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Easy Method of Patient Positioning for Convergent-Beam Cardiac SPECT

Gengsheng L. Zeng and Paul E. Christian
Journal of Nuclear Medicine Technology September 2007, 35 (3) 131-134; DOI: https://doi.org/10.2967/jnmt.107.041160

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Figures

  • FIGURE 1. 
    FIGURE 1. 

    When parallel-hole collimators are used to image heart, detector area is not efficiently used, especially when detector area is large.

  • FIGURE 2. 
    FIGURE 2. 

    Convergent-beam collimators can magnify image size on detector or generate multiple images of object on detector, so that large detector area is more efficiently used for imaging of small organs. (Left) Fanbeam collimator. (Middle) Combined parallel-hole and slant-hole collimator. (Right) Collimator with varying focal length.

  • FIGURE 3. 
    FIGURE 3. 

    Patient-positioning procedure. (A) Default patient table position, in which table is centered. (B) Suggested left locking position of patient table. Top-view camera is used to monitor whether heart is centered. (C) Adjustment of table height so that heart is at center of side-view camera.

  • FIGURE 4. 
    FIGURE 4. 

    In modern SPECT systems, detector head can rotate and move radially and tangentially.

  • FIGURE 5. 
    FIGURE 5. 

    In modern SPECT systems, detector head can translate at each view, so that central ray passes through center of heart.

  • FIGURE 6. 
    FIGURE 6. 

    Coordinate system for fanbeam imaging geometry. During patient setup, center of heart on detector is marked as tθ and stored in computer. Two angles of θ are required to determine center of heart.

  • FIGURE 7. 
    FIGURE 7. 

    (A) Worst-case situation, at which truncation of heart is most likely to happen. (B) For patients weighing more than 135 kg, short scan can be used to avoid worst-case situation.

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