC algorithm (BrainLABiPlan ver.4.1.2) for Novalis‐TX with HD‐MLCs and 6MVSRS(1000MU/min) mode, following RTOG‐0813 dosimetric guidelines. To understand the known uncertainties of conventional heterogeneities‐corrected/uncorrected pencil beam (PBhete/ PB‐homo) algorithms, dose distributions were re‐calculated with PBhete/ PB‐homo using same beam configurations, MLCs and monitor units. Biologically effective dose(BED10) was computed using LQ‐model with α/β=10Gy for meanPTV and meanITV. BED10‐c*L, gave size‐adjusted BED(sBED), where c=10Gy/cm and L=PTV diameter in centimeter. The TCP model was adopted from Ohri et al.(IJROBP, 2012): TCP = exp[sBEDTCD50]/ k /(1.0 + exp[sBED‐TCD50]/k), where k=31Gy corresponding to TCD50=0Gy; and more realistic MC‐based TCP was computed for PTV(V99%).

Results:

Mean PTV PB‐hete TCP value was 6% higher, but, mean PTV PB‐homo TCP value was 4% lower compared to mean PTV MC TCP. Mean ITV PB‐hete/PB‐homo TCP values were comparable (within ±3.0%) to mean ITV MC TCP. The mean PTV(V99%)had BED10=90.9±3.7%(median=92.2%),sBED=54.1±8.2%(median=53.5%) corresponding to mean MC TCP value of 84.8±3.3%(median=84.9%) at 2‐ year local control.

Conclusion:

The TCP model which incorporates BED10 and tumor diameter indicates that radiobiological effect of target volume and dose calculation algorithm significantly affects TCP for lung SBRT patients. Dose calculation using MC‐based algorithm is more realistic with tissue heterogeneities and is routinely performed in our clinic. Patients will be followed up to determine whether TCP prediction correlate clinical outcomes.
SU‐C‐BRE‐03: Dual Compartment Mathematical Modeling of Glioblastoma Multiforme (GBM)
Authors: Yu V , Nguyen D , Kupelian P , Kaprealian T , Selch M , Low D , Pajonk F , Sheng K
Published: July 2014

Purpose:

To explore the aggressive recurrence and radioresistence of GBM with a dual compartment tumor survival mathematical model based on intrinsic tumor heterogeneity, cancer stem cells (CSC) and differentiated cancer cells (DCC).

Methods:

The repopulation and differentiation responses to radiotherapy of a solid tumor were simulated using an Ordinary Differential Equation (ODE). To obtain the tumor radiobiological parameters, we assumed that a tumor consists of two subpopulations, each with its distinctive linear quadratic parameters. The dual compartment cell survival model was constructed as SF(D)=F × exp(‐α1 D‐β1D2) + (1‐F) × exp(‐α2D‐β2D2) for a single fraction of treatment, with F as the fraction of CSC, and α and β describing the radiological properties of each population. Robust least square fitting was performed on clonogenic survival data from one GBM (U373MG) and one NSCLC (H460) cell line. The fit parameters were then used in the ODE model to predict treatment outcome of various treatment schemes.

Results:

The fit parameters from GBM cell survival data were (F, α1, β1, α2, β2)=(0.0396, 0.0801, 0.0006, 0.1363, 0.0279), exhibiting two populations with distinctive radiological properties, CSC more radioresistant than DCC. The GBM cell line exhibited significantly poorer tumor control than its single compartment model prediction and NSCLC, which responded well to hypofrationation. The increased radioresistance was due to rapid regrowth of the DCC compartment triggered by its depletion while maintaining a viable CSC population. The rapid regrowth can be reduced by treating dose fractions ≤ 2 Gy with a prolonged treatment period.

