Exposure Time Accuracy Research Articles

First implementation of quality control procedures on selected X-ray machines in South of Benin

Abstract Introduction: The use of X-ray equipment for medical diagnostic radiography procedures has increased due to advances and complexity of radiological procedures. Achieving good image quality while keeping exposure of workers, public and patient exposure to an acceptable level has become a prerequisite for the radiology department in order to comply with best international practices. The aim of this study was to undertake quality control measurement of seven (7) diagnostic radiography equipment in the south of Benin, the first of its kind. Material and methods: Multifunction detector (Piranha) and beam alignment test tool were used to perform quality control tests on seven (7) X-ray units. The method used as well as the interpretation of the results was based on the American Association of Physicists in Medicine (AAPM), United States Food and Drug Administration (FDA), Healing Arts Radiation Protection (HARP), Institute of Physics and Engineering in Medicine (IPEM), International Atomic Energy Agency (IAEA) and Canadian Safety code 35 (S.C 35) recommendations. Results: The quality control results showed that all X-ray equipment investigated were within standard limits for accuracy of exposure time below 10 ms; reproducibility of kVp, exposure time and dose output; specific dose-kVp2 linearity; and specific dose-mAs linearity. Five (5) out of seven (7) diagnostic X-ray machines passed quality control tests such as X-ray beam alignment, exposure time above 10 ms and kVp accuracy. One (1) X-ray machine failed the quality control test of beam filtration at 70 kVp and above. Conclusions: The findings of this study have provided baseline data for other radiology departments to embark on similar QA/QC activities, and also explore options for optimization of patient dose. However, there is a need to extend the study to cover more diagnostic X-ray machines throughout the country. It is anticipated that this would ultimately assist in improving radiation protection and safety during medical diagnostic radiological procedures.

Pelaksanaan Quality Control Pesawat Sinar X di Pelayanan Radiodiagnostik

Background: Quality Control can be used as a monitoring of the reliability of X-Ray Unit during the validity period of the Conformity Test Certificate. During the use of X-ray Unit, there is the potential for damage to components during the validity period of the certificate of passing the Compliance Test. If the X-Ray Unit Reliability Test is only carried out during the Compliance Test, then if there is a decrease in the quality and safety of the X-ray Unit it cannot be immediately known. This has the potential to endanger patients, radiation workers and the public. In Banyumas Regency, there are 80 Radiation Source Utilization Permits spread across 34 radiodiagnostic installation. Preliminary studies show that not all radiodiagnostic installation carry out routine X-ray machine reliability tests according to the Keputusan Menteri Kesehatan Republik Indonesia Nomor 1250/Menkes/SK/XII/2009 Tentang Pedoman Kendali Mutu (Quality Control) Peralatan Radiodiagnostik.
 Method: This research type is qualitative with survey of 20 radiodiagnostic installation using a questionnaire instrument. Quality control conducted periodically includes kVp accuracy test, linearity and reproducibility mA, exposure time accuracy test, tube leak test, collimator beam suitability test, collimator shutter efficiency test, collimator light strength test, HVL measurement, implementation of reject analysis program and availability and qualifications of quality control officers and availability of quality control equipment. Then the data will be grouped based on research objectives and presented descriptively.
 Result: From the results of data collection, 1 hospital did not have a quality control officer and 4 hospitals had a quality control officer with an educational background of Diploma IV in Radiology Engineering without any Radiology Equipment Quality Control training. Meanwhile, 15 hospitals have quality control officers with an educational background in the Medical Physics Undergraduate Program and have attended training in Quality Control of Radiology Equipment. Of the 20 hospital radiology installations, there were 7 hospitals that did not carry out the Reject Analysis Program. This was done with the assumption that Digital Radiography had been used in both the CR and DR modalities. A number of 13 hospitals continued to carry out the Reject Analysis Program even though they had used Digital Radiography. Of the 20 hospital radiology installations, there are 6 hospitals that independently carry out X-ray unit testing within the framework of a quality control program. However, only 1 hospital conducts regular testing. Testing is also limited to the accuracy of the collimator field and the strong light of the collimator. Fourteen hospitals did not carry out a quality control program independently but only carried out an X-ray unit calibration test once a year which was carried out by BPFK and an X-ray unit distributor company.
 Conclusion: The implementation of quality control of x-ray machines on a regular basis has not been carried out by all radiodiagnostic services, even though they already have quality control officers. One of the reasons is the availability of quality control equipment needed for testing and supervision of radiodiagnostic service management. The role of management of radiodiagnostic services is needed to overcome these problems.
 
