Improvements in computed technology continue to attract attention.The new development is a new type of storage phosphor material based on a translucent glass-ceramic imaging plate.One of the attractions of the technology is that the image receptor can be substituted at existing equipment without changing the associated x-ray equipment.
K.S.Parthasarathy
Siemens
New CR technology boosts resolution, bags R&D award
9/3/2007
http://www.auntminnie.com/print/print.asp?sec=sup&sub=xra&pag=dis&ItemId=77337&printpage=true
By: Brian Casey
U.S. researchers have developed a new type of computed radiography (CR) technology that they believe could yield much higher resolution than existing CR systems. One prominent scientific magazine thought enough of their research to name it one of the top 100 scientific innovations for 2007.
Computed radiography has made impressive gains in achieving commercial acceptance in the last 25 years, but the fundamental technology behind CR remains the same -- photons produced by an x-ray generator are sent through a patient and captured on a storage phosphor plate that's coated with a powder that typically consists of barium fluorobromide doped with europium. The imaging plate is then taken to a laser scanner, where electrons stored in the plates are converted into light, then read out and converted into digital images.
But some industry observers believe that CR has reached a plateau in terms of improving on this basic design, and as a result its image quality has been surpassed by digital radiography (DR) units based on flat-panel technology, according to a research group that includes scientists from Argonne National Laboratory in Argonne, IL, and the State University of New York (SUNY) at Stony Brook. To improve on CR, the group developed a new type of storage phosphor material based on a translucent glass-ceramic imaging plate.
The SUNY/Argonne technology could offer much higher resolution than current CR systems, and could be used to retrofit existing x-ray rooms in the same way as CR, without requiring a new x-ray generator and other equipment, according to Anthony Lubinsky, who represented SUNY on the research team. Lubinsky is a former employee at Eastman Kodak Health Group (now Carestream Health of Rochester, NY), and has been working on CR technology for the past 20 years.
"It would be as easy to make the switch (to digital) for your x-ray room as it is with CR in the ordinary practice," Lubinsky said. "What's inside the cassette is different and what's inside the scanner box is also different, but to the user it works the same way."
See-through CR?
The heart of the new technology is a CR design developed at SUNY and Argonne National Laboratory that the group calls transparent storage phosphor (TSP). TSP is based on a photostimulable material that employs fluorozirconate rather than barium fluorobromide. Rather than coat an imaging plate with the fluorozirconate, the material is used in combination with europium-doped barium nanocrystals to create a composite glass imaging plate.
Experimental setup of x-ray imaging system for testing fluorochlorozirconate glass-ceramic imaging plates.
The SUNY/Argonne design results in a detector material that's translucent, rather than the opaque powder screen used today with CR. As a result, a point of light entering the imaging plate doesn't scatter as much as it does with conventional imaging plates, resulting in a higher modulation transfer function (MTF). That means that a manufacturer developing a CR system based on the SUNY/Argonne technology could make the imaging plate much thicker than one based on barium fluorobromide or some other type of powder, with correspondingly higher spatial resolution.
How much higher? The group has fashioned imaging plates with a resolution of 17 microns, compared with 70 microns for amorphous selenium-based DR and 100-200 microns for conventional CR, according to Jacqueline A. Johnson of Argonne National Laboratory. The group points out that the 17-micron specification was achieved in a test environment and with a radiation dose that's much higher than would be used clinically.
Phantom image collected with tabletop CR system. Parallel vertical lines represent gold bars at spatial frequencies of 19 line pairs (left) and 20 line pairs (right) per mm. All images courtesy of Argonne National Laboratory.
One of the most obvious applications for the SUNY/Argonne technology in the clinical realm would be mammography, in which CR units based on conventional technology are entering clinical use in the U.S. after the Food and Drug Administration's 2006 approval of the first CR mammography unit, from Fujifilm Medical Systems USA of Stamford, CT. Argonne's technology could give mammographers an even finer level of detail than conventional CR.
