bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐G‐BRA‐03: PCA Based Imaging Angle Optimization for 2D Cine MRI Based Radiotherapy Guidance
Authors: Chen T , Yue N , Jabbour S , Zhang M
Published: July 2016

Purpose:

To develop an imaging angle optimization methodology for orthogonal 2D cine MRI based radiotherapy guidance using Principal Component Analysis (PCA) of target motion retrieved from 4DCT.

Methods:

We retrospectively analyzed 4DCT of 6 patients with lung tumor. A radiation oncologist manually contoured the target volume at the maximal inhalation phase of the respiratory cycle. An object constrained deformable image registration (DIR) method has been developed to track the target motion along the respiration at ten phases. The motion of the center of the target mass has been analyzed using the PCA to find out the principal motion components that were uncorrelated with each other. Two orthogonal image planes for cineMRI have been determined using this method to minimize the through plane motion during MRI based radiotherapy guidance.

Results:

3D target respiratory motion for all 6 patients has been efficiently retrieved from 4DCT. In this process, the object constrained DIR demonstrated satisfactory accuracy and efficiency to enable the automatic motion tracking for clinical application. The average motion amplitude in the AP, lateral, and longitudinal directions were 3.6mm (min: 1.6mm, max: 5.6mm), 1.7mm (min: 0.6mm, max: 2.7mm), and 5.6mm (min: 1.8mm, max: 16.1mm), respectively. Based on PCA, the optimal orthogonal imaging planes were determined for cineMRI. The average angular difference between the PCA determined imaging planes and the traditional AP and lateral imaging planes were 47 and 31 degrees, respectively. After optimization, the average amplitude of through plane motion reduced from 3.6mm in AP images to 2.5mm (min:1.3mm, max:3.9mm); and from 1.7mm in lateral images to 0.6mm (min: 0.2mm, max:1.5mm), while the principal in plane motion amplitude increased from 5.6mm to 6.5mm (min: 2.8mm, max: 17mm).

Conclusion:

DIR and PCA can be used to optimize the orthogonal image planes of cineMRI to minimize the through plane motion during radiotherapy guidance.
SU‐G‐BRA‐09: Estimation of Motion Tracking Uncertainty for Real‐Time Adaptive Imaging
Authors: Yan H , Chen Z , Nath R , Liu W
Published: July 2016

Purpose:

kV fluoroscopic imaging combined with MV treatment beam imaging has been investigated for intrafractional motion monitoring and correction. It is, however, subject to additional kV imaging dose to normal tissue. To balance tracking accuracy and imaging dose, we previously proposed an adaptive imaging strategy to dynamically decide future imaging type and moments based on motion tracking uncertainty. kV imaging may be used continuously for maximal accuracy or only when the position uncertainty (probability of out of threshold) is high if a preset imaging dose limit is considered. In this work, we propose more accurate methods to estimate tracking uncertainty through analyzing acquired data in real‐time.

Methods:

We simulated motion tracking process based on a previously developed imaging framework (MV + initial seconds of kV imaging) using real‐time breathing data from 42 patients. Motion tracking errors for each time point were collected together with the time point's corresponding features, such as tumor motion speed and 2D tracking error of previous time points, etc. We tested three methods for error uncertainty estimation based on the features: conditional probability distribution, logistic regression modeling, and support vector machine (SVM) classification to detect errors exceeding a threshold.

Results:

For conditional probability distribution, polynomial regressions on three features (previous tracking error, prediction quality, and cosine of the angle between the trajectory and the treatment beam) showed strong correlation with the variation (uncertainty) of the mean 3D tracking error and its standard deviation: R‐square = 0.94 and 0.90, respectively. The logistic regression and SVM classification successfully identified about 95% of tracking errors exceeding 2.5mm threshold.

Conclusion:

The proposed methods can reliably estimate the motion tracking uncertainty in real‐time, which can be used to guide adaptive additional imaging to confirm the tumor is within the margin or initialize motion compensation if it is out of the margin.
SU‐G‐BRA‐12: Development of An Intra‐Fractional Motion Tracking and Dose Reconstruction System for Adaptive Stereotactic Body Radiation Therapy in High‐Risk Prostate Cancer
Authors: Rezaeian N Hassan , Chi Y , Tian Z , Jiang S , Hannan R , Jia X
Published: July 2016

Purpose:

A clinical trial on stereotactic body radiation therapy (SBRT) for high‐risk prostate cancer is undergoing at our institution. In addition to escalating dose to the prostate, we have increased dose to intra‐prostatic lesions. Intra‐fractional prostate motion deteriorates well planned radiation dose, especially for the small intra‐prostatic lesions. To solve this problem, we have developed a motion tracking and 4D dose‐reconstruction system to facilitate adaptive re‐planning.

Methods:

Patients in the clinical trial were treated with VMAT using four arcs and 10 FFF beam. KV triggered x‐ray projections were taken every 3 sec during delivery to acquire 2D projections of 3D anatomy at the direction orthogonal to the therapeutic beam. Each patient had three implanted prostate markers. Our developed system first determined 2D projection locations of these markers and then 3D prostate translation and rotation via 2D/3D registration of the markers. Using delivery log files, our GPU‐based Monte Carlo tool (goMC) reconstructed dose corresponding to each triggered image. The calculated 4D dose distributions were further aggregated to yield the delivered dose.

