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Jones A, Ansell C, Jerrom C, Honey ID. Optimization of image quality and patient dose in radiographs of paediatric extremities using direct digital radiography. Br J Radiol 2015; 88:20140660. [PMID: 25816115 PMCID: PMC4628445 DOI: 10.1259/bjr.20140660] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 02/02/2015] [Accepted: 03/26/2015] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE The purpose of this study was to evaluate the effect of beam quality on the image quality (IQ) of ankle radiographs of paediatric patients in the age range of 0-1 year whilst maintaining constant effective dose (ED). METHODS Lateral ankle radiographs of an infant foot phantom were taken at a range of tube potentials (40.0-64.5 kVp) with and without 0.1-mm copper (Cu) filtration using a Trixell Pixium 4600 detector (Trixell, Morains, France). ED to the patient was computed for the default exposure parameters using PCXMC v. 2.0 and was fixed for other beam qualities by modulating the tube current-time product. The contrast-to-noise ratio (CNR) was measured between the tibia and adjacent soft tissue. The IQ of the phantom images was assessed by three radiologists and a reporting radiographer. Four IQ criteria were defined each with a scale of 1-3, giving a maximum score of 12. Finally, a service audit of clinical images at the default and optimum beam qualities was undertaken. RESULTS The measured CNR for the 40 kVp/no Cu image was 12.0 compared with 7.6 for the default mode (55 0.1 mm Cu). An improvement in the clinical IQ scores was also apparent at this lower beam quality. CONCLUSION Lowering tube potential and removing filtration improved the clinical IQ of paediatric ankle radiographs in this age range. ADVANCES IN KNOWLEDGE There are currently no UK guidelines on exposure protocols for paediatric imaging using direct digital radiography. A lower beam quality will produce better IQ with no additional dose penalty for infant extremity imaging.
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Affiliation(s)
- A Jones
- Medical Physics Department, Guy's and St Thomas' NHS Foundation Trust, London, UK
- Medical Physics Department, Western Sydney Local Health District, Sydney, NSW, Australia
| | - C Ansell
- Radiology Department, Evelina London Children's Hospital, Guy's and St Thomas' NHS Foundation Trust, London, UK
| | - C Jerrom
- Medical Physics Department, Guy's and St Thomas' NHS Foundation Trust, London, UK
| | - I D Honey
- Medical Physics Department, Guy's and St Thomas' NHS Foundation Trust, London, UK
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Miracle AC, Mukherji SK. Conebeam CT of the head and neck, part 1: physical principles. AJNR Am J Neuroradiol 2009; 30:1088-95. [PMID: 19439484 DOI: 10.3174/ajnr.a1653] [Citation(s) in RCA: 199] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Conebeam x-ray CT (CBCT) is a developing imaging technique designed to provide relatively low-dose high-spatial-resolution visualization of high-contrast structures in the head and neck and other anatomic areas. This first installment in a 2-part review will address the physical principles underlying CBCT imaging as it is used in dedicated head and neck scanners. Concepts related to CBCT acquisition geometry, flat panel detection, and image quality will be explored in detail. Particular emphasis will be placed on technical limitations to low-contrast detectability and radiation dose. Proposed methods of x-ray scatter reduction will also be discussed.
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Affiliation(s)
- A C Miracle
- Department of Radiology, University of Michigan Health System, University Hospital, Ann Arbor, MI 48109-5030, USA.
