bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐D‐9A‐05: IBEX: An Open Software Infrastructure Platform to Accelerate Collaborative Work On Quantitative Image Features and Predictive Models
Authors: Zhang L , Hunter L , Fried D , Fave X , Yang J , Court L
Published: July 2014

Purpose:

Quantitative imaging analysis has great potential to improve the accuracy and efficiency of cancer research, but the lack of software infrastructure prohibits progress from developing and using its methods. We have developed a software platform to flexibly support common quantitative imaging analysis tasks such as multimodality image data import and review, feature algorithm development, predictive model design, and consistent data sharing among multi‐institutions.

Methods:

The IBEX(Imaging Biomarker Explorer) software package was developed under Matlab and C/C++. The software architecture deploys the modern Model‐View‐Controller (MVC) and unit testing programming concepts to isolate each task and to validate if their relevant data and algorithms are fit for use. The View component represents multimodality images with delineated structures (if available), which are imported using DICOM, CERR, or other native formats. Non‐image data, such as patient performance status can also be entered. The Controller component represents image pre‐processing and feature extraction algorithms. The Model component represents the predictive model formula and coefficients. Thanks to the unit testing implementation, the user has the option of reviewing the corresponding result to check the quality of data and algorithms at each stage. While IBEX itself is self‐contained and has implemented typical algorithms and models, it is an open system and additional algorithms and models can be easily added by defining them in library files. Also, a complete external model can be imported, including necessary data about pre‐processing algorithms, feature algorithms, model formula, and model coefficients. This greatly helps maintain data consistency when institutions attempt to validate external models.

Results:

Testers found the IBEX software to be intuitive and easy to use. All import, pre‐processing algorithms, and feature algorithms were fully validated.

Conclusion:

We have successfully implemented an open software infrastructure platform to accelerate work on quantitative imaging analysis and collaborative research activities.

This work was funded by the NCI(1R03CA178495‐01)
SU‐D‐9A‐07: Imaging Dose and Cancer Risk in Image‐Guided Radiotherapy of Cancers
Authors: Zhou L , Bai S , Zhang Y , Ming X , Zhang Y , Deng J
Published: July 2014

Purpose:

To systematically evaluate the imaging doses and cancer risks associated with various imaging procedures involving ionizing radiation during image‐guided radiotherapy of an increasingly large number of cancer patients.

Methods:

141 patients (52 brain cases, 47 thoracic cases, 42 abdominal cases, aged 3 to 91 years old) treated between October 2009 and March 2010 were included in this IRB‐approved retrospective study. During the whole radiotherapy course, each patient underwent at least one type of imaging procedures, i.e., kV portal, MV portal and kVCBCT, besides CT simulations. Based on Monte Carlo modeling and particle transport in human anatomy of various dimensions, the correlations between the radiation doses to the various organs‐at‐risk (OARs) at the head, the thoracic and the abdominal regions and one's weight, circumference, scan mAs and kVp have been obtained and used to estimate the radiation dose from a specific imaging procedure. The radiation‐induced excess relative risk (ERR) was then estimated with BEIR VII formulism based on one's gender, age and radiation dose. 1+ ERR was reported in this study as relative cancer risk.

Results:

For the whole cohort of 141 patients, the mean imaging doses from various imaging procedures were 8.3 cGy to the brain, 10.5 cGy to the lungs and 19.2 cGy to the red bone marrow, respectively. Accordingly, the cancer risks were 1.140, 1.369 and 2.671, respectively. In comparison, MV portal deposited largest doses to the lungs while kVCBCT delivered the highest doses to the red bone marrow.

Conclusion:

The compiled imaging doses to a patient during his/her treatment course were patient‐specific and site‐dependent, varying from 1.2 to 263.5 cGy on average, which were clinically significant and should be included in the treatment planning and overall decision‐making. Our results indicated the necessity of personalized imaging to maximize its clinical benefits while reducing the associated cancer risks.

Sichuan University Scholarship
SU‐E‐E‐04: Hurtles and Benefits to Establishing An Academic/industry Diagnostic Medical Physics Residency Collaboration
Authors: Nye J , Cuddy M , Heathcock G
Published: July 2014

Purpose:

Funding and administration of diagnostic residencies presents a barrier to the expansion of these programs. In this work, the authors detail elements included in establishing an academic and industry collaboration to share the training and finances of a new residency program.

Methods:

The goals of each partner were prioritized and strengths and weaknesses in expertise were identified as well as their potential benefit to each. Many of the hurtles concerning the broader program administration were addressed through an affiliation agreement. Aspects of program management specific to each resident such as deviations to the approved training plan were addressed through sub‐agreements. Some priorities identified may need to be actively managed throughout the resident's training period.

Results:

Several hurtles were identified in the administration and training of residents including conflicts between training and service, protection of proprietary materials/knowledge, intellectual property rights, funding and payment models, remote management, resident placement/scheduling and non‐compete agreements. Several benefits may be realized through an academic/industry collaboration including mentorship and teaching experience, scholarship, enhancement of the partner's reputation, marketing advantages, minimization of the administrative burden and training of future qualified staff. These hurtles and benefits should be well understood as some may not be negotiable due to institutional or company policies governing the operation of each partner.

