First-pass scintigraphy with 99mTc macroaggregated albumin: a method for evaluating pulmonary arterial flow pulsatility

Evaluation of pulmonary hypertension and surgical outcome by dynamic pulmonary perfusion imaging in patients with valvular disease

PURPOSE

The gold standard for assessing the degree of pulmonary hypertension is by right ventricular catheterization, an invasive procedure. This study was carried out to evaluate a noninvasive method using dynamic pulmonary perfusion imaging (DPPI) for assessing pulmonary hypertension and surgical outcome in patients with valvular heart disease.

METHODS

A total of 116 patients (50 men, 66 women, mean age: 45.8 ± 10.7 years) with valvular disease and 10 healthy volunteers (4 men, 6 women; mean age: 40.2 ± 12.8 years) were included in this study. Baseline DPPI with Tc-99m macroaggregated albumin and right ventricular catheterization were performed in all patients, before mitral valve replacement with or without aortic valve replacement surgery, and healthy volunteers. At 7 to 14 days postsurgery, 105 patients were re-evaluated with DPPI. A total lung region of interest was used to calculate a time-activity curve from the DPPI. The lung equilibrium time (LET: time from Tc-99m macroaggregated albumin entering the lungs to equilibrium) was measured. Receiver operating characteristic analysis of LET for diagnosing pulmonary hypertension was carried out.

RESULTS

LET in patients with valvular heart disease was significantly prolonged compared with those in 10 healthy volunteers (P < 0.001). LET was 14.79 ± 4.37 seconds and 27.78 ± 10.26 seconds in 10 healthy volunteers and patients, respectively). A strong correlation between LET and mean pulmonary arterial pressure (r = 0.827, P < 0.001) was found. Using mean pulmonary arterial pressure as a gold standard and threshold value of LET at 22.7 seconds, the sensitivity and specificity of LET for assessing pulmonary hypertension were found to be 94.7% and 78.0%, respectively. The pre- and postsurgery LET were found to be significantly different (27.48 ± 9.83 seconds vs. 21.33 ± 6.18 seconds, P < 0.001).

CONCLUSION

DPPI is an accurate and noninvasive method for evaluating pulmonary hypertension and surgical outcome in patients with valvular heart disease.

Influence of Pulmonary Regurgitation Inequality on Differential Perfusion of the Lungs in Tetralogy of Fallot After Repair

OBJECTIVES

The purpose of this study was to evaluate the influence of pulmonary regurgitation inequality on differential perfusion of the lungs in tetralogy of Fallot (TOF) after repair.

BACKGROUND

Asymmetry of lung perfusion is one of the best predictors of outcome in TOF after repair. A recent phase-contrast magnetic resonance imaging (PC-MRI) study found prominent regurgitation inequality between the bilateral pulmonary arteries in TOF after repair.

METHODS

Forty-three TOF post-repair patients (median age = 51 months, 31 men) received PC-MRI and 99mTc-labeled macroaggregates of albumin perfusion scintigraphy (PS) in the same day. We took PC-MRI measurements of forward flow volume (FFV), backward flow volume (BFV), and net flow volume (NFV) (NFV = FFV - BFV) and regurgitation fraction (RF) (RF = BFV/FFV) at the left and right pulmonary arteries (LPA and RPA). The differential perfusion of the left lung (L%) (L% = left lung/left + right lung) as calculated by NFV ratio, by FFV ratio of PC-MRI, and by PS were compared.

RESULTS

The discrepancy between L% by NFV versus L% by PS was affected by the severity of RF of LPA (r = -0.51, p = 0.001); agreement between L% by NFV versus L% by PS was good (intraclass correlation coefficient [Ri] = 0.87) if RF of LPA <0.4 (n = 23) but downgraded (Ri = 0.51) and underestimated the L% (median of error = -14%, range = -25.3% to 5.5%) if RF of LPA > or =0.4 (n = 20). In contrast, agreement between L% by FFV versus L% by PS was high and unaffected by RF of LPA (Ri = 0.94, 0.92, respectively).

CONCLUSIONS

While integrating PC-MRI of pulmonary artery as a comprehensive MRI evaluation of TOF after repair, conventional NFV ratio method tended to underestimate the left lung perfusion and may lead to unnecessary intervention. The FFV ratio method should be used for precise assessment of differential lung perfusion.

Biological and Optical Properties of Fluorescent Nanoparticles Developed for Intravascular Imaging

Intravascular tracers in the blood circulation can provide a description of the flow field over time and space. To address the limitations of existing intravascular tracers, we have developed fluorescent nanoparticles capable of providing detailed information regarding the intravascular flow field. The nanoparticles were designed to maximize plasma half-life as well as minimize interactions with other blood components. The bioavailability of the particles in the blood circulation required nanoscale size and low surface charge density. Intravital imaging of nanoparticles in the microcirculation demonstrated that the fluorescence intensity of the nanoparticles was a major determinant of both temporal and spatial resolution of the flow field. We conclude that nanoparticles prepared with these physical and optical properties can provide an accurate description of the localized intravascular flow field.