Entrance Surface Air Kerma Rate Research Articles

Effect of shape of automatic dose rate control and wedge compensation filter on radiation dose in an angiography system with a flat-panel detector.

The purpose was to investigate air-kerma area product (PKA) and entrance surface air-kerma rate ([Formula: see text]a,e) on the effect of the shape of automatic dose rate control (ADRC) in the presence of a wedge compensation filter. We compared and evaluated the variability of the X-ray output using a combination of wedge compensation filters and the ADRC. Two ADRC shapes (round and square) and three poly-methyl-methacrylate thicknesses (15, 20, and 25cm) were used. A wedge compensation filter was inserted 2cm at a time, up to 6cm. When the wedge compensation filter was inserted to 6 cm for 20cm of poly-methyl-methacrylate, the X-ray output fluctuated significantly. The PKA was reduced by 39% when the wedge compensation filter was inserted to 6 cm and by 59% when it was inserted to 4cm under round-type for 20cm poly-methyl-methacrylate. The shape of the ADRC affects [Formula: see text]a,e and PKA.

Evaluation of dose radiation on x-ray radiography

Evaluated radiation dose and output of general radiographic machine on the thorax and abdomen examination. Radiation output testing on 53 radiographic machine produced 1985-2017 in East Java, Indonesia. For thorax examination, 45-89 kV, 100-200 mA, exposure time 0.01-100 s and abdominal examination, 50-89 kV, 18-320 mA, exposure time is 0.02-100 s. Tests are carried out with the Piranha X-Ray Multimeter. There are reportedly 3 of 53 radiographic machine in the thorax examination as follows: the incident air kerma (INAK), tube output, and entrance surface air kerma (ESAK) rates ranged between 0.019 - 1.604 mGy, 0.0004 - 0.0057 mGy/mAs, and 0.024 - 2.101 mGy. While on abdominal examination, the INAK, tube output, and ESAK rates ranged between 0.009 - 2.710 mGy, 0.014 - 0.072 mGy/mAs, and 0.013 - 3.660 mGy., From data with various brands, general radiographic machine in East Java, for Thorax and Abdomen examination INAK values are below 1,604 mGy, 2,710 mGy, values are below 0.0057 mGy / mAs, 0.072 mGy / mAs, and ESAK values are below 2,101 mGy, 2,710 mGy and still within the limits permitted by the BAPETEN regulation in Indonesia.

Second generation stationary digital breast tomosynthesis system with faster scan time and wider angular span.

The aim of this study was to characterize a new generation stationary digital breast tomosynthesis system with higher tube flux and increased angular span over a first generation system. The linear CNT x-ray source was designed, built, and evaluated to determine its performance parameters. The second generation system was then constructed using the CNT x-ray source and a Hologic gantry. Upon construction, test objects and phantoms were used to characterize system resolution as measured by the modulation transfer function (MTF), and artifact spread function (ASF). The results indicated that the linear CNT x-ray source was capable of stable operation at a tube potential of 49kVp, and measured focal spot sizes showed source-to-source consistency with a nominal focal spot size of 1.1mm. After construction, the second generation (Gen 2) system exhibited entrance surface air kerma rates two times greater the previous s-DBT system. System in-plane resolution as measured by the MTF is 7.7cycles/mm, compared to 6.7cycles/mm for the Gen 1 system. As expected, an increase in the z-axis depth resolution was observed, with a decrease in the ASF from 4.30mm to 2.35mm moving from the Gen 1 system to the Gen 2 system as result of an increased angular span. The results indicate that the Gen 2 stationary digital breast tomosynthesis system, which has a larger angular span, increased entrance surface air kerma, and faster image acquisition time over the Gen 1s-DBT system, results in higher resolution images. With the detector operating at full resolution, the Gen 2s-DBT system can achieve an in-plane resolution of 7.7cycles per mm, which is better than the current commercial DBT systems today, and may potentially result in better patient diagnosis.

OPTIMISATION OF PATIENT DOSE AND IMAGE QUALITY IN ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATOGRAPHY: A PHANTOM-BASED EVALUATION.

A phantom-based study is presented aiming to optimise patient dose and image quality (IQ) in endoscopic retrograde cholangiopancreatography procedures, utilising a fluoroscopy system equipped with a flat panel detector. The patient thickness was simulated with various polymethyl methacrylate slabs, whilst IQ was evaluated using the Leeds test object. The main factors evaluated were phantom thickness, distance between phantom and detector, field of view and pulse rate. For all these factors, the dosemetric indices, entrance surface air kerma (ESAK) rate and ESAK per pulse, as well as the IQ parameters, signal-to-noise ratio and high contrast spatial resolution, were measured. Based on these measurements, the figure of merit (FOM) was estimated. The FOM and ESAK rate values indicated the optimum combination of the factors evaluated which could provide adequate clinical information, assuring minimum patient dose.

