فهرست مطالب

  • Volume:2 Issue: 2, 2015
  • تاریخ انتشار: 1394/05/16
  • تعداد عناوین: 8
|
  • Hassan Mohy, Ud, Din, Nicolas A. Karakatsanis, William Willis, Abdel K. Tahari, Dean F. Wong, Arman Rahmim Pages 366-379
    Purpose
    Inter-frame and intra-frame motion can adversely impact the performanceof dynamic brain PET imaging. Only correcting the former can still result in degradedqualitative and quantitative performance. Meanwhile, patient motion introducesmismatches between transmission and emission data which may lead to incorrectattenuation and scatter compensation in the reconstruction process. As a result,the reconstructed dynamic images may carry erroneous estimates of radioactivitydistribution. We seek a solution to this problem.
    Methods
    We investigated the use of iterative deconvolution coupled with a proposeduse of time-weighted averaging of motion-transformed transmission images to correctthe transmission-emission mismatch artifacts in dynamic brain PET images. Weperformed simulations using real-patient motion profile acquired by the infrared PolarisVicra motion tracking device which estimates 3-D motion transformations during PETacquisition. This was followed by frame-based motion correction employing threedifferent transmission-emission alignment strategies: transmission image transformedby (1) mean motion transformation, (2) median motion transformation, and (3) theproposed time-weighted average of motion-transformed transmission images.
    Results
    The results demonstrate that the proposed approach of using time-weightedaveraging of motion transformed transmission images outperforms conventionalmethods by substantially reducing the transmission-emission mismatch artifacts inthe reconstructed images. Coupled with an alignment of the reconstructed framesfor inter-frame motion correction and a subsequent iterative deconvolution approachfor intra-frame motion correction, the resulting motion compensated images showedsuperior quality, considerable reduction in error norm and enhanced noise-biasperformance compared to conventional methods of transmission-emission mismatchcompensation. The performance was consistent across different levels of intra-framemotion, and the algorithm was amenable to different framing schemes.
    Conclusion
    In frame-based motion correction of dynamic PET images, it is feasibleto achieve intra-frame motion compensation using time-weighted averaging ofmotion transformed transmission images coupled with a post-reconstruction iterativedeconvolution procedure to compensate for intra-frame motion.
    Keywords: Dynamic PET Imaging, Transmission, Emission mismatch artifacts, Inter, frame, Intra, frame motion, motion compensation
  • Saber Nankali, Ahmad Esmaili Torshabi, Payam Samadi Miandoab, Amin Baghizadeh Pages 380-387
    Purpose
    In external beam radiotherapy of dynamic tumors, several errors raise due tointer- and intra-fractional motions. In order to compensate these errors, signals obtainedfrom different surrogates are used to infer with tumor motion as real time. Therefore,a comparative assessment may be worthwhile on the effect ofdifferent surrogates intumor motion tracking.
    Methods
    The performance accuracy of three internal-external surrogates entitled:external markers, diaphragm movement and lung volume was done using 4Dimensional Extended Cardiac-Torso (4D-XCAT) phantoms. Adaptive NeuroFuzzy Inference System (ANFIS) model was implemented to correlate the motionof surrogates with several tumors located in liver and lung, separately. Finally,the Root Mean Square Error (RMSE) of ANFIS model outputs in tumor motionpredictionof different surrogates was compared as metric tool.
    Results
    The average value of RMSE of lung and liver tumors were 0.4 mm, 0.6 mmand 0.8 mm for external markers, lung volume and diaphragm motion, respectively.
    Conclusion
    Among three investigated surrogates, the best performance belonged toexternal markers strategy, while optimum location of these markers determined usingan input selection algorithm in this method.
    Keywords: External radiotherapy, Tumor tracking, Surrogates, ANFIS model, Input selection
  • Amin Asgharzade Alvar, Amir Salar Jafarpisheh, Zahra Shirzhiyan, Akram Pourbakht, Azadeh Ghalyanchi, Amir Homayoun Jafari Pages 388-396
    Purpose
    In elementary studies on brainstem evoked potentials a simple stimuli likeclick and sinusoidal tones is used, but in recent years Auditory Neuroscience orientedto use complex stimuli. These complex stimuli (e.g. speech and music) are morecapable in representation of auditory pathway functions. Previous studies in this field,mainly attend to one single vowel or consonant-vowels. Until now no study has beendone which considered the encoding of multi structurally meaning full combination ofconsonant-vowel. In this study, we try to extract information using suitable tools fromAuditory Brainstem Responses (ABR) to stimuli ‘’baba’’.