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Brook O, Fischer D, Litmanovich D, Leiderman M, Molnar R, Ghersin E, Shreiber R, Hirshenbaum A, Kleinhaus U, Rosenberger A, Engel A. Prospective study of digital radiographs versus conventional screen films in Small Bowel Follow-Through examination. Comput Med Imaging Graph 2008; 32:531-8. [DOI: 10.1016/j.compmedimag.2008.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Accepted: 06/03/2008] [Indexed: 10/21/2022]
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Kleinman PL, Zurakowski D, Strauss KJ, Cleveland RH, Perez-Rosello JM, Nichols DP, Zou KH, Kleinman PK. Detection of Simulated Inflicted Metaphyseal Fractures in a Fetal Pig Model: Image Optimization and Dose Reduction with Computed Radiography. Radiology 2008; 247:381-90. [DOI: 10.1148/radiol.2472070811] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Cowen AR, Kengyelics SM, Davies AG. Solid-state, flat-panel, digital radiography detectors and their physical imaging characteristics. Clin Radiol 2008; 63:487-98. [PMID: 18374710 DOI: 10.1016/j.crad.2007.10.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2007] [Revised: 10/08/2007] [Accepted: 10/21/2007] [Indexed: 10/22/2022]
Abstract
Solid-state, digital radiography (DR) detectors, designed specifically for standard projection radiography, emerged just before the turn of the millennium. This new generation of digital image detector comprises a thin layer of x-ray absorptive material combined with an electronic active matrix array fabricated in a thin film of hydrogenated amorphous silicon (a-Si:H). DR detectors can offer both efficient (low-dose) x-ray image acquisition plus on-line readout of the latent image as electronic data. To date, solid-state, flat-panel, DR detectors have come in two principal designs, the indirect-conversion (x-ray scintillator-based) and the direct-conversion (x-ray photoconductor-based) types. This review describes the underlying principles and enabling technologies exploited by these designs of detector, and evaluates their physical imaging characteristics, comparing performance both against each other and computed radiography (CR). In standard projection radiography indirect conversion DR detectors currently offer superior physical image quality and dose efficiency compared with direct conversion DR and modern point-scan CR. These conclusions have been confirmed in the findings of clinical evaluations of DR detectors. Future trends in solid-state DR detector technologies are also briefly considered. Salient innovations include WiFi-enabled, portable DR detectors, improvements in x-ray absorber layers and developments in alternative electronic media to a-Si:H.
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Affiliation(s)
- A R Cowen
- LXi Research, Academic Unit of Medical Physics, The University of Leeds, West Yorkshire, UK.
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Hamer OW, Sirlin CB, Strotzer M, Borisch I, Zorger N, Feuerbach S, Völk M. Chest radiography with a flat-panel detector: image quality with dose reduction after copper filtration. Radiology 2005; 237:691-700. [PMID: 16192324 DOI: 10.1148/radiol.2372041738] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To compare image quality and estimated dose for chest radiographs obtained by using a cesium iodide-amorphous silicon flat-panel detector at fixed tube voltage and detector entrance dose with and without additional 0.3-mm copper filtration. MATERIALS AND METHODS The study was approved by the institutional ethics committee. All prospectively enrolled patients signed the written consent form. Chest radiographs in two projections were acquired at 125-kVp tube voltage and 2.5-microGy detector entrance dose. The experimental group (38 patients) was imaged with 0.3-mm copper filtration; the control group (38 patients) was imaged without copper filtration. An additional 12 patients were imaged with and without copper filtration and served as paired subject-controls. Three readers blinded to group and clinical data independently evaluated the radiographs for image quality on a digital display system. Twelve variables (six for each radiographic projection) were assigned scores on a seven-point ordinal scale. Scores between experimental and control groups were compared: Logistic regression analysis and Mann-Whitney U test were used for unpaired patients; and Wilcoxon and McNemar test, for paired patients. In all, 72 comparisons were determined (36 [12 variables x three readers] for unpaired patients and 36 for paired patients). In a phantom study, radiation burden of experimental protocol was compared with that of control protocol by using Monte Carlo calculations. RESULTS For 70 of 72 comparisons, digital radiographs obtained with copper filtration were of similar image quality as radiographs obtained without copper filtration (P = .123 to P > .99). For two of 72 comparisons, one observer judged the experimental protocol superior to the control protocol (P = .043, P = .046). Patient dose reduction estimated with Monte Carlo calculations was 31%. Use of copper filtration increased exposure times by 48% for posteroanterior views and by 34% for lateral views. CONCLUSION Subjectively equivalent chest radiographic image quality was found with estimated 30% dose reduction after addition of 0.3-mm copper filtration with flat-panel cesium iodide-amorphous silicon technology.
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Affiliation(s)
- Okka W Hamer
- Department of Diagnostic Radiology, University Hospital of Regensburg, Franz-Josef-Strauss-Allee 11, 93042 Regensburg, Germany.
