Characteristics of small lung cancers invisible on conventional chest radiography and detected by population based screening using spiral CT

State of the Art: Lung Cancer Staging Using Updated Imaging Modalities

Lung cancer is among the most common mortality causes worldwide. This scientific article is a comprehensive review of current knowledge regarding screening, subtyping, imaging, staging, and management of treatment response for lung cancer. The traditional imaging modality for screening and initial lung cancer diagnosis is computed tomography (CT). Recently, a dual-energy CT was proven to enhance the categorization of variable pulmonary lesions. The National Comprehensive Cancer Network (NCCN) recommends usage of fluorodeoxyglucose positron emission tomography (FDG PET) in concert with CT to properly stage lung cancer and to prevent fruitless thoracotomies. Diffusion MR is an alternative to FDG PET/CT that is radiation-free and has a comparable diagnostic performance. For response evaluation after treatment, FDG PET/CT is a potent modality which predicts survival better than CT. Updated knowledge of lung cancer genomic abnormalities and treatment regimens helps to improve the radiologists’ skills. Incorporating the radiologic experience is crucial for precise diagnosis, therapy planning, and surveillance of lung cancer.

Computer-Aided Detection of Seven Chest Pathologies on Standard Posteroanterior Chest X-Rays Compared to Radiologists Reading Dual-Energy Subtracted Radiographs

RATIONALE AND OBJECTIVES

Retrospective performance evaluation of a computer-aided detection (CAD) system on standard posteroanterior (PA) chest radiographs (PA-CXR) in detection of pulmonary nodules, infectious consolidation, pneumothorax, pleural effusion, aortic calcification, cardiomegaly and rib fractures compared to radiologists analyzing PA-CXR including dual-energy subtraction radiography (further termed as DESR).

MATERIALS AND METHODS

PA-CXR/DESR images of 197 patients were included. All patients underwent chest CT (gold standard) within a short interval (mean 28 hours). All images were evaluated by three blinded readers for the presence of pulmonary nodules, infectious consolidation, pneumothorax, pleural effusion, aortic calcification, cardiomegaly, and rib fractures. Meanwhile PA-CXR were analyzed by a CAD software. CAD results were compared to the majority result of the three readers. Sensitivity and specificity were calculated. McNemar's test was applied to test for significant differences. Interobserver agreement was defined using Cohen's kappa (κ).

RESULTS

Sensitivity of the CAD software was significantly higher (p < 0.05) for detection of infectious consolidation and pulmonary nodules (67.9% vs 26.8% and 54% vs 35.6%, respectively; p < 0.001) compared to radiologists analyzing DESR images. For the residual evaluated pathologies no statistical significant differences could be found. Overall, mean inter observer agreement between the three radiologists was moderate (k = 0.534). The best interobserver agreement could be reached for pneumothorax (k = 0.708) and pleural effusion (k = 0.699), while the worst was obtained for rib fractures (k = 0.412).

CONCLUSION

The CAD system has the potential to improve the detection of infectious consolidation and pulmonary nodules on CXR images.

Lung cancer screening: who pays? Who receives? The European perspectives

Lung cancer is the leading cause of cancer-related death worldwide, and its early detection is critical to achieving a curative treatment and to reducing mortality. Low-dose computed tomography (LDCT) is a highly sensitive technique for detecting noninvasive small lung tumors in high-risk populations. We here analyze the current status of lung cancer screening (LCS) from a European point of view. With economic burden of health care in most European countries resting on the state, it is important to reduce costs of screening and improve its effectiveness. Current cost-effectiveness analyses on LCS have indicated a favorable economic profile. The most recently published analysis reported an incremental cost-effectiveness ratio (ICER) of €3,297 per 1 life-year gained adjusted for the quality of life (QALY) and €2,944 per life-year gained, demonstrating a 90% probability of ICER being below €15,000 and a 98.1% probability of being below €25,000. Different risk models have been used to identify the target population; among these, the PLCOM2012 in particular allows for the selection of the population to be screened with high sensitivity. Risk models should also be employed to define screening intervals, which can reduce the general number of LDCT scans after the baseline round. Future perspectives of screening in a European scenario are related to the will of the policy makers to implement policy on a large scale and to improve the effectiveness of a broad screening of smoking-related disease, including cardiovascular prevention, by measuring coronary calcium score on LDCT. The employment of artificial intelligence (AI) in imaging interpretation, the use of liquid biopsies for the characterization of CT-detected undetermined nodules, and less invasive, personalized surgical treatments, will improve the effectiveness of LCS.

Effects of toner-handling work on respiratory function, chest X-ray findings, and biomarkers of inflammation, allergy, and oxidative stress: a 10-year prospective Japanese cohort study

Background

Exposure to toner, a substance used in photocopiers and printers, has been associated with siderosilicosis and other adverse effects. However, these findings are limited, and there is insufficient evidence on the long-term effects of toner exposure. Using longitudinal analysis, this study aimed to examine the effects of work involving toner exposure on the respiratory system over time.

