Article Figures & Data
Figures
- FIGURE 1.
QC images for SPECT/CT registration in AC-MPI. (A) CT: Hounsfield units obtained from CT are converted to appropriate attenuation coefficient values. (B) Non–AC-MPI. (C) Fused SPECT/CT: MPI contours are shown in red. Software-enabled control and correction of emission–transmission registration before AC image reconstruction.
- FIGURE 2.
Artificial CT shift along 3 axes and 6 directions by 3 pixels with respect to SPECT (red contour). Directions were caudal, −z-axis (A), cephalad, +z-axis (B), ventral, −y-axis (C), dorsal, +y-axis (D), right, −x-axis (E), and left, +x-axis (F).
- FIGURE 3.
Percentage change in polar map segment score as function of misregistration of CT with respect to SPECT. For each axis, most severe changes are caused by 3-pixel shift as follows: anterior wall by a caudal shift (A), lateral wall by ventral shift (B), and lateral wall by right shift (C). All severe changes can be visually identified as misregistration, with myocardium on SPECT overlapping lung tissue on CT.
Tables
Direction of misregistration Magnitude of misregistration (pixels) >1 >2 >3 On any axis 181 (72.9%) 57 (22.9%) 10 (4.0%) Most severe direction on any axis* 152 (61.3%) 40 (16.1%) 7 (2.8%) ≥2 axes 65 (26.2%) 5 (2.0%) 0 Most severe direction* ≥2 axes 3 (1.2%) 0 0 ↵* In different experiment, caudal, ventral, or right artificial shift of CT was found to induce most severe changes in polar map scoring.
Number in parentheses is percentage of 248 consecutive clinical studies.
Magnitude of misregistration (pixels) Region Direction of misregistration Anterior Apex Inferior Septum Lateral Cephalad (+z-axis) 3 − − − − − 2 + − − − − 1 + − − − − Caudal (−z-axis) 1 − + + + + 2 − − + + + − 3 − − + + + − Dorsal (+y-axis) 3 − − − − − − + 2 − − − − − − + 1 − − − − + Ventral (−y-axis) 1 − + − + − 2 − + − + − − 3 − ++ − − + − − − Left (+x-axis) 3 − − − − − + 2 − − − − + 1 − − − − + Right (−x-axis) 1 + + + + − 2 + + + + − 3 − − + + + − − Difference with respect to registered SPECT/CT: + + + = positive change of ≥15%; − − − = negative change of ≤−15%; + + = positive change of <15% and ≥5%; − − = negative change of >−15% and ≤−5%; + = positive change of <5% and >0%; − = negative change of >−5% and <0%.
- TABLE 3
κ-Statistics and Significance of McNemar Differences of SSS for Each Artificial Misregistration
No. of patients changing category* Misregistration direction Misregistration magnitude (pixels) Abnormal to normal Normal to abnormal κ-value McNemar test Cephalad (+z-axis) 3 2 3 0.440 NS 2 4 1 0.510 NS 1 4 3 0.300 NS Caudal (–z-axis) 1 3 0 0.706 NS 2 3 3 0.394 NS 3 2 7 0.043 P < 0.05 Dorsal (+y-axis) 3 2 8 −0.075 P < 0.05 2 1 7 0.400 P < 0.05 1 3 4 0.286 NS Ventral (–y-axis) 1 4 1 0.510 NS 2 4 2 0.406 NS 3 2 3 0.490 NS Left (+x-axis) 3 3 4 0.286 NS 2 2 2 0.596 NS 1 3 1 0.604 NS Right (– x-axis) 1 3 2 0.500 NS 2 2 4 0.381 NS 3 1 7 0.140 P < 0.05 ↵* Registered case: 9 normal (SSS < 4), 11 abnormal (SSS ≥ 4).
NS = no significant difference (P > 0.05).
- TABLE 4
Directionality: Misregistrations with Significant Difference Between Positive and Negative 3-Pixel Shifts (by Student t test)
Misregistration direction Region Anterior Apex Inferior Septum Lateral Cephalad/caudal (z-axis) P < 0. 001 P < 0.001 P < 0.025 NS NS Dorsal/ventral (y-axis) NS P < 0.001 P < 0.002 P < 0.001 P < 0.001 Left/right (x-axis) NS NS P < 0.001 P < 0.001 P < 0.004 NS = no significant difference between positive and negative shifts (P > 0.05).
