bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐F‐T‐674: In Vitro Study of 5‐Aminolevulinic Acid‐Mediated Photo Dynamic Therapy in Human Cancer Cell Lines
Authors: Cvetkovic D , Wang B , Gupta R , Ma C
Published: July 2016

Purpose:

Photodynamic therapy (PTD) is a promising cancer treatment modality. 5‐sminolevulinic acid (ALA) is a clinically approved photosensitizer. Here we studied the effect of 5‐ALA administration with irradiation on several cell lines in vitro.

Methods:

Human head and neck (FaDu), lung (A549) and prostate (LNCaP) cancer cells (104/well) were seeded overnight in 96‐well plates (Figure 1). 5‐ALA at a range from 0.1 to 30.0mg/ml was added to confluent cells 3h before irradiation in 100ul of culture medium. 15MV photon beams from a Siemens Artiste linear accelerator were used to deliver 2 Gy dose in one fraction to the cells. Cell viability was evaluated by WST1 assay. The development of orange color was measured 3h after the addition of WST‐1 reagent at 450nm on an Envision Multilabel Reader (Figure 2) and directly correlated to cell number. Control, untreated cells were incubated without 5‐ALA. The experiment was performed twice for each cell line.

Results:

The cell viability rates for the head and neck cancer line are shown in Figure 3. FaDu cell viability was reduced significantly to 36.5% (5‐ALA) and 18.1% (5‐ALA + RT) only at the highest concentration of 5‐ALA, 30mg/ml. This effect was observed in neither A549, nor LNCaP cell line. No toxicity was detected at lower 5‐ALA concentrations.

Conclusion:

Application of 5‐ALA and subsequent PDT was found to be cytotoxic at the highest dose of the photosensitizer used in the FaDu head and neck cell line, and their effect was synergistic. Further efforts are necessary to study the potential therapeutic effects of 5‐ALA PTD in vitro and in vivo. Our results suggest 5‐ALA may improve the efficacy of radiotherapy by acting as a radiomediator in head and neck cancer.
SU‐F‐T‐675: Down‐Regulating the Expression of Cdc42 and Inhibition of Migration of A549 with Combined Treatment of Ionizing Radiation and Sevoflurane
Authors: Feng Y , Feng J , Huang Z
Published: July 2016

Purpose:

Cdc42 is involved in cell transformation, proliferation, invasion and metastasis of human cancer cells. Cdc42 overexpression has been reported in several types of cancers. This study investigated the combined treatment effects of ionizing radiation and sevoflurane on down‐regulating Cdc42 expression and suppressing migration of human adenocarcinoma cell line A549.

Methods:

Samples of A549 cells with Cdc42 overexpression were created and Cdc42 expression was determined by Western blotting. Increase of migration speed by Cdc42‐HA overexpression was confirmed with an initial in‐vitro scratch assay. The cells grown in culture media were separated into 2 groups of 6 samples: one for the control and the other was treated with 4% sevoflurane for 5hrs prior to a single‐fraction radiation of 4Gy using a 6MV beam. Cell migration speeds of the 2 groups were measured with an initial in‐vitro scratch assay. The scratch was created with a pipette tip immediately after treatment and images at 4 post‐treatment time points (0h, 3h, 6h, 12h) were acquired. The distance between the two separated sides at 0h was used as reference and subsequent changes of the distance over time was defined as the cell migration speed. Image processing and measurement were performed with an in‐house software. The experiment was repeated three times independently to evaluate the repeatability and reliability. Statistical analysis was performed with SPSS 19.0.

Results:

Western blotting showed the treatment down‐regulated Cdc42 overexpression. Quantitative analysis and two‐tailed t‐test showed that cell migration speed of the treated group was higher than the control group at all time points after treatment (p < 0.02).

Conclusion:

Combined treatment of 6MV photon and sevoflurane can cause the effects of down‐regulating Cdc42 overexpression and decrease of migration speed of A549 cells which provides potential of clinical benefit for the cancer therapy. More investigation is needed to further quantify the benefits of the combined therapy.
SU‐F‐T‐678: Clotrimazole Sensitizes MCF‐7 Breast Cancer Cell Line to Radiation
Authors: Garcia L , Tambasco M
Published: July 2016

Purpose:

To study the effects of Clotrimazole (CLT) on radiosensitivity of MCF‐7 Cells in correlation to detachment of Hexokinase II from the Voltage Dependent Anion Channel on the outer membrane of the mitochondria. Apoptotic fractions were also analyzed in relation to the detachment of Hexokinase.

Methods:

This study focused on the mammary adenocarcinoma cell line, MCF‐7. Colony forming assays were used to analyze radiosensitization by CLT. Flow cytometry methods were used to analyze apoptotic vs necrotic fractions after treatment with CLT. Spectrophotometery was used to analyze the mitochondrial bound and soluble fraction of Hexokinase by means of relative enzymatic activity.

Results:

Our preliminary data have shown that CLT sensitizes MCF‐7 cells to radiation in a dose and incubation time dependent manner up. We have also demonstrated that there are two radiosensitizing periods in MCF‐7 cells with the first corresponding to the cycle arrest after 24 hours observed in other cell lines. The second radiosensitizing period occurs with incubation in CLT after irradiation which reaches maximum effect around 24 hours of incubation time. Preliminary data from our Hexokinase detachment assay show a factor of two increase in the ratio of unbound to bound Hexokinase when comparing incubation for 24 hours in media containing 0 and 20 µM CLT.

