International Journal of Radiation Research
Year:2006 | Volume:3 | Issue:4|Papers Count:8

Background: In vivo measurements of applied dose during radiotherapy treatment, is important to ensure accurate dose delivery to patients. Uncertainty in dose delivery should fall within ±5% of the prescribed dose as recommended by ICRU. Assessment of dose for radiotherapy applications performed with various types of detectors. In this study, semiconductor diodes were used which have some advantages for clinical dosimetry.Materials and Methods: The brain tumors have generally treated with two fields using SSD technique. Entrance and exit dose were measured for each patient with diodes during treatment. Entrance and exit dose measurements have converted to midline dose. Measured entrance and exit doses have compared with calculated ones and large deviations (more than 5%) have observed. A farmer ionization chamber (0.6 cm) was used as the reference dose detector and a Perspex water phantom (30|¤|30cm2 area and thickness ranging from 5 cm to 30 cm) were used to determine calibration and correction factors.Results: Correction factors were determined and variations more than 1% have used to obtain correct doses. Large deviations between measured and calculated for entrance (5.3%), exit (42%) and midline (47%) were detected. The difference was not found to be significant when comparing the measured entrance dose with the calculated one (p=0.696) and the measured exit dose with calculated one (p=0.643) and measured midline dose with calculated one (p=0.104).Conclusion: In vivo dosimetry is very useful to check the dose delivered to the patient. A high precision obtained when the calibration and correction factors for each parameter of influence on the diode response are carefully determined and applied to convert the diode signal in the adsorbed dose. In this study, the target-absorbed doses were estimated from the measured entrance dose and the measured transmission.

Background: In order to quantify effects of ultrasound irradiation parameters under therapeutic condition, especially sonodynamic therapy, it is initially necessary to evaluate inertial cavitation activity in vitro conditions; therefore, in this study, the effect of 1 MHz low level ultrasound based on °OH radicals generated by acoustic inertial cavitation in aqueous solution was monitored by their reaction with terephthalic acid (TA) to produce fluorescent 2-Hydroxyterephthalate acid (HTA) by spectrofluorometry method (Terephtalic acid dosimetry). Materials and Methods: The study was designed to measure hydroxyl radicals in a field near to 1 MHz sonotherapy probe in progressive mode and low level intensity. The effect of ultrasound irradiation parameters (1MHz) containing duty factor, mode, intensity ultrasound and, time sonication in hydroxyl radical production have been considered. After preparation of solution of dosimetry and plotting calibration curve of spectrofluorescence, the effect of mode of sonication (continuous and pulsating), duty factor (20-80%), intensity (0-2 W/cm2, with step of 0.5 W/cm2), and sonication time (0-60min with step time of 10min) without increasing temperature to more than 3°C to determine the effective exposure in low level ultrasound were evaluated. The fluorescence intensity of TA solution before and after irradiation, in all cases was measured, and the results were reported as Mean ± Standard Deviation (SD). Results: The result of experiments related to sonication mode for 1MHz ultrasound irradiation (2 W/cm2) show that continuous mode of sonication is 29% higher fluorescence intensity than the pulse mode in 80% duty cycle for sonodynamic therapy. With compensation of irradiation time for 1MHz sonication in different duty cycles, fluorescence intensity in continuous mode is 22% higher than the pulse mode in average. The amount of hydroxyl radicals production versus ultrasound intensity, and sonication time show with increasing intensity or sonication time in continuous mode, the hydroxyl radical production is linearity increased (R=0.99). Conclusion: The results show that the terephthalic acid dosimetry is suitable for detecting and quantifying free hydroxyl radical as a criterion of inertial cavitation production over a range of condition in medical ultrasound fields.  

Background: The essential constituents of cements like lime, silica and alumina are derived from earth's crust in which radioactive elements like uranium, thorium etc are also present in varying amounts almost everywhere. These two elements are considered as the parent elements of uranium and thorium radioactive decay series in which radon and thoron are produced respectively as decay products. In the present study the samples of ordinary Portland cement (OPC), Portland pozzolana cement (PPC) and some other cementious finishing materials like white cement, Plaster of Paris (POP), cement putty etc were collected and analysed for radium and radon concentrations along with radon exhalation rates. Materials and Methods: Alpha sensitive LR-115 Type II plastic track detectors commonly known as "Solid State Nuclear Track Detectors" were used to measure the radium and radon concentration. The alpha particles emitted from the radon causes the radiation damaged tracks. The Chemical etching in NaOH at 60 °C for about 90 minutes was done to reveal these latent tracks, which were then scanned and counted by an optical microscope of suitable magnification. By calculating the track density of registered tracks, the radon and radium concentrations along with exhalation rate of radon, were determined using required formulae. Results: The radon and radium concentration in various brands of cements found to vary from 333 ±9.9 to 506 ±13.3 Bq m-3 and from 3.7 ± 0.1 to 5.6 ± 0.2 Bq kg-1 while in various cementious finishing materials used in the construction, these were found to vary from 378 ±19.7 to 550 ± 9.8 Bq m-3 and from 4.2 ± 0.2 to 6.1 ± 0.1 Bq Kg-1, respectively. Based on the data the mass and surface exhalation rates were also calculated. Conclusion: The measurements indicate that there is marginal variation of the concentration of radium and radon in various brands of cements in India with lower levels in the cement samples having red oxide and higher levels in fly ash based cement samples but overall concentration levels of radon and radium are lower than that of average global values.  

