1. Ventilation perfusion functional difference images in lung SPECT: A linear and symmetrical scale as an alternative to the ventilation perfusion ratio.
- Author
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de Nijs, Robin, Berg, Ronan M.G., Lindskov Hansen, Sofie, and Mortensen, Jann
- Abstract
• V-Q difference shows classical and reversed mismatches simultaneously. • Saving the ratio with very large values is avoided by using the V-Q difference. • The scaled V-Q difference represents change in lung function. • No masking of artifacts is needed for the scaled V-Q difference images. • Functional difference images could improve the diagnostic value of VQ SPECT. Ventilation Perfusion SPECT is important in the diagnostics of e.g. pulmonary embolism and chronic obstructive pulmonary disease. Classical and reverse mismatched defects can be identified by utilizing the ventilation-perfusion ratio. Unfortunately, this ratio is only linear in the ventilation, the scale is not symmetrical regarding classical and reversed mismatches and small perfusion values give rise to artifacts. The ventilation-perfusion (VQ) difference is developed as an alternative. For both VQ-ratio and VQ-difference a scaling factor for the perfusion is computed, so that voxels with matched ventilation and perfusion (on average) yield zero signal. The relative VQ-difference is calculated by scaling with the summed VQ-signal in each voxel. The scaled VQ-difference is calculated by scaling with the global maximum of this sum. The relative and scaled differences have a scale from −1 (perfusion only) to + 1 (ventilation only). Image quality of relative VQ-difference and VQ-ratio images is hampered by artifacts from areas with both low perfusion and low ventilation. Ratio and differences have been investigated in ten patients and are shown for three patients (one without defects). Clinical thresholds for the difference images are derived resulting in color maps of relevant (reversed) mismatches with a (reciprocal) ratio larger than two. The relative ventilation-perfusion difference is a methodological improvement on the ventilation-perfusion ratio, because it has a symmetrical scale and is bound on a closed domain. A better diagnostic value is expected by utilizing the scaled difference, which represents functional difference instead of relative difference. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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