Conclusion:

This study and others indicate CLT as a possible radiosensitizing agent in cancer therapies. While CLT itself shows toxicity to the liver in high doses, this study further demonstrates that disruption of the Warburg Effect and unbinding of mitochondrial bound Hexokinase as a possible pathway for cancer treatment.
SU‐G‐206‐03: CTDI Per KV at Phantom Center and Periphery: Comparison Between Major CT Manufacturers
Authors: Al‐Senan R , Demirkaya O
Published: July 2016

Purpose:

The purpose of this study was to: 1) compare scanners output by measuring normalized CTDIw (mGy/100mAs) in different CT makes and models and at different kV's, and 2) quantify the relationship between kV and CTDI and compare this relationship between the different manufacturers.

Methods:

Study included forty scanners of major CT manufacturers and of various models. Exposure was measured at center and 12 o'clock holes of head and body CTDI phantoms, at all available kV's, and with the largest or second largest available collimation in each scanner. Average measured CTDI's from each CT manufacturer were also plotted against kV and the fitting equation: CTDIw (normalized) = a.kVb was calculated. The power (b) value may be considered as an indicator of spectral filtration, which affects the degree of beam hardening. Also, HVLs were measured at several scanners.

Results:

Results showed GE scanners, on average, had higher normalized CTDIw than those of Siemens and Philips, in both phantom sizes and at all kV's. ANOVA statistic indicated the difference was statistically significant (p < 0.05). Comparison between Philips and Siemens, however, was not statistically significant. Curve fitting showed b values ranged from 2.4 to 2.9 (for Head periphery and center, respectively); and was about 2.8 for Body phantom periphery, and 3.2 at the center of Body phantom. Fitting equations (kV vs. CTDI) will be presented and discussed. GE's CTDIw vs. HVL showed very strong correlation (r > 0.99).

Conclusion:

Partial characterization of scanners output was performed which may be helpful in dose estimation to internal organs. The relatively higher output from GE scanners may be attributed to lower filtration. Work is still in progress to obtain CTDI values from other scanners as well as to measure their HVLs.
SU‐G‐206‐06: Analytic Dose Function for CT Scans in Infinite Cylinders as a Function of Scan Length and Cylinder Radius
Authors: Bakalyar D , Feng W , McKenney S
Published: July 2016

Purpose:

The radiation dose absorbed at a particular radius ρ within the central plane of a long cylinder following a CT scan is a function of the length of the scan L and the cylinder radius R along with kVp and cylinder composition. An analytic function was created that that not only expresses these dependencies but is integrable in closed form over the area of the central plane. This feature facilitates explicit calculation of the planar average dose. The “approach to equilibrium” h(L) discussed in the TG111 report is seamlessly included in this function.

Methods:

For a cylindrically symmetric radiation field, Monte Carlo calculations were performed to compute the dose distribution to long polyethylene cylinders for scans of varying L for cylinders ranging in radius from 5 to 20 cm. The function was developed from the resultant Monte Carlo data. In addition, the function was successfully fit to data taken from measurements on the 30 cm diameter ICRU/TG200 phantom using a real‐time dosimeter.

Results:

Symmetry and continuity dictate a local extremum at the center which is a minimum for the larger sizes. There are competing effects as the beam penetrates the cylinder from the outside: attenuation, resulting in a decrease; scatter, abruptly increasing at the circumference. This competition may result in an absolute maximum between the center and outer edge leading to a “gull wing” shape for the radial dependence. For the smallest cylinders, scatter may dominate to the extent that there is an absolute maximum at the center.

Conclusion:

An integrable, analytic function has been developed that provides the radial dependency of dose for the central plane of a scan of length L for cylinders of varying diameter. Equivalently, we have developed h(L,R,ρ).
SU‐G‐206‐07: Dual‐Energy CT Inter‐ and Intra‐Scanner Variability Within One Make and Model
Authors: Jacobsen M , Wood C , Cody D
Published: July 2016

Purpose:

It can be logistically quite difficult to scan patients on the same exact device for their repeat visits in multi‐scanner facilities. The reliability between dual‐energy CT scanners’ quantitative results is not known, nor is their individual repeatability. Therefore, we evaluated inter‐ and intra‐scanner variability with respect to several key clinical quantitative metrics specific to dual‐energy CT.

Methods:

Eleven identical GE HD‐750 CT scanners in a busy clinical environment were used to perform dual‐energy (DE) CT scans of a large elliptical quality control (QC) phantom (Gammex, Inc.; Middleton, WI) which contains many standard insert materials. The DE‐QC phantom was scanned bi‐weekly during 2016; 3 to 4 scans were obtained from each scanner (a total of 35 data sets were used for analysis). Iodine accuracy for the 2mg/ml, 5mg/ml and 15mg/ml rods (from the Iodine(Water) image set) and soft tissue HU (40 HU based on NIST constants) from the 50keV data set were used to assess inter‐ and intra‐scanner variability (standard deviation).

Results:

Intra‐scanner variability average for 2mg/ml Iodine was 0.10 mg/ml (range 0.05–0.15 mg/ml), for 5mg/ml Iodine was 0.12 mg/ml (range 0.07–0.16 mg/ml), for 15 mg/ml Iodine was 0.25 mg/ml (range 0.16–0.37 mg/ml), and for the soft tissue inserts was 2.1 HU (range 1.8–2.6 HU). Inter‐scanner variability average for 2mg/ml Iodine was 0.16 mg/ml (range 0.11–0.19 mg/ml), for 5mg/ml Iodine was 0.18 mg/ml (range 0.11–0.22 mg/ml), for 15 mg/ml Iodine was 0.35 mg/ml (range 0.23–0.44 mg/ml), and for the soft tissue inserts was 3.8 HU (range 3.1–4.5 HU).