But the Argonne team believes that its technology could have a wide range of applications in medical imaging. "If it works for mammography, I would hope the resolution would be helpful in the extremities as well," Lubinsky said.
However, you won't see the SUNY/Argonne technology in a commercially available CR system anytime soon. At present, the group has built a tabletop system and collected phantom images, and their next step is to develop a working prototype. The research team estimates that it could be more than five years before the technology hits clinical users, due to the vagaries of technology development and the need to move such a system through the FDA approval process.
If the technology does make it into the commercial marketplace, it wouldn't be totally plug-and-play with existing CR systems. Although the technology could be used with existing x-ray generators and gantries, the TSP plates would require specially adapted scanners for reading the plates, according to Lubinsky.
But the SUNY/Argonne's team work was promising enough to catch the attention of R&D Magazine, which named the research one of the top 100 scientific innovations of 2007, based on the group's March 2007 paper in the Journal of the American Chemical Society (Vol. 90:3, pp. 693-698). The award will be announced in the magazine's September issue.
The development of a translucent CR imaging plate is not a new idea: "It's something that people have thought of as a great idea if you could do it," Lubinsky said. But the SUNY/Argonne group's major achievement has been in developing both a translucent imaging plate and the concept of a laser scanner to read out the images.
"The trick is to get the (TSP and readout technologies) working together so well," he said.
By Brian Casey
AuntMinnie.com staff writer
September 3, 2007
Related Reading
PACS data-mining technique tackles CR dose creep, July 30, 2007
DICOM-compliant displays aid CR/DR exposure control, July 17, 2007
CR/DR image quality: Issues and concerns, April 12, 2007
Strategies for reducing 'dose creep' in digital x-ray, April 11, 2007
Study suggests ways to cut CR radiation, March 5, 2007
Copyright © 2007 AuntMinnie.com
Wednesday, August 29, 2007
Ways to cut radiation dose in computed tomography
Any one who is involved in radiological protection cannot ignore the development which involves reduction in radiation doses in computed tomography (CT).CT examinations are exposing patients to doses in the range in which the survivors of atomic bombings suffered excess cancers.
K.S.Parthasarathy
Siemens
Study suggests ways to cut CR radiation
3/5/2007
http://www.auntminnie.com/print/print.asp?sec=sup&sub=xra&pag=dis&ItemId=74868&printpage=true
By: Leanne McKnoulty
A new study by Australian researchers has found that the radiation dose delivered in computed radiography (CR) examinations could be cut in half by adjusting the manufacturers recommended range (MRR) for exposure indices (EIs) by as little as 10%.
The arrival of CR has given radiographers (radiologic technologists) the ability to use a greater range of radiation exposures to produce diagnostic images, the article states. Because, unlike film-screen radiography, higher-than-appropriate exposures in CR result in better-quality images due to increased signal-to-noise ratio, and "radiographers develop a tendency to use higher than necessary exposure factors to improve image quality and avoid repeat radiographs."
To safeguard against overexposure, CR manufacturers each set their own exposure indicators -- numerical parameters that are estimates of radiation exposure on imaging plates. The feature is called EI on systems manufactured by Eastman Kodak Health Group of Rochester, NY, and sensitivity value (S) on units made by Fujifilm Medical Systems of Tokyo.
Dr. Helen Warren-Forward and colleagues at the University of Newcastle set out to explore whether radiographers were in fact producing images using EIs within the MRR. They also sought to investigate any evidence of "exposure creep," and the relationship between EIs and radiation dose using fixed and varying tube potential, in the hope that this knowledge would ensure the use of techniques that minimize radiation dose. The study was published in the British Journal of Radiology (January 2007, Vol. 80:949, pp. 26-31).
The researchers retrospectively assessed CR data for posteroanterior (PA) chest and lateral (LAT) lumbar spine imaging, from two hospitals, denoted as hospital A and hospital B, using the CR-800 and CR-850 systems (Eastman Kodak), during an 18-month period from January 2004.
