Quantitative ComputedTomography Detects AirTrapping duetoAsthma

Objective: Thepurpose ofthis study wastoprospectively seeifquantitative computed tomography (QCT) could separate asthmatic patients fromnormal control subjects. TheQCTresults werealso correlated withthe pulmonary function tests (PF1) that weredoneonboth theasthmatic patients andcontrol subjects. Subjects andmethods: Eighteen adult nonsmoking asthmatics and22adult control subjects wereentered into thestudy. Quantitative CTwasperformed atthe level ofthetransverse aorta andjust abovethediaphragm atboth endinspiration andendexpiration inall patients andcontrol subjects: 10-mmand1.5-mm collimation using ahighspatial frequency algorithm was usedtoobtain theQCTexaminations. Thepercent of pixels below -900Hounsfeld units, pixel index, ineach oftheQCTaxial images ofthelungs wascalculated for eachasthmatic andcontrol subject inthestudy. Pulmonaryfunction testing wasperformed onboththe asthmatics andcontrol subjects andincluded determination ofFEV1, FVC,FRC,RV,andTLC.Unpaired Student's ttest analysis oftheQCTdatawasdoneto statistically compare theasthmatics withthecontrol subjects. Linear regression analysis wasdonetocomparetheQCTresults withPF1dataontheasthmatics andcontrol subjects. Results: Whenscans wereperformed atendexpiration, Computedtomography (CT)andhigh-resolution CT(HRCT) areuseful indiagnosing airways diseases such asemphysema,18 bronchiectasis,9"'1 bronchiolitis,'2 andbronchiolitis obliterans.13'16 However, these tools haveamuchmorelimited role intheassessment ofasthma andchronic bronchitis, inpart because bronchial wallthickening andairtrapping havebeendifficult toquantify byCT.