Discordant findings between krypton-81m gas and Tc-99m labeled ultrafine aerosol lung ventilation SPECT in two patients with idiopathic pulmonary fibrosis

Low-Frequency Intrapulmonary Percussive Ventilation Increases Aerosol Penetration in a 2-Compartment Physical Model of Fibrotic Lung Disease

In patients with fibrotic pulmonary disease such as idiopathic pulmonary fibrosis (IPF), inhaled aerosols deposit mostly in the less affected region of the lungs, resulting in suboptimal pharmacokinetics of airway-delivered treatments. Refinement of aerosol delivery technique requires new models to simulate the major alterations of lung physiology associated with IPF, i.e., heterogeneously reduced lung compliance and increased airway caliber. A novel physical model of the respiratory system was constructed to simulate aerosol drug delivery in spontaneously breathing (negative pressure ventilation) IPF patients. The model comprises upper (Alberta ideal throat) and lower airway (plastic tubing) models and branches into two compartments (Michigan lung models) which differ in compliance and caliber of conducting airway. The model was able to reproduce the heterogeneous, compliance-dependent reduction in ventilation and aerosol penetration (using NaF as a model aerosol) seen in fibrotic lung regions in IPF. Of note, intrapulmonary percussive ventilation induced a 2-3-fold increase in aerosol penetration in the low-compliance/high airway caliber compartment of the model, demonstrating the responsiveness of the model to therapeutic intervention.

Development of an ex vivo preclinical respiratory model of idiopathic pulmonary fibrosis for aerosol regional studies

Idiopathic pulmonary fibrosis is a progressive disease with unsatisfactory systemic treatments. Aerosol drug delivery to the lungs is expected to be an interesting route of administration. However, due to the alterations of lung compliance caused by fibrosis, local delivery remains challenging. This work aimed to develop a practical, relevant and ethically less restricted ex vivo respiratory model of fibrotic lung for regional aerosol deposition studies. This model is composed of an Ear-Nose-Throat replica connected to a sealed enclosure containing an ex vivo porcine respiratory tract, which was modified to mimic the mechanical properties of fibrotic lung parenchyma - i.e. reduced compliance. Passive respiratory mechanics were measured. ^81mKr scintigraphies were used to assess the homogeneity of gas-ventilation, while regional aerosol deposition was assessed with ^99mTc-DTPA scintigraphies. We validated the procedure to induce modifications of lung parenchyma to obtain aimed variation of compliance. Compared to the healthy model, lung respiratory mechanics were modified to the same extent as IPF-suffering patients. ^81mKr gas-ventilation and ^99mTc-DTPA regional aerosol deposition showed results comparable to clinical studies, qualitatively. This ex vivo respiratory model could simulate lung fibrosis for aerosol regional deposition studies giving an interesting alternative to animal experiments, accelerating and facilitating preclinical studies before clinical trials.

Coregistered ventilation and perfusion SPECT using krypton-81m and Tc-99m-labeled macroaggregated albumin with multislice CT utility for prediction of postoperative lung function in non-small cell lung cancer patients

RATIONALE AND OBJECTIVE

Co-registered SPECT and CT imaging (SPECT-CT) has potential for more precise evaluation of regional pulmonary function and may be useful for prediction of postoperative lung function in non-small cell lung cancer (NSCLC) patients. The purpose of the present study was to prospectively assess the capability of co-registered SPECT-CT using krypton-81m (Kr-81m) and technetium-99m-labeled macroaggregated albumin (Tc-99m MAA) for prediction of postoperative lung function of NSCLC patients compared with SPECT and planar imaging.

MATERIALS AND METHODS

Sixty consecutive patients considered candidates for lung resection underwent 16-slice CT, ventilation and perfusion scintigraphy with SPECT examinations, and preoperative and postoperative measurement of FEV(1)%. In each subject, SPECT and CT data were automatically fused by using commercially available software. Each postoperative FEV(1)% value was predicted from uptakes of Kr-81m and Tc-99m MAA within total and resected lungs. Then, reproducibility coefficients and the limits of agreement between actual and each predicted postoperative lung function were statistically assessed.

RESULTS

Reproducibility coefficients of SPECT-CT (Kr-81m: 5.1%, Tc-99m MAA: 5.2%) were smaller than those of SPECT and planar image using Kr-81m (SPECT: 7.4%, planar image: 12.1%) and using Tc-99m MAA (SPECT: 7.2%, planar image: 11.8%). The limits of agreement for SPECT-CT (Kr-81m: 3.3 +/- 10.5%, Tc-99m MAA: 5.4 +/- 11.0%) were also smaller than that of SPECT and planar image and small enough for clinical purposes.

