Optimisation in fluoroscopy

Abstract

Optimisation of radiation protection in fluoroscopy is important since the procedure could lead to relatively high absorbed doses both in patients and personnel resulting in acute radiation injury. Optimisation procedures include adjustment of the fluoroscopy equipment such as exposure factors as well as proper use of automatic brightness control and pulsed fluoroscopy. It is also important to gain the benefits of image processing and the higher sensitivity of flat panel detectors as compared to image intensifier-TV systems.Proper positioning of the patient with respect to detector and X-ray tube is of fundamental importance to image quality and radiation dose to the patient. Both image quality and radiation dose are also affected by the methodology used with parameters such as magnification factor, increased filtration, use of last-image-hold and the use of a grid.There is a direct relation between patient dose and the absorbed dose to the personnel since this is mostly due to scattered radiation from the patient. If the correct methodology and the correct radiation protection devices are used, the absorbed dose to the personnel could be minimised to acceptable levels even for those working with complex procedures.In order to have an organised review of all aspects of optimisation, it is recommendable to have an active quality system at the department. This system should define responsibilities and tasks for persons involved.

Keywords: Radiation protection; dose reduction; fluoroscopy; patient dose.

Figure 1

Different modes of operation for the regulation of tube voltage and tube current using automatic brightness control.

Figure 2

Example of dose levels for continuous and pulsed fluoroscopy.

Figure 3

Entrance skin dose level dependent on patient thickness, tube voltage and focus-skin distance. For tube voltage 70 kV and focus-skin distance 70 cm (♦), 100kV, 70cm (■), 70 kV,40cm (▲). This figure gives an example. The actual dose rate depends on setting of the ABC.