Cost-effectiveness of stereoscopic radiographs in detection of lung nodules

Detection of lung nodules was assessed using a series of radiographs which were either normal or showed only one nodule. Stereoscopic pairs were obtained in 26 cases (10 positive and 16 normal). A "singles" series comprising one radiograph from each pair was presented to each observer on three occasions. The pairs were later presented side by side and finally were viewed stereoscopically. The results indicate that a second shifted radiograph improves detection of lung nodules enough to be cost-effective. The shifted radiographs do not need to be viewed stereoscopically.     

The value of searching films without specific preconceptions

The detection of simulated pulmonary nodules was measured in three different situations that required: (1) reports of all significant chest findings (Free Search), (2) only reports of possible nodules (Nodule Search), or (3) evaluation of particular film locations as nodules (Specified Location). ROC curves from these conditions compared how accurately readers could distinguish between the nodule and normal "test locations," and between the films that did and did not contain nodules. In replication of previous results for heterogeneous chest findings, detection accuracy was superior when readers had to search the films. Each reader's distinctions between the nodule and normal test locations became considerably less accurate when these locations were prespecified for explicit evaluation. When asked to search only for pulmonary nodules, most readers substantially increased their false reports of nodules at each level of confidence, with little improvement in their (already high) true-detection rates. Searching for nodules increased both the true-detection and false-detection rates for two readers, who simply appeared to relax a strong bias against reporting nodules in the initial Free-Search situation.     

Digital synthesis of lung nodules

Studies evaluating observer accuracy and visual perception of pulmonary nodules usually are based upon test films obtained from clinical practice in patients with proven pulmonary nodules. Unfortunately, such nodules do not always occur in the optimal size and location to facilitate testing. Such studies would be enhanced by the ability to place nodules of desired size and location on chest radiographs. This report describes a method of placing a computer-generated (synthesized) nodule on a digitized chest radiograph. To demonstrate the similarity of these synthesized nodules to real nodules, each digitized radiograph with a computer-generated nodule was paired with a digitized chest radiograph of a patient with a clinically proven pulmonary nodule. A total of 22 pairs of chest radiographs were then shown to 13 radiologists, who were asked to distinguish the synthesized nodule from the real nodule. With this two alternative forced-choice test, the radiologists were only able to distinguish the synthesized nodule in 51% of the cases, strongly suggesting that computer generated nodules may be used to simulate real pulmonary nodules in future tests of nodule detection.     

Pulmonary nodules: detection in 1 and 2 cm full lung linear tomography

Pulmonary nodule detection was evaluated in full lung linear tomography at 1 and 2 cm intervals. Three radiologists independently reviewed 1 and 2 tomograms on 26 patients with 39 pulmonary nodules. Decisions made in each case included: (1) no nodule; (2) definite nodule(s); and (3) suspect nodule(s). The presence of nodules was determined by surgery, radiographic follow-up, or observer consensus. A significantly greater number of nodules was detected by all reviewers on the 1 cm tomograms. Of the 39 nodules, 72%-97% were detected as definite and 82%-100% were identified as definite or suspect. Factors relating to nodule detectability and observer performance are discussed. It is recommended that full lung linear tomography be performed at 1 cm intervals.     

Subtle lung nodules: influence of local anatomic variations on detection

PURPOSE: To assess the influence of local anatomic noise on the detection of subtle lung nodules depicted on chest radiographs. MATERIALS AND METHODS: Six 8 x 8-cm lung regions were extracted from digital chest radiographs obtained in healthy subjects. Simulated nodules emulating the radiographic characteristics of subtle tissue-equivalent lesions 3.2-6.4 mm in diameter (equivalent to 0.1-0.4 mm in contrast-diameter product [CD]) were added to the images. On multiple renditions of each image, nodules were inserted at slightly different locations within 6 mm of the center; this process allowed different local background patterns to overlie the nodules. An observer detection study involving 15 experienced radiologists was performed. The authors performed analysis of variance and pairwise t test analyses to determine variations in nodule detectability related to nodule location and size on each image. RESULTS: Results indicated a strong correlation between nodule size and observer detection score and significant variation in nodule detectability as a function of location. Changes in nodule position caused observer score variations that were equivalent to the variation caused by an up to 185% change in nodule CD (78% average over all six images), an up to 68% change in diameter (32% average), and an up to 28% change in area under the receiver operating characteristic curve (Az) (14% average). CONCLUSION: Local anatomic variations surrounding and overlying a subtle lung nodule on a chest radiograph that are created by the projection of anatomic features in the thorax, such as ribs and pulmonary vessels, can greatly influence the detection of nodules, altering the Az by as much as 28%.     

