Limits...
Pediatric interventional radiography equipment: safety considerations.

Strauss KJ - Pediatr Radiol (2006)

Bottom Line: The range of pulse widths must be limited to less than 10 ms in children to properly freeze patient motion.Three focal spots with nominal sizes of 0.3 mm to 1 mm are necessary on the pediatric unit.A second, lateral imaging plane might be necessary because of the child's limited tolerance of contrast medium.

View Article: PubMed Central - PubMed

Affiliation: Radiology Physics and Engineering, Children's Hospital Boston, Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA. Keith.Strauss@tch.harvard.edu

ABSTRACT
This paper discusses pediatric image quality and radiation dose considerations in state-of-the-art fluoroscopic imaging equipment. Although most fluoroscopes are capable of automatically providing good image quality on infants, toddlers, and small children, excessive radiation dose levels can result from design deficiencies of the imaging device or inappropriate configuration of the equipment's capabilities when imaging small body parts. Important design features and setup choices at installation and during the clinical use of the imaging device can improve image quality and reduce radiation exposure levels in pediatric patients. Pediatric radiologists and cardiologists, with the help of medical physicists, need to understand the issues involved in creating good image quality at reasonable pediatric patient doses. The control of radiographic technique factors by the generator of the imaging device must provide a large dynamic range of mAs values per exposure pulse during both fluoroscopy and image recording as a function of patient girth, which is the thickness of the patient in the posterior-anterior projection at the umbilicus (less than 10 cm to greater than 30 cm). The range of pulse widths must be limited to less than 10 ms in children to properly freeze patient motion. Variable rate pulsed fluoroscopy can be leveraged to reduce radiation dose to the patient and improve image quality. Three focal spots with nominal sizes of 0.3 mm to 1 mm are necessary on the pediatric unit. A second, lateral imaging plane might be necessary because of the child's limited tolerance of contrast medium. Spectral and spatial beam shaping can improve image quality while reducing the radiation dose. Finally, the level of entrance exposure to the image receptor of the fluoroscope as a function of operator choices, of added filter thickness, of selected pulse rate, of the selected field-of-view and of the patient girth all must be addressed at installation.

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Low-energy X-rays less than 33 keV (hatched region) are absorbed by the patient’s tissues. The high-energy X-rays greater than 45 keV (black region) contribute to patient dose and generate scattered photons that mask subject contrast. Ideally, both shaded regions of the X-ray beam spectrum should be eliminated (reprinted with permission from RSNA [44])
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Fig7: Low-energy X-rays less than 33 keV (hatched region) are absorbed by the patient’s tissues. The high-energy X-rays greater than 45 keV (black region) contribute to patient dose and generate scattered photons that mask subject contrast. Ideally, both shaded regions of the X-ray beam spectrum should be eliminated (reprinted with permission from RSNA [44])

Mentions: Spectral beam shaping is the change in quality (shape) of the X-ray beam spectrum to match the attenuation curve of iodine-filled blood vessels (Fig. 7, dashed line). Peak attenuation by the iodine–the peak radiopacity of the blood vessels, or maximum subject contrast–occurs at 33–2 keV, a small range of energies just greater than the k shell binding energy of iodine.Fig. 7


Pediatric interventional radiography equipment: safety considerations.

Strauss KJ - Pediatr Radiol (2006)

Low-energy X-rays less than 33 keV (hatched region) are absorbed by the patient’s tissues. The high-energy X-rays greater than 45 keV (black region) contribute to patient dose and generate scattered photons that mask subject contrast. Ideally, both shaded regions of the X-ray beam spectrum should be eliminated (reprinted with permission from RSNA [44])
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2663646&req=5

Fig7: Low-energy X-rays less than 33 keV (hatched region) are absorbed by the patient’s tissues. The high-energy X-rays greater than 45 keV (black region) contribute to patient dose and generate scattered photons that mask subject contrast. Ideally, both shaded regions of the X-ray beam spectrum should be eliminated (reprinted with permission from RSNA [44])
Mentions: Spectral beam shaping is the change in quality (shape) of the X-ray beam spectrum to match the attenuation curve of iodine-filled blood vessels (Fig. 7, dashed line). Peak attenuation by the iodine–the peak radiopacity of the blood vessels, or maximum subject contrast–occurs at 33–2 keV, a small range of energies just greater than the k shell binding energy of iodine.Fig. 7

Bottom Line: The range of pulse widths must be limited to less than 10 ms in children to properly freeze patient motion.Three focal spots with nominal sizes of 0.3 mm to 1 mm are necessary on the pediatric unit.A second, lateral imaging plane might be necessary because of the child's limited tolerance of contrast medium.

View Article: PubMed Central - PubMed

Affiliation: Radiology Physics and Engineering, Children's Hospital Boston, Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA. Keith.Strauss@tch.harvard.edu

ABSTRACT
This paper discusses pediatric image quality and radiation dose considerations in state-of-the-art fluoroscopic imaging equipment. Although most fluoroscopes are capable of automatically providing good image quality on infants, toddlers, and small children, excessive radiation dose levels can result from design deficiencies of the imaging device or inappropriate configuration of the equipment's capabilities when imaging small body parts. Important design features and setup choices at installation and during the clinical use of the imaging device can improve image quality and reduce radiation exposure levels in pediatric patients. Pediatric radiologists and cardiologists, with the help of medical physicists, need to understand the issues involved in creating good image quality at reasonable pediatric patient doses. The control of radiographic technique factors by the generator of the imaging device must provide a large dynamic range of mAs values per exposure pulse during both fluoroscopy and image recording as a function of patient girth, which is the thickness of the patient in the posterior-anterior projection at the umbilicus (less than 10 cm to greater than 30 cm). The range of pulse widths must be limited to less than 10 ms in children to properly freeze patient motion. Variable rate pulsed fluoroscopy can be leveraged to reduce radiation dose to the patient and improve image quality. Three focal spots with nominal sizes of 0.3 mm to 1 mm are necessary on the pediatric unit. A second, lateral imaging plane might be necessary because of the child's limited tolerance of contrast medium. Spectral and spatial beam shaping can improve image quality while reducing the radiation dose. Finally, the level of entrance exposure to the image receptor of the fluoroscope as a function of operator choices, of added filter thickness, of selected pulse rate, of the selected field-of-view and of the patient girth all must be addressed at installation.

Show MeSH
Related in: MedlinePlus