Methods

We conducted a prospective cohort study in a Japanese toner and copier manufacturing enterprise between 2003 and 2013. The cohort included a total of 1468 workers, which comprised 887 toner-handling workers and 581 non-toner-handling workers. We subdivided the toner-handling workers into two groups according to the toner exposure concentration, based on the baseline survey in 2003. We compared the chest X-ray results, respiratory function indicators, and serum and urinary biomarkers of inflammation, allergy, and oxidative stress among the three groups: high-concentration toner exposure group, low-concentration toner exposure group, and non-toner-handling group. To consider the effects of individual differences on the longitudinal data, we used a linear mixed model.

Results

Similar chest X-ray results, the biomarkers, and most of the respiratory function indicators were found in the non-toner-handling and toner-handling groups. There were no significant yearly changes in the percentage of vital capacity (%VC) in the high-concentration toner exposure group, while there was a significant yearly increase in %VC in the low-concentration toner exposure group and non-toner-handling group. The yearly change in each group was as follows: high-concentration toner exposure group, − 0.11% (95% confidence interval [CI], − 0.29 to 0.08; P = 0.250); low-concentration toner exposure group, 0.13% (95% CI, 0.09–0.17; P < 0.001); and non-toner-handling group, 0.15% (95% CI, 0.01–0.20; P < 0.001).

Conclusions

In our 10-year prospective study, toner-handling work was not associated with the deterioration of respiratory function and an increase in biomarker values for inflammation, allergy, and oxidative stress. This finding suggests that toner-handling work is irrelevant to the onset of respiratory disease and has minimal adverse effects on the respiratory system under a well-managed work environment.

Supplementary Information

Supplementary information accompanies this paper at10.1186/s12890-020-01320-6.

Imaging patterns of early stage lung cancer for the thoracic surgeon

In the modern era, thoracic surgeons are experiencing an increase interest in imaging patterns of early stage lung cancer due to the introduction of the ground glass opacity in clinical practice, and for the necessity to an accurate cancer localization to perform the appropriate type of resection. In this brief review we analyze the latest news regarding imaging patterns of early pulmonary nodules with special emphasis to ground glass opacity.

Segmentation and suppression of pulmonary vessels in low-dose chest CT scans

PURPOSE

The suppression of pulmonary vessels in chest computed tomography (CT) images can enhance the conspicuity of lung nodules, thereby improving the detection rate of early lung cancer. This study aimed to develop two key techniques in vessel suppression, that is, segmentation and removal of pulmonary vessels while preserving the nodules.

METHODS

Pulmonary vessel segmentation and removal methods in CT images were developed. The vessel segmentation method used a framework of two cascaded convolutional neural networks (CNNs). A bi-class segmentation network was utilized in the first step to extract high-intensity structures, including both vessels and nonvascular tissues such as nodules. A tri-class segmentation network was employed in the second step to distinguish the vessels from nonvascular tissues (mainly nodules) and the lung parenchyma. In the vessel removal method, the voxels in the segmented vessels were replaced with randomly selected voxels from the surrounding lung parenchyma. The dataset in this study comprised 50 three-dimensional (3D) low-dose chest CT images. The labels for vessel and nodule segmentation were annotated with a semi automatic approach. The two cascaded networks for pulmonary vessel segmentation were trained with CT images of 40 cases and tested with CT images of ten cases. Pulmonary vessels were removed from the ten testing scans based on the predicted segmentation results. In addition to qualitative evaluation to the effects of segmentation and removal, the segmentation results were quantitatively evaluated using Dice coefficient (DICE), Jaccard index (JAC), and volumetric similarity (VS) and the removal results were evaluated using contrast-to-noise ratio (CNR).

RESULTS

In the first step of vessel segmentation, the mean DICE, JAC, and VS for high-intensity tissues, including both vessels and nodules, were 0.943, 0.893, and 0.991, respectively. In the second step, all the nodules were separated from the vessels, and the mean DICE, JAC, and VS for the vessels were 0.941, 0.890, and 0.991, respectively. After vessel removal, the mean CNR for nodules was improved from 4.23 (6.26 dB) to 6.95 (8.42 dB).

CONCLUSIONS

Quantitative and qualitative evaluations demonstrated that the proposed method achieved a high accuracy for pulmonary vessel segmentation and a good effect on pulmonary vessel suppression.

Missed lung cancer: when, where, and why?

