Computerized detection of pulmonary nodules by single-exposure dual-energy computed radiography of the chest (part 1)

OBJECTIVE: To clarify the usefulness of computerized detection of pulmonary nodules (PNs) in single-exposure dual-energy subtraction computed radiography (CR) images of the chest. METHODS AND MATERIAL: Our scheme uses bone-subtracted CR (BS-CR) images, and consists of a contrast-adaptive filter for detection of the candidates for PNs and a vessel-enhancing filter for elimination of vessel opacities in the candidates for PNs. For the evaluation, 12 clinical cases with multiple PNs were used, and four radiologists participated in this study. RESULTS: The detectability of our computer-aided diagnosis (CAD) was compared with detectabilities of radiologists. The mean true-positive (TP) number of four radiologists was 1.60+/-1.03, and that of the CAD was 1.83+/-1.34. There was no significant difference in the nodule detectabilities between the radiologists and CAD (P=0.18). However, the false-positive (FP) rate of the CAD was 9.42+/-2.54 per image, whereas the mean FP rate of the radiologists was 1.40+/-0.64 per image. CONCLUSION: Computerized detection of PNs is considered to be useful in the determination of radiological diagnoses. However, reducing the number of FP findings remains an important problem to be solved.     

Detection of lung cancer using single-exposure dual-energy subtraction chest radiography

PURPOSE: The aim of this study was to evaluate the detectability of lung cancer by chest radiography with a single-exposure dual-energy subtraction (ES) method. MATERIALS AND METHODS: Five radiologists read two sets of chest radiographs from 77 patients (66.5 +/- 9.6 years old) with histologically proven lung cancer measuring or=50 but <100%; (3) solid: TDR was <50%. RESULTS: Overall, detectability with the ES method was significantly better than that without ES (mean Az value increased from 0.7673 to 0.8265, P < 0.05). In the subgroup analysis of the nonsolid group and the solid group detectability did not change using the ES method, whereas in the partly solid group detectability with the ES method was significantly better than that without ES (mean Az value increased from 0.7162 to 0.8209, P < 0.005). CONCLUSION: The ES method improves the detectability of lung cancer by chest radiography, especially of the partly solid group.     

Single-exposure dual-energy subtraction chest radiography: Detection of pulmonary nodules and masses in clinical practice

The purpose of this retrospective study was to evaluate the impact of energy subtraction (ES) chest radiography on the detection of pulmonary nodules and masses in daily routine. Seventy-seven patients and 25 healthy subjects were examined with a single exposure digital radiography system. Five blinded readers evaluated first the non-subtracted PA and lateral chest radiographs alone and then together with the subtracted PA soft tissue images. The size, location and number of lung nodules or masses were registered with the confidence level. CT was used as standard of reference. For the 200 total lesions, a sensitivity of 33.5–52.5% was found at non-subtracted and a sensitivity of 43.5–58.5% at energy-subtracted radiography, corresponding to a significant improvement in four of five readers (p < 0.05). However, in three of five readers the rate of false positives was higher with ES. With ES, sensitivity, but not the area under the alternative free-response receiver operating characteristics (AFROC) curve, showed a good correlation with reader experience (R = 0.90, p = 0.026). In four of five readers, the diagnostic confidence improved with ES (p = 0.0036). We conclude that single-exposure digital ES chest radiography improves detection of most pulmonary nodules and masses, but identification of nodules <1 cm and false-positive findings remain a problem.     

Clinical evaluation of pulmonary nodules with dual-exposure dual-energy subtraction chest radiography

PURPOSE: The purpose of this study was to assess the effect of dual-exposure dual-energy (DE) subtraction chest radiography with flat-panel detector. MATERIALS AND METHODS: One hundred patients underwent dual-exposure DE subtraction chest radiography and chest CT for evaluation of pulmonary nodules. Fifty-two patients with pulmonary nodules and 48 patients with normal lungs were selected for receiver operating characteristic (ROC) curve analysis. Ten radiologists who were unaware of the CT results evaluated chest radiography alone and chest radiography with DE subtraction images in the detection of pulmonary nodules. For each radiologist, we calculated the areas under the ROC curve (Az) for chest radiography alone and chest radiography with DE subtraction images. RESULTS: The average detectability of dual-exposure DE subtraction chest radiography was statistically significantly higher than that of chest radiography without subtraction images (mean Az value increased from 0.784 to 0.815, p<0.001). CONCLUSION: Dual-exposure DE subtraction chest radiography improves diagnostic accuracy of pulmonary nodules.     

