Diagnostic X-ray Generators Research Articles

의료용 디지털방사선영상의 공간분해능 최적화에 의한 소듐냉각고속로 연료봉 내부의 소듐 충전상태 평가

The purpose of this study was tried to evaluate the filling sodium states inside the fuel rod of sodium-cooled fast reactor by digital medical X-ray. We used the diagnostic X-ray generators in digital radiography (DR). This study have found the optimal conditions by changing the effective focal spot size of X-ray tube and post-processing of the DR method with a tungsten edge plate in order to ensure excellent sharpness At this time, the sharpness and resolution were evaluated using the MTF (modulation transfer function). As a result, this study obtained a spatial resolution of 3.871 lp/mm (0.1 MTF), 3.290 lp/mm (0.5 MTF) when implemented the contrast strengthen post-processing in small focal spot. In this research, the result is able to evaluate the level of sodium inside the fuel rod by using the diagnostic X-ray generators in medical digital radiographic images.

진단용 X선 장치에서 방사선출력의 재현성 평가(IEC 60601-2-54 표준규격을 기반으로)

총 5대를 대상으로 한 진단용X선발생장치(DR)는 IEC 60601-2-54 표준규격에서 제시한 방사선출력의 재현성 시험에서 4대가 적합으로 나타났으며, 다만 1대의 X선 장치에서 C Group의 시험 설정인 진단용X선장치의 최고 관전압의 50%와 관전류 시간 곱(mAs)이 <TEX>$1{\mu}Gy$</TEX>에서 <TEX>$5{\mu}Gy$</TEX> 사이의 인가출력량의 조합으로 측정한 항목에서 부적합으로 나타났다. 이에 따라 방사선량을 정량화하기 위한 표준으로 IEC 60601-2-54 표준규격에서 제시한 방사선출력의 재현성이 진단용 X선 영상장치 성능관리에 중요한 평가 요소임을 인식해야 한다. For five diagnostic X-ray generators (DR), four units turned out to be appropriate in tests on the reproducibility of radiation output suggested in the IEC 60601-2-54 standard, but in one unit of the X-ray equipment, an item measured in a combination of 50% of the highest tube voltage of the diagnostic X-ray equipment, the test setting of Group C with authorized output doses between <TEX>$1{\mu}Gy$</TEX> and <TEX>$5{\mu}Gy$</TEX> of mAs turned out to be inappropriate. As a result, the radiation dose to the IEC 60601-2-54 standard for quantification standards proposed by the radiation output from diagnostic X-ray imaging device reproducibility of performance management should be aware that an important evaluation factor.

진단용 X선 발생장치의 성능 측정

본 연구는 진단용 X선 발생장치의 성능을 검사하기 위해 직선성(Linearity), 재현성(reproducibility) 및 반가층(Half Value Layer; HVL)을 실험하였다. 직선성(Linearity)은 설정된 조사조건으로 한 장비 당 4회씩 조사하여 측정된 선량을 기록하고 mR/mAs를 구하여 측정하였으며, 측정값이 0.1을 초과하면 직선성이 떨어지는 것을 알 수 있다. 재현성(Reproducibility)은 80kVp, 200mA, 20mAs와120kVp, 300mA, 8mAs의 조건으로 10회 조사하여 변동계수(CV) 공식에 대입하여 측정한 값이 0.05안에 포함되면 양호하게 나타나는 것을 알 수 있다. 반가층(Half Value Layer: HVL)은 filter가 없을 때 설정된 조건으로 3회 조사하여 측정한 후 부가필터용 반가층 물질로 사용하여 필터의 두께를 0, 1, 2, 4 mm로 바꾸어 가며 부가필터가 없을 때의 <TEX>$\frac{1}{2}$</TEX>이하인 측정값이 나올 때 까지 측정한다. 현재 본원에서 사용하는 진단용 X선 발생장치 5대를 대상으로 직선성, 재현성, 반가층을 측정한 결과 직선성은 1번 장비에서는 300mA~400mA, 5번 장비에서는 100mA~200mA 부근에서 양호하지 않았으며, 반가층 측정에서는 80kVp 측정치에서 1번 장비에서 검사기준을 만족하지 못하였다. 출력은 단상에 비해 삼상장치가 높게 나왔다. 실험을 통하여 밝혀진 결과를 토대로 정기적인 장비관리와 노후 된 장비의 교환 등이 이루어진다면 장비 사용의 효율성을 극대화 할 수 있으며, 방사선 피폭선량을 줄임과 동시에 영상의 화질을 향상시킬 수 있어 정확한 진단에 기여할 수 있을 것으로 사료된다. To examine the performance of a diagnostic X-ray system, we tested a linearity, reproducibility, and Half Value Layer(HVL). The linearity was examined 4 times of irradiation with a given condition, and we recorded a level of radiation. We then calculated the mR/mAs. And the measured value should not be more than 0.1. If the measured value was more than 0.1, we could know that the linearity was decreased. The reproducibility was analyzed 10 times of irradiations at 80kVp, 200mA, 20mAs and 120kVp, 300mA, 8mAs. The values from these analyses were integrated into CV equation, and we could get outputs. The reproducibility was good if the output was lower than 0.05. HVL was measured 3 times of irradiation without a filter, and we inserted additional HLV filters with 0, 1, 2, 4 mm of thickness. We tested the values until we get the measured value less than a half of the value measured without additional filter. We tested the linearity, the reproducibility, and HVL of 5 diagnostic X-ray generators in this facilities. The linearity of No. 1 and No. 5 generator didn't satisfy the standard for radiation safety around 300mA~400mA and 100mA~200mA, respectively. HVL of No.1 generator was not satisfied at 80kVp. The outputs were higher in the three-phase equipment than the single-phase equipment. The old generators need to maintain and exchange of components based on the these results. Then, we could contribute to getting more exact diagnosis increasing a quality of the image and decreasing an expose dose of radiation.

