Automatic Emphysema Detection using Weakly Labeled HRCT Lung Images

A method for automatically quantifying emphysema regions using High-Resolution Computed Tomography (HRCT) scans of patients with chronic obstructive pulmonary disease (COPD) that does not require manually annotated scans for training is presented. HRCT scans of controls and of COPD patients with diverse disease severity are acquired at two different centers. Textural features from co-occurrence matrices and Gaussian filter banks are used to characterize the lung parenchyma in the scans. Two robust versions of multiple instance learning (MIL) classifiers, miSVM and MILES, are investigated. The classifiers are trained with the weak labels extracted from the forced expiratory volume in one minute (FEV$_1$) and diffusing capacity of the lungs for carbon monoxide (DLCO). At test time, the classifiers output a patient label indicating overall COPD diagnosis and local labels indicating the presence of emphysema. The classifier performance is compared with manual annotations by two radiologists, a classical density based method, and pulmonary function tests (PFTs). The miSVM classifier performed better than MILES on both patient and emphysema classification. The classifier has a stronger correlation with PFT than the density based method, the percentage of emphysema in the intersection of annotations from both radiologists, and the percentage of emphysema annotated by one of the radiologists. The correlation between the classifier and the PFT is only outperformed by the second radiologist. The method is therefore promising for facilitating assessment of emphysema and reducing inter-observer variability.Comment: Accepted at PLoS ON

A New Fiducial Marker for Gated Radiotherapy in the Lung – A Feasibility Study of Bronchoscopy Based Insertion and Removal in Göttingen Mini-Pig

To develop a new prototype fiducial marker (LS-1) that may be used for gated radiotherapy in the lung.  One LS-1 marker was inserted in the lung of each animal under sedation. Animals were kept under observation  for four weeks after insertion. After the observation period the marker was removed. Animals were  CT scanned after insertion and before removal of the LS-1 marker. After the last CT scan animals were  euthanized and lungs excised for pathology. The LS-1 marker was successfully inserted in all fourteen animals. Thirteen of fourteen LS-1 marker’s  were in situ after four weeks. Two cases of pneumothorax were seen in connection with insertion. The LS-1  marker could only be successfully removed from eleven of thirteen animals. Damage to the lung was mainly  local close to the LS-1 marker insertion site. The LS-1 marker has the potential to be a fiducial marker suitable for gated external beam radiotherapy in  the lung. The method still needs some refinement prior to application in humans.