Hand-held X-ray unit generates lower dose of radiation

by Larry Emmott on March 7, 2014

in Radiography

HandHoldingNOMADProWorking2Following is the abstract of some amazing research. You can access it here. It is so counterintuitive. The assumption is that a hand-held unit like the Nomad would create more scatter and higher exposure to workers and patients. Well the research shows just the opposite. Read the whole thing.

A hand-held, battery-powered dental intraoral x-ray system (60 kV, constant potential output) was compared to a conventional, wall-mounted intraoral x-ray system (70 kV, self-rectified output) in terms of image quality, and patient and staff radiation doses.

The image quality comparison includes quantitative measurements of image sharpness (resolution), contrast, and overall image quality plus images of a human jaw phantom.

Patient doses were compared using the jaw phantom and adjusting the radiation dose to obtain the same density on intraoral dental films.

Scattered radiation isodose curves were produced from measurements made for the hand-held x-ray unit with and without a backscatter shield, and for a conventional dental x-ray unit.

Staff radiation doses were measured using personal dosimetry badges for dental facilities for six months using the hand-held system and for six months after allowing accurate comparison of staff doses with both systems under similar workloads and operating conditions.

Results indicate that the image quality for the hand-held system is at least comparable to that of conventional systems, and in some instances superior. A resolution test pattern was placed at the end of the position indicating device (PID) and the film was 2.5 cm away (with a distance of 20 cm from the source to the PID tip). With this geometry the image resolution is 14 c/mm for the hand-held system and 5.5 c/mm for the conventional system. Contrast (with F-Speed film), measured as the density difference, is similar with 0.51 for the Nomad and 0.55 for the conventional system (visual contrast differences in jaw phantom images were not perceptible).

The patient dose-area product is lower for the hand-held system due to its smaller x-ray field size at the entrance surface of the patient. For matched film densities and half-value layers (HVLs) the entrance doses for the Nomad and conventional systems were virtually the same at 1.18 and 1.23 mGy respectively. The dose-area product (DAP) for the Nomad is 30% less than that of the conventional system due to the difference in the diameter of the position-indicator devices (6 cm vs 7 cm).

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