Conclusion:

Residency collaborations between academic and industry environments present a unique set of hurtles but clear advantages to each stakeholder. The benefit to the future resident is an innovative educational experience comprised of hospital‐ and consultingbased medical practices.
SU‐E‐P‐05: Is Routine Treatment Planning System Quality Assurance Necessary?
Authors: Alaei P
Published: July 2014

Purpose:

To evaluate the variation of dose calculations using a treatment planning system (TPS) over a two year period and assessment of the need for TPS QA on regular intervals.

Methods:

Two phantoms containing solid water and lung‐ and bone‐equivalent heterogeneities were constructed in two different institutions for the same brand treatment planning system. Multiple plans, consisting of photons and electron beams, including IMRT and VMAT ones, were created and calculated on the phantoms. The accuracy of dose computation in the phantoms was evaluated at the onset by dose measurements within the phantoms. The dose values at up to 24 points of interest (POI) within the solid water, lung, and bone slabs, as well as mean doses to several regions of interest (ROI), were re‐calculated over a two‐year period which included two software upgrades. The variations in POI and ROI dose values were analyzed and evaluated.

Results:

The computed doses vary slightly month‐over‐month. There are noticeable variations at the times of software upgrade, if the upgrade involves remodeling and/or re‐commissioning of the beams. The variations are larger in certain points within the phantom, usually in the buildup region or near interfaces, and are almost non‐existent for electron beams.

Conclusion:

Routine TPS QA is recommended by AAPM and other professional societies, and is often required by accreditation organizations. The frequency and type of QA, though, is subject to debate. The results presented here demonstrate that the frequency of these tests could be at longer intervals than monthly. However, it is essential to perform TPS QA at the time of commissioning and after each software upgrade.
SU‐E‐P‐06: A Novel Hybrid Planning Approach to Allow More Patients Benefited by the Intensity Modulated Proton Therapy
Authors: Jiang S , Liao L , Li Y , Wang X , Li H , Zhu X , Sahoo N , Gillin M , Hojo Y , Sun J , Chang J , Liao Z , Grosshans D , Frank S , Zhang X
Published: July 2014

Purpose:

We report a hybrid scattering and scanning beam delivery approach, termed as (HimpsPT), which demonstrated that majority IMPT delivery can be potentially replaced with hybrid IMPT and PSPT delivery with similar or better plan quality.

Methods:

Three representative clinical cases, including head and neck (HN), skull base chordoma (CNS) and lung cancer, treated in MDACC Proton Therapy Center with IMPT were retrospectively redesigned using HimpsPT. The PSPT plans are designed with the same prescriptions as those of IMPT plans. The whole treatment can be delivered by either alternating or sequential PSPT and IMPT delivery. The dosimetric data and dose distributions of HimpsPT plans are compared with those of IMPT plans. We also performed a worst‐case robust analysis for all plans.

Results:

The target coverages for all cases are comparable. For the HN case, the mean dose of esophagus larynx, left parotid and right submandibular, oral cavity V20, the max dose of cord is 18.0, 36.1, 23.6, 47.2, 0.1, 31.7 Gy in HimpsPT plan, and 25.5, 33.8, 24.9, 49.1, 0.2, 33.8 Gy in IMPT plan. For the lung case, the lung V5, V20, V30, mean lung dose, heart V40, esophagus V70, cord maximum dose are 50.5%, 37.0%, 31.7%, 21.3 Gy, 7.2%, 4.9%, 35.5 Gy in HimpsPT plan, and 55.4%, 36.7%, 30.1%, 21.3 Gy, 7.7%, 8.4%, 36.8Gy in IMPT plans. For the CNS case, brainstem maximum dose is 50.5 Gy in HimpsPT plan and 55.4 Gy in IMPT plan due to sharp penumbra offered by the aperture of the PSPT plan in HimpsPT technique.

Conclusion:

For majority disease sites, the dosimetric advantage of IMPT technique can be achieved by the hybrid PSPT and IMPT technique, which enables the centers equipped with both scattering and scanning beam facilities to treat more patients which can be benefited by the scanning beam.
SU‐E‐I‐04: A Mammography Phantom to Measure Mean Glandular Dose and Image Quality
Authors: Lopez‐Pineda E , Ruiz‐Trejo C , E Brandan M
Published: July 2014

Purpose:

To evaluate mean glandular dose (MGD) and image quality in a selection of mammography systems using a novel phantom based on thermoluminescent dosemeters and the ACR wax insert.

Methods:

The phantom consists of two acrylic, 19 cm diameter, 4.5 cm thick, semicircular modules, used in sequence. The image quality module contains the ACR insert and is used to obtain a quality control image under automatic exposure conditions. The dosimetric module carries 15 TLD‐100 chips, some under Al foils, to determine air kerma and half‐value‐layer. TL readings take place at our laboratory under controlled conditions. Calibration was performed using an ionization chamber and a Senographe 2000D unit for a variety of beam qualities, from 24 to 40 kV, Mo and Rh anodes and filters. Phantom MGD values agree, on the average, within 3% with ionization chamber data, and their precision is better than 10% (k=1).

