A Technique for Simulating Radionuclide Images from the Aerosol Deposition Pattern in the Airway Tree

Influence of particle size on regional lung deposition – What evidence is there?

“…As opposed to planar sections (based on pixels), the lung structure can be divided into volumes of interest, also known as voxels. For instance, in one of these techniques, the airway tree is arbitrarily divided into lung layers in the shape of concentric "shells" with the main bronchial bifurcation as the reference point (Berridge et al, 2003;Fleming et al, 1997). Based on gamma camera counts, these shells are further converted into spatial distributions that can consequently be used in the definition of Penetration Index (PI = P/C or C/P ratio).…”

“…Though, due to insufficient time for growth coupled with effect of mass transfer, the increase in aerodynamic diameter by small hypertonic saline droplets was expected by the authors to reach an intermediate size between 3.2 and 6.5 m. Consequently, it would be expected to demonstrate a pulmonary deposition pattern intermediate to the smaller and bigger airways. Based on the work by Fleming et al (1997), the lung images from SPECT were likewise subdivided into concentric shells as previously explained and the regional deposition of the particles in the lungs was determined according to the penetration index (P/C ratio). However, only deposition in the right lung was considered, since the image of the left lung may include confounding factors from the stomach and cardiac shadow.…”

The Use of Combined Single Photon Emission Computed Tomography and X-ray Computed Tomography to Assess the Fate of Inhaled Aerosol

“…(7,8) This was created by defining a uniform 3D distribution of activity in a computer model of the airway tree and simulating the corresponding gamma camera image using the attenuation map derived from the CT scan to model the effect of tissue attenuation. (8) The other regions were defined manually from a visual display of the initial aerosol deposition image. Attenuation correction factors for each region were calculated from thickness measurements obtained automatically from the CT images.…”

Airway Identification Within Planar Gamma Camera Images Using Computer Models of Lung Morphology

“…Although 3-D techniques may provide finer resolution and can provide information on lung volume, planar gamma cameras are still considered practical and valuable tools for assessing total and regional deposition for therapeutic and diagnostic studies. The relative sensitivity of 2-D and 3-D imaging techniques in determining regional deposition can be compared by computing the penetration index of the distribution of activity in the lung (17,41). However, for 2-D imaging techniques, the penetration index will be a sensitive function of the actual distribution of airways in the C and P regions.…”