bluuebunny/crossref_metadata_2025 huggingface dataset:
High molecular weight form of adiponectin levels of Japanese patients with chronic hepatitis C virus infection
Authors: Furusyo Norihiro , Sawayama Yasunori , Maeda Shinji , Toyoda Kazuhiro , Takeoka Hiroaki , Murata Masayuki , Ohnishi Hachiro , Hayashi Jun
Published: July 2007

Aim:  The aim of the present study was to clarify the correlation between serum adiponectin level and the properties of hepatitis C virus (HCV).

Methods:  A meal test was carried out for insulin resistance assessment in 81 patients with chronic HCV infection. Blood samples were taken before and after the test to measure serum insulin and plasma glucose (PG). The adiponectin level was measured by enzyme‐linked immunosorbent assay in each patient.

Results:  Serum adiponectin levels were significantly correlated with the area under the insulin curve (AUC‐insulin)during the meal test and with serum HCV‐RNA level. Multiple regression analysis showed age to be a significant independent parameter associated with an increased adiponectin level, whereas male sex, fasting insulin, and serum HCV‐RNA level were significant independent parameters associated with a decreased adiponectin level.

Conclusion:  It is possible that insulin resistance in patients with chronic HCV infection is related to adiponectin secretion.
Evaluation of GAFCHROMIC® EBT film for CyberKnife® dosimetry
Authors: Wilcox Ellen E. , Daskalov George M.
Published: July 2007

External beam therapy (EBT) GAFCHROMIC® film is evaluated for dosimetry and characterization of the CyberKnife® radiation beams. Percentage depth doses, lateral beam profiles, and output factors are measured in solid water using EBT GAFCHROMIC® film (International Specialty Products, Wayne, NJ) for the radiation beams of diameter produced by the CyberKnife® (Accuray, Sunnyvale, CA). The data are compared to those measured with the PTW 60008 diode and the Wellhofer CC01 ion chamber in water. For the small radiation field sizes used in stereotactic radiosurgery, lateral electronic disequilibrium and steep dose gradients exist in a large portion of these fields, requiring the use of high‐resolution measurement techniques. For small beams, the detector size approaches the dimensions of the beam and adversely affects measurement accuracy in regions where the gradient varies across the detector. When film is the detector, the scanning system is usually the resolution‐limiting component. Radiographic films based upon silver halide (AgH) emulsions are widely used for relative dosimetry of external radiation treatment beams in the megavoltage energy range, because of their good spatial resolution and capability to provide integrated dosimetry over two dimensions. Film dosimetry, however, has drawbacks due to its steep energy dependence at low photon energies as well as film processor and densitometer artifacts. EBT radiochromic film, introduced in 2004 specifically for IMRT dosimetry, may be a detector of choice for the characterization of small radiosurgical beams, because of its near‐tissue equivalence, radiation beam energy independence, high spatial resolution, and self developing properties. For radiation beam sizes greater than , the film measurements were identical to those of the diode and ion chamber. For the smaller beam diameters of 7.5 and , however, there were differences in the data measured with the different detectors, which are attributed to their different spatial resolution and non‐water‐equivalence.
Inverse‐geometry volumetric CT system with multiple detector arrays for wide field‐of‐view imaging
Authors: Mazin Samuel R. , Star‐Lack Josh , Bennett N. Robert , Pelc Norbert J.
Published: July 2007

Current volumetric computed tomography (CT) methods require seconds to acquire a thick volume with high resolution. Inverse‐geometry CT (IGCT) is a new system geometry under investigation that is anticipated to be able to image a thick volume in a single gantry rotation with isotropic resolution and no cone‐beam artifacts. IGCT employs a large array of source spots opposite a smaller detector array. The in‐plane field of view (FOV) is primarily determined by the size of the source array, in much the same way that the FOV is determined by the size of the detector array in a conventional CT system. Thus, the size of the source array can be a limitation on the achievable FOV. We propose adding additional detector arrays, spaced apart laterally, to increase the in‐plane FOV while still using a modestly sized source array. We determine optimal detector placement to maximize the FOV while obtaining relatively uniform sampling. We also demonstrate low wasted radiation of the proposed system through design and simulation of a pre‐patient collimator. Reconstructions from simulated projection data show no artifacts when combining the data from the detector arrays. Finally, to demonstrate feasibility of the concept, an anthropomorphic thorax phantom containing a porcine heart was scanned on a prototype table‐top system. The reconstructed axial images demonstrate a in‐plane FOV using a source array.
SU‐BB‐BRB‐03: Learning a Foreign Language: Scientists and Media Relations
Authors: Classic K
Published: July 2007

It seems that each scientific specialty has its own language. Talk to a computer person and you're not sure whether you need to just reboot the system or toss it out completely. Talk to a medical doctor and you're not sure if you really have to exercise or if you can get over it with a pill. So, a physicist and the public? Is it no wonder there is a communication gap when, as scientists, we even find it hard to communicate with and understand other science‐types?

What are some basic tips we can use to be better communicators — with other scientists and the public? There are tips that can be offered:

• Using common analogies (e.g. alpha = linebacker, beta = running back, gamma = wide receiver).

• Emphasizing that radiation is beneficial.

• Listening and asking questions (e.g. Why do you think that?)