Results:

MGD and image quality have been evaluated in a selection of mammography units currently used in Mexican health services. The sample includes analogic (screen/film), flexible digital (CR), and full‐field digital image receptors. The highest MDG are associated to the CR technology. The most common image quality failure is due to artifacts (dust, intensifying screen scratches, and processor marks for film/screen, laser reader defects for CR).

Conclusion:

The developed phantom permits the MGD measurement without the need of a calibrated ionization chamber at the mammography site and can be used by a technician without the presence of a medical physicist. The results indicate the urgent need to establish quality control programs for mammography.
SU‐E‐I‐07: An Improved Technique for Scatter Correction in PET
Authors: Lin S , Wang Y , Lue K , Lin H , Chuang K
Published: July 2014

Purpose:

In positron emission tomography (PET), the single scatter simulation (SSS) algorithm is widely used for scatter estimation in clinical scans. However, bias usually occurs at the essential steps of scaling the computed SSS distribution to real scatter amounts by employing the scatter‐only projection tail. The bias can be amplified when the scatter‐only projection tail is too small, resulting in incorrect scatter correction. To this end, we propose a novel scatter calibration technique to accurately estimate the amount of scatter using pre‐determined scatter fraction (SF) function instead of the employment of scatter‐only tail information.

Methods:

As the SF depends on the radioactivity distribution and the attenuating material of the patient, an accurate theoretical relation cannot be devised. Instead, we constructed an empirical transformation function between SFs and average attenuation coefficients based on a serious of phantom studies with different sizes and materials. From the average attenuation coefficient, the predicted SFs were calculated using empirical transformation function. Hence, real scatter amount can be obtained by scaling the SSS distribution with the predicted SFs. The simulation was conducted using the SimSET. The Siemens Biograph™ 6 PET scanner was modeled in this study. The Software for Tomographic Image Reconstruction (STIR) was employed to estimate the scatter and reconstruct images. The EEC phantom was adopted to evaluate the performance of our proposed technique.

Results:

The scatter‐corrected image of our method demonstrated improved image contrast over that of SSS. For our technique and SSS of the reconstructed images, the normalized standard deviation were 0.053 and 0.182, respectively; the root mean squared errors were 11.852 and 13.767, respectively.

Conclusion:

We have proposed an alternative method to calibrate SSS (C‐SSS) to the absolute scatter amounts using SF. This method can avoid the bias caused by the insufficient tail information and therefore improve the accuracy of scatter estimation.
SU‐E‐I‐08: An Inpaint‐Based Interpolation Technique to Recover Blocked Information for Cone Beam CT with a Synchronized Moving Grid (SMOG)
Authors: Kong V , Zhang H , Ren L , Jin J
Published: July 2014

Purpose:

Synchronized moving grid (SMOG) is a promising technique to reduce scatter and ghost artifacts in cone beam computed tomography (CBCT). However, the grid blocks part of image information in each projection, and multiple projections at the same gantry angle have to been taken to obtain full information. Because of the continuity of a patient's anatomy in the projection, the blocked information may be estimated by interpolation. This study aims to evaluate an inpainting‐based interpolation approach to recover the missing information for CBCT reconstruction.

Method:

We used a simple region‐based inpainting approach to interpolate the missing information. For a pixel to be interpolated, we divided the nearby regions having image information into 6 sub‐regions: up‐left, up‐middle, up‐right, down‐left, down‐middle, and down‐right, each with 9 pixels. The average pixel value of each sub‐region was calculated. These average values, along with the pixel location, were used to determine the interpolated pixel value. We compared our approach with the Criminisi Exemplar (CE) and total variation (TV) based inpainting techniques. Projection images of Catphan and a head phantom were used for the comparison. The SMOG was simulated by erasing the information (filling with “0”) of the areas in each projection corresponding to the grid.

Results:

For the Catphan, the processing time was 178, 45 and 0.98 minutes for CE, TV and our approach, respectively. The signal to noise ratio (SNR) was 19.4, 18.5 and 26.4 db, correspondingly. For the head phantom, the processing time was 222, 45 and 0.93 minutes for CE, TV and our approach, respectively. The SNR was 24.6, 20.2 and 26.2db correspondingly.

Conclusion:

We have developed a simple inpainting based interpolation approach, which can recover some of the image information for the SMOG‐based CBCT imaging.

This study is supported by NIH/NCI grant 1R01CA166948‐01
SU‐E‐I‐09: Application of LiF:Mg,Cu (TLD‐100H) Dosimeters for in Diagnostic Radiology
Authors: Sina S , Zeinali B , Karimipourfard M , Lotfalizadeh F , Sadeghi M , Faghihi R
Published: July 2014

Purpose:

Accurate dosimetery is very essential in diagnostic radiology. The goal of this study is to verify the application of LiF:Mg,Cu,P (TLD100H) in obtaining the Entrance skin dose (ESD) of patients undergoing diagnostic radiology. The results of dosimetry performed by TLD‐100H, were compared with those obtained by TLD100, which is a common dosimeter in diagnostic radiology.