Results:

We first tested each module in our system. MC dose engine were commissioned to our treatment planning system with dose difference of <0.5%. For motion tracking, 1789 kV projections from 7 patients were acquired. The 2D marker location error was <1 mm. For 3D motion tracking, root mean square (RMS) errors along LR, AP, and CC directions were 0.26mm, 0.36mm, and 0.01mm respectively in simulation studies and 1.99mm, 1.37mm, and 0.22mm in phantom studies. We also tested the entire system workflow. Our system was able to reconstruct delivered dose.

Conclusion:

We have developed a functional intra‐fractional motion tracking and 4D dose re‐construction system to support our clinical trial on adaptive high‐risk prostate cancer SBRT. Comprehensive evaluations have shown the capability and accuracy of our system.
SU‐G‐206‐02: Impact of Focal Spot Sizes On CT Image Quality
Authors: Bache S , Rong J
Published: July 2016

Purpose:

To quantify a radiology team's assessment of image quality differences between two CT scanner models currently in clinical use, with emphasis on spatial resolution that could be impacted by focal spot size.

Methods:

Modulation Transfer Functions (MTF) measurements were performed by scanning the impulse source insert module of the Catphan 600 at 120/140 kVp with both large (LFS) and small (SFS) focal spots and reconstructed to 2.5mm and 5.0mm thicknesses on a GE Discovery CT750 HD and a LightSpeed VCT CT scanner. MTFs were calculated by summing the 2D PSF along one‐dimension to obtain line‐spread‐function (LSF), and calculating the Fourier Transform of the zero‐padded and background corrected LSF. Spatial resolution performance was evaluated by comparing MTF curves, 50% and 10% MTF cutoff, and total area under the MTF curve (AUC). In addition, images of the Catphan high‐contrast module and a Kagaku anthropomorphic body phantom were acquired from the HD scanner for visual comparisons.

Results:

For each scanner model, SFS was superior to LFS spatial resolution with respect to 50%/10% MTF cutoff and AUC. For the HD, 50%/10% cutoff was 4.29/7.22cm‐1 for the LFS and 4.43/7.45cm‐1 for the SFS. VCT outperformed HD, with 50%/10% cutoff of 4.40/7.29 cm‐1 for LFS and 4.62/7.47cm‐1 for SFS. Scanner model performance in order of decreasing AUC performance was VCT SFS (7.43), HD SFS (7.20), VCT LFS (7.09) and HD LFS (6.93). Visual evaluations of Kagaku phantom images confirmed that VCT outperformed HD.

Conclusion:

VCT outperformed HD and small focal spot is desired for either model over large focal spot in term of spatial resolution – in agreement with radiologist feedback of overall image quality. In‐depth evaluations of clinical impact and focal spot selection mechanisms is currently being assessed.
SU‐G‐206‐09: Consistent Low Contrast Detectability and Optimal Dose for Different Patient Sizes in Abdominal CT
Authors: Zhou Y , Nute J , Scott A , Lee C
Published: July 2016

Purpose:

To study optimal dose dictated by consistent low contrast detectability for various patient sizes in abdominal CT.

Methods:

Seven realistically shaped tissue‐equivalent abdomen phantoms (CIRS TE01–TE08) were utilized. Helical scans were performed on each phantom with GE 750 HD and Siemens mCT 64 at different dose levels. The images were reconstructed using comparable kernels (standard and Bf35 for GE and Siemens, respectively). The noise images, obtained using subtraction from adjacent slices, were partitioned into matrices of square cells matching different sizes of lesions (1.8 – 10 mm). The noise granularities were quantified by the standard deviation (σ) of the matrix cell pixel mean values distribution at each cell size. The minimum detectable contrast (MDC), defined as 3.29σ with 95% confidence of detectability, was obtained for each phantom at different doses. We proposed that the MDC is inversely proportional to the lesion size and to the square root of the size specific dose and the proportional factor is a function of phantom size. The MDC data was fitted against the lesion size and dose following the proposed model.

Results:

The simplified power law model was found to fit the minimum detectable contrast against the lesion and dose very well for various phantoms (R^2 > 0.983). The proportionality factor was found to fit the phantom equivalent diameter (L) to a Gaussian amplifier with R2 = 0.983 and to an exponential function with R^2 = 0.999, for GE HD750 and Siemens mCT 64, respectively. The parameters of the Gaussian amplifier varied with different scanners. To obtain the tube current‐rotation time product (mAs) from the size specific dose (D), the relationship of D per 100 mAs versus L at 120 kVp was also presented for each scanner.

Conclusion:

The relationship of low contrast detectability and optimal dose across different patient sizes was successfully obtained.
SU‐G‐206‐10: Low‐Contrast Detectability Vs. Dose for CT Images Reconstructed Using Filtered Backprojection and Iterative Reconstruction: Assessment with a Model Observer
Authors: Favazza C , Ferrero A , McMillan K , Bruesewitz M , Yu L , Leng S , Kofler J , McCollough C
Published: July 2016

Purpose:

To evaluate CT low‐contrast detectability at different dose levels in images reconstructed using filtered backprojection (FBP) and iterative reconstruction (IR).