Conclusion:

The interaction between a radioresistant CSC compartment and DCC compartment can explain the poor clinical outcome of GBM after radiotherapy despite dose escalation and hypofractionation attempts. Lower dose fractions result in better treatment outcome but still eventually recurs. Dose escalation beyond 100 Gy and/or differentiation therapy will be vital in achieving GBM tumor control.
SU‐C‐BRD‐02: A Team Focused Clinical Implementation and Failure Mode and Effects Analysis of HDR Skin Brachytherapy Using Valencia and Leipzig Surface Applicators
Authors: Sayler E , Harrison A , Eldredge‐Hindy H , Dinome J , Munro S , Anne R , Comber E , Lockamy V
Published: July 2014

Purpose:

and Leipzig applicators (VLAs) are single‐channel brachytherapy surface applicators used to treat skin lesions up to 2cm diameter. Source dwell times can be calculated and entered manually after clinical set‐up or ultrasound. This procedure differs dramatically from CT‐based planning; the novelty and unfamiliarity could lead to severe errors. To build layers of safety and ensure quality, a multidisciplinary team created a protocol and applied Failure Modes and Effects Analysis (FMEA) to the clinical procedure for HDR VLA skin treatments.

Methods:

team including physicists, physicians, nurses, therapists, residents, and administration developed a clinical procedure for VLA treatment. The procedure was evaluated using FMEA. Failure modes were identified and scored by severity, occurrence, and detection. The clinical procedure was revised to address high‐scoring process nodes.

Results:

Several key components were added to the clinical procedure to minimize risk probability numbers (RPN): ‐Treatments are reviewed at weekly QA rounds, where physicians discuss diagnosis, prescription, applicator selection, and set‐up. Peer review reduces the likelihood of an inappropriate treatment regime. ‐A template for HDR skin treatments was established in the clinical EMR system to standardize treatment instructions. This reduces the chances of miscommunication between the physician and planning physicist, and increases the detectability of an error during the physics second check. ‐A screen check was implemented during the second check to increase detectability of an error. ‐To reduce error probability, the treatment plan worksheet was designed to display plan parameters in a format visually similar to the treatment console display. This facilitates data entry and verification. ‐VLAs are color‐coded and labeled to match the EMR prescriptions, which simplifies in‐room selection and verification.

Conclusion:

Multidisciplinary planning and FMEA increased delectability and reduced error probability during VLA HDR Brachytherapy. This clinical model may be useful to institutions implementing similar procedures.
SU‐C‐BRD‐04: Automatic Detection of Patient Identification and Patient Positioning Errors Using 3D Setup Images
Authors: Jani S , O' Connell D , Chow P , Agazaryan N , Low D , Lamb J
Published: July 2014

Purpose:

To develop an automated system to detect patient identification and patient positioning errors using algorithmic comparison between megavoltage CT (MVCT) and kilovoltage CT (kVCT) planning images.

Methods:

MVCT images from 35 head and neck (H&N) patients and 19 pelvis patients were collected from a Tomotherapy machine, along with the corresponding planning kVCTs. MVCTs and kVCTs were manually aligned according to clinical protocols at our institution. Patient identification errors were simulated by aligning MVCTs and kVCTs from different patients. Positioning errors were simulated by misaligning MVCTs and kVCTs by 1cm to 5cm in the each of the six anatomical directions. For each image pair, a pixel‐by‐pixel cross‐correlation metric was computed within the MVCT image body contour. To eliminate the effect of daily variations in bowel gas, the metric was limited to voxels with HU>‐700. The kVCT voxel intensities were remapped to the MVCT scale using a third‐order polynomial from a publicly available software package.

Results:

A threshold pixel‐by‐pixel cross‐correlation value was found that distinguished between correct and incorrect patient setup with a high degree of accuracy. A stratified 10‐fold cross‐validation analysis yielded average misclassification probabilities of 0.0030 for H&N and 0.00 for pelvis. For misaligned image pairs, cross‐validation analysis yielded average misclassification probabilities of 0.00 and 0.0013 for H&N shifts ≥20mm and ≥10mm across all six anatomical directions, respectively. Misclassification probabilities were 0.00, 0.011, and 0.10 for pelvic shifts ≥30mm, ≥20mm, and ≥10mm, respectively. Receiver operator characteristic analysis for misaligned patients yielded areas under the curve ranging from 0.99 to 1.0 for H&N and 0.86 to 1.0 for pelvis.

