OtherBASIC SCIENCE INVESTIGATIONS

Cine CT for Attenuation Correction in Cardiac PET/CT

Adam M. Alessio, Steve Kohlmyer, Kelley Branch, Grace Chen, James Caldwell and Paul Kinahan
Journal of Nuclear Medicine May 2007, 48 (5) 794-801; DOI: https://doi.org/10.2967/jnumed.106.035717

Article Figures & Data

Figures

  • FIGURE 1. 
    FIGURE 1. 

    Cardiac PET/CT example of attenuation and emission scan mismatch, which often occurs along lateral free wall or right diaphragm. Axial and coronal images of CT scan and of attenuation-corrected NH3 PET scan show, as indicated with same solid line drawn on all slices, 24.7-mm mismatch at lateral wall.

  • FIGURE 2. 
    FIGURE 2. 

    Transaxial slice through CT scans of oscillating box and water-filled sphere. (A) Image acquired in conventional helical mode (0.8-s rotation, 2.5-mm slice, pitch of 1). (B and C) Images formed from cine CT images: average image of 5 time frames at same slice (B) and intensity-maximum image of 5 time frames (C). Because PET is performed during multiple complete respirations, attenuation correction derived from cine CT images may be more accurate than that derived from helical images.

  • FIGURE 3. 
    FIGURE 3. 

    Comparison of attenuation correction techniques for cardiac PET, with CT images for attenuation correction at top and attenuation-corrected PET images at bottom. (A) PET/CT data acquired from stationary phantom processed to induce motion and generate the true case. (B–D) PET data acquired from moving phantom corrected with helical CT, as performed in current clinical practice (B); with average cine CT (C); and with intensity-maximum cine CT (D). The proposed cine methods reduce bias and variance in myocardium.

  • FIGURE 4. 
    FIGURE 4. 

    Coronal slice through patient example of aligned CT and PET images. At top are average (A) and intensity maximum (B) of 1 set of cine CT data. Top row was used for attenuation correction of PET images in bottom row.

  • FIGURE 5. 
    FIGURE 5. 

    Patient example of unacceptable alignment from average of cine CT images (column A) and acceptable alignment from intensity maximum of cine CT images (column B). Top row contains coronal slice of CT used for attenuation correction of PET image seen in second row from top. Third row from top contains transaxial slice of same CT image used for attenuation correction of PET image seen in bottom row. Identical myocardial outline is drawn on all coronal views, and separate identical outline is drawn on all transaxial views.

  • FIGURE 6. 
    FIGURE 6. 

    Average quantification in myocardium along circumferential profiles through short-axis view of basal segments (A and C) and mid segments (B and D) for identical emission data attenuation-corrected with different methods: plots of average kBq/mL in segments (A and B) and plots of same segments with units normalized (norm) such that images from all methods have same maximum value (C and D). This patient scan was classified as normal, with unacceptable alignment for average of first cine and with acceptable alignment for all other methods.

  • FIGURE 7. 
    FIGURE 7. 

    Coronal slices through average of cine CT data (A), intensity-maximum image (B), and weighted combination of average and intensity-maximum image (C). Weighted-combination image reduces some of the stair-step axial-field-of-view artifacts present on average image and shows a potentially more accurate boundary extent than does intensity-maximum image.

Tables

  • TABLE 1

    Protocol for Ammonia Cardiac Perfusion Study with Cine CT

    StepsTimeNotes
    Prepare patient (14)
    Acquire scout scan<1 min
    Rest study
     Perform first resting cine CT attenuation correction<1 min
     Administer NH3 (370–740 MBq)
     Acquire resting dynamic PET study4 minFor myocardial blood flow quantitation
     Acquire resting cardiac gated PET study15 minFor qualitative perfusion assessment
     Perform second resting cine CT attenuation correction<1 min
     Wait for isotope decay∼20 min40 min between injections
    Stress study
     Administer dipyridamole4 min0.56 mg/kg over 4 min
     Perform first stress cine CT attenuation correction<1 min
     Administer NH3 (555–925 MBq)
     Acquire stress dynamic PET study4 minFor myocardial blood flow quantitation
     Acquire stress cardiac gated PET study15 minFor qualitative perfusion assessment
     Perform second stress cine CT attenuation correction<1 min
    Total acquisition time∼80 min
  • TABLE 2

    Number of Unacceptable Attenuation–Emission Alignments for Rest, Stress, and Sum of Rest and Stress Cine CT

    Cine CT combinationRest (n = 20)Stress (n = 17)Total (n = 37)
    Average5;3;45;5;410;8;8
    Intensity maximum1;2;32;4;12;6;4

    • Data are for reviewer 1;reviewer 2;reviewer 3.

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