Methods:

A validated channelized Hotelling observer (CHO) model was used to detect low contrast objects in images of a helical CT phantom (Model 061, CIRS) using an Aquilion Prime 160 scanner (Toshiba Medical Systems). Twenty‐one different objects of 7 diameters (2.4, 3.2, 4.6, 6.3, 9.5, and 10 mm) and 3 contrast levels (∼10, 15, and 25 HU) were evaluated. Images were acquired using 5 different tube current settings (45, 60, 90, 140, and 180 mA) and reconstructed using both FBP and IR (Adaptive Iterative Dose Reduction (AIDR) 3D). For each tube current, the phantom was scanned 100 times, yielding sets of 100 object‐present and object‐absent images at the same x‐y locations. All images were evaluated using the CHO and detectability indices (d’) for each object were calculated at all dose levels.

Results:

For the same tube current setting, images formed using IR yielded d’ values on average 8% higher than images reconstructed using FBP. When dose was reduced by more than 25% of the full dose, however, results showed reduced low‐contrast detectability in AIDR‐3D images compared to 100% dose, FBP images. With the vendordefault settings, dose is automatically reduced by 70‐75% when AIDR 3D reconstructions are selected, which our data indicate would significantly reduce low contrast detectability.

Conclusion:

At higher dose levels (minimal dose reduction), AIDR‐3D improved object detectability as compared to full‐dose FBP images. However, when dose was reduced by more than 25%, object detectability was substantially reduced for images reconstructed with AIDR‐3D compared to full‐dose FBP images.

CH McCollough is supported by industry funding from Siemens Healthcare
SU‐G‐206‐12: The Correlation Between Table Height and Patient Size in CT: A Simple Way to Properly Position Patients
Authors: Szczykutowicz T , Janssen‐Saldivar E , Miller D , Malkus A
Published: July 2016

Purpose:

Proper patient positioning is essential in CT to ensure automatic exposure control functions properly, noise uniformity, and CT number uniformity. This work describes how table height can be used as a surrogate for proper patient positioning and motivates incorporating table height recommendations as a function of patient size into technologist training programs.

Methods:

Scan data were acquired from 551 adult and pediatric patients under IRB approval. The table height, mean anterior‐posterior patient dimension, and mean lateral patient dimension were calculated for each patient. Table height as a function of a patient size surrogate was then analyzed. The mathematical relationship between table height and a properly positioned cylinder was derived and used to fit the data. Patient scans showing proper positioning, and positioning both too high and too low in the gantry were analyzed by measuring the image noise within anterior and posterior regions of the liver.

Results:

The slope of our fits to patient data matched the mathematical model well, suggesting our technologists are on average properly positioning patients at isocenter. The predicted slope for table height versus anterior‐posterior width is 0.5; we measured 0.48±0.006. Patients with table heights more than 2 sigma from the mean table height for their size were shown to have noise non‐uniformities greater than 13 HU across the liver which demonstrates how knowing the patient size and table height can predict the image quality of the subsequent CT exam.

Conclusion:

Our results motivate training technologists to pay attention to the table height. Doing so could easily stop an adult receiving a pediatric positioning and vice versa. Additionally, our results can guide the construction of low end CT scanners lacking vertical table motion by defining the range of table heights used at our clinical practice for a particular patient age and size.

Research support provided by GE Healthcare. TPS supplies CT protocols to GE Healthcare under a licensing agreement.
SU‐G‐IeP1‐12: Size Selective Arterial Cerebral Blood Volume Mapping Using Multiple Inversion Time Arterial Spin Labeling
Authors: Jung Y , Johnston M , Liu H , Whitlow C
Published: July 2016

Purpose:

To demonstrate the feasibility of a novel method for size specific arterial cerebral blood volume (aCBV) mapping using pseudo‐continuous arterial spin labeling (PCASL), with multiple TI.

Methods:

Multiple PCASL images were obtained from a subject with TI of [300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000] ms. Each TI pair was averaged six times. Two scans were performed: one without a flow crusher gradient and the other with a crusher gradient (10cm/s in three directions) to remove signals from large arteries. Scan times were 5min. without a crusher gradient and 5.5 min with a crusher gradient. Non‐linear fitting algorithm finds the minimum mean squared solution of per‐voxel based aCBV, cerebral blood flow, and arterial transit time, and fits the data into a hemodynamic model that represents superposition of blood volume and flow components within a single voxel.

Results:

aCBV maps with a crusher gradient represent signals from medium and small sized arteries, while those without a crusher gradient represent signals from all sized arteries, indicating that flow crusher gradients can be effectively employed to achieve size‐specific aCBV mapping. Regardless of flow crusher, the CBF and ATT maps are very similar in appearance.

Conclusion:

Quantitative size selective blood volume mapping controlled by a flow crusher is feasible without additional information because the ASL quantification process doesn't require an arterial input function measured from a large artery. The size specific blood volume mapping is not interfered by sSignals from large arteries do not interfere with size specific aCBV mapping in the applications of interest in for applications in which only medium or small arteries are of interest.
SU‐G‐IeP1‐14: The Relationship Between Voxel Based Morphometry and Fiber Tract Abnormalities by Correlation Analysis in Patients with Neurodegerative Disease
Authors: Juh R , Suh T , Han J , Kim C , Oh C
Published: July 2016

Purpose:

We evaluated the relationship between white matter (WM) tract disintegration and gray matter (GM) atrophy in patients with Alzheimer's disease (AD), mild cognitive impairment (MCI) and controls, using diffusion tensor imaging (DTI) and an optimized voxel‐based analysis.