Conclusion:

This proof‐ofconcept study shows that pixel‐by‐pixel cross‐correlation of MVCT setup images with their corresponding planning CT images can be used to detect wrong‐patient errors as well as incorrect patient shifts in the pelvis and H&N regions.
SU‐C‐BRD‐07: The Radiological Physics Center (RPC): 45 Years of Improving Radiotherapy Dosimetry
Authors: Followill D , Lowenstein J , Molineu A , Alvarez P , Summers P , Kry S
Published: July 2014

Purpose:

The RPC, established in 1968 has contributed to the development, conduct, and QA of NCI funded multi‐institutional cooperative group clinical trials and institutions, primarily in the USA/Canada and 242 other countries, participating in trials.

Methods:

The RPC QA program components were designed to audit the radiation dose calculation chain from the NIST traceable reference beam calibration, to inclusion of dosimetry parameters used to calculate tumor doses, to the delivery of the radiation dose. The QA program included: 1) remote TLD/OSLD audit of machine output, 2) on‐site dosimetry review visits, 3) credentialing for advanced technologies, and 4) review of patient treatment records. The RPC presented and published their findings to the radiation oncology community.

Results:

The number of institutions monitored by the RPC increased from around 1200 in the late 90s, to ∼2000 in 2013. There were over 4000 megavoltage therapy machines and ∼28,000 therapy beams in the 1991 institutions monitored by the RPC by the end of 2013. Within the 14,000 photon, electron and proton beam outputs remotely monitored with TLD/OSLD annually, between 10‐20% of the institutions have one or more beams outside the RPC 5% criterion. Dosimetry site visits to photon and proton centers continue to result in 2‐4 recommendations affecting key dosimetry parameters that impact patient treatment times. One in four patient treatment records reviewed by the RPC have their dose data corrected by >5% before trial groups use them for outcomes analysis. Twelve of fourteen clinically active proton centers are approved to participate in NCI funded clinical trials. The RPC published 222 peer reviewed articles since 1972.

Conclusion:

Findings from the RPC suggest that human errors continue to play a role in radiotherapy discrepancies and without the RPC independent QA program, the number of undetected errors and time elapsed before their discovery would have been greater.

Work supported by MGH C06 CA059267 and grants CA10953, CA081647 awarded by NCI, DHHS.
SU‐C‐BRF‐01: Correlation of DIBH Breath Hold Amplitude with Dosimetric Sparing of Heart and Left Anterior Descending Artery in Left Breast Radiotherapy
Authors: Kim Taeho , Reardon Kelli , Sukovich Kaitlyn , Crandley Edwin , Read Paul , Krishni Wijesooriya
Published: July 2014

Purpose:

A 7.4% increase in major coronary events per 1 Gy increase in mean heart dose has been reported from the population‐based analysis of radiation‐induced cardiac toxicity following treatment of left sided breast cancer. Deep inhalation breath‐hold (DIBH) is clinically utilized to reduce radiation dose to heart and left anterior descending artery (LAD). We investigated the correlation of dose sparing in heart and LAD with internal DIBH amplitude to develop a quantitative predictive model for expected dose to heart and LAD based on internal breath hold amplitude.

Methods:

A treatment planning study (Prescription Dose = 50 Gy) was performed on 50 left breast cancer patients underwent DIBH whole breast radiotherapy. Two CT datasets, free breathing (FB) and DIBH, were utilized for treatment planning and for determination of the internal anatomy DIBH amplitude (difference between sternum position at FB and DIBH). The heart and LAD dose between FB and DIBH plans was compared and dose to the heart and LAD as a function of breath hold amplitude was determined.

Results:

Average DIBH amplitude using internal anatomy was 13.9±4.2 mm. The DIBH amplitude‐mean dose reduction correlation is 20%/5mm (0.3 Gy/5mm) for the heart and 18%/5mm (1.1 Gy/5mm) for LAD. The correlation with max dose reduction is 12%/5mm (3.8 Gy/5mm) for the heart and 16%/5mm (3.2 Gy/5mm) for LAD. We found that average dose reductions to LAD from 6.0±6.5 Gy to 2.0±1.6 Gy with DIBH (4.0 Gy reduction: ‐67%, p < 0.001) and average dose reduction to the heart from 1.3±0.7 Gy to 0.7±0.2 Gy with DIBH (0.6 Gy reduction: ‐46%, p < 0.001). That suggests using DIBH may reduce the risk of the major coronary event for left sided breast cancer patients.