• Using of language that is not trying to convince, but is instead to simply inform.

• Not getting into physics 101.

• Keeping it short unless additional questions are asked.

• Never lying or going “off the record”.

• Being professional.

• Using visuals whenever possible.

• Using whole numbers.

A lot, though, falls into experience. This talk will cover some of the listed tips and also discuss lessons learned.
SU‐FF‐I‐21: An Empirical Method for Lag Correction in Cone‐Beam CT
Authors: Mail N , Moseley D , Siewerdsen J , Jaffray D
Published: July 2007

Purpose: Image lag degrades image quality in cone‐beam CT (CBCT), resulting in contrast reduction, lack of CT number accuracy and uniformity, and skin‐line artifacts. This work investigates the magnitude of such degradation and demonstrates a lag correction method based on measured data from a system for CBCT guidance of radiotherapy (Elekta Synergy XVI). Method and Materials: Image lag and its relationship with various parameters including signal strength, photon energy and frame number was investigated for a PerkinElmer (RID1640) flat‐panel imager. An empirical lag correction based on measurements of image lag was developed to manage lag artifacts. The CatPhan phantom within an irregular body annulus was used to demonstrate the magnitude of artifacts before and after correction. Each projection was corrected for lag effects by subtracting previous projections weighted by the magnitude of image lag. The subtraction of previous projections was limited up to 51 frames due to uncorrelated noise. The reconstructed images before and after correction were analyzed for skin‐line and radar type artifacts, CT♯ accuracy, uniformity and contrast of several inserts. Reconstructed images were transformed into polar coordinates for analysis. Results: Experimental results illustrate that the first frame lag of the imager is less than 2.3%, and is independent of the kVp value (70–120 kV) and pixel saturation (20–80%). Lag correction improves the skin‐line artifact and reduces radar artifact by 40%. Contrast enhances by 20% and improves the CT♯ accuracy for water by 2.5%. It improves water uniformity by 5% compared to the nominal images. Conclusion: Lag artifacts can be reduced by correction of the projection images. Lag correction is most important for high contrast and irregularly shaped objects. For a circularly shaped object, lag correction does not improve the skin‐line artifact but can be useful for soft‐tissue visibility adjacent to bony anatomy.

This research is sponsored by Elekta.
SU‐FF‐I‐25: Feasibility of Estimating Multidetector CT Dose Using BEAMnrc Code
Authors: Chiang‐Hsieh C C , Tsai Hui‐Yu , Tung C J
Published: July 2007

Purpose: Most of Monte Carlo based methods estimating radiation dose in computed tomography (CT) were performed using MCNP or EGS codes. The BEAMnrc code, one of Monte Carlo codes, was usually used to simulate radiation therapy accelerators, and has fine graphic interfaces and various component modules. The purpose of this work was to verify the feasibility of using BEAMnrc code to estimate radiation dose in a multidetector CT (MDCT) scanner. Method and Materials: A Siemens Somatom Sensation 64 MDCT scanner system was used in our simulations to achieve the study objective. Detailed MDCT inner structures were constructed by component modules in the BEAMnrc code to describe the x‐ray tube, filtrations, bowtie filter, collimators and geometry factors. Further more, a pencil‐type ionization chamber and a batch of TLDs were used to measure the lateral dose distribution. The beam quality, referred to half value layer (HVL), was measured with the chamber and high‐purity aluminum sheets. Results: The simulated x‐ray spectra has been compared with those in Xcom5 calculations and they agree with each other. Comparisons between experimental measurements for the lateral in‐air dose profile and half value layer measures, and the absolute dose values derived from the Monte Carlo simulations for the body filter demonstrate agreements with 0.6%. Conclusion: This work illustrates the feasibility to extend the BEAMnrc code for modeling from radiotherapy sources to CT sources. Future work will be extended to estimate doses within voxelized patient models using DOSXYZnrc.
SU‐FF‐I‐39: Development of Clinical Application Platform Using Digital Tomosynthesis for Target Localization
Authors: Yan H , Ren L , Godfrey D , Yin F
Published: July 2007

Purpose: To develop a workstation for clinical application of digital tomosynthesis (DTS) for real‐time target localization. Specifically, to accelerate the reconstruction both digitally‐reconstructed radiograph (DRR) and DTS using ultra‐fast interpolation capability of graphics hardware. Method and Materials: The developed workstation for real‐time target localization using DTS technology includes image acquisition, image reconstruction, and image comparison. A critical step to implement this technology is its reconstruction speed, especially real‐time generation of reference DTSs which require DRRs. The new generation graphics hardware provides a fast implementation of image interpolation and allows the bi‐linear/tri‐linear interpolation and the other image operations to be accomplished within second. We implemented classical ray‐casting algorithm for 2D DRR and filtered back‐projection (FBP) algorithm for DTS reconstruction on graphics hardware based on OpenGL programming interface. Specifically, planning CT images and on‐board projection images were loaded into the memory of hardware and saved as textures which were projected onto frame‐buffer according to the given geometry of imaging system. The final images were generated by blending multiple textures projected onto the frame‐buffer. Difference images and correlation coefficients between hardware and software DRRs and DTSs were calculated to assess their similarity. Results: The mean errors and their standard deviations of the differences DRR and DTS images are 1.0% ± 1.5% and 1.2% ± 2.1%. The correlation coefficients are 99.9% for DRRs and 99.5% for DTS. The reconstructed efficiency was improved by a factor of 67 for DRR and 13 for DTS. Conclusions: The hardware method provides fast reconstructions of DRR and DTS with visibility of anatomical structures comparable to those generated using software methods.