应用计算机辅助检测系统对观察者在数字化胸片肺结节检测中的训练

摘要目的评估短期反馈能否帮助观察者提高在数字化胸片中运用计算机辅助系统(CAD)检测肺结节的能力。方法140例胸部平片(56例CT证实存在孤立性肺结节,84例为阴性对照)分为4组,每组各35例;每组均有6名观察者按不同顺序阅片。在有和没有CAD(IQQA-Chest,EDDA Technology)辅助情况下分别对病变的存在、部位、诊断的可靠性进行计分。观察者在每组阅片后获得独立的反馈。     

Detectability of simulated pulmonary nodules on chest radiographs: Comparison between irradiation side sampling indirect flat-panel detector and computed radiography

Objective

To compare the detectability of simulated pulmonary nodules on chest radiographs between an irradiation side sampling indirect flat-panel detector (ISS-FPD) and computed radiography (CR).

Materials and methods

This study was an observer performance study. Simulated pulmonary nodules of 8 mm in diameter were superimposed on an anthropomorphic chest phantom. Chest radiographs were acquired under 2 exposure levels (4 and 3.2 mAs) with the ISS-FPD and the CR. Six thoracic radiologists evaluated all 40 images (10 patterns × 2 different exposure doses × 2 different systems) for the presence or absence of a lesion over each of 12 defined areas on a 3-megapixel monochrome liquid-crystal display. Receiver operating characteristic (ROC) curves were obtained for observation in predefined 480 areas. A jackknife method was used for statistical analysis. Differences with a P value of <0.05 were considered significant.

Results

The analysis of the observer detection of simulated pulmonary nodules showed larger areas under the ROC curve (AUC) by the ISS-FPD than by the CR. There was a statistically significant difference between the two systems at 3.2 mAs (P = 0.0330).

Conclusion

The ISS-FPD was superior to the CR for the detection of simulated pulmonary nodules at 3.2 mAs.     

Detection of simulated nodules on clinical radiographs: dose reduction at digital posteroanterior chest radiography

PURPOSE: To determine to what extent dose reduction results in decreased detection of simulated nodules on patient digital posteroanterior (PA) chest radiographs. MATERIALS AND METHODS: Raw data from 20 clinical digital PA chest images that were reported as having normal findings and that were obtained with a slot-scan charge-coupled device system were used. For research protocol that concerns data with patient identities concealed, institutional review board approval is not required. One hundred twenty nodules varying in size and signal intensity were digitally simulated and added to the chest images. Hard copies were printed to represent a 100% dose and, by adding noise, to represent simulated patient doses of 50%, 25%, and 12%. Four radiologists reviewed images. Each lesion was registered as "detected" or "not detected." A semiparametric logistic regression model was used for statistical analysis. RESULTS: The decrease in radiation dose from 100% to 50%, 25%, or 12% had no effect on lesion detection in the lungs. The decrease in radiation dose had an effect on lesion detection in the mediastinum, as probabilities deteriorated from the 100% dose to the 50%, 25%, and 12% dose with each step. Probabilities of smaller detection rates when compared with that of the reference category (100% dose) were 0.97 (95% confidence interval [CI]: -0.86, 0.012) for the 50% dose, 1 (CI: -0.59, -0.61) for the 25% dose, and 1 (CI: -2.41, -1.22) for the 12% dose. CIs for the effects were on the log(odds). Detection probability decreased with smaller and lower signal intensity lesions. CONCLUSION: At clinical digital radiography, dose reduction resulted in decreased observer detection of simulated nodules in the mediastinum but not in the lungs.     

Temporal subtraction for detection of solitary pulmonary nodules on chest radiographs: evaluation of a commercially available computer-aided diagnosis system

