Volumetric versus distortional deformation in rat lungs

There are several lung diseases that lead to alterations in regional lung mechanics, including acute respiratory distress syndrome. Such alterations can lead to localized underventilation of the affected areas resulting in the overdistension of the surrounding healthy regions. They can also lead to the surrounding alveoli expanding unevenly or distorting. Therefore, the quantification of the regional deformation in the lungs offers insights into identifying the regions at risk of lung injury. Although few recent studies have developed image processing techniques to quantify the regional volumetric deformation in the lung from dynamic imaging, the presence and extent of distortional deformation in the lung, and its correlation with volumetric deformation, remain poorly understood. In this study, we present a method that uses the four-dimensional displacement field obtained from image registration to quantify both regional volumetric and distortional deformation in the lung. We used dynamic computed tomography scans in a healthy rat over the course of one respiratory cycle in free breathing. Non-rigid image registration was performed to quantify voxel displacement during respiration. The deformation gradient was calculated using the displacement field and its determinant was used to quantify regional volumetric deformation. Regional distortion was calculated as the ratio of maximum to minimum principal stretches using the isochoric part of the Cauchy green tensor. We found an inverse correlation between volumetric strains and distortion indicating that poorly expanding alveoli tend to experience larger distortion. The combination of regional volumetric strains and distortion may serve as high-fidelity biomarkers to identify the regions at risk of most adverse lung injuries.

A psychiatric study of nonorganic chronic headache patients

Nonorganic chronic headache is a common, challenging presentation in clinical practice. The aim of this study was to investigate the frequency of associated psychiatric psychopathology, personality disorders, or traits. In addition, the study attempted to investigate possible relationships of nonorganic chronic headache with alexithymia, locus of control, and pain perception. Psychiatric pathology, personality traits, and pain profiles were examined in 100 randomized patients with chronic headache lacking an obvious organic basis, and they were compared with 100 subjects, 50 with headache of a known organic cause and 50 seemingly healthy persons, by using structured clinical interviews. Somatoform pain disorder was diagnosed in 43% of the nonorganic and 20% of the organic headache group. Nine percent of the former group had major depression, 16% had dysthymia, and 8% had both. In the organic group, 56% had no psychiatric disorder and 20% had somatoform pain disorder. Seventy-seven percent of the patients in the nonorganic pain group had personality disorders, mostly of the mixed and multiple types, compared with 24% of the organic headache patients. The study sample was more alexithymic than the other groups (in 65% of subjects) and had a culturally influenced locus of control and a pain profile characterized by dramatization, vagueness, lower pain threshold, and lower pain tolerance. The nonorganic chronic headache patients showed a high prevalence of somatoform, depressive, and other forms of psychiatric disorders. The high frequency of personality disorders, mostly the mixed and multiple types, the high alexithymic pattern, and low pain threshold and tolerance in the study group should be taken into consideration in the evaluation and management of nonorganic headache patients.