Computer tomography perfusion patterns in iatrogenic cerebral arterial gas embolism: A retrospective cohort study.

PURPOSE: Cerebral arterial gas embolism (CAGE) occurs when air or medical gas enters the systemic circulation during invasive procedures and lodges in the cerebral vasculature. Non-contrast computer tomography (CT) may not always show intracerebral gas. CT perfusion (CTP) might be a useful adjunct for diagnosing CAGE in these patients. METHODS: This is a retrospective single-center cohort study. We included patients who were diagnosed with iatrogenic CAGE and underwent CTP within 24 h after onset of symptoms between January 2016 and October 2022. All imaging studies were evaluated by two independent radiologists. CTP studies were scored semi-quantitatively for perfusion abnormalities (normal, minimal, moderate, severe) in the following parameters: cerebral blood flow, cerebral blood volume, time-to-drain and time-to-maximum. RESULTS: Among 27 patient admitted with iatrogenic CAGE, 15 patients underwent CTP within the designated timeframe and were included for imaging analysis. CTP showed perfusion deficits in all patients except one. The affected areas on CTP scans were in general located bilaterally and frontoparietally. The typical pattern of CTP abnormalities in these areas was hypoperfusion with an increased time-to-drain and time-to-maximum, and a corresponding minimal decrease in cerebral blood flow. Cerebral blood volume was mostly unaffected. CONCLUSION: CTP may show specific perfusion defects in patients with a clinical diagnosis of CAGE. This suggests that CTP may be supportive in diagnosing CAGE in cases where no intracerebral gas is seen on non-contrast CT.

Gray-scale reversal for the detection of pulmonary nodules on a PACS workstation.

OBJECTIVE: The purpose of this article is to evaluate the impact of gray-scale reversal on the detection of small pulmonary nodules in two-view chest radiography. MATERIALS AND METHODS: One hundred twenty-eight patients (mean age, 62 years) who underwent CT and chest radiography within 6 weeks were retrospectively selected for this study. Seventy-three percent of patients showed variable degrees of radiographic findings of a "dirty lung." A total of 129 solid pulmonary nodules were present in 74 patients (nodule diameter range, 5-30 mm; mean diameter, 13 mm). The remaining 54 patients served as negative control subjects. Six readers with varying experience levels evaluated the images without and with the availability of gray-scale reversal in two separate reading sessions. Figure of merit (FOM), sensitivity per lesion, mean number of false-positive marks per image, and accuracy were calculated. RESULTS: Five of the six readers showed a slight increase in sensitivity with the use of gray-scale reversal, but on average, the difference was not significant (48% vs 50%; p > 0.05). The mean number of false-positive marks per image also nonsignificantly increased from 0.20 to 0.23. The increases in both sensitivity and the mean number of false-positive marks per image translated into nonsignificant decreases in average FOM (0.79 vs 0.77) and accuracy (72% vs 71%). Data analysis of subgroups of nodules or different reader groups, depending on level of experience, did not reveal significant differences. CONCLUSION: Using PACS display of digital chest radiographs, gray-scale reversal does not help the radiologists in detecting pulmonary nodules.

Computer-aided detection of small pulmonary nodules in chest radiographs: an observer study.

RATIONALE AND OBJECTIVES: To evaluate the impact of computer-aided detection (CAD, IQQA-Chest; EDDA Technology, Princeton Junction, NJ) used as second reader on the detection of small pulmonary nodules in chest radiography (CXR). MATERIALS AND METHODS: A total of 113 patients (mean age 62 years) with CT and CXR within 6 weeks were selected. Fifty-nine patients showed 101 pulmonary nodules (diameter 5-15mm); the remaining 54 patients served as negative controls. Six readers of varying experience individually evaluated the CXR without and with CAD as second reader in two separate reading sessions. The sensitivity per lesion, figure of merit (FOM), and mean false positive per image (mFP) were calculated. Institutional review board approval was waived. RESULTS: With CAD, the sensitivity increased for inexperienced readers (39% vs. 45%, P < .05) and remained unchanged for experienced readers (50% vs. 51%). The mFP nonsignificantly increased for both inexperienced and experienced readers (0.27 vs. 0.34 and 0.16 vs. 0.21). The mean FOM did not significantly differ for readings without and with CAD irrespective of reader experience (0.71 vs. 0.71 and 0.84 vs. 0.87). All readers together dismissed 33% of true-positive CAD candidates. False-positive candidates by CAD provoked 40% of all false-positive marks made by the readers. CONCLUSION: CAD improves the sensitivity of inexperienced readers for the detection of small nodules at the expense of loss of specificity. Overall performance by means of FOM was therefore not affected. To use CAD more beneficial, readers need to improve their ability to differentiate true from false-positive CAD candidates.