IRANIAN JOURNAL OF MEDICAL PHYSICS
Year:2009 | Volume:6 | Issue:1 (22)|Papers Count:11

Introduction: Acoustic transient cavitation is the primary mechanism of sonochemical reaction and has potential use for tumor treatment. In this study, the in vivo anti-tumor effect of simultaneous dual-frequency ultrasound at low-level intensity (ISATA < 6 W/cm2) was investigated in a spontaneous murine model of breast adenocarcinoma in Balb/c mice.Materials and Methods: Forty tumor bearing mice were divided into four groups (10 in each group). The treated groups received 15 or 30 minutes of combined dual-frequency ultrasound in continuous mode (1 MHzcon + 150 kHzcon) respectively. The control and the sham groups contained the untreated mice. The tumor growth delay parameters including tumor volume, relative tumor volume, T5 and T2 (the needed time for each tumor to reach 5 and 2 times the initial tumor volume, respectively), survival period and percent of tumor growth inhibition ratio were measured on different days after treatment. Results: The results showed that the 30 min treatment was effective in tumor growth delay and percent of tumor growth inhibitory ratio compared to the sham and the control groups. The tumor volume growth and relative volume of tumors in the same treated group showed an anti-tumor effect relative to the sham and the control groups. There was a significant difference in tumor volume growth between this 30 min treatment group and the sham group 12 days after treatment (p-value <0.05). The mean of the survival period for animals in the 30 min treatment group was 16% more than the control group. The percent of tumor growth inhibition in the 30 and 15 min treatment groups were 23% and 20% respectively, showing a statistically significant difference.Conclusion: Sonodynamic therapy with combined dual–frequency ultrasound in progressive wave mode can be useful in cancer therapy.

Introduction: Diabetic retinopathy (DR) is one of the most serious and most frequent eye diseases in the world and the most common cause of blindness in adults between 20 and 60 years of age. Following 15 years of diabetes, about 2% of the diabetic patients are blind and 10% suffer from vision impairment due to DR complications. This paper addresses the automatic detection of microaneurysms (MA) in color fundus images, which plays a key role in computer-assisted early diagnosis of diabetic retinopathy.Materials and Methods: The algorithm can be divided into three main steps. The purpose of the first step or pre-processing is background normalization and contrast enhancement of the images.The second step aims to detect candidates, i.e., all patterns possibly corresponding to MA, which is achieved using a local radon transform, Then, features are extracted, which are used in the last step to automatically classify the candidates into real MA or other objects using the SVM method. A database of 100 annotated images was used to test the algorithm. The algorithm was compared to manually obtained gradings of these images.Results: The sensitivity of diagnosis for DR was 100%, with specificity of 90% and the sensitivity of precise MA localization was 97%, at an average number of 5 false positives per image.Discussion and Conclusion: Sensitivity and specificity of this algorithm make it one of the best methods in this field. Using the local radon transform in this algorithm eliminates the noise sensitivity for MA detection in retinal image analysis.

Introduction: In clinical electron beams, most of bremsstrahlung radiation is produced by various linac head structures. This bremsstrahlung radiation dose is influenced by the geometry and construction of every component of the linac treatment head structures. Thus, it can be expected that the amount of the contaminated photon dose due to bremsstrahlung radiation varies among different linacs, even for the same electron beam energy. The aims of this study were to simulate the NEPTUN 10PC linac electron beams and to calculate the photon contamination dose due to bremsstrahlung radiation in these beams using a Monte Carlo method. Materials and methods: A NEPTUN 10PC linac was simulated in its electron mode using the BEAMnrc code. This linac can provide three electron beam energies of 6, 8 and 10 MeV. Detailed information required for the simulation, including the geometry and materials of various components of the linac treatment head, was provided by the vender. For all simulations, the cut-off energies for electron and photon transport were set at ECUT=0.521 MeV and PCUT=0.010 MeV, respectively. The KS statistical test was used for validation of the simulated models. Then, relevant bremsstrahlung radiation doses for the three electron beam energies of the linac were calculated for the reference field using the Monte Carlo method. Results: The KS test showed a good agreement between the calculated values (resulting from the simulations) and the measured ones. The results showed that the amount of contaminated photon dose due to bremsstrahlung radiation from various components of the simulated linac at the surface of the phantom was between 0.2%-0.5% of the maximum dose for the three electron beam energies.Conclusion: Considering the good agreement between the measured and simulated data, it can be concluded that the simulation method as well as the calculated bremsstrahlung doses have been made at a good level of accuracy and precision. The results of this study indicate that photon contamination in the NEPTUN 10PC electron beams is not significant. Therefore, it seems that this linac can be used for total skin electron irradiation.