Methods:

Two hundred thirty one individuals (61 controls, 116 MCI and 54 AD) were included. Voxel‐based WM tract statistics was used to obtain whole‐brain maps of WM bundles for FA. Voxel‐based morphometry (VBM) was conducted to detect regions of gray matter (GM) atrophy in the AD, MCI group relative to the control group. FA maps were processed to make voxel‐wise comparison of tract based analysis in whole brain between each the two groups. The relationship between locations of abnormalities in the WM and GM were examined.

Results:

Patients with AD showed significant GM atrophy in posterior cingulate gyrus (BA31, 32) to the precuneus, the middle temporal lobe (BA19), the superior frontal (BA9) to the anterior cingulate (BA 32), the medial frontal lobe (BA 11, BA25), the hippocampus, the parahippocampal gyrus (BA30/34) and the insula, and WM tract disintegrity of the uncinate fasciculus, posterior cingulate fasciculus and fornix compared with the control and MCI groups. These abnormalities in the AD group were caused by either structural changes in GM atrophy or neural dysfunction due to functional disconnections in the WM tract.

Conclusion:

The GM atrophy resulting from WM tract disintegration or GM atrophy itself may be the first step in the AD process, resulting in anatomically congruent correlations between WM disintegration and regional GM atrophy. Using tract based spatial statistics and voxel based analysis, both of which are useful in investigating GM and WM changes in individuals with neurodegenerative disorders.
SU‐G‐JeP1‐02: A New Intra‐Fractional Prostate Motion Tracking Method in Volumetric Modulated Arc Therapy (VMAT) Via 2D/3D Registration
Authors: Chi Y , Rezaeian N Hassan , Hannan R , Jia X
Published: July 2016

Purpose:

Intra‐fractional prostate motion leads uncertainty on delivered dose in radiotherapy and may cause significant dose deviation from the planned dose distribution. This is especially a concern in scenarios with a high dose per fraction and hence a long delivery time, e.g. stereotactic body radiotherapy. Knowledge about intra‐fractional prostate motion is valuable to address this problem, e.g. by reconstructing delivered dose and performing adaptation. This study proposes a new approach to determine intra‐fractional prostate motion in VMAT via 2D/3D maker registration.

Methods:

At our institution, each patient has three markers implanted in the prostate. During treatment delivery, kV triggered images were taken every three seconds to acquire 2D projection of 3D anatomy at the direction orthogonal to the therapeutic beam. Projected marker locations were identified on each projection image using template matching with geometric constraints. 3D prostate translation and rotation for each triggered image were obtained by solving an optimization problem, such that the calculated marker locations match the measured ones. Inter‐image motion smoothness was employed as a constraint. We tested this method in simulation studies with five realistic prostate motion trajectories acquired via Calypso and in real phantom experiments.

Results:

For the simulation case, the motion range for these patients was 0.5∼6.0 mm. Root mean square (RMS) error of calculated motion along left‐right (LR), anterior‐posterior (AP) and cranial‐caudal (CC) directions were 0.26mm, 0.36mm, and 0.016mm, respectively. The motion range in the phantom study along LR, AP, and CC directions were 15mm, 20mm and 10mm. The mean RMS errors along these directions were 1.99mm, 1.37mm and 0.22mm.

Conclusion:

A new prostate motion tracking algorithm based on kV triggered images has been developed and validated. Clinically acceptable accuracy has been achieved.
SU‐G‐JeP1‐07: Development of a Programmable Motion Testbed for the Validation of Ultrasound Tracking Algorithms
Authors: Shepard A , Matrosic C , Zagzebski J , Bednarz B
Published: July 2016

Purpose:

To develop an advanced testbed that combines a 3D motion stage and ultrasound phantom to optimize and validate 2D and 3D tracking algorithms for real‐time motion management during radiation therapy.

Methods:

A Siemens S2000 Ultrasound scanner utilizing a 9L4 transducer was coupled with the Washington University 4D Phantom to simulate patient motion. The transducer was securely fastened to the 3D stage and positioned to image three cylinders of varying contrast in a Gammex 404GS LE phantom. The transducer was placed within a water bath above the phantom in order to maintain sufficient coupling for the entire range of simulated motion. A programmed motion sequence was used to move the transducer during image acquisition and a cine video was acquired for one minute to allow for long sequence tracking. Images were analyzed using a normalized cross‐correlation block matching tracking algorithm and compared to the known motion of the transducer relative to the phantom.

Results:

The setup produced stable ultrasound motion traces consistent with those programmed into the 3D motion stage. The acquired ultrasound images showed minimal artifacts and an image quality that was more than suitable for tracking algorithm verification. Comparisons of a block matching tracking algorithm with the known motion trace for the three features resulted in an average tracking error of 0.59 mm.

Conclusion:

The high accuracy and programmability of the 4D phantom allows for the acquisition of ultrasound motion sequences that are highly customizable; allowing for focused analysis of some common pitfalls of tracking algorithms such as partial feature occlusion or feature disappearance, among others. The design can easily be modified to adapt to any probe such that the process can be extended to 3D acquisition. Further development of an anatomy specific phantom better resembling true anatomical landmarks could lead to an even more robust validation.