 Keyword : Quality Control Programe, Compliance Test, X-Ray Unit

Performance Evaluation of Diagnostic X-Ray Equipment Regarding the Hospital Size in the Republic of Korea

Introduction: The Republic of Korea has developed a national standard based on which diagnostic X-ray equipment must be tested every 3 years. Accordingly, the performance of X-ray equipment used in all hospitals is evaluated by national certification bodies in compliance with the safety management regulations for X-ray equipment. However, if the equipment is non-compliant, its use must be stopped until it satisfies the accepted standards. Material and Methods: In compliance with the safety management regulations for diagnostic X-ray equipment, hospitals in this study were divided into two groups, namely the general hospital group and the clinic group with diagnostic X-ray equipment. The samples in this study were composed of 11 and 18 machines selected randomly from general hospitals and clinics, respectively, which satisfied the acceptance standards since last year in both groups. The evaluation of diagnostic X-ray machines was based on the results obtained from X-ray tube voltage, tube current, exposure time accuracy, and the X-ray dose reproducibility. Results: The X-ray machines of the general hospital group followed all national standards. However, those of the clinic group failed to satisfy the requirements of tube voltage, tube current, exposure time accuracy, and X-ray dose reproducibility. Conclusion: Clinics require their own quality control to reduce unnecessary medical radiation exposure due to the poor X-ray equipment performance. Moreover, it is suggested that the test period of the safety management regulations on diagnostic X-ray equipment need to be shorter than three years.

Quality assessment of conventional X-ray diagnostic equipment by measuring X-ray exposure and tube output parameters in Great Khorasan Province, Iran

Introduction: Regular implementation of quality control (QC) program in diagnostic X-ray facilities may affect both image quality and patient radiation dose due to the changes in exposure parameters. Therefore, this study aimed to investigate the status of randomly selected conventional radiographic X-ray devices installed in radiology centers of Great Khorasan Province, Iran, to produce the data needed to formulate QC policies, which are essential to ensure the accuracy of the diagnosis while minimizing the radiation dose. Material and Methods: This cross-sectional study was performed using a calibrated Piranha multi-purpose detector to measure QC parameters in order to unify X‐ray imaging practices using international guidelines. The QC parameters included voltage accuracy, voltage reproducibility, exposure time accuracy, exposure time reproducibility, tube output linearity with time andmilliampere (mA), and tube output reproducibility. Data analysis procedures were performed based on the type of an X-ray generator, which has not been reported in previous studies. Results: The results showed that the implementation of high-frequency X-ray generators were more advantageous compared to alternative current generators, due to their efficient, better accuracy, linearity, and reproducibility. Conclusion: The survey revealed that the QC program was not conducted at regular intervals in some of the investigated radiology centers, mostly because of inadequate enforcement by national regulatory authorities for implementation of QC program.

Quality Control Assessment of Conventional Radiology Devices in Iran

Introduction Quality control (QC) techniques are used in monitoring and maintenance of the components of an x-ray system. QC of radiology devices plays a significant role in reduction of medication dose and optimization of image quality. This study aimed to conduct QC tests on randomly selected radiology devices, installed in diagnostic imaging departments of Iran. Materials and Methods In total, quality control tests were conducted on 51 conventional radiology devices installed in 20 cities of Iran in order to assess the accuracy of peak kilovoltage (kVp), exposure time, exposure linearity and reciprocity, reproducibility of exposure and determination of half-value layer (HVL) using a calibrated Mult-O-Meter. Results In this study, 38.6% of devices had intolerable variance of kVp accuracy. The results of 34.5% of devices were out of the acceptable limits in exposure time accuracy test. In 46.7% and 53.1% of devices, variance was greater than the acceptable range for exposure linearity and exposure reciprocity, respectively. In terms of reproducibility of exposure test, the reproducibility variance and percentage of tube output variations in 19.4% of devices exceeded the limits. Moreover, the thickness of first HVL was lower than the acceptable limit in 14.7% of devices. Conclusion According to the results of this study, there were wide variations in QC test results, perhaps mainly due to the fact that it is not an obligation to implement QC programs in Iran. The most important problems were non-reciprocity of exposure, nonlinearity of exposure with milliampere-second (mAs), kVp and timer inaccuracy. Involvement of medical physicists, radiologists and radiographers in the implementation of QC programs at various stages of development, installation and use of equipment should enable the gradual improvement in equipment performance.

