title: CT analysis of lung density changes in patients undergoing total body irradiation prior to bone marrow transplantation.
abstract: Sequential changes in lung density measured by CT are potentially sensitive and convenient monitors of lung abnormalities following total body irradiation (TBI). Methods have been developed to compare pre- and post-TBI CT of lung. The average local features of a cross-sectional lung slice are extracted from three peripheral regions of interest in the anterior, posterior, and lateral portions of the CT image. Also, density profiles across a specific region may be obtained. These may be compared first for verification of patient position and breathing status and then for changes between pre- and post-TBI. These may also be compared with radiation dose profiles through the lung. A preliminary study on 21 leukemia patients undergoing total body irradiation indicates the following: (a) Density gradients of patients' lungs in the antero-posterior direction show a marked heterogeneity before and after transplantation compared with normal lungs. The patients with departures from normal density gradients pre-TBI correlate with later pulmonary complications. (b) Measurements of average peripheral lung densities have demonstrated that the average lung density in the younger age group is substantially higher: pre-TBI, the average CT number (1,000 scale) is -638 +/- 39 Hounsfield unit (HU) for 0-10 years old and -739 +/- 53 HU for 21-40 years old. (c) Density profiles showed no post-TBI regional changes in lung density corresponding to the dose profile across the lung, so no differentiation of a radiation-specific effect has yet been possible. Computed tomographic density profiles in the antero-posterior direction are successfully used to verify positioning of the CT slice and the breathing level of the lung.
mesh_terms: D000293:Adolescent; D000328:Adult; D001855:Bone Marrow Diseases / Q000628:therapy; D016026:Bone Marrow Transplantation; D002648:Child; D002675:Child, Preschool; D003131:Combined Modality Therapy; D006801:Humans; D007223:Infant; D007938:Leukemia / Q000628:therapy*; D008168:Lung / Q000000981:diagnostic imaging* / Q000528:radiation effects; D008433:Mathematics; D012119:Respiration; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014916:Whole-Body Irradiation / Q000009:adverse effects; D014939:Work of Breathing