bluuebunny/crossref_metadata_2025 huggingface dataset:
TU‐H‐202‐02: Applications, Validation, Clinical Endpoints and Opportunities for CT Ventilation
Authors: Vinogradskiy Y.
Published: July 2016

CT ventilation imaging is an exciting functional imaging modality that combines four‐dimensional computed tomography (4DCT) and deformable image registration (DIR) to provide exquisite ventilation maps of the lung. CT ventilation imaging can be used for:

Functional avoidance in thoracic radiation therapy,

Imaging longitudinal changes in regional lung function for treatment assessment and adaptation,

Image‐assisted diagnosis of non‐oncologic respiratory diseases.

CT ventilation imaging uses CT, a predominantly anatomic imaging modality, and through imaging processing creates functional images. CT ventilation imaging provides functional images that are higher resolution, faster and cheaper to perform than the clinical standard, SPECT. Indeed the number of CT ventilation abstracts presented at the AAPM meeting has been doubling every two years. With the world's‐first clinical trial of CT ventilation functional image‐guided radiation therapy now underway, the first dedicated scientific symposium will educate and stimulate AAPM members from both radiology and radiation oncology.

This symposium will compare the foundations of CT ventilation imaging with competing MRI, PET and SPECT ventilation imaging methods, and details the first clinical trial of CT ventilation imaging for functional avoidance in lung cancer radiation therapy. The spatial‐temporal nature of pulmonary ventilation, response maps to radiation and the design of predictive models will be presented. Validation efforts and challenges will also be discussed, from clinical outcome correlations in single time point and longitudinal studies, to cross‐modality image comparisons in the first multi‐institutional CT ventilation imaging challenge.

The panel will discuss the future role of CT ventilation imaging, and what level of physiologic validation is needed for applications in radiation oncology and beyond.

Learning Objectives:

Learn the principles of CT ventilation imaging and how ventilation images are acquired with MRI, PET and SPECT

Understand the methods used to benchmark CT ventilation and the correlations between CT ventilation imaging and clinical outcomes

Recognize the clinical applications of CT ventilation imaging in radiation oncology and beyond

Australian NHMRC Fellowship. Australian NSW Cancer Institute Fellowship.; Y. Vinogradskiy, The authors acknowledge NIH R01CA200817 grant and Stat of Colorado grant.; T. Yamamoto, This study was supported in part by the American Cancer Society and the Dean of the University of California Davis School of Medicine (ACS IRG‐95‐125‐13). Philips Radiation Oncology Systems loaned us a research version of the Pinnacle3 treatment planning system.; J. Bayouth, Funding support from NCI

R01 CA166703; J. Kipritidis, This work has been supported by a Cancer Institute NSW Early Career Fellowship and an NHMRC Australia Fellowship.

No commercial funding was received for this work.
TU‐H‐207A‐03: CT Hounsfield Unit Accuracy: Effect of Beam Hardening On Phantom and Clinical Whole‐Body CT Images
Authors: Ai H , Wendt R
Published: July 2016

Purpose:

To assess the effect of beam hardening on measured CT HU values.

Methods:

An anthropomorphic knee phantom was scanned with the CT component of a GE Discovery 690 PET/CT scanner (120kVp, 300mAs, 40?0.625mm collimation, pitch=0.984, FOV=500mm, matrix=512?512) with four different scan setups, each of which induces different degrees of beam hardening by introducing additional attenuation media into the field of view. Homogeneous voxels representing “soft tissue” and “bone” were segmented by HU thresholding followed by a 3D morphological erosion operation which removes the non‐homogenous voxels located on the interface of thresholded tissue mask. HU values of segmented “soft tissue” and “bone” were compared.Additionally, whole‐body CT data with coverage from the skull apex to the end of toes were retrospectively retrieved from seven PET/CT exams to evaluate the effect of beam hardening in vivo. Homogeneous bone voxels were segmented with the same method previously described. Total In‐Slice Attenuation (TISA) for each CT slice, defined as the summation of HU values over all voxels within a CT slice, was calculated for all slices of the seven whole‐body CT datasets and evaluated against the mean HU values of homogeneous bone voxels within that slice.

Results:

HU values measured from the phantom showed that while “soft tissue” HU values were unaffected, added attenuation within the FOV caused noticeable decreases in the measured HU values of “bone” voxels. A linear relationship was observed between bone HU and TISA for slices of the torso and legs, but not of the skull.

Conclusion:

Beam hardening effect is not an issue of concern for voxels with HU in the soft tissue range, but should not be neglected for bone voxels. A linear relationship exists between bone HU and the associated TISA in non‐skull CT slices, which can be exploited to develop a correction strategy.
TU‐H‐207A‐04: How Patient Positioning in CT Affects More Than the AEC: Image Noise Uniformity and CT Number Changes as a Function of Positioning
Authors: Szczykutowicz T , Duplissis A , Miller D
Published: July 2016

Purpose:

Studies dealing with patient positioning in CT have mainly dealt with dose and image noise changes. For diagnosis, only dose decreases can negatively affect the diagnostic utility of the exam via an increase in image noise. However, a little studied consequence of poor positioning is CT number and noise uniformity changes.

Methods:

An anthropomorphic phantom was imaged in 2 cm vertical steps between the highest and lowest couch positions. CT number and noise were measured using regions of interest (ROI) in the upper‐thorax, mid‐thorax, and abdomen. The degree of noise non‐uniformity and CT number change was assessed by comparing values obtained in the anterior vs. posterior regions. Additionally, to add clinical support for the study, we analyzed 5,746 abdominal patients at our institution and obtained their lateral and vertical mis‐positioning from iso‐center. The patients ranged in size from teens to large adults. Box and whisker plots were used to identify the range of patient poisonings seen in our clinic.

