Non-invasive dye dilution method for measuring an atrial septal defect shunt size

AimsObjective of this study was to evaluate the feasibility of the non-invasive dye dilution method to quantify shunt size related to atrial septal defects (ASD).The diagnostic accuracy of shunt size determination in ASD’s has been suboptimal with common non-invasive methods. We have previously developed a cost-effective and time-effective non-invasive dye dilution method. In this method, the indocyanine green solution is injected into the antecubital vein and the appearance of the dye is detected with an earpiece densitometer.Methods and resultsWe studied 192 patients with an ASD. Mean pulmonary blood flow/systemic blood flow (Qp/Qs) was measured with dye dilution technique and compared with following methods: Fick’s invasive oximetry (n=49), transoesophageal echocardiography (TEE) measuring ASD size (n=143) and cardiac MR (CMR) (n=9).For the first 49 patients, Qp/Qs was 2.05±0.70 with the Fick’s invasive oximetry and 2.12±0.68 with dye dilution method with an excellent correlation between the two methods (R=0.902, p<0.001). In the second study sample, the ASD size by TEE was 15±6 mm on average, and the mean Qp/Qs 2.16±0.65 measured with dye dilution method with a good correlation between the methods (R=0.674, p<0.001). Qp/Qs measured with CMR was 1.87±0.40 resulting in a good correlation with the dye dilution method (R=0.696, p=0.037).ConclusionThe dye dilution method with earpiece densitometer recording is a clinically feasible and reliable method to assess shunt size in ASDs.

Biometric Image Analysis for Quantitation of Dividing Platelets

(1) Background: Quantification of platelet division is challenging because automated Coulter cell counters produce equivocal platelet counts. (2) Methods: We applied the flow cytometric cell tracking dye dilution assay as a popular immunological method to evaluate lymphocyte proliferation to prove and quantitate platelet division. We also devised a method relying on platelet culture in a semisolid medium which enabled dividing platelets to be identified by limiting the diffusive movement of platelets. Mixing platelets of different labeling colors in semisolid medium and counting the platelet doublets of each color combination enabled us to prove and quantitate platelet division. (3) Results: The tracking dye dilution assay revealed that 75.5 to 85.6% of platelets were dividing after 20 hours in culture. Platelets labeled with two different tracking dyes were mixed and cultured in semisolid medium for differential doublet counting. We counted platelet singlets and doublets of each color and color combination using confocal microscopy after six hours of culture and compared the relative number of two-colored doublets with binomial prediction to prove platelet division (P < 0.01). Division was suppressed by taxol, nocodazole, or cytochalasin D treatment. We derived a formula for determining the fraction of dividing platelets using the numbers of singlets and doublets of each color and color combination. The platelet division fraction ranged from 8.8 to 17.5%. (4) Conclusion: We successfully measured platelet division using a simple biometric image analysis method with possible future application to microfluidic devices.