Conclusion:

The correlation between breath hold amplitude and dosimetric sparing suggests that dose sparing linearly increases with internal DIBH amplitude.
SU‐C‐BRF‐02: Surface Imaging Based Analysis of Intra‐Fraction Motion for Breast Radiotherapy Patients
Authors: Wiant D , Wentworth S , Maurer J , Vanderstraeten C , Terrell J , Sintay B
Published: July 2014

Purpose:

To quantify and characterize intrafraction motion for breast radiotherapy treatments using 3D surface imaging.

Methods:

Thirty free breathing breast patients were monitored with 3D surface imaging over a total of 831 monitoring sessions. Mean translations and rotations were calculated over each minute, each session, and over all sessions combined. The percentage of each session that the root mean square (RMS) of the linear translations were outside of 2 mm, 3 mm, 4 mm, and 5 mm were determined for each patient. Correlations between mean translations per minute and time and between standard deviation per minute and time were evaluated using Pearson's r value.

Results:

The mean RMS translation averaged over all patients was 2.63 mm +/‐ 1.63 mm. The patients spent an average of 52%, 24%, 11%, and 5% of the monitoring time outside of 2 mm, 3 mm, 4 mm, and 5 mm RMS tolerances, respectively. The RMS values averaged over all patients were 2.95 mm +/‐ 1.67 mm, 3.21 +/‐ 2.11, and 3.57 mm +/‐ 2.23 mm over the 5th, 10th, and 15th minutes of monitoring, respectively. The RMS values (r = 0.95, p = 0) and the standard deviations of the RMS values (r = 0.97, p = 0) both showed strong significant correlations with time.

Conclusion:

The majority of patients treatment time is spent within 5 mm of the isocenter. Patient position tends to drift with increasing time in the session. Treatment length should be considered when determining planning margins. An 8 mm margin on a target volume would account for two standard deviations of motion for a treatment up to 15 minutes in length.
SU‐C‐BRF‐03: PCA Modeling of Anatomical Changes During Head and Neck Radiation Therapy
Authors: Chetvertkov M , Kim J , Siddiqui F , Kumarasiri A , Chetty I , Gordon J
Published: July 2014

Purpose:

To develop principal component analysis (PCA) models from daily cone beam CTs (CBCTs) of head and neck (H&N) patients that could be used prospectively in adaptive radiation therapy (ART).

Methods:

: For 7 H&N patients, Pinnacle Treatment Planning System (Philips Healthcare) was used to retrospectively deformably register daily CBCTs to the planning CT. The number N of CBCTs per treatment course ranged from 14 to 22. For each patient a PCA model was built from the deformation vector fields (DVFs), after first subtracting the mean DVF, producing N eigen‐DVFs (EDVFs). It was hypothesized that EDVFs with large eigenvalues represent the major anatomical deformations during the course of treatment, and that it is feasible to relate each EDVF to a clinically meaningful systematic or random change in anatomy, such as weight loss, neck flexion, etc.

Results:

DVFs contained on the order of 3×87×87×58=1.3 million scalar values (3 times the number of voxels in the registered volume). The top 3 eigenvalues accounted for ∼90% of variance. Anatomical changes corresponding to an EDVF were evaluated by generating a synthetic DVF, and applying that DVF to the CT to produce a synthetic CBCT. For all patients, the EDVF for the largest eigenvalue was interpreted to model weight loss. The EDVF for other eigenvalues appeared to represented quasi‐random fraction‐to‐fraction changes.

Conclusion:

The leading EDVFs from single‐patient PCA models have tentatively been identified with weight loss changes during treatment. Other EDVFs are tentatively identified as quasi‐random inter‐fraction changes. Clean separation of systematic and random components may require further work. This work is expected to facilitate development of population‐based PCA models that can be used to prospectively identify significant anatomical changes, such as weight loss, early in treatment, triggering replanning where beneficial.
SU‐C‐BRF‐04: Delivered 4D Dose Calculation for Lung‐VMAT Patients Using In‐ Treatment CBCT and LINAC Log Data
Authors: Saotome N , Haga A , Imae T , Kida S , Nakano M , Yamashita H , Nakagawa K , Ohtomo K
Published: July 2014

Purpose:

To verify the delivered four‐dimensional (4D) dose distribution for the lung VMAT using in‐treatment 4D cone‐beam CT (CBCT) and LINAC log data.