Measuring skin dose in CT examinations under complex geometries: Instruments, methods and considerations

ObjectiveTo investigate skin dose in Computed Tomography (CT) and its dependence on scanning geometry. Materials and methodsMeasurements of entrance surface air kerma (ESAK) in free air and entrance skin dose (ESD) on an anthropomorphic phantom were performed in a 64-slice CT scanner, using two different instruments: the Dose Profiler (DP) and the QED skin diode (QEDSD). Using DP and QEDSD, the ESAK rate profiles at the isocenter and at different distances from it, were measured using axial scans. Using DP and helical scans the ESAK rate profile in the Z-axis was acquired. The same profile was acquired with the QEDSD also, using many axial scans and manual table translation. ESD measurements were performed with the DP and QEDSD, in axial and helical scan mode. ResultsESAK measurements with DP and QEDSD were in good agreement, for both point dose and profile measurements. The agreement was also good for ESD measurements but not for helical scans, due to variable X-ray beam overlapping and different tube angular positions at each scan start. It was observed that the ESD values at different Y-axis offsets were comparable to the respective ESAK values recorded at the same Y-axis offset distances without the phantom. ConclusionsBoth DP and QEDSD were proven suitable for performing point ESD measurements. However, calculating the skin dose distribution in CT examinations is a very challenging task. A practical approach would be for CT scanners to provide a conservative estimate of the peak skin dose using the isocenter ESAK value.

Entrance surface air kerma in X-ray systems for paediatric interventional cardiology: a national survey.

The aims of this work were to report the results of a national survey on entrance surface air kerma (ESAK) values for different phantom thicknesses and operation modes in paediatric interventional cardiology (IC) systems and to compare them with previous values. The national survey also offers suggested investigation levels (ILs) for ESAK in paediatric cardiac procedures. ESAK was measured on phantoms of 4-16 cm thickness of polymethyl methacrylate slabs. For low fluoroscopy mode (FM), ESAK rates ranged from 0.11 to 33.1 mGy min(-1) and for high FM from 0.34 to 61.0 mGy min(-1). For cine mode, values of ESAK per frame were from 1.9 to 78.2 µGy fr(-1). The ILs were suggested as the third quartile of the values measured. This research showed lower ESAK values than in previous research, particularly for ESAK values in cine modes. This work represents a first step towards launching a national programme in paediatric dosimetry for IC procedures.

Impact of the X-ray system setting on patient dose and image quality; a case study with two interventional cardiology systems

This study investigates the influence of the initial X-ray system setting on patient doses and image quality in interventional cardiology procedures. Two dedicated interventional cardiology systems were studied: a system with image intensifier (II) and a flat detector (FD) system. Entrance surface air kerma (ESAK) rates in fluoroscopy and ESAK per frame in the acquisition mode were measured on the surface of a PMMA phantom for the field of views (FOV) of 23 and 17 cm (II system) and 25 and 20 cm (FD system). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were estimated using DICOM images obtained during the measurements. System performances were compared using a figure of merit combining SNR and ESAK. The influence of system setting on patient doses was investigated analysing the information for air kerma area product (KAP) and cumulative dose (CD) at the patient entrance reference point, for a sample of coronary angiography examinations. ESAK rates in fluoroscopy modes were a factor of 2 higher in the FD system for the similar FOVs, resulting in a factor of 1.9 higher median values of KAP and CD for patients with FD system than for the II system. SNR and CNR for the FD system were better than the equivalent FOVs with II. The resulting FOM was better for the FD system in both FOVs. Potential for optimisation was suggested by adjusting system settings.

SU-E-I-29: Dose Rate and Image Quality Comparison Between Philips Veradius and GE OEC 9900 Elite Fluoroscopic C-Arms.

The radiation dose rate and image quality were compared on GE OEC 9900 Elite Vas 8 and Philips Veradius fluoroscopic C-arms. Plastic (PMMA) phantoms were used to simulate various thicknesses of soft tissues encountered during fluoroscopically-guided interventional procedures while aluminum and copper phantoms were used to simulate extremities of different sizes. An image quality test tool and an ionization chamber were included in the setup of each phantom. The phantoms were imaged in several fluoroscopy modes and at different dose levels. The entrance surface air KERMA rate (ESAKR) was measured for each phantom in each fluoroscopy mode. Simultaneously, the image quality was assessed by counting the number of low-contrast objects visible in the image quality test tool. For a given phantom type and thickness, the ESAKR was plotted versus the number of visible low-contrast objects to compare the dose rate required for a given level of image quality. Additionally, the mean ESAKR per number of objects was calculated and p-values were used to test for statistically significant differences between the C-arms. For comparable image quality with a given phantom type and thickness the ESAKR with the OEC was typically much higher than with the Veradius. One-tailed, unpaired t-tests confirm that the mean ESAKR per number of visible low-contrast objects was lower for the Veradius than for the OEC with all thicknesses of PMMA (p < 0.05). The differences for the aluminum and copper phantoms were much smaller and were not statistically significant (p-values ranged from 0.2 to 0.47). In general, the Veradius C-arm provided better low-contrast image quality during fluoroscopy, with lower ESAKR than the OEC 9900 Elite Vas 8. The differences were statistically significant only with PMMA phantoms. Funding support provided by Philips Healthcare (Bothell, WA).