Conclusion:

Intra‐scanner variability for the iodine and soft tissue inserts averaged 3.1% and 5.2% respectively, and inter‐scanner variability for these regions analyzed averaged 5.0% and 9.5%, respectively. Future work will include determination of smallest measurable change and acceptable limits for DE‐CT scanner variability over longer time intervals.

This research has been supported by funds from Dr. William Murphy, Jr., the John S. Dunn, Sr. Distinguished Chair in Diagnostic Imaging at MD Anderson Cancer Center.
SU‐G‐206‐13: Validating Dose Split: A Method to Image the Same Patient at Multiple Doses with a Single CT Acquisition
Authors: Solomon J , Zhang Y , Marin D , Samei E
Published: July 2016

Purpose:

Dose optimization studies in CT have a need for images acquired at multiple dose levels. This presents ethical and logistical challenges for performing such research with human subjects. As a result, most studies rely on phantom data. The purpose of this study was to perform a physics‐based validation of a method to obtain images of the same patient at multiple dose levels using a single CT acquisition on a dual‐source CT system.

Methods:

The Dose Split (DS) method relies on acquiring raw projection data simultaneously from two separate sources/detectors (denoted Tube A and Tube B) on a dual‐source system. By distributing the dose unevenly between Tube A and Tube B (at the same kVp), it is possible to reconstruct images corresponding to any dose in the range of min(A,B) to A+B. CT data of the ACR phantom were acquired on a dual‐source system (SOMATOM Flash, Siemens Healthcare) with a traditional single‐source (SS) technique at 6 dose levels (25, 50, 75, 100, 150, and 200 mAs). Corresponding data using the DS technique were acquired and compared with the SS data in terms of noise magnitude (pixel STD), contrast, contrast‐to‐noise ratio, noise power spectrum (average spatial frequency), modulation transfer function (50% frequency) and detectability index (for a non‐prewhitening matched filter observer).

Results:

Between the DS and SS techniques, the differences (SS–DS) in noise magnitude, contrast, and CNR were on average (across doses) 1.2 HU (4.1%), 0.7 HU (11%), and 0.02 (6.9%), respectively. The differences in NPS average frequency, MTF 50% frequency, and detectability index were 0.01 cycles/mm (2.5%), 0.03 cycles/mm (7.5%), and −.03 (−6.8%), respectively.

Conclusion:

The dose split method can be used to acquire images of the same patient equivalent to many dose levels in a single acquisition. Differences in noise, CNR, NPS, MTF, and detectability were all negligible.
SU‐G‐IeP1‐07: Inaccuracy of Lesion Blood Flow Quantification Related to the Proton Density Reference Image in Arterial Spin Labeling MRI of Brain Tumors
Authors: Jen M , Johnson J , Hou P , Liu H
Published: July 2016

Purpose:

Cerebral blood flow quantification in arterial spin labeling (ASL) MRI requires an estimate of the equilibrium magnetization of blood, which is often obtained by a set of proton density (PD) reference image. Normally, a constant blood‐brain partition coefficient is assumed across the brain. However, this assumption may not be valid for brain lesions. This study aimed to evaluate the impact of lesion‐related PD variations on ASL quantification in patients with brain tumors.

Methods:

MR images for posttreatment evaluation of 42 patients with brain tumors were retrospectively analyzed. These images were acquired on a 3T MRI scanner, including T2‐weighted FLAIR, 3D pseudo‐continuous ASL and post‐contrast T1‐weighted images. Anatomical images were coregistered with ASL images using the SPM software. Regions of interest (ROIs) of the enhancing and FLAIR lesions were manually drawn on the coregistered images. ROIs of the contralateral normal appearing tissues were also determined, with the consideration of approximating coil sensitivity patterns in lesion ROIs. Relative lesion blood flow (lesion/contralateral tissue) was calculated from both the CBF map (dependent on the PD) and the ΔM map for comparison.

Results:

The signal intensities in both enhancing and FLAIR lesions were significantly different than contralateral tissues on the PD reference image (p<0.001). The percent signal difference ranged from −15.9 to 19.2%, with a mean of 5.4% for the enhancing lesion, and from −2.8 to 22.9% with a mean of 10.1% for the FLAIR lesion. The high/low lesion‐related PD signal resulted in inversely proportional under‐/over‐estimation of blood flow in both enhancing and FLAIR lesions.

Conclusion:

Significant signal differences were found between lesions and contralateral tissues in the PD reference image, which introduced errors in blood flow quantification in ASL. The error can be up to 20% in individual patients with an average of 5‐ 10% for the group of patients with brain tumors.
SU‐G‐IeP1‐11: Resting‐State Fluctuation of BOLD Signal Amplitude for Mapping Cerebrovascular Reactivity in Presurgical Functional MRI
Authors: Wang P , Hou P , Kesler S , Colen R , Kumar A , Prabhu S , Liu H
Published: July 2016

Purpose:

Cerebrovascular reactivity (CVR) MRI with hypercapnia challenges, such as a breath‐hold (BH) task, has been proposed to indicate areas with neurovascular uncoupling potentials for presurgical functional MRI (fMRI). This study aimed to explore the use of resting‐state (RS) fMRI, in particular, the RS fluctuation of amplitude (RSFA) for detecting the impaired CVR and compare with BH MRI in patients with gliomas.

