فهرست مطالب

Iranian Journal of Medical Physics
Volume:11 Issue: 4, Autumn 2014

  • تاریخ انتشار: 1393/09/01
  • تعداد عناوین: 8
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  • Abdolkazem Ansarinejad, Anna Ferrari Pages 294-300
    Introduction
    Today, there is a growing interest in the use of hadrontherapy as an advanced radiotherapy technique. Hadrontherapy is considered a promising tool for cancer treatment, given its high radiobiological effectiveness and high accuracy of dose deposition due to the physical properties of hadrons. However, new radiation modalities of dose delivery and on-line beam monitoring play crucial roles in a successful treatment. In hadrontherapy, through interactions between the primary beam and patient’s tissue, secondary neutrons are produced.
    Materials And Methods
    This study, by using FLUKA Monte Carlo simulations, assessed the level of secondary neutron radiation, produced during patient treatment. In addition, the evaluation included secondary neutron radiation, which was produced while hitting the on-line detectors of beam delivery system by the Italian National Center for Hadrontherapy (CNAO). This study assessed the effects of secondary neutron radiation on an electronics rack (including a data acquisition system, a power supply, and a gas system) and a nozzle, where two monitoring boxes (each one consisting of two or three parallel plate ionization chambers) were installed.
    Results
    The resulting neutron energy spectra and radiation doses were used to determine the life performance and the probability of damage to these devices. Findings showed that by using carbon ions of 400 MeV/u, the fluence rate of secondary neutrons will be approximately 3.4×1010 n/cm2 in a year.
    Conclusion
    This value is lower than the experimental threshold, which is responsible for less than 1% of changes in electrical characteristics, and would cause no single event upsets.
    Keywords: Neutron Diffraction, Proton Therapy, Radiation Effects, Monte Carlo Method
  • Mohammad Taghi Bahreynitoossi, Malakeh Malekzadeh Pages 301-307
    Introduction
    Given the fact that children are more sensitive to radiation, compared to adults, special attention needs to be paid to radiation protection in pediatric radiology. Diagnostic reference level (DRL) has been defined to be employed as a practical tool for examining the overall performance of a radiological center in terms of patient dose among a series of similar equipments in an area or an institution as a Local DRL (LDRL).
    Materials And Methods
    To establish DRL for diagnostic X-ray examinations of children in KhorasanRazavi province, data were collected from 627 pediatric patients. The average of entrance surface doses (ESDs), arising from chest and abdomen examinations, were examined for three different age groups.
    Results
    Local DRL (LDRL) were calculated to be 77, 126, and 138 µGy for chest examinations of <1-month-old, 1-12-month-old, and 1-5-year-old groups, respectively. The corresponding values obtained from abdomen radiographies were 152, 120, and 280 µGy, respectively.
    Conclusion
    Our findings revealed that local DRLs in this study are higher than the corresponding values, recommended by the Commission of European Communities (CEC) and National Radiological Protection Board (NRBP). Higher ESDs acquired for chest examination were related to the use of low kVp, relatively high mAs in all centers, and use of grid for most of the patients.
    Keywords: Diagnostic Reference Level, Pediatric, Radiology, Entrance Surface Dose, Iran
  • Zohreh Dehghani-Bidgoli, Mohammad Hosein Miran Baygi, Ehsanollah Kabir, Rasoul Malekfar Pages 308-315
    Introduction
    Raman spectroscopy is a vibrational spectroscopic technique, based on inelastic scattering of monochromatic light. This technique can provide valuable information about biomolecular changes, associated with neoplastic transformation. The purpose of this study was to find Raman spectral markers for distinguishing normal samples from cancerous ones in different tissues.
    Materials And Methods
    Ten tissue samples from the breast, colon, pancreas, and thyroid were collected. A Raman system was used for Raman spectroscopic measurement of tissues at 532 nm laser excitation. Five to six Raman spectra were acquired from each sample (a total of 52 spectra). Raman spectra were investigated in important bands associated with Amid1, CH2 (scissoring), Amid3, d(NH), n(C-C), and das (CH3) in both normal and cancerous groups. In addition, common spectral markers, which discriminated between normal and cancerous samples in the above tissues, were investigated.
