bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐F‐J‐44: Development of a Room Laser Based Real‐Time Alignment Monitoring System Using An Array of Photodiodes
Authors: Noh Y , Kim S , Kim T , Kang S , Kim D , Cho M , Kim K , Shin D , Suh T
Published: July 2016

Purpose:

To develop a real‐time alignment monitoring system (RAMS) to compensate for the limitations of the conventional room laser based alignment system, and to verify the feasibility of the RAMS.

Methods:

The RAMS was composed of a room laser sensing array (RLSA), an analog‐todigital converter, and a control PC. In the RLSA, seven photodiodes (each in 1 mm width) are arranged in a pattern that the RAMS provides alignment in 1 mm resolution. It works based on detecting laser light aligned on one of photodiodes. When misaligned, the laser would match with different photodiode(s) giving signal at unexpected location. Thus, how much displaced can be determined. To verify the reproducibility of the system with respect to time as well as repeated set‐ups, temporal reproducibility and repeatability test was conducted. The accuracy of the system was tested by obtaining detection signals with varying laser‐match positions.

Results:

The signal of the RAMS was found to be stable with respect to time. The repeatability test resulted in a maximum coefficient of variance of 1.14%, suggesting that the signal of the RAMS was stable over repeated set‐ups. In the accuracy test, signals between when the laser was aligned and notaligned with any of sensors could be distinguished by signal intensity. The signals of not‐aligned sensors were always below 75% of the signal of the aligned sensor. It was confirmed that the system could detect 1 mm of movement by monitoring the pattern of signals, and could observe the movement of the system in real‐time.

Conclusion:

We developed a room laser based alignment monitoring system. The feasibility test verified that the system is capable of quantitative alignment monitoring in real time. The system is relatively simple, not expensive, and considered to be easily incorporated into conventional room laser systems for real‐time alignment monitoring.

This research was supported by the Mid‐career Researcher Program through NRF funded by the Ministry of Science, ICT & Future Planning of Korea (NRF‐2014R1A2A1A10050270) and by the Radiation Technology R&D program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (No. 2013M2A2A7038291)
SU‐F‐J‐45: Sparing Normal Tissue with Ultra‐High Dose Rate in Radiation Therapy
Authors: Feng Y
Published: July 2016

Purpose:

To spare normal tissue by reducing the location uncertainty of a moving target, we proposed an ultra‐high dose rate system and evaluated.

Methods:

High energy electrons generated with a linear accelerator were injected into a storage ring to be accumulated. The number of the electrons in the ring was determined based on the prescribed radiation dose. The dose was delivered within a millisecond, when an online imaging system found that the target was in the position that was consistent with that in a treatment plan. In such a short time period, the displacement of the target was negligible. The margin added to the clinical target volume (CTV) could be reduced that was evaluated by comparing of volumes between CTV and ITV in 14 cases of lung stereotactic body radiation therapy (SBRT) treatments. A design of the ultra‐high dose rate system was evaluated based clinical needs and the recent developments of low energy (a few MeV) electron storage ring.

Results:

This design of ultra‐high dose rate system was feasible based on the techniques currently available. The reduction of a target volume was significant by reducing the margin that accounted the motion of the target. ∼50% volume reduction of the internal target volume (ITV) could be achieved in lung SBRT treatments.

Conclusion:

With this innovation of ultra‐high dose rate system, the margin of target is able to be significantly reduced. It will reduce treatment time of gating and allow precisely specified gating window to improve the accuracy of dose delivering.
SU‐F‐J‐47: Inherent Uncertainty in the Positional Shifts Determined by a Volumetric Cone Beam Imaging System
Authors: Giri U , Ganesh T , Saini V , Munshi A , Sarkar B , Mohanti B
Published: July 2016

Purpose:

To quantify inherent uncertainty associated with a volumetric imaging system in its determination of positional shifts.

Methods:

The study was performed on an Elekta Axesse™ linac's XVI cone beam computed tomography (CBCT) system. A CT image data set of a Penta‐ Guide phantom was used as reference image by placing isocenter at the center of the phantom.The phantom was placed arbitrarily on the couch close to isocenter and CBCT images were obtained. The CBCT dataset was matched with the reference image using XVI software and the shifts were determined in 6‐dimensions. Without moving the phantom, this process was repeated 20 times consecutively within 30 minutes on a single day. Mean shifts and their standard deviations in all 6‐dimensions were determined for all the 20 instances of imaging. For any given day, the first set of shifts obtained was kept as reference and the deviations of the subsequent 19 sets from the reference set were scored. Mean differences and their standard deviations were determined. In this way, data were obtained for 30 consecutive working days.

Results:

Tabulating the mean deviations and their standard deviations observed on each day for the 30 measurement days, systematic and random errors in the determination of shifts by XVI software were calculated. The systematic errors were found to be 0.03, 0.04 and 0.03 mm while random errors were 0.05, 0.06 and 0.06 mm in lateral, craniocaudal and anterio‐posterior directions respectively. For rotational shifts, the systematic errors were 0.02°, 0.03° and 0.03° and random errors were 0.06°, 0.05° and 0.05° in pitch, roll and yaw directions respectively.

Conclusion:

The inherent uncertainties in every image guidance system should be assessed and baseline values established at the time of its commissioning. These shall be periodically tested as part of the QA protocol.
SU‐F‐J‐49: IGRT Credentialing in NCTN Trials
Authors: Lowenstein J , Molineu A , Al‐Hallaq H , Matuszak M , Craig T , Ulin K , Xiao Y , Yin F , Followill D
Published: July 2016

Purpose:

To make Image Guided Radiation Therapy (IGRT) credentialing a more unified, consistent and efficient process across the entire National Clinical Trial Network (NCTN).

