The usual flat rectilinear detector motion in radioisotope scanning is by no means the only one possible, and sometimes changing it is advantageous. In brain scanning, for instance, Reid and Johns (1) have used concentric parasagittal arcs to match the curvature of the head. We have previously suggested that a cylindrical scan path would be useful in scanning the curved surface of the liver (2) and, more recently, we have demonstrated that the detector motion could be modified to make body-section scanning possible (3, 4). This report describes the first clinical use of a scanning instrument which we have constructed to explore the potential of cylindrical and section scanning. Scanning System Mechanical Design: The scanning system includes two opposed scintillation detectors employing 3-in. diameter by 2-in. thick NaI (Tl) crystals, with a minimum of 2-in. of lead side wall shielding, and a choice of focusing collimators designed for different photon energies (5). The mountings permit the detectors to be raised, lowered, swiveled on gimbal supports on two axes, and then locked in the required position (Fig. 1). The scanner is an assembly of three units : a yoke, a rotation arm, and a pedestal mounted on tracks by flanged wheels. A cantilever platform supports the patient between the two opposed scintillation detectors mounted at the extremities of the scanner yoke. The three basic motions of the scanner, rotary, transverse, and longitudinal, are obtained by applying power to axles in both the rotation arm and yoke, and, independently, to the wheels. For detector rotation, power is applied only to the axle of the rotation arm (Fig. 2, A). For a “straight-line” detector motion transverse to the patient, the central axle turns the rotation arm, while synchronized counter-rotation is applied to the yoke axle to fix the angle of the detector with respect to the line of travel (Fig. 2, B). This transverse detector excursion is actually a shallow arc of 2 cm. rise for a 30 cm. chord length. The transverse scan line can be oriented at any angle about the patient by appropriate positioning of the rotation arm prior to the excursion. The entire scanner can be moved step-wise with the powered wheels through a maximum longitudinal distance of 125 cm. to provide line spacing (Fig.2, C). Motor Control: The rotation arm axle and a 3-phase synchrotie generator are powered by a 1 1/2 horsepower d.c. motor. A 3-phase synchrotic motor, synchronous in rotation and powered by the generator, drives the yoke axle. A separate 1/2-horsepower d.c. motor drives the rear wheels for longitudinal travel. A servo-mechanism is used to maintain speed regulation in spite of changes in loading as the detector positions change. The machine is programmed for operation by adjusting calibrated front-panel controls for the scanning geometry desired. These controls establish voltages to represent limits of movement.