PURPOSE: To evaluate the usefulness of a commercially available computer-aided diagnosis (CAD) system that incorporates temporal subtraction for the detection of solitary pulmonary nodules on chest radiographs by readers with different levels of experience. MATERIALS AND METHODS: Sixty pairs of chest radiographs in 30 patients with newly detected solitary pulmonary nodules and 30 normal cases, all confirmed with serial chest computed tomography (CT), were obtained from screen-film or digital radiographic systems and were digitized (spatial resolution, 0.171 mm/pixel). Temporal subtraction images were produced with an iterative image-warping technique. Five chest radiologists and five residents evaluated both image sets for solitary nodules: set A, current and prior radiographs with temporal subtraction images, and set B, current and prior radiographs only. Assessment was performed with receiver operating characteristic (ROC) analysis of the images on a monitor (pixel size, 1,280 x 1,024) equipped with the system. The reading time needed by each reader was recorded in each case. RESULTS: For the chest radiologists, no statistically significant difference was found between set A (area under the ROC curve [A(z)] = 0.934) and set B (A(z) = 0.964). For the residents, however, observer performance in set A (A(z) = 0.907) was superior to that in set B (A(z) = 0.855) (P <.05). For both groups, the mean reading time per case for set A (chest radiologists, 16.7 seconds; residents, 15.7 seconds) was significantly (P <.05) shorter than that for set B (chest radiologists, 20.4 seconds; residents, 26.2 seconds). CONCLUSION: For the detection of solitary pulmonary nodules, the CAD system with temporal subtraction can promote efficiency for established chest radiologists and improvement in accuracy for less experienced readers.     

Improved detection of lung nodules on chest radiographs using a commercial computer-aided diagnosis system

OBJECTIVE: The aim of this study was to evaluate the usefulness of a new commercially available computer-aided diagnosis (CAD) system with an automated method of detecting nodules due to lung cancers on chest radiograph. MATERIALS AND METHODS: For patients with cancer, 45 cases with solitary lung nodules up to 25 mm in diameter (nodule size range, 8-25 mm in diameter; mean, 18 mm; median, 20 mm) were used. For healthy patients, 45 cases were selected on the basis of confirmation on chest CT. All chest radiographs were obtained with a computed radiography system. The CAD output images were produced with a newly developed CAD system, which consisted of an image server including CAD software called EpiSight/XR. Eight radiologists (four board-certified radiologists and four radiology residents) participated in observer performance studies and interpreted both the original radiographs and CAD output images using a sequential testing method. The observers' performance was evaluated with receiver operating characteristic analysis. RESULTS: The average area under the curve value increased significantly from 0.924 without to 0.986 with CAD output images. Individually, the use of CAD output images was more beneficial to radiology residents than to board-certified radiologists. CONCLUSION: This CAD system for digital chest radiographs can assist radiologists and has the potential to improve the detection of lung nodules due to lung cancer.     

Pulmonary nodules at chest CT: effect of computer-aided diagnosis on radiologists' detection performance

PURPOSE: To evaluate the effect of computer-aided diagnosis (CAD) on radiologists' detection of pulmonary nodules. MATERIALS AND METHODS: Fifty chest computed tomographic (CT) examination cases were used. The mean nodule size was 0.81 cm +/- 0.60 (SD) (range, 0.3-2.9 cm). Alternative free-response receiver operating characteristic (ROC) analysis with a continuous rating scale was used to compare the observers' performance in detecting nodules with and without use of CAD. Five board-certified radiologists and five radiology residents participated in an observer performance study. First they were asked to rate the probability of nodule presence without using CAD; then they were asked to rate the probability of nodule presence by using CAD. RESULTS: For all radiologists, the mean areas under the best-fit alternative free-response ROC curves (Az) without and with CAD were 0.64 +/- 0.08 and 0.67 +/- 0.09, respectively, indicating a significant difference (P <.01). For the five board-certified radiologists, the mean Az values without and with CAD were 0.63 +/- 0.08 and 0.66 +/- 0.09, respectively, indicating a significant difference (P <.01). For the five resident radiologists, the mean Az values without and with CAD were 0.66 +/- 0.04 and 0.68 +/- 0.04, respectively, indicating a significant difference (P =.02). At observer performance analyses, there were no significant differences in Az values obtained either without (P =.61) or with (P =.88) CAD between the board-certified radiologists and the residents. For all radiologists, in the detection of pulmonary nodules 1.0 cm in diameter or smaller, the mean Az values without and with CAD were 0.60 +/- 0.11 and 0.64 +/- 0.11, respectively, indicating a significant difference (P <.01). CONCLUSION: Use of the CAD system improved the board-certified radiologists' and residents' detection of pulmonary nodules at chest CT.     

Evaluation of a method of computer-aided detection (CAD) of pulmonary nodules at computed tomography

Purpose

The authors sought to compare the sensitivity and reading time obtained using computer-aided detection (CAD) software as second reader (SR) or concurrent reader (CR) in the identification of pulmonary nodules.

