Determination of Image Quality in Relation to Absorbed Dose in Mammography

1993 ◽  
Vol 49 (1-3) ◽  
pp. 157-161 ◽  
Author(s):  
J. Zoetelief ◽  
J.Th.M. Jansen ◽  
N.J.P. de Wit
Keyword(s):  
1993 ◽  
Vol 49 (1-3) ◽  
pp. 157-161 ◽  
Author(s):  
J. Zoetelief ◽  
J.Th.M. Jansen ◽  
N.J.P. de Wit
Keyword(s):  

1997 ◽  
Vol 38 (6) ◽  
pp. 1010-1014
Author(s):  
J. Persliden ◽  
P. Larsson ◽  
B. Noren ◽  
S. Wirell
Keyword(s):  

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Juha I. Peltonen ◽  
Touko Kaasalainen ◽  
Mika Kortesniemi

Abstract Background Cone-beam computed tomography (CBCT) has become an increasingly important medical imaging modality in orthopedic operating rooms. Metal implants and related image artifacts create challenges for image quality optimization in CBCT. The purpose of this study was to develop a robust and quantitative method for the comprehensive determination of metal artifacts in novel CBCT applications. Methods The image quality of an O-arm CBCT device was assessed with an anthropomorphic pelvis phantom in the presence of metal implants. Three different kilovoltage and two different exposure settings were used to scan the phantom both with and without the presence of metal rods. Results The amount of metal artifact was related to the applied CBCT imaging protocol parameters. The size of the artifact was moderate with all imaging settings. The highest applied kilovoltage and exposure level distinctly increased artifact severity. Conclusions The developed method offers a practical and robust way to quantify metal artifacts in CBCT. Changes in imaging parameters may have nonlinear effects on image quality which are not anticipated based on physics.


1997 ◽  
Vol 16 (11) ◽  
pp. 667-672 ◽  
Author(s):  
S. Halbach ◽  
L. Kremers ◽  
H. Willruth ◽  
A. Mehl ◽  
G. Welzl ◽  
...  

The number of amalgam-covered surfaces and the occlusal area of the fillings, the concentrations of total mercury in plasma, erythrocytes and urine, the urinary excretion rate, and the absorbed daily doses estimated by two separate methods from intra-oral Hg emission were determined in 29 volunteers with a low amalgam load. The transfer ofHg from the fillings via the oral cavity and blood to urinary excretion was evaluated by multiple correla tions between these variables. In addition, the combina tion of variables most representative of the entire compartmental transfer of amalgam Hg was determined. Urinary excretion (1), Hg concentration in plasma (2) and absorbed dose (3) were most closely correlated to each other, followed by correlations with the variables of the fillings (4). Correlation coefficients were 0.75 for variables 1 vs 2 and 2 vs 3, and 0.49 for variables 3 vs 4. It was concluded that variables 1-3 best reflected the transfer of mercury from amalgam fillings throughout the organism and that they were relatively insensitive to dietary mercury. The determination of total mercury in plasma and of its urinary excretion rate appears, under practical aspects, most suitable for the investigation of Hg uptake from amalgam.


2005 ◽  
Vol 48 (spe2) ◽  
pp. 221-228 ◽  
Author(s):  
José Araújo dos Santos Júnior ◽  
Jorge João Ricardo Ferreira Cardoso ◽  
Cleomacio Miguel da Silva ◽  
Suêldo Vita Silveira ◽  
Romilton dos Santos Amaral

Potassium-40 was determined in soil in an area with 40,000 m² situated in the western State of Pernambuco, Brazil. For radiometric measurements, the gamma spectrometry method with a high purity germanium (HPGe) detector was used. Sampling of 78 soil samples has been performed at intervals of 25 m. The specific activities of 40K were calculated based on the photopeak of 1.46 MeV. Values from 541 to 3,572 Bq kg-1 were obtained (mean of 1,827 Bq kg-1). These values allowed the determination of the elemental concentrations as well as the absorbed dose rates in air, 1 m above the ground. The values varied from 1.7 to 11.5% (mean of 6%) and from 23.4 to 154.3 nGy h-1 (mean of 79 nGy h-1), respectively.


1997 ◽  
Vol 38 (6) ◽  
pp. 1010-1014 ◽  
Author(s):  
J. Persliden ◽  
P. Larsson ◽  
B. Norén ◽  
S. Wirell

Purpose: Image quality and the absorbed dose to the patient are issues of primary interest in the change-over from the conventional analogue technique to the digital technique in the examination of the colon by means of fluoroscopy. the aim of this study was to compare the incident radiation and to evaluate the image quality in two different X-ray equipment types, one digital and one analogue Material and Methods: A kerma-area product meter was used to measure the incident radiation to the patient. Both fluoroscopy and total-examination times were measured as was the number of images. an evaluation of image quality was made and statistically analysed Results and Conclusion: No significant difference in the irradiation dose was observed between the two techniques. the fluoroscopy time was significantly lower with the conventional technique but the total-examination time decreased by 18% with the digital technique. the total number of images taken was higher with the digital technique (25 images compared to 19) owing to the limited field of the image intensifier. Significantly more noise and less sharpness were observed with the digital system but there was no significant difference in contrast or image quality in the various anatomical structures. Although the change-over to the digital system produced a reduction in sharpness and an increase in noise, and no significant dose saving was measured, the digital system was faster to work with and could well be used for diagnostic purposes


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