Methods:

The BH and RS fMRI from six patients as part of their presurgical fMRI studies were analyzed. Functional images were coregistered to the 3D T1‐weighted images and spatially smoothed using a 4‐mm Gaussian kernel. A band‐pass filter (0.01–0.08 Hz) was then applied to the RS time series. Temporal standard deviations of the BH and the filtered RS signal changes were computed for each voxel to indicate CVR and subsequently transformed to Z‐scores. For quantitative comparison, a region of interest (ROI) with significant CVR in the sensorimotor cortex on the contralateral side of the tumor was determined for each patient as Z‐scores greater than 50% of the local maxima. In addition, a tumor ROI was determined by referencing the T2 FLAIR and post‐contrast T1‐weighted images of each patient.

Results:

Significant cross‐subject correlations between the BH CVR and RSFA were found in both the sensorimotor and tumor ROIs (r=0.59, p<0.05 and r=0.83, p<0.05, respectively). Within individuals, voxel‐based analyses showed significant correlations between two methods in both ROIs in all patients. The spatial patterns of BH CVR and RSFA maps appeared similar across the brain with sparse local discrepancies.

Conclusion:

The RSFA derived from RS‐fMRI is a promising method for probing impaired CVR in presurgical fMRI mapping. Unlike BH, RS‐fMRI is less dependent on patient performance. In addition, with its proven relation to neural activity, RSFA of certain frequency bands has potentials to better indicate the neurovascular uncoupling.
SU‐G‐IeP1‐15: Towards Accurate Cerebral Blood Flow Quantification with Distortion‐ Corrected Pseudo‐Continuous Arterial Spin Labeling
Authors: Hoff M , Rane‐Levandovsky S , Andre J
Published: July 2016

Purpose:

Traditional arterial spin labeling (ASL) acquisitions with echo planar imaging (EPI) readouts suffer from image distortion due to susceptibility effects, compromising ASL's ability to accurately quantify cerebral blood flow (CBF) and assess disease‐specific patterns associated with CBF abnormalities. Phase labeling for additional coordinate encoding (PLACE) can remove image distortion; our goal is to apply PLACE to improve the quantitative accuracy of ASL CBF in humans.

Methods:

Four subjects were imaged on a 3T Philips Ingenia scanner using a 16‐channel receive coil with a 21/21/10cm (frequency/phase/slice direction) field‐of‐view. An ASL sequence with a pseudo‐continuous ASL (pCASL) labeling scheme was employed to acquire thirty dynamics of single‐shot EPI data, with control and label datasets for all dynamics, and PLACE gradients applied on odd dynamics. Parameters included a post‐labeling delay = 2s, label duration = 1.8s, flip angle = 90°, TR/TE = 5000/23.5ms, and 2.9/2.9/5.0mm (frequency/phase/slice direction) voxel size. “M0” EPI‐reference images and T1‐weighted spin‐echo images with 0.8/1.0/3.3mm (frequency/phase/slice directions) voxel size were also acquired. Complex conjugate image products of pCASL odd and even dynamics were formed, a linear phase ramp applied, and data expanded and smoothed. Data phase was extracted to map control, label, and M0 magnitude image pixels to their undistorted locations, and images were rebinned to original size. All images were corrected for motion artifacts in FSL 5.0. pCASL images were registered to M0 images, and control and label images were subtracted to compute quantitative CBF maps.

Results:

pCASL image and CBF map distortions were removed by PLACE in all subjects. Corrected images conformed well to the anatomical T1‐weighted reference image, and deviations in corrected CBF maps were evident.

Conclusion:

Eliminating pCASL distortion with PLACE can improve CBF quantification accuracy using minimal pulse sequence modifications and no additional scan time, improving ASL's clinical applicability.
SU‐G‐JeP1‐01: A Combination of Real Time Electromagnetic Localization and Tracking with Cone Beam Computed Tomography in Stereotactic Radiosurgery for Brain Tumors
Authors: Muralidhar K Raja , Pangam Suresh , Ponaganti Srinivas , Krishna Jayarama , Sujana Kolla V , Komanduri Priya K
Published: July 2016

Purpose:

1. online verification of patient position during treatment using calypso electromagnetic localization and tracking system. 2. Verification and comparison of positional accuracy between cone beam computed tomography and calypso system. 3. Presenting the advantage of continuation localization in Stereotactic radiosurgery treatments.

Methods:

Ten brain tumor cases were taken for this study. Patients with head mask were under gone Computed Tomography (CT). Before scanning, mask was cut on the fore head area to keep surface beacons on the skin. Slice thickness of 0.65 mm were taken for this study. x, y, z coordinates of these beacons in TPS were entered into tracking station. Varian True Beam accelerator, equipped with On Board Imager was used to take Cone beam Computed Tomography (CBCT) to localize the patient. Simultaneously Surface beacons were used to localize and track the patient throughout the treatment. The localization values were compared in both systems. For localization CBCT considered as reference. Tracking was done throughout the treatment using Calypso tracking system using electromagnetic array. This array was in tracking position during imaging and treatment. Flattening Filter free beams of 6MV photons along with Volumetric Modulated Arc Therapy was used for the treatment. The patient movement was observed throughout the treatment ranging from 2 min to 4 min.

