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Brain SPECT Artifacts in Patients Having Metallic Cranioplasty

Michael T. Hackett, Wei-Jen Shih and Vickie H. Kiefer
Journal of Nuclear Medicine Technology December 2001, 29 (4) 189-192;

Article Figures & Data

Figures

  • FIGURE 1.
    FIGURE 1.

    Patient 1, with head trauma in the 1940s that required a metallic plate in the left frontal area. (A) Transaxial images from brain SPECT study show photon-deficient area in the left frontal region with faint increased tracer activity extending into scalp area at periphery. (B) CT shows significant streak artifact caused by the metallic plate.

  • FIGURE 2.
    FIGURE 2.

    Patient 2, with head trauma in the 1970s that required a metallic plate in the right occipital area. (A) Transaxial images from brain SPECT study show photon-deficient area in the right occipital region with prominent increased tracer activity extending into scalp area at periphery. (B) CT shows significant streak artifact caused by the metallic plate.

  • FIGURE 3.
    FIGURE 3.

    Patient 3, with head trauma in the 1940s that required a metallic plate in the left frontal area. (A) Transaxial images from brain SPECT study show photon-deficient area in the left frontal region with very faint increased tracer activity extending into scalp area at periphery. (B) CT shows significant streak artifact caused by the metallic plate.

  • FIGURE 4.
    FIGURE 4.

    Transaxial images of SPECT brain phantom with no metallic sheets in place (A) and with 0.076-cm lead sheet placed over midline of the frontal region (B). The 0.038-cm lead sheet produced a similar artifact, though not as prominent.

Tables

  • TABLE 1

    Summary of Metallic Plates/Sheets Used for Cranioplasty and Phantom Study

    Type of Metallic Plate/SheetAluminumStainless SteelTantalumLead
    Mass attenuation coefficient for 140 keV photon (cm2/g)0.143NA1.825 2.393
    Density (g/cm3)2.70NA16.6511.35 
    Reported metallic plate thickness used for cranioplasty (cm)0.0640.0460.038, 0.051NA
    Theoretical attenuation for reported metallic plate (%)2NA68, 79NA
    Experimental metallic sheet thickness used for phantom study (cm)0.0640.061NA0.038, 0.076
    Theoretical attenuation for experimental metallic sheet (%)2NANA64, 87
    Calculated attenuation from planar image (%)49NANA, 83

    • Mass attenuation coefficient and density information obtained from www.physics.NIST.gov Web site’s reference tables of x-ray mass attenuation coefficients.

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