Medical X-ray Systems Research Articles

Skeletal Deformities in Invaded Population of Amazon Sailfin Catfish Pterygoplichthys pardalis (Castelnau, 1855) in the East Kolkata Wetland, India

The incidence of severe vertebral deformity was reported in the specimens of the Amazon sailfin catfish Pterygoplichthys pardalis (Castelnau, 1855) for the first time in India. Fish samples were collected on bimonthly basis during June 2019 to December 2020, from wastewater-fed large aquaculture impoundments (locally called ‘bheries’) of north-western part of the East Kolkata Wetlands, India. Sampling were performed using seine nets of mesh size 15 mm–30 mm and covering more or less 5,000 sq m area each time. Deformities were found in 18 specimens of Pterygoplichthys pardalis. Two types of spinal deformities, scoliosis and kyphosis, were determined visually and reconfirmed by radiography using medical X-ray system. The total length and body weights of individual fish (normal and deformed) were measured and the length-weight relationships parameters were calculated and compared. A significant difference was observed between b values of deformed (b ~1.679) and normal specimens (b>2.5) of Pterygoplichthys pardalis. Various environmental and genetic factors could contribute to the development of this deformity in the Pterygoplichthys pardalis, but based on the available data, it is impossible to confidently identify the key factor(s). However, as the fishes were from a wastewater-fed fisheries system, which receive about 600 million litres of industrial and municipal discharge of the city every day, metal and other organic contaminants could be a reason of this impairment in Pterygoplichthys pardalis.

Investigation of the suitability of new developed epoxy based-phantom for child's tissue equivalency in paediatric radiology

In this study, tissue equivalency (TE) of a newly developed epoxy-based phantom to 3–5 years child's tissue was investigated in paediatric energy range. Epoxy-based TE-phantoms were produced at different glandular/adipose (G/A) ratios of 17/83%, 31/69%, 36/64% and 10/90%. A procedure was developed in which specific amounts of boron, calcium, magnesium, sulphur compounds are mixed with epoxy resin, together with other minor substitutes. In paediatric energy range of 40–60 kVp half-value layer (HVL) values were measured and then Hounsfield Units (HU) were determined from Computed Tomography(CT) scans taken in the X-ray energy range of 80-120kVp. It is found that radiation absorption properties of these phantoms in terms of the measured HVL values related to linear attenuation coefficients (μ) are very well mimicking a 3 years child's soft tissue in case a ratio of 10/90%G/A. Additionally, the HU values of phantoms were determined from the CT scans. The HU = 47.8 ± 4.8 value was found for the epoxy-based phantom produced at a ratio of 10/90%G/A. The obtained HVL and HU values also support the suitability of the new epoxy based-phantom produced at a ratio of 10/90%G/A for a satisfactory mimicking a 3 years child's soft tissue by 5%. Thus they can have a potential use to perform the quality controls of medical X-ray systems and dose optimization studies.

Quality Control of Medical Digital X-ray System Equipment and Analysis of Current Situation of Radiation Protection in the Computer Room of Our Hospital

Quality Control of Medical Digital X-ray System Equipment and Analysis of Current Situation of Radiation Protection in the Computer Room of Our Hospital

High Bandwidth Non-Resonant High Voltage Generator for X-Ray Systems

High-voltage supplies for medical X-ray systems require up to 150 kV DC at up to 100 kW to supply the tube. The challenge for the power supply however is not only to deal with the high voltage and high power demand, but also to provide short voltage rise- and fall times in the range of 100μs. A coupled interleaved circuit variant of a single active bridge concept, the coupled interleaved single active bridge converter, is demonstrated in this work providing very fast output voltage control due to its non-resonant structure. The conduction modes of the circuit are analysed in detail and compared to the uncoupled interleaved single active bridge approach, demonstrating the advantages of low inverter RMS current, zero voltage switching (or at least zero current switching) over the full operating range with constant switching frequency. Analytic expressions for the output current-duty cycle relationship are provided. Experiments on a 60 kW (low voltage equivalent) prototype show that rise times as low as five switching cycles are possible, allowing to reach the target of 100μs rise time using a switching frequency of only 50 kHz.