Methods:

In this study the ESD values were measured using two types of Thermoluminescence dosimeters (TLD‐100, and TLD‐100H) for 16 patients undergoing diagnostic radiology (lumbar spine imaging). The ESD values were also obtained by putting the two types of TLDs at the surface of Rando phantom for different imaging techniques and different views (AP, and lateral). The TLD chips were annealed with a standard procedure, and the ECC values for each TLD was obtained by exposing the chips to equal amount of radiation. Each time three TLD chips were covered by thin dark plastic covers, and were put at the surface of the phantom or the patient. The average reading of the three chips was used for obtaining the dose.

Results:

The results show a close agreement between the dose measuered by the two dosimeters.According to the results of this study, the TLD‐100H dosimeters have higher sensitivities (i.e.signal(nc)/dose) than TLD‐100. The ESD values varied between 2.71 mGy and 26.29 mGy with the average of 11.89 mGy for TLD‐100, and between 2.55 mGy and 27.41 mGy with the average of 12.32 mGy for measurements.

Conclusion:

The TLD‐100H dosimeters are suggested as effective dosimeters for dosimetry in low dose fields because of their higher sensitivities.
SU‐E‐I‐27: Establishing Target Exposure Index Values for Computed Radiography
Authors: Murphy N , Tchou P , Belcher K , Scott A
Published: July 2014

Purpose:

To develop a standard set of target exposure index (TEI) values to be applied to Agfa Computed Radiography (CR) readers in accordance with International Electrotechnical Committee 62494‐1 (ed. 1.0).

Methods:

A large data cohort was collected from six USAF Medical Treatment Facilities that exclusively use Agfa CR Readers. Dose monitoring statistics were collected from each reader. The data was analyzed based on anatomic region, view, and processing speed class. The Agfa specific exposure metric, logarithmic mean (LGM), was converted to exposure index (EI) for each data set. The optimum TEI value was determined by minimizing the number of studies that fell outside the acceptable deviation index (DI) range of +/− 2 for phototimed techniques or a range of +/−3 for fixed techniques. An anthropomorphic radiographic phantom was used to corroborate the TEI recommendations. Images were acquired of several anatomic regions and views using standard techniques. The images were then evaluated by two radiologists as either acceptable or unacceptable. The acceptable image with the lowest exposure and EI value was compared to the recommended TEI values using a passing DI range.

Results:

Target EI values were determined for a comprehensive list of anatomic regions and views.

Conclusion:

Target EI values must be established on each CR unit in order to provide a positive feedback system for the technologist. This system will serve as a mechanism to prevent under or overexposures of patients. The TEI recommendations are a first attempt at a large scale process improvement with the goal of setting reasonable and standardized TEI values. The implementation and effectiveness of the recommended TEI values should be monitored and adjustments made as necessary.
SU‐E‐I‐30: Image Analysis in Ultrasonography for Diagnosis of Sjoegren's Syndrome Using Dual‐Tree Complex Wavelet Transform
Authors: Matsui T , Ohki M , Nakamura T , Takagi Y
Published: July 2014

Purpose:

Sjoegren's syndrome (SS) is an autoimmune disease invading mainly salivary and lacrimal glands. Ultrasonography is used for an initial and non‐invasive examination of this disease. However, the ultrasonography diagnosis tends to lack in objectivity and depends on the operator's skills. The purpose of this study is to propose a computer‐aided diagnosis (CAD) system for SS based on a dual‐tree complex wavelet transform (DT‐CWT) and machine learning.

Methods:

The subjects of this study were 174 patients suspected of having SS at Nagasaki University Hospital and examined with ultrasonography of the parotid glands. Out of these patients, 77 patients were diagnosed with SS by sialography. A region of interest (ROI) of 128 × 128 pixels was set within the parotid gland that was indicated by a dental radiologist. The DT‐CWT was applied to the images in the ROI and every image was decomposed into 72 sub‐images of the real and imaginary components in six different resolution levels and six orientations. The statistical features of the sub‐image were calculated and used as data input for the support vector machine (SVM) classifier for the detection of SS. A ten‐fold cross‐validation was employed to verify the

Resultof SVM. The accuracy of diagnosis was compared by a CAD system with a human observer performance. Results:

The sensitivity, specificity, and accuracy in the detection of SS were 95%, 86%, and 91% through our CAD system respectively, while those by a human observer were 84%, 81%, and 83% respectively.

Conclusion:

The proposed computer‐aided diagnosis system for Sjoegren's syndrome in ultrasonography based on dual‐tree complex wavelet transform had a better performance than a human observer.
SU‐E‐I‐33: Initial Evaluation of Model‐Based Iterative CT Reconstruction Using Standard Image Quality Phantoms
Authors: Gingold E , Dave J
Published: July 2014

Purpose:

The purpose of this study was to compare a new model‐based iterative reconstruction with existing reconstruction methods (filtered backprojection and basic iterative reconstruction) using quantitative analysis of standard image quality phantom images.

