To acquire good image quality and to minimize unnecessary radiation dose to patients, it is important to ensure that the radiopharmaceutical administered is accurately measured. Quality control of radionuclide calibrators should be performed to achieve these goals. The purpose of this study is to support the quality control of radionuclide calibrators in nuclear medicine centers and to investigate the level of measurement accuracy of the radionuclide calibrators. 58 radionuclide calibrators from 45 nuclear medicine centers, 74 radionuclide calibrators from 58 nuclear medicine centers, and 60 radionuclide calibrators from 45 nuclear medicine centers were tested with I-131, Tc-99m and I-123, respectively. The results showed that 81% of calibrators for I-131, 61% of calibrators for Tc-99m and 67% of calibrators for I-123 were within +/-5%. 17% of calibrators for I-131, 20% of calibrators for Tc-99m and 15% of calibrators for I-123 had a deviation in the range 5%<|delta|< or =10%. 2% of calibrators for I-131, 19% of calibrators for Tc-99m and 18% of calibrators for I-123 had a deviation of |delta|>10%. Follow-up measurements were performed on the calibrators whose error exceeded the +/-10% limit. As a result, some of the calibrator showed an improvement and their deviation decreased below the +/-10% limit. The results have shown that such comparisons are necessary to improve the accuracy of the measurement and to identify malfunctioning radionuclide calibrators.
Dietary Sucrose ; Follow-Up Studies ; Humans ; Nuclear Medicine ; Quality Control ; Radioactivity

Scatter radiation considerably affects radiographic image quality by reducing image contrast and contributing to a non-uniform background. Images containing a large portion of scatter radiation may result in an incorrect diagnosis. In the past few years, many efforts have been made to reduce the effects of scatter radiation on radiographic images. The purpose of this study is to accurately measure scatter fractions and evaluate the effectiveness of beam-stop arrays. To measure scatter fraction accurately, a beam-stop array and the SFC (Scatter Fraction Calculator) program were developed. Images were obtained using the beam-stop array for both an anti-scatter technique with an anti-scatter grid and an air gap technique. The scatter fractions of the images were measured using the SFC program. Scatter fractions obtained with an anti-scatter grid were evaluated and compared to scatter fractions obtained without an anti-scatter grid. Scatter fractions were also quantitatively measured and evaluated with an air gap technique. The effectiveness of the beam-stop array was demonstrated by quantifying scatter fractions under various conditions. The results showed that a beam-stop array and the SFC program can be used to accurately measure scatter fractions in radiographic images and can be applied for both developing scatter correction methods as well as systems.
Radiographic Image Enhancement

In this study, we evaluated the dose response of MAGAT (Methacrylic Acid Gelatin gel and THPC) normoxic polymer gel dosimeters based on the X-ray CT scanner. To perform this study, we determined the proper ratio of the gel composition and acquired X-ray scan parameters. MAGAT gel dosimeters were manufactured using MAA (MethacrylicAcid) and gelatin of various concentration, irradiated up to 20 Gy. We obtained the 20 CT images from the irradiated gel dosimeters by using on a Phillips Brilliance Big Bore CT scanner with the various scan parameters. This CT images were used to determine the N(CT)-dose response, dose sensitivity and dose resolution As an amount of MAA and gelatin were increase, the slope and intercept were increase in each MAGAT gel dosimeter with various concentration of the N(CT)-dose response curve. The dose sensitivity was 0.38+/-0.08 to 0.859+/-0.1 and increased were amount of the MAA was increased or the gelatin was decreased. However, the change of gelatin concentration was very small compare to MAA. The Dose resolution (D(delta)(95%)) varies considerably from 2.6 to 6 Gy, dependent on dose resolution and CT image noise. The slope and dose sensitivity was almost ident verywith the variation of the tube voltage, tube current and slice thickness in the dose response curve, but the noise (standard deviation of averamalg CT number) was decreased when the tube voltage, tube current and slice thickness are increase. The optimal MAGAT polymer gel dosimeter based on the CT were evaluated to determine the CT imaging scan parameters of the maximum tube voltage, tube current and slice thickness (commonly used in clinical) using the composition ratio of a 9% MAA, 8% gelatin and 83% water. This study could get proper composition ratio and scan parameter evaluating dose response of MAGAT normoxic polymer gel dosimeter using CT scanner.
Gelatin ; Noise ; Polymers ; Tomography Scanners, X-Ray Computed ; Water

The aim of this study is to suggest the method for image enhancement of digital chest radiograph and evaluate clinically the quality of the resultant image. A nonlinear iterative filter was developed in order to reduce quantum noise preserving edge. Dynamic range was adjusted and adaptive image enhancement was performed based on the property of anatomic region and the degree of compatibility with neighboring pixels. The lung fields were enhanced appropriately to visualize effectively vascular tissue, bronchus and lung tissue with the desired mediastinum enhancement. Clinic evaluation was performed by three radiologists with at least 8 years experience. The anatomic regions of 11 in PA and 9 in Lateral were observed carefully in each 100 radiographs according to ITU (International Telecommunication Union) recommendation 500 protocol. The result showed the mean 3.4 between good and adequate. This means that the clinical utility of the image quality is enough. In this study, image enhancement was carried out considering image display device and human perceptual system to prevent the loss of useful anatomic information. In order to increase the diagnostic accuracy in digital radiograph, the continuous study on image enhancement is needed.
Bronchi ; Humans ; Image Enhancement ; Lung ; Mediastinum ; Noise ; Telecommunications ; Thorax