Methods:

IGRT plays a role in several advanced NCTN trials. Previously an institution had to be IGRT credentialed for each protocol. When institutions were allowed to use previous credentials for new protocols it was limited to the same disease site as the original credentialing. The credentialing was analyzed by the physics PI of the protocol. We consulted with several of these physicists to determine what is important to consider when reviewing submissions and to learn ways to apply credentialing more broadly.

Results:

For trials open in 2016, IGRT credentialing can be simplified to cover either boney anatomy or soft tissue. This revised credentialing will cover all disease sites based on the type of anatomy, unless otherwise stated within the protocol. Institutions will submit will complete an online questionnaire about their IGRT procedures. Boney anatomy requirements will include submission of data from 2 sequential fraction of both a patient aligned with boney anatomy and pelvic patient. Soft tissue will require similar submissions for a patient aligned using soft tissue and a pelvic patient. Institutions will only be required to submit the pelvic patient once. Data should be in DICOM format and includes planning CT set, RT structure set, RT plan file, RT dose file, localization images and spatial registration file (if available). Reviews will be done by IROC‐Houston staff who will continue to provide feedback to the sites.

Conclusion:

This revised IGRT credentialing process will bring consistency, a savings in time and effort for both the IROC Houston QA office and to those institutions wanting to be credentialed to participate in NCTN Trials.

Sponsored by NIH/NCI CA10953
SU‐F‐J‐53: A 3D Printed Phantom for the Use of Daily Quality Assurance Alignment Tests
Authors: Woods K , Ayan A , Woollard J , Gardner N , Gupta N
Published: July 2016

Purpose:

To discuss experiences and results for a 3D printed QA phantom used for daily alignment purposes for a six degrees‐of‐freedom (6DoF) table

Methods:

A 3D model was created using a fused deposition modeling (FDM) printer using free online computer‐aided design (CAD) software. The model has been under use for daily QA alignment tests for a 6DoF couch. An aligned and angled baseplate were also printed in order to introduce known angles for 6DoF corrections during image‐guidance. Unique registration contours were created on the faces of the phantom in order to achieve a better cone‐beam computed tomography (CBCT) match using an auto‐registration algorithm. A BB was also introduced at the center of the phantom in order to deliver an integrated daily Winston‐Lutz (WL) test. Translational, rotational, and WL results were tabulated over one month.

Results:

The 'honeycomb’ structure of the print was apparent in the EPID images for the WL test, which affected the results of the analysis software. This was fixed by inserting a cube made of polyoxymethylene within the 3D phantom that encompass the BB. Auto‐registration results for the three translational and three rotational from a known offset to the BB isocenter consistently fell within 1 mm and 0.2°, respectively. WL tests resulted in an average of 0.71 ± 0.14 mm.

Conclusion:

3D printed models allow for accurate builds that can be customized to a variety of clinical needs. Results from translational, rotational, and WL show consistent results over a month's time. Given its relatively cheap and streamlined workflow, 3D printing could be implemented into any clinic looking to create customized phantoms.
SU‐F‐J‐55: Feasibility of Supraclavicular Field Treatment by Investigating Variation of Junction Position Between Breast Tangential and Supraclavicular Fields for Deep Inspiration Breath Hold (DIBH) Left Breast Radiation
Authors: Zhao H , Sarkar V , Paxton A , Rassiah‐Szegedi P , Huang Y , Szegedi M , Huang L , Su F , Salter B
Published: July 2016

Purpose:

To explore the feasibility of supraclavicular field treatment by investigating the variation of junction position between tangential and supraclavicular fields during left breast radiation using DIBH technique.

Methods:

Six patients with left breast cancer treated using DIBH technique were included in this study. AlignRT system was used to track patient's breast surface. During daily treatment, when the patient's DIBH reached preset AlignRT tolerance of ±3mm for all principle directions (vertical, longitudinal, and lateral), the remaining longitudinal offset was recorded. The average with standard‐deviation and the range of daily longitudinal offset for the entire treatment course were calculated for all six patients (93 fractions totally). The ranges of average ± 1σ and 2σ were calculated, and they represent longitudinal field edge error with the confidence level of 68% and 95%. Based on these longitudinal errors, dose at junction between breast tangential and supraclavicular fields with variable gap/overlap sizes was calculated as a percentage of prescription (on a representative patient treatment plan).

Results:

The average of longitudinal offset for all patients is 0.16±1.32mm, and the range of longitudinal offset is −2.6 to 2.6mm. The range of longitudinal field edge error at 68% confidence level is −1.48 to 1.16mm, and at 95% confidence level is −2.80 to 2.48mm. With a 5mm and 1mm gap, the junction dose could be as low as 37.5% and 84.9% of prescription dose; with a 5mm and 1mm overlap, the junction dose could be as high as 169.3% and 117.6%.

Conclusion:

We observed longitudinal field edge error at 95% confidence level is about ±2.5mm, and the junction dose could reach 70% hot/cold between different DIBH. However, over the entire course of treatment, the average junction variation for all patients is within 0.2mm. The results from our study shows it is potentially feasible to treat supraclavicular field with breast tangents.
SU‐F‐J‐56: The Connection Between Cherenkov Light Emission and Radiation Absorbed Dose in Proton Irradiated Phantoms
Authors: Darafsheh A , Taleei R , Kassaee A , Finlay J
Published: July 2016

Purpose:

Range verification in proton therapy is of great importance. Cherenkov light follows the photon and electron energy deposition in water phantom. The purpose of this study is to investigate the connection between Cherenkov light generation and radiation absorbed dose in a water phantom irradiated with proton beams.