Results:

Absolute CT number changes between anterior and posterior ROIs over 10 HU were measured for ROIs at 4 cm off‐centering. Noise uniformity varied by greater than 2 times for all regions at an offset of −10 cm. The 25–75 percentile ranges for patient positioning was −.91 – 1.4, −.87 – .88, −1.3 – .93, −1.8 – .60 cm for pediatrics, small adults, medium adults, and large adults respectively. However, 1.4% of our patients had mis‐positioning errors outside of 4 cm.

Conclusion:

The CT number changes shown here are large enough to warrant further investigation on how positioning might affect clinical decision making that relies on CT number for pathology characterization, especially due to the fact our clinical positioning data demonstrates we will have HU differences on the order of 10–20 HU.

Research support GE Healthcare. TPS supplies CT protocols to GE under a licensing agreement.
TU‐H‐207A‐06: The Effects of Various CT Tube Current Modulation (TCM) Schemes On Dose. Do You Really Know What Your TCM Scheme Is Doing?
Authors: Singhrao K , Bostani M , Hardy A , Cagnon C , McNitt‐Gray M
Published: July 2016

Purpose:

To compare the effects of various tube current modulation (TCM) schemes – including attenuation‐based, “organ‐based” and combined schemes ‐ on both the resulting tube current values as well as dose savings.

Methods:

An anthropomorphic adult thorax phantom was scanned using a Multidetector row CT scanner that offered both attenuation‐based and “organ‐based” TCM schemes that could be used separately or in combination (Definition AS64, Siemens Healthcare). A small ion chamber was attached to a medial location on the surface of the chest phantom to provide a reference value which served as proxy for organ dose. Scans were performed under each possible TCM configuration (fixed mA, attenuationbased only, organ‐based only and combined organ and attenuation based) using the same nominal parameters (e.g. Quality Reference mAs). The actual TCM scheme was extracted from the raw projection data of each scan to illustrate the actual mA variations. The scanner CTDIvol and ion chamber readings were recorded for each scan and comparisons were made across TCM schemes.

Results:

Each of the TCM schemes showed substantially different mA patterns. All TCM schemes showed some reduction in CTDIvol compared to a fixed mA scan with the same nominal settings; however the values ranged from a decrease of 2% (organ based only) to 18% (attenuation based only). The dose reduction to the surface dose point varied from a decrease of 34% (organ based only) to an increase of 15% (attenuation based only) compared to the fixed mA scan. Examining the actual TCM schemes from the raw data files allows us to understand the effects of each scheme.

Conclusion:

Phantom scans allowed us to compare the effects of different TCM schemes on both CTDIvol values as well as point doses. Future work will focus on organ doses from each scheme using validated Monte Carlo techniques.
TU‐H‐206‐06: B1 Inhomogeneity Correction for Measuring T1 From DCE MRI
Authors: Gach H , Mason N , Wang H , Tsien C , Benzinger T , Robinson C
Published: July 2016

Purpose:

3D MRI sequences typically used in DCE MRI suffer from B1 inhomogeneities associated with the slab‐selective RF pulse. B1 inhomogeneities affect the calculation of tissue T1 often used to solve the two‐compartment model. Previously, the inhomogeneities were corrected based on Bloch equation simulations of the RF pulse. However, the RF pulse specification may not be readily available or the simulation may not represent the actual scan conditions. The objective of this work was to directly measure B1 inhomogeneities and apply an inhomogeneity correction to minimize quantification errors in T1 fitting.

Methods:

We used a 3D GRE sequence with varied flip angles (2–30°) to measure T1‐weighted signals in phantoms at 3 T on a Siemens mMR. 2D EPI B1 maps were acquired to measure the B1 inhomogeneity associated with the RF coils. Inversion recovery T1 maps were acquired for ground truth. Two B1 inhomogeneity correction methods were compared: 1) A 3D segmented EPI sequence measured the RF slab selective excitation profile; and 2) The T1's of phantom standards were used to normalize the 3D GRE images.

Results:

Only the central 1/3 of the 3D GRE slices yielded accurate T1 values without correction. The slice profiles measured with 3D EPI were consistent between measurements made with different flip angles. The two correction approaches resulted in similar T1 values for at least 2/3 of the slices. Approach 2 yielded more slices with values comparable to the ground truth. However, Approach 1 resulted in less error than Approach 2 for the upper 2/3 of the slices.

Conclusion:

Using a phantom standard with a short T1 allowed us to shorten the acquisition time of the 3D EPI sequence to less than 1 minute or increase spatial resolution. The B1 inhomogeneity correction technique requires further testing in vivo for DCE MRI studies.
TU‐H‐209‐01: Acceptance Procedures for Savi, Contura and ML Mammosite
Authors: Kyriacou A.
Published: July 2016

Learnings Objectives:

Although brachytherapy is the oldest form of radiation therapy, the rapid advancement of the methods of dose calculation, treatment planning and treatment delivery pushes us to keep updating our knowledge and experience to new procedures all the time. Our purpose is to present the newest applicators used in Accelerated Partial Breast Irradiation (APBI) and the techniques of using them for a maximum effective treatment. Our objective will be to get the user familiar with the Savi, Contura and ML Mammosite from the detailed description and measurements to cavity eval and choice or size, to acceptance tests and use of each.

