فهرست مطالب

Frontiers in Biomedical Technologies - Volume:6 Issue: 4, 2019
  • Volume:6 Issue: 4, 2019
  • تاریخ انتشار: 1398/10/09
  • تعداد عناوین: 8
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  • Mohmmadreza Nazemzadeh* Pages 161-167

    Medical imaging measurements have been increasingly investigated as imaging biomarkers for detecting physiological and pathological changes. It is critical to evaluate the reliability of the changes in measurements observed in an individual patient for any clinical decision making. The purpose of this article is to review the utility of uncertainty analysis in medical imaging measurements for individual patients undergoing any pathology or medical therapy. We specifically show how to assess whether the observed alterations in measurements are true changes, i.e. the changes due to medical conditions alone, beyond the uncertainty associated with the imaging, image analysis, or natural physiological occurrences. In order to elaborate the uncertainty concept and the potential applications of uncertainty analysis in the field medical imaging, we reopen two of our previous articles published in the “journal of Physics in Medicine and Biology” [1], and the “Journal of neurological sciences” [2], respectively. While the first study delineates the uncertainty analysis in the context of longitudinal imaging for evaluating the validity of serial measurements, the second work intricates such an application for evaluating the laterality indices and interhemispheric changes in the pathologic brains in cross-sectional studies. Assessment of the repeatability and confidence interval of medical measurements of an endpoint of interest allows us to determine the true changes in measurements, beyond the uncertainty. We have demonstrated how to use estimated repeatability coefficients to evaluate imaging biomarkers for assessing radiation-induced neurotoxicity in patients who had low-grade or benign tumors and were treated by partial brain radiation therapy. We also showed how to use estimated interhemispheric variation uncertainty to identify the epileptogenic side in the patients with temporal lobe epilepsy. In conclusion, we demonstrated that the analysis of uncertainty for the changes in imaging attributes is absolutely crucial, yet beneficial in the context of accurate and reliable diagnostic medical imaging and customizing appropriate treatments for individual patients. The concept can be applied to other imaging modalities and biomarkers in diagnostic and therapeutic assessments.

  • Raheleh Rooshenass, Mehdi Salehi Barough*, Somayeh Gholami, Ehsan Mohammadi Pages 168-173
    Purpose

    The aim of this study is to compare the accuracy of different algorithms in EclipseTM Treatment Planning System (TPS) using a heterogeneous phantom.

    Materials and Methods

    The method is based on the International Atomic Energy Agency's TEC-DOC 1583 report. The chest phantom of CIRS, PTW30010 ionization chamber and an electrometer (PTW, Freiburg) were used for the measurements.Three ACUROSE XB (AXB), Analytical Anisotropic Algorithm (AAA) and Pencil Beam Convolution (PBC) dose calculation algorithms available in Eclipse TM TPS were considered in this study.

    Results

    Based on the measurements, the maximum differences between calculated dose by TPS and measured dose in TEC-DOC 1583 tests were 2.5%, 8.6% and 16.1% for the AXB, AAA and PBC algorithms in heterogeneous media, respectively.

    Conclusion

    The Acuros XB algorithm has superior accuracy to predict the dose distribution in the heterogeneous tissues such as lung compared to AAA and PBC algorithms.

    Keywords: Heterogeneous Tissues, Treatment Planning System, Dose Calculations
  • Samira Yazdani, Fathollah Bouzarjomehri, Eric Slessinger Pages 174-180
    Purpose

    Radiation Therapy has a fundamental role in the treatment of cancer. Achieving Tumor Control Probability (TCP), while avoiding normal tissue complication is the goal of this treatment modality. The sensitivity of the thyroid gland to radiation increases the risk of developing secondary thyroid cancer and hypothyroidism.

    Materials and Methods

    The average dose to the thyroid from head and neck irradiation was measured using in vivo dosimetry (Thermolumincsence Dosimetry). The Radiotherapy technique was given using 6 MV x-rays from an Elekta compact linear accelerator and conformal technique delivered 1.8 to 2.0 Gy over 5 sequential days per week.

    Results

    The average absorbed dose to the thyroid from head and neck radiotherapy was 4.4% of the prescription dose and from whole brain radiotherapy was 0.7% of the prescription dose. Thyroid Stimulating Hormone (TSH) levels were determined in 30 patients before and after completion of radiation therapy. The average concentration of TSH increased from 0.88 +/- 0.55 (pre-radiotherapy) to 1.7 +/- 0.66 (post-radiotherapy), (p < 0.05).

    Conclusion

    Thyroid absorbed dose was less than the threshold dose for patients who received radiotherapy to the head and neck based on thyroid function tests.

    Keywords: Radiotherapy, Hypothyroidism, Thermolumincsence Dosimetry, Treatment Planning System, Head, Neck Tumors
  • Mahak Osouli Alamdari, Pardis Ghafarian, Parham Geramifar, Mohammad Reza Ay Pages 181-186
    Purpose

    Positron Emission Tomography (PET) imaging is a nuclear medicine imaging technique based on the recording of two photons as coincidence created by positron annihilation.

    Materials and Methods

    PET coincidence events include true and unwanted coincidences (random, scattered, multiple coincidences). We modeled the Discovery 690 (D-690) PET scanner using the GATE simulation tool and estimated the effect of the diameter of the scattering medium out of the Axial Field of View (AFOV) on the random coincidence rates.

    Results

    The validation results indicated that the average difference between simulated and measured data for sensitivity and scatter fraction tests are 5% and 3%, respectively. Moreover, the results revealed that the increasing diameter of the scattering medium out of the AFOV has a direct effect on the random coincidence rates within the Field of View (FOV).

