Evaluation of Low-Density Neutral Oral Contrast Material in PET/CT for Tumor Imaging: Results of a Randomized Clinical Trial
July 21st, 2009 Posted by: admin
OBJECTIVE. The objective of this study was to determine the impact
on image quality and risks in terms of artifacts and side effects of a
low-density barium-based suspension as oral contrast material for CT during
PET/CT examinations of an oncologic patient population.
SUBJECTS AND METHODS. Eighty-five patients (51 men and 34 women;
mean age, 53 years; age range, 21–87 years) were prospectively
randomized to receive either 0.1% barium sulfate oral suspension or no oral
contrast material during PET/CT. Patients in the oral contrast group were
given 1,350 mL over 60–75 minutes. The 18F-FDG PET component
of each examination was reviewed for the presence of artifacts by two nuclear
medicine physicians and was classified as adequate (no presence of artifactual
focal FDG uptake attributed to attenuation-correction errors) or inadequate
(focal uptake in attenuation-correction PET images with no corresponding
uptake in non-attenuation-corrected PET images). Two radiologists reviewed the
CT studies and scored the degree of bowel opacification using a 5-point scale,
ranging from 0 for no opacification (i.e., not possible to delineate the bowel
structures from the surrounding tissues) to 4 for excellent opacification
(i.e., bowel structure identifiable and bowel wall clearly visible). The
attenuation values (in Hounsfield units) were recorded in the stomach,
duodenum, mid jejunum, and terminal ileum for quantitative analysis.
Interobserver variability was assessed using kappa coefficients.
RESULTS. None of the patients who received oral contrast material
experienced side effects. All 85 PET examinations were considered adequate
with no observable artifacts. The mean bowel opacification scores of the oral
contrast group (2.59 and 2.93) as evaluated by radiologists 1 and 2,
respectively, were significantly higher (p < 0.01) than those of
the control group (1.55 and 1.59). The level of attenuation achieved in the
contrast group was significantly higher than in the control group. The
interobserver variability was moderate ( = 0.32).
CONCLUSION. The use of low-density neutral oral contrast material
for CT during combined FDG PET/CT studies significantly improves visualization
of the bowel structures compared with no contrast material without causing
side effects or clinically detectable errors in the attenuation correction of
the FDG PET study.