This allows real‐time target localization for image registration between on‐board and reference DTSs in the application platform.
SU‐FF‐I‐48: Normalized Conceptus Doses for Multi‐Detector CT Examinations : A Monte Carlo Study
Authors: Damilakis J , Tzedakis A , Perisinakis K , Gourtsoyiannis N
Published: July 2007

Purpose: To provide normalized conceptus dose data for the estimation of the conceptus dose from examinations performed using a 16‐slice CT scanner. Method and Materials: The Monte Carlo N‐Particle (MCNP) radiation transport code was employed in this study to model the Siemens Sensation 16 CT scanner. Four mathematical phantoms were used simulating women at 0, 3, 6 and 9 months of gestation. The contribution to the conceptus dose from a single scan was measured at various positions across the phantom. To verify MCNP results, conceptus dose measurements were carried out by means of (a) three physical anthropomorphic phantoms simulating pregnancy at 0, 3 and 6 months of gestation and (b) thermoluminescence dosimetry. The scans were carried out using a Siemens Sensation 16 scanner. Results: The results consist of normalized conceptus dose coefficients for single slices of 2 cm width across the 4 mathematical phantoms. These coefficients were defined as the conceptus dose contribution from a single slice divided by the CTDI free‐in‐air measured with identical scanning parameters. Normalized conceptus dose data were calculated for (a) 120 kV and 140 kV and (b) 12 mm and 24 mm beam collimation. The mean conceptus dose can be calculated using the following formula:
urn:x-wiley:00942405:media:mp0425:mp0425-math-0001 where Dc is the dose to the conceptus, CTDIF is the CTDI free‐in‐air, BC is the beam collimation in mm, fz the normalized conceptus dose coefficients and z1, z2 the boundaries of the scanned volume. Taking into account phantom differences, there was a good agreement between the results of the TLD measurements and the mathematical simulation. Conclusion: Accurate estimation of conceptus doses from MDCT examinations performed using a multi‐detector scanner can be made using the dose data provided in this study.
SU‐FF‐I‐51: Effect of Subcutaneous Fat On Abdominal CT Dosimetry: Monte Carlo Study
Authors: Lee C , Lee C , Lodwick D , Bolch W
Published: July 2007

Purpose: To investigate the effect of abdominal subcutaneous fat on organ and effective doses in abdominal computed tomography (CT) examination by using deformable hybrid anthropomorphic phantoms and MCNPX2.5. Methods and Material: A hybrid anthropomorphic computational phantom representing a newborn reference patient was employed in this study to illustrate use of deformable phantoms for patient‐specific dosimetry. The hybrid phantom is currently the most advanced computational phantom incorporating the best features of conventional stylized and voxel phantoms, which include parameter‐based flexibility and improved anatomical realism, respectively. Based on the template phantom of which the abdominal circumference was 36 cm, two more phantoms having abdominal circumferences of 33 and 39 cm were generated by manipulating control points on the abdominal surfaces. Three phantoms were then incorporated into MCNPX2.5 code where helical fan beams from SOMATOM Sensation 16 helical multi‐slice CT scanner were modeled. A CT collimator setting of 12 mm and a tube potential of 100 kVp, both commonly used in pediatric CT scans, were simulated for illustrative calculations. Absorbed doses for major organ doses were calculated in each of the three newborn phantoms. The normalized organ absorbed doses for a total of 9 major organs were calculated and compared to each other. Results: As waist circumference increases, the thickness of abdominal subcutaneous fat increases correspondingly which causes a decrease in the organ absorbed dose for CT beams, especially, for the small intestinal wall (−5.8%) and kidney (−7.3%). Conclusion: Even though the effect of fat thickness on organ dose was not significant in newborn phantom, higher correlation would be observed in older and larger phantoms. The authors are working on a series of pediatric phantoms so that a more systematic investigation on the effect of abdominal subcutaneous fat on CT dosimetry could be performed in the future.
SU‐FF‐I‐52: Comparison of CR QC Phantoms: The Kodak TQT Program Versus a General Purpose Phantom Program
Authors: Arbique G , Anderson J , Gallet J , Guild J , Lane T
Published: July 2007