Methods:

An ACR accreditation phantom (Gammex 464) and a CATPHAN600 phantom were scanned using 3 routine clinical acquisition protocols (adult axial brain, adult abdomen, and pediatric abdomen) on a Philips iCT system. Each scan was acquired using default conditions and 75%, 50% and 25% dose levels. Images were reconstructed using standard filtered backprojection (FBP), conventional iterative reconstruction (iDose4) and a prototype model‐based iterative reconstruction (IMR). Phantom measurements included CT number accuracy, contrast to noise ratio (CNR), modulation transfer function (MTF), low contrast detectability (LCD), and noise power spectrum (NPS).

Results:

The choice of reconstruction method had no effect on CT number accuracy, or MTF (p<0.01). The CNR of a 6 HU contrast target was improved by 1–67% with iDose4 relative to FBP, while IMR improved CNR by 145–367% across all protocols and dose levels. Within each scan protocol, the CNR improvement from IMR vs FBP showed a general trend of greater improvement at lower dose levels. NPS magnitude was greatest for FBP and lowest for IMR. The NPS of the IMR reconstruction showed a pronounced decrease with increasing spatial frequency, consistent with the unusual noise texture seen in IMR images.

Conclusion:

Iterative Model Reconstruction reduces noise and improves contrast‐to‐noise ratio without sacrificing spatial resolution in CT phantom images. This offers the possibility of radiation dose reduction and improved low contrast detectability compared with filtered backprojection or conventional iterative reconstruction.
SU‐E‐I‐40: New Method for Measurement of Task‐Specific, High‐Resolution Detector System Performance
Authors: Loughran B , Singh V , Jain A , Bednarek D , Rudin S
Published: July 2014

Purpose:

Although generalized linear system analytic metrics such as GMTF and GDQE can evaluate performance of the whole imaging system including detector, scatter and focal‐spot, a simplified task‐specific measured metric may help to better compare detector systems.

Methods:

Low quantum‐noise images of a neuro‐vascular stent with a modified ANSI head phantom were obtained from the average of many exposures taken with the high‐resolution Micro‐Angiographic Fluoroscope (MAF) and with a Flat Panel Detector (FPD). The square of the Fourier Transform of each averaged image, equivalent to the measured product of the system GMTF and the object function in spatial‐frequency space, was then divided by the normalized noise power spectra (NNPS) for each respective system to obtain a task‐specific generalized signal‐to‐noise ratio. A generalized measured relative object detectability (GM‐ROD) was obtained by taking the ratio of the integral of the resulting expressions for each detector system to give an overall metric that enables a realistic systems comparison for the given detection task.

Results:

The GM‐ROD provides comparison of relative performance of detector systems from actual measurements of the object function as imaged by those detector systems. This metric includes noise correlations and spatial frequencies relevant to the specific object. Additionally, the integration bounds for the GM‐ROD can be selected to emphasis the higher frequency band of each detector if high‐resolution image details are to be evaluated. Examples of this new metric are discussed with a comparison of the MAF to the FPD for neuro‐vascular interventional imaging.

Conclusion:

The GM‐ROD is a new direct‐measured task‐specific metric that can provide clinically relevant comparison of the relative performance of imaging systems.

Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation
SU‐E‐I‐48: The Behavior of AEC in Scan Regions Outside the Localizer Radiograph FOV: An In Phantom Study of CT Systems From Four Vendors
Authors: Supanich M , Bevins N
Published: July 2014

Purpose:

This review of scanners from 4 major manufacturers examines the clinical impact of performing CT scans that extend into areas of the body that were not acquired in the CT localizer radiograph.

Methods:

Anthropomorphic chest and abdomen phantoms were positioned together on the tables of CT scanners from 4 different vendors. All of the scanners offered an Automatic Exposure Control (AEC) option with both lateral and axial tube current modulation. A localizer radiograph was taken covering the entire extent of both phantoms and then the scanner's Chest‐Abdomen‐Pelvis (CAP) study was performed with the clinical AEC settings employed and the scan and reconstruction range extending from the superior portion of the chest phantom through the inferior portion of the abdomen phantom. A new study was then initiated with a localizer radiograph extending the length of the chest phantom (not covering the abdomen phantom). The same CAP protocol and AEC settings were then used to scan and reconstruct the entire length of both phantoms. Scan parameters at specific locations in the abdomen phantom from both studies were investigated using the information contained in the DICOM metadata of the reconstructed images.

Results:

The AEC systems on all scanners utilized different tube current settings in the abdomen phantom for the scan completed without the full localizer radiograph. The AEC system behavior was also scanner dependent with the default manual tube current, the maximum tube current and the tube current at the last known position observed as outcomes.

Conclusion:

The behavior of the AEC systems of CT scanners in regions not covered by the localizer radiograph is vendor dependent. To ensure optimal image quality and radiation exposure it is important to include the entire planned scan region in the localizer radiograph.
SU‐E‐I‐55: White Matter Fiber Tract Abnormalities by Voxel Wise Correlation Analysis in Neurodegenerative Disease
Authors: Juh R , Suh T
Published: July 2014

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:

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‐E‐I‐59: Image Quality and Dose Measurement for Partial Cone‐Beam CT
Authors: Abouei E , Ford N
Published: July 2014

Purpose:

To characterize performance of cone beam CT (CBCT) used in dentistry investigating quantitatively the image quality and radiation dose during dental CBCT over different settings for partial rotation of the x‐ray tube.