At the end of the session the attendants will be able to assist at the scanning of the patient for the first treatment, decide on the proper localization and immobilization devices, import the scans in the treatment planning system, perform the structure segmentation, reconstruct the catheters and develop a treatment plan using inverse planning (IPSA) or volume optimization. The attendant should be able to evaluate the quality of a treatment plan according to the ABS protocols and B39 after this session.

Our goal is that all the attendants to gain knowledge of all the quality assurance procedures required to be performed prior to a treatment, at the beginning of a treatment day, weekly, monthly and annualy on the remote afterloader, the treatment planning system and the secondary check system. We will provide tips for a consistent treatment delivery of the 10 fractions in a BID (twice daily) regimen.
TU‐H‐207B‐03: Radiomics & Regulatory Issues
Authors: Myers K.
Published: July 2016

Research and development in radiomics for precision medicine have been advancing at a rapid pace, and can be extended to eventually be mature enough for integration into clinical practice. To facilitate advances in this field, investigators need updated information on research funding, regulatory matters, and clinical translation efforts. In this special radiomics symposium, the attendee will learn of various novel funding mechanisms – both past and present – that have been used to support a number of quantitative imaging and radiomics research and resource infrastructures. In addition, a regulatory presentation will be given to provide the attendee with an understanding of when a radiomics tool might require FDA clearance or approval, and with what supporting performance data. We will end with insights from a clinical radiologist who is greatly involved in quantitative imaging in order to enable the attendee to appreciate the needs and subtleties involved in moving radiomics into the clinical workflow.

J. Boone, This is a memorial and not a funded event.
TU‐H‐207B‐04: Clinical Translation of Radiomics
Authors: Schwartz L.
Published: July 2016

Research and development in radiomics for precision medicine have been advancing at a rapid pace, and can be extended to eventually be mature enough for integration into clinical practice. To facilitate advances in this field, investigators need updated information on research funding, regulatory matters, and clinical translation efforts. In this special radiomics symposium, the attendee will learn of various novel funding mechanisms – both past and present – that have been used to support a number of quantitative imaging and radiomics research and resource infrastructures. In addition, a regulatory presentation will be given to provide the attendee with an understanding of when a radiomics tool might require FDA clearance or approval, and with what supporting performance data. We will end with insights from a clinical radiologist who is greatly involved in quantitative imaging in order to enable the attendee to appreciate the needs and subtleties involved in moving radiomics into the clinical workflow.

J. Boone, This is a memorial and not a funded event.
TU‐H‐CAMPUS‐IeP1‐02: Validation of a CT Monte Carlo Software
Authors: Schmidt R , Wulff J , Penchev P , Zink K
Published: July 2016

Purpose:

To validate the in‐house developed CT Monte Carlo calculation tool GMctdospp against reference simulation sets provided by the AAPM in the new report 195.

Methods:

Deposited energy was calculated in four segments (test 1) and two 10 cm long cylinders (test 2) inside a CTDI phantom (following case #4 of the AAPM report 195). The x‐ray point source of a given 120 kVp spectrum was collimated to a fan beam with two thicknesses (10 mm, 80 mm) for a static and a rotational setup. In addition, a given chest geometry was used to calculate deposited energy in several organs for a 0° static and a rotational beam (following case #5 of the AAPM report 195). The results of GMctdospp were compared against the particular mean value of the four quoted Monte Carlo codes (EGSnrc, Geant 4, MCNP and Penelope).

Results:

Calculated values showed no outliers in any of the cases. Differences between GMctdospp and the particular mean

Results:

Calculated values showed no outliers in any of the cases. Differences between GMctdospp and the particular mean value were always at similar magnitude compared to the quoted codes. For case #4 (CTDI phantom) the relative differences were within 1.5 %, on average 0.4 % and for case #5 (chest phantom) within 2.5 % and on average 0.85 %.

Conclusion:

The results confirmed an overall uncertainty of the Monte‐Carlo calculation chain in GMctdospp being <2.5 %, for most cases even better. This can be considered small compared to other sources of uncertainties, e.g. virtual source and patient models. The photon transport implemented in GMctdospp inside a voxel‐based patient geometry was successfully verified.
TU‐H‐CAMPUS‐IeP1‐05: A Framework for the Analytic Calculation of Patient‐Specific Dose Distribution Due to CBCT Scan for IGRT
Authors: Youn H , Kim J , Jeon H , Kim H , Cho M , Yun S , Nam J , Lee J , Lee J , Park D , Kim W , Ki Y , Kim D
Published: July 2016

Purpose:

To investigate the feasibility of an analytic framework to estimate patients’ absorbed dose distribution owing to daily cone‐beam CT scan for image‐guided radiation treatment.

Methods:

To compute total absorbed dose distribution, we separated the framework into primary and scattered dose calculations. Using the source parameters such as voltage, current, and bowtie filtration, for the primary dose calculation, we simulated the forward projection from the source to each voxel of an imaging object including some inhomogeneous inserts. Then we calculated the primary absorbed dose at each voxel based on the absorption probability deduced from the HU values and Beer's law. In sequence, all voxels constructing the phantom were regarded as secondary sources to radiate scattered photons for scattered dose calculation. Details of forward projection were identical to that of the previous step. The secondary source intensities were given by using scatter‐to‐ primary ratios provided by NIST. In addition, we compared the analytically calculated dose distribution with their Monte Carlo simulation results.