This work is partially funded by NIH grant R01CA190298
SU‐G‐JeP1‐08: Dual Modality Verification for Respiratory Gating Using New Real‐ Time Tumor Tracking Radiotherapy System
Authors: Shiinoki T , Kawamura S , Koike M , Yuasa Y , Uehara T , Fujimoto K , Hanazawa H , Shibuya K
Published: July 2016

Purpose:

The respirato ry gating system combined the TrueBeam and a new real‐time tumor‐tracking radiotherapy system (RTRT) was installed. The RTRT system consists of two x‐ray tubes and color image intensifiers. Using fluoroscopic images, the fiducial marker which was implanted near the tumor was tracked and was used as the internal surrogate for respiratory gating. The purposes of this study was to develop the verification technique of the respiratory gating with the new RTRT using cine electronic portal image device images (EPIDs) of TrueBeam and log files of the RTRT. Methods: A patient who underwent respiratory gated SBRT of the lung using the RTRT were enrolled in this study. For a patient, the log files of three‐dimensional coordinate of fiducial marker used as an internal surrogate were acquired using the RTRT. Simultaneously, the cine EPIDs were acquired during respiratory gated radiotherapy. The data acquisition was performed for one field at five sessions during the course of SBRT. The residual motion errors were calculated using the log files (Elog). The fiducial marker used as an internal surrogate into the cine EPIDs was automatically extracted by in‐house software based on the template‐matching algorithm. The differences between the the marker positions of cine EPIDs and digitally reconstructed radiograph were calculated (EEPID).

Results:

Marker detection on EPID using in‐house software was influenced by low image contrast. For one field during the course of SBRT, the respiratory gating using the RTRT showed the mean ± S.D. of 95th percentile EEPID were 1.3 ± 0.3 mm,1.1 ± 0.5 mm,and those of Elog were 1.5 ± 0.2 mm, 1.1 ± 0.2 mm in LR and SI directions, respectively.

Conclusion:

We have developed the verification method of respiratory gating combined TrueBeam and new real‐time tumor‐tracking radiotherapy system using EPIDs and log files.
SU‐G‐TeP2‐15: Feasibility Study of Fiber‐Optic Cerenkov Radiation Sensors for in Vivo Measurement: Dosimetric Characterization and Clinical Application in Proton Beams
Authors: Lah J , Son J , Kim G , Shin D
Published: July 2016

Purpose:

To evaluate the possibility of a fiber‐optic Cerenkov radiation sensor (FCRS) for in vivo dose verification in proton therapy.

Methods:

The Cerenkov radiation due to the proton beam was measured using a homemade phantom, consisting of a plastic optical fiber (POF, PGSCD1001‐13‐E, Toray, Tokyo, Japan) connected to each channel of a multianode photomultiplier tube (MAPMT:H7546, Hamamatsu Photonics, Shizuoka, Japan). Data were acquired using a multi‐anode photomultiplier tube with the NI‐DAQ system (National Instruments Texas, USA). The real‐time monitoring graphic user interface was programmed using Labview. The FCRS was analyzed for its dosimetrics characteristic in proton beam. To determine the accuracy of the FCRS in proton dose measurements, we compared the ionization chamber dose measurements using a water phantom. We investigated the feasibility of the FCRS for the measurement of dose distributions near the superficial region for proton plans with a varying separation between the target volume and the surface of 3 patients using a humanoid phantom.

Results:

The dose‐response has good linearity. Dose‐rate and energy dependence were found to be within 1%. Depth‐dose distributions in non‐modulated proton beams obtained with the FCRS was in good agreement with the depth‐dose measurements from the ionization chamber. To evaluate the dosimetric accuracy of the FCRS, the difference of isocenter dose between the delivery dose calculated by the treatment planning system and that measured by the FCRS was within 3%. With in vivo dosimetry using the humanoid phantom, the calculated surface doses overestimated measurements by 4%–8% using FCRS.

Conclusion:

In previous study, our results indicate that the performance of the array‐type FCRS was comparable to that of the currently used a multi‐layer ion chamber system. In this study, we also believe that the fiber‐optic Cerenkov radiation sensor has considerable potential for use with in vivo patient proton dosimetry.
SU‐G‐IeP3‐03: Dual‐Filament, Multi‐Facet Anode Design to Overcome Small Focal Spot Output Limitations
Authors: Freund E , Rudin S , Bednarek D
Published: July 2016

Purpose:

Demonstrate the advantages of two novel x‐ray tube‐insert designs to overcome tube output limitations for high‐resolution, small field‐of‐view (FOV) angiographic imaging.

Methods:

High‐spatial resolution with a small focal spot (sfs) is achievable with the microangiographic (MA) detector that we have developed. The two designs explored are a non‐offset design, and an offset design. Both tube‐insert designs include two filaments, L1 and L2, and two focal target tracks. L1 corresponds to an 8° anode region to produce a medium effective focal spot (mfs) to be used with the standard FOV flat‐panel detector (FPD). L2 corresponds to a 2° anode region to produce a small effective focal spot (sfs) to be used with the smaller FOV MA detector, while providing comparable x‐ray output. The non‐offset design has the sfs region closer to the anode rotation axis, and mfs region farther from the axis. The offset design has the mfs region closer to the rotation axis, and sfs region farther from the rotation axis. The sfs region of the offset design has a greater anode track diameter which may further increase output capability. However, in order to avoid limitations on the mfs FOV in this design, the sfs target region of the anode is offset in the anode cathode direction. The geometries of both designs are illustrated and compared.

Results:

It is shown that the new designs enable increased tube output for the sfs when used with a small FOV detector, while also allowing for increased FOV with the standard FPD and the mfs.

