Abstract

Objective: To test the hypothesis that replacing the antiscatter grid with an air gap will reduce patient radiation exposure without significant compromise of image quality.

Methods: 457 patients having either uncomplicated diagnostic studies or a single vessel angioplasty (percutaneous transluminal coronary angioplasty (PTCA)) on a flat plate system (GE Innova) were studied. For two months their total dose–area product score was recorded on standard gridded images and then for two months on images made with the grid out, with an air gap used to reduce scatter. Detector magnification was reduced one step when an air gap was used to achieve the same final image size. A sample set of studies was reviewed blind by five observers, who scored sharpness and contrast on a non-linear scale.

Results: The average dose–area product was significantly reduced, both in the diagnostic group (n  =  276), from a mean (SD) of 26.2 (14.7) Gy·cm² with the grid in to 16.1 (12) Gy·cm² with the grid out (p  =  0.01), and in the PTCA group (n  =  181), from 48.2 (36.2) to 37 (27.5) (p  =  0.01). The mean image quality scores of the gridless cohort were not significantly different from those of the gridded cohort.

Conclusion: With the use of a flat plate detector, air gap gridless angiography reduces the radiation dose to the patient and, in consequence, to the operator without significantly affecting image quality. It is proposed that gridless imaging should be the default technique for adults and children and in most installations.