    Conclusion

    The study concluded that the presence of a scattering medium near the FOV increases the rate of random coincidences.

    Keywords: Positron Emission Tomography, Random Coincidences, Noise Equivalent Count Rate, Monte Carlo
  • Azimeh Dehkordi*, Saeideh Koohestani Pages 187-196
    Introduction

    Recruiting the pharmacokinetic parameters estimated from noninvasive methods such as Dynamic Contrast Enhanced MRI (DCE-MRI) to evaluate or plan treatment procedure is widely interested in clinical practices. Interpretation of the DCE-MRI data are highly dependent to precision and accuracy of the estimated parameters. One of the most effective factors on the DCE-MR images and consequently on the contrast concentration profile is signal to noise ratio. This work focuses on the analytically evaluation of the noise effect on accuracy of the estimated PK parameters in DCE-MRI studies.

    Materials and Methods

    Tofts model as a popular pharmacokinetic model and model selection technique was used to simulate 3470 time curves of contrast concentration. Maximum likelihood estimator as a minimum variance unbiased estimator was recruited to estimate the PK parameters.  Eleven levels of signal to noise ratios (SNR= 5, 8, 10, 13, 15, 20, 25, 30, 35, 50, Noiseless) were added to the simulated CA concentration profiles. The PK parameters were estimated for 11 series data and then mean percentage error was calculated for estimated parameters.

    Results

    The results indicate that the most sensitive parameters to the SNR of the DCE-MR images is inverse transfer constant. A SNR greater than 25 was found to be ensure a reasonable error (<5%) in all models parameters.

    Conclusion

    Clinical decision based on the DCE-MRI data analysis and estimated PK parameters needs a good image quality (SNR>25), an accurate and robust estimator and correct pharmacokinetic model selection.

    Keywords: Dynamic Contrast Enhanced Magnetic Resonance Imaging, Signal to Noise Ratio, Pharmacokinetic Parameters Accuracy, Contrast Concentration Uncertainty
  • Gholamreza Fallah Mohammadi*, Yasaman Kiumarsi, Pardis Eghbaliyan Pages 197-203
    Purpose

    The aim of this research was to estimation of patient effective dose from digital radiography repeat rate and related factors in two referral hospital in Sari, Iran.

    Materials and Methods

    Entrance skin dose and effective dose per common radiography procedures in digital radiography was measured using the BARACUDA RTI detector. 1724 x-ray exposures were investigated prospectively. The annual number of each radiographic procedure was obtained from the archives of digital radiography departments. Patient cumulative dose was calculation from annual exposures repeat rate(RR) and effective dose per digital radiography procedures.

    Results

    Mean exposure RR per examination was 1.2% and total percentage of repeat of all examination was 8.7%. annual cumulative dose(man-sivert) resulted from radiographic RR was, 449.2.  The factors leading to the repetition was include the radiographer error (69%), the X-ray tube and equipment error (10.4%), the patient related error (16.1%) and other cases (4.1%). The average effective dose for each examination was 0.36 mSv.

    Conclusion

    Digital radiographic repeat rate increases 1.1 % annual patient effective dose from the base level that receives from current radiographic examination. Inconsistency of the center of the digital panel and the central axis of the X-ray beam and error in selection of the upright or table digital panel are among the most important factors in the repetition of digital radiography.

    Keywords: Digital Radiography, Effective Dose, Repeat Rate
  • Nayereh Joodi*, Farzaneh Rahmani Pages 204-216
    Purpose

    This paper aims to review the recent linguistic research carried out with the help of fMRI.

    Materials and Methods

    We performed a comprehensive search on ProQuest and Scopus search engines using keywords: "functional MRI", "fMRI", and "linguistics", "phonetics", "semantics", and their synonyms, yielding to a total of 343 articles. We included 23 articles based on full-text review which conducted original research on different aspects of language processing using fMRI. Studies regarding applied linguistics, as well as studies using subjects with any neuropsychological disorders, were excluded.

    Results

    Included studies were categorized according to the language areas they investigated, including phonetics and phonological processing; semantics; and syntax. The results show that the auditory cortex of both hemispheres is responsible for phonological comprehension of language at the first level, followed by left dominant processing of suprasegmental language in the superior temporal gyrus and the inferior frontal cortices and the supplementary motor area. During semantic processing of the language, lexical entry takes place in the medial temporal lobe and the hippocampus, while sentential semantic aspects of the language are predominantly processed in the left anterior temporal cortex. The BA 44 area is the major active region during syntax processing.

    Conclusion

    The experimental methods in studying language such as fMRI and other neurolinguistics techniques could provide scientific evidence for proving theoretical assumption. Besides, results of such researches can help other scientific developments such as brain mapping and pre-surgical planning.

    Keywords: Functional Magnetic Resonance Imaging, Neurolinguistics, Phonetics, Phonological Processing, Syntax, Semantics
  • Seyed Mohsen Ebrahimi, Mojtaba Seydi, Mahyasadat Ebrahimi, Marjaneh Hejazi* Pages 217-220
    Purpose

    In this report the design concept and experimental evaluation of the performance of Fluo Vision have been illustrated.

    Materials and Methods

    The Fluo Vision system designed for fluorescence concentration imaging. In order to assess the capability of the system, results of reference design have been analyzed.

    Results

    Results of the Fluo Vision system are matched with the reference design.

    Conclusion

    The evaluation indicated that Fluo Vision is adequate as a fluorescence imaging system for fluorescence concentration imaging.

    Keywords: Fluo Vision, Fluorescence Imaging, Light Leakage, Optical Imaging