CT screening for lung cancer: frequency and significance of part-solid and nonsolid nodules

OBJECTIVE: In the Early Lung Cancer Action Project (ELCAP), we found not only solid but also part-solid and nonsolid nodules in patients at both baseline and repeat CT screening for lung cancer. We report the frequency and significance of part-solid and nonsolid nodules in comparison with solid nodules. MATERIALS AND METHODS: We reviewed all instances of a positive finding in patients at baseline (from one to six noncalcified nodules) and annual repeat screenings (from one to six newly detected noncalcified nodules with interim growth) to classify each of the nodules as solid, part-solid, or nonsolid. We defined a solid nodule as a nodule that completely obscures the entire lung parenchyma within it. Part-solid nodules are those having sections that are solid in this sense, and nonsolid nodules are those with no solid parts. Chi-square statistics were used to test for differences in the malignancy rates. RESULTS: Among the 233 instances of positive results at baseline screening, 44 (19%) involved a part-solid or nonsolid largest nodule (16 part-solid and 28 nonsolid). Among these 44 cases of positive findings, malignancy was diagnosed in 15 (34%) as opposed to a 7% malignancy rate for solid nodules (p = 0.000001). The malignancy rate for part-solid nodules was 63% (10/16), and the rate for nonsolid nodules was 18% (5/28). Even after standardizing for nodule size, the malignancy rate was significantly higher for part-solid nodules than for either solid ones (p = 0.004) or nonsolid ones (p = 0.03). The malignancy type in the part-solid or nonsolid nodules was predominantly bronchioloalveolar carcinoma or adenocarcinoma with bronchioloalveolar features, contrasting with other subtypes of adenocarcinoma found in the solid nodules (p = 0.0001). At annual repeat screenings, only 30 instances of positive test results have been obtained; seven of these involved part-solid or nonsolid nodules. CONCLUSION: In CT screening for lung cancer, the detected nodule commonly is either only part-solid or nonsolid, but such a nodule is more likely to be malignant than a solid one, even when nodule size is taken into account.     

Incremental benefit of maximum-intensity-projection images on observer detection of small pulmonary nodules revealed by multidetector CT

OBJECTIVE: Our purpose was to assess the incremental effect of maximum-intensity-projection (MIP) image processing on the ability of various observers to detect small (<1 cm in diameter) central and peripheral lung nodules revealed by multidetector CT. MATERIALS AND METHODS: We retrospectively identified 25 patients with metastatic disease, each having from two to nine nodules that were 3-9 mm in diameter. Two senior and three junior reviewers interpreted all images on a workstation. The observers first reviewed axial images (3.75-mm collimation, 3-mm reconstruction interval, multidetector acquisition) in cine and sequential fashion and recorded the size, lobe, and central or peripheral (within 1 cm of the edge of lung) location of each nodule. MIP images (10-mm slab, 8-mm interval) were then reviewed, and additional nodules detected were recorded. Final counts were established by consensus. RESULTS: The reviewers found 122 nodules (71 peripheral, 51 central) in the 25 patients. The addition of MIP slabs significantly enhanced reviewer detection of central nodules (p < 0.001) and junior reviewer detection of peripheral nodules (p < 0.001). MIP slabs also reduced the effects of reviewer experience, particularly for peripheral nodules. CONCLUSION: MIP processing reduces the number of overlooked small nodules, particularly in the central lung. Observer nodule detection remains imperfect even when lesions are clearly depicted on images.     

Differential uptake of TI-201 by small-cell lung cancer in a patient with pneumoconiosis-related pulmonary nodules.