A national patient dose survey and setting of reference levels for interventional radiology in Bulgaria

A national study on patient dose values in interventional radiology and cardiology was performed in order to assess current practice in Bulgaria, to estimate the typical patient doses and to propose reference levels for the most common procedures. Fifteen units and more than 1,000 cases were included. Average values of the measured parameters for three procedures-coronary angiography (CA), combined procedure (CA + PCI) and lower limb arteriography (LLA)--were compared with data published in the literature. Substantial variations were observed in equipment and procedure protocols used. This resulted in variations in patient dose: air-kerma area product ranges were 4-339, 6-1,003 and 0.2-288 Gy cm(2) for CA, CA + PCI and LLA respectively. Reference levels for air kerma-area product were proposed: 40 Gy cm(2) for CA, 140 Gy cm(2) for CA + PCI and 45 Gy cm(2) for LLA. Auxiliary reference intervals were proposed for other dose-related parameters: fluoroscopy time, number of images and entrance surface air kerma rate in fluoroscopy and cine mode. There is an apparent necessity for improvement in the classification of peripheral procedures and for standardisation of the protocols applied. It is important that patient doses are routinely recorded and compared with reference levels. • Patient doses in interventional radiology are high and vary greatly • Better standardisation of procedures and techniques is needed to improve practice • Dose reference levels for most common procedures are proposed.

Radiation dose and image quality for adult interventional cardiology in Chile: a national survey

The aim of this work was to investigate the differences in dose settings and image quality among 10 X-ray systems used for interventional cardiology in Chile. Entrance surface air kerma (ESAK) was measured on a phantom of 20 cm thickness of polymethyl methacrylate slabs. Image quality was evaluated using DICOM images of a test object Leeds TOR 18-FG for cine mode acquisition, through the numerical parameters signal-to-noise ratio (SNR), high-contrast spatial resolution (HCSR) and figure of merit. ESAK rate values for fluoroscopy modes ranged between 7.1 and 121.7 mGy min(-1). For cine mode, ESAK values per frame ranged from 63 to 400 µGy fr(-1). SNR and HCSR parameters for cine mode varied from 4.8 to 8.6 and 0.4 to 10, respectively. FOM values resulted from 6.9 to 64.5 among the different X-ray systems. Results show important differences between systems and point out the need to launch an optimisation programme.

Estudo de otimização de imagens em fluoroscopia intervencionista

OBJETIVO: O objetivo deste trabalho é o de estudar a otimização da qualidade da imagem fluoroscópica e a taxa de kerma no ar de entrada na superfície do paciente em procedimentos de radiologia intervencionista, utilizando-se de um objeto simulador adaptado para fluoroscopia. MATERIAIS E MÉTODOS: Foi utilizado um objeto simulador desenvolvido para avaliação de imagens em radiologia convencional. O objeto simulador foi adaptado para fluoroscopia mediante incorporação de dois cateteres com diferentes espessuras, ambos utilizados em radiologia intervencionista. Os níveis de taxa de kerma no ar de entrada na superfície do paciente foram determinados utilizando-se este objeto simulador. RESULTADOS: A avaliação dos parâmetros técnicos para diversos modos de exposição de um equipamento fluoroscópico com digitalização de imagens permitiu estabelecer os indicadores de taxa de kerma no ar, que permitem a otimização da qualidade das imagens em procedimentos intervencionistas. A redução na taxa de kerma no ar de entrada na superfície do paciente pode chegar a 67%. CONCLUSÃO: A otimização da qualidade da imagem utilizando-se um objeto simulador possibilita reduzir a taxa de kerma no ar de entrada na superfície do paciente, sem perda considerável de informação diagnóstica.

