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Purpose: To evaluate whether MR scanners with acoustic noise reduction and a short magnetic bore reduce the rate of claustrophobic reactions.
Materials and Methods: We performed a cohort study in an outpatient setting, enrolling a total of 55,734 consecutive patients referred for MRI of any part of the body based on a clinical indication. Imaging was performed using a conventional MR scanner (42,998 patients) and a recently developed MR scanner (12,736 patients) with 97% acoustic noise reduction and a short bore. Multiple logistic regression analysis was used to adjust for the nonrandomized design.
Results: In addition to those undergoing head-first examinations, female and middle-aged patients were significantly more likely to develop claustrophobia in the logistic regression analysis (P < 0.001). The rate of claustrophobic reactions was significantly lower with the recent MR scanner (0.7%; 95% confidence interval [CI]: 0.6–0.9%) than with the conventional scanner (2.1%; 95% CI, 2.0–2.3%; P < 0.001) with an adjusted odds ratio (OR) of 3.1 (95% CI, 2.5–3.9) and a number needed to treat of 72 (95% CI, 63–85).
Conclusion: The incidence of claustrophobia may be reduced by a factor of 3 when recently-developed MR scanners are used.
Key Words: magnetic resonance imaging; claustrophobia; safety; patients; anxiety; sedation
J. Magn. Reson. Imaging 2007;
26:1322–1327. © 2007 Wiley-Liss, Inc.
MAGNETIC RESONANCE IMAGING (MRI) has been described as the most important medical innovation in the last 25 years (1). Between 1% and 15% of all patients
1 Department of Radiology, Charite´, Medical School, Humboldt-Universität zu Berlin, Berlin, Germany.
2 Department of Medical Biometry, Charite´, Medical School, Humboldt-Universität zu Berlin, Berlin, Germany.
3 Radiology Outpatient Center Löbau, Löbau, Saxony, Germany.
* Address reprint requests to: M.D., Institut für Radiologie, Charite´–
Universitätsmedizin Berlin, Freie Universität und Humboldt-Universität zu Berlin, Charite´platz 1, 10117 Berlin, Germany.
E-mail: marc.dewey@charite.de
Results were presented in part as an abstract at the RSNA 2007 meeting
(no. 22-09SSC).
Received May 22, 2007; Accepted July 31, 2007.
DOI 10.1002/jmri.21147
Published online in Wiley InterScience ( www.interscience.wiley.com). |
patients who undergo an MR examination suffer from claustrophobia and cannot be imaged, or they require sedation to complete the scan (mean, 2.3%; 95% confidence interval [CI], 2.0–2.5%; Table 1) (2–12). Claustrophobic patients are frightened and experience a feeling of confinement or being closed in (13,14). In these patients anxiolytic sedation and additional sequences (after sedation) may be necessary to complete the examinations. This situation reduces workflow, limits patient acceptance, and wastes valuable scanning time. Improved convenience during the MR examination (e.g., reduction of noise and sensations of confinement) appears to be essential to avoid claustrophobic reactions (6,15). Thus, we have performed an observational cohort study to evaluate whether a newly-designed MR scanner with acoustic noise reduction and a patientfriendly short magnetic bore reduces the rate of claustrophobic reactions.
MATERIALS AND METHODS
Study Design
We performed a cohort study in an outpatient setting, enrolling a total of 55,734 consecutive patients referred for MRI over a period of over eight years. Between 28 April 2004 and 23 December 2005 we analyzed claustrophobia in 12,736 consecutive patients undergoing imaging in an outpatient imaging center (http://www. radiologie-sachsen.com) on a 1.5T MR scanner (Magnetom Avanto; Siemens Medical Solutions, Erlangen, Germany) with 97% acoustic noise reduction (below 99 dB A) and a short (1.6 m) and wide conical-shaped magnetic bore (0.6 m) that resembles the appearance of the gantry of a computed tomography scanner (Fig. 1). The results obtained in this patient group were compared with those achieved in a consecutive cohort (42,998 patients) examined on a conventional 1.0T MR scanner (Magnetom Impact Expert Plus; Siemens) in the same center between 3 November 1997 and 3 April 2004. This conventional MR scanner had a flat front and a bore with a length of 2.25 m and a width of 0.6 by 0.53 m (Fig. 1) with an acoustic noise of up to 128 dB A. All other parameters (e.g., receptionists with whom patients interact, dressing rooms, waiting rooms, etc.) were kept constant during the entire study period. Hearing protection was used in all patients as required by federal law. The study was approved by the State |