Methods:

Monte Carlo simulation was performed by employing FLUKA Monte Carlo code to stochastically simulate radiation transport, ionizing radiation dose deposition, and Cherenkov radiation in water phantoms. The simulations were performed for proton beams with energies in the range 50–600 MeV to cover a wide range of proton energies.

Results:

The mechanism of Cherenkov light production depends on the initial energy of protons. For proton energy with 50–400 MeV energy that is below the threshold (∼483 MeV in water) for Cherenkov light production directly from incident protons, Cherenkov light is produced mainly from the secondary electrons liberated as a result of columbic interactions with the incident protons. For proton beams with energy above 500 MeV, in the initial depth that incident protons have higher energy than the Cherenkov light production threshold, the light has higher intensity. As the slowing down process results in lower energy protons in larger depths in the water phantom, there is a knee point in the Cherenkov light curve vs. depth due to switching the Cherenkov light production mechanism from primary protons to secondary electrons. At the end of the depth dose curve the Cherenkov light intensity does not follow the dose peak because of the lack of high energy protons to produce Cherenkov light either directly or through secondary electrons.

Conclusion:

In contrast to photon and electron beams, Cherenkov light generation induced by proton beams does not follow the proton energy deposition specially close to the end of the proton range near the Bragg peak.
SU‐F‐J‐57: Effectiveness of Daily CT‐Based Three‐Dimensional Image Guided and Adaptive Proton Therapy
Authors: Moriya S , Tachibana H , Hotta K , Nakamura N , Baba H , Kohno R , Miyakawa S , Kurosawa T , Akimoto T
Published: July 2016

Purpose:

Daily CT‐based three‐dimensional image‐guided and adaptive (CTIGRT‐ART) proton therapy system was designed and developed. We also evaluated the effectiveness of the CTIGRT‐ART.

Methods:

Retrospective analysis was performed in three lung cancer patients: Proton treatment planning was performed using CT image datasets acquired by Toshiba Aquilion ONE. Planning target volume and surrounding organs were contoured by a well‐trained radiation oncologist. Dose distribution was optimized using 180‐deg. and 270‐deg. two fields in passive scattering proton therapy. Well commissioned Simplified Monte Carlo algorithm was used as dose calculation engine. Daily consecutive CT image datasets was acquired by an in‐room CT (Toshiba Aquilion LB). In our in‐house program, two image registrations for bone and tumor were performed to shift the isocenter using treatment CT image dataset. Subsequently, dose recalculation was performed after the shift of the isocenter. When the dose distribution after the tumor registration exhibits change of dosimetric parameter of CTV D90% compared to the initial plan, an additional process of was performed that the range shifter thickness was optimized. Dose distribution with CTV D90% for the bone registration, the tumor registration only and adaptive plan with the tumor registration was compared to the initial plan.

Results:

In the bone registration, tumor dose coverage was decreased by 16% on average (Maximum: 56%). The tumor registration shows better coverage than the bone registration, however the coverage was also decreased by 9% (Maximum: 22%) The adaptive plan shows similar dose coverage of the tumor (Average: 2%, Maximum: 7%).

Conclusion:

There is a high possibility that only image registration for bone and tumor may reduce tumor coverage. Thus, our proposed methodology of image guidance and adaptive planning using the range adaptation after tumor registration would be effective for proton therapy.

This research is partially supported by Japan Agency for Medical Research and Development (AMED).
SU‐F‐J‐58: Evaluation of RayStation Hybrid Deformable Image Registration for Accurate Contour Propagation in Adaptive Planning
Authors: Rong Y , Rao S , Daly M , Wright C , Benedict S , Yamamoto T
Published: July 2016

Purpose:

Adaptive radiotherapy requires complete new sets of regions of interests (ROIs) delineation on the mid‐treatment CT images. This work aims at evaluating the accuracy of the RayStation hybrid deformable image registration (DIR) algorithm for its overall integrity and accuracy in contour propagation for adaptive planning.

Methods:

The hybrid DIR is based on the combination of intensity‐based algorithm and anatomical information provided by contours. Patients who received mid‐treatment CT scans were identified for the study, including six lung patients (two mid‐treatment CTs) and six head‐and‐neck (HN) patients (one mid‐treatment CT). DIRpropagated ROIs were compared with physician‐drawn ROIs for 8 ITVs and 7 critical organs (lungs, heart, esophagus, and etc.) for the lung patients, as well as 14 GTVs and 20 critical organs (mandible, eyes, parotids, and etc.) for the HN patients. Volume difference, center of mass (COM) difference, and Dice index were used for evaluation. Clinical‐relevance of each propagated ROI was scored by two physicians, and correlated with the Dice index.

Results:

For critical organs, good agreement (Dice>0.9) were seen on all 7 for lung patients and 13 out of 20 for HN patients, with the rest requiring minimal edits. For targets, COM differences were within 5 mm on average for all patients. For Lung, 5 out of 8 ITVs required minimal edits (Dice 0.8–0.9), with the rest 2 needed re‐drawn due to their small volumes (<10 cc). However, the propagated HN GTVs resulted in relatively low Dice values (0.5–0.8) due to their small volumes (3–40 cc) and high variability, among which 2 required re‐drawn due to new nodal target identified on the mid‐treatment CT scans.