Background: The X-ray machines used for radiodiagnosis should meet certain quality assurance (QA) programmes. These are necessary to have good quality radiographs at reasonably low exposure to patients. Materials and Methods: Dose reduction methods in abdomen X-ray examination were carried out in 10 hospitals in Tehran. This paper presents the work, which was implemented on 200 patients and evaluated using the entrance skin dose (ESD) in the Anterior-Posterior (AP) abdomen projection measured directly at the center of the X-ray field. In addition, the machine room, and dark room parameters, as well as work practices and repeat rates were studied. Results: The quality control (QC) parameters and the ESD were evaluated utilizing an anthropologic phantom to define the optimal exposure condition at all hospitals before and after QC. Results show that after using the QC parameters and optimization of the exposure conditions, the mean of mAs and ESD can be decreased by 62% and 65% respectively. Conclusion: The quality of the radiographs generally increased. The reported method is easily implemented in any clinical situation where optimization of abdomen radiography is necessary.    

Background: While the benefits of Computed Tomography (CT) are well known in accurate diagnosis, those benefits are not risk free. CT is a device with higher patient dose in comparison with other conventional radiological procedures. Is the reduction of exposures by requiring optimization of CT procedures [a principle concern in radiological protection]? In this study, the radiation dose of conventional and spiral CT were investigated and compared with European Commission Reference Dose Levels (EC RDLs). Materials and Methods: The dosimetric quantities proposed in the European Guidelines (EG) for CT are Weighted Computed Tomography Dose Index (CTDIW) for a single slice for axial scanning or per rotation for helical scanning and Dose-Length Product (DLP) for a complete examination. The patient-related data were collected for brain, neck, chest, abdomen and pelvis examinations in each scanner. For each type of examination, 10 typical patients were randomly included. CTDI with an active length of 10cm was measured in two CT scanners by using UNFORS (Mult- O-Meter 601) in head and body phantom (PMMA) with 16 cm and 32 cm in diameter; respectively. Mean values of CTDIW, DLP and Effective Dose(ED) were estimated for those examinations. Results: CTDIW had a range of 15.8-24.7 mGy for brain, 16.1-30.6mGy for neck, 6.8-9.2 mGy for chest, 6.8-9.8 mGy for abdomen and pelvis. DLP had a range of 246.4-397.7 mGy.cm for brain, 104.6-262.2 mGy.cm for neck, 135- 248.4 mGy.cm for chest, 187-298.9 mGy.cm for abdomen and 197.2-319.4 mGy.cm for pelvis. The mean values of effective dose were 0.70 mSv for brain, 1 mSv for neck, 3.2 mSv for chest, 3.3 mSv for abdomen and 5.1 mSv for pelvis. Conclusion: The obtained results in this study have shown that CTDIW and DLP are lower than EC RDLs and other studies, in other words, the performance of all scanners has been satisfactory as far as CTDIw and DLP are concerned. The CTDIW and DLP in the conventional CT are higher than the spiral CT values. With regard to ALARA principle, for the establishment of reference dose levels, the radiation dose with spiral CT scanners should be taken into account.  

Background: The brain response to temporal frequencies (TF) has been already reported, but with no study reported for different TF with respect to various spatial frequencies (SF). Materials and Methods: fMRI was performed by 1.5T GE-system in 14 volunteers during checkerboard, with TFs of 4, 6, 8 and 10Hz in low and high SFs of 0.5 and 8cpd. Results: Average percentage BOLD signal change demonstrated the amplitude of the fMRI response to different TFs was maximal in 6Hz for high SF of 8cpd, while, it was maximal at TF of 8Hz for low SF of 0.5cpd. Conclusion: The results are useful for vision therapy (such as the treatment of Amblyopia) and visual task selecting in fMRI studies.    

Background: PIXE (Particle Induced X-Ray Emission) is a suitable method for the analysis of biological samples in which heavy trace elements are contained in light matrix elements. It is very important to know which factors or probably elements act as initial seed and lead to growing the sands. The goal of this study was to compare the relative values of Fe/K, Cu/K and Zn/K for gallstones, gallbladder, and bile of a specific patient for studying the origination of forming the gallstones.Materials and Methods: Human gallbladder, bile, and gallstone samples were obtained by surgical operation from 15 patients and are bombarded by 2.0 MeV energy proton beams produced by van de Graff accelerator in vacuum. All the gallstones were chosen of pigment type of stones and, all the patients were adults. In contrast with conventional methods, the shell and center of the sands has been analyzed separately. The PIXE spectrum analysis was performed using the nonlinear least square fitting code AXIL and GUPIX. Results: The results of detected minor and trace elements shows that the precipitation of calcium salt in the bile lead to reduction of crystals' formation. Elemental comparison of pigment type of gallstone and bile shows that the concentration of calcium in the shell of the stones is four times more than that in the bile. Conclusion: Precipitation of the calcium from the saturated bile on the cholesterols as a seed of gallstones led to reduced sands formation. Analysis of the gallbladder of the same patients revealed no relation between elemental concentrations of bile and gallstones.    

Gestational Trophoblastic Neoplasm (GTN) is among rare human tumors which can be observed with widespread metastasis. Two young patients with emergent neurologic symptoms with no gynecological problems are presented in this report. GTN was later diagnosed in both cases with brain metastasis. The first case: A 22 years old patient, admitted to the infectious disease ward, with probable diagnosis of Encephalitis. After brain CT scan and measurement of b human chorionic gonadotropin (bhCG), GTN with brain metastasis was confirmed. The second case: A 33 years old patient who underwent craniotomy due to hemorrhagic brain tumor in neurosurgery department. Brain metastatic GTN was confirmed by histological examinations. Both cases received multiagent chemotherapy concurrent with whole brain irradiation of 3000 cGy in 10 fractions (F) within a period of 2 weeks, and chemotherapy was continued for additional course. The patients were both well after about 22 months. Diagnosis of GTN should be considered in any woman of reproductive age.