Avaliação do kerma no ar na superfície de entrada e da qualidade da imagem em radiografias de tórax

OBJETIVO: Avaliar os fatores de técnica utilizados durante exames de tórax póstero-anterior em pacientes-padrão e correlacioná-los aos valores de kerma no ar na superfície de entrada e à qualidade das imagens clínicas. MATERIAIS E MÉTODOS: O estudo foi realizado em três hospitais do Rio de Janeiro, num total de cinco salas de raios X, com dez pacientes por sala. As imagens foram avaliadas pelos radiologistas dos serviços segundo o protocolo europeu. O kerma no ar na superfície de entrada foi estimado a partir da curva de rendimento do equipamento de raios X, que foi obtida utilizando câmara de ionização acoplada a um eletrômetro. Análise de variância foi realizada para verificar se a diferença entre os valores de kerma no ar na superfície de entrada é significativa. RESULTADOS: Os valores de kerma no ar na superfície de entrada variaram entre 0,05 e 0,26 mGy, com média 60% inferior ao nível de referência publicado na Portaria 453. Das imagens avaliadas, 98% atenderam acima de 65% dos critérios de qualidade. CONCLUSÃO: Para um padrão de qualidade da imagem, aceitável para o diagnóstico, verificou-se ampla variação do kerma no ar na superfície de entrada para pacientes-padrão. Isto demonstra a falta de padronização dos fatores de técnica e a existência de um potencial de redução do valor do kerma no ar na superfície de entrada.

Comparison of Patient Dose in Two-Dimensional Carotid Arteriography and Three-Dimensional Rotational Angiography

It is known that interventional neuroradiology (IN) involves high radiation dose to both patients and staff even if performed by trained operators using modern fluoroscopic X-ray equipment and dose-reducing technology. Therefore, every new technology or imaging tool introduced, such as three-dimensional rotational angiography (3D RA), should be evaluated in terms of radiation dose. 3D RA requires a series with a large number of images in comparison with 2D angiography and it is sometimes considered a high-dose IN procedure. The literature is scarce on the 3D RA radiation dose and in particular there are no data on carotid arteriography (CA). The aim of this study was to investigate patient dose differences between 2D and 3D CA. The study included 35 patients undergoing 2D CA in hospital 1 and 25 patients undergoing 3D CA in hospital 2. Patient technical data collection included information on the kerma area product (KAP), fluoroscopy time (T), total number of series (S), and total number of acquired images (F). Median KAP was 112 Gy cm(2) and 41 Gy cm(2) for hospitals 1 and 2, respectively, median T was 8.2 min and 5.1 min, median S was 13 and 4, and median F was 247 and 242. Entrance surface air-kerma rate, as measured in "medium" fluoroscopy mode measured in 2D acquisition using a 20 cm phantom of polymethylmethacrylate, was 17.3 mGy/min for hospital 1 and 9.2 mGy/min for hospital 2. 3D CA allows a substantial reduction in patient radiation dose compared with 2D CA, while providing the necessary diagnostic information.

Influence of patient thickness and operation modes on occupational and patient radiation doses in interventional cardiology

Patient and staff dose values in an interventional cardiology laboratory for different operational modes and several patient thicknesses (from 16 to 28 cm, simulated using polymethylmethacrylate) are presented. When increasing patient thicknesses and depending on fluoroscopy and cine modes, occupational doses can increase >30 times the baseline level. Scatter dose rates at the cardiologist's position with no radiation protective tools ranged from 1 to 14 mSv h(-1) for fluoroscopy, and from 10 to 47 mSv h(-1) during cine acquisition. Patient entrance surface air kerma rates increased by nearly 3 and staff dose rates by up to 2.6 when fluoroscopy was moved from the low to the high mode, for a typical 20 cm thickness. The respective increase factors were 6 and 4.2 when patient thickness rose from 16 to 28 cm, and by 10 and 8.3, when comparing cine acquisition with the low fluoroscopy mode. The knowledge of typical dose rates for each X-ray system in use in catheterisation laboratories is essential in order to optimise protection of patients and staff.

Are new technologies always reducing patient doses in cardiac procedures?

Dynamic digital flat-panel (FD) imaging technology is characterised by a higher sensitivity and image quality compared to image intensifier (II) technology. In this study, an angiography system based on II and one based on FD were compared with respect to system performance and impact of patient dose in interventional cardiology. When entrance surface air kerma rates are measured, the FD system requires a reduced dose rate, of up to 40%. For coronary angiography (CA), fluoroscopy time (FT) and dose-area product (DAP) were 4.3 +/- 5.0 min and 31.2 +/- 30.2 Gy cm2 on the II system and 4.4 +/- 3.8 min and 33.4 +/- 19.2 Gy cm2 with the FD system. For percutaneous transluminal coronary angiography, FT and DAP were 11.4 +/- 10.7 min and 52.1 +/- 45.0 Gy cm2 on II and 10.7 +/- 8.7 min and 66.9 +/- 54.4 Gy cm2 on DF. Data comparison suggests that reduced entrance dose rates do not automatically imply a reduction of patient dose in clinical practice.