Conclusion:

The hybrid DIR algorithm was found to be clinically useful and efficient for lung and HN patients, especially for propagated critical organ ROIs. It has potential to significantly improve the workflow in adaptive planning.
SU‐F‐J‐69: The Dosimetric Impact of Interfraction Anorectum and Bladder Variability in Prostate Radiation Therapy
Authors: Patel V , Chinea F , Abramowitz M , Studenski M
Published: July 2016

Purpose:

In the era of dose escalation and numerous protocols evaluating radiation delivery to the prostate, it is imperative to achieve accurate and standardized daily set up. At the Sylvester Comprehensive Cancer Center, patients are instructed to drink 8 ounces of water 30 minutes prior to RT and follow a low residue diet to ensure that the anorectum is not distended and the bladder is adequately filled. If daily CBCT imaging shows any variation, the patient is removed from the table and drinks water or evacuates their rectum prior to a repeat CBCT. Here we attempt to quantify the efficacy of this procedure.

Methods:

CBCTs were collected for 5 patients receiving 40 fractions of definitive treatment for prostate cancer. CBCTs were imported into MIM (v6.5.7, Cleveland OH) and the bladder, anorectum, and prostate were contoured. Using the daily registration reviewed by the attending physician, the planning dose was rigidly transferred to the daily CBCT. On days that multiple CBCTs were performed due to inadequate anorectum or bladder preparation, the repeated and final CBCTs were evaluated for variations in V40Gy and V65Gy to both the anorectum and bladder.

Results:

A high level of variability in doses to the anorectum and bladder was found in the scans that were not utilized for treatment. The aggregate lower quartile for the unused versus used CBCTs was 27.2% vs. 16.83% for V40Gy and 8.53% vs. 5.66% for V65Gy bladder. The upper quartiles showed to be 48.88% vs. 41.92% and 21.05% vs. 20.55%. The combined lower quartile for the unused vs. used CBCTs was 8.24% vs. 5.49% for V40Gy and 0.57% vs. 0.0% for V65Gy anorectum. The upper quartiles were 34.35% vs. 33.25% and 18.37% vs. 16.11%.

Conclusion:

This study shows that daily imaging is insufficient and that proper bladder and anorectum preparation are essential to deliver proper treatment.
SU‐F‐J‐71: Improving CT Quality for Radiation Therapy Planning and Delivery Guidance Using a Non‐Linear Contrast Enhancement Technique
Authors: Noid G , Tai A , Li X
Published: July 2016

Purpose:

Advanced image post‐processing techniques which enhance soft‐tissue contrast in CT have not been widely employed for RT planning or delivery guidance. The purpose of this work is to assess the soft‐tissue contrast enhancement from non‐linear contrast enhancing filters and its impact in RT. The contrast enhancement reduces patient alignment uncertainties.

Methods:

Non‐linear contrast enhancing methods, such as Best Contrast (Siemens), amplify small differences in X‐ray attenuation between two adjacent structure without significantly increasing noise. Best Contrast (BC) separates a CT into two frequency bands. The low frequency band is modified by a non‐linear scaling function before recombination with the high frequency band. CT data collected using a CT‐on‐rails (Definition AS Open, Siemens) during daily CT‐guided RT for 6 prostate cancer patients and an image quality phantom (The Phantom Laboratory) were analyzed. Images acquired with a standard protocol (120 kVp, 0.6 pitch, 18 mGy CTDIvol) were processed before comparison to the unaltered images. Contrast and noise were measured in the the phantom. Inter‐observer variation was assessed by placing prostate contours on the 12 CT study sets, 6 enhanced and 6 unaltered, in a blinded study involving 8 observers.

Results:

The phantom data demonstrate that BC increased the contrast between the 1.0% supra‐slice element and the background substrate by 46.5 HU while noise increased by only 2.3 HU. Thus the contrast to noise ratio increased from 1.28 to 6.71. Furthermore, the variation in centroid position of the prostate contours was decreased from 1.3±0.4 mm to 0.8±0.3 mm. Thus the CTV‐to‐PTV margin was reduced by 1.1 mm. The uncertainty in delineation of the prostate/rectum edge decreased by 0.5 mm.

Conclusion:

As demonstrated in phantom and patient scans the BC filter accentuates soft‐tissue contrast. This enhancement leads to reduced inter‐observer variation, which should improve RT planning and delivery.

Supported by Siemens
SU‐F‐J‐76: Evaluation of the Performance of Different Deformable Image Registration Algorithms in Helical, Axial and Cone‐Beam CT Images of a Mobile Phantom
Authors: Jaskowiak J , Alsbou N , Ahmad S , Ali I
Published: July 2016

Purpose:

To investigate quantitatively the performance of different deformable‐image‐registration algorithms (DIR) with helical (HCT), axial (ACT) and cone‐beam CT (CBCT) by evaluating the variations in the CT‐numbers and lengths of targets moving with controlled motion‐patterns.

Methods:

Four DIR‐algorithms including demons, fast‐demons, Horn‐Schunk and Locas‐Kanade from the DIRART‐software are used to register CT‐images of a mobile‐phantom. A mobile‐phantom is scanned with different imaging techniques that include helical, axial and cone‐beam CT. The phantom includes three targets with different lengths that are made from water‐equivalent material and inserted in low‐density‐foam which is moved with adjustable motion‐amplitudes and frequencies.

