TY - JOUR

T1 - Ventilation perfusion functional difference images in lung SPECT

T2 - A linear and symmetrical scale as an alternative to the ventilation perfusion ratio

AU - de Nijs, Robin

AU - Berg, Ronan M.G.

AU - Lindskov Hansen, Sofie

AU - Mortensen, Jann

N1 - Publisher Copyright: © 2024 Associazione Italiana di Fisica Medica e Sanitaria

PY - 2024

Y1 - 2024

N2 - Purpose: 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. Methods: 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. Results: 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. Conclusions: 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.

AB - Purpose: 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. Methods: 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. Results: 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. Conclusions: 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.

KW - Difference

KW - Embolism

KW - Functional

KW - Krypton

KW - MAA

KW - Obstructive

KW - Perfusion

KW - Ratio

KW - SPECT

KW - Ventilation

UR - http://www.scopus.com/inward/record.url?scp=85184773558&partnerID=8YFLogxK

U2 - 10.1016/j.ejmp.2024.103306

DO - 10.1016/j.ejmp.2024.103306

M3 - Journal article

C2 - 38335743

AN - SCOPUS:85184773558

VL - 119

JO - Physica Medica

JF - Physica Medica

SN - 1120-1797

M1 - 103306

ER -