Purpose: Recently, the American Association of Physicists in Medicine (AAPM) issued two Task Group reports (AAPM Reports 74 and 93) covering acceptance testing and QA for CR systems. An important component of CR QA programs is routine testing of system performance by the technologist. Testing should be simple to perform, be easy to evaluate, and probe most facets of system operation. To this end a quality control phantom for routine testing is recommended. CR QA phantoms can be vendor‐specific, or general purpose for cross‐platform use. We compare our clinical experience with both types of phantom and discuss their relative merits. Method and Materials: The optional Kodak Total Quality Tool (TQT), and associated analysis software, is designed for acceptance testing and routine QA of the Kodak DirectView CR system. Our institution has used the TQT for more than two years. The Fluke EZ CR/DR “DIN” test tool (DTT) is a general purpose phantom incorporating a standard test pattern. The DTT, with an in‐house analysis package, has been used with our Fuji CR systems for over four years. Results: Both phantoms measure parameters recommended by the AAPM reports. A detailed comparison of measurement capabilities including spatial resolution and linearity, exposure linearity and calibration, low contrast resolution, uniformity, and noise and artifact evaluation is presented. The documentation and integrated analysis features of the Kodak QA program led to easy implementation and management. The DTT analysis used standard imaging tools and subjective measures. While the DTT is useful for cross‐platform comparisons, the TQT appears to be more sensitive in detecting potential equipment problems. Conclusion: Advantages of the TQT program include: tests specific to the reading mechanism, an integrated user interface, and acceptance and understanding by service personnel. The non‐proprietary DTT is useful for comparing different systems using a set of standardized measures.
SU‐FF‐I‐55: A CT Daily Quality Assurance On‐Couch Procedure and Phantom in Radiation Oncology
Authors: Liu R , Prado K , Wu R , Balter P
Published: July 2007

Purpose: To design a simple yet comprehensive daily quality assurance (QA) program and phantom for CT Simulators in Radiation Oncology so that positioning laser and imaging QA can be performed on the flat couch using only one tool. This has been done to avoid removing the flat couch to perform CT QA and to simplify the daily QA procedure. Method and Materials: A new daily QA phantom was constructed by attaching to a commercially available CT QA phantom 3 adjustable legs and two metric scales in both vertical and horizontal directions. The two metric scales are used for laser QA, while the phantom body is used for CT imaging QA. Since the couch is scanned with the phantom, its effect on image quality was evaluated. The phantom is positioned on the couch such that couch effects are minimized. Four different GE CT scanners and 3 different Philips scanners were used to evaluate this phantom. Daily testing includes high and low contrast resolution, scale accuracy, CT number accuracy and uniformity. Results: The proposed program has been piloted in our institution. Inclusion of the couch produces different yet reproducible effects on image quality. The effects appear to be couch and scanner specific and are incorporated in the acceptability criteria for each CT scanner. Based on our data thus far, the presence of the couch does not change image resolution visually. It appears, however, that the couch causes changes in the uniformity of water's CT number. The effects are greatest in the section of the phantom closest to the couch. We thus limit our image quality evaluation to the central and 12 O'clock positions of the phantom. Conclusions: The proposed program and phantom has allowed us to implement a more comprehensive QA program while decreasing the level of effort by the simulation therapists.
SU‐FF‐I‐56: A Treatment Planning System (TPS) Independent Software for 4DCT Image Analysis
Authors: Samant S , Huang M , Xia J , Frouhar V , Palta J
Published: July 2007

Purpose: To present standalone software that allows for transfer of treatment planning data from a treatment planning system (TPS) in DICOM‐RT format to any user‐defined image analysis platform. With this, several treatment planning tools have been developed outside of TPS for 4DCT analysis. Materials and method: Treatment planning systems have been primarily viewed as dose calculation engines, and only recently have begun introducing rudimentary tools dealing with 4DCT and deformable image registration. Concurrently, there has been a proliferation of imaging software, either in public domain or user‐written, for the new imaging paradigm offered by 4DCT to study organ deformation. There is a disconnect between available treatment planning tools and the state‐of‐art in image processing. While DICOM‐RT standard allows, in theory, for a straightforward transfer of treatment planning data, the clinical experience is generally anything but this. Thus most radiotherapy clinics, without benefit of dedicated programming and imaging science teams and yet treating the majority of patients, are unable to realize the full potential offered by 4DCT or contribute valuable clinical experience. Using a simplified DICOM‐RT export from TPS, we developed several treatment planning tools for enhanced visualization and image analysis of 4DCT data. Results: Various tools for processing 4DCT data were developed: 1) autosegmentation of normal structures onto phased CTs using a reference 3D CT containing initial manual segmentations; 2) automatic generation of internal target volume (ITV); 3) target motion characterization using center‐of‐mass trajectories; 4) dose volume histograms based either on maximal target motion, or probability density function; and 5) visualization for studying goodness of registration. Conclusion: Image analysis tools, which supplement available image visualization using software from CERR (Washington University, St. Louis) and RCET (University of Florida), for 4DCT were presented. This approach allows for rapid development and clinical implementation of state‐of‐art image analysis tools in treatment planning.
SU‐FF‐I‐57: A PET Head and Neck Tumor Delineation Approach Based On Mumford‐Shah Active Contours
Authors: Li H , Thorstad W , Biehl K , Laforest R , Su Y , Shoghi K , Donnelly E , Low D , Lu W
Published: July 2007