Methods:

Image quality and dose measurements were done on a variable field of view (FOV) dental CBCT (Carestream 9300). X‐ray parameters for clinical settings were adjustable for 2–10 mA, 60–90 kVp, and two optional voxel size values, but time was fixed for each FOV. Image quality was assessed by scanning cylindrical poly‐methyl methacrylate (PMMA) image quality phantom (SEDENTEXCT IQ), and then the images were analyzed using ImageJ to calculate image quality parameters such as noise, uniformity, and contrast to noise ratio (CNR). A protocol proposed by SEDENTEXCT, dose index 1 (DI1), was applied to dose measurements obtained using a thimble ionization chamber and cylindrical PMMA dose index phantom (SEDENTEXCT DI). Dose distributions were obtained using Gafchromic film. The phantoms were positioned in the FOV to imitate a clinical positioning.

Results:

The image noise was 6–12.5% which, when normalized to the difference of mean voxel value of PMMA and air, was comparable between different FOVs. Uniformity was 93.5ߝ99.7% across the images. CNR was 1.7–4.2 and 6.3–14.3 for LDPE and Aluminum, respectively. Dose distributions were symmetric about the rotation angle's bisector. For large and medium FOVs at 4 mA and 80–90 kVp, DI1 values were in the range of 1.26–3.23 mGy. DI1 values were between 1.01–1.93 mGy for small FOV (5×5 cm2) at 4–5 mA and 75–84 kVp.

Conclusion:

Noise decreased by increasing kVp, and the CNR increased for each FOV. When FOV size increased, image noise increased and CNR decreased. DI1 values were increased by increasing tube current (mA), tube voltage (kVp), and/or FOV.

Funding for this project from NSERC Discovery grant, UBC Faculty of Dentistry Research Equipment Grant and UBC Faculty of Dentistry S. Wah Leung Endowment Fund.
SU‐E‐I‐65: The Joint Commission's Requirements for Annual Diagnostic Physics Testing of Nuclear Medicine Equipment, and a Clinically Relevant Methodology for Testing Low‐Contrast Resolution
Authors: West W. Geoffrey , Gray David Clinton
Published: July 2014

Purpose:

To introduce the Joint Commission's requirements for annual diagnostic physics testing of all nuclear medicine equipment, effective 7/1/2014, and to highlight an acceptable methodology for testing lowcontrast resolution of the nuclear medicine imaging system.

Methods:

The Joint Commission's required diagnostic physics evaluations are to be conducted for all of the image types produced clinically by each scanner. Other accrediting bodies, such as the ACR and the IAC, have similar imaging metrics, but do not emphasize testing low‐contrast resolution as it relates clinically. The proposed method for testing low contrast resolution introduces quantitative metrics that are clinically relevant. The acquisition protocol and calculation of contrast levels will utilize a modified version of the protocol defined in AAPM Report #52.

Results:

Using the Rose criterion for lesion detection with a SNRpixel = 4.335 and a CNRlesion = 4, the minimum contrast levels for 25.4 mm and 31.8 mm cold spheres were calculated to be 0.317 and 0.283, respectively. These contrast levels are the minimum threshold that must be attained to guard against false positive lesion detection.

Conclusion:

Low contrast resolution, or detectability, can be properly tested in a manner that is clinically relevant by measuring the contrast level of cold spheres within a Jaszczak phantom using pixel values within ROI's placed in the background and cold sphere regions. The measured contrast levels are then compared to a minimum threshold calculated using the Rose criterion and a CNRlesion = 4. The measured contrast levels must either meet or exceed this minimum threshold to prove acceptable lesion detectability.

This research and development activity was performed by the authors while employed at West Physics Consulting, LLC. It is presented with the consent of West Physics, which has authorized the dissemination of the information and/or techniques described in the work.
SU‐E‐I‐69: How to Appropriately Calculate Effective Dose for CT Using Either SSDE Or DLP
Authors: Brady S , Mirro A , Moore B , Kaufman R
Published: July 2014

Purpose:

To demonstrate how to calculate effective dose (E) using specific dose estimates (SSDE), and to correct the current method using CT dose length product (DLP).

Methods:

The institutional review board waived the need to obtain informed consent for this analysis. Data were analyzed from 352 chest and 241 abdominopelvic CT images (mean age 6.2 years ± 5.1; range 5–55 kg). To calculate E using SSDE, SSDE was first calculated for chest and abdominopelvic regions. 23 individual organ dose values were estimated using the patient's weight and effective diameter to look up a conversion factor that was multiplied by patient SSDE. Organ doses were averaged within patient weight‐based populations, and used to calculate E by the method of weighted summation of organ dose with ICRP 103 tissue weighting factors (E_ICRP). E was calculated using population averaged CT examination DLP for the chest and abdominopelvic region using k‐coefficients published in AAPM Report 96 (E_DLP).