Methods:

Three patients for lung stereotactic radiotherapy (SRT) were treated by single‐arc volumetric modulated arc therapy (VMAT) created by SmartArc in Pinnacle v9.2 (Philips, USA).Kilovoltage (kV) projection images were acquired during VMAT delivery using the x‐ray volumetric imager, XVI (Elekta, UK). LINAC log data were also recorded via iCom interface (Elekta, UK). Subsequently, the iCom data format was converted to Pinnacle data format, thereby allowing Pinnacle to read actual MLC positions, jaw positions, gantry angles and MUs. These parameters were categorized into four groups according to patient's respiratory phase. The patient respiratory phase was determined from kV‐projection images by in‐house phase recognizing software. By exporting these data back to Pinnacle, in‐treatment dose distributions for each respiratory phase were obtained by combining calculated dose having a particular phase. The 4D CBCT were reconstructed by in‐house program. The density in the structures on the CBCT was overridden by the average density in the corresponding structures on the planning CT for the dose calculation. The dose indexes, such as maximum, minimum, mean dose in the target were compared among the plan, in‐treatment 3D calculation, and in‐treatment 4D calculation.

Results:

The day‐to‐day variation of the delivered dose was observed for all three patients. The maximum difference was 5.9% for the minimum dose in the target. Difference for the mean dose was found to be small (1.1% at maximum).

Conclusion:

We have obtained in‐treatment dose distribution for each of the different respiratory phases using in‐treatment 4D CBCT and LINAC log data during lung VMAT delivery. Our result indicate a small but significant dose difference between the 3D and 4D calculations for the case of large target traveling.
SU‐C‐BRF‐05: Design and Geometric Validation of An Externally and Internally Deformable, Programmable Lung Motion Phantom
Authors: Cheung Y , Sawant A
Published: July 2014

Purpose:

Most clinically‐deployed strategies for respiratory motion management in lung radiotherapy (e.g., gating, tracking) use external markers that serve as surrogates for tumor motion. However, typical lung phantoms used to validate these strategies are rigid‐exterior+rigid‐interior or rigid‐exterior+deformable‐interior. Neither class adequately represents the human anatomy, which is deformable internally as well as externally. We describe the construction and experimental validation of a more realistic, externally‐ and internally‐deformable, programmable lung phantom.

Methods:

The outer shell of a commercially‐available lung phantom (RS‐ 1500, RSD Inc.) was used. The shell consists of a chest cavity with a flexible anterior surface, and embedded vertebrae, rib‐cage and sternum. A 3‐axis platform was programmed with sinusoidal and six patient‐recorded lung tumor trajectories. The platform was used to drive a rigid foam ‘diaphragm’ that compressed/decompressed the phantom interior. Experimental characterization comprised of mapping the superior‐inferior (SI) and anterior‐posterior (AP) trajectories of external and internal radioopaque markers with kV x‐ray fluoroscopy and correlating these with optical surface monitoring using the in‐room VisionRT system.

Results:

The phantom correctly reproduced the programmed motion as well as realistic effects such as hysteresis. The reproducibility of marker trajectories over multiple runs for sinusoidal as well as patient traces, as characterized by fluoroscopy, was within 0.4 mm RMS error for internal as well as external markers. The motion trajectories of internal and external markers as measured by fluoroscopy were found to be highly correlated (R=0.97). Furthermore, motion trajectories of arbitrary points on the deforming phantom surface, as recorded by the VisionRT system also showed a high correlation with respect to the fluoroscopically‐measured trajectories of internal markers (R=0.92).

Conclusion:

We have developed a realistic externally‐ and internally‐deformable lung phantom that will serve as a valuable tool for clinical QA and motion management research. This work was supported through funding from the NIH and VisionRT Ltd.