Purpose: Existing methods to segment the tumor boundary using PET images have focused on intensity thresholding, which suffers from ambiguity with respect to the threshold selection. In this paper, we present a novel, semi‐automatic method for PET head & neck tumor delineation utilizing an energy minimization method—Mumford‐shah active contours. Method and Materials: Mumford‐shah method is a region‐based active contour model which enjoys a number of attractive properties, such as greater robustness to noise than most edge‐based approaches, and flexible initial contour placement. The proposed process begins when an experienced radiation oncologist manually draws a small initial curve (or surface) inside the desired tumor. Then the Mumford‐shah active contour model is utilized to expend this initialization to reach an equilibrium state and form the final tumor boundary. In this model, the region‐based information is for guiding the energy minimization process. The entire process is adaptive to each tumor and independent of the manual drawn initializations. Results: We applied this method to a set of simulated, phantom, and clinical PET images. For simulated and phantom images, the results were quantitatively compared with the known sphere sizes. The results show that our method is reasonably robust with errors less than 2.0 mm in the diameter and volume overlap metric higher than 90.0% between the detected volumes and the actual volumes. The results on clinical PET images were deemed reasonably accurate through visual appraisal by an experienced head‐and‐neck radiation oncologist. Conclusion: An energy minimization method based on Mumford‐shah active contours is applied to adaptive, reproducible, and accurate tumor delineation in PET. Experimental results on simulated, phantom, and clinical PET images demonstrate the robustness, accuracy, reproducibility, and its potential usefulness in clinical radiation therapy planning.
SU‐FF‐I‐61: Auto‐Recontouring of CBCT Images for Adaptive Therapy
Authors: Chao M , Xing L
Published: July 2007

Purpose: Organ delineation on CBCT is an indispensable step in using CBCT data to adaptively modify treatment plan online or offline. With the goal of automating the process, we develop a method to map the existing contours from a patient's treatment plan to his/her CBCT images. Methods: Two head‐and‐neck and two prostate patients were selected. For each case, 3∼5 on‐treatment CBCTs were acquired during the course of radiotherapy. The organs were manually segmented on the planning CT for treatment planning. A narrow shell of width ∼1cm was created to encompass the contour surface. The shell captures the image features of the neighborhood of the contours and acts as a “signature” of the surface in searching for its best correspondence in CBCT. Deformation of the shell is permissible and is modeled by a spline algorithm. The shell was first mapped rigidly from CT to CBCT, followed by an adjustment of shell shape to adapt any anatomy change. The influence of CBCT reconstruction artifacts on the accuracy and reliability of the proposed algorithm was also studied. Results: Despite that CBCT is noisier and often contains reconstruction artifacts, contour mapping calculations for a total of 16 sets CBCTs showed no single failure, as judged by an inaccuracy anywhere on the boundary larger than 3mm. For the head‐and‐neck patients, high fidelity mapping is achievable with a rigid mapping of the shells. Other than the femoral heads, deformable adjustments of the contours after rigid mapping are found to be necessary for the prostate cases. Noteworthy, the algorithm performs well even in the presence of an unusually large shape change of the bladder in one of the treatment sessions. Conclusions: A contour mapping technique has been developed for CBCT image segmentation. The method provides a useful tool for future adaptive radiation therapy.
SU‐FF‐I‐63: Temporal Constrained Registration of Arbitrary Surface Contours for Use in 4D Radiation Therapy
Authors: Jacques R , Glaunès J , Ford E , McNutt T , Taylor R , Wong J
Published: July 2007

Purpose: To quantify the validity of the temporal interpolation provided by a nonlinear uncorrelated contour based path length minimizing deformable registration algorithm in 4D radiation therapy. Method and Materials: The anatomical surfaces are represented as triangulated meshes. The registration algorithm is implemented by defining a norm between the triangulated meshes, based on the algorithms of Glaunès and Vaillant. This algorithm matches two surfaces as opposed to image intensities or specific points. Additionally, it optimizes the path between them allowing for a temporal interpolation. The registration is defined as the flow of an unlabeled 3D point set to an arbitrary target surface that minimizes both the norm between the target and registered surface and the non‐linear path length between the source and registered surface. Ground truth surfaces were generated from 4D lung datasets using the semi‐automatic mesh segmentation routine from a research version of Pinnacle, with expert manual correction. Results: To test this algorithm we compared its ability to interpolate intermediate shapes with a standard linear interpolation technique. We found that this algorithm performs comparably.

The similarity metric used was an Euclidean distance error metric between the ground truth surface and a surface interpolated between a previous and subsequent ground truth surface. It was calculated between the interpolated and truth vertexes and their closest points on the truth and interpolated surfaces, respectively. This metric is independent of the interpolation and surface triangulation used, and thus is applicable to other interpolation algorithms. Conclusion: This work shows that this general, path length minimizing deformable registration algorithm based interpolation performs similarly to linear interpolation in approximately correlated, intrafractional datasets. This algorithm has the advantage of utilizing surfaces with arbitrary triangulations without point correspondences. We further discovered that this specific algorithm exhibited numerical instabilities that require further investigation.
SU‐FF‐I‐64: Breast Image Registration Using SIFT and TPS Hybrid Method
Authors: Xie Y , Faranesh T , Daniel B , Xing L
Published: July 2007