A 68-year-old man with pneumoconiosis was thought to have small-cell lung cancer based on the results of a biopsy of a bone tumor. Three pulmonary nodules were observed on a chest radiograph. Compared with a chest radiograph taken 4 months earlier, one of the nodules had grown. It was difficult to differentiate this nodule from pneumoconiosis-related benign pulmonary nodules from the appearance on the chest radiograph and CT. Ga-67 scintigraphy and TI-201 lung SPECT were performed to characterize these nodules. TI-201 SPECT showed differential high uptake in the enlarged nodule, whereas Ga-67 scintigraphy showed equally intense uptake in all these nodules. Transbronchial biopsy of the nodule that showed high TI-201 uptake revealed cancer cell nests against a background of interstitial fibrosis. The pathologic diagnosis was small-cell lung cancer that had developed in lung scar tissue. This case suggests the utility of TI-201 in scintigraphic assessments of pneumoconiosis-related pulmonary nodules when lung cancer is suspected.     

Influence of monitor luminance change on observer performance for detection of abnormalities depicted on chest radiographs

RATIONALE AND OBJECTIVES: To investigate how changes in luminance affect the detection accuracy of radiologists viewing chest radiograph images on high-resolution CRT monitors. MATERIALS AND METHODS: Thirteen radiologists performed a detection task for 11 chest radiograph images with simulated nodules on a monitor with 11 luminance conditions (the maximum luminance ranges from 157.4-369.0 candela/m2) simulating CRT degraded by long-term usage, under the ambient illumination of 200 lux; the observation order was always from the darkest to the brightest. RESULTS: There was a statistically reliable effect of the 11 monitor display conditions on the detection of nodules (P < 0.001). In the conditions in which the maximum luminance of the CRT was 60.7% or below that of the standard display luminance, the correctly detected nodule number reliably deteriorated. CONCLUSIONS: The luminance change in CRT monitor display under long-term usage will have a detrimental effect on nodule detection performance in chest radiograph images.     

Hypothyroidism presenting as a hot pertechnetate nodule

The authors report an uncommon finding of hot nodule on Tc-99m sodium pertechnetate thyroid scan in three patients with hypothyroidism. Data indicate that hypothyroidism is secondary to Hashimoto's disease (HD). There was a concordant aspect on I-131 scan in two; a nodular discrepancy (cold nodule with I-131) was associated with the highest microsomal antibodies titer. The findings of thyroid scan and ultrasonographic findings indicate that hot nodules may be observed either on initial or advanced stages of HD. Color flow Doppler sonography, showed an absence of internal increase of vascularization. These data suggest that the observed hot nodules correspond to localized hyperplasia of the less diseased portions secondary to chronic stimulation by TSH.     

Differentiation of benign from malignant pulmonary nodules with digitized chest radiographs

To assess whether it is possible to distinguish benign from malignant solitary pulmonary nodules with digital techniques, a retrospective study of 68 patients with proved solitary nodules was performed. The conventional chest radiograph for each patient was digitized to 2,048 X 2,048 X 12 bits, and changes in the optical density within the nodule were analyzed. A number (the corrected gradient number) was then generated that reflected this variation. Striking differences were noted between 26 malignant nodules and 21 calcified granulomas. The technique was then applied to 21 benign nodules that had initially required thoracotomy or further study for diagnosis. In nine of these 21 patients (43%), the corrected gradient number allowed correct classification as a benign lesion.     

Computed tomography findings of Caplan syndrome

We report a case of Caplan syndrome complicated with tuberculosis, which was clinically followed up for 18 years and underwent autopsy. Initial chest radiograph showed 2 large nodules against the background of smaller pneumoconiotic nodules. One of the large nodules showed cavitation during follow-up. Computed tomography (CT) was helpful in identifying calcification in another large nodule. Autopsy confirmed the 2 large nodules as burned-out rheumatoid nodules and revealed additional rheumatoid nodules that were indistinguishable from silicotic nodules by CT.     