Trends in patient exposure to radiation in interventional cardiology over a 10-year period

Technological progress has made it possible to reduce the dose of radiation delivered by medical X-ray systems. In parallel, interventional coronary procedures have become increasingly complex and consequently, last longer. This study aimed to compared to the estimated dose of radiation received by patients in interventional cardiology at 10 years interval (2006 vs. 2016). The study population included all patients undergoing interventional coronary procedures in one of the catheterization laboratories (cathlabs) of our institution during two periods, namely period 1 from October 2005 to March 2006, and period 2 from November 2015 to October 2016. The primary endpoint was the estimated dose of radiation received by the patient as assessed by dose area product (DAP). In 2016, the estimated dose of radiation received by patients undergoing interventional coronary procedures was on average 77.7% lower than that received in 2006 ( P < 0.0001), whereas the fluoroscopy time increased by 54% on average over the same period ( P < 0.0001). By multivariate analysis including age, approach, body mass index, fluoroscopy time and performance of angioplasty, the reduction in radiation remained significant. The radial approach was significantly associated with an increased estimated dose of radiation received ( P < 0.0001) ( Table 1 , Fig. 1 ). In our centre, the estimated dose of radiation received by patients undergoing interventional cardiology procedures has been reduced by 77.7% over the last decade.

Accurate FRF Identification of LPV Systems: nD-LPM With Application to a Medical X-Ray System

Linear parameter varying (LPV) controller synthesis is a systematic approach for designing gain-scheduled controllers. The advances in LPV controller synthesis have spurred the development of system identification techniques that deliver the required models. The aim of this paper is to present an accurate and fast frequency response function (FRF) identification methodology for LPV systems. A local parametric modeling approach is developed that exploits smoothness over frequencies and scheduling parameters. By exploiting the smoothness over frequency as well as over the scheduling parameters, increased time efficiency in experimentation time and accuracy of the FRF is obtained. Traditional approaches, i.e., the local polynomial method/local rational method, are recovered as a special case of the proposed approach. The application potential is illustrated by a simulation example as well as real-life experiments on a medical X-ray system.

Trends in Patient Exposure to Radiation in Percutaneous Coronary Interventions Over a 10-Year Period

Technological progress has made it possible to reduce the dose of radiation delivered by medical x-ray systems. In parallel, interventional coronary procedures have become increasingly complex and consequently, last longer. This study aimed to compare the estimated dose of radiation received by patients in interventional cardiology at 10 years interval (2006 vs 2016). The study population included all patients who underwent interventional coronary procedures in one of the catheterization laboratories of our institution during 2 periods, namely, period 1 from October 2005 to March 2006, and period 2 from November 2015 to October 2016. The primary end point was the estimated dose of radiation received by the patient as assessed by dose area product. In 2016, the estimated dose of radiation received by patients who underwent interventional coronary procedures was on average 78% lower than that received in 2006 (p <0.0001), whereas the fluoroscopy time increased by 54% on average over the same period (p <0.0001). By multivariate analysis, including age, approach, body mass index, fluoroscopy time, and performance of angioplasty, the reduction in radiation remained significant. The radial approach was significantly associated with an increased estimated dose of radiation received (p <0.0001). In conclusion, the estimated dose of radiation received by patients who underwent interventional cardiology procedures has been reduced by 78% over the last decade.

Periodic Signal Tracking for Lightly Damped Systems

The focus of this paper is on the development of time-delay filters to accomplish tracking of periodic signals with zero phase errors. The class of problems addressed include systems whose dynamics are characterized by lightly damped modes. A general approach for the zero-phase tracking of periodic inputs is presented followed by an illustration of single harmonic tracking of underdamped second-order systems with relative degree two. A general formulation of the approach is then posed for higher-order systems and systems including zeros. The paper concludes with the illustration of enforcing constraints to desensitize the time-delay filter to uncertainties in the location of the poles of the system and forcing frequencies. A numerical practical design case based on a medical X-ray system is used to illustrate the potential of the proposed technique.

Efficient nonparametric identification for high-precision motion systems: A practical comparison based on a medical X-ray system

The need for accurate knowledge of complex dynamical behavior for high-performance mechatronic systems led to the development of a vast amount of nonparametric system identification approaches over the recent years. The aim of this paper is to compare several proposed methods based on experiments on a physical complex mechanical system to bridge the gap between identification theory and practical applications in industry where basic identification approaches are often the norm. Typical practical implications such as operation under closed-loop control, multivariable coupled behavior and nonlinear effects are included in the analysis. Finally, a possible approach for fast and reliable identification is illustrated based on measurement results of an interventional medical X-ray system.