Purpose/Objectives(s): Breast images compose of soft tissues with low contrast in MRI imaging modality. However, even small amounts of motion can have large effects on clinical analysis, since each individual pixel needs to be careful checked. We investigate a strategy to obtain high precision deformable registration method for breast images. Materials: The data set contains 3 series. Each series contains 32 slices, with adifferent number of time points. Series 1 contains 15 time points (15×32 = 480 images), Series 2 contains 20 time points (20×32 = 640 images), and Series 3 contains 20 time points (20×32 = 640 images). Some potential complicating factors are: 1) In Series 1, the MRI flip angle is different for time points 1–5, 6–10, and 11–15, which causes each set of 5 time points to potentially have different contrast. 2) Contrast agent is administered in series 2, so the contrast changes over time. 3) There is a space of a few minutes between each series, when the patient may move. 4) Series 3 is a “wash‐out” series. As the contrast agent washes out, the image contrast may change. Methods: Our calculation consists of two natural steps. First, a number of control points are auto‐searched based on tissue intensity information. Control points in fixed image and moving image are matched together using SIFT (Scale Invariance Feature Transformation) method. In the second stage, the matched control points serve as a priori information for the TPS (Thin Plate Spline) deformable registration calculation. Results: Breast images are matched well using this hybrid registration method. The subtraction images are presented to show the registration results. Conclusions: The proposed method can be used in the soft tissue images and large deformation images. Comparison to the conventional deformable registration, this method can effectively increase the local registration quality.
SU‐FF‐I‐68: Evaluation of An Intensity‐Based Free‐Form Deformable Registration Algorithm
Authors: Piper J
Published: July 2007

Purpose: To propose and evaluate an intensity‐based free‐form deformable registration algorithm for CT image volumes. Method and Materials: We have developed an intensity‐based deformable registration algorithm with essentially limitless degrees of freedom depending on required accuracy and execution speed. The algorithm utilizes sufficient regularization to minimize the likelihood of folds or tears in the deformation fields. The first evaluation strategy utilized real CT volume pairs acquired weeks apart for three subjects who exhibited significant weight loss during IMRT treatment. For these subjects, we calculated the correlation coefficient after rigid and deformable registration. Additionally, a known deformation was applied to a real CT volume creating a synthetic target to determine the ability of the algorithm to recover the same “gold standard” deformation. Finally, we measured the consistency of the algorithm as the average distance of concatenated forward and reverse deformations from the unity transform on a real CT volume pair. Results: The correlation coefficients after rigid registration were 0.890, 0.921, and 0.859 for the three volume pairs. These improved to 0.979, 0.983, and 0.978, respectively, after deformable registration. These results were comparable to benchmark self‐correlations of the target CTs with a 1.4mm translation error applied (0.979, 0.980, and 0.978, respectively). In the second experiment, rigid registration averaged 10.3mm error (6.6mm SD) while deformable registration averaged 1.1mm error (1.9mm SD) from the “gold standard”. Nearly three quarters (73.9%) of voxels had less than 1mm error and the 95% confidence interval was 4.8mm compared to 0.6% and 23.2mm respectively for rigid registration. Finally, concatenating the forward and reverse deformations resulted in an average distance of 3.1mm (3.1mm SD) from unity. Conclusions: The accuracy and speed of the algorithm suggests its utility for a variety of purposes including integration into an adaptive radiation therapy protocol. Conflict of Interest: Contributing author employed by MIMvista Corp.
SU‐FF‐I‐69: A 2D‐3D Registration Quality Evaluator for Patient Positioning in Radiotherapy
Authors: Wu J , Samant S
Published: July 2007

Purpose: To construct a registration quality evaluator (RQE) for 2D‐3D registration to automatically determine the “goodness” of a registration for user‐defined error tolerance based on average pixel shift in the region of interest, a more consistent quantification of registration error, rather than conventional units in mm and degree. Method and Materials: RQE was automatically constructed from two orthogonal kilovoltage portal images and their corresponding CT dataset of an anthropomorphic cranial phantom. Digitally reconstructed radiographs (DRRs) were generated from a registered CT dataset by adding known arbitrary displacements. Then normalized mutual information (NMI) values between each pair of DRRs and their corresponding portal images were computed, and associated with the known registration error. Based on a user‐defined error tolerance, each sample, which includes a NMI value and its known registration error, was classified as a successful or unsuccessful registration. Finally, supervised learning was performed to calculate a decision threshold on NMI. To determine the goodness of a registration, the registration error can be estimated by calculating the NMI related to the registration output and comparing the value with the RQE threshold. To estimate RQE performance, radio‐opaque markers were attached to the phantom and marker‐based registrations were carried out independently to establish a gold standard. In the absence of markers, this standard can be established by using multiple runs of a registration algorithm alongside visual verification. Results: RQE training yielded a sensitivity and a specificity of 0.9804 (0.8955–0.9995) and 0.9388 (0.8313–0.9872) respectively at 95% confidence interval. Using test dataset, the sensitivity and the specificity of RQE were 0.939 and 0.937, respectively. Conclusion: Our phantom study showed RQE had very good performance in identifying registration errors in 2D‐3D registrations. As part of an automated patient positioning system, RQE can be combined with a 2D‐3D registration algorithm to avoid local optima and improve robustness.
SU‐FF‐I‐72: Reducing PET Scan Duration By Improving SNR Using Super‐Resolution Techniques
Authors: Chang G , Pan T , Qiao F , Clark J , Mawlawi O
Published: July 2007

Objectives: Super resolution (SR) techniques reconstruct a high resolution image from a series of low resolution images taken from different points of view of the same object. The aim of this abstract is to compare the SNR of images reconstructed with and without SR processing versus total scan duration in an attempt to produce images of similar quality but with shorter scan duration.