Results:

The average variation observed between calypso system and CBCT localization was less than 0.5 mm. These variations were due to manual errors while keeping beacon on the patient. Less than 0.05 cm intra‐fraction motion was observed throughout the treatment with the help of continuous tracking.

Conclusion:

Calypso target localization system is one of the finest tools to perform radiosurgery in combination with CBCT. This non radiographic method of tracking is a real beneficial method to treat patients confidently while observing real‐time motion information of the patient.
SU‐G‐JeP1‐06: Correlation of Lung Tumor Motion with Tumor Location Using Electromagnetic Tracking
Authors: Muccigrosso D , Maughan N , Schultejans H , Bera R , Parikh P
Published: July 2016

Purpose:

It is well known that lung tumors move with respiration. However, most measurements of lung tumor motion have studied long treatment times with intermittent imaging; those populations may not necessarily represent conventional LINAC patients. We summarized the correlation between tumor motion and location in a multi‐institutional trial with electromagnetic tracking, and identified the patient cohort that would most benefit from respiratory gating.

Methods:

Continuous electromagnetic transponder data (Varian Medical, Seattle, WA) of lung tumor motion was collected from 14 patients (214 total fractions) across 3 institutions during external beam radiation therapy in a prospective clinical trial (NCT01396551). External intervention from the clinician, such as couch shifts, instructed breath‐holds, and acquisition pauses, were manually removed from the 10 Hz tracking data according to recorded notes. The average three‐dimensional displacement from the breathing cycle's end‐expiratory to end‐inhalation phases (peak‐to‐peak distance) of the transponders’ isocenter was calculated for each patient's treatment. A weighted average of each isocenter was used to assess the effects of location on motion. A total of 14 patients were included in this analysis, grouped by their transponders’ location in the lung: upper, medial, and lower.

Results:

8 patients had transponders in the upper lung, and 3 patients each in the medial lobe and lower lung. The weighted average ± standard deviation of all peak‐to‐peak distances for each group was: 1.04 ± 0.39 cm in the lower lung, 0.56 ± 0.14 cm in the medial lung, and 0.30 ± 0.06 cm in the upper lung.

Conclusion:

Tumors in the lower lung are most susceptible to excessive motion and daily variation, and would benefit most from continuous motion tracking and gating. Those in the medial lobe might be at moderate risk. The upper lobes have limited motion. These results can guide different motion management strategies between lung tumor locations.

This is part of an NIH‐funded prospective clinical trial (NCT01396551), using an electromagnetic transponder tracking system and additional funding from Varian Medical (Seattle, WA).
SU‐G‐TeP2‐09: Evaluation of the MaxFOV Extended Field of View (EFOV) Reconstruction Algorithm On a GE RT590 CT Scanner
Authors: Grzetic S , Weldon M , Noa K , Gupta N
Published: July 2016

Purpose:

This study compares the newly released MaxFOV Revision 1 EFOV reconstruction algorithm for GE RT590 to the older WideView EFOV algorithm. Two radiotherapy overlays from Q‐fix and Diacor, are included in our analysis. Hounsfield Units (HU) generated with the WideView algorithm varied in the extended field (beyond 50cm) and the scanned object's border varied from slice to slice. A validation of HU consistency between the two reconstruction algorithms is performed.

Methods:

A CatPhan 504 and CIRS062 Electron Density Phantom were scanned on a GE RT590 CT‐Simulator. The phantoms were positioned in multiple locations within the scan field of view so some of the density plugs were outside the 50cm reconstruction circle. Images were reconstructed using both the WideView and MaxFOV algorithms. The HU for each scan were characterized both in average over a volume and in profile.

Results:

HU values are consistent between the two algorithms. Low‐density material will have a slight increase in HU value and high‐density material will have a slight decrease in HU value as the distance from the sweet spot increases. Border inconsistencies and shading artifacts are still present with the MaxFOV reconstruction on the Q‐fix overlay but not the Diacor overlay (It should be noted that the Q‐fix overlay is not currently GE‐certified). HU values for water outside the 50cm FOV are within 40HU of reconstructions at the sweet spot of the scanner. CatPhan HU profiles show improvement with the MaxFOV algorithm as it approaches the scanner edge.

Conclusion:

The new MaxFOV algorithm improves the contour border for objects outside of the standard FOV when using a GE‐approved tabletop. Air cavities outside of the standard FOV create inconsistent object borders. HU consistency is within GE specifications and the accuracy of the phantom edge improves. Further adjustments to the algorithm are being investigated by GE.
SU‐G‐JeP3‐02: Comparison of Magnitude and Frequency of Patient Positioning Errors in Breast Irradiation Using AlignRT 3D Optical Surface Imaging and Skin Mark Techniques
Authors: Yao R , Chisela W , Dorbu G
Published: July 2016

Purpose:

To evaluate clinical usefulness of AlignRT (Vision RT Ltd., London, UK) in reducing patient positioning errors in breast irradiation.

Methods:

60 patients undergoing whole breast irradiation were selected for this study. Patients were treated to the left or right breast lying on Qfix Access breast board (Qfix, Avondale, PA) in supine position for 28 fractions using tangential fields. 30 patients were aligned using AlignRT by aligning a breast surface region of interest (ROI) to the same area from a reference surface image extracted from planning CT. When the patient's surface image deviated from the reference by more than 3mm on one or more translational and rotational directions, a new reference was acquired using AlignRT in‐room cameras. The other 30 patients were aligned to the skin marks with room lasers. On‐Board MV portal images of medial field were taken daily and matched to the DRRs. The magnitude and frequency of positioning errors were determined from measured translational shifts. Kolmogorov‐Smirnov test was used to evaluate statistical differences of positional accuracy and precision between AlignRT and non‐AlignRT patients.