The Monte Carlo method cannot have been used for routine treatment planning because of heavy time consumption for the acceptable accuracy. Since calculation time is proportional to particle histories, we can save time by decreasing the number of histories. However, a small number of histories can cause serious uncertainties. In this study, we proposed Monte Carlo dose computation time and uncertainty reduction method using specially designed filters and adaptive denoising process. Proposed algorithm was applied to 6 MV photon and 21 MeV electron dose calculations in homogeneous and heterogeneous phantoms. Filtering time was negligible comparing to Monte Carlo simulation time. The accuracy was improved dramatically in all situations and the simulation of 1% to 10% number of histories of benchmark in photon and electron dose calculation showed the most beneficial result. The empirical reduction of necessary histories was about a factor of ten to fifty from the result.
Monte Carlo Method ; Uncertainty

In total body irradiation (TBI) for leukemia, we have a two methode. One is a AP (anterior-posterior) method and the other is a Lateral methode. Our hospital used lateral methode. TBI must consider about body contour, because of homogeneous dose distribution. For compensation about irregular body contour, we use compensator. For TBI treatment, we must be considered, accurate manufacture of compensator and accurate calculation of dose. We developed the automatic program for TBI. This program accomplished for compensator design and dose calculation for irregular body. This program was developed for uses to use in a windows environment using the IDL language. In this program, it use energy data for each energy: TMR, output factor, inverse square law, spoiler, field size factor. This program reduces the error to happen due to the manual. As a development of program, we could decrease the time of treatment plan and care the patient accurately.
Compensation and Redress ; Humans ; Jurisprudence ; Leukemia ; Whole-Body Irradiation*

The first step in the commissioning procedure of a treatment planning system is always verification of the basic beam data. In this work, we have measured PDD curves and beam profiles between 1x1 cm2 and 40x40 cm2. In an attempt, Pinnacle 7.4f detect discrepancies between predicted dose distribution and delivered dose distribution. The discrepancies between measurement data and caculation data was found. The delivered dose was underestimated in field but overestimated out of field. The Dmax depth of 1x1 cm2 was reduced about 2 mm. For the larger field size (> or = 4x4 cm2), the beam profile and PDD curve showed good agreement between measurement data and calculation data.

Absorbed dose dosimetry protocols of high energy photon and electron beams, which are widely used and based on an air kerma calibration factors, have somewhat complex formalism and limitations for improving dosimetric accuracy due to uncertainty of the physical parameters used. Recently the IAEA and the AAPM published the absorbed dose to water-based dosimetry protocol. In this work web-based dose calibration program for IAEA TRS-398 and AAPM TG-51 protocols were developed. This program developed using the Visual C# language can be used in the internet. User selectable dosimetry protocol on the web allows the absorbed dose to water data of the two protocols at a reference point to be easily compared, and enables to conveniently manage and understand the current status of the dosimetry calibration performed at participating institutions in korea. This program and the resultant database from the web-based calibration can be useful in developing new dosimetry protocols in Korea.
Calibration* ; Internet ; Korea ; Uncertainty ; Water

We have designed the multi channel detector for the quality assurance of clinical photon beams. The detector was composed of solid phantom inserted by six plane-parallel ionization chambers at different depth. The chamber as a mini plane parallel chamber was made of carbon coated microfilms. In this study the electrical characteristics of the six chambers in the solid phantom were evaluated using 6 MV photon beam. The leakage currents were less than 0.5 pA, reproducibility was less than 0.5%, linearity was less than 0.5%, and dose rate effect was less than 0.7%. In addition the effect of dose variation from other chambers was estimated to maximum 0.8% approximately. The developed detector can be used for quality determination in output dosimetry or measurement of percentage depth dose approximately for clinical photon beam.
Carbon* ; Electrodes*

A thermal neutron beam facility utilizing a typical tangential beam port for Neutron Capture Therapy was installed at the HANARO, 30 MW multi-purpose research reactor. Mixed beams with different physical characteristics and relative biological effectiveness would be emitted from the BNCT irradiation facility, so a quantitative analysis of each component of the mixed beams should be performed to determine the accurate delivered dose. Thus, various techniques were applied including the use of activation foils, TLDs and ionization chambers. All the dose measurements were performed with the water phantom filled with distilled water. The results of the measurement were compared with MCNP4B calculation. The thermal neutron fluxes were 1.02E9 n/cm2 s and 6.07E8 n/cm2 s at 10 and 20 mm depth respectively, and the fast neutron dose rate was insignificant as 0.11 Gy/hr at 10 mm depth in water. The gamma-ray dose rate was 5.10 Gy/hr at 20 mm depth in water. Good agreement within 5%, has been obtained between the measured dose and the calculated dose using MCNP for neutron and gamma component and discrepancy with 14% for fast neutron flux. Considering the difficulty of neutron detection, the current study support the reliability of these results and confirmed the suitability of the thermal neutron beam as a dosimetric data for BNCT clinical trials.
Fast Neutrons ; Neutron Capture Therapy* ; Neutrons* ; Relative Biological Effectiveness ; Water