Is CT bulletproof? On the use of CT for characterization of bullets in forensic radiology

Purpose Forensic investigations could benefit from non-invasive in situ characterization of bullets. Therefore, the use of CT imaging was explored for the analysis of bullet geometry and composition. Bullet visualization with CT is challenging as the metal constituents suffer from excessive X-ray attenuation due to their high atomic number, density, and geometry. Methods A metal reference phantom was developed containing small discs of various common metals (aluminum, iron, stainless steel, copper, brass, tungsten, and lead). CT images were acquired with 70-150 kVp and 200-400 mAs and were reconstructed using an extended Hounsfield unit (HU) scale (- 10,240 to + 30,710). For each material, the mean CT number (HU) was measured to construct a metal database. Different bullets (n = 11) were scanned in a soft tissue-mimicking phantom. Bullet size and shape were measured, and composition was evaluated by comparison with the metal database. Also, the effect of bullet orientation within the CT scanner was evaluated. Results In the reference phantom, metals were classified into three groups according to their atomic number (Z): low (Z = 74; HU > 30,000). External bullet contours could be accurately delineated. Internal interfaces between jacket and core could not be identified. Cross-sectional spatial profile plots of the CT number along bullets' short axis revealed beam hardening and photon starvation effects that depended on bullet size, shape, and orientation within the CT scanner. Therefore, the CT numbers of bullets were unreliable and could not be used for material characterization by comparison with the reference phantom. Conclusion CT-based characterization of bullets was feasible in terms of size and shape but not composition

Perception of Bronchoconstriction:A Complementary Disease Marker in Children with Asthma

<p>Introduction. Asthma guidelines use symptoms as the most important aspect of asthma control. Symptom perception varies widely between individuals. Over-perception as well as underperception of bronchoconstriction could have a negative effect on asthma management. We hypothesized that perception of bronchoconstriction in childhood asthma is not related to common measures of disease control. For that reason, we examined the clinical determinants of the perception of bronchoconstriction and the repeatability of perception measurements. Patients and methods. In school-age children with moderately severe atopic asthma, we measured the perception of bronchoconstriction (decrease in forced expiratory volume in 1 second (FEV1)) during methacholine bronchoprovocation challenges. The perception of bronchoconstriction was assessed as the slope of the relation between FEV1 and Borg score, and as the Borg score at a 20% decrease in FEV1 from baseline during the provocation test (PS20). Data from subjects who had a 20% or more decrease in FEV1 (n=112) were used for the analysis. Fifty-four children repeated the test after 3 months. Symptoms, use of rescue medication, and peak expiratory flows were scored in diaries during the 2 weeks before testing. Results. Symptom perception was significantly better in children without (PD20 > 1570 mu g, n=28) than in children with airway hyperresponsiveness (PD20</p>