Iranian Journal of Medical Physics
Volume:10 Issue: 1, Winter 2012 & Spring 2013

Bladder cancer is the most common malignancy in elderly people and most bladder cancers are transitional cell carcinomas (TCC). Bladder pathology is usually investigated visually by cystoscopy and this technique can represent different conditions ranging from simple inflammation to flat CIS. However, biopsies must be taken from the suspected area to obtain diagnostic information. This is a relatively high cost procedure in terms of both time and money and is associated with discomfort for the patient and increased morbidity. Electrical impedance spectroscopy (EIS), a minimally invasive screening technique, can be used to separate malignant areas from non-malignant areas in the urinary bladder. The feasibility of adapting this technique to screen bladder cancer, and abnormalities during cystoscopy has been explored and compared with histopathological evaluation of urinary bladder lesions. Both ex vivo and in vivo studies were carried out in this study. The impedance data were evaluated in both malignant and benign groups and a significant difference between these two groups was revealed. In all measurements, the impedivity of malignant bladder tissue was significantly higher than the benign tissue, especially at lower frequencies (p<0.001) This technique can be a complimentary method for cystoscopy, biopsy, and histopathological evaluation of the bladder abnormalities.

Abnormal neural impulses in the nervous system may lead to various diseases and disabilities. High frequency alternating currents (HFAC) has been used to block the propagation of such impulses and improve the symptoms or disabilities. The technique is safe, reversible, and relatively selective, and its reliability, the optimum stimulation parameters, and elimination of the onset response have been the focus of related studies in the last decade. In this work, a series of computational simulations were performed to evaluate the performance of asymmetric biphasic rectangular waveforms for HFAC. Computer simulations were carried out in NEURON software based on the MRG model, a detailed model of mammalian peripheral nerve fibers. The current threshold for the block and the injected charge per phase were assess for different forms of this waveform and compared with symmetric rectangular, sinusoidal, DC, and monophasic stimulations. The effect of fiber diameter and the stimulation frequency were also evaluated for this waveform. The threshold charge per phase to induce nerve conduction block was significantly lower for the proposed asymmetric biphasic stimulation. The minimum thresholds were achieved for the waveforms with short anodic long cathodic phases. The threshold was reduced with increasing the asymmetry of the waveform and reduction of the frequency. Simulations performed in this study demonstrated that the proposed stimulation with asymmetric biphasic rectangular waveforms significantly reduces the current threshold and requires much less charge injection per phase to induce nerve conduction block. This is very important for clinical use due to less damage to the tissue.

Cold plasma is a self-sterilized, painless, and non-contact method in surgeries. These properties allow it to be applied to the living tissues and heat-sensitive parts. The aim of this study was to design a new cold plasma producer device and evaluate the effects of cold argon plasma on decreasing the coagulation time of blood drop in vitro and that of the injured liver blood in vivo. In an experimental study, two blood drops of a normal healthy human were placed on a glass slide. The experimental sample was irradiated by plasma until the complete coagulation occurred, while the control sample remained intact. The complete coagulation time was then measured for both samples. In another part of our study, 20 rats were divided into two experimental and control groups and anesthetized for experimentation. Livers of the rats in the control group were incised and the bleeding time was measured until complete coagulation. Livers of the experimental rats were irradiated by plasma after being incised, and the complete coagulation time was measured. Cold plasma treatment increased the speed of blood coagulation in both blood drop in vitro and the injured liver blood.in vivo. Histopathological examinations revealed that plasma treatment caused no significant tissue damages as compared with the control group. The use of argon plasma coagulation device at the time of surgery, in addition to accelerating blood coagulation, caused no injury and burning on tissues. Plasma increases the platelets activation, fibroblasts proliferation and fibrin production. the mechanism of action is likely mediated by exogenous nitric oxide.

The main goal of this study was to perform quality control test on all radiography units operating in Golestan province of IRAN. Forty-four X-ray units were examined based on general accepted programs for quality control. Eight parameters including kVp accuracy, kVp reproducibility, mA-time reciprocity, exposure linearity, exposure reproducibility, timer accuracy, filtration, and beam alignment were measured and calculated. Measurements were carried out by a Baracuda X-ray beam analyzer. Variance of kVp reproducibility was acceptable in 100% of equipments. kVp accuracy was found to be unsatisfactory in 29.5% of equipments. Variance of mA-time reciprocity was measured to be within reliable limits. Thirty-nine percent of radiography equipments showed non-linear exposure attitude while 16.7 % of them exhibited unacceptable reproducibility of exposure. Moreover, beam misalignment was met in 29.5% of equipments. In 43.2% of radiography equipments, timer accuracy was out of permissible range. Timer inaccuracy seems to be a common problem for X-ray units. Exposure non-linearity, mA-time non-reciprocity, kVp inaccuracy, beam misalignment, and finally non-reproducibility of exposure were found to have less importance.

