Comparison of three dimensional magnetic resonance imaging in conjunction with a blood pool contrast agent and nuclear scintigraphy for the detection of experimentally induced gastrointestinal bleeding

Abstract

Background and aims: To compare the performance of 3D magnetic resonance imaging (MRI) in conjunction with an intravascular contrast agent with that of scintigraphy, with respect to detection and localisation of gastrointestinal haemorrhage in vivo in pigs.

Methods: Intraluminal bleeding sites were surgically created in the small bowel and colon of six pigs. The animals underwent scintigraphy with (99m)Tc labelled red blood cells and 3D MRI following administration of an intravascular contrast agent (NC100150) at five minute intervals over 30 minutes. For analysis, the intestinal tract was divided into six segments. Based on the two evaluated methods, each segment was characterised on a five point scale regarding the presence of a bleed. At autopsy, the surgically manipulated bowel segments were inspected for the presence of haemorrhage.

Results: Bleeding was confirmed at autopsy in 18/36 segments. Contrast extravasation with subsequent movement through the bowel could be documented on MRI data sets. All segments were correctly characterised, resulting in 100% sensitivity and specificity for MRI. Based on scintigraphy, interpretation of seven segments (19%) was false (sensitivity/specificity of 78%/72%). Differences in diagnostic performance were evident in the receiver operator characteristic (ROC) analysis, with an area under the MRI curve of 0.99 and under the scintigraphy curve of 0.85.

Conclusion: In conjunction with an intravascular contrast agent, 3D MRI permits accurate detection and localisation of gastrointestinal bleeding. The extent and evolution of intestinal bleeding can be determined with repeated data acquisition.

Figure 1

Surgically created bleeding site in the caecum. To induce haemorrhage, the mucosa is scraped (arrow). Subsequently, the bowel is closed with a sealed suture.

Figure 2

The presence of the intravascular agent causes enhancement of the entire vascular system as shown on this coronal maximum intensity projection image: aorta (arrow), inferior vena cava (double arrow), portal vein (double arrowhead), splenic and mesenteric vessels (arrowheads). A small bleed is visualised in the right upper quadrant, corresponding to the duodenum (large arrow).

Figure 3

(A) Coronal source image of 3D gradient recalled echo data set collected 10 minutes after administration of the intravascular agent. Blood containing intravascular contrast is already evident in the duodenum (arrow). Note the excellent depiction of the mesenteric vascularity reflecting the presence of the intravascular contrast material. (B) The bleed is seen to even better advantage following subtraction of the first image set, depicting the mesenteric arteries and veins.

Figure 4

Coronal maximum intensity projection images of 3D gradient recalled echo data sets after subtraction of the first image set collected 10 minutes (A), 15 minutes (B), and 20 minutes (C) after administration of the intravascular agent. Increasing contrast accumulation within the small bowel (white large arrow), the caecum (white arrowhead), and the rectum (white small arrow) is evident. Planar scintigraphic images obtained at the same time intervals, 10 minutes (D), 15 minutes (E), and 20 minutes (F) after administration of tagged red blood cells show bleeds in the proximal small bowel (black large arrow) and the caecum (black arrowhead). The rectal bleed (black small arrow) was missed prospectively.

Figure 5

Receiver operator characteristic curves for magnetic resonance imaging (MRI) and scintigraphy (NUK).

Figure 6

Coronal maximum intensity projection images acquired 10 minutes (A) and 20 minutes (B) after administration of the intravascular agent. Increasing contrast accumulation within the proximal small bowel (large arrow) and the caecum (arrowhead) is evident. Corresponding axial magnetic resonance (MR) and single photon emission computed tomography (SPECT) scintigraphic images show the bleeding sites: (C,D) at the level of the kidneys (small arrows), and (E,F) below. Localisation of increased activity on the SPECT images corresponds well with the axial MR images.