Results:

The percentage of port images with no shift required was 46.5% and 27.0% in vertical, 49.8% and 25.8% in longitudinal, 47.6% and 28.5% in lateral for AlignRT and non‐AlignRT patients, respectively. The percentage of port images requiring more than 3mm shifts was 18.1% and 35.1% in vertical, 28.6% and 50.8% in longitudinal, 11.3% and 24.2% in lateral for AlignRT and non‐AlignRT patients, respectively. Kolmogorov‐Smirnov test showed that there were significant differences between the frequency distributions of AlignRT and non‐AlignRT in vertical, longitudinal, and lateral shifts.

Conclusion:

As confirmed by port images, AlignRT‐assisted patient positioning can significantly reduce the frequency and magnitude of patient setup errors in breast irradiation compared to the use of lasers and skin marks.
SU‐G‐JeP3‐15: Is the Reproducibility with Respect to Bone of Tumor Position at Simulation for Breath Hold CT Scans Correlated to the Reproducibility for Multiple Breath Hold CBCTs at Treatment in SBRT Thoracic Patients?
Authors: Pollard J , Prajapati S , Gao S , Nitsch P , Sadagopan R , Wang X , Balter P
Published: July 2016

Purpose:

To evaluate correlation between the reproducibility of tumor position under feedback guided voluntary deep inspiration breath hold gating at simulation and at treatment.

Methods:

All patients treated with breath hold (BH) have 3‐6 BH CTs taken at simulation (sim). In addition, if the relationship between the tumor and nearby bony anatomy on treatment BH CT(or CBCT) is found to be greater than 5 mm different at treatment than it was at sim, a repeat BH CT is taken before treatment. We retrospectively analyzed the sim CTs for 19 patients who received BH SBRT lung treatments and had repeat BH CT on treatment. We evaluated the reproducibility of the tumor position during the simulation CTs and compared this to the reproducibility of the tumor position on the repeat treatment CT with our in‐house CT alignment software (CT‐Assisted Targeting for Radiotherapy).

Results:

Comparing the tumor position for multiple simulation BH CTs, we calculated: maximum difference (max) = 0.69cm; average difference (x) = 0.28cm; standard deviation (σ) = 0.18cm. Comparing the repeat BH CBCTs on treatment days we calculated: max = 0.44cm; x = 0.16cm; σ = 0.22cm. We also found that for 95% of our BH cases, the absolute variation in tumor position within the same imaging day was within 5mm of the range at the time of simulation and treatment. We found that 75% of the BH cases had less residual tumor motion on treatment days than at simulation.

Conclusion:

This suggests that a GTV contour based upon the residual tumor motion in multiple BH datasets plus 2 mm margin should be sufficient to cover the full range of residual tumor motion on treatment days.
SU‐G‐TeP3‐14: Three‐Dimensional Cluster Model in Inhomogeneous Dose Distribution
Authors: Wei J , Penagaricano J , Narayanasamy G , Chao M
Published: July 2016

Purpose:

We aim to investigate 3D cluster formation in inhomogeneous dose distribution to search for new models predicting radiation tissue damage and further leading to new optimization paradigm for radiotherapy planning.

Methods:

The aggregation of higher dose in the organ at risk (OAR) than a preset threshold was chosen as the cluster whose connectivity dictates the cluster structure. Upon the selection of the dose threshold, the fractional density defined as the fraction of voxels in the organ eligible to be part of the cluster was determined according to the dose volume histogram (DVH). A Monte Carlo method was implemented to establish a case pertinent to the corresponding DVH. Ones and zeros were randomly assigned to each OAR voxel with the sampling probability equal to the fractional density. Ten thousand samples were randomly generated to ensure a sufficient number of cluster sets. A recursive cluster searching algorithm was developed to analyze the cluster with various connectivity choices like 1‐, 2‐, and 3‐connectivity. The mean size of the largest cluster (MSLC) from the Monte Carlo samples was taken to be a function of the fractional density. Various OARs from clinical plans were included in the study.

Results:

Intensive Monte Carlo study demonstrates the inverse relationship between the MSLC and the cluster connectivity as anticipated and the cluster size does not change with fractional density linearly regardless of the connectivity types. An initially‐slow‐increase to exponential growth transition of the MSLC from low to high density was observed. The cluster sizes were found to vary within a large range and are relatively independent of the OARs.

Conclusion:

The Monte Carlo study revealed that the cluster size could serve as a suitable index of the tissue damage (percolation cluster) and the clinical outcome of the same DVH might be potentially different.
SU‐G‐IeP4‐02: Application of Changs Attenuation Correction Technique for SPECT Partial Angle Acquisition of Jaszczak Phantom
Authors: Saha K , Barbarits J , Humenik R , Johnson J , Murray B , Hoyt S
Published: July 2016

Purpose:

Chang's mathematical formulation is a common method of attenuation correction applied on reconstructed Jaszczak phantom images. Though Chang's attenuation correction method has been used for 360° angle acquisition, its applicability for 180° angle acquisition remains a question with one vendor's camera software producing artifacts. The objective of this work is to ensure that Chang's attenuation correction technique can be applied for reconstructed Jaszczak phantom images acquired in both 360° and 180° mode.

