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Optimization of radiographic parameters for paediatric cardiac angiography

Paediatric Cardiology and Biomedical Engineering, University of Kiel, Schwanenweg 20, 24105 Kiel, Germany

View larger version (89K): [in a new window]   Figure 1. Biplane images from a cardiac angiogram (recorded at 25 frames s–1, 23 cm field of view, using a grid and 0.4 mm Cu filtration, after injection of 20 ml Imagopaque 350 (Amersham Health, Princeton)) of a 6-year-old boy (32 kg), treated as an infant because of transposition of the great arteries, showing the end-systolic state of the left ventricle in two views: (a) 10° caudal/16° right anterior oblique, source–image distance (SID) 92 cm, 66 kV, 428 mA, 4 ms; (b) 19° cranial/70° left anterior oblique, SID 107 cm, 70 kV, 497 mA, 5 ms. The mean brightness levels are indicated for 8 regions of interest.

View larger version (22K): [in a new window]   Figure 2. Automatic exposure control curves P1 to P6 configured to arrive at a variety of tube voltages for angiographic acquisitions.

View larger version (17K): [in a new window]   Figure 3. The irradiation geometry. The semiconductor dosemeter is fixed 9 cm below the phantom, composed of polymethylmethacrylate plates and a contrast structure.

View larger version (39K): [in a new window]   Figure 4. The test structure consisting of a copper step wedge, a strip of aluminium and a piece of lead. The radiation detector projected right, below the step wedge.

View larger version (81K): [in a new window]   Figure 5. Comparison of two images of the 11 cm phantom, recorded under different radiographic parameters (see Table 1). For identifying the steps S0 to S5 of the step wedge see Figure 4 for comparison.

View larger version (14K): [in a new window]   Figure 6. Entrance dose versus X-ray voltage for the four objects (circles: 8 cm; squares: 11 cm; rhombi: 15.5 cm; and triangles: 18.5 cm) recorded with a grid using the automatic exposure control programs P1 to P6. Solid lines: 0.2 mm Cu filtering (programs P2, P4, P6, from left to right); dashed lines: 0.4 mm Cu filtering (programs P3, P5, P1, from left to right).

View larger version (17K): [in a new window]   Figure 7. The signal-to-noise ratios SNRb (triangles) and SNRd (squares) of the images recorded with 0.2 mm (filled symbols) and 0.4 mm Cu filtering (open symbols). All data from radiographs with an anti-scatter grid.