Results:

E_DLP was different by an average of 21% (1.4/1.1) in the chest and 42% (2.4/3.4) in the abdominopelvic region as compared to calculating E_ICRP. K‐coefficients published in AAPM Report 96 did not account for pitch factor other than unity, were derived using a 32 cm diameter CTDI phantom only, and used ICRP 60 tissue weighting factors. Once corrected for pitch factor, the appropriate size of CTDI phantom, and ICRP 103 tissue weighting factors, E_DLP improved in agreement with E_ICRP to better than 7% (1.4/1.3) and 4% (2.4/2.5) for the chest and abdominopelvic regions, respectively.

Conclusion:

Current use of DLP to calculate E was shown to be deficient when compared to the method using ICRP tissue weighting factors due to the outdated means by which the k‐coefficients were derived. This study demonstrates a means to calculate E_ICRP using patient SSDE and how to appropriately correct E_DLP.
SU‐E‐I‐77: A Noise Reduction Technique for Energy‐Resolved Photon‐Counting Detectors
Authors: Lam Ng A , Ding H , Cho H , Molloi S
Published: July 2014

Purpose:

Finding the optimal energy threshold setting for an energy‐resolved photon‐counting detector has an important impact on the maximization of contrast‐to‐noise‐ratio (CNR). We introduce a noise reduction method to enhance CNR by reducing the noise in each energy bin without altering the average gray levels in the projection and image domains.

Methods:

We simulated a four bin energy‐resolved photon‐counting detector based on Si with a 10 mm depth of interaction. TASMIP algorithm was used to simulate a spectrum of 65 kVp with 2.7 mm Al filter. A 13 mm PMMA phantom with hydroxyapatite and iodine at different concentrations (100, 200 and 300 mg/ml for HA, and 2, 4, and 8 mg/ml for Iodine) was used. Projection‐based and Image‐based energy weighting methods were used to generate weighted images. A reference low noise image was used for noise reduction purposes. A Gaussian‐like weighting function which computes the similarity between pixels of interest was calculated from the reference image and implemented on a pixel by pixel basis for the noisy images.

Results:

CNR improvement compared to different methods (Charge‐Integrated, Photon‐Counting and Energy‐Weighting) and after noise reduction was highly task‐dependent. The CNR improvement with respect to the Charge‐Integrated CNR for hydroxyapatite and iodine were 1.8 and 1.5, respectively. In each of the energy bins, the noise was reduced by approximately factor of two without altering their respective average gray levels.

Conclusion:

The proposed noise reduction technique for energy‐resolved photon‐counting detectors can significantly reduce image noise. This technique can be used as a compliment to the current energy‐weighting methods in CNR optimization.
SU‐E‐I‐82: Improving CT Image Quality for Radiation Therapy Using Iterative Reconstruction Algorithms and Slightly Increasing Imaging Doses
Authors: Noid G , Chen G , Tai A , Li X
Published: July 2014

Purpose:

Iterative reconstruction (IR) algorithms are developed to improve CT image quality (IQ) by reducing noise without diminishing spatial resolution or contrast. For CT in radiation therapy (RT), slightly increasing imaging dose to improve IQ may be justified if it can substantially enhance structure delineation. The purpose of this study is to investigate and to quantify the IQ enhancement as a result of increasing imaging doses and using IR algorithms.

Methods:

CT images were acquired for phantoms, built to evaluate IQ metrics including spatial resolution, contrast and noise, with a variety of imaging protocols using a CT scanner (Definition AS Open, Siemens) installed inside a Linac room. Representative patients were scanned once the protocols were optimized. Both phantom and patient scans were reconstructed using the Sinogram Affirmed Iterative Reconstruction (SAFIRE) and the Filtered Back Projection (FBP) methods. IQ metrics of the obtained CTs were compared.

Results:

IR techniques are demonstrated to preserve spatial resolution as measured by the point spread function and reduce noise in comparison to traditional FBP. Driven by the reduction in noise, the contrast to noise ratio is doubled by adopting the highest SAFIRE strength. As expected, increasing imaging dose reduces noise for both SAFIRE and FBP reconstructions. The contrast to noise increases from 3 to 5 by increasing the dose by a factor of 4. Similar IQ improvement was observed on the CTs for selected patients with pancreas and prostrate cancers.

Conclusion:

The IR techniques produce a measurable enhancement to CT IQ by reducing the noise. Increasing imaging dose further reduces noise independent of the IR techniques. The improved CT enables more accurate delineation of tumors and/or organs at risk during RT planning and delivery guidance.
SU‐E‐I‐85: Exploring the 18F‐Fluorodeoxyglucose PET Characteristics in Staging of Esophageal Squamous Cell Carcinoma
Authors: Ma C , Yin Y
Published: July 2014

Purpose:

The aim of this study was to explore the characteristics derived from 18F‐fluorodeoxyglucose (18F‐FDG) PET image and assess its capacity in staging of esophageal squamous cell carcinoma (ESCC).

Methods:

26 patients with newly diagnosed ESCC who underwent 18F‐FDG PET scan were included in this study. Different image‐derived indices including the standardized uptake value (SUV), gross tumor length, texture features and shape feature were considered. Taken the histopathologic examination as the gold standard, the extracted capacities of indices in staging of ESCC were assessed by Kruskal‐Wallis test and Mann‐Whitney test. Specificity and sensitivity for each of the studied parameters were derived using receiver‐operating characteristic curves.

