Dynamic ventilation imaging from four-dimensional computed tomography

Abstract

A novel method for dynamic ventilation imaging of the full respiratory cycle from four-dimensional computed tomography (4D CT) acquired without added contrast is presented. Three cases with 4D CT images obtained with respiratory gated acquisition for radiotherapy treatment planning were selected. Each of the 4D CT data sets was acquired during resting tidal breathing. A deformable image registration algorithm mapped each (voxel) corresponding tissue element across the 4D CT data set. From local average CT values, the change in fraction of air per voxel (i.e. local ventilation) was calculated. A 4D ventilation image set was calculated using pairs formed with the maximum expiration image volume, first the exhalation then the inhalation phases representing a complete breath cycle. A preliminary validation using manually determined lung volumes was performed. The calculated total ventilation was compared to the change in contoured lung volumes between the CT pairs (measured volume). A linear regression resulted in a slope of 1.01 and a correlation coefficient of 0.984 for the ventilation images. The spatial distribution of ventilation was found to be case specific and a 30% difference in mass-specific ventilation between the lower and upper lung halves was found. These images may be useful in radiotherapy planning.

CT ventilation functional image-based IMRT treatment plans are comparable to SPECT ventilation functional image-based plans

“…Ventilation images can also be acquired by a method based on four-dimensional (4D) computed tomography (CT) and image processing/analysis [12,13], henceforth referred to as CT ventilation imaging. CT ventilation imaging has the potential for widespread clinical implementation, as 4D-CT is routinely acquired for treatment planning at many centers [14] and ventilation computation only involves image processing/analysis without extra scans to patients.…”

Using 4DCT‐ventilation to characterize lung function changes for pediatric patients getting thoracic radiotherapy

“…Eq. (1) results in a unitless ratio of the amount of change in air content from inhale to exhale 2, 11. For display and evaluation purposes, we multiplied all raw ventilation values by 100.…”

Functional Imaging: CT and MRI

“…With the broader coverage, retrospective gating methods have emerged for both cardiac as well as pulmonary imaging whereby, via a very low pitch, images are gathered during the respiratory or cardiac cycles while recording the physiologic signal together with the projection images. Prospectively, (11) or retrospectively (10,(12)(13)(14)(15)(16)(17), the portions of the physiologic cycle of interest can be selected from within the slow pitch spiral data such that a volumetric image data set is reconstructed for just that location of the respiratory or cardiac cycle. Multiple portions of the physiologic cycle can thus be reconstructed to yield a dynamic image sequence of the organ of interest.…”

“…Multiple portions of the physiologic cycle can thus be reconstructed to yield a dynamic image sequence of the organ of interest. (10,(12)(13)(14)(15)(16)(17) In pulmonary applications, the earliest use of this method has been in oncology, tracking the maximum trajectory throughout a respiratory cycle for the purposes of treatment planning. (15,18).…”