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P101. Radiation exposure during nasojejunal intubation for MRI

L. Puustinen1, K. Numminen2, J. Uusi-Simola2, T. Sipponen1

1Helsinki University Central Hospital, Department of Gastroenterology, Helsinki, Finland; 2Helsinki University Central Hospital, Department of Radiology, Helsinki, Finland

Background: Patients with Crohn's disease are often investigated using MRI enteroclysis which provides better visual quality than MRI enterography, but exposes patients to radiation.

Methods: During 12 months study period, all 95 patients (40 men) undergoing MRI enteroclysis with nasojejunal intubation using fluoroscopy for suspicion or evaluation of Crohn's disease were included. Average age at the time of MRI was 40.1 years (range 17–79).

Conversion factors from dose-area product to effective dose were determined with a Monte Carlo based software PCXMC. The Conversion factors were determined for a standard sized adult phantom for posterior-anterior and right-posterior-oblique projections.

Results: The average total time of fluoroscopy was 3 min 17 s (range 0 min 7 s – 31 min). The average effective dose of ionizing radiation was 0.21 mSv (range 0.01–2.67). The average dose is equivalent to ten PA chest x‑rays. Standard deviation was 0.41 mSv. The highest single patient received an effective dose of 2.67 mSv. In comparison, a standard abdominal ct scan causes an effective dose of 12 mSv.

Conclusions: The effective dose of ionizing radiation with nasojejunal intubation is relatively small in the majority of patients. The use of MRI enteroclysis seems to be justified when exploring patients with suspected or known Crohn's disease. When repeated imaging is necessary, it would be advisable to consider imaging techniques, which do not subject patients to ionizing radiation. Also if a previous nasojejunal intubation has been difficult, a different imaging technique is recommended.