The researchers selected PA chest data because, in Australian hospitals, this is the most frequently performed examination. LAT lumbar spine data were selected because the researchers felt this represented a high entrance surface dose examination. Also, these two examinations provided a contrast in exposure factors, body part, and positioning technique, they stated.
Although manufacturers of CR equipment recommend certain "exposure indicators," the researchers highlighted that higher tube potentials and lower mAs reduce patient radiation dose compared with lower tube potentials and higher mAs. "Therefore, it cannot be assumed that there is a good correlation between exposure index and patient doses," they wrote.
Using a lung/chest phantom (model CNR/R5330, Oxford Scientific, Silverwater, Australia), the researchers showed that for a fixed tube potential (125 kVp), without any change in other parameters, EI correlates with entrance-surface dose (ESD) -- there is a log relationship in dose and EI in CR. So, a small increase in EI results in a large increase in ESD. Additionally, the researchers investigated the relationship among a varied tube potential, EI, and patient dose. They found that an increasing tube potential and a decreasing mAs for a constant EI (1500) resulted in decreasing ESD.
"The results from this current study strongly suggest that EI should not be used as an indication of ESD when comparing examinations conducted between different radiographers and institutions using different tube potentials," they wrote.
The authors caution that, particularly for chest imaging, a number of factors can affect patient dose, in particular tube potential. Therefore, EI should only be used to indicate ESD for examinations within a specific department performed by the same radiographers. They found no significant variation in EIs when they compared CR imaging during normal operational hours with after-hours services.
EIs lower than the MRR, 1700-1900 for Kodak CR systems, were successfully used for 30% of LAT lumbar spine examinations at hospital B and 38% of PA chest examinations at hospital A. "This implies that the MRR may be set too high and can be reduced to values less than 1700," they wrote.
More than two-thirds of PA chest examinations performed at hospital B, but less than one-third at hospital A, were produced with EIs within the MRR. Almost half of LAT lumbar spine examinations performed at hospital B were produced with EIs within the MRR, but almost half at hospital A were above the MRR.
Using the lung/chest phantom to produce suitable diagnostic images, EIs were 1550. The researchers suggest that since a reduction in EI by 300 results in half the patient dose, reducing MRR values from 1770-1900 to 1530-1700 (a 10% reduction) would result in significant dose savings (50%).
Exposure creep was described by the researchers as a tendency by radiographers to set higher exposures than necessary, knowing that images could be manipulated with postprocessing techniques, to achieve a suitable diagnostic image.
Results demonstrated exposure creep at hospital A, where exposure indices for LAT lumbar spine CR increased 7.1% during the 18-month period. Hospital A also showed a larger range of EIs, probably due to a higher number of patients and staff, resulting in greater variation in radiographic technique, which impacts the EI levels used to produce images, the authors suggested.
The study findings highlight the need for regular staff training on the appropriate use of CR systems and departmental quality assurance programs to ensure staff adopt the ALARA principle, to keep patient doses "as low as reasonably achievable," the researchers stated. They suggested that CR manufacturers should review the acceptable range of EIs recommended.
"The results showed that an EI of 2000 produced at 125 kVp can deliver the same patient dose as an EI of 1700 produced at 70 kVp, where the EI difference of 300 represents a doubling of dose to the detector," they wrote. "EI cannot always be used as an indicator of changes to patient dose, but that a number of other factors (predominately tube potential) need to be considered."