Results:

The suggested framework for absorbed dose estimation successfully provided the primary and secondary dose distributions of the phantom. Moreover, our analytic dose calculations and Monte Carlo calculations were well agreed each other even near the inhomogeneous inserts.

Conclusion:

This work indicated that our framework can be an effective monitor to estimate a patient's exposure owing to cone‐beam CT scan for image‐guided radiation treatment. Therefore, we expected that the patient's over‐exposure during IGRT might be prevented by our framework.
TU‐H‐CAMPUS‐JeP1‐04: Deformable Image Registration Performances in Pelvis Patients: Impact of CBCT Image Quality
Authors: Fusella M , Loi G , Fiandra C , Lanzi E
Published: July 2016

Purpose:

To investigate the accuracy and robustness, against image noise and artifacts (typical of CBCT images), of a commercial algorithm for deformable image registration (DIR), to propagate regions of interest (ROIs) in computational phantoms based on real prostate patient images.

Methods:

The Anaconda DIR algorithm, implemented in RayStation was tested. Two specific Deformation Vector Fields (DVFs) were applied to the reference data set (CTref) using the ImSimQA software, obtaining two deformed CTs. For each dataset twenty‐four different level of noise and/or capping artifacts were applied to simulate CBCT images. DIR was performed between CTref and each deformed CTs and CBCTs. In order to investigate the relationship between image quality parameters and the DIR results (expressed by a logit transform of the Dice Index) a bilinear regression was defined.

Results:

More than 550 DIR‐mapped ROIs were analyzed. The Statistical analysis states that deformation strenght and artifacts were significant prognostic factors of DIR performances, while noise appeared to have a minor role in DIR process as implemented in RayStation as expected by the image similarity metric built in the registration algorithm. Capping artifacts reveals a determinant role for the accuracy of DIR results. Two optimal values for capping artifacts were found to obtain acceptable DIR results (DICE> 075/ 0.85). Various clinical CBCT acquisition protocol were reported to evaluate the significance of the study.

Conclusion:

This work illustrates the impact of image quality on DIR performance. Clinical issues like Adaptive Radiation Therapy (ART) and Dose Accumulation need accurate and robust DIR software. The RayStation DIR algorithm resulted robust against noise, but sensitive to image artifacts. This result highlights the need of robustness quality assurance against image noise and artifacts in the commissioning of a DIR commercial system and underlines the importance to adopt optimized protocols for CBCT image acquisitions in ART clinical implementation.
TU‐H‐CAMPUS‐IeP2‐04: Efficient Binary Tree Description of High Resolution Breast Models for in Silico Imaging
Authors: Badal A , Graff C , Zeng R , Samuelson F , Badano A
Published: July 2016

Purpose:

We introduce a new geometric model for Monte Carlo (MC) simulation of breast tomosynthesis and mammography images with very high resolution digital breast phantoms voxelized at resolutions down to 50 microns or less. This fine sampling of the anatomy is required to reproduce the spiculated lesions and microcalcifications visible in clinical mammograms with pixel sizes under 100 microns. Phantoms voxelized at this resolution require such a large amount of computer memory that it might not be possible to execute the simulation in regular computers or in Graphics Processing Units (GPU), limiting the realism that can be achieved in virtual clinical trials.

Methods:

The standard voxel‐based geometry model used in MC codes is inefficient in terms of memory use, because uniform regions are described with a large number of identical voxels. We have developed a new geometric model based on a binary tree partition of space. The binary tree recursively divides the object in two equal halves, alternating the x, y, and z dimensions, until a uniform volume or a final voxel are found. A top‐down search of the tree structure is used to determine the exact composition of a particular voxel during the ray‐tracing process.

Results:

The binary tree geometry was implemented in PENELOPE and its GPU‐accelerated version MC‐GPU. An example tomosynthesis scan was simulated using a computational breast phantom voxelized at 50 micron. This phantom was too large to fit in the GPU memory directly, but its binary tree version required 10 times less memory. The time spend searching the binary tree reduced the simulation speed in half approximately.

Conclusion:

We have introduced a new geometry model for in silico imaging of very high resolution phantoms. The binary tree model increases the computation time but, more importantly, enables the simulation of more detailed phantoms than previously possible.
TU‐H‐CAMPUS‐TeP2‐03: High Sensitivity and High Resolution Fiber Based Micro‐Detector for Sub‐Millimeter Preclinical Dosimetry
Authors: Izaguirre E , Pokhrel S , Hedrick S , Knewtson T
Published: July 2016

Purpose:

Current precision of small animal and cell micro‐irradiators has continuously increased during the past years. Currently, preclinical irradiators can deliver sub‐millimeter fields with micrometric precision but there are no water equivalent dosimeters to determine small field profiles and dose in the orthovoltage range of energies with micrometric resolution and precision. We have developed a fiber based micro‐dosimeter with the resolution and dosimetric accuracy required for radiobiological research.

Methods:

We constructed two prototypes of micro‐dosimeters based on different compositions of fiber scintillators to study the spatial resolution and dosimetric precision of small animal and cell micro‐irradiators. The first has green output and the second has blue output. The blue output dosimeter has the highest sensitivity because it matches the spectral sensitivity of silicon photomultipliers. A blue detector with 500um cross section was built and tested respect to a CC01 ion chamber, film, and the 1500um green output detector. Orthovoltage fields from 1×1mm2 to 5×5mm2 were used for detector characteristics comparison.