Amit Sawant has research funding from Varian Medical Systems, VisionRT and Elekta
SU‐C‐BRF‐06: Impact of Temporal Probability in 4D Dose Calculation for Lung Cancer Treatment Planning
Authors: Rouabhi O , Ma M , Bayouth J , Xia J
Published: July 2014

Purpose:

To evaluate dosimetric uncertainty in 4D dose calculation for lung cancer patients using three different temporal probabilities.

Methods:

The impact of temporal probability, defined as the fraction of time a patient spends in each respiratory amplitude, was evaluated in nine lung cancer patients. For each patient, 4D dose was computed using 4DCT and three temporal probability distributions: 1) uniform distribution, 2) sinusoidal distribution, and 3) patient‐specific distribution. To calculate 4D dose, the dose for each of 10 binned CTs was first computed using the same planning parameters as those used in the breath‐hold CT. Next, deformable image registration was used to deform the dose of each binned CT to the breathhold CT using the deformation map between each binned CT and the breathhold CT. Finally, 4D dose volume was computed by summing the 10 deformed doses using corresponding temporal probabilities. In this study, 4D dose calculated from patient‐specific temporal probabilities was used as the ground truth. Dosimetric comparison included: 1) 3D gamma (3% dose difference, 3mm distance to agreement tolerance), 2) mean tumor dose (MTD), 3) mean lung dose (MLD), and 4) lung V20.

Results:

For all patients, both uniform and sinusoidal dose distributions were found to have an average gamma passing rate >99% for both lung and PTV volume. Compared with 4D dose calculated using the patient respiratory trace, uniform distribution and sinusoidal distribution showed a percentage difference on average of ‐0.1±0.6% and ‐0.2±0.4% in MTD, ‐0.2±2.0% and ‐0.2±1.3% in MLD, 0.9±2.8% and ‐0.7±1.8% in lung V20, respectively.

Conclusion:

Both uniformly and sinusoidally‐distributed temporal probabilities can be used to approximate 4D dose calculation. The dosimetric difference among the three temporal probability distributions is not clinically significant.

This research is supported by Siemens Medical Solutions USA, Inc
SU‐F‐BRF‐10: Deformable MRI to CT Validation Employing Same Day Planning MRI for Surrogate Analysis
Authors: Padgett K , Stoyanova R , Johnson P , Piper J , Javorek A , Dogan N , Pollack A
Published: July 2014

Purpose:

To compare rigid and deformable registrations of the prostate in the multi‐modality setting (diagnostic‐MRI to planning‐CT) by utilizing a planning‐MRI as a surrogate. The surrogate allows for the direct quantitative analysis which can be difficult in the multi‐modality domain where intensity mapping differs.

Methods:

For ten subjects, T2 fast‐spin‐echo images were acquired at two different time points, the first several weeks prior to planning (diagnostic‐MRI) and the second on the same day in which the planning CT was collected (planning‐MRI). Significant effort in patient positioning and bowel/bladder preparation was undertaken to minimize distortion of the prostate in all datasets. The diagnostic‐MRI was deformed to the planning‐CT utilizing a commercially available deformable registration algorithm synthesized from local registrations. The deformed MRI was then rigidly aligned to the planning MRI which was used as the surrogate for the planning‐CT. Agreement between the two MRI datasets was scored using intensity based metrics including Pearson correlation and normalized mutual information, NMI. A local analysis was performed by looking only within the prostate, proximal seminal vesicles, penile bulb and combined areas. A similar method was used to assess a rigid registration between the diagnostic‐MRI and planning‐CT.

Results:

Utilizing the NMI, the deformable registrations were superior to the rigid registrations in 9 of 10 cases demonstrating a 15.94% improvement (p‐value < 0.001) within the combined area. The Pearson correlation showed similar results with the deformable registration superior in the same number of cases and demonstrating a 6.97% improvement (p‐value <0.011).

Conclusion:

Validating deformable multi‐modality registrations using spatial intensity based metrics is difficult due to the inherent differences in intensity mapping. This population provides an ideal testing ground for MRI to CT deformable registrations by obviating the need for multi‐modality comparisons which are inherently more challenging. Deformable registrations generated in this work significantly outperformed rigid alignments.

