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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Standard table top for adults. a Overhead view with an infant centered on the table top. b Table top with extension constructed of carbon fiber on the narrow head region of the table top, which allows correct positioning of an infant or toddler and lateral image receptor. For safety reasons, this extension should not be wider than the narrow head region of the standard table-top, and a means of securing the patient to the narrow table top must be provided (reprinted with permission from RSNA [44])
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Fig11: Standard table top for adults. a Overhead view with an infant centered on the table top. b Table top with extension constructed of carbon fiber on the narrow head region of the table top, which allows correct positioning of an infant or toddler and lateral image receptor. For safety reasons, this extension should not be wider than the narrow head region of the standard table-top, and a means of securing the patient to the narrow table top must be provided (reprinted with permission from RSNA [44])

Mentions: Figure 11 illustrates the shape of a standard table top for adults as viewed from overhead. The torso region is substantially wider than a small child, which introduces geometric magnification if the patient is positioned on the center-line of the table top. If the unit contains a nominal 0.3-mm focal spot and the grid can be removed, this is not an issue. If the grid is fixed or the small focal spot is larger than 0.3 mm, this geometric setup increases patient dose and geometric unsharpness in the image. These problems can be avoided by putting a form-fitted extension constructed of carbon fiber material [36] on the narrow head region of the table top. This extension allows proper positioning of the patient and lateral image receptor as illustrated in Fig. 11. This extension should not be wider than the narrow head region of the standard table top to discourage cantilevering larger patients too far from the pedestal support of the table; these table tops are not designed to support heavy loads concentrated at their head ends. A means of securing the small patient to the narrow table top extension must be provided.Fig. 11


Pediatric interventional radiography equipment: safety considerations.

Strauss KJ - Pediatr Radiol (2006)

Standard table top for adults. a Overhead view with an infant centered on the table top. b Table top with extension constructed of carbon fiber on the narrow head region of the table top, which allows correct positioning of an infant or toddler and lateral image receptor. For safety reasons, this extension should not be wider than the narrow head region of the standard table-top, and a means of securing the patient to the narrow table top must be provided (reprinted with permission from RSNA [44])
© Copyright Policy
Related In: Results  -  Collection

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

Fig11: Standard table top for adults. a Overhead view with an infant centered on the table top. b Table top with extension constructed of carbon fiber on the narrow head region of the table top, which allows correct positioning of an infant or toddler and lateral image receptor. For safety reasons, this extension should not be wider than the narrow head region of the standard table-top, and a means of securing the patient to the narrow table top must be provided (reprinted with permission from RSNA [44])
Mentions: Figure 11 illustrates the shape of a standard table top for adults as viewed from overhead. The torso region is substantially wider than a small child, which introduces geometric magnification if the patient is positioned on the center-line of the table top. If the unit contains a nominal 0.3-mm focal spot and the grid can be removed, this is not an issue. If the grid is fixed or the small focal spot is larger than 0.3 mm, this geometric setup increases patient dose and geometric unsharpness in the image. These problems can be avoided by putting a form-fitted extension constructed of carbon fiber material [36] on the narrow head region of the table top. This extension allows proper positioning of the patient and lateral image receptor as illustrated in Fig. 11. This extension should not be wider than the narrow head region of the standard table top to discourage cantilevering larger patients too far from the pedestal support of the table; these table tops are not designed to support heavy loads concentrated at their head ends. A means of securing the small patient to the narrow table top extension must be provided.Fig. 11

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