Results:

The blue fiber dosimeter shows great agreement with films and matches dose measurements with the gold‐standard ion chamber for 5×5mm2 fields. The detector has the appropriate sensitivity to measure fields from 1×1mm2 to larger sizes with a 1% dosimetric accuracy. The spatial resolution is in the sub‐millimeter range and the spectral matching with the photomultiplier allows reducing the sensor cross section even further than the presented prototype. These results suggest that scintillating fibers combined with silicon photomultipliers is the appropriate technology to pursue micro‐dosimetry for small animals and disperse cell samples.

Conclusion:

The constructed detectors establish a new landmark for the resolution and sensitivity of fiber based microdetectors. The validation of the detector in our small animal and cell irradiator shows that they are appropriate for preclinical and micro single cell irradiation quality assurance and dosimetry.
TU‐H‐CAMPUS‐TeP3‐02: In‐Situ Dose Painting Using Gold Nanoparticles Released From Cylindrically Shaped Fiducials During External Beam Radiation Therapy
Authors: Mueller R , Hao Y , Hesser J , Ngwa W
Published: July 2016

Purpose:

Recent studies have shown that the presence of Gold Nanoparticles (GNPs) in tumor tissue can lead to significant dose enhancement (DE) during External Beam Radiation Therapy (EBRT). In this in‐silico study we investigate EBRT with in‐situ dose painting using GNPs released from cylindrically shaped GNP‐loaded fiducials.

Methods:

Reported Biologically Target/Tumor Volumes (BTVs) for 12 prostate carcinoma patients were employed in this study. Distribution of the GNPs after burst release from the fiducial (1.5mm diameter and 5mm length) located in the center of the spherically assumed BTV were modeled by isotropic and free diffusion without boundary condition and under the assumption of superposition. An experimentally determined diffusion coefficient for 10nm nanoparticles was adapted for investigating other GNP sizes (2, 5, 15, and 20nm) using the Stokes‐Einstein equation. The maximum size of GNPs to achieve a minimal DE Factor (DEF) of 1.1 for 6MV EBRT using a fiducial‐load of 30mg/g was calculated for typical periods of 14 and 21 days after implantation. Further, the minimal fiducial‐load needed to achieve a clinically significant DEF of 1.2 was computed for 2nm GNPs.

Results:

Results showed that a minimal DEF of 1.1 could be reached for the smallest patient BTV using a maximal GNP size of 10nm and 20nm after 14 and 21 days, respectively. With increasing BTV smaller GNPs are required to ensure the same DEF. In particular, the largest BTV requires 2nm GNPs for periods of 14 and 21 days. Meanwhile, the required fiducial‐load to reach a minimal DEF of 1.2 after 14 days was found in the range of 17mg/g and 59mg/g for all reported BTVs.

Conclusion:

This preliminary study indicates a strong dependence on GNP size and fiducial‐load to realize a significant DE. The findings avail further research towards development of GNP‐loaded fiducials for significantly enhancing radiotherapy for cancer patients.
TU‐H‐CAMPUS‐TeP3‐03: Dose Enhancement by Gold Nanoparticles Around the Bragg Peak of Proton Beams
Authors: Kwon J , Sutherland K , Hashimoto T , Peng H , Xing L , Shirato H , Date H
Published: July 2016

Purpose:

To make clear the spatial distribution of dose enhancement around gold nanoparticles (GNPs) located near the proton Bragg peak, and to evaluate the potential of GNPs as a radio sensitizer.

Methods:

The dose enhancement by electrons emitted from GNPs under proton irradiation was estimated by Geant4 Monte Carlo simulation toolkit in two steps. In an initial macroscopic step, 100 and 195 MeV proton beams were incident on a water cube, 30 cm on a side. Energy distributions of protons were calculated at four depths, 50% and 75% proximal to the Bragg peak, 100% peak, and 75% distal to the peak (P50, P75, Peak, and D75, respectively). In a subsequent microscopic step, protons with the energy distribution calculated above were incident on a 20 nm diameter GNP in a nanometer‐size water box and the spatial distribution of dose around the GNP was determined for each energy distribution. The dose enhancement factor (DEF) was also deduced.

Results:

The dose enhancement effect was spread to several tens of nanometers in the both depth and radial directions. The enhancement area increased in the order of P50, P75, Peak, and D75 for both cases with 100 and 195 MeV protons. In every position around the Bragg peak, the 100 MeV beam resulted in a higher dose enhancement than the 195 MeV beam. At P75, the average and maximum DEF were 3.9 and 17.0 for 100 MeV, and 3.5 and 16.2 for 195 MeV, respectively. These results indicate that lower energy protons caused higher dose enhancement in this incident proton energy range.

Conclusion:

The dose enhancement around GNPs spread as the position in the Bragg peak region becomes deeper and depends on proton energy. It is expected that GNPs can be used as a radio sensitizer with consideration of the location and proton beam energy.
WE‐A‐BRC‐01: Introduction to the Certificate Course
Authors: Palta J.
Published: July 2016

Quality and safety in healthcare are inextricably linked. There are compelling data that link poor quality radiation therapy to inferior patient survival. Radiation Oncology clinical trial protocol deviations often involve incorrect target volume delineation or dosing, akin to radiotherapy incidents which also often involve partial geometric miss or improper radiation dosing. When patients with radiation protocol variations are compared to those without significant protocol variations, clinical outcome is negatively impacted. Traditionally, quality assurance in radiation oncology has been driven largely by new technological advances, and safety improvement has been driven by reactive responses to past system failures and prescriptive mandates recommended by professional organizations and promulgated by regulators. Prescriptive approaches to quality and safety alone often do not address the huge variety of process and technique used in radiation oncology. Risk‐based assessments of radiotherapy processes provide a mechanism to enhance quality and safety, both for new and for established techniques. It is imperative that we explore such a paradigm shift at this time, when expectations from patients as well as providers are rising while available resources are falling. There is much we can learn from our past experiences to be applied towards the new risk‐based assessments.