Quality Control of Conventional Radiology Devices in Selected Hospitals of Khuzestan Province, Iran

Introduction Quality control techniques used to test the components of the radiological system and verify that the equipment is operating satisfactorily. In this study, quality control (QC) assessment of conventional radiology devices was performed in frequently visited radiology centers of Khuzestan province, Iran. Materials and Methods Fifteen conventional radiology devices were examined, based on the protocol proposed in Report No. 77 by the Institute of Physics and Engineering in Medicine (IPEM). Ten standard QC tests, including voltage accuracy and reproducibility, exposure time accuracy and reproducibility, tube output linearity (time and milliampere), filtration (half-value layer), tube output (70 kV at FSD =100 cm), tube output reproducibility and beam alignment were performed and assessed. All measurements were performed, using Barracuda multi-purpose detector. Results The reproducibility of voltage, exposure time and dose output, as well as output linearity, met the standard criteria in all devices. However, in 60% of the units, the results of the beam alignment test were poor. We also found that 66.7% of the studied units offer services to more than 18,000 patients annually or 50 patients per day. Conclusion Despite the fact that radiological devices in Khuzestan province are relatively old with high workload, the obtained results showed that these devices met the standard criteria. This may be mainly related to proper after-sale services, provided by the companies. Although these services may be expensive for radiology centers, the costs may be significantly reduced if QC is defined as a routine procedure performed by qualified medical physicists or radiation safety officers.

The Evaluation of Conventional X-ray Exposure Parameters Including Tube Voltage and Exposure Time in Private and Governmental Hospitals of Lorestan Province, Iran

Introduction In radiography, dose and image quality are dependent on radiographic parameters. The problem is caused from incorrect use of radiography equipment and from the radiation exposure to patients much more than required. Therefore, the aim of this study was to implement a quality-control program to detect changes in exposure parameters, which may affect diagnosis or patient radiation dose. Materials and Methods This cross-sectional study was performed on seven stationary X-ray units in sixhospitals of Lorestan province. The measurements were performed, using a factory-calibrated Barracuda dosimeter (model: SE-43137). Results According to the results, the highest output was obtained in A Hospital (M1 device), ranging from 107×10-3 to 147×10-3 mGy/mAs. The evaluation of tube voltage accuracy showed a deviation from the standard value, which ranged between 0.81% (M1 device) and 17.94% (M2 device) at A Hospital. The deviation ranges at other hospitals were as follows: 0.30-27.52% in B Hospital (the highest in this study), 8.11-20.34% in C Hospital, 1.68-2.58% in D Hospital, 0.90-2.42% in E Hospital and 0.10-1.63% in F Hospital. The evaluation of exposure time accuracy showed that E, C, D and A (M2 device) hospitals complied with the requirements (allowing a deviation of ±5%), whereas A (M1 device), F and B hospitals exceeded the permitted limit. Conclusion The results of this study showed that old X-ray equipments with poor or no maintenance are probably the main sources of reducing radiographic image quality and increasing patient radiation dose.

Quality control assessment of diagnostic X-ray facilities in Ghana

Twenty-three X-ray machines located at 20 different hospitals in Ghana were assessed for quality assurance and control. The radiographic parameters evaluated were tube voltage and current, tube output consistency variation with kilovoltage (kV) and current-time (mAs) factor, exposure time accuracy and beam quality as measured by half-value layer. The photographic parameters assessed were type of films, level of film fogging, film speed, contrast index and film processing temperature. Twenty two of the machines were ~ 99 % output consistency with standard kVp and mAs. Twelve of the machines had output linearity deviation of less than the acceptable 5 %, while 22 machines were within the accepted kVp deviation of 5 %. The film processing temperature at most hospitals exceeded the required level, due to the absence of air conditioners in the darkrooms. The darkroom quality control at all the facilities was very high. Fogging of films was minimal as indicated by the Base + Fog value of 0.3, speed index of film was ~ 1.65 and contrast index was comparable to the acceptable value of 1.5. The level of timer accuracy was greater than 95 % for all the X-ray machines with the exception of one. The general quality control status of all the X-ray machines and darkrooms assessed were acceptable and within the quality assurance standards.

