Bone suppression increases the visibility of invasive pulmonary aspergillosis in chest radiographs

Objective: Chest radiographs (CXR) are an important diagnostic tool for the detection of invasive pulmonary aspergillosis (IPA) in critically ill patients, but their diagnostic value is limited by a poor sensitivity. By using advanced image processing, the aim of this study was to increase the value of chest radiographs in the diagnostic work up of neutropenic patients who are suspected of IPA. Methods: The frontal CXRs of 105 suspected cases of IPA were collected from four institutions. Radiographs could contain single or multiple sites of infection. CT was used as reference standard. Five radiologists and two residents participated in an observer study for the detection of IPA on CXRs with and without bone suppressed images (ClearRead BSI 3.2; Riverain Technologies). The evaluation was performed separately for the right and left lung, resulting in 78 diseased cases (or lungs) and 132 normal cases (or lungs). For each image, observers scored the likelihood of focal infectious lesions being present on a continuous scale (0-100). The area under the receiver operating characteristics curve (AUC) served as the performance measure. Sensitivity and specificity were calculated by considering only the lungs with a suspiciousness score of greater than 50 to be positive. Results: The average AUC for only CXRs was 0.815. Performance significantly increased, to 0.853, when evaluation was aided with BSI (p = 0.01). Sensitivity increased from 49% to 66% with BSI, while specificity decreased from 95% to 90%. Conclusion: The detection of IPA in CXRs can be improved when their evaluation is aided by bone suppressed images. BSI improved the sensitivity of the CXR examination, outweighing a small loss in specificity

Bone suppression increases the visibility of invasive pulmonary aspergillosis in chest radiographs

textabstractObjective: Chest radiographs (CXR) are an important diagnostic tool for the detection of invasive pulmonary aspergillosis (IPA) in critically ill patients, but their diagnostic value is limited by a poor sensitivity. By using advanced image processing, the aim of this study was to increase the value of chest radiographs in the diagnostic work up of neutropenic patients who are suspected of IPA. Methods: The frontal CXRs of 105 suspected cases of IPA were collected from four institutions. Radiographs could contain single or multiple sites of infection. CT was used as reference standard. Five radiologists and two residents participated in an observer study for the detection of IPA on CXRs with and without bone suppressed images (ClearRead BSI 3.2; Riverain Technologies). The evaluation was performed separately for the right and left lung, resulting in 78 diseased cases (or lungs) and 132 normal cases (or lungs). For each image, observers scored the likelihood of focal infectious lesions being present on a continuous scale (0-100). The area under the receiver operating characteristics curve (AUC) served as the performance measure. Sensitivity and specificity were calculated by considering only the lungs with a suspiciousness score of greater than 50 to be positive. Results: The average AUC for only CXRs was 0.815. Performance significantly increased, to 0.853, when evaluation was aided with BSI (p = 0.01). Sensitivity increased from 49% to 66% with BSI, while specificity decreased from 95% to 90%. Conclusion: The detection of IPA in CXRs can be improved when their evaluation is aided by bone suppressed images. BSI improved the sensitivity of the CXR examination, outweighing a small loss in specificity

Subtlety categories.

<p>Number of cases classified into the different subtlety categories.</p><p>Subtlety categories.</p

Patient demographics.

<p>Age, gender, average time between the chest radiograph and the CT in days, and projection type are displayed for the diseased and normal cases. n  =  number.</p><p>Patient demographics.</p

Bedside radiograph of a 58 year old female with neutropenic fever.

<p>Without BSI, 3 of the 7 observers called the radiograph suspicious, which increased to 7 observers with BSI. Original radiograph (A), bone suppressed image (B), coronal CT slice (C).</p

Number of, on average, detected cases per subtlety category.

<p>Number of, on average, detected cases per subtlety category.</p

Upright radiograph with a very subtle lesion in the left lower lobe.

<p>Without BSI only one observer marked the small lesion. With BSI all 7 observers marked the lesion with an average suspiciousness score of 55. Original radiograph (A), bone suppressed image (B), coronal CT slice (C).</p

Sensitivity and specificity.

<p>Individual sensitivities and specificities for the detection of IPA in chest radiographs without and with BSI, based on marking with a suspiciousness score above 50. * Δ = difference.</p><p>Sensitivity and specificity.</p

Observer performance.

<p>Average area under the ROC curves (AUC) for all observers. AUCs are displayed for all images and for analysis of the different groups of projection type (bedside and upright).</p><p>Observer performance.</p

Example of a moderately subtle case of a 35 year old female with multiple focal lesions in the right lung.

<p>Without BSI 6 of the 7 observers marked this case with an average suspiciousness score of 63. With BSI all observers marked the case with an average suspiciousness score of 91. Original radiograph (A), bone suppressed image (B), coronal CT slice (C).</p