Utility of negative oral contrast (milk with 4% fat) in PET-CT studies

Samuel Aban Meyer, Sachin Gawde, Samuel Aban Meyer, Sachin Gawde

Abstract

Aims: The aim of this study was to evaluate whether low-attenuation oral contrast agent (milk with 4% fat) in PET-CT gastrointestinal studies(GIT) improves the diagnostic accuracy.

Justification for the study: Traditional high-contrast oral agents like iodine solutions, and barium suspensions which due to overcorrection problems in PET-CT interpretation lowers the accuracy of diagnosis. Traditional low-attenuation oral contrast agents are water, air, fat containing agents used with 12.5% corn oil and polyethylene glycol. Volumen is a 0.1% barium suspension and has found favor in visualization of mural features as well as for GIT distension. Milk with 4% fat content has also been tested out in radiological studies and found to be as effective as Volumen. As the former is more easily available, palatable, and acceptable especially, by children it needed to be tested in the visualization of the GIT in the PET-CT scenario.

Materials and methods: Total of 112 patients were divided into 3 groups. Group I: No intervention (18 subjects) Group II: Water (55 subjects): All these patients had 500-750 ml of water 5-10 min before PET examination. Group III: Milk (39 subjects) 500 ml of milk (4% fat content with no additives) was given 40-45 min after 18F-Fluorodeoxyglucose (FDG) injection and another 500 ml 5 min before scan was started. For patients intolerant to milk the same procedure was carried out with soya milk. Group IV comparison with data with Volumen.

Results: CRITERIA FOR EVALUATION OF GUT DISTENSION ON CT IMAGES: (0) No distension, (1) 1 cm distension, (2) 1-2 cm distension, (3) >2 cm distension. For the study analysis, % of patients with criteria 2 and 3 were considered as good visualization. Stomach distension was16%, 47%, 88%, 75% in Gr1-4 respectively, Duodenum-11%, 27% 88%, 86%, Jejunum-33%, 49%, 89%, 76%(*) Ileum-40%, 77%, 82%, 80%(*) and Colon-55%, 58%, 7 4%. Visualization of bowel wall with enhancement of stomach, duodenum, jejunum, and ileum and proximal colon was significantly better with milk than with water or no intervention. Intensity of FDG uptake was mild to moderate with no overcorrection in normal bowel loops and in patients with GIT lesions. Gaseous distension was not increased with milk as an oral contrast agent. Images of patients with bowel tumor was well-delineated with milk administration as the FDG uptake ratio of tumor to gut was high.

Conclusion: Distension and visualization of the stomach, duodenum, jejunum, and proximal bowel was significantly improved with milk as a low-attenuation contrast agent. Intensity of FDG uptake was not significantly increased in normal gut and delineation of tumor with increased FDG uptake was improved as overcorrection was minimal.

Keywords: Low attenuation gastrointestinal contrast; PET-CT of the gut; milk with 4% fat.

Conflict of interest statement

Conflict of Interest: None declared

Figures

Figure 1
Figure 1
The distension criteria of the segments of the gut (% of patients with criteria 2 and 3). (Stomach 16%, 47%, 88%, 75%* [No intervention-18 patients, water-55 patients, milk-39 patients, Volumen – 100 patients*], Duodenum 11%, 27% 88%, 86%*, Jejunum 33%, 49%, 89%, 76%*, Ileum 40%, 77%, 82%, 80%*, Colon 55%, 58%, 74%, Volumen values were compared from the reference *AJR 190:1307-1313, 2008)
Figure 2
Figure 2
The effect of contrast on the 18FFDG uptake on the gut and gaseous distension (% of patients showing intense intestinal uptake +++ or SUV >2.5 and 2.5 and

Figure 3

(a) Mesenteric metastasis, (b) stomach…

Figure 3

(a) Mesenteric metastasis, (b) stomach wall, (c) normal patient with positive oral contrast…

Figure 3
(a) Mesenteric metastasis, (b) stomach wall, (c) normal patient with positive oral contrast with over correction of normal. 18F FDG activity in the colon, (d) Colon mass with negative oral contrast (milk). Pelvic metastasis is also seen. Standard uptake values with negative contrast in the normal gut varies from 1.7 ± 0.5 while barium based. Oral contrast agents show SUVs of 2.5 ± 0.6
Figure 3
Figure 3
(a) Mesenteric metastasis, (b) stomach wall, (c) normal patient with positive oral contrast with over correction of normal. 18F FDG activity in the colon, (d) Colon mass with negative oral contrast (milk). Pelvic metastasis is also seen. Standard uptake values with negative contrast in the normal gut varies from 1.7 ± 0.5 while barium based. Oral contrast agents show SUVs of 2.5 ± 0.6

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