Introduction: Over the last decade, exposure to electromagnetic waves due to base station antennas has increased. This study was planned to evaluate the effects of different electrical field strengths with 950 MHz waves of the GSM mobile phone system on the excitatory postsynaptic potentiation (EPSP) slope of the dentate gyrus long-term potentiation (LTP). Material and Methods: Twenty four naive male Wistar rats (3 months old, weighing 220±15 g) were randomly divided into three groups (sham–exposed, GSM with 50.4 V/m and GSM with 60 V/m electrical field strength). The exposure program was carried out for 10 sessions during 3 days. The animals were exposed to the electromagnetic field for 45 minutes in a plastic chamber. Immediately after the exposure, anesthesia was induced for LTP induction and the field potentials were recorded for 60 minutes, then the EPSP slope and maintenance were analyzed. Results: Our data showed that whole-body exposure to 950 MHz waves of the GSM mobile phone system with 60 V/m electrical field strength could change the EPSP slope in rat brain hippocampus.Discussion and Conclusion: Increasing the electrical field strength could change synaptic plasticity and LTP characteristics in rat brain hippocampus.

Introduction: The human skin is an active medium from the optical point of view. Therefore, the diagnostic and therapeutic techniques employing light are increasing. Current optical techniques are based on the measurement of the intensity of reflected absorbed or backscattered light from or within skin. Studies have shown that biological tissues, and in particular skin, demonstrate polarization properties. Scattering of light from the surface of skin or the layers within it is a function of incident polarization. Therefore, by changing the polarization of the incident light and measuring the backscattered light, we can study those skin properties which affect the state of polarization.Material and methods: We have implemented a scattering ellipsometry system in order to investigate the polarization properties of a phantom representing skin. Using the Stocks vector defining the state of polarization and measuring the elements of the Mueller matrix representing the phantom under study, we have shown that by changing the reflection and scattering properties of the sample, polarization characteristics of the backscattered light will be affected.Results: The results of this investigation showed that some elements of the Mueller matrix of the phantom under study were affected by the polarization state of the incident light and the scattering component within the phantom. Therefore, these elements have the potential of being used as polarization markers of the biological tissue.Discussion and conclusion: Upon interaction of polarized light with the skin tissue, the backscattered light will contain optical and polarization information about the skin. Using a simple laboratory-made phantom, we have shown that by analyzing the polarization information within the backscattered light we can study the cause, and possibly the disease, which affected the polarization characteristics of the skin.

Introduction: Coronary angiography and angioplasty procedures lead to significant radiation exposure of patients. In the current study, the average radiation dose to patients during angiography in the Angiography Department of Shahid-Madani Hospital was determined.Materials and Methods: An image intensifier based angiography unit (Philips BH 3000) was used for angiography procedures. The accuracy of the internal dosimeter was verified. Dose-area products (DAP) of patients (236 cases) during fluoroscopy and cine acquisition were recorded. Analyzing the data, the average radiation doses to patients for angiography and angioplasty and also for fluoroscopy and cine acquisition were determined. Additionally, the average fluoroscopy time for all patients was estimated.Results: The average DAPs of 23.7 and 91.5 Gycm2 were estimated for angiography and angioplasty respectively. Patient doses including fluoroscopy, cine acquisition and the total dose for angiography were 2, 7.7 and 3.8 times lower than angioplasty procedures respectively. Average fluoroscopy time was 1.9 times lower for angiography compared to angioplasty. Discussion and Conclusion: Fluoroscopy time and patient dose during fluoroscopy were in good agreement with other studies. However, the dose to patients during angioplasty was higher compared to other reports. To reduce patient dose in angioplasty procedures, the use of the lowest available frame rate, smallest field size and retraining of operators and technologists are recommended.

Introduction: Laser tissue soldering using albumin and indocyanine green dye (ICG) is an effective technique utilized in various surgical procedures. The purpose of this study was to perform laser soldering of rat skin under a feedback control system and compare the results with those obtained using standard sutures. Material and Methods: Skin incisions were made over eight rats’ dorsa, which were subsequently closed using different wound closure interventions in two groups: (a) using a temperature controlled infrared detector or (b) by suture. Tensile strengths were measured at 2, 5, 7 and 10 days post-incision. Histological examination was performed at the time of sacrifice.Results: Tensile strength results showed that during the initial days following the incisions, the tensile strengths of the sutured samples were greater than the laser samples. However, 10 days after the incisions, the tensile strengths of the laser soldered incisions were higher than the sutured cuts. Histopathological examination showed a preferred wound healing response in the soldered skin compared with the control samples. The healing indices of the laser soldered repairs (426) were significantly better than the control samples (340.5).Conclusion: Tissue feedback control of temperature and optical changes in laser soldering of skin leads to a higher tensile strength and better histological results and hence this method may be considered as an alternative to standard suturing.

Introduction: Virtual bronchoscopy is a reliable and efficient diagnostic method for primary symptoms of lung cancer. The segmentation of airways from CT images is a critical step for numerous virtual bronchoscopy applications.Materials and Methods: To overcome the limitations of the fuzzy connectedness method, the proposed technique, called fuzzy connectivity - fuzzy C-mean (FC-FCM), utilized the FCM algorithm. Then, hanging-togetherness of pixels was handled by employing a spatial membership function. Another problem in airway segmentation that had to be overcome was the leakage into the extra-luminal regions due to the thinness of the airway walls during the process of segmentation. Results: The result shows an accuracy of 92.92% obtained for segmentation of the airway tree up to the fourth generation. Conclusion: We have presented a new segmentation method that is not only robust regarding the leakage problem but also functions more efficiently than the traditional FC method.