By Leanne McNoulty
AuntMinnie.com contributing writer
March 5, 2007
Related Reading
Korean rads find no edge for high-res CR in chest exams, January 22, 2007
Study: DR delivers lower radiation dose, November 7, 2006
U.S. hospitals find ways to take the digital x-ray plunge, October 12, 2006
AuntMinnie's IMV MarketStat #44: Percentage of U.S. hospitals with DR or CR technology, October 9, 2006
Digital radiography slowly, but surely, makes its mark, July 25, 2006
Copyright © 2007 AuntMinnie.com
K.S.Parthasarathy
Siemens
Study suggests ways to cut CR radiation
3/5/2007
http://www.auntminnie.com/print/print.asp?sec=sup&sub=xra&pag=dis&ItemId=74868&printpage=true
By: Leanne McKnoulty
A new study by Australian researchers has found that the radiation dose delivered in computed radiography (CR) examinations could be cut in half by adjusting the manufacturers recommended range (MRR) for exposure indices (EIs) by as little as 10%.
The arrival of CR has given radiographers (radiologic technologists) the ability to use a greater range of radiation exposures to produce diagnostic images, the article states. Because, unlike film-screen radiography, higher-than-appropriate exposures in CR result in better-quality images due to increased signal-to-noise ratio, and "radiographers develop a tendency to use higher than necessary exposure factors to improve image quality and avoid repeat radiographs."
To safeguard against overexposure, CR manufacturers each set their own exposure indicators -- numerical parameters that are estimates of radiation exposure on imaging plates. The feature is called EI on systems manufactured by Eastman Kodak Health Group of Rochester, NY, and sensitivity value (S) on units made by Fujifilm Medical Systems of Tokyo.
Dr. Helen Warren-Forward and colleagues at the University of Newcastle set out to explore whether radiographers were in fact producing images using EIs within the MRR. They also sought to investigate any evidence of "exposure creep," and the relationship between EIs and radiation dose using fixed and varying tube potential, in the hope that this knowledge would ensure the use of techniques that minimize radiation dose. The study was published in the British Journal of Radiology (January 2007, Vol. 80:949, pp. 26-31).
The researchers retrospectively assessed CR data for posteroanterior (PA) chest and lateral (LAT) lumbar spine imaging, from two hospitals, denoted as hospital A and hospital B, using the CR-800 and CR-850 systems (Eastman Kodak), during an 18-month period from January 2004.
The researchers selected PA chest data because, in Australian hospitals, this is the most frequently performed examination. LAT lumbar spine data were selected because the researchers felt this represented a high entrance surface dose examination. Also, these two examinations provided a contrast in exposure factors, body part, and positioning technique, they stated.
Although manufacturers of CR equipment recommend certain "exposure indicators," the researchers highlighted that higher tube potentials and lower mAs reduce patient radiation dose compared with lower tube potentials and higher mAs. "Therefore, it cannot be assumed that there is a good correlation between exposure index and patient doses," they wrote.
Using a lung/chest phantom (model CNR/R5330, Oxford Scientific, Silverwater, Australia), the researchers showed that for a fixed tube potential (125 kVp), without any change in other parameters, EI correlates with entrance-surface dose (ESD) -- there is a log relationship in dose and EI in CR. So, a small increase in EI results in a large increase in ESD. Additionally, the researchers investigated the relationship among a varied tube potential, EI, and patient dose. They found that an increasing tube potential and a decreasing mAs for a constant EI (1500) resulted in decreasing ESD.
"The results from this current study strongly suggest that EI should not be used as an indication of ESD when comparing examinations conducted between different radiographers and institutions using different tube potentials," they wrote.
The authors caution that, particularly for chest imaging, a number of factors can affect patient dose, in particular tube potential. Therefore, EI should only be used to indicate ESD for examinations within a specific department performed by the same radiographers. They found no significant variation in EIs when they compared CR imaging during normal operational hours with after-hours services.
EIs lower than the MRR, 1700-1900 for Kodak CR systems, were successfully used for 30% of LAT lumbar spine examinations at hospital B and 38% of PA chest examinations at hospital A. "This implies that the MRR may be set too high and can be reduced to values less than 1700," they wrote.
More than two-thirds of PA chest examinations performed at hospital B, but less than one-third at hospital A, were produced with EIs within the MRR. Almost half of LAT lumbar spine examinations performed at hospital B were produced with EIs within the MRR, but almost half at hospital A were above the MRR.