Results:

18F‐FDG SUVmax and SUVmean showed statistically significant capability in AJCC and TNM stages. Texture features such as ENT and CORR were significant factors for N stages(p=0.040, p=0.029). Both FDG PET Longitudinal length and shape feature Eccentricity (EC) (p≤0.010) provided powerful stratification in the primary ESCC AJCC and TNM stages than SUV and texture features. Receiver‐operating‐characteristic curve analysis showed that tumor textural analysis can capabilty M stages with higher sensitivity than SUV measurement but lower in T and N stages.

Conclusion:

The 18F‐FDG image‐derived characteristics of SUV, textural features and shape feature allow for good stratification AJCC and TNM stage in ESCC patients.
SU‐E‐I‐95: Personalized Radiography Technical Parameters for Each Patient and Exam
Authors: Soares F , Camozzato T , Kahl G , Soares A , Zottis A
Published: July 2014

Purpose:

To determine exact electrical parameters (kV, mAs) a radiological technologist shall use taking account the exam and patient's structure, with guarantee of minimum dose and adequate quality image.

Methods:

A patient's absorbed dose equation was developed by means of Entrance Skin Dose (ESD), irradiated area and patient width for specific anatomy. ESD is calculated from a developed equation, where entrance surface air‐KERMA and backscatter factor are included, with air‐to‐skin coefficient conversion. We developed specific Lambert‐Beer attenuation equations derived from mass energy‐absorption coefficients data for skin, fat, and muscle and bone as one tissue. Anatomy tissue thickness distribution at central X‐ray location in anteroposterior incidence for hand and chest, was estimate by discounting constant skin and bone thickness from patient measured width, assuming the result as muscle and fat. A clinical research at a big hospital were executed when real parameters (kV, mAs, filtration, ripple) used by technologists were combined with the image quality and patient's data: anatomy width, height and weight. A correlation among the best images acquired and electrical parameters used were confronted with patient's data and dose estimation. The best combinations were used as gold standards.

Results:

For each anatomy, two equations were developed to calculate voltage (kV) and exposure (mAs) to reproduce and interpolate the gold standards. Patient is measured and data are input into equations, giving radiological technologists the right set of electrical parameters for that specific exam.

Conclusion:

This work indicates that radiological technologist can personalize the exact electrical parameters for each patient exam, instead of using standard values. It also guarantee that patients under or over‐sized measures will receive the right dose for the best image. It will stop wrong empiric adjusts technologists do when examining a non‐standard patient and reduce probability of radiography retaken because of over or under exposition.
SU‐E‐I‐100: Heterogeneity Studying for Primary and Lymphoma Tumors by Using Multi‐Scale Image Texture Analysis with PET‐CT Images
Authors: Li Dengwang , Wang Qinfen , Li H , Chen J
Published: July 2014

Purpose:

The purpose of this research is studying tumor heterogeneity of the primary and lymphoma by using multi‐scale texture analysis with PET‐CT images, where the tumor heterogeneity is expressed by texture features.

Methods:

Datasets were collected from 12 lung cancer patients, and both of primary and lymphoma tumors were detected with all these patients. All patients underwent whole‐body 18F‐FDG PET/CT scan before treatment. The regions of interest (ROI) of primary and lymphoma tumor were contoured by experienced clinical doctors. Then the ROI of primary and lymphoma tumor is extracted automatically by using Matlab software. According to the geometry size of contour structure, the images of tumor are decomposed by multi‐scale method.Wavelet transform was performed on ROI structures within images by L layers sampling, and then wavelet sub‐bands which have the same size of the original image are obtained. The number of sub‐bands is 3L+1. The gray level co‐occurrence matrix (GLCM) is calculated within different sub‐bands, thenenergy, inertia, correlation and gray in‐homogeneity were extracted from GLCM.Finally, heterogeneity statistical analysis was studied for primary and lymphoma tumor using the texture features.

Results:

Energy, inertia, correlation and gray in‐homogeneity are calculated with our experiments for heterogeneity statistical analysis.Energy for primary and lymphomatumor is equal with the same patient, while gray in‐homogeneity and inertia of primaryare 2.59595±0.00855, 0.6439±0.0007 respectively. Gray in‐homogeneity and inertia of lymphoma are 2.60115±0.00635, 0.64435±0.00055 respectively. The experiments showed that the volume of lymphoma is smaller than primary tumor, but thegray in‐homogeneity and inertia were higher than primary tumor with the same patient, and the correlation with lymphoma tumors is zero, while the correlation with primary tumor isslightly strong.

Conclusion:

This studying showed that there were effective heterogeneity differences between primary and lymphoma tumor by multi‐scale image texture analysis.

This work is supported by National Natural Science Foundation of China (No. 61201441), Research Fund for Excellent Young and Middle‐aged Scientists of Shandong Province (No. BS2012DX038), Project of Shandong Province Higher Educational Science and Technology Program (No. J12LN23), Jinan youth science and technology star (No.20120109)