Results:

Most of the DIR‐algorithms are able to produce the lengths of the stationary‐targets, however, they do not produce the CT‐number values in CBCT. The image‐artifacts induced by motion are more regular in CBCT imaging where the mobile‐target elongation increases linearly with motion‐amplitude. In ACT and HCT, the motion‐artifacts are irregular where some mobile ‐targets are elongated or shrunk depending on the motion‐phase during imaging. The DIR‐algorithms are successful in deforming the images of the mobile‐targets to the images of the stationary‐targets producing the CT‐number values and length of the target for motion‐amplitudes < 20 mm. Similarly in ACT, all DIR‐algorithms produced the actual CT‐number and length of the stationary‐targets for motion‐amplitudes < 15 mm. As stronger motion‐artifacts are induced in HCT and ACT, DIR‐algorithms fail to produce CT‐values and shape of the stationary‐targets and fast‐demons‐algorithm has worst performance.

Conclusion:

Most of DIR‐algorithms produce the CT‐number values and lengths of the stationary‐targets in HCT and ACT images that has motion‐artifacts induced by small motion‐amplitudes. As motion‐amplitudes increase, the DIR‐algorithms fail to deform mobile‐target images to the stationary‐images in HCT and ACT. In CBCT, DIR‐algorithms are successful in producing length and shape of the stationary‐targets, however, they fail to produce the accurate CT‐number level.
SU‐F‐J‐81: Evaluation of Automated Deformable Registration Between Planning Computed Tomography (CT) and Daily Cone Beam CT Images Over the Course of Prostate Cancer Radiotherapy
Authors: Matney J , Hammers J , Kaidar‐Person O , Wang A , Chen R , Das S , Marks L , Mavroidis P
Published: July 2016

Purpose:

To compute daily dose delivered during radiotherapy, deformable registration needs to be relatively fast, automated, and accurate. The aim of this study was to evaluate the performance of commercial deformable registration software for deforming between two modalities: planning computed tomography (pCT) images acquired for treatment planning and cone beam (CB) CT images acquired prior to each fraction of prostate cancer radiotherapy.

Methods:

A workflow was designed using MIM Software™ that aligned and deformed pCT into daily CBCT images in two steps: (1) rigid shifts applied after daily CBCT imaging to align patient anatomy to the pCT and (2) normalized intensity‐based deformable registration to account for interfractional anatomical variations. The physician‐approved CTV and organ and risk (OAR) contours were deformed from the pCT to daily CBCT over the course of treatment. The same structures were delineated on each daily CBCT by a radiation oncologist. Dice similarity coefficient (DSC) mean and standard deviations were calculated to quantify the deformable registration quality for prostate, bladder, rectum and femoral heads.

Results:

To date, contour comparisons have been analyzed for 31 daily fractions of 2 of 10 of the cohort. Interim analysis shows that right and left femoral head contours demonstrate the highest agreement (DSC: 0.96±0.02) with physician contours. Additionally, deformed bladder (DSC: 0.81±0.09) and prostate (DSC: 0.80±0.07) have good agreement with physician‐defined daily contours. Rectum contours have the highest variations (DSC: 0.66±0.10) between the deformed and physician‐defined contours on daily CBCT imaging.

Conclusion:

For structures with relatively high contrast boundaries on CBCT, the MIM automated deformable registration provided accurate representations of the daily contours during treatment delivery. These findings will permit subsequent investigations to automate daily dose computation from CBCT. However, improved methods need to be investigated to improve deformable results for rectum contours.
SU‐F‐J‐84: Comparison of Quantitative Deformable Image Registration Evaluation Tools: Application to Prostate IGART
Authors: Dogan N , Weiss E , Sleeman W , Christensen G , Williamson J , Ford J
Published: July 2016

Purpose:

Errors in displacement vector fields (DVFs) generated by Deformable Image Registration (DIR) algorithms can give rise to significant uncertainties in contour propagation and dose accumulation in Image‐Guided Adaptive Radiotherapy (IGART). The purpose of this work is to assess the accuracy of two DIR algorithms using a variety of quality metrics for prostate IGART.

Methods:

Pelvic CT images were selected from an anonymized database of nineteen prostate patients who underwent 8–12 serial scans during radiotherapy. Prostate, bladder, and rectum were contoured on 34 image‐sets for three patients by the same physician. The planning CT was deformably‐registered to daily CT using three variants of the Small deformation Inverse Consistent Linear Elastic (SICLE) algorithm: Grayscale‐driven (G), Contour‐driven (C, which utilizes segmented structures to drive DIR), combined (G+C); and also grayscale ITK demons (Gd). The accuracy of G, C, G+C SICLE and Gd registrations were evaluated using a new metric Edge Gradient Distance to Agreement (EGDTA) and other commonly‐used metrics such as Pearson Correlation Coefficient (PCC), Dice Similarity Index (DSI) and Hausdorff Distance (HD).

Results:

C and G+C demonstrated much better performance at organ boundaries, revealing the lowest HD and highest DSI, in prostate, bladder and rectum. G+C demonstrated the lowest mean EGDTA (1.14 mm), which corresponds to highest registration quality, compared to G and C DVFs (1.16 and 2.34 mm). However, demons DIR showed the best overall performance, revealing lowest EGDTA (0.73 mm) and highest PCC (0.85).