Using the lung/chest phantom to produce suitable diagnostic images, EIs were 1550. The researchers suggest that since a reduction in EI by 300 results in half the patient dose, reducing MRR values from 1770-1900 to 1530-1700 (a 10% reduction) would result in significant dose savings (50%).
Exposure creep was described by the researchers as a tendency by radiographers to set higher exposures than necessary, knowing that images could be manipulated with postprocessing techniques, to achieve a suitable diagnostic image.
Results demonstrated exposure creep at hospital A, where exposure indices for LAT lumbar spine CR increased 7.1% during the 18-month period. Hospital A also showed a larger range of EIs, probably due to a higher number of patients and staff, resulting in greater variation in radiographic technique, which impacts the EI levels used to produce images, the authors suggested.
The study findings highlight the need for regular staff training on the appropriate use of CR systems and departmental quality assurance programs to ensure staff adopt the ALARA principle, to keep patient doses "as low as reasonably achievable," the researchers stated. They suggested that CR manufacturers should review the acceptable range of EIs recommended.
"The results showed that an EI of 2000 produced at 125 kVp can deliver the same patient dose as an EI of 1700 produced at 70 kVp, where the EI difference of 300 represents a doubling of dose to the detector," they wrote. "EI cannot always be used as an indicator of changes to patient dose, but that a number of other factors (predominately tube potential) need to be considered."
By Leanne McNoulty
AuntMinnie.com contributing writer
March 5, 2007
Related Reading
Korean rads find no edge for high-res CR in chest exams, January 22, 2007
Study: DR delivers lower radiation dose, November 7, 2006
U.S. hospitals find ways to take the digital x-ray plunge, October 12, 2006
AuntMinnie's IMV MarketStat #44: Percentage of U.S. hospitals with DR or CR technology, October 9, 2006
Digital radiography slowly, but surely, makes its mark, July 25, 2006
Copyright © 2007 AuntMinnie.com
Wednesday, August 15, 2007
Informational hand out on computed tomography to parents
Since computed tomogaphy exposes patients to significant radiation doses, physicians must use them after due consideration.They must carry out CT tests only if they are clinically indicated.Children are more sensitive to radiation so use of CT for pediatric examination must receive more attention.
Dr.K.S.Parthasarathy
Contact: Necoya Lightsey
necoya@arrs.org
703-858-4304
American Roentgen Ray Society
Informational handout key to giving parents a better understanding of CT radiation risks
Simply giving parents informational handouts can improve their understanding of the potential increased risk of cancer related to pediatric CT, according to a recent study conducted by researchers from The Children’s Hospital in Denver, CO and Yale University School of Medicine in New Haven, CT.
“Like many radiology departments around the country, we are concerned about the increasing radiation exposure to children caused by increased usage of CT. When we looked into it, our emergency physicians told us that parents' expectations may play a role,” said David B. Larson, MD, lead author of the study. “The emergency room clinicians tell us anecdotally that a number of parents expect that their child will undergo CT even before the child is seen by a physician. Parents rarely seem to understand the associated risks, so we thought it might be helpful to our emergency room colleagues to provide a handout to parents to explain, in basic terms, the risks associated with CT,” said Dr. Larson.
The study consisted of 100 parents of children undergoing non-emergent CT studies who were surveyed before and after reading an informational handout that described radiation risks. Of the 100 parents surveyed, 66% believed that CT uses radiation; 99% afterwards. 13% of those surveyed before reading the handout believed CT increases the lifetime risk of cancer, versus 86% surveyed afterward.
According to the study, after reading the handout, parents became less willing to have their child undergo a CT examination if their doctor believed that either CT or observation would be equally effective. Their willingness to have their child undergo CT recommended by their doctor did not significantly change. No parent refused or requested to defer CT after reading the handout.