Calculation of air-kerma rate of diagnostic X-ray generators

As one type of basic physical data related to the calculation of the construction of X-ray examination room shielding, we investigated the air-kerma rate 1 m from the source of the useful beam focus per unit current time product. Compared to the X-ray energy penetration values obtained in prior research, we obtained higher values. We found three causes for this discrepancy: (1) the X-ray tube total filtration (increasing total filtration reduces air kerma), (2) the tube voltage ripple percentage (increased voltage ripple reduces air kerma, and (3) the target angle (increasing the target angle increases the air kerma). On standardizing (1)-(3), we confirmed that our values mostly matched those obtained in past research. Consequently, when one employs the air-kerma rate that results from the consideration of (1)-(3), without pursuing a path of excessive safety, calculation of shielding under clinical conditions is possible.

The practical peak voltage of diagnostic X-ray generators.

A new quantity termed the "practical peak voltage" is proposed. This quantity is derived by equating the low level contrast in an exposure made with an X-ray tube connected to a generator delivering any arbitrary wave form, to the contrast produced by the same X-ray tube connected to a constant potential generator. Out of the great number of possible contrast configurations one is selected as being suitable for diagnostic radiology. By means of an eigenvalue problem a direct link is established between the electrical quantity X-ray tube voltage and the practical peak voltage which was initially defined through the properties of the X-ray field. It is shown that the spread in total X-ray tube filtration as encountered in medical diagnostic radiology can influence the result of a measurement of the practical peak voltage only marginally.

Application of Dynalyzer II to X-Ray Quality Control

The Dynalyzer ll can be used as a troubleshooting aid, or as a calibration tool for diagnostic x-ray generators. The High Voltage Unit can measure anode current and filament current as well as kVp. The Digital Display has features to provide accurate numerical values to these parameters. The operation of the system in typical applications is discussed.

Absolute kilovoltage calibration of a diagnostic x-ray generator.

A method for absolute calibration of diagnostic x-ray generators is presented and discussed. The method employs a Ge(Li) detector and relies on the direct observation of the onset of fluorescence radiation from scattering foils placed in the primary beam.

Kilovoltage measurements on diagnostic X-ray machines with voltage dividers

Discusses the evaluation of ten different voltage dividers used to measure the tube potential of diagnostic X-ray generators. The dividers were tested for ratio accuracy, voltage and temperature coefficients, frequency response and high voltage current leakage. The errors associated with the use of voltage dividers for kVp measurements were examined and a hardware design and methodology to provide minimum error proposed for field testing of X-ray generators.

Determination of kVp of diagnostic X-ray generators

Using a constant potential X-ray generator operated below 50 kV, the kV could be detected by measuring the relative transmission through an absorber. This technique was used on diagnostic X-ray equipment for potentials up to 115 kVp. The ratio for Ho, Au, U and Pb absorbants was determined on a typical full-wave rectified diagnostic machine.

Measurement of Peak Voltage of Diagnostic X-Ray Generators

The measurement of the voltage of diagnostic X-ray generators, using the characteristic radiation emitted by scattering foils, is discussed, and a rigorous definition of the generator voltage which just equals that of the K-absorption edge is put forward. Previous methods of defining this voltage are shown to be either wrong or subject to random variations of up to 10%. Experimental evidence using a scintillation counter and multi-channel analyser is given in corroboration. The use of ionization chambers is also discussed and it is shown that reasonable accuracy (±1%) can be obtained using a single chamber to detect the characteristic radiation.The need for a differential filter of the same material as the scattering foil is considered, and evidence is presented to show that it can be replaced by a primary beam filter of aluminium of suitable thickness for the kilovoltage range under consideration.