Conclusion:

A dual track, dual filament x‐ray tube‐insert design provides increased output capability over a small FOV, while enabling an mfs to be used with the lower resolution standard FPD.

Toshiba Medical Systems Corp
SU‐G‐IeP3‐05: Effects of Image Receptor Technology and Dose Reduction Software On Radiation Dose Estimates for Fluoroscopically‐Guided Interventional (FGI) Procedures
Authors: Merritt Z , Dave J , Eschelman D , Gonsalves C
Published: July 2016

Purpose:

To investigate the effects of image receptor technology and dose reduction software on radiation dose estimates for most frequently performed fluoroscopically‐guided interventional (FGI) procedures at a tertiary health care center.

Methods:

IRB approval was obtained for retrospective analysis of FGI procedures performed in the interventional radiology suites between January‐2011 and December‐2015. This included procedures performed using image‐intensifier (II) based systems which were subsequently replaced, flat‐panel‐detector (FPD) based systems which were later upgraded with ClarityIQ dose reduction software (Philips Healthcare) and relatively new FPD system already equipped with ClarityIQ. Post procedure, technologists entered system‐reported cumulative air kerma (CAK) and kerma‐area product (KAP; only KAP for II based systems) in RIS; these values were analyzed. Data pre‐processing included correcting typographical errors and cross‐verifying CAK and KAP. The most frequent high and low dose FGI procedures were identified and corresponding CAK and KAP values were compared.

Results:

Out of 27,251 procedures within this time period, most frequent high and low dose procedures were chemo/immuno‐embolization (n=1967) and abscess drainage (n=1821). Mean KAP for embolization and abscess drainage procedures were 260,657, 310,304 and 94,908 mGycm2, and 14,497, 15,040 and 6307 mGycm2 using II‐, FPD‐ and FPD with ClarityIQ‐ based systems, respectively. Statistically significant differences were observed in KAP values for embolization procedures with respect to different systems but for abscess drainage procedures significant differences were only noted between systems with FPD and FPD with ClarityIQ (p<0.05). Mean CAK reduced significantly from 823 to 308 mGy and from 43 to 21 mGy for embolization and abscess drainage procedures, respectively, in transitioning to FPD systems with ClarityIQ (p<0.05).

Conclusion:

While transitioning from II‐ to FPD‐ based systems was not associated with dose reduction for the most frequently performed FGI procedures, substantial dose reduction was noted with relatively newer systems and dose reduction software.
SU‐G‐IeP3‐15: Cloud Based Monitoring of X‐Ray Angiography Equipment Performance Based On Automated Daily Sampling of Key Performance Indicators
Authors: Sjoeberg J , Omar A , Bujila R , Nowik P , Olafsson I , Poludniowski G
Published: July 2016

Purpose:

To investigate the feasibility of deploying a novel method for the daily monitoring of x‐ray Angiography (XA) equipment performance as a cloud‐based service.

Methods:

From previous work, we have developed a novel image based method of testing the performance of XA equipment on a daily basis. A pre‐programmed protocol on an XA system is used and images are automatically analyzed using software developed in‐house, resulting in a set of Key Performance Indicators (KPI's) that can be tracked over time. The analysis software was deployed in the cloud and a routing rule was set up to automatically transfer images from the XA systems to the cloud. A web based user interface was developed with access to the KPI's for studying auto generated reports, trends and anomalies. Technologists were instructed on how to perform the daily scans with a remotely hosted instructional video and have actively participated in this endeavor for the last 7 months.

Results:

Quantitative performance tests have been automated including data aggregation, management, analysis and visualization which enables sampling of KPI's on a daily basis and the developed solution has been migrated to the cloud. The daily performance check routine takes ∼6 minutes per XA system in total including the transfer of images, analysis and reporting. In one instance a significant artifact and a defective pixel has been identified. A generally stable system performance has otherwise been observed as indicated by the process control charts.

Conclusion:

A cloud based solution for monitoring the performance of XA equipment has been developed. The solution facilitates efficient data collection, enabling useful trend analysis on large data sets.

This project was funded by Vinnova (Swedish Innovation Agency), grant number 2012‐03693, and was carried out in collaboration with Image Owl, Inc. (Reykjavik, Iceland).
SU‐G‐JeP3‐06: Lower KV Image Dose Are Expected From a Limited‐Angle Intra‐Fractional Verification (LIVE) System for SBRT Treatments
Authors: Ding G , Yin F , Ren L
Published: July 2016

Purpose:

In order to track the tumor movement for patient positioning verification during arc treatment delivery or in between 3D/IMRT beams for stereotactic body radiation therapy (SBRT), the limited‐angle kV projections acquisition simultaneously during arc treatment delivery or in‐between static treatment beams as the gantry moves to the next beam angle was proposed. The purpose of this study is to estimate additional imaging dose resulting from multiple tomosynthesis acquisitions in‐between static treatment beams and to compare with that of a conventional kV‐CBCT acquisition.

Methods:

kV imaging system integrated into Varian TrueBeam accelerators was modeled using EGSnrc Monte Carlo user code, BEAMnrc and DOSXYZnrc code was used in dose calculations. The simulated realistic kV beams from the Varian TrueBeam OBI 1.5 system were used to calculate dose to patient based on CT images. Organ doses were analyzed using DVHs. The imaging dose to patient resulting from realistic multiple tomosynthesis acquisitions with each 25–30 degree kV source rotation between 6 treatment beam gantry angles was studied.