Learning Objectives:

Understand the impact of clinical and technical quality on outcomes

Understand the importance of quality care in radiation oncology

Learn to assess the impact of quality on clinical outcomes

D. Followill, NIH Grant CA180803
WE‐AB‐BRB‐03: Real‐Time Volumetric Scintillation Dosimetry for Radiation Therapy
Authors: Beddar S.
Published: July 2016

Despite widespread IMRT treatments at modern radiation therapy clinics, precise dosimetric commissioning of an IMRT system remains a challenge. In the most recent report from the Radiological Physics Center (RPC), nearly 20% of institutions failed an end‐to‐end test with an anthropomorphic head and neck phantom, a test that has rather lenient dose difference and distance‐to‐agreement criteria of 7% and 4 mm. The RPC report provides strong evidence that IMRT implementation is prone to error and that improved quality assurance tools are required. At the heart of radiation therapy dosimetry is the multidimensional dosimeter. However, due to the limited availability of water‐equivalent dosimetry materials, research and development in this important field is challenging. In this session, we will review a few dosimeter developments that are either in the laboratory phase or in the pre‐commercialization phase. 1) Radiochromic plastic. Novel formulations exhibit light absorbing optical contrast with very little scatter, enabling faster, broad beam optical CT design. 2) Storage phosphor. After irradiation, the dosimetry panels will be read out using a dedicated 2D scanning apparatus in a non‐invasive, electro‐optic manner and immediately restored for further use. 3) Liquid scintillator. Scintillators convert the energy from x‐rays and proton beams into visible light, which can be recorded with a scientific camera (CCD or CMOS) from multiple angles. The 3D shape of the dose distribution can then be reconstructed. 4) Cherenkov emission imaging. Gated intensified imaging allows video‐rate passive detection of Cherenkov emission during radiation therapy with the room lights on.

Learning Objectives:

To understand the physics of a variety of dosimetry techniques based upon optical imaging

To investigate the strategies to overcome respective challenges and limitations

To explore novel ideas of dosimeter design

Supported in part by NIH Grants R01CA148853, R01CA182450, R01CA109558. Brian Pogue is founder and president of the company DoseOptics LLC, dedicated to developing and commercializing the first dedicated Cerenkov imaging camera and system for radiation dose imaging. Work reported in this talk does not involve the use of DoseOptics technology.; H. Li, this work was supported in part by NIH Grant No. R01CA148853; S. Beddar, NIH funding R01‐CA182450
WE‐AB‐BRA‐03: Non‐Invasive Controlled Release from Implantable Hydrogel Scaffolds Using Ultrasound
Authors: Moncion A , Kripfgans O.D , Putnam A.J , Frances chi R.T , Fabiilli M.L
Published: July 2016

Purpose:

To control release of a model payload in acoustically responsive scaffolds (ARSs) using focused ultrasound (FUS).

Methods:

Fluorescently‐labeled dextran (10 kDa) was encapsulated in sonosensitive perfluorocarbon (C6F14 or C5F12) double emulsions (mean diameter: 2.9±0.1 µm). For in vitro release studies, 0.5 mL ARSs (10 mg/mL fibrin, 1% (v/v) emulsion) were polymerized in 24 well plates and covered with 0.5 mL medium. Starting one day after polymerization, ARSs were exposed to FUS (2.5 MHz, Pr = 8 MPa, 13 cycles, 100 Hz PRF) for 2 min daily. The amount of dextran released into the media was quantified. For in vivo studies, 0.25 mL ARSs were prepared as described previously and injected subcutaneously in the lower back of BALB/c mice. After polymerization, a subset of the implanted ARSs were exposed to FUS (as previously described). Animals were imaged longitudinally using a fluorescence imaging system to quantify the amount of dextran released from the ARSs.

Results:

In vitro: Over 6 days, +FUS displayed an 8.2‐fold increase in dextran release compared to −FUS (−FUS: 2.7±0.6%; +FUS: 22.2±3.0%) for C6F14 ARSs, and a 6.7‐fold increase (−FUS: 5.0±0.8%; +FUS: 38.5±1.6%) for C5F12:C6F14 ARSs. In vivo: +FUS displayed statistically greater dextran release compared to −FUS one day after implantation for C5F12:C6F14 ARSs (−FUS: 55.1±1.5%; +FUS: 74.1±2.2%) and three days after implantation for C6F14 ARSs (−FUS: 1.4±6.5%; +FUS: 30.4±5.4%).

Conclusion:

FUS enables non‐invasive control of payload release from an ARS, which could benefit growth factor delivery for tissue regeneration. ARS are versatile due to their tunability (i.e. stiffness, emulsion composition, FUS pressure, FUS frequency, etc.) and can be modified to for optimal payload release. Future work will optimize ARS formulations for in vivo use to minimize payload release in the absence of FUS.