    Results
    Common spectral markers among different tissues included intensities of Amid3 and CH2 (scissoring) and intensity ratios of I(Amid1)/I(CH2), I(n(C-C))/I(CH2), and I(d(NH))/I(CH2). This study showed that Amid1-, n(C-C)-, and d(NH)-to-CH2 intensity ratios can discriminate between normal and cancerous samples, with an accuracy of 84.6%, 82.7%, and 82.7% in all studied tissues, respectively.
    Conclusion
    This study demonstrates the presence of common spectral markers, associated with neoplastic changes, among different tissues.
    Keywords: Breast Cancer, cancer detection, colon cancer, pancreas cancer, Raman spectroscopy, thyroid cancer
  • Bagher Farhood, Seyed Rabie Mahdavi, Mohammad Hasan Emranpour, Kamal Mohammadi Asl, Navid Nekoui, Courtney Knaup Pages 316-321
    Introduction
    The first medical intervention for many breast cancer patients is breast conserving surgery (BCS) and/or modified radical mastectomy (MRM). Most of these patients undergo radiation therapy, following surgery. The most common side-effect of breast radiotherapy is skin damage. In the present study, the severity of acute skin changes and the underlying causes were investigated in patients undergoing BCS and radiotherapy.
    Materials And Methods
    This prospective, cohort study was performed on 31 female patients, undergoing breast surgery therapy at Shahid Rajaie Babolsar Radiotherapy Center from September 2011 to July 2012. A questionnaire was designed, including the patient’s characteristics, details of radiotherapy technique, and skin damage; the questionnaire was completed for each patient. The obtained results were analysed by performing ANOVA and Fisher''s exact tests. Complications were graded using the radiation therapy oncology group (RTOG) scale.
    Results
    Grade 0 or 4 of skin damage was observed in none of the patients. Among the evaluated patients, 58%, 35.5%, and 6.5% of the patients had grade 1, grade 2, and grade 3 of skin damage, respectively. There was no statistically significant relationship between regional skin burns and factors such as average tangential field size, internal mammary field, chemotherapy, prior history of diseases, tamoxifen use, previous radiotherapy in breast area, or skin type (p>0.05). However, there was a significant relationship between skin burns and presence of supraclavicular field (p=0.05).
    Conclusion
    Considering the significant relationship between skin burn and supraclavicular field, special attention needs to be paid to factors affecting the treatment planning of supraclavicular field such as field size and photon energy.
    Keywords: Breast Cancer, Radiotherapy, Skin Burns, Breast Conserving Surgery, Surgery
  • Pages 322-327
    Introduction
    Signal intensity uniformity in a magnetic resonance (MR) image indicates how well the MR imaging (MRI) system represents an object. One of the major sources of image non-uniformity in high-field MRI scanners is inhomogeneity of radio-frequency coil. The aim of this study was to investigate non-uniformity in head, head and neck, and body coils and compare the obtained results to determine the best clinical coil for future clinical application.
    Materials And Methods
    A phantom was designed to investigate the non-uniformity of coils. All evaluations were carried out using a 1.5 T clinical MRI scanner. T1-weighted inversion recovery sequence (linear phase encoding) and turbo fast low angle shot (TurboFLASH) images were used to find non-uniformity in the clinical coils. For testing the uniformity of coils, signal intensity profiles in parts of the coronal image of phantom were measured over X and Y axes.
    Results
    The results showed that body coil was the most uniform coil of all; in addition, the head and neck coil was more uniform than the head coil. The results also indicated that signal-to-noise ratio (SNR) of the head and neck coil was higher than the head and body coils. Moreover, SNR of the head coil was higher than that of the body coil.
    Conclusion
    In order to accurately find or apply an image signal intensity for measuring organ blood flow or perfusion, coil non-uniformity corrections are required.
    Keywords: Coil, MRI, Prospective Studies, Signal, To, Noise Ratio
  • Pages 328-333
    Introduction
    Pterygium is a wing-shaped, vascular, fleshy growth that originates from the conjunctiva and can spread into the corneal limbus and beyond. Beta irradiation after bare sclera surgery of primary pterygium is a simple, effective, and safe treatment, which reduces the risk of local recurrence.