Model-based geometric calibration for medical x-ray systems.

Currently applied calibration approaches lead to satisfying 3D roadmapping overlay and 3D reconstruction accuracies; however, the required calibration times are extensive. The aim of this paper is the introduction of a novel model-based approach for geometric system calibrations, leading to a significant reduction of calibration times. By using physical insight into the system, a physical model is derived which can be exploited to predict geometric calibrations parameters. Model-parameters are estimated using a limited set of phantom-based measurement data. Effectively, the calibration procedure is recast to a parameter identification experiment. The potential of the proposed approach is illustrated by virtue of a benchmark object, successful reconstruction of a clinical phantom, and comparison to phantom-based accuracies. Accurate models are required to achieve the desired accuracies. Based on the results in this work, the approach seems to be feasible for practical applications; however, to achieve all the desired specifications, future research should focus on enhanced modeling techniques.

Application of a Time-Delay Pre-Filter Design for Periodic Signal Tracking of Lightly-Damped Multivariable Systems

The aim of this work is the illustration of time-delay filter applications for three current industrial high-performance motion control problems. The main focus is on time-delay filters that enable zero phase tracking of periodic signals, however this is not a restriction for the introduced approaches. The first problem introduced in this paper is the point-of-interest or inferential control problem where the feedback variable typically is not the same as the performance variable. The second illustration is an application of time-delay filter design on a multivariable robotic system. The third challenge illustrates how a robust time-delay filter design allows for practical implementations on medical X-ray systems.

診療用Ｘ線撮影システムおよびＣＲシステムにおける簡便な始業点検プログラムの評価

We investigated the feasibility of a simple, easy method that uses a digital radiography (DR) phantom for daily operational checks of the medical X-ray system and computed radiography (CR) system. First, we measured exposure indicator calibration (S value) from 12 seconds to 11 minutes after irradiation to examine the effect of fading of the photostimulable phosphor screen. We then examined the management width of the exposure indicator calibration ratio and limiting resolution of the CR system. Finally, we studied the exposure indicator calibration ratio, limiting the resolution and time necessary for the initial check-up by running the program 20 times for five weeks. Under the influence of the fading, the S value increased gradually, although the level of variation was small. From the mean and coefficient of variation of the exposure indicator calibration ratio, the management width was determined as +/-10%. The exposure indicator calibration ratio and limiting resolution were within +/-10% and +/-20%, respectively. It took three minutes to accomplish the initial check-up. The initial check-up using a DR phantom is simple and can perform the operational check of the medical X-ray system and the CR system with sufficient accuracy in only 3 minutes.

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.

Image quality evaluation and patient dose assessment of medical fluoroscopic X-ray systems: a national study

This study presents the results from a survey conducted by the Greek Atomic Energy Commission (GAEC), during the period 1998-2003, in 530 public and private owned fluoroscopic X-ray systems in Greece. Certain operational parameters for conventional and remote control systems were assessed, according to a quality control protocol developed by GAEC on the basis of the current literature. Public (91.5%) and private (81.5%) owned fluoroscopic units exhibit high-contrast resolution values over 1 lp mm(-1). Moreover, 88.5 and 87.1% of the fluoroscopic units installed in the public and private sector, respectively, present Maximum Patient Entrance Kerma Rate values lower than 100 mGy min(-1). Additionally, 68.3% of the units assessed were found to perform within the acceptance limits. Finally, the third quartile of the Entrance Surface Dose Rate distribution was estimated according to the Dose Reference Level definition and found equal to 35 mGy min(-1).

Calibration model of a dual gain flat panel detector for 2D and 3D x‐ray imaging

The continuing research and further development in flat panel detector technology have led to its integration into more and more medical x-ray systems for two-dimensional (2D) and three-dimensional (3D) imaging, such as fixed or mobile C arms. Besides the obvious advantages of flat panel detectors, like the slim design and the resulting optimum accessibility to the patient, their success is primarily a product of the image quality that can be achieved. The benefits in the physical and performance-related features as opposed to conventional image intensifier systems, (e.g., distortion-free reproduction of imaging information or almost linear signal response over a large dynamic range) can be fully exploited, however, only if the raw detector images are correctly calibrated and postprocessed. Previous procedures for processing raw data contain idealizations that, in the real world, lead to artifacts or losses in image quality. Thus, for example, temperature dependencies or changes in beam geometry, as can occur with mobile C arm systems, have not been taken into account up to this time. Additionally, adverse characteristics such as image lag or aging effects have to be compensated to attain the best possible image quality. In this article a procedure is presented that takes into account the important dependencies of the individual pixel sensitivity of flat panel detectors used in 2D or 3D imaging and simultaneously minimizes the work required for an extensive recalibration. It is suitable for conventional detectors with only one gain mode as well as for the detectors specially developed for 3D imaging with dual gain read-out technology.