This work was supported by NIH Grant R21 AR065010 (M.L. Fabiilli) and the Basic Radiologic Sciences Innovative Research Award (M.L. Fabiilli). A. Moncion is supported by the National Science Foundation Graduate Student Research Fellowship (Grant DGE 1256260).
WE‐AB‐BRA‐10: Assessment of Fiber Bragg Grating (FBG)‐Based Sensing for Real‐Time Needle Tracking During MR‐Guided Brachytherapy
Authors: Borot de Battisti M , Denis de Senneville B , Maenhout M , Hautvast G , Binnekamp D , Lagendijk J J W , Van Vulpen M , Moerland M A
Published: July 2016

Purpose:

This study assesses the potential of Fiber Bragg Grating (FBG)‐based sensing for real‐time needle (including catheter or tube) tracking during MR‐guided HDR brachytherapy.

Methods:

The proposed FBG‐based sensing tracking approach involves a MR‐compatible stylet composed of three optic fibers with nine sets of embedded FBG sensors each. When the stylet is inserted inside the lumen of the needle, the FBG sensing system can measure the needle's deflection. For localization of the needle in physical space, the position and orientation of the stylet base are mandatory. For this purpose, we propose to fix the stylet base and determine its position and orientation using a MR‐based calibration as follows. First, the deflection of a needle inserted in a phantom in two different configurations is measured during simultaneous MR‐imaging. Then, after segmentation of the needle shapes on the MR‐images, the position and orientation of the stylet base is determined using a rigid registration of the needle shapes on both MR and FBG‐based measurements. The calibration method was assessed by measuring the deflection of a needle in a prostate phantom in five different configurations using FBG‐based sensing during simultaneous MR‐imaging. Any two needle shapes were employed for the calibration step and the proposed FGB‐tracking approach was subsequently evaluated on the other three needles configurations. The tracking accuracy was evaluated by computing the Euclidian distance between the 3D FBG vs. MR‐based measurements.

Results:

Over all needle shapes tested, the average(standard deviation) Euclidian distance between the FBG and MR‐based measurements was 0.79mm(0.37mm). The update rate and latency of the FBG‐based measurements were 100ms and 300ms respectively.

Conclusion:

The proposed FBG‐based protocol can measure the needle position with an accuracy, precision, update rate and latency eligible for accurate needle steering during MR‐guided HDR brachytherapy.

M. Borot de Battisti is funded by Philips Medical Systems Nederland B.V.; M. Moerland is principal investigator on a contract funded by Philips Medical Systems Nederland B.V.; G. Hautvast and D. Binnekamp are fulltime employees of Philips Medical Systems Nederland B.V.
WE‐AB‐202‐02: Incorporating Regional Ventilation Function in Predicting Radiation Fibrosis After Concurrent Chemoradiotherapy for Lung Cancer
Authors: Lan F , Jeudy J , Senan S , van Sornsen de Koste J , Tseng H , Zhou J , D'Souza W , Zhang H
Published: July 2016

Purpose:

To investigate the incorporation of pre‐therapy regional ventilation function in predicting radiation fibrosis (RF) in stage III non‐small‐cell lung cancer (NSCLC) patients treated with concurrent thoracic chemoradiotherapy.

Methods:

37 stage III NSCLC patients were retrospectively studied. Patients received one cycle of cisplatin‐gemcitabine, followed by two to three cycles of cisplatin‐etoposide concurrently with involved‐field thoracic radiotherapy between 46 and 66 Gy (2 Gy per fraction). Pre‐therapy regional ventilation images of the lung were derived from 4DCT via a density‐change‐based image registration algorithm with mass correction. RF was evaluated at 6‐months post‐treatment using radiographic scoring based on airway dilation and volume loss. Three types of ipsilateral lung metrics were studied: (1) conventional dose‐volume metrics (V20, V30, V40, and mean‐lung‐dose (MLD)), (2) dose‐function metrics (fV20, fV30, fV40, and functional mean‐lung‐dose (fMLD) generated by combining regional ventilation and dose), and (3) dose‐subvolume metrics (sV20, sV30, sV40, and subvolume mean‐lung‐dose (sMLD) defined as the dose‐volume metrics computed on the sub‐volume of the lung with at least 60% of the quantified maximum ventilation status). Receiver operating characteristic (ROC) curve analysis and logistic regression analysis were used to evaluate the predictability of these metrics for RF.

Results:

In predicting airway dilation, the area under the ROC curve (AUC) values for (V20, MLD), (fV20, fMLD), and (sV20, and sMLD) were (0.76, 0.70), (0.80, 0.74) and (0.82, 0.80), respectively. The logistic regression p‐values were (0.09, 0.18), (0.02, 0.05) and (0.004, 0.006), respectively. With regard to volume loss, the corresponding AUC values for these metrics were (0.66, 0.57), (0.67, 0.61) and (0.71, 0.69), and p‐values were (0.95, 0.90), (0.43, 0.64) and (0.08, 0.12), respectively.

Conclusion:

The inclusion of regional ventilation function improved predictability of radiation fibrosis. Dose‐subvolume metrics provided a promising method for incorporating functional information into the conventional dose‐volume parameters for outcome assessment.
WE‐AB‐202‐04: Statistical Evaluation of Lung Function Using 4DCT Ventilation Imaging: Proton Therapy VS IMRT
Authors: Huang Q , Zhang M , Chen T , Yue N , Zou J
Published: July 2016

Purpose:

Variation in function of different lung regions has been ignored so far for conventional lung cancer treatment planning, which may lead to higher risk of radiation induced lung disease. 4DCT based lung ventilation imaging provides a novel yet convenient approach for lung functional imaging as 4DCT is taken as routine for lung cancer treatment. Our work aims to evaluate the impact of accounting for spatial heterogeneity in lung function using 4DCT based lung ventilation imaging for proton and IMRT plans.