CONCLUSIONS

Co-registered SPECT-CT using Kr-81m and Tc-99m MAA was able to more reproducibly and accurately predict postoperative lung function compared with SPECT and planar imaging.

Position affects distribution of ventilation in the lungs of older people: an experimental study

QUESTION

What is the effect of sitting and side-lying on the distribution of ventilation during tidal breathing in healthy older people?

DESIGN

Randomised, within-participant, experimental study.

PARTICIPANTS

Ten healthy people more than 65 years old.

INTERVENTION

Tidal breathing during sitting and right side-lying.

OUTCOME MEASURES

Distribution of ventilation as a percentage of total counts using Technetium-99m Technegas lung ventilation imaging.

RESULTS

In sitting, the ratio of the distribution of ventilation to apical: middle: basal regions was 1: 3.5: 3.3 in the right lung, and 1: 2.9: 2.3 in the left lung. In right side-lying, 32% (95% CI 22 to 43) more ventilation was distributed to the right lung than to the left lung. The ratio of the distribution of ventilation to apical: middle: basal regions was 1: 2.8: 2.2 in the right lung, and 1: 2.4: 1.9 in the left lung.

CONCLUSIONS

In both sitting and right side-lying, ventilation was distributed more to the middle than to the basal region, which may be related to age-associated changes in the respiratory system.

Long-term follow-up of patients with high-risk congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Recent advances including prenatal diagnosis, high-frequency oscillatory ventilation, and nitric oxide inhalation therapy have gradually improved the survival of high-risk congenital diaphragmatic hernia. However, the factors affecting the long-term outcome of these patients have not been well established.

METHODS

Thirty-three children with ages 4.1 +/- 2.5 years underwent clinical examination including growth measurements, echocardiography, ventilation, and perfusion scintigraphy.

RESULTS

No late death was observed. Common complications were frequent respiratory tract infection (13 patients) and bowel obstruction (5 patients underwent surgery). Although frequent respiratory tract infection decreased with increasing age, patients with frequent respiratory tract infection had a decreased uptake of lung ventilation and perfusion scintigraphy on the affected side and had a decreased height for age and weight for height. No significant difference in lung ventilation and perfusion scintigraphy was observed between patients treated with and without extracorporeal membrane oxygenation, those requiring oxygen more than 1 month, and between those with and without prenatal diagnosis. Patients with a patch repair had decreased uptake on lung perfusion scintigraphy. Although frequent respiratory tract infection may be owing to hypoplasia of the ipsilateral lung, it may impair recovery of the hypoplastic lung.

CONCLUSION

These results indicate that monitoring for respiratory tract infection in addition to nutritional assessment should be required in the follow-up of patients with congenital diaphragmatic hernia at high risk.

Scintigraphic Assessment of the Regional Distribution and Kinetics of Pharmaceuticals

A lesser known use of imaging studies in drug development is to determine the patterns of deposition, biodistribution, and regional kinetics of drugs in the body. This kind of study is of most interest when the drug is intended for local action following topical administration by inhalation. Imaging provides a convenient noninvasive method for observing initial deposition patterns and their variations caused by variables of the drug’s formulation and delivery method. Though planar gamma imaging is the method that has most often been used, recent years have seen promising demonstrations of SPECT and PET imaging to provide three-dimensional and quantitative measurements of drug deposition. When the goal of a drug is direct local treatment of diseased tissue, delivery of that drug is an important therapeutic variable. Imaging studies allow the drug delivery to be measured and optimized before a drug formulation is committed to clinical trials.

Indirect labeling of macroaggregated albumin with indium-111 via diethylenetriaminepentaacetic acid

It is ideal to perform a simultaneous pulmonary perfusion and ventilation scan in cases of suspected pulmonary thromboembolism. Indium-111 (111In)-diethylenetriaminepentaacetic acid (DTPA)-macroaggregated albumin (MAA) was designed for this purpose. MAA was conjugated with DTPA at a molar ratio of 1:100 and incubated with 111In-chloride for 30 min at room temperature. DTPA-MAA could be labelled with 111In above a 96% labelling efficiency without MAA particle aggregates making their particles larger than desirable. The obtained 111In-DTPA-MAA was intravenously injected into normal mice and their biodistribution was studied at 15 and 180 min after injection. A gamma camera image was obtained 15 min after injection. 111In-DTPA-MAA was stable in vitro and in vivo, and gave high uptake of murine lung in the biodistribution study and clearly visualized murine lung in the scintigraph. Using 111In-DTPA-MAA as a pulmonary perfusion agent, a simultaneous pulmonary perfusion and ventilation scan with technetium-99m-ventilation agents is able to be performed using the dual-isotope technique. 111In-DTPA-MAA may be a potential pulmonary perfusion agent.