    Methods
    At the first step we used a test to find an appropriate distance betweentwo consecutive consonant- vowels ‘ba’ which is perceived ‘baba’. For this, apsychophysical test was designed. Subjects were asked to choose a suitable distancebetween two ‘ba’ that the combination perceived ‘baba’. After recording evokedpotentials to ‘ba’ and ‘baba’, we searched distinctive features between the signalsrelated two stimuli. So at first, we began with comparative time-frequency analyseslike correlation and coherence.
    Results
    Correlation analyses show that the response to ‘ba’ and the response to firstsyllable of ‘baba’ in the Onset and also transient parts of responses are different and theresponse to first and second syllable of /baba/ become similar. The results of coherenceanalyses show that these differences could not be represented with a linear relationmerely.
    Conclusion
    Brainstem neural activity was different in countering with single syllablestimuli in comparison with meaningful disyllabic stimuli. These changes can beconsequences of activities in anatomical top-down pathway.
    Keywords: Brainstem evoked response(ABR), Correlation analysis, Coherence analysis, Disyllabic
  • Saeedeh Navaei Lavasani, Anahita Fathi Kazerooni, Hamidreza Saligheh Rad, Masoumeh Gity Pages 397-403
    Purpose
    Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) is aneffective tool for detection and characterization of breast lesions. Qualitative assessmentof suspicious breast DCE-MRI is problematic and operator dependent. The purposeof this study is to evaluate diagnostic efficacy of the representative characteristicparameters, extracted from kinetic curves of DCE-MRI, for discrimination betweenbenign from malignant suspicious breast tumors.
    Methods
    Pre-operative DCE-MR images of twenty-six histopathological approvedbreast lesions were analyzed. The images were reviewed by an expert radiologist andthe regions of interests (ROI)s were selected on the most solid part of the lesion. Semiquantitativekinetic parameters, namely: maximum signal enhancement (SImax), initialarea under the curve (IAUC60), time to peak (TTP), wash in rate (WIR), wash out rate(WOR) and signal enhancement ratio (SER), were calculated within each ROI. Meanvalues of the calculated features among benign and malignant groups were comparedusing student’s t-test. Finally, a classification was performed employing supportvector machines (SVM) using each of the parameters and their combinations in orderto investigate the efficacy of the parameters in distinguishing between benign frommalignant tumors.
    Results
    The performance of the classification procedure employing the combinationof semi-quantitative features with (p-value<0.001) was evaluated by means of severalmeasures, including accuracy, sensitivity, specificity, positive predictive value andnegative predictive value which returned amounts of 97.5%, 96.49%, 100%, 100%and 95.61% respectively.
    Conclusion
    In conclusion, semi-quantitative analysis of the characteristic kineticcurves of suspicious breast lesions derived from SVM classifier
    Keywords: Breast cancer, Dynamic contrast enhancement, Classification, Semi, quantitative features, Support vector machine
  • Payam Samadi Miandoab, Ahmad Esmaili Torshabi, Saber Nankali Pages 404-413
    Purpose
    Although in the external beam radiotherapy tumor motionis a crucial andchallenging issue due to respiration motion, temporal changes in anatomy duringimaging cause considerable problems. Moreover, the Four Dimensional ComputedTomography (4DCT) imaging has been proposed to track these changes at thedifferent breathing phases. Also at real time tumor tracking, the accuracy of motiontracking models that are necessary can be increased by constructing virtual imagesdue to obtaining additional motion data.
    Methods
    In this study, the 4DCT data set of five real patients who have had lungcancer were provided by DIR-lab site in addition to deformable image registrationalgorithms presented in MATLAB software and DIRART software respectively tocalculate 2D and 3D vector felids between two respiratory volumes. Moreover, the2D and 3D displacement vector were calculated by optical flow based on Horn-Schunck method, these vector fields were used to generate an interpolated image at thedesired time by 2D and 3D interpolation methods. Although 2D interpolation methodsincluded nearest, cubic, linear, and B-spline, the 3D interpolation method was based onthe 3D spatial interpolation. In this study, the reconstructed image at the desired timeby two methods was compared with real image at the same time. Considering RootsMean Square Error (RMSE) between actual and interpolated imageis used to measurethe accuracy of interpolated images. Also the accuracy of our reconstruction imagesdepends on the accuracy of displacement field.