Methods:

Six patients with advanced stage lung cancer of various tumor locations were retrospectively evaluated for the study. Proton and IMRT plans were designed following identical planning objective and constrains for each patient. Ventilation images were calculated from patients’ 4DCT using deformable image registration implemented by Velocity AI software based on Jacobian‐metrics. Lung was delineated into two function level regions based on ventilation (low and high functional area). High functional region was defined as lung ventilation greater than 30%. Dose distribution and statistics in different lung function area was calculated for patients.

Results:

Variation in dosimetric statistics of different function lung region was observed between proton and IMRT plans. In all proton plans, high function lung regions receive lower maximum dose (100.2%–108.9%), compared with IMRT plans (106.4%–119.7%). Interestingly, three out of six proton plans gave higher mean dose by up to 2.2% than IMRT to high function lung region. Lower mean dose (lower by up to 14.1%) and maximum dose (lower by up to 9%) were observed in low function lung for proton plans.

Conclusion:

A systematic approach was developed to generate function lung ventilation imaging and use it to evaluate plans. This method hold great promise in function analysis of lung during planning. We are currently studying more subjects to evaluate this tool.
WE‐AB‐202‐12: Voxel‐Wise Analysis of Apparent Diffusion Coefficient and Perfusion Maps in Multi‐Parametric MRI of Prostate Cancer
Authors: Engstroem K , Casares‐Magaz O , Roervik J , Andersen E , Muren L
Published: July 2016

Purpose:

Multi‐parametric MRI (mp‐MRI) is being introduced in radiotherapy (RT) of prostate cancer, including for tumour delineation in focal boosting strategies. We recently developed an image‐based tumour control probability model, based on cell density distributions derived from apparent diffusion coefficient (ADC) maps. Beyond tumour volume and cell densities, tumour hypoxia is also an important determinant of RT response. Since tissue perfusion from mp‐MRI has been related to hypoxia we have explored the patterns of ADC and perfusion maps, and the relations between them, inside and outside prostate index lesions.

Methods:

ADC and perfusion maps from 20 prostate cancer patients were used, with the prostate and index lesion delineated by a dedicated uro‐radiologist. To reduce noise, the maps were averaged over a 3×3×3 voxel cube. Associations between different ADC and perfusion histogram parameters within the prostate, inside and outside the index lesion, were evaluated with the Pearson's correlation coefficient. In the voxel‐wise analysis, scatter plots of ADC vs perfusion were analysed for voxels in the prostate, inside and outside of the index lesion, again with the associations quantified with the Pearson's correlation coefficient.

Results:

Overall ADC was lower inside the index lesion than in the normal prostate as opposed to ktrans that was higher inside the index lesion than outside. In the histogram analysis, the minimum ktrans was significantly correlated with the maximum ADC (Pearson=0.47; p=0.03). At the voxel level, 15 of the 20 cases had a statistically significant inverse correlation between ADC and perfusion inside the index lesion; ten of the cases had a Pearson < −0.4.

Conclusion:

The minimum value of ktrans across the tumour was correlated to the maximum ADC. However, on the voxel level, the ‘local’ ktrans in the index lesion is inversely (i.e. negatively) correlated to the ‘local’ ADC in most patients.

Research agreement with Varian Medical Systems, not related to the work presented in this abstract.
WE‐AB‐207A‐09: Optimization of the Design of a Moving Blocker for Cone‐Beam CT Scatter Correction: Experimental Evaluation
Authors: Chen X , Ouyang L , Yan H , Jia X , Zhang Y , Wang J
Published: July 2016

Purpose:

A moving blocker based strategy has shown promising results for scatter correction in cone‐beam computed tomography (CBCT). Different geometry designs and moving speeds of the blocker affect its performance in image reconstruction accuracy. The goal of this work is to optimize the geometric design and moving speed of the moving blocker system through experimental evaluations.

Methods:

An Elekta Synergy XVI system and an anthropomorphic pelvis phantom CIRS 801‐P were used for our experiment. A blocker consisting of lead strips was inserted between the x‐ray source and the phantom moving back and forth along rotation axis to measure the scatter signal. Accoriding to our Monte Carlo simulation results, three blockers were used, which have the same lead strip width 3.2mm and different gap between neighboring lead strips, 3.2, 6.4 and 9.6mm. For each blocker, three moving speeds were evaluated, 10, 20 and 30 pixels per projection (on the detector plane). Scatter signal in the unblocked region was estimated by cubic B‐spline based interpolation from the blocked region. CBCT image was reconstructed by a total variation (TV) based algebraic iterative reconstruction (ART) algorithm from the partially blocked projection data. Reconstruction accuracy in each condition is quantified as CT number error of region of interest (ROI) by comparing to a CBCT reconstructed image from analytically simulated unblocked and scatter free projection data.

Results:

Highest reconstruction accuracy is achieved when the blocker width is 3.2 mm, the gap between neighboring lead strips is 9.6 mm and the moving speed is 20 pixels per projection. RMSE of the CT number of ROIs can be reduced from 436 to 27.

Conclusions:

Image reconstruction accuracy is greatly affected by the geometry design of the blocker. The moving speed does not have a very strong effect on reconstruction result if it is over 20 pixels per projection.