Conclusion:

As expected, both C‐ and C+G SICLE more accurately reproduce manually‐contoured target datasets than G‐SICLE or Gd using HD and DSI metrics. In general, the Gd appears to have difficulty reproducing large daily position and shape changes in the rectum and bladder. However, Gd outperforms SICLE in terms of EGDTA and PCC metrics, possibly at the expense of topological quality of the estimated DVFs.
SU‐F‐J‐85: Evaluation of the Velocity Deformable Image Registration Algorithm
Authors: Polan D , Kamp J , Lee JY , Chapman C , Green M , Payal S , Kessler M , Brock K
Published: July 2016

Purpose:

To perform validation and commissioning of a commercial deformable image registration (DIR) algorithm (Velocity, Varian Medical Systems) for numerous clinical sites using single and multi‐modality images.

Methods:

In this retrospective study, the DIR algorithm was evaluated for 10 patients in each of the following body sites: head and neck (HN), prostate, liver, and gynecological (GYN). HN DIRs were evaluated from planning (p)CT to re‐pCT and pCTs to daily CBCTs using dice similarity coefficients (DSC) of corresponding anatomical structures. Prostate DIRs were evaluated from pCT to CBCTs using DSC and target registration error (TRE) of implanted RF beacons within the prostate. Liver DIRs were evaluated from pMR to pCT using DSC and TRE of vessel bifurcations. GYN DIRs were evaluated between fractionated brachytherapy MRIs using DSC of corresponding anatomical structures.

Results:

Analysis to date has given average DSCs for HN pCT‐to‐(re)pCT DIR for the brainstem, cochleas, constrictors, spinal canal, cord, esophagus, larynx, parotids, and submandibular glands as 0.88, 0.65, 0.67, 0.91, 0.77, 0.69, 0.77, 0.87, and 0.71, respectively. Average DSCs for HN pCT‐to‐CBCT DIR for the constrictors, spinal canal, esophagus, larynx, parotids, and submandibular glands were 0.64, 0.90, 0.62, 0.82, 0.75, and 0.69, respectively. For prostate pCT‐to‐CBCT DIR the DSC for the bladder, femoral heads, prostate, and rectum were 0.71, 0.82, 0.69, and 0.61, respectively. Average TRE using implanted beacons was 3.35 mm. For liver pCT‐to‐pMR, the average liver DSC was 0.94 and TRE was 5.26 mm. For GYN MR‐to‐MR DIR the DSC for the bladder, sigmoid colon, GTV, and rectum were 0.79, 0.58, 0.67, and 0.76, respectively.

Conclusion:

The Velocity DIR algorithm has been evaluated over a number of anatomical sites. This work functions to document the uncertainties in the DIR in the commissioning process so that these can be accounted for in the development of downstream clinical processes.

This work was supported in part by a co‐development agreement with Varian Medical Systems
SU‐F‐J‐87: Impact Of The Dosimetric Consequences From Minimal Displacements Throughout The Treatment Time In APBI With SAVI Applicators
Authors: Chandrasekara S , Pella S , Hyvarinen M , Pinder J
Published: July 2016

Purpose:

To assess the variation in dose received by the organs at risk (OARs) due to inter‐fractional motion by SAVI to determine the importance of providing proper immobilization

Methods:

An analysis of 15 patients treated with SAVI applicators were considered for this study. Treatment planning teams did not see significant changes in their CT scans through scout images and initial treatment plan was used for the entire treatment. These scans, taken before each treatment were imported in to the treatment planning system and were fused together with respective to the applicator, using landmark registration. Dosimetric evaluations were performed. Dose received by skin, ribs and PTV(Planning target volume) respect to the initial treatment plan were measured.

Results:

Contours of the OARs were not similar with the initial image. Deduction in volumes of PTV and cavity, small deviations in displacements from the applicator to the OARs, difference in doses received by the OARs between treatments were noticed. The maximum, minimum, average doses varied between 10% to 20% 5% to 8% and 15% to 20% in ribs and skin. The 0.1cc doses to OARs showed an average change of 10% of the prescribed dose. PTV was receiving a different dose than the estimated dose

Conclusion:

The variation in volumes and isodoses related to the OARs, PTV receiving a lesser dose than the prescribed dose indicate that the estimated doses are different from the received dose. This study reveals the urgent need of improving the immobilization methods. Taking a CT scan before each treatment and replanning is helpful to minimize the risk of delivering undesired high doses to the OARs. Patient positioning, motion, respiration, observer differences and time lap between the planning and treating can arise more complications. VacLock, Positioning cushions, Image guided brachytherapy and adjustable registration should be used for further improvements.
SU‐F‐J‐95: Impact of Shape Complexity On the Accuracy of Gradient‐Based PET Volume Delineation
Authors: Dance M , Wu G , Gao Y , Pirozzi S , Nelson A , Das S , Lian J
Published: July 2016

Purpose:

Explore correlation of tumor complexity shape with PET target volume accuracy when delineated with gradient‐based segmentation tool.

Methods:

A total of 24 clinically realistic digital PET Monte Carlo (MC) phantoms of NSCLC were used in the study. The phantom simulated 29 thoracic lesions (lung primary and mediastinal lymph nodes) of varying size, shape, location, and 18F‐FDG activity. A program was developed to calculate a curvature vector along the outline and the standard deviation of this vector was used as a metric to quantify a shape's “complexity score”. This complexity score was calculated for standard geometric shapes and MC‐generated target volumes in PET phantom images. All lesions were contoured using a commercially available gradient‐based segmentation tool and the differences in volume from the MC‐generated volumes were calculated as the measure of the accuracy of segmentation.

