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Deep lymphatic drainage plays an important role in the lung, as it removes foreign materials laying on the airways surface, such as pathogenic microorganisms. This drainage is also associated with lung tumour dissemination route. Liposomes with a specially tailored membrane were used as foreign particles to be removed by the lung lymphatics. We aim to obtain images of deep lung lymphatics in baboons using liposomes encapsulating (99m)Tc-HMPAO, as aerosols. Axillary lymph nodes were visualized 30 min post-inhalation, becoming more evident 1 hour after, when abdominal aortic and inguinal lymph nodes were also observed. Late images added no additional information. ROI's and their time-activity curves were drawn to obtain biokinetic information. In conclusion, we can say that the proposed technique enables visualization of the deep lymphatic lung network and lymph nodes. This methodology may be an important tool for targeted lung delivery of cytotoxic drugs., (Copyright © 2011. Published by Elsevier España.)

Unlabelled: Lymphatic drainage plays an important role in the uptake of particulates in the respiratory system, being also associated to the spreading of lung cancer through metastasis development. In recent years solid lipid nanoparticles (SLN) have been proposed as carriers of anti-tumoural drugs, for their low toxicity and surface characteristics make them suitable for either imaging (gamma-scintigraphy) or therapy upon encapsulation of cytotoxic drugs. Assessment of inhaled radiolabelled SLN biodistribution is described in the present work., Methods: Nanoparticles (200 nm) were radiolabelled with 99mTc using the lipophilic chelator D,L-hexamehylpropyleneamine oxime (HMPAO). Biodistribution studies were carried out following aerosolisation and administration of a 99mTc-HMPAO-SLN suspension to a group of adult male Wistar rats. A 60 min dynamic image acquisition was performed in a gamma-camera, followed by static image collection at 30 min intervals up to 4 h postinhalation. Radiation counting was performed in organ samples, collected after the animals were sacrificed., Results: The data show an important and significant uptake of the radiolabelled SLN into the lymphatics after inhalation, and a high rate of distribution in periaortic, axillar and inguinal lymph nodes., Conclusion: Results indicate that SLN could be effective colloidal carriers for lymphoscintigraphy or therapy upon pulmonary delivery.

The general aspects of methodology and image processing used in some of the nuclear pneumology techniques developed by our group are briefly described in this presentation. Three main subjects are considered: 1--Studies on pulmonary circulation, 2--Studies on pulmonary ventilation and perfusion and 3--Studies on alveolar-capillary barrier permeability. This is a multidisciplinary work that is the joint effort of three department: Biophysics Service (Faculty of Medicine, University of Coimbra), Department of Electronics and Telecommunications (University of Aveiro) and Pneumology Center (University of Coimbra).

We propose a functional parametric analysis method using ECG-gated 99mTc-labeled red blood cell (RBC) imaging for detection and characterization of periodic variations in local blood activity in the lungs during cardiac cycle. We validated in animal experiments that such count variations correlate with cyclical pulmonary blood flow and may be used for evaluation of systemic-to-pulmonary shunts. Clinical studies were performed in 48 patients. After labeling the RBC pool with 99mTc, ECG-gated gamma camera images of both lung fields were acquired and processed to obtain Fourier transforms of time/activity functions in selected regions. The first harmonic parametric images of amplitude and phase were derived. There was an excellent correlation (r = 0.92) between activity variations and pulsatile flow measured by our method with that obtained by the thermodilution method in dog experiments (n = 10) after implantation of a systemic-to-pulmonary shunt. Patient studies showed the technique to be sensitive in detecting and quantifying abnormal systemic-to-pulmonary blood flow. Lung pulsatile flow can thus be noninvasively measured from functional parametric phase and amplitude images; the technique may be useful for detecting and quantifying abnormal systemic-to-pulmonary blood flow in man.

A new method of ventilation and perfusion display onto a single image is presented. From the data on regions of interest of the lungs, three-dimensional histograms are created, containing as parameters X and Y for the position of the pixels, Z for the perfusion and colour for local ventilation. The perfusion value is supplied by sets of curves having Z proportional to the local perfusion count rate. Ventilation modulates colour. Four perspective views of the histogram are simultaneously displayed to allow visualization of the entire organ. Information about the normal ranges for both ventilation and perfusion is also provided in the histograms.

A method for the study of the dynamics of the perfusion of the compliant vascular tree of the lungs using in vivo labelled 99mTc red cells and ECG gating is presented. Following blood pool labelling, posterior, ECG gated gamma camera images were acquired in time intervals of about 40 ms for 1,000-2,000 cardiac cycles. The images show the lungs plus the heart and great vessels. The image sequence containing the periodic variation of the blood activity in the lungs during the cardiac cycle is analyzed to obtain volume curves and functional images of the amplitude and phase of the lung perfusion. The interference of the heart and great vessels with the left lung can be avoided by excluding the superimposed areas in the ROIs with the sacrifice of part of the left lung. This technique allows dynamic visualization of the perfusion process in the compliant arterial and venous vascular trees of the lungs. The results obtained with this method in normals and some pathologies are discussed.