    Results
    All of the methods are able to generate images at the desired time withless RMSE and high correlation coefficient. While the 2D interpolation methodsthat include nearest, cubic, linear, and B-spline were able to generate an imagewith less errors, the performance of the 2D interpolation method is less efficientthan other methods.
    Conclusion
    The behavior and capability of the algorithmsare demonstrated bysynthetic image examples. Furthermore, to compare 2D and 3D optical flow basedinterpolation methods, the RMSE quantitative measures are calculated. Results indicatethat both 2D and 3D interpolation presented methods are outperformed significantly,and the patient is kept away from re-scanning for getting new images.
    Keywords: 2D, 3D Image reconstruction, 2D, 3D optical flow, 4DCT Deformable image registration, IGRT, DIRART
  • Siavash Mazdeyasna, Amir Homayoun Jafari, Jamshid Hadjati, Armin Allahverdy, Mehdi Alavi Moghaddam Pages 414-420
    Purpose
    Plans for all types of therapies for cancer need to be updated according to new achievements in science and technology. Building models of in vitro cancer cell growth, may make a predictive view for physicians about the behavior of these cells in the real world.
    Method
    In this study using experimental data which acquired from cultured cells and taking photos using a digital microscope lens, we designed a cellular automata model of death and growth of melanoma cancer cells in the presence of different concentration of FBS and different dose of Cisplatin as a chemotherapy drug.
    Results
    As we say this model is based on cellular automata although we used a genetic algorithm for this model which this combined model casts a dynamic in model and made that adoptive based on the alternation of the environment. In the end, we achieved to 75% prediction accuracy about the behavior of these cells.
    Conclusion
    The proposed model showed approximately good results to predict tumor growth in the presence of different dosages of chemotherapy drug and it can make a perspective of tumor growth for us.
    Keywords: Cancer, Melanoma, ModeL, Chemotherapy, Cisplatin, Cellular Automata, Genetic Algorithm
  • Banafsheh Zeinali Rafsanjani, Reza Faghihi, Mahdi Saeedi Moghadam Pages 421-426
    Purpose
    MR only treatment planning for pediatric radiation therapy is helpful to reduce the patient dose and more precise target definition. Bone segmentation and assigning a suitable bulk electron density to bone tissue is important in this technique. Bone in children under 14 years old is still developing so the mineral density is changing during these ages. The objective of this study is to assess the effect of assigning the same bulk electron density to bone tissues of the children with different ages on dose distribution.
    Methods
    Seven sets of skull CT images of children under 19 years old were selected. Skull bones were segmented and the CT numbers extracted, then the CT numbers converted to density. In order to compare the differences of dose distribution due to differences in bone density, the percentage depth dose was calculated by Monte Carlo simulation in inhomogeneous phantoms.
    Results
    The results of PDDs in photon and electron sources did not show a significant difference (<2%) between different densities beneath the bone tissue.
    Conclusion
    When MR only treatment planning is to be used for a child, the bulk density method is accurate enough for treatment of brain or underneath area of bone. However, if the target of radiation therapy is bone, this method may cause a little error in dose calculation especially in superficial and electron therapy, so that voxel based methods are more reliable for these treatments.
    Keywords: Bone development, electron density, segmentation, MR only treatment planning
  • Aram Radnia, Mohammad Hossein Farahani, Hoorvash C. Yousefzadeh, Mohammad Reza Ay Pages 427-429
    Purpose
    In this report the design concept and experimental evaluation of the performance of HeliGuide have been illustrated.
    Methods
    14C-UBT system designed for detecting Helicobacter pylori. In order to assess the capability of the system, results of 221 reference cards have been analyzed.
    Results
    Results of the HeliGuide system are matched with the reference.
    Conclusion
    Results of the evaluation indicated that HeliGuide is adequate as a Urea Breath Test system for detecting helicobacter pylori.
    Keywords: 14C, Urea breath test, Helicobacter pylori, Peptic ulcer disease, Stomach ulcer, Beta counter