Jeffrey Seth Klein MD, Abstract Co-Author: Nothing to Disclose

Daniel N. Sommers MD, Presenter: Nothing to Disclose

David Kaminsky MD, Abstract Co-Author: Nothing to Disclose

Jason Bates PhD, Abstract Co-Author: Nothing to Disclose

Michael J. Sullivan BS, Abstract Co-Author: Nothing to Disclose

Charles Irvin PhD, Abstract Co-Author: Nothing to Disclose

Quantitative image analysis using CT has been used to measure extent of airtrapping and emphysema in subjects with asthma and COPD. Studies have involved measuring the pixel distribution of lung attenuation from single slice scans of anywhere between 1.5 and 10 mm collimation. With the availability of high speed volumetric helical CT, regions of interest may be defined that span many single slice views included within the entire acquisition. In order to determine how lung attenuation is affected by varying slice thickness, we measured lung attenuation using a manual single slice vs. automated single slice vs. automated 3-10-slice volume averaging method in an ongoing study of quantitative imaging in asthmatic subjects before and after inhalation of methacholine while supine.

Fourteen subjects have been studied, 8 with asthma and 6 non-asthmatic healthy controls. All subjects were studied before and after inhalation of methacholine. Lung attenuation in the manual vs. automated single vs. automated volumetric methods before (pre) and after (post) methacholine were measured.

Lung attenuation (HU) in the manual vs. automated single vs. automated volumetric methods before (pre) and after (post) methacholine were measured. In asthmatics, manual pre =699±37, manual post=749±45, single pre=722±38, single post=766±52, volume pre= 722±36, volume post768±50. In control subjects, manual pre =716±98, manual post=758±60, single pre=770±97, single post=795±58, volume pre 772±92, volume post=796±58. When correlated by linear regression, the coefficient of determination was > 0.96 for all comparisons of the 3 methods in the pre- or post- conditions, with all p-values < 0.01.

We conclude that an automated method of measuring lung attenuation using single slices is as precise as that using volume averaging around the same region of interest, and also compares closely to a manual method. These data suggest that for purposes of measuring lung attenuation, precise matching of anatomic structures in lung images acquired before and after methacholine is not necessary as long as similar regions of interest are studied.

Klein, J, Sommers, D, Kaminsky, D, Bates, J, Sullivan, M, Irvin, C, Comparison of Lung Attenuation Changes in Asthmatic and Normal Patients: Single Slice versus Volumetric Assessment.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4404717.html