Methods: A NEMA/IEC phantom containing 6 spheres of varying diameters (1–3.7cm) was filled with F‐18 water and scanned on a DSTE PET/CT scanner. The phantom was scanned in LIST mode for 4 min in 2D and 3D using three different sphere‐to‐background ratios (SBR) (3, 5, and 8). The LIST data was then rebinned into 24 different scan durations in 10 sec increments and reconstructed into 128*128 matrix using OSEM (2 iterations, 21 subsets). In addition, for each scan duration, a 128*128 SR image was generated from 4 64*64 images by offsetting the pixel grid by a 4mm along the X and Y axes. SNR was then determined by drawing ROIs on all spheres and background on all images with and without SR processing for all SBRs and scan durations in both 2D and 3D. Results: For the same scan duration, the noise in images with SR processing is reduced by 19–35% while SNR is improved by 36–40% for all SBRs and scan modes. For the same SNR, scan duration with SR processing can be reduced by 31–41% for different SBRs and scan modes. Conclusion: SR processing produces images with superior SNR and noise content thereby allowing a reduction in PET scan duration while maintaining similar image quality to standard reconstruction. One specific application of SR processing is to improve the quality of gated PET images.
SU‐FF‐I‐73: Artifacts Generated by Interior Tomography
Authors: Graff D
Published: July 2007

Purpose: Although it is well known that quantitative tomography is impossible in systems with interior truncation, this geometry is being increasingly applied to applications such as cone‐beam CT and cardiac SPECT. It has been shown that interior problem, represented by the truncated Radon transform, has a null‐space (and thus could theoretically have an artifact) containing any smooth function in the fully sampled field of view. In practice, artifacts tend to be smooth. Our purpose is to theoretically understand what artifacts will be typically generated under the interior problem. Method and Materials: A linear operator is constructed which generates members of the null‐space of the internal Radon transform. A singular value decomposition of this operator is derived and the singular values are examined. Results: The singular values are all non‐zero, confirming that the null‐space of the truncated Radon transform contains all smooth functions. However, the singular values drop rapidly. When combined with the positivity constraint, this limits the magnitude of all but the lowest singular vectors. Conclusion: Although the null‐space of the truncated Radon transform contains rapidly varying components, their amplitude will be exponentially small. This justifies the use of truncated images to quantitatively measure high‐spatial‐frequency objects such as organ boundaries. Although the formal null‐space is infinite‐dimensional, most of these dimensions are measured in practice with high accuracy. The artifacts generated from actual images can be described with high accuracy by only a few (2–10) parameters. Thus, supplements of the truncated data with low‐quality non‐truncated data or with simple priors can improve the quantifiable accuracy of truncated images.
SU‐FF‐I‐75: Noise Equivalent Quanta of CT Images: Results and Challenges
Authors: Metheany K , Boone J , Abbey C
Published: July 2007

Purpose: To evaluate changes in noise equivalent quanta (NEQ) as technique factors are varied in CT, and to evaluate NPS, MTF, and NEQ as standard quantitative metrics for CT image quality assessment. Method and Materials: The modulation transfer function [MTF(f)] of a GE lightspeed16, clinical CT scanner was measured. A 13μm, nickel‐chromium wire was scanned at 120kVp and 400mAs to obtain a point spread function (PSF). Three reconstruction filters were evaluated. The measured PSF was integrated to obtain the line spread function (LSF), and the MTF(f) was then computed. Ten CT scans of a 20 cm diameter water‐filled pipe were also acquired to measure the noise power spectra [NPS(f)] on the same scanner. The mAs was varied from 10 to 400mAs at constant kVp, and the kVp was varied from 80 to 140kVp at constant mAs. Images using each of the reconstruction filters were evaluated. Using N × N regions of interest (ROI) the NPS(f) was computed by calculating the 2D FFT of each ROI and averaging all of the magnitude, squared FFT results. A minimum of 64 ROI were used per volume, and different ROI placement distributions were evaluated. The 2D results were averaged radially to obtain the 1D NPS(f). The NEQ(f) was computed by dividing the MTF2(f) by the NPS(f). Results: The MTF(f) measurement is straightforward and the NPS(f) metric for CT images demonstrates behavior consistent with trends in photon fluence and apodizing filter behavior. The NPS(f) and NEQ(f) curves demonstrated sensitive changes with kVp, mAs, and slice thickness. Conclusion: While NPS(f) and NEQ(f) normalization issues exist due to the normalization of CT images into Hounsfield Units, these metrics are sensitive to changes in technique and slice thickness changes and therefore are strong candidates for routine quantitative assessment of CT image quality.
SU‐FF‐I‐79: Evaluation of Reproducibility of FMRI Maps in Patients with Proven Low‐Grade Brain Neoplasms
Authors: McKinsey R , Moritz C , Heredia G , Tome W , Meyerand M
Published: July 2007

