title: Optimisation of quantitative lung SPECT applied to mild COPD: a software phantom simulation study.
abstract: BACKGROUND
  The amount of inhomogeneities in a (99m)Tc Technegas single-photon emission computed tomography (SPECT) lung image, caused by reduced ventilation in lung regions affected by chronic obstructive pulmonary disease (COPD), is correlated to disease advancement. A quantitative analysis method, the CVT method, measuring these inhomogeneities was proposed in earlier work. To detect mild COPD, which is a difficult task, optimised parameter values are needed.
  
  
  METHODS
  In this work, the CVT method was optimised with respect to the parameter values of acquisition, reconstruction and analysis. The ordered subset expectation maximisation (OSEM) algorithm was used for reconstructing the lung SPECT images. As a first step towards clinical application of the CVT method in detecting mild COPD, this study was based on simulated SPECT images of an advanced anthropomorphic lung software phantom including respiratory and cardiac motion, where the mild COPD lung had an overall ventilation reduction of 5%.
  
  
  RESULTS
  The best separation between healthy and mild COPD lung images as determined using the CVT measure of ventilation inhomogeneity and 125 MBq (99m)Tc was obtained using a low-energy high-resolution collimator (LEHR) and a power 6 Butterworth post-filter with a cutoff frequency of 0.6 to 0.7 cm(-1). Sixty-four reconstruction updates and a small kernel size should be used when the whole lung is analysed, and for the reduced lung a greater number of updates and a larger kernel size are needed.
  
  
  CONCLUSIONS
  A LEHR collimator and 125 (99m)Tc MBq together with an optimal combination of cutoff frequency, number of updates and kernel size, gave the best result. Suboptimal selections of either cutoff frequency, number of updates and kernel size will reduce the imaging system's ability to detect mild COPD in the lung phantom.
authors: Medical Radiation Physics, Department of Medical and Health Sciences, Linköping University, Linköping, 581 83 Sweden ; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, 581 83 Sweden.
authors: Pernilla
authors: P
authors: Norberg
authors: Medical Radiation Physics, Department of Medical and Health Sciences, Linköping University, Linköping, 581 83 Sweden ; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, 581 83 Sweden ; Clinical Physiology, Department of Medical and Health Sciences, Linköping University, Linköping, 581 83 Sweden.
authors: Anna
authors: A
authors: Olsson
authors: Medical Radiation Physics, Department of Medical and Health Sciences, Linköping University, Linköping, 581 83 Sweden ; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, 581 83 Sweden.
authors: Gudrun
authors: G
authors: Alm Carlsson
authors: Medical Radiation Physics, Department of Medical and Health Sciences, Linköping University, Linköping, 581 83 Sweden ; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, 581 83 Sweden.
authors: Michael
authors: M
authors: Sandborg
authors: Department of Medical Physics, Karolinska University Hospital, Huddinge, Stockholm 141 86 Sweden.
authors: Agnetha
authors: A
authors: Gustafsson
keywords: Computer-assisted image analysis; Lung diseases; Quantitative evaluation; SPECT; Simulation; Technegas