Methods:

The Jaszczak phantom filled with 20 mCi of diluted Tc‐99m was placed on the patient table of Siemens e.cam™ (n = 2) and Siemens Symbia™ (n = 1) dual head gamma cameras centered both in lateral and axial directions. A total of 3 scans were done at 180° and 2 scans at 360° orbit acquisition modes. Thirty two million counts were acquired for both modes. Reconstruction of the projection data was performed using filtered back projection smoothed with pre reconstruction Butterworth filter (order: 6, cutoff: 0.55). Reconstructed transaxial slices were attenuation corrected by Chang's attenuation correction technique as implemented in the camera software. Corrections were also done using a modified technique where photon path lengths for all possible attenuation paths through a pixel in the image space were added to estimate the corresponding attenuation factor. The inverse of the attenuation factor was utilized to correct the attenuated pixel counts.

Results:

Comparable uniformity and noise were observed for 360° acquired phantom images attenuation corrected by the vendor technique (28.3% and 7.9%) and the proposed technique (26.8% and 8.4%). The difference in uniformity for 180° acquisition between the proposed technique (22.6% and 6.8%) and the vendor technique (57.6% and 30.1%) was more substantial.

Conclusion:

Assessment of attenuation correction performance by phantom uniformity analysis illustrated improved uniformity with the proposed algorithm compared to the camera software.
SU‐G‐IeP4‐03: Cone Beam X‐Ray Luminescence Computed Tomography Based On Generalized Gaussian Markov Random Field
Authors: Zhang G , Xing L
Published: July 2016

Purpose:

Cone beam X‐ray luminescence computed tomography (CB‐XLCT), which aims to achieve molecular and functional imaging by X‐rays, has recently been proposed as a new imaging modality. However, the inverse problem of CB‐XLCT is seriously ill‐conditioned, hindering us to achieve good image quality. In this work, a novel reconstruction method based on Bayesian theory is proposed to tackle this problem

Methods:

Bayesian theory provides a natural framework for utilizing various kinds of available prior information to improve the reconstruction image quality. A generalized Gaussian Markov random field (GGMRF) model is proposed here to construct the prior model of the Bayesian theory. The most important feature of GGMRF model is the adjustable shape parameter p, which can be continuously adjusted from 1 to 2. The reconstruction image tends to have more edge‐preserving property when p is slide to 1, while having more noise tolerance property when p is slide to 2, just like the behavior of L1 and L2 regularization methods, respectively. The proposed method provides a flexible regularization framework to adapt to a wide range of applications.

Results:

Numerical simulations were implemented to test the performance of the proposed method. The Digimouse atlas were employed to construct a three‐dimensional mouse model, and two small cylinders were placed inside to serve as the targets. Reconstruction results show that the proposed method tends to obtain better spatial resolution with a smaller shape parameter, while better signal‐to‐noise image with a larger shape parameter. Quantitative indexes, contrast‐to‐noise ratio (CNR) and full‐width at half‐maximum (FWHM), were used to assess the performance of the proposed method, and confirmed its effectiveness in CB‐XLCT reconstruction.

Conclusion:

A novel reconstruction method for CB‐XLCT is proposed based on GGMRF model, which enables an adjustable performance tradeoff between L1 and L2 regularization methods. Numerical simulations were conducted to demonstrate its performance.
SU‐G‐JeP4‐01: An Assessment of a Microsoft Kinect V2 Sensor for Voluntary Breath‐Hold Monitoring in Radiotherapy
Authors: Edmunds D , Donovan E
Published: July 2016

Purpose:

To determine whether the Microsoft Kinect Version 2 (Kinect v2), a commercial off‐the‐shelf (COTS) depth sensors designed for entertainment purposes, were robust to the radiotherapy treatment environment and could be suitable for monitoring of voluntary breath‐hold compliance. This could complement current visual monitoring techniques, and be useful for heart sparing left breast radiotherapy.

Methods:

In‐house software to control Kinect v2 sensors, and capture output information, was developed using the free Microsoft software development kit, and the Cinder creative coding C++ library. Each sensor was used with a 12m USB 3.0 active cable. A solid water block was used as the object. The depth accuracy and precision of the sensors was evaluated by comparing Kinect reported distance to the object with a precision laser measurement across a distance range of 0.6m to 2.0 m. The object was positioned on a high‐precision programmable motion platform and moved in two programmed motion patterns and Kinect reported distance logged. Robustness to the radiation environment was tested by repeating all measurements with a linear accelerator operating over a range of pulse repetition frequencies (6Hz to 400Hz) and dose rates 50 to 1500 monitor units (MU) per minute.

Results:

The complex, consistent relationship between true and measured distance was unaffected by the radiation environment, as was the ability to detect motion. Sensor precision was < 1 mm and the accuracy between 1.3 mm and 1.8 mm when a distance correction was applied. Both motion patterns were tracked successfully with a root mean squared error (RMSE) of 1.4 and 1.1 mm respectively.

Conclusion:

Kinect v2 sensors are capable of tracking pre‐programmed motion patterns with an accuracy <2 mm and appear robust to the radiotherapy treatment environment. A clinical trial using Kinect v2 sensor for monitoring voluntary breath hold has ethical approval and is open to recruitment.

