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A multi-purpose ruler for magnetic resonance imaging

¹ University Department of Radiology, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK ² Herchel Smith Laboratory for Medicinal Chemistry, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK

This excerpt was created in the absence of an abstract.

Since the advent of clinical magnetic resonance imaging (MRI) there have been problems in locating internal structures with respect to external markers. Numerous methods have been advocated ranging from simple adhesive attachment of gels (Douglas & Gatenby, 1988; Matthaei et al, 1992) or "liver oil" capsules (Thompson, 1988) to more sophisticated MR compatible stereotactic devices (Saunders et al, 1990; Alvarez-Royo et al, 1991; Rousseau et al, 1991). In this report we describe a simple and versatile ruler for use with clinical MRI systems. The ruler was originally designed to facilitate direct anatomical-MRI correlative studies by allowing precise positioning of MR image slices with respect to an external reference. However, the design described can be readily adapted to the specific needs of the user in terms of both imaging characteristics and overall dimensions.

The ruler consists of four basic components (Figure 1): the outer casing, the end caps, a number of internal spacers and a number of internal tubes containing a gadolinium doped agarose gel. The precise dimensions of the ruler can be varied according to individual aims and the availability of standard sizes of materials. In the ruler illustrated in this report, the outer casing used was a 13.5 cm length of 13 mm square bar with a 6 mm diameter hole bored through the centre. The two end caps were carefully machined down to the exact diameter of the bore from a large diameter round bar.

Received for publication October 23, 1992. Accepted for publication January 11, 1993.