“While most parents knew that CT uses radiation, we were surprised to find that most parents did not realize that this radiation exposure is associated with an increased risk of cancer,” said Dr. Larson.
“While we were working on the handout, we found it extremely difficult to find meaningful estimates of exposure, dose, and risk for various types of procedures--even in the radiology literature. It is then not surprising that not only do parents underestimate the risk, but so do clinicians and radiologists,” he said. “When addressing the question of ‘how much does a CT increase the risk of cancer"” rather than providing a meaningful basis of comparison, most publications give one of two responses; either ‘the risk is slight’ or ‘it depends.’ While both may be accurate, neither are very helpful,” he said.
“Even though risk estimates are fraught with uncertainty, a reasonable quantitative estimate is an improvement upon ‘slight’,” said Dr. Larson. “If radiologists expect clinicians to have these discussions with their patients, then we need to do a better job discussing this subject amongst ourselves and with clinicians. We believe such information should be straightforward, accurate, and widely available,” he said.
###
The full results of this study appear in the August issue of the American Journal of Roentgenology, published by the American Roentgen Ray Society.
[ Back to EurekAlert! ] [ Print Article Print Article | E-mail Article | Close Window | Close Window ]
Dr.K.S.Parthasarathy
Contact: Necoya Lightsey
necoya@arrs.org
703-858-4304
American Roentgen Ray Society
Informational handout key to giving parents a better understanding of CT radiation risks
Simply giving parents informational handouts can improve their understanding of the potential increased risk of cancer related to pediatric CT, according to a recent study conducted by researchers from The Children’s Hospital in Denver, CO and Yale University School of Medicine in New Haven, CT.
“Like many radiology departments around the country, we are concerned about the increasing radiation exposure to children caused by increased usage of CT. When we looked into it, our emergency physicians told us that parents' expectations may play a role,” said David B. Larson, MD, lead author of the study. “The emergency room clinicians tell us anecdotally that a number of parents expect that their child will undergo CT even before the child is seen by a physician. Parents rarely seem to understand the associated risks, so we thought it might be helpful to our emergency room colleagues to provide a handout to parents to explain, in basic terms, the risks associated with CT,” said Dr. Larson.
The study consisted of 100 parents of children undergoing non-emergent CT studies who were surveyed before and after reading an informational handout that described radiation risks. Of the 100 parents surveyed, 66% believed that CT uses radiation; 99% afterwards. 13% of those surveyed before reading the handout believed CT increases the lifetime risk of cancer, versus 86% surveyed afterward.
According to the study, after reading the handout, parents became less willing to have their child undergo a CT examination if their doctor believed that either CT or observation would be equally effective. Their willingness to have their child undergo CT recommended by their doctor did not significantly change. No parent refused or requested to defer CT after reading the handout.
“While most parents knew that CT uses radiation, we were surprised to find that most parents did not realize that this radiation exposure is associated with an increased risk of cancer,” said Dr. Larson.
“While we were working on the handout, we found it extremely difficult to find meaningful estimates of exposure, dose, and risk for various types of procedures--even in the radiology literature. It is then not surprising that not only do parents underestimate the risk, but so do clinicians and radiologists,” he said. “When addressing the question of ‘how much does a CT increase the risk of cancer"” rather than providing a meaningful basis of comparison, most publications give one of two responses; either ‘the risk is slight’ or ‘it depends.’ While both may be accurate, neither are very helpful,” he said.
“Even though risk estimates are fraught with uncertainty, a reasonable quantitative estimate is an improvement upon ‘slight’,” said Dr. Larson. “If radiologists expect clinicians to have these discussions with their patients, then we need to do a better job discussing this subject amongst ourselves and with clinicians. We believe such information should be straightforward, accurate, and widely available,” he said.
###
The full results of this study appear in the August issue of the American Journal of Roentgenology, published by the American Roentgen Ray Society.
[ Back to EurekAlert! ] [ Print Article Print Article | E-mail Article | Close Window | Close Window ]
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