Radon is a colorless and tasteless gas which exists in most soils. It is a substance that poses a potential risk for lung cancer in case a person is exposed to high levels over long periods of time. The Environmental Protection Agency (EPA) estimates that 90% of lung cancers per year are caused by radon. The aim of this paper is to estimate the absorbed doses of 222Rn by MCNPX simulation in single-mode optical fiber (SMF) as a method proposed for dosimetry test. To calculate the absorbed dose of 222Rn in SMF using MCNPX-2.6 code, the *F6 tally was applied. SMF was simulated by being exposed to radon while being located in the axis of the pipe. The absorbed doses due to beta, gamma, and alpha radiations emitted from radon in SMF obtained by Monte Carlo simulations were equal to 5.76311E-13, 5.06973E-15, and 4.83457E-14Gy/particle, respectively. Therefore, the total absorbed dose for radon in SMF was in the order of 6.29727E-13 Gy/particle. The MCNPX outputs are always normalized to one source particle. Therefore to calculate the absorbed dose in various radon concentrations, this result must be multiplied to the number of source particles in active volume around the SMF. The daily radon absorbed dose in a one-meter of SMF and 1 kBq/m3 radon concentration is about 0.017 mGy which is in a dose range of TLD dosimeters. The results show that the SMF can be regarded as a radon dosimeter and may be used for beta-particles dosimetry.

Radiotherapy planning systems require many percentage depth dose (PDD) and profile measurements and there are various dosimeters that can be used to obtain these scans. As dose perturbation is particularly troublesome in smaller photon fields, using a low-perturbation, unshielded electron field diode (EFD) in these fields is of interest. The aim of this work was to investigate the suitability of an unshielded diode for beam scanning in 3×3 cm2, 5×5 cm2, and 10×10 cm2, 6 MV fields. An EFD was used for all the scans. For comparisons in profile measurements, a tungsten-shielded photon field diode (PFD) was also used. PDDs were measured using the PFD and an RK ionization chamber. Very good agreement (0.4%) was found between the PDDs measured with EFD and PFD for the two larger fields. However, the difference between them exceeded 1.0% slightly for the smallest field, which may be attributed to the effect of the larger PFD perturbation. The RK chamber PDDs around 10 cm depth were 1-2% lower than those measured with the diodes. There was good agreement ( The EFD generally agrees well with the PFD and may even perform better in smaller fields.

Contrast-enhanced fluid-attenuated inversion recovery (FLAIR) is one of the MRI sequences that can be used for detection and evaluation of pathological changes in the brain. In this work, we have studied the effect of different echo times (TE) on the maximum relationship between signal intensity and concentration of the contrast agent using the FLAIR sequence. For assessment of the relationship between signal intensity (SI) and concentration, a water-filled phantom containing vials of different concentrations of Gd-DTPA (0 to 19.77 mmol/L) was used. The mean SI was obtained in the region of interest when T1-weighted images were implemnted. The SI was corrected for coil non-uniformity. This study showed that an increase in TE is associated with a decrease in the maximum relationship between SI and concentration. TE is an important parameter when the SI is measured in clinical FLAIR studies. The concentration leading to a maximum SI depends on this parameter, with the relevant concentration range decreasing at high TE.

SPECT projections are contaminated by scatter radiation, resulting in reduced image contrast and quantitative errors. Backscatter constitutes a major part of the scatter contamination in lower energy windows. The current study is an evaluation of the effect of backscatter material on FWHM and image quality investigated by Monte Carlo simulation. SIMIND program was used for simulation of a Siemen’s dual-head variable angle scintillation gamma camera. Planar and SPECT scanning of a 99mTc source and a Jaszczak phantom for varying thicknesses of Perspex slabs, as a backscatter media, were analyzed using the photopeak and scatter windows. Simulated planar images and reconstructed tomographic images were evaluated qualitatively, by two nuclear medicine specialists, and quantitatively, by Structural Similarity (SSIM) Index. In the 99mTc photopeak window, no significant change in total counts due to backscatter material was measured. In the scatter windows, scattering was overestimated compared with a simulated backscatter free SPECT system. For instance, at a thickness of 10 cm, total counts of a 99mTc source detected in the 72 keV windows eventually doubled with increasing backscatter material, compared with the situation without backscatter material. The backscatter contribution plateaued when more than 7 cm of scatter material was placed but there were optimized results for a backscatter thickness of 4.5 cm. Better image quality for the thickness was confirmed by the results of eye interpretation and also by SSIM algorithm. Backscatter should be taken into account, particularly in model-based scatter correction methods in SPECT for an accurate simulation system optimization.