Research reported in this abstract was supported by the NIH National Cancer Institute R21CA153826 “MRI‐Guided Radiotherapy and Biomarkers for Prostate Cancer” and Bankhead‐Coley Cancer Research Program 10BT‐03 “MRI‐Guided Radiotherapy and Biomarkers for Prostate Cancer”.
SU‐F‐BRF‐11: Dose Rearrangement in High Dose Locally Advanced Lung Patients Based On Perfusion Imaging
Authors: Matrosic C , Jarema D , Kong F , McShan D , Stenmark M , Owen D , Ten Haken R , Matuszak M
Published: July 2014

Purpose:

The use of mean lung dose (MLD) limits allows individualization of lung patient tumor doses at safe levels. However, MLD does not account for local lung function differences between patients, leading to toxicity variability at the same MLD. We investigated dose rearrangement to minimize dose to functional lung, as measured by perfusion SPECT, while maintaining target coverage and conventional MLD limits.

Methods:

Retrospective plans were optimized for 15 locally advanced NSCLC patients enrolled in a prospective imaging trial. A priority‐based optimization system was used. The baseline priorities were (1) meet OAR dose constraints, (2) maximize target gEUD, and (3) minimize physical MLD. As a final step, normal tissue doses were minimized. To determine the benefit of rearranging dose using perfusion SPECT, plans were reoptimized to minimize functional lung gEUD as the 4th priority.

Results:

When only minimizing physical MLD, the functional lung gEUD was 10.8+/−5.0 Gy (4.3–19.8 Gy). Only 3/15 cases showed a decrease in functional lung gEUD of ≥4% when rearranging dose to minimize functional gEUD in the cost function (10.5+/−5.0 Gy range 4.3−19.7). Although OAR constraints were respected, the dose rearrangement resulted in ≥10% increases in gEUD to an OAR in 4/15 cases. Only slight reductions in functional lung gEUD were noted when omitting the minimization of physical MLD, suggesting that constraining the target gEUD minimizes the potential to redistribute dose.

Conclusion:

Prioritydriven optimization permits the generation of plans that respect traditional OAR limits and target coverage, but with the ability to rearrange dose based on functional imaging. The latter appears to be limited due to the decreased solution space when constraining target coverage. Since dose rearrangement may increase dose to other OARs, it is also worthwhile to investigate global biomarkers of lung toxicity to further individualize treatment in this population.

Partially supported by R01‐CA142840 and P01‐CA59827
In utero undernourishment perturbs the adult sperm methylome and intergenerational metabolism
Authors: Radford Elizabeth J. , Ito Mitsuteru , Shi Hui , Corish Jennifer A. , Yamazawa Kazuki , Isganaitis Elvira , Seisenberger Stefanie , Hore Timothy A. , Reik Wolf , Erkek Serap , Peters Antoine H. F. M. , Patti Mary-Elizabeth , Ferguson-Smith Anne C.
Published: July 2014

The nutritional sins of the mother…

Prenatal exposures of a mother can affect the health of her offspring, but how? Radford
et al.
found that the male progeny of undernourished pregnant mice had altered DNA chemistry in their sperm. In addition, the offspring displayed compromised metabolic health. The specific affected genes not only lost DNA methylation but also lacked the normal sperm DNA packaging factors (protamines) and instead were enriched in nucleosomes. Thus, when subjected to a suboptimal prenatal environment, offspring feel the effects of the maternal assault.

Science
, this issue p.
10.1126/science.1255903
Complete Genome Sequence of Vibrio anguillarum Phage CHOED Successfully Used for Phage Therapy in Aquaculture
Authors: Romero Jaime , Higuera Gastón , Gajardo Felipe , Castillo Daniel , Middleboe Mathias , García Katherine , Ramírez Carolina , Espejo Romilio T.
Published: July 2014

Vibrio anguillarum
phage CHOED was isolated from Chilean mussels. It is a virulent phage showing effective inhibition of
V. anguillarum
. CHOED has potential in phage therapy, because it can protect fish from vibriosis in fish farms. Here, we announce the completely sequenced genome of
V. anguillarum
phage CHOED.
Complete Genome Sequences of Four Novel Lactococcus lactis Phages Distantly Related to the Rare 1706 Phage Species
Authors: Kot Witold , Neve Horst , Vogensen Finn K. , Heller Knut J. , Sørensen Søren J. , Hansen Lars H.
Published: July 2014