Results:

For a typical lung SBRT treatment delivery much lower (20–50%) kV imaging doses from the sum of realistic six tomosynthesis acquisitions with each 25–30 degree x‐ray source rotation between six treatment beam gantry angles were observed compared to that from a single CBCT image acquisition.

Conclusion:

This work indicates that the kV imaging in this proposed Limited‐angle Intra‐fractional Verification (LIVE) System for SBRT Treatments has a negligible imaging dose increase. It is worth to note that the MV imaging dose caused by MV projection acquisition in‐between static beams in LIVE can be minimized by restricting the imaging to the target region and reducing the number of projections acquired. For arc treatments, MV imaging acquisition in LIVE does not add additional imaging dose as the MV images are acquired from treatment beams directly during the treatment.
SU‐G‐JeP3‐07: Real‐Time Image Guided Radiation Therapy for Heterotopic Ossification in Patients After Hip Replacement
Authors: Le A , Jiang S , Timmerman R , Choy H , Pompos A
Published: July 2016

Purpose:

To demonstrate the feasibility of using CBCT in a real‐time image guided radiation therapy (IGRT) for single fraction heterotopic ossification (HO) in patients after hip replacement. In this real‐time procedure, all steps, from simulation, imaging, planning to treatment delivery, are performed at the treatment unit in one appointment time slot. This work promotes real‐time treatment to create a paradigm shift in the single fraction radiation therapy.

Methods:

An integrated real‐time IGRT for HO was developed and tested for radiation treatment of heterotopic ossification for patient after hip replacement. After CBCT images are acquired at the linac, and sent to the treatment planning system, the physician determines the field and/or draws a block. Subsequently, a simple 2D AP/PA plan with prescription of 700 cGy is created on‐the‐fly for physician to review. Once the physician approves the plan, the patient is treated on the same simulation position. This real‐time treatment requires the team of attending physician, physicist, therapists, and dosimetrist to work in harmony to achieve all the steps in a timely manner.

Results:

Ten patients have been treated with this real‐time treatment, having the same beams arrangement treatment plan and prescription as our clinically regular CT‐based 2D plans. The average time for these procedures are 52.9 ±10.7 minutes from the time patient entered the treatment room until s/he exited, and 37.7 ±8.6 minutes from starting CBCT until last beam delivered.

Conclusion:

The real‐time IGRT for HO treatment has been tested and implemented to be a clinically accepted procedure. This one‐time appointment greatly enhances the waiting time, especially when patients in high level of pain, and provides a convenient approach for the whole clinical staff. Other disease sites will be also tested with this new technology.
SU‐G‐JeP3‐11: Use of an Easily‐Modified Simple Phantom to Perform the Daily and Monthly Localization QA Tasks for a Video‐Based Surface Imaging System
Authors: Kim C , Furhang E , Devick C
Published: July 2016

Purpose:

To describe a simple, easily fabricated, Styrofoam phantom used in conjunction with a commonly available OBI phantom, to QA a video‐surface imaging system according to TG147, using minimal effort.

Methods:

Styrofoam, a common packaging material, reflects the speckled AlignRT light very well. A Styrofoam block was used as a partial cap to attach onto a standard Varian Marker Match phantom. The cap was engraved with two sets crosshairs on each surface, one at the ‘zero’(center) and the other an ‘off‐centered’ position, 2 cm in all three orthogonal directions. A reference image is obtained at ‘zero’ position. For the daily test, static localization check is performed by aligning the phantom with room lasers at ‘off‐centered’ position and then the couch is shifted to match the ‘zero’ with the lasers. For the monthly test, plate calibration is recommended to define a relationship between an image point on the camera and that of the isocenter in the treatment room. Static localization accuracy is checked using a hidden‐target test, which is an extension of daily static localization procedure. The phantom positioned at ‘off‐centered’ is shifted to make the readings 0.0 cm for all orientations. The location of the hidden target is then verified by taking orthogonal kV images or CBCT.

Results:

The AlignRT tests required by TG147 are quite similar to those performed on on‐board imaging (OBI). Overall alignment of the system is maintained with RMS < 1 mm and any potential problems were identified. The system's static location is maintained within ± 1 mm. The same accuracy can be obtained for a monthly hidden target test which is integrated with an OBI QA.

Conclusion:

A customized phantom is tested and a routine QA program for surface‐imaging system is introduced. By dealing with a single phantom, the procedure can achieve similar goals efficiently.
SU‐G‐TeP3‐10: Radiation Induces Prompt Live‐Cell Metabolic Fluxes
Authors: Campos D , Peeters W , Nickel K , Burkel B , Bussink J , Kimple R , van der Kogel A , Eliceiri K , Kissick M
Published: July 2016

Purpose:

To compare metabolic dynamics and HIF‐1α expression following radiation between a cancerous cell line (UM‐SCC‐22B) and a normal, immortalized cell line, NOK (Normal Oral Keratinocyte). HIF‐1 is a key factor in metabolism and radiosensitivity. A better understanding of how radiation affects the interplay of metabolism and HIF‐1 might give a better understanding of the mechanisms responsible for radiosensitivity.