Results:

The average absolute percent difference in volumes between the MC‐volumes and gradient‐based volumes was 11% (0.4%–48.4%). The complexity score showed strong correlation with standard geometric shapes. However, no relationship was found between the complexity score and the accuracy of segmentation by gradient‐based tool on MC simulated tumors (R2 = 0.156). When the lesions were grouped into primary lung lesions and mediastinal/mediastinal adjacent lesions, the average absolute percent difference in volumes were 6% and 29%, respectively. The former group is more isolated and the latter is more surround by tissues with relatively high SUV background.

Conclusion:

The complexity shape of NSCLC lesions has little effect on the accuracy of the gradient‐based segmentation method and thus is not a good predictor of uncertainty in target volume delineation. Location of lesion within a relatively high SUV background may play a more significant role in the accuracy of gradient‐based segmentation.
SU‐F‐J‐98: Improvement and Evaluation Of Deformation Image Registration On Parotid Glands During Radiation Therapy for Nasopharyngeal Cancer
Authors: Xu S , Wu Z , Liu B , Li Y , Gong H , Zhou F , Qu B , Liu Y
Published: July 2016

Purpose:

To quantitatively evaluate the strategic innovation and accuracy variation of deformation registration algorithm for parotid glands using the similarity Dice coefficient during the course of radiation therapy (RT) for nasopharyngeal cancer (NPC).

Methods:

Daily MVCT data for 10 patients with pathologically proven nasopharyngeal cancers were analyzed. The data were acquired using tomotherapy (TomoTherapy, Accuray) at the PLA General Hospital. The prescription dose to the primary target was 70Gy in 33 fractions. Two kinds of contours for parotid glands on daily MVCTs were obtained by populating these contours from planning CTs to the daily CTs via rigid‐body registration with or without the rotation shifts using the in‐house tools and the Adaptive plan software (Adaptive Plan, TomoTherapy), and were edited manually if necessary. The diffeomorphic Demons algorithm developed in the in‐house tool was used to propagate the parotid structures from the daily CTs to planning CTs. The differences of the mapped parotid contours in two methods were evaluated using Dice similarity index (DSI). Two‐tailed t‐test analysis was carried out to compare the DSI changes during the course of RT.

Results:

For 10 patient plans, the accuracy of deformation image registration (DIR) with the rotation shift was obviously better than those without the rotation shift. The Dice scores of the ipsi‐ and contra‐lateral parotids for with and without the rotation shifts were found to be correlated with each other [0.904±0.031 vs 0.919±0.030 (p<0.001); 0.900±0.031 vs 0.910±0.032 (p<0.001)]. The Dice scores for the parotids have shown the reduction with the changes of parotid volumes during RT. The DSI values between the first and last fraction were 0.932±0.020 vs 0.899±0.030 in 10 patient plans.

Conclusion:

DIR was successfully improved using the strategic innovation for ART. And the decrease of DIR accuracy has also been found during the delivery of fractionated radiotherapy.

This work was supported in part by the grant from Chinese Natural Science Foundation (Grant No. 11105225).
SU‐F‐J‐100: Standardized Biodistribution Template for Nuclear Medicine Dosimetry Collection and Reporting
Authors: Kesner A , Poli G , Beykan S , Lassman M
Published: July 2016

Purpose:

As the field of Nuclear Medicine moves forward with efforts to integrate radiation dosimetry into clinical practice we can identify the challenge posed by the lack of standardized dose calculation methods and protocols. All personalized internal dosimetry is derived by projecting biodistribution measurements into dosimetry calculations. In an effort to standardize organization of data and its reporting, we have developed, as a sequel to the EANM recommendation of “Good Dosimetry Reporting”, a freely available biodistribution template, which can be used to create a common point of reference for dosimetry data. It can be disseminated, interpreted, and used for method development widely across the field.

Methods:

A generalized biodistribution template was built in a comma delineated format (.csv) to be completed by users performing biodistribution measurements. The template is available for free download. The download site includes instructions and other usage details on the template.

Results:

This is a new resource developed for the community. It is our hope that users will consider integrating it into their dosimetry operations. Having biodistribution data available and easily accessible for all patients processed is a strategy for organizing large amounts of information. It may enable users to create their own databases that can be analyzed for multiple aspects of dosimetry operations. Furthermore, it enables population data to easily be reprocessed using different dosimetry methodologies. With respect to dosimetry‐related research and publications, the biodistribution template can be included as supplementary material, and will allow others in the community to better compare calculations and results achieved.

Conclusion:

As dosimetry in nuclear medicine become more routinely applied in clinical applications, we, as a field, need to develop the infrastructure for handling large amounts of data. Our organ level biodistribution template can be used as a standard format for data collection, organization, as well as for dosimetry research and software development.
SU‐F‐J‐105: Towards a Novel Treatment Planning Pipeline Delivering Pareto‐ Optimal Plans While Enabling Inter‐ and Intrafraction Plan Adaptation
Authors: Kontaxis C , Breedveld S , Bol G , Sharfo A , Heijmen B , Lagendijk J , Raaymakers B
Published: July 2016

Purpose:

To develop a new IMRT treatment planning methodology suitable for the new generation of MR‐linear accelerator machines. The pipeline is able to deliver Pareto‐optimal plans and can be utilized for conventional treatments as well as for inter‐ and intrafraction plan adaptation based on real‐time MR‐data.