Special bump bonding technique for silicon pixel detectors

This paper presents a high-density bumping technique based on electrodeposition of the bump materials. The idea of such technique is to allow the packaging of densely populated chips such as array pixel detectors. Silicon pixel detector dummies have been designed and fabricated at CNM in order to evaluate the technique developed. Special test structures have been included in these dummies to evaluate the final yield of the process developed at CNM. The foreseen applications are Medical Imaging and X-ray systems. The new bumping technique developed will greatly improve the simplicity and the cost of the packaging process.

X-ray spectroscopy and dosimetry with a portable CdTe device

X-ray spectra and dosimetry information are very important for quality assurance (QA) and quality control (QC) in medical diagnostic X-ray systems. An accurate knowledge of the diagnostic X-ray spectra would improve the patient dose optimization, without compromising image information. In this work, we performed direct diagnostic X-ray spectra measurements with a portable device, based on a CdTe solid-state detector. The portable device is able to directly measure X-ray spectra at high photon fluence rates, as typical of clinical radiography. We investigated on the spectral performances of the system in the mammographic energy range (up to ∼40 keV). Good system response to monoenergetic photons was measured (energy resolution of 5% FWHM at 22.1 keV). We measured the molybdenum X-ray spectra produced by a mammographic X-ray unit (GE Senographe DMR) at 28 kV and 30 kV under clinical conditions. The results showed the good reproducibility of the system and low pile-up distortions. Preliminary dosimetric measurements have been regarded as exposure and half value layer (HVL) values obtained from direct measurements and from measured X-ray spectral data, and a good agreement between exposure attenuation curves and the HVL values was obtained. The results indicated that the portable device is suitable for mammographic X-ray spectroscopy under clinical conditions.

Self-normalizing method to measure the detective quantum efficiency of a wide range of x-ray detectors.

The detective quantum efficiency (DQE) is widely accepted as the most relevant parameter to characterize the image quality of medical x-ray systems. In this article we describe a solid method to measure the DQE. The strength of the method lies in the fact that it is self-normalizing so measurements at very low spatial frequencies are not needed. Furthermore, it works on any system with a response function which is linear in the small-signal approximation. We decompose the DQE into several easily accessible quantities and discuss in detail how they can be measured. At the end we lead the interested reader through an example. Noise equivalent quanta and normalized contrast values are tabulated for standard radiation qualities.

Current advances and future trends in X-ray digital detectors for medical applications

Despite the progress made in imaging modalities based on nonionizing radiation such as ultrasound and magnetic resonance imaging, X-ray is still the primary imaging method in most radiology departments. In recent years, digital electronics and manufacturing methods have led to many approaches for the design and construction of X-ray detectors. The ideal medical X-ray system is a digital, flat-panel able to perform all current radiological modalities at reduced dose. It would, immediately after the patient's X-ray exposure, provide a high quality radiograph on a video monitor. It would also be usable for real-time imaging (e.g., digital cine loops and fluoroscopy). The physical form would be similar to a film/screen cassette (except for the addition of an umbilical cord) which could easily fit into the Bucky tray of existing X-ray rooms. There are two main approaches both based on active matrix technology developed for lap-top displays. The first, called the direct method employs a photoconductive layer of amorphous selenium (a-Se) to detect X-rays. The charge image formed on the surface of the a-Se is digitally read out in situ using a two-dimensional array of thin-film transistors (TFT's), i.e., an active matrix. The second flat panel method is called the indirect method and uses an active matrix to readout a phosphor layer. Phosphors give off light on interaction with X-rays and this is sensed by photo diodes on the active matrix. The relative practicality of the direct and indirect active matrix readout systems is an area of current investigation.

5.医用X線システムの人間工学的設計について(II.医用X線システムの人間工学的設計)(第37回総会)

In case of planning any medical X-ray system, we must consider the factors like capability, operation and safety. The safety and operation arise from human character. Therefore human engineering must be investigated and the harmony between the machine and the operater should be maintained, property and sufficiently.