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Holdsworth DW, Pollmann SI, Nikolov HN, Fahrig R. Correction of XRII geometric distortion using a liquid-filled grid and image subtraction. Med Phys 2005; 32:55-64. [PMID: 15719955 DOI: 10.1118/1.1827751] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
X-ray image intensifier (XRII) geometric distortion reduces the accuracy of image-guided procedures and quantitative image reconstructions. Due to the dependence of this error on the earth's magnetic field, the required correction is angle dependent, and calibration data should ideally be acquired simultaneously with clinical image data, at a specific orientation. We describe a technique to correct XRII geometric image distortion at any angular position during a stereotactic procedure. This approach uses a machined plastic grid, which contains channels that can be filled with iodinated contrast agent and subsequently flushed with water, providing contrast and mask images, respectively, of a geometric calibration grid. The standard image subtraction capabilities of conventional digital subtraction angiography devices can then be used to create a subtraction image of the iodine-filled channels, without any confounding anatomical structure. Grid-line intersection points are used to determine the control points that are required for a global polynomial correction algorithm, creating a correction map that is specific to the current angular position and XRII field of view (FOV). Tests with a clinical C-arm based XRII show that control points can be obtained with a precision of +/-0.053 mm, resulting in geometric correction accuracy of +/-0.152 mm, at a nominal FOV of 40 cm. While the precision and accuracy are both poorer than that achieved with a high-contrast steel-bead grid, the fact that the liquid grid can remain rigidly attached to the XRII during an entire procedure results in the establishment of an absolute detector coordinate system (referenced to the liquid-filled correction grid). The design of the liquid-filled channels allows the required control points to be introduced into the image or removed in about 30 s, avoiding the appearance of obscuring or confounding markers during clinical image acquisition, with a concurrent increase in patient dose of about 8% in the current design. Applications for this technique include stereotactic surgery, radiosurgery, x-ray stereogrammetry, and other image-guided procedures.
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Affiliation(s)
- David W Holdsworth
- Imaging Research Laboratories, Robarts Research Institute, London N6A 5K8, Ontario, Canada.
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Neofotistou V, Tsapaki V, Kottou S, Schreiner-Karoussou A, Vano E. Does digital imaging decrease patient dose? A pilot study and review of the literature. RADIATION PROTECTION DOSIMETRY 2005; 117:204-10. [PMID: 16464833 DOI: 10.1093/rpd/nci718] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The potential for decreasing patient dose is one of the main arguments for the justification of the cost of digital imaging equipment. However, the literature review with respect to patient doses using digital imaging modalities, presents conflicting results. During this study, patients' entrance surface doses were measured for three simple radiographic examinations, in European centres equipped with a computed radiography digital system. Results showed that doses between centres varied from 30% for chest LAT to 250% for chest PA examination. With the digital image quality criteria still under discussion, and with the post-processing parameters and/or image documentations varying, any dose comparisons between conventional/digital systems, as well as dose comparisons between different centre using digital units, are difficult. Clinical trials are required in order to define reference levels associated with quality of digital image necessary to address specific clinical requirements.
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Affiliation(s)
- V Neofotistou
- Medical Physics Department, Athens General Hospital, 11527 Athens, Greece.
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Hamer OW, Völk M, Zorger N, Borisch I, Büttner R, Feuerbach S, Strotzer M. Contrast-Detail Phantom Study for X-ray Spectrum Optimization Regarding Chest Radiography Using a Cesium Iodide-Amorphous Silicon Flat-Panel Detector. Invest Radiol 2004; 39:610-8. [PMID: 15377940 DOI: 10.1097/01.rli.0000138091.96320.f8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
RATIONALE AND OBJECTIVES The purpose of this study evaluating a cesium iodide-amorphous silicon-based flat-panel detector was to optimize the x-ray spectrum for chest radiography combining excellent contrast-detail visibility with reduced patient exposure. MATERIALS AND METHODS A Lucite plate with 36 drilled holes of varying diameter and depth was used as contrast-detail phantom. For 3 scatter body thicknesses (7.5 cm, 12.5 cm, 21.5 cm Lucite) images were obtained at 113 kVp, 117 kVp, and 125 kVp with additional copper filter of 0.2 and 0.3 mm, respectively. For each setting, radiographs acquired with 125 kVp and no copper filter were taken as standard of reference. On soft-copy displays, 3 observers blinded to the exposure technique evaluated the detectability of each aperture in each image according to a 5-point scale. The number of points given to all 36 holes per image was added. The scores of images acquired with filtration were compared with the standard images by means of a multivariate analysis of variance. Radiation burden was approximated by referring to the entrance dose and calculated using Monte Carlo method. RESULTS All 6 evaluated x-ray spectra resulted in a statistically equivalent contrast-detail performance when compared with the standard of reference. The combination 125 kVp with 0.3 mm copper was most favorable in terms of dose reduction (approximately 33%). CONCLUSION Within the constraints of the presented contrast-detail phantom study simulating chest radiography, the CsI/a-Si system enables an addition of up to 0.3 mm copper filtration without the need for compensatory reduction of the tube voltage for providing constant image quality. Beam filtration reduces radiation burden by about 33%.