Materials and methods

Unenhanced CT scans of 100 consecutive cancer patients were retrospectively reviewed by four readers to identify all solid, noncalcified pulmonary nodules ranging from 3 to 30 mm in diameter. The sensitivity and reading time of each reader and of CAD alone were calculated at 3-mm and 5-mm thresholds with respect to the reference standard, consisting of a consensus reading by the four radiologists involved in the study. The McNemar test was used to compare the sensitivities obtained by reading without CAD (readers 1 and 2), with CAD as SR (readers 1 and 2 with a 2-month delay), and with CAD as CR (readers 3 and 4). The paired Student’s t test was used to compare reading times. A value of p<0.05 was considered statistically significant.

Results

A total of 258 and 224 nodules were identified at 3-mm and 5-mm thresholds, respectively. The sensitivity of CAD alone was 62.79% and 67.41% at the 3-mm and 5-mm threshold values respectively, with 4.15 and 2.96 false-positive findings per examination. CAD as SR produced a significant increase in sensitivity (p<0.001) in nodule detection with respect to reading without CAD both at 3 mm (12.01%) and 5 mm (10.04%); the average increase in sensitivity obtained when comparing CAD as SR to CAD as CR was statistically significant (p<0.025) both at the 3-mm (5.35%) and 5-mm (4.68%) thresholds. CAD as CR produced a nonsignificant increase in sensitivity compared with reading without CAD (p>0.05). Mean reading time using CAD as SR (330 s) was significantly longer than reading without CAD (135 s, p<0.001) and reading with CAD as CR (195 s, p<0.025).

Conclusions

The use of CAD as CR, without any significant increase in reading time, produces no significant increase in sensitivity in pulmonary nodule detection when compared with reading without CAD (p>0.05); CAD as SR, at the cost of longer reading times, increases sensitivity when compared with reading without CAD (p<0.001) or with CAD as CR (p<0.025).     

双能量减影与常规胸片诊断肺内孤立性结节的临床对比

我们对40例经CT证实肺内确实存在孤立性结节患者行常规胸片和胸部DES检查,依此来探讨DES与常规胸片在显示肺内孤立性结节方面的优势和价值。1资料与方法搜集2004年5~12月经CT检查证实肺内有孤立性结节的患者40例,男24例,女16例;年龄32~70岁,平均49岁。所有患者均在CT检查3 d内进行常规胸片及DES检查,使用GE RevolutionXR/d型DR摄影系统。常规X线成像条件是110~120 kV,DES的2次曝光间隔为0·2 s,条件分别为120~140 kV和60~70 kV。焦点到平板探测器的距离为180 cm,投照体位均为后前位,深吸气屏(+)(-)2416346合计40 40χ2=6·270 P…     

Usefulness of temporal subtraction images of chest computed radiography for detection of metastatic pulmonary nodules

Temporal subtraction is a technique by which a previous chest radiograph is subtracted from a current radiograph in order to enhance interval changes. Our purpose in this study was to evaluate the usefulness of temporal subtraction for the detection of metastatic pulmonary nodules. We examined 19 cases of metastatic nodules less than 15 mm in diameter (8.4 mm on average). Temporal subtraction images were created based on the matching of local lung areas in pairs of chest radiographs. By using the subtraction images, the detectability of nodules was clearly improved in 5 cases and moderately improved in 8 cases; there was no improvement in 6 cases. The subtraction images were especially useful for nodules superimposed over normal structures, such as rib, mediastinum, and diaphragm, as well as for small nodules. In 6 of the 19 cases, the nodules had been missed clinically; however, the temporal subtraction images clearly demonstrated half of missed small nodules. Temporal subtraction made it possible to enhance subtle interval changes and helped in detecting small pulmonary metastases. This technique seems promising for augmenting the capabilities of computed radiography of the chest.     

Detection of pulmonary nodules by computed tomography.

In 11 of 23 patients, computed tomography of the chest detected pulmonary nodules that were not detected by conventional chest radiography or whole lung tomography. CT is recommended for patients suspected of having pulmonary metastasis and those with a solitary pulmonary nodule.     

One-shot dual-energy subtraction chest imaging with computed radiography: clinical evaluation of film images

A clinical evaluation of one-shot dual-energy subtraction chest imaging by means of computed radiography (CR) with imaging plates was carried out in a comparison with the original plain CR images. In analyses of chest images of 140 patients, new information, not detected on the original plain CR images, was obtained on subtraction images in 21 patients (15%). Receiver operating characteristic curve studies also verified the superiority of CR subtraction over the original plain CR images for the detection of pulmonary nodules, calcification in a nodule, and rib lesions. Subtraction images complemented the original plain images.