Methods:

A Pareto‐optimal plan is generated using the automated multicriterial optimization approach Erasmus‐iCycle. The resulting dose distribution is used as input to the second part of the pipeline, an iterative process which generates deliverable segments that target the latest anatomical state and gradually converges to the prescribed dose. This process continues until a certain percentage of the dose has been delivered. Under a conventional treatment, a Segment Weight Optimization (SWO) is then performed to ensure convergence to the prescribed dose. In the case of inter‐ and intrafraction adaptation, post‐processing steps like SWO cannot be employed due to the changing anatomy. This is instead addressed by transferring the missing/excess dose to the input of the subsequent fraction. In this work, the resulting plans were delivered on a Delta4 phantom as a final Quality Assurance test.

Results:

A conventional static SWO IMRT plan was generated for two prostate cases. The sequencer faithfully reproduced the input dose for all volumes of interest. For the two cases the mean relative dose difference of the PTV between the ideal input and sequenced dose was 0.1% and −0.02% respectively. Both plans were delivered on a Delta4 phantom and passed the clinical Quality Assurance procedures by achieving 100% pass rate at a 3%/3mm gamma analysis.

Conclusion:

We have developed a new sequencing methodology capable of online plan adaptation. In this work, we extended the pipeline to support Pareto‐optimal input and clinically validated that it can accurately achieve these ideal distributions, while its flexible design enables inter‐ and intrafraction plan adaptation.

This research is financially supported by Elekta AB, Stockholm, Sweden.
SU‐F‐J‐106: Dose Adaptation with a Virtual 6D Couch for Frameless Brain Radiosurgery Via a Dedicated Gamma‐Ray Device
Authors: Cheung J , Braunstein S , Sneed P , McDermott M , Theodosopoulos P , Ma L
Published: July 2016

Purpose:

The couch for Gamma Knife Radiosurgery (GKSRS) is limited to translational movements. With frameless designs, patient positional rotations may become an important factor. Therefore, we investigated the effect of rotations for GKSRS and the ability to correct for these rotations with simple couch translations.

Methods:

Seven previously treated GKSRS patients with different disease types (tumor volumes 0.01–12cc) were selected for this study. The planning MRI images were processed in order to digitally rotate the stereotactic frame (Leksell G‐frame) to ±1, ±2, ±3, ±5, and ±10‐degrees in the transverse plane from the nominal position. These images were imported back into the clinical planning system (LGP 10.2) and dose from the original treatment plan was calculated with these rotational errors. Translation corrections for each shot based on the rotation transform matrix were applied to the plan and coverage and Paddick conformity index (PCI) were evaluated for the uncorrected and corrected plans.

Results:

The rotational errors resulted in large decreases in plan coverage, with some small tumors being missed completely with rotations of ±3‐degrees or more. The rotated plans resulted in an average (range) decreased coverage of 8% (0–33%), 28% (0–87%), 43% (0–100%), 57% (0–100%), and 72% (5–100%) for ±1, ±2, ±3, ±5, and ±10‐degrees, respectively. For the corrected plans, the average (range) decrease in coverage was only 1% (0–4%), even for the rotations of ±10‐degrees. The PCI differences improved as well, with the rotated plans resulting in decreased PCI of 2% (0–11%), 13% (0–32%), 22% (0–50%), 31% (1–56%), 42% (4–67%) for ±1, ±2, ±3, ±5, and ±10‐degrees, respectively, which improved to 1% for all of the corrected plans with a range from 5% decrease to 13% increase in PCI.

Conclusion:

The applications of simple 3D couch translations were successful in recovering rotation uncertainties up to ±10‐degrees for frameless GKSRS.
SU‐F‐J‐107: Online Adaptive VMAT Planning Based On Deformed Dose
Authors: Qiu R , Vassil A , Godley A
Published: July 2016

Purpose:

Prostate treatment with volumetric‐modulated arc therapy (VMAT) in conjunction with small PTV margins, allows the dose to the rectum and bladder to be minimized, at the potential cost of prostate coverage. Coverage can be restored by online adaptive planning. Here, the deformed planning dose is used as the goal for adaptive plan optimization.

Methods:

9 prostate patients with CT‐on‐Rails (CTOR) imaging were replanned using Monaco (Elekta AB, Stockholm, Sweden) with 2 VMAT arcs, and 70 Gy to 95% of the PTV. A variable margin of 4–6 mm was used. The planning CT was deformably registered to each CTOR, the resulting deformation field was then applied to morph the structures and dose to the CTORs, using ADMIRE (Elekta AB, Stockholm Sweden). The deformed dose, edited contours and CTOR were imported into Monaco, and the dose referred as a guide for plan optimization. The original treatment plan was also copied to the CTOR, keeping the center of the prostate as the isocenter, to mimic the current repositioning based therapy.

Results:

The deformed dose guided optimization maintained the prostate coverage and the sparing of OAR. The shifted plan was unable to do both. The mean percentage volume covered by 100% isodose line increased from 96.11±2.04 to 99.74±0.10 for prostate, and 83.48±2.63 to 94.61±0.34 for PTV by adapting the deformed dose guided optimization. PTV coverage is of some interest, as there still needs to be some margin for intra‐fraction motion. Besides, the resulting lower inter‐fraction dose variation of optimized plan implied a better dose delivery consistency.

Conclusion:

Using the planned dose, deformed to the daily CTOR provided a successful goal for adaptive optimization, allowing reduced margins, increased OAR sparing, and maintained prostate coverage.

Godley receives research grant from Elekta.