Differentiation of Anal Sphincters with High-Resolution Magnetic Resonance Imaging Using Contrast-Enhanced Fast Low-Angle Shot 3-Dimensional Sequences

Oliver Schaefer, Mehmet Oezer Oeksuez, Christian Lohrmann, Mathias Langer

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Objective: The imaging of the anal apparatus is becoming more and more important in the management of patients who suffer from anorectal disease. The exact differentiation of the sphincter muscles is a major requirement for the detection of disorders of the anal canal. The purpose of this study was to evaluate a new magnetic resonance (MR) imaging protocol using contrast-enhanced, high-resolution, fast low-angle shot, 3-dimensional (3D) sequences and image subtraction regarding the visualization and differentiation of the internal and external sphincter muscles. Methods: High-resolution pelvic MR imaging (1.5 T) was performed in 85 patients (42 male, 43 female; age range: 12-81 years) with a phased-array body coil. For an anatomic overview of the pelvic region, a short tau inversion recovery sequence in the coronal plane was carried out, followed by a 3D, high-resolution, fat-saturated, T1-weighted, gradient echo sequence before and after intravenous administration of a contrast agent (gadobenic acid, 0.15 mmol/kg). To optimize the visualization of the sphincter muscles, subtraction of the unenhanced from the contrast-enhanced sequences was routinely performed. The signal intensities of the internal and external sphincter muscles were measured in the axial plane on the subtracted images. Results: The distribution of the mean signal intensities of the internal and external sphincter muscles as well as the difference between both revealed a normal deviation. The confidence interval on a 95% significance level ranged between 1.6941 and 1.9393, with a mean of 1.81. In the whole study group, the signal intensity of the internal sphincter muscle was significantly higher than that of the external sphincter, thus facilitating the identification and differentiation of the 2 components of the anal sphincter complex. Conclusion: The presented MR imaging protocol is robust, provides a high image quality, and is well accepted by patients because of its noninvasiveness.

Original languageEnglish
Pages (from-to)174-179
Number of pages6
JournalJournal of Computer Assisted Tomography
Volume28
Issue number2
DOIs
StatePublished - 2004
Externally publishedYes

Keywords

  • Anal sphincter muscle
  • Magnetic resonance imaging

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