Purpose: The focus of this project is to demonstrate the test re‐test reliability of fMRI in subjects with benign and biopsy proven low‐grade neoplasms. Methods and Materials: FMRI activation maps with different thresholds were generated for 6 subjects with benign and biopsy proven low‐grade brain neoplasms using a GE Signa 1.5T MRI scanner and birdcage head coil. The imaging protocol included a 3DSPGR T1 brain volume, a coronal T2 anatomical acquisition(24 slices), and 8 functional scans. The 8 functional scans consisted of four functional task repeated twice. Each task verified one of the following: language, language comprehension, fine motor control, and visual perception with Blood Oxygen Dependent(BOLD) responses. Preprocessing steps included dicom to afni conversion, motion correction and spatial smoothing(9mm Gaussian filter). A correlation analysis was performed which allowed the reference timing of the BOLD response in the expected areas to be confirmed. A measure of reproducibility was calculated using the Euclidean distance between the center of mass of the activated volumes in two independent scans and measuring the number of reproducible activated voxels, Rsize. Results and Discussion: Activated clusters were observed for each functional scan. Activated clusters were not observed in all subjects for each task. Rsize was calculated to measure the reproducibility. These measurements will vary between 0.0(worst) and 1.0(best). The Text Listening Task provided the best reproducibility of activated clusters with an average value of 0.94±0.05 and 0.90±0.06 for the left and right temporal lobe, respectively. Activation of clusters amongst subjects varied greatly for the visual perception scan. Previous published results had similar findings. Conclusions: Similar comparisons of reproducibility will be made for more subjects. Roverlap, another parameter used for testing reproducibility will be calculated. The minimum number of clusters used and the cluster radius will be further examined to obtain more activated clusters.
SU‐FF‐I‐80: Comparison of Artifact Size Caused by Metallic Tissue Marking Clips at 1.5T and 3T Breast MRI: A Phantom Study
Authors: Peng Q , Dornbluth C , Kist K , Otto P
Published: July 2007

Purpose: To compare the signal void artifact size caused by metallic tissue marking clips at 1.5T and 3T and to test the impact of different readout bandwidth and TE on the artifact size. Methods and Materials: The signal void size of three commercially available metallic tissue marking clips were assessed at both 1.5T and 3T scanners. The clips studied were immersed in a gel phantom with enough distance (>25mm) to avoid field interference between them. An RF‐spoiled T1‐weighted gradient echo (SPGR) sequence commonly used in DCE breast imaging was used on both scanners with TR/TE/FA=32/4.6/25°, FOV=160mm, spatial resolution of 1×1×4mm3, and water fat shift of 1.534 pixels (i.e., readout bandwidth = 22.6 kHz for 1.5T, and 45.3 kHz for 3T). Same sequence was repeated with higher readout bandwidth of 139 kHz (1.5T) and 198 kHz (3T). In addition, TE=1.16ms was also tested with partial Fourier readout and high readout bandwidth to study change of TE on the effect of signal void artifact size on both scanners. Results: At TE=4.6ms, both scanners showed signal void artifacts 2∼8 times larger than the clips themselves. Importantly, the signal void size was 15%∼30% larger at 3T compared to that of 1.5T. Increasing readout bandwidth had little impact on signal void artifact size on both scanners. However, decreasing TE from 4.6 ms to 1.16 ms reduced the average artifact size at both 1.5T (27%) and 3T (31%). Conclusion: Signal void artifact size is larger at 3T for all three metallic tissue marking clips studied at the current experimental settings. This could be a disadvantage of 3T scanners when used to detect and follow‐up breast cancer adjacent to metallic tissue marking clips after biopsy. Short TE can be used to effectively reduce signal void artifacts at both 1.5T and 3T.
SU‐FF‐I‐83: Effect of Tumor Motion On the Pixel‐Based Analysis of DCE‐MRI Data for Cervical Cancer
Authors: Yuan J , Mayr N , Wang J , Zhang H , Martin D , Yuh W
Published: July 2007

Purpose: The quantitative imaging analysis of dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) data is subject to errors caused by motion during the image acquisition. Previous studies on the pixel‐by‐pixel analysis of perfusion DCE‐MRI for cervical cancer ignored this motion effect or corrected it manually. To improve the quantification of tumor perfusion, a comprehensive analysis of the tumor motion was conducted in this work by automatically registering the time series of DCE‐MRI. Methods and Materials: Fifty‐six patients and a total of 192 MR examinations were included in the registration study. To improve image quality, before registration the image noise was first reduced by employing edge preserving smoothing techniques. A mask region including uterus, bladder and cervix was applied to all time‐serial slices so that both internal organ motion and patient body movement were taken into account in the image registration. The registration was then performed by rigid translation using the normalized mutual information (NMI) algorithm to compensate respiratory and bowel motion, followed by non‐rigid transformation using the Demons algorithm to compensate for deformation within the slice plane. Results: For all 56 patients and 192 studies, most of slices (80%) in each study have ±1 mm or less translational displacement from registration to the reference image, and 20% of the slices have a ⩾ 2 mm translational displacement. In most slices (80%), the absolute motion is approximately 1 pixel (1.526 mm) and 10% of slices have more than 3‐pixel motion (⩾ 4–5 mm). Conclusions: Movements at the level larger than the pixel size will lead to pixel misalignment in a time series, consequently will influence the pixel‐based analysis of tumor perfusion data. Therefore, accounting for and correcting tumor motion effects by image registration may improve the results of the pixel‐based analysis of DCE‐MRI data for cervical cancer.