Lactoccocus lactis
is a Gram-positive bacterium widely used in the dairy industry in the production of an array of cheeses and other fermented milk products. Here, we describe the sequencing and genome annotations of a set of four phages virulent to
L. lactis
and exhibiting similarities to phage 1706.
Draft Genome Sequence of
Rhodosporidium toruloides
CECT1137, an Oleaginous Yeast of Biotechnological Interest
Authors: Morin Nicolas , Calcas Xavier , Devillers Hugo , Durrens Pascal , Sherman David James , Nicaud Jean-Marc , Neuvéglise Cécile
Published: July 2014

We report the sequencing of the basidiomycetous yeast
Rhodosporidium toruloides
CECT1137. The current assembly comprises 62 scaffolds, for a total size of ca. 20.45 Mbp and a G+C content of ca. 61.9%. The genome annotation predicts 8,206 putative protein-coding genes.
Draft Genome Sequence of Marine-Derived Actinomycete
Nocardiopsis
sp. Strain TP-A0876, a Producer of Polyketide Pyrones
Authors: Komaki Hisayuki , Ichikawa Natsuko , Hosoyama Akira , Fujita Nobuyuki , Igarashi Yasuhiro
Published: July 2014

Here we report the draft genome sequence of
Nocardiopsis
sp. strain TP-A0876, isolated from marine sediment, which produces polyketide-derived pyrones called nocapyrones. The genome contains three polyketide synthase (PKS) gene clusters, one of which was proposed to be responsible for nocapyrone biosynthesis. This genome sequence will facilitate the study of the potential for secondary metabolism in
Nocardiopsis
strains.
Complete Genome Sequence of Mycoplasma californicum Strain HAZ160_1 from Bovine Mastitic Milk in Japan
Authors: Hata Eiji , Murakami Kenji
Published: July 2014

Bovine mycoplasmal mastitis is spreading quickly among cows. It often leads to clinical mastitis outbreaks and often results in huge economic losses.
Mycoplasma californicum
is an important causal species of bovine mastitis. Presented here is the 799,088-bp complete genome sequence of
M. californicum
strain HAZ160_1, which was isolated in Japan.
Complete Genome Sequences of Two Central European Brucella suis bv. 2 Haplotype 2c Strains Isolated from Wild Boars
Authors: Ferreira Ana Cristina , Tenreiro Rogério , Corrêa de Sá Maria Inácia , Dias Ricardo
Published: July 2014

The
Brucella suis
haplotype 2c is commonly isolated from wild boars and domestic pigs across Central Europe, though it is rarely described in the Iberian Peninsula. We report here the complete and annotated genome sequences of two haplotype 2c strains isolated from wild boars in the northeast region of Spain, above the Ebro River.
Draft Genomes of Heterogeneous Vancomycin-Intermediate Staphylococcus aureus Strain MM66 and MM66 Derivatives with Altered Vancomycin Resistance Levels
Authors: Matyi Stephanie A. , Ramaraj Thiruvarangan , Sundararajan Anitha , Lindquist Ingrid E. , Devitt Nicolas P. , Schilkey Faye D. , Lamichhane-Khadka Reena , Hoyt Peter R. , Mudge Joann , Gustafson John E.
Published: July 2014

The draft genomes of heterogeneous vancomycin-intermediate
Staphylococcus aureus
(hVISA) strain MM66 and MM66 isolates demonstrating altered vancomycin resistance levels were produced in an effort to provide information on mutations contributing to the vancomycin resistance levels observed in these strains
.
Draft Genome Sequence of Polaromonas glacialis Strain R3-9, a Psychrotolerant Bacterium Isolated from Arctic Glacial Foreland
Authors: Wang Zhiyong , Chang Xulu , Yang Xu , Pan Li , Dai Jun
Published: July 2014

Here we report the draft genome sequence of the psychrotolerant
Polaromonas glacialis
strain R3-9, isolated from Midtre Lovénbreen glacial foreland near Ny-Alesund, Svalbard Archipelago, Norway.