Personal computer-based interpretation experiment system for digital chest images]

We have developed a system of nodule detection interpretation experiment on personal computers. This system is composed of three subsystems: practice, experiment and check modes. In the practice and experiment modes, chest radiographic images, each with or without a nodule, are shown in a random order on the monitor. The reader is then asked to point a location of nodule and to give a confidence rating. In the check mode, a subsystem shows locations of the real nodules and false positive foci on a figure of a chest radiograph. It also shows receiver operating characteristics of each reader. This system can precisely and easily perform an interpretation experiment. Then reader performance in detection of nodules can be accurately and promptly evaluated. This system, therefore, is very useful to perform a large-scale interpretation experiment in a constant reading condition.     

Pulmonary malignancy in silicosis: factors associated with radiographic detection

The aim was to assess radiographic features of pulmonary malignancies in silicosis and to reveal confounding factors in their detection. A total of 501 silicosis patients were followed up between 1982 and 2003. Sixty pulmonary malignancies were pathologically confirmed in 54 (10.8%) patients. Two radiologists reviewed serial radiographs of these patients to determine radiographic features of tumor (size, margin, nodule or consolidation, localization, overlying structures) and silicosis (profusion of pneumoconiotic opacities, progressive massive fibrosis (PMF), hilar lymphadenopathy). Eleven tumors were radiographically negative. Forty-nine tumors were retrospectively visible with radiograph. Of these, 15 tumors were clinically detected with radiograph, but 25 were missed. The remaining nine tumors became radiographically positive after positive sputum cytology. There were no differences between missed and detected nodules in terms of radiographic findings. The mean tumor size was 30mm (range: 15-90mm) and was significantly larger in patients with PMF or hilar lymphadenopathy than in those without (35mm vs. 24mm, p=0.006; 33mm vs. 24mm, p=0.038, respectively). This was correlated with background profusion of small pneumoconiotic opacities (r=0.433, p=0.024). Retrospective reading tests by three radiologists showed correct localization of tumor in 75%, however, the correct diagnosis with a high confidence was reached in only 54%. In conclusion, radiographic detection of malignancy in silicosis proved a difficult task and no single radiographic finding was found to be associated with missing the tumor. The presence of PMF, hilar lymphadenopathy and profusion of small pneumoconiotic nodules affected tumor size at detection.     

Searching for nodules: what features attract attention and influence detection?

RATIONALE AND OBJECTIVES: The goal of the study was to determine whether there are certain physical features of pulmonary nodules that attract visual attention and contribute to increased recognition and detection by observers. MATERIALS AND METHODS: A series of posteroanterior chest images with solitary pulmonary nodules were searched by six radiologists as their eye-position was recorded. The signal-to-noise ratio, size, conspicuity, location, and calcification status were measured for each nodule. Dwell parameters were correlated with nodule features and related to detection rates. RESULTS: Only nodule size (F = 5.08, P = .0254) and conspicuity (F = 4.625, P = .0329) influenced total dwell time on nodules, with larger, more conspicuous nodules receiving less visual attention than smaller, less conspicuous nodules. All nodule features examined influenced overall detection performance (P < .05) even though most did not influence visual search and attention. CONCLUSION: Individual nodule features do not attract attention as measured by "first hit" fixation data, but certain features do tend to hold attention once the nodule has been fixated. The combination of all features influences whether or not it is detected.     

Performance of computer-aided detection of pulmonary nodules in low-dose CT: comparison with double reading by nodule volume

Objective

To evaluate performance of computer-aided detection (CAD) beyond double reading for pulmonary nodules on low-dose computed tomography (CT) by nodule volume.

Methods

A total of 400 low-dose chest CT examinations were randomly selected from the NELSON lung cancer screening trial. CTs were evaluated by two independent readers and processed by CAD. A total of 1,667 findings marked by readers and/or CAD were evaluated by a consensus panel of expert chest radiologists. Performance was evaluated by calculating sensitivity of pulmonary nodule detection and number of false positives, by nodule characteristics and volume.

Results

According to the screening protocol, 90.9?% of the findings could be excluded from further evaluation, 49.2?% being small nodules (less than 50?mm³). Excluding small nodules reduced false-positive detections by CAD from 3.7 to 1.9 per examination. Of 151 findings that needed further evaluation, 33 (21.9?%) were detected by CAD only, one of them being diagnosed as lung cancer the following year. The sensitivity of nodule detection was 78.1?% for double reading and 96.7?% for CAD. A total of 69.7?% of nodules undetected by readers were attached nodules of which 78.3?% were vessel-attached.