Performance evaluation of a CyberKnife® G4 image-guided robotic stereotactic radiosurgery system

The aim of the current work was to present the performance evaluation procedures implemented at our department for the commissioning of a G4 CyberKnife system. This system consists of a robotic manipulator, a target-locating system and a lightweight 6-MV linac. Individual quality assurance procedures were performed for each of the CyberKnife subsystems. The system was checked for the mechanical accuracy of its robotic manipulator. The performance of the target-locating system was evaluated in terms of mechanical accuracy of both cameras' alignment and quality assurance tests of the x-ray generators and the flat-panel detectors. The traditional linac 6-MV beam characteristics and beam output parameters were also measured. Results revealed a manipulator mechanical mean accuracy of ∼0.1 mm, with individual maximum position uncertainties less than 0.25 mm. The target-locating system mechanical accuracy was found within the acceptance limits. For the most clinically used parameters in the CyberKnife practice, e.g. 100–120 kV and 50–200 ms, kV and exposure time accuracy error were measured as less than 2%, while the precision error of the kV was determined as less than 1%. The acquired images of the ETR grid pattern revealed no geometrical distortion while the critical frequency f50 values for cameras A and B were calculated as 1.5 lp mm−1 and 1.4 lp mm−1, respectively. Dose placement measurements were performed in a head and neck phantom. Results revealed sub-millimeter beam delivery precision whereas the total clinical accuracy of the system was measured equal to 0.44 ± 0.12 mm, 0.29 ± 0.10 mm and 0.53 ± 0.16 mm for the skull, fiducial and Xsight spine tracking methods, respectively. The results of this work certify the G4 CyberKnife SRS system capable of delivering high dose distributions with sub-millimeter accuracy and precision to intracranial and extracranial lesions. Moreover, total clinical accuracy of the investigated G4 system was found to be improved for the skull and fiducial tracking methods and was comparable for Xsight spine tracking method compared with the earlier generation of the instrument.

Dental radiology dosimetric data as routinely collected in an Italian hospital

The work presented here was developed in the framework of the SENTINEL Project and is devoted to the analysis of dental radiology dosimetric data. The procedure of data processing allows the analysis of some important aspects related to the protection of the patient and the staff because of the position of the operators near the patient and their exposure to the radiation scattered by the patient. Dental radiology data was collected in an Italian hospital. Following the Italian quality assurance (QA) protocols and suggestions by the leaders of the SENTINEL Project, X-ray equipment performances have been analysed in terms of: kVp accuracy, exposure time accuracy and precision, tube output, dose reproducibility and linearity, beam collimation, artefacts and light tightness. Referring to these parameters the physical quality index (QI) was analysed. In a single numerical value between 0 and 1, QI summarises the results of quality tests for radiological devices. The actual impact of such a figure (as suggested by international QA protocols or as adopted by local QA routine) on the policy of machine maintenance and replacement is discussed.

Performance of medical radiographic X-ray systems in Greece for the time period 1998–2004

This study presents the results of the on-site inspections performed by the Greek Atomic Energy Commission (GAEC) on conventional X-ray systems, both in public and private medical radiology departments. A part of the inspection concerns the assessment of important radiographic parameters obtained according to a specified quality control protocol and the comparison of the measured parameter values with the corresponding acceptance limits. A total number of 1011 radiographic systems were inspected by the GAEC during the period 1998–2004, with 63.4% of them being privately owned. Analysis of 8 different operational parameters is carried out providing information on the overall performance, as well as on each parameter of the inspected X-ray systems. Tube voltage reproducibility values show the highest percentage of acceptability (98.9%, 99.5% for private and public owned radiographic systems respectively), while linearity of radiation output for private systems (72.5%) and time accuracy for public ones (72.7%) show the worst results. The comparison of the results for the private sector to those of a similar study carried out during the period 1995–1997 indicates a substantial improvement in X-ray systems performance. Higher level of improvement shows exposure time accuracy (12.2% percentile increase) and linearity of radiation output (12.5% percentile increase). Nevertheless, the situation can be further optimized if maintenance and quality control of the radiographic systems are carried out on a more regular basis.

Interlaboratory comparison and accreditation in quality control testing of diagnostic X-ray equipment

The University of Tartu provides a quality control service to the majority of diagnostic X-ray departments in Estonia. Its methodology has been adopted from the IEC and other relevant standards. Recently the Testing Centre of the University of Tartu was accredited on this methodology by ISO/IEC 17025. Besides the implementation of the quality management system, participation in interlaboratory comparison (ILC) was one of the prerequisites for the accreditation. Tests for estimating reproducibility of tube voltage and dose rate, accuracy of the voltage and accuracy of exposure time were carried out on a diagnostic X-ray unit in the Radiation and Nuclear Safety Authority in Helsinki. The measurement performance was judged by calculating deviation E(n) normalised with respect to the stated uncertainties. E(n) values for all tests were less than unity and by the common ILC criteria the testing performance could be considered as acceptable.