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Relative Threshold of Detection of Active Arterial Bleeding: In Vitro Comparison of MDCT and Digital Subtraction Angiography

Shuvro H. Roy-Choudhury1,2, David J. Gallacher3, John Pilmer3, Sheila Rankin2, Geoff Fowler4, Jeff Steers4, Renato Dourado2, Paul Woodburn2 and Andreas Adam2

1 Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham, B9 5SS, United Kingdom.
2 Department of Radiology, Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom.
3 Department of Medical Physics, Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom.
4 Department of Clinical Perfusion, Guy's and St. Thomas' Foundation NHS Trust, London, United Kingdom.


Figure 1
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  		Fig. 1A —Drawings and photograph show phantom used for experiments. Schematic diagram shows phantom used for experiment. Perfusion pump (P) and oxygenator (O) of a cardiopulmonary bypass circuit were connected to system of tubings to mimic arteriovenous system. Smaller interconnecting tubes (a, b, c) were used to mimic bleeding arteries and were enclosed in sponge sleeves. Tube a had 100-µm hole, tube b had 280-µm hole, and tube c had no holes in it. Contrast material was injected via automatic injector (CI) connected to oxygenator. Pressure was changed with graduated valve (V) and measured with manometer (M). Arrows indicate direction of flow. P1, P2, Q1, and Q2 indicate measurements used for mathematic model outlined in Appendix 1. Briefly, pressure at input to pump is P2, and pressure at output is P1, Q1 is flow in main arterial (aortic) branch, Q2 is flow in each of three arterial branches in acrylic plastic (Perspex, Lucite International) insert. Position of catheter for digital subtraction angiography study is indicated as 1 – selective position and 2 – highly superselective position (see text and tables).

 

Figure 2
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  		Fig. 1B —Drawings and photograph show phantom used for experiments. Schematic diagram with tubings shown in A placed in water bath. Plastic clamp (C) mounted on bath holds smaller arterial tubings (A) at depth of 10 cm. Water bath was filled to 20 cm.

 

Figure 3
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  		Fig. 1C —Drawings and photograph show phantom used for experiments. Image of branch arterial tubings in their sponge sleeves. Empty spaces were filled with sponge (not shown). Straight catheter is noted in highly superselective position at level of hole (arrow). For selective digital subtraction angiography study, catheter was placed in Y connector 10 cm proximal to hole in simulated artery.

 

Figure 4
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  		Fig. 2A —Three-dimensional maximum-intensity-projection images of phantom. Image obtained in arterial phase (A) and image obtained 2 minutes after A (B) show active bleeding from simulated arteries (arrows) that was detected with cardiac output of 4 L/min and mean arterial pressure of 50 mm Hg. Tube on left has 100-µm hole, one in middle has 280-µm hole, and tube on right has no holes. For limitations of this model, see text.

 

Figure 5
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  		Fig. 2B —Three-dimensional maximum-intensity-projection images of phantom. Image obtained in arterial phase (A) and image obtained 2 minutes after A (B) show active bleeding from simulated arteries (arrows) that was detected with cardiac output of 4 L/min and mean arterial pressure of 50 mm Hg. Tube on left has 100-µm hole, one in middle has 280-µm hole, and tube on right has no holes. For limitations of this model, see text.

 

Figure 6
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  		Fig. 3 —Graph shows predicted extravasation rates obtained using mathematic model and actual observed extravasation rates from 100-µm hole plotted against increasing mean arterial pressure. Estimated leakage rates at 10 and 20 mm Hg were calculated by backward extrapolation of graph. Q = 2 L/min, 0.1-mm hole ({triangleup}); Q = 4 L/min, 0.1-mm hole ({blacksquare}). Q = 2 L/min, measured leak, 0.1-mm hole ({blacktriangleup}); Q = 4 L/min, measured leak, 0.1-mm hole ({square}).

 

Figure 7
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  		Fig. 4 —Graph shows predicted extravasation rates obtained using mathematic model and actual observed extravasation rates from 280-µm hole plotted against increasing mean arterial pressure. Q = 2 L/min, 0.28-mm hole ({triangleup}); Q = 4 L/min, 0.28-mm hole ({blacksquare}). Q = 2 L/min, measured leak, 0.28-mm hole ({blacktriangleup}); Q = 4 L/min, measured leak, 0.28-mm hole ({square}).

 

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