The authors are supported by a National Institute of Health Research (NIHR) Career Development Fellowship (CDF‐2013‐06‐005). Microsoft Corporation donated three sensors. The views expressed in this publication are those of the author(s) and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health.
SU‐G‐JeP4‐11: Prospective Treatment Plan‐Specific Action Limits for Real‐Time Intrafractional Monitoring in Surface Image Guided Radiosurgery
Authors: Yock A , Pawlicki T , Kim G
Published: July 2016

Purpose:

Surface image‐guided radiosurgery action limits are created to determine when intrafractional patient motion warrants intervention. Action limits remain constant across patients despite plan‐specific effects on brain metastases target coverage. The purpose of this work was twofold: 1) characterize the sensitivity of single‐met per iso and multi‐met per iso treatment plans to motion, and 2) describe a method to prospectively determine plan‐specific action limits considering this sensitivity.

Methods:

Seventy‐two brain metastases were used for this study. Twenty‐five were treated individually (“single‐met per iso plans”), and 47 were treated simultaneously with at least one other met (“multi‐met per iso plans”). For each met, the proportion of the gross tumor volume that remained within the 100% prescription isodose line after various combinations of translations and rotations (0.0–3.0 mm and 0.0–3.0°) was estimated. This was achieved using code developed in the Matlab environment that exhaustively evaluated the effects of all combinations of translations and rotations in this range. The target volume and the prescription dose volume were considered concentric spheres that encompassed volumes determined from the treatment plan. Plan‐specific contour plots and DVHs were created to illustrate the sensitivity of a specific lesion to motion.

Results:

Both single‐met per iso and multi‐met per iso plans exhibited compromised target coverage after transformations, though multi‐met per iso plans were considerably more sensitive to motion (2.3% and 39.8%, respectively). Plan‐specific contour plots and DVHs illustrate how size, distance from isocenter, and planning technique affect motion sensitivity.

Conclusion:

Stereotactic radiosurgery treatment plans that treat multiple brain metastases using a common isocenter are particularly susceptible to patient motion. This technique and other plan‐specific factors should influence motion management. A graphical representation of the sensitivity of any plan to motion can be generated to determine appropriate action limit.
SU‐G‐JeP4‐15: Feasibility Study of Tumor Monitoring Technique Using Prompt Gamma Rays During Antiproton Therapy
Authors: Shin H , Yoon D , Jung J , Kim M , Suh T
Published: July 2016

Purpose:

The purpose of this study is to suggest a tumor monitoring technique using prompt gamma rays emitted during the reaction between an antiproton and a boron particle, and to verify the increase of the therapeutic effectiveness of the antiproton boron fusion therapy using Monte Carlo simulation code.

Methods:

We acquired the percentage depth dose of the antiproton beam from a water phantom with and without three boron uptake regions (region A, B, and C) using F6 tally of MCNPX. The tomographic image was reconstructed using prompt gamma ray events from the reaction between the antiproton and boron during the treatment from 32 projections (reconstruction algorithm: MLEM). For the image reconstruction, we were performed using a 80 × 80 pixel matrix with a pixel size of 5 mm. The energy window was set as a 10 % energy window.

Results:

The prompt gamma ray peak for imaging was observed at 719 keV in the energy spectrum using the F8 tally fuction (energy deposition tally) of the MCNPX code. The tomographic image shows that the boron uptake regions were successfully identified from the simulation results. In terms of the receiver operating characteristic curve analysis, the area under the curve values were 0.647 (region A), 0.679 (region B), and 0.632 (region C). The SNR values increased as the tumor diameter increased. The CNR indicated the relative signal intensity within different regions. The CNR values also increased as the different of BURs diamter increased.

Conclusion:

We confirmed the feasibility of tumor monitoring during the antiproton therapy as well as the superior therapeutic effect of the antiproton boron fusion therapy. This result can be beneficial for the development of a more accurate particle therapy.
SU‐G‐TeP4‐03: A Multileaf Collimator Calibration and Quality Assurance Technique Using An Electronic Portal Imaging Device
Authors: Lebron S , Yan G , Li J , Lu B , Liu C
Published: July 2016

Purpose:

To develop an accurate and quick multileaf collimator (MLC) calibration and quality assurance technique using an electronic portal imaging device (EPID)

Methods:

The MLC models used include the MLCi and Agility (Elekta Ltd). This technique consists of two 22(L)x10(W) cm2 fields with 00 and 1800 collimator angles centered to an offset EPID. The MLC opening is estimated by calculating the profile at the image's center in the image's horizontal direction. Scans in the image's vertical direction were calculated every 20 pixels in the inner 70% of estimated MLC opening. The profiles’ edges were fitted with linear equations to determine the image's rotation angle. Then, crossline profiles were scanned at the center of each leaf taking into account the leaf's width at isocenter and the rotation angle. The profiles’ edges determine the location of the leaves’ edges and these were subtracted from the reference leaf's position in order to determine the relative leaf offsets. The edge location of all profiles was determined by using the parameterized gradient of the penumbra region. The technique was tested against an established diode array‐based method, and for different MLC systems, patterns, gantry angles, days, energies, beam modalities and MLC openings.

Results:

The differences between the proposed and established methods were 0.26±0.19mm. The leaf offsets’ deviation was <0.3mm (5 months period). For pattern fields, the differences between predetermined and calculated offsets were 0.18±0.18mm. The leaf offset deviation of measurements with different energies and MLC openings were <0.1mm and <0.3mm, respectively. The differences between offsets of FF and FFF beams were 0.01±0.02mm (<0.07mm). The differences between the offsets at different gantry angles were 0.08±0.15mm.

Conclusion:

The proposed method proved to be accurate and efficient in calculating the relative leaf offsets. Parameterized field edge is essential to obtain accurate result by eliminating the noise from EPID.