Missed lung cancer is a source of concern among radiologists and an important medicolegal challenge. In 90% of the cases, errors in diagnosis of lung cancer occur on chest radiographs. It may be challenging for radiologists to distinguish a lung lesion from bones, pulmonary vessels, mediastinal structures, and other complex anatomical structures on chest radiographs. Nevertheless, lung cancer can also be overlooked on computed tomography (CT) scans, regardless of the context, either if a clinical or radiologic suspect exists or for other reasons. Awareness of the possible causes of overlooking a pulmonary lesion can give radiologists a chance to reduce the occurrence of this eventuality. Various factors contribute to a misdiagnosis of lung cancer on chest radiographs and on CT, often very similar in nature to each other. Observer error is the most significant one and comprises scanning error, recognition error, decision-making error, and satisfaction of search. Tumor characteristics such as lesion size, conspicuity, and location are also crucial in this context. Even technical aspects can contribute to the probability of skipping lung cancer, including image quality and patient positioning and movement. Albeit it is hard to remove missed lung cancer completely, strategies to reduce observer error and methods to improve technique and automated detection may be valuable in reducing its likelihood.

ROC Curve for Extremely Subtle Lung Nodules on Chest Radiographs Confirmed by CT Scan

RATIONALE AND OBJECTIVES

The aim of the present study was to test the hypothesis that when a radiologist does not perceive an abnormality in images that contain either extremely subtle abnormalities or no abnormalities, the radiologist cannot distinguish these two types of images and the receiver operating characteristic (ROC) curve reflects that performance.

MATERIALS AND METHODS

This retrospective study was conducted with approval of our institutional review board. Four general radiologists participated in an observer performance study of 100 chest images, each of which had a 5 × 5 cm region of interest (ROI) drawn (50 containing a lung nodule, and 50 did not, based on computed tomography [CT] confirmation). About half of the lung nodules were extremely subtle. The readers reported their confidence that a nodule was present within the ROI, from which empirical and maximum-likelihood "proper" binormal and conventional binormal ROC curves were estimated. The readers also reported whether they saw an abnormality that could be a nodule within the ROI.

RESULTS

Empirical ROC curves deviated from typical ROC-curve shapes, and a portion of the curve leading to the northeast corner of the ROC space had relatively steep and constant slopes. The readers reported not seeing anything suggestive of a lung nodule in this portion of the ROC curve, which also corresponded to cases that either contained extremely subtle nodules or normal cases. The average area under the ROC curves (mean ± standard deviation) was 0.66 ± 0.02 for proper binormal, 0.62 ± 0.02 for conventional binormal, and 0.60 ± 0.03 for trapezoidal ROC curves.

CONCLUSIONS

When a radiologist does not perceive an abnormality in images that contain either extremely subtle abnormalities or no abnormalities, the ROC curve (or a portion thereof) is characterized by a straight line, which is not consistent with conventional ROC theories.

The challenge of small lung nodules identified in CT screening: can biomarkers assist diagnosis?

Various biomarkers have been developed as noninvasive tests to indicate the presence of lung cancer in asymptomatic persons, and in particular to provide evidence as to whether indeterminate lung nodules detected by screening are malignant. We performed an overview of the range of biomarkers reported in the literature and described those that can complement low-dose computed tomography screening. Several have promising sensitivity and specificity. However to our knowledge, only three techniques have reached the prospective screening phase (phase 4) of the five-phase biomarker development process. Two miRNA signatures (the miR-Test for serum and the miRNA signature classifier test for plasma) are being assessed in prospective screening trials, as is the EarlyCDT-Lung test based on autoantibodies. All will need to undergo prospective studies to determine their ability to improve outcomes before they can become an established adjunct to lung cancer control strategies.

Lung cancer screening: the European perspective

European studies have contributed significantly to the understanding of lung cancer screening. Smoking within screening, quality of life, nodule management, minimally invasive treatments, cancer prevention programs, and risk models have been extensively investigated by European groups. Mortality data from European screening studies have not been encouraging so far, but long-term results of the NELSON study are eagerly awaited. Investigations on molecular markers of lung cancer are ongoing in Europe; preliminary results suggest they may become an important screening tool in the future.

Prevalence and variables associated with solitary pulmonary nodules in a routine clinic-based population: a cross-sectional study

Objective

To determine the prevalence of solitary pulmonary nodules (SPNs) in chest radiology studies and patient’s features associated with malignancy in a non-high-risk clinical population.

Methods

Patients ≥35 years were referred for thoracic imaging in two hospitals (2010-2011). Eight radiologists determined the presence and characteristics of SPN. Selected variables were collected from radiological register and medical records. Observer agreement in the diagnosis of SPN was assessed.

Results

25,529 patients were included: 23,102 (90.5 %) underwent chest radiograph and 2,497 (9.5 %) a CT. The prevalence of SPN was 2.1 % (95 % CI 1.9 – 2.3) in radiographs and 17.0