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Affiliation(s)
- Okka W Hamer
- Department of Diagnostic Radiology, University Hospital of Regensburg, Regensburg, Germany.
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Hamer OW, Strotzer M, Zorger N, Paetzel C, Lerch K, Feuerbach S, Völk M. Amorphous Silicon, Flat-Panel, X-ray Detector. Invest Radiol 2004; 39:271-6. [PMID: 15087721 DOI: 10.1097/01.rli.0000117853.02516.01] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
RATIONALE AND OBJECTIVES To evaluate composed long-leg images acquired with a large-area, flat-panel x-ray detector with regard to angle and distance measurements. METHODS Radiographs of a long-leg phantom were acquired at 13 different angle settings with a 43-cm x 43-cm digital x-ray detector based on cesium iodide (CsI) and amorphous silicon (a-Si) technology. Three overlapping single images of the phantom were reconstructed at a workstation using a generalized correlation method. Four blinded observers were instructed to determine the angle of the axis of the long-legs as well as the length of "femur" and "tibia" on soft-copy displays. For that, the angle and distance measurement software integrated in the workstation was used. The images were analyzed with and without prior manual fine tuning of the primary composition result according to a mapped scale. Standard of reference was angle and distance determination at the phantom. RESULTS On average, the difference between the observers' angle measurements and the standard of reference was 0.4 degrees for both images with and without prior manual correction. Regarding distance measurements, the average discrepancies to the standard were 0.2 cm (femur) and 0.1 cm (tibia) when analyzing images that had undergone manual fine tuning and 0.5 cm and 0.7 cm, respectively, for images without manual correction. CONCLUSIONS The evaluated image fusion algorithm in conjunction with a 43-cm x 43-cm flat-panel detector is feasible regarding angle and distance measurements on long-leg images. In the case of inaccurate primary composition, results can be corrected easily by manual fine tuning.
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Affiliation(s)
- Okka W Hamer
- Department of Diagnostic Radiology, University Hospital of Regensburg, Regensburg, Germany.
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Völk M, Hamer OW, Feuerbach S, Strotzer M. Dose reduction in skeletal and chest radiography using a large-area flat-panel detector based on amorphous silicon and thallium-doped cesium iodide: technical background, basic image quality parameters, and review of the literature. Eur Radiol 2004; 14:827-34. [PMID: 14968260 DOI: 10.1007/s00330-004-2243-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2003] [Accepted: 01/05/2004] [Indexed: 11/29/2022]
Abstract
The two most frequently performed diagnostic X-ray examinations are those of the extremities and of the chest. Thus, dose reduction in the field of conventional skeletal and chest radiography is an important issue and there is a need to reduce man-made ionizing radiation. The large-area flat-panel detector based on amorphous silicon and thallium-doped cesium iodide provides a significant reduction of radiation dose in skeletal and chest radiography compared with traditional imaging systems. This article describes the technical background and basic image quality parameters of this 43 x 43-cm digital system, and summarizes the available literature (years 2000-2003) concerning dose reduction in experimental and clinical studies. Due to its high detective quantum efficiency and dynamic range compared with traditional screen-film systems, a dose reduction of up to 50% is possible without loss of image quality.
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Affiliation(s)
- Markus Völk
- Department of Diagnostic Radiology, University Hospital of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
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