Radiation dose descriptors: BERT, COD, DAP, and other strange creatures.

Over the years, a number of terms have been used to describe radiation dose. Eight common radiation dose descriptors include background equivalent radiation time (BERT), critical organ dose (COD), surface absorbed dose (SAD), dose area product (DAP), diagnostic acceptable reference level (DARLing), effective dose (ED), fetal absorbed dose (FAD), and total imparted energy (TIE). BERT is compared to the annual natural background radiation (about 3 mSv per year) and is easily understandable for the general public. COD refers to the radiation dose delivered to an individual critical organ. SAD is the radiation dose delivered at the skin surface. DAP is a product of the irradiated surface area multiplied by the radiation dose at the surface. DARLing is usually the radiation level that encompasses 75% (the third quartile) of the data derived from a nationwide or regional survey. DARLings are meant for voluntary guidance. Consistently higher patient doses should be investigated for possible equipment deficiencies or suboptimal protocols. ED is obtained by multiplying the radiation dose delivered to each organ by its weighting factor and then by adding those values to get the sum. It can be used to assess the risk of radiation-induced cancers and serious hereditary effects to future generations, regardless of the procedure being performed, and is the most useful radiation dose descriptor. FAD is the radiation dose delivered to the fetus, and TIE is the sum of the energy imparted to all irradiated tissue. Each of these descriptors is intended to relate radiation dose ultimately to potential biologic effects. To avoid confusion, the key is to avoid using the terms interchangeably. It is important to understand each of the radiation dose descriptors and their derivation in order to correctly evaluate radiation dose and to consult with patients concerned about the risks of radiation.

New automated fluoroscopic systems for pediatric applications.

Pediatric patients are at higher risk to the adverse effects from exposure to ionizing radiation than adults. The smaller sizes of the anatomy and the reduced X-ray attenuation of the tissues provide special challenges. The goal of this effort is to investigate strategies for pediatric fluoroscopy in order to minimize the radiation exposure to these individuals, while maintaining effective diagnostic image quality. Modern fluoroscopy systems are often entirely automated and computer controlled. In this paper, various selectable and automated modes are examined to determine the influence of the fluoroscopy parameters upon the patient radiation exposures and image quality. These parameters include variable X-ray beam filters, automatic brightness control programs, starting kilovolt peak levels, fluoroscopic pulse rates, and other factors. Typical values of radiation exposure rates have been measured for a range of phantom thicknesses from 5 cm to 20 cm of acrylic. Other factors that have been assessed include spatial resolution, low contrast discrimination, and temporal resolution. The selection menu for various procedures is based upon the examination type, anatomical region, and patient size. For pediatric patients, the automated system can employ additional filtration, special automatic brightness control curves, pulsed fluoroscopy, and other features to reduce the patient radiation exposures without significantly compromising the image quality. The benefits gained from an optimal selection of automated programs and settings for fluoroscopy include ease of operation, better image quality, and lower patient radiation exposures.

Pediatric high KV/filtered airway radiographs: comparison of CR and film-screen systems.

The imaging of pediatric airways presents a challenge because of the superimposition of the airway over the bone of the spine on the AP view. In recent years, some radiology departments have replaced conventional X-ray films by computed radiography (CR). The effect of the various changes upon image quality and radiation doses has not been clearly demonstrated. The goal of this paper was to investigate and identify potential improvements and/or degradations to pediatric airways imaging from the application of new technology, in particular to high KV/filtered radiographs; a new filter was designed. Two modern film-screen combinations and a CR system were evaluated for a range of tube potentials from 60 to 140 kVp. The spatial resolutions were measured for different geometrical magnifications. Relative radiation doses were also determined. Clinical airway images of children taken with the different imaging methods were subjectively compared. Our study confirmed that the visualization of the pediatric airways is enhanced by using high X-ray tube potentials with proper X-ray beam filtration. For CR systems, the selection of the cassette size, cassette type, focal spot, and geometrical magnification impact upon the image quality. Despite the increased dynamic range and image processing advantage with CR systems, CR techniques need to be improved to be more comparable with high kVp filtered magnification radiographs using film screens and small X-ray tube focal spots. With appropriate X-ray beam filtration and high kVp's, CR image receptors can provide adequate image quality for pediatric airway imaging. However, the transition to digital radiography involves certain caveats. In general, radiation doses with CR systems are greater than typical doses with film-screen systems.