    Materials And Methods
    Dosimetric components of strontium-90 (90Sr), phosphorous-32 (32P), and ruthenium-106 (106Ru), in form of ophthalmic applicators, were evaluated, using the Monte Carlo method.
    Results
    The obtained results indicated that 32P applicator could deliver higher doses (about 10 Gy) to a target, located within a close distance from the surface, compared to 90Sr and 106Ru; it also delivered a lower dose to normal tissues.
    Conclusion
    The risk of pterygium has increased given the geographical location and climate of Iran. Spread of dust in the country over the past few years has also contributed to the rising rate of this condition. Our results showed that using 32P applicator is a cost-effective method for pterygium treatment.
    Keywords: Pterygium, 32P applicator, Monte Carlo method, MCNP
  • Javad Sayahzadeh, Hamidreza Pourreza, Javad Salehi Fadardi Pages 334-349
    Introduction
    “Blink” is defined as closing and opening of the eyes in a small duration of time. In this study, we aimed to introduce a fast, robust, vision-based approach for blink detection.
    Materials And Methods
    This approach consists of two steps. In the first step, the subject’s face is localized every second and with the first blink, the system detects the eye’s location and creates an open-eye template image. In the second step, the eye is tracked, using sum of squared distances (SSD). This system can classify the state of the eyes as open, closed, or lost, using the SSD-based classifier. If the eyes are closed as in usual blinking, the blink will be detected. To classify eyes as closed or open, two adaptive thresholds were proposed; therefore, factors such as the subject’s distance from the camera or environment illumination did not affect the system performance. In addition, in order to improve system performance, a new feature, called «peak-to-neighbors ratio», was proposed.
    Results
    The accuracy of this system was 96. 03%, based on the evaluation on Zhejiang University (ZJU) dataset, and 98. 59% in our own dataset.
    Conclusion
    The present system was faster than other systems, which use normalized correlation coefficient (NCC) for eye tracking, since time complexity of SSD is lower than that of NCC. The achieved processing rate for ZJU dataset was 35 fps.
    Keywords: Eye Localization, Blink Detection, Sum of Squared Distances
  • Shokouhozaman Soleymanifard, Mohammad Taghi Bahreyni Toossi, Shokoufeh Mohebbi, Ameneh Sazgarnia, Seyed Ahmad Mohajeri Pages 350-357
    Introduction
    Radiation-induced bystander effect (RIBE) is a phenomenon in which radiation signals are transmitted from irradiated cells to non-irradiated ones, inducing radiation effects in these cells. RIBE plays an effective role in radiation response at environmentally relevant low doses and in radiotherapy, given its impact on adjacent normal tissues or those far from the irradiated tumor. Reactive oxygen species contribute to RIBE induction. Therefore, the present study was conducted to investigate the possible inhibitory effects of garlic, as an antioxidant-containing plant, on RIBE.
    Materials And Methods
    MCF7 cells, treated with raw garlic extracts, were irradiated by 60Co gamma rays, and their culture medium was transferred to non-irradiated autologous bystander cells. Percentage cell viability and micronucleus formation in both irradiated and bystander cells were examined and compared with corresponding cell groups, not treated with garlic.
    Results
    Treatment with garlic extract reduced the number of micronucleus-containing cells in both irradiated and bystander cells. However, it only increased the percentage cell viability in bystander cells, not the irradiated ones.
    Conclusion
    RIBE was effectively suppressed by raw garlic extracts. Inhibitory effects of raw garlic may be of particular importance for exposure to environmentally relevant low doses, where RIBE dominates direct radiation effects. They are also partially important for addressing the limited therapeutic gain of radiotherapy, as they may only increase the percentage cell viability of bystander cells, not the directly irradiated tumor cells. However, more comprehensive in-vivo research regarding garlic treatment duration is required to support the obtained results.
    Keywords: Allium Sativum, Antioxidant, MCF7 Cells, Radiation, Induced Bystander Effect, Raw Garlic