Conclusions

CAD is valuable in lung cancer screening to improve sensitivity of pulmonary nodule detection beyond double reading, at a low false-positive rate when excluding small nodules.

Key Points

? Computer-aided detection (CAD) has known advantages for computed tomography (CT). ? Combined CAD/nodule size cut-off parameters assist CT lung cancer screening. ? This combination improves the sensitivity of pulmonary nodule detection by CT. ? It increases the positive predictive value for cancer detection.     

Pulmonary cavitary nodules on computed tomography: differentiation of malignancy and benignancy

OBJECTIVE: To establish computed tomographic findings that enable accurate differentiation between malignant and benign cavitary lung nodules. METHODS: Computed tomographic scans from 39 patients with malignant cavitary nodules and from 39 patients with benign cavitary nodules were independently assessed by 2 observers. They recorded the computed tomographic findings of both types of cavitary nodules and surrounding pulmonary parenchyma. The computed tomographic findings were then compared using chi test. RESULTS: The notch was found in 29% of benign cavitary nodule cases and in 54% of malignant cavitary nodule cases (P < 0.01). An irregular internal wall was found in 26% of benign nodules and in 49% of malignant nodule cases (P < 0.01). A linear margin (P < 0.01), satellite nodule presence (P < 0.01), bronchial wall thickening (P < 0.05), consolidation (P < 0.05), and ground-glass attenuation (P < 0.01) were significantly more frequent in benign cavitary nodules than in malignant ones. CONCLUSIONS: Although the computed tomographic findings of benign and malignant cavitary nodules overlap, some computed tomographic findings are useful for differentiating cavitary nodules.     

<Superscript>18</Superscript>F-FDG-PET/CT as an indicator for resection of pulmonary epithelioid hemangioendothelioma

A 60-year-old man with a 7-year history of multiple pulmonary nodules presented to our hospital because the nodules were seen to have increased in size on review of films on a regular medical checkup 1 week earlier. Computed tomography (CT) revealed multiple pulmonary nodules with calcification in the lungs. The largest nodule measuring 2.5 cm in the maximum dimension was lobulated and ill-defined. The patient underwent 18F-fluorodeoxyglucose positron emission tomography/CT (18F-FDG-PET/CT) to evaluate the multiple nodules and to search for a primary lesion. 18F-FDG-PET/CT revealed increased uptake in only two nodules with a standardized uptake value of 4.61 and 2.10, respectively. The two foci with increased 18F-FDG uptake were resected and pathologically proven to be pulmonary epithelioid hemangioendothelioma (PEH). PEH can transform into malignancy with metastasis. An 18F-FDG-PET/CT finding may be an indicator to decide on PEH resection.     

Searching for lung nodules. Visual dwell indicates locations of false-positive and false-negative decisions

Eye position recordings made while radiologists searched chest images for lung nodules showed that regions falsely reported positive or suspicious received prolonged visual attention. Correlation of regional fixation dwell time with independent ratings of image features indicated that more than 90% of false-positive decisions were caused by some perturbation in the image that aroused the suspicion of the viewer. The remainder apparently arose from within the viewer. Most missed nodules (false-negative reports) also received prolonged visual attention, implying an active decision not to perceive a nodule. The data are interpreted to show that roughly one task-related decision is made during each second of scanning a radiograph. This departs from the central assumption of the traditional signal-detection model based upon one decision per image.     

Bronchiolitis obliterans organising pneumonia simulating bronchial carcinoma

Idiopathic bronchiolitis obliterans organising pneumonia (BOOP) is an uncommon but well-recognised condition that usually presents radiologically as bilateral multifocal patchy areas of consolidation on the chest radiograph and on computed tomography (CT). Five cases are described in which the presenting feature was that of a solitary pulmonary nodule. Four of these nodules showed evidence of cavitation and three patients presented with haemoptysis. In all cases the appearances closely resembled bronchial carcinoma. Received 22 December 1997; Accepted 23 January 1998