Methods:

Changes in cellular metabolism in response to radiation are tracked by fluorescence lifetime of NADH. Expression of HIF‐1α was measured by immunofluorescence for both cell lines with and without irradiation. Radiation response is also monitored with additional treatment of a HIF‐1α inhibitor (chrysin) as well as a radical scavenger (glutathione). Changes in oxygen consumption and respiratory capacity are also monitored using the Seahorse XF analyzer.

Results:

An increase in HIF‐1α was found to be in response to radiation for the cancer cell line, but not the normal cell line. Radiation was found to shift metabolism toward glycolytic pathways in cancer cells as measured by oxygen consumption and respiratory capacity. Radiation response was found to be muted by addition of glutathione to cell media. HIF‐1α inhibition similarly muted radiation response in cancer.

Conclusion:

The HIF‐1 protein complex is a key regulator cellular metabolism through the regulation of glycolysis and glucose transport enzymes. Moreover, HIF‐1 has shown radio‐protective effects in tumor vascular endothelia, and has been implicated in metastatic aggression. Monitoring interplay between metabolism and the HIF‐1 protein complex can give a more fundamental understanding of radiotherapy response.
SU‐G‐IeP4‐05: Experience with a Practical Approach to the Release of Radioactive Patients from Radiation Safety Isolation
Authors: Wendt R , Erwin W , Fisher A , Jones S , Jimenez S , Wong F , Jessop A
Published: July 2016

Purpose:

The radioactive patient releases of the nuclear medicine department in a large cancer center were analyzed to compare the estimated doses to others to the regulatory limit and institutional targets and to gauge how onerous the patients’ instructions were.

Methods:

In‐house software that implements the NUREG 1556 approach and further considers fellow travelers, children and pregnant women and members of the public following Siegel, et al., is used to calculate release timing and to provide patients with individualized instructions. A retrospective analysis of the 218 releases in 2015 that required instructions included all I‐131 and Lu‐177 treatments.

Results:

There were 87 male and 131 female patients. They were 45.5±16.5 (8‐84) years old, weighed 83.3±21.8 kg and stood 168±10 cm tall with a body mass index of 29.3±6.7 kg/m2. 195 patients received 2.96±2.23 GBq of I‐131‐NaI for differentiated thyroid carcinoma and eight received 636±231 MBq of I‐131‐NaI for hyperthyroidism. There were eight administrations of 18.5 GBq of I‐131‐mIBG and seven administrations of 7.4 GBq of Lu‐177‐DOTATATE. The dose to the most exposed person was 1.67±1.05 (mode=0.60, median=1.15) mSv. The dose to a fellow traveler was 0.31±0.31 (mode=0.1, median=0.17) mSv. The dose to children and pregnant women was 0.51±0.34 (mode=1.0, median=0.42) mSv. The duration of isolation was 7.7±17.3 (mode=2, median=1.7) hours. The duration of sleeping alone was 60.4±127 (mode=0, median=15.5) hours. The time to delay traveling was 12.2±11 (mode=median=0) hours. The time to completely avoid children and pregnant women was 23.3±26.5 (0–254, mode=median=24) hours followed by limited contact for 20.6±68.1 (0–491, mode=median=0) hours. The time to avoid others (e.g., to wait to return to work) was 12.1±101 (0–1465, mode=median=0) hours.

Conclusion:

The estimated doses to others were often well below the limits set by regulation, 5 mSv, or prudent practice, 1 mSv. Most patients’ instructions were not hard to comply with.
SU‐G‐IeP4‐06: Feasibility of External Beam Treatment Field Verification Using Cherenkov Imaging
Authors: Black P , Na Y , Wuu C
Published: July 2016

Purpose:

Cherenkov light emission has been shown to correlate with ionizing radiation (IR) dose delivery in solid tissue. In order to properly correlate Cherenkov light images with real time dose delivery in a patient, we must account for geometric and intensity distortions arising from observation angle, as well as the effect of monitor units (MU) and field size on Cherenkov light emission. To test the feasibility of treatment field verification, we first focused on Cherenkov light emission efficiency based on MU and known field size (FS).

Methods:

Cherenkov light emission was captured using a PI‐MAX4 intensified charge coupled device(ICCD) system (Princeton Instruments), positioned at a fixed angle of 40° relative to the beam central axis. A Varian TrueBeam linear accelerator (linac) was operated at 6MV and 600MU/min to deliver an Anterior‐Posterior beam to a 5cm thick block phantom positioned at 100cm Source‐to‐Surface‐Distance(SSD). FS of 10×10, 5×5, and 2×2cm2 were used. Before beam delivery projected light field images were acquired, ensuring that geometric distortions were consistent when measuring Cherenkov field discrepancies. Cherenkov image acquisition was triggered by linac target current. 500 frames were acquired for each FS. Composite images were created through summation of frames and background subtraction. MU per image was calculated based on linac pulse delay of 2.8ms. Cherenkov and projected light FS were evaluated using ImageJ software.

Results:

Mean Cherenkov FS discrepancies compared to light field were <0.5cm for 5.6, 2.8, and 8.6 MU for 10×10, 5×5, and 2×2cm2 FS, respectably. Discrepancies were reduced with increasing field size and MU. We predict a minimum of 100 frames is needed for reliable confirmation of delivered FS.

Conclusion:

Current discrepancies in Cherenkov field sizes are within a usable range to confirm treatment delivery in standard and respiratory gated clinical scenarios at MU levels appropriate to standard MLC position segments