Computer-Aided Volumetry of Pulmonary Nodules Exhibiting Ground-Glass Opacity at MDCT

high-resolution CT may help in differential diagnosis. Because the doubling time of BAC is long (average, 457-813 days) With MDCT it is possible to scan a wide range, including areas containing pulmonary nodules, at a detector collimation of 0.500-0.625 mm in one breath-hold. This capability facilitates 3D evaluation of pulmonary nodules. In previous studies C a r d io p u lm o n a r y I m ag i ng • O r ig i n a l R e s e a rc h MATERIALS AND METHODS. To evaluate the accuracy of computer-aided volumetry software, we performed thin-section helical CT of a chest phantom that included simulated 3-, 5-, 8-, 10-, and 12-mm-diameter ground-glass opacity nodules with attenuation of -800, -630, and -450 HU. Three radiologists measured the volume of the nodules and calculated the relative volume measurement error, which was defined as follows: (measured nodule volume minus assumed nodule volume ÷ assumed nodule volume) × 100. Two radiologists performed two independent measurements of 59 nodules in humans. Intraobserver and interobserver agreement was evaluated with Bland-Altman methods. RESULTS. The relative volume measurement error for simulated ground-glass opacity nodules measuring 3 mm ranged from 51.1% to 85.2% and for nodules measuring 5 mm or more in diameter ranged from -4.1% to 7.1%. In the clinical study, for intraobserver agreement, the 95% limits of agreement were -14.9% and -13.7% and -16.6% to 15.7% for observers A and B. For interobserver agreement, these values were -16.3% to 23.7% for nodules 8 mm in diameter or larger. CONCLUSION. With computer-aided volumetry of ground-glass opacity nodules, the relative volume measurement error was small for nodules 5 mm in diameter or larger. Intraobserver and interobserver agreement was relatively high for nodules 8 mm in diameter or larger

Effects of dual-energy subtraction chest radiography on detection of small pulmonary nodules with varying attenuation: receiver operating characteristic analysis using a phantom study

Purpose: To investigate the detectability of simulated pulmonary nodules with different X-ray attenuation by flat-panel detector (FPD) chest radiography using a dual-exposure dual-energy subtraction (DES) technique.Materials and Methods: Using a FPD radiography system we obtained 108 sets of chest radiographs of a chest phantom. They consisted of 54 sets each of chest radiographs with- and without simulated nodules. Each data set contained a standard- and a corresponding dual-energy subtracted chest radiograph (DES image). The diameter of the simulated nodules was 8-, 10-, and 12 mm; nodules of each size manifested attenuation of -450, -200, and 30 Hounsfield units (HU). We performed receiver operating characteristic (ROC) analysis to compare the observers’ performance in detecting nodules.Results: For -450 HU nodules the mean area under the ROC curve (AUC) without and with DES images was 0.66 and 0.77, respectively; the difference was significant (paired t-test, p < 0.01). For nodules with -200- and 30 HU, there was no significant difference in the AUC value (0.79 vs. 0.77, p=0.13; 0.92 vs. 0.94, p=0.17, respectively).Conclusion: The addition of DES images to standard chest radiographs improved the performance of radiologists charged with detecting simulated nodules with an attenuation of -450 HU

Uniform Vascular Enhancement of Lower-Extremity Artery on CT Angiography Using Test-Injection Monitoring at the Central Level of the Scan Range: A Simulation Flow Phantom Study with Clinical Correlation

RATIONALE AND OBJECTIVES: To evaluate the efficacy of variable contrast injection durations and scanning delay determined by test injection analysis of computed tomography angiography (CTA) of peripheral arteries. nMATERIALS AND METHODS: We used a flow phantom that simulates the hemodynamics in a lower extremity artery. We set the flow rate at the pump to 2.0 or 5.0 L/minute. In protocol 1, we adopted a variable contrast injection duration based on the peak enhancement time of the test injection monitoring at the central level of the scan range. In protocol 2, we adopted a fixed contrast injection duration. The scanning delay was determined with a conventional bolus-tracking technique monitoring at the top of the scan range. Mean arterial attenuation and difference between the maximum and minimum attenuation values were calculated. To verify the phantom study results, clinical study, including 16 patients was performed under protocol 1. nRESULTS: The mean attenuation values under protocols 1 and 2 were comparable (563.6 Hounsfield units [HU] and 535.0 HU, respectively) at a pump flow rate of 2.0 L/minute; at 5.0 L/minute, they were 289.4 HU and 328.8 HU. The difference between the maximum and minimum attenuation values was smaller under protocol 1 than protocol 2 (76.8 HU vs. 184.9 HU) at a pump flow of 2.0 L/minute and also smaller under protocol 1 than protocol 2 (79.7 HU vs. 203.8 HU) at 5.0 L/minute. In clinical study, the mean attenuation value was 332.6 +/- 51.9 HU, and the difference between the maximum and minimum attenuation values was 55.1 +/- 24.4 HU. nCONCLUSION: The object-specific injection duration based on test injection at the central level of the scan range provides sufficient and constant vascular enhancement at CTA

Detection of small pulmonary nodules on chest radiographs: efficacy of dual-energy subtraction technique using flat-panel detector chest radiography

AIM:We investigated the effect of a double-exposure dual-energy subtraction (DES) technique on the performance of radiologists detecting small pulmonary nodules on flat-panel detector (FPD) chest radiographs.MATERIALS AND METHODS:Using FPD radiography we obtained 41 sets of chest radiographs from 26 patients with pulmonary nodules measuring ≤ 20 mm and from 15 normal subjects. Each data set included standard- and corresponding DES images. There were 6 non-solid-, 10 part-solid-, and 10 solid nodules. The mean size of the 26 nodules was 15.0 ± 4.8 mm. We performed receiver operating characteristic (ROC) analysis to compare the performance of 8 board-certified radiologists.RESULTS:For the 8 radiologists, the mean value of the area under the ROC curve (AUC) without and with DES images was 0.62 ± 0.05 and 0.68 ± 0.05, respectively; the difference was statistically significant (p = 0.02). For part-solid nodules, the difference of the mean AUC value was statistically significant (AUC = 0.61 ± 0.07 vs. 0.69 ± 0.05; p < 0.01); for non-solid nodules it was not (AUC = 0.62 ± 0.10 vs. 0.61 ± 0.09; p = 0.73), and for solid nodules it was not (AUC = 0.75 ± 0.10 vs. 0.78 ± 0.08; p = 0.23). For nodules with overlapping bone shadows, the difference of the mean AUC value was statistically significant (p = 0.03), for nodules without overlapping, it was not (p = 0.26).CONCLUSION:Use of a double-exposure DES technique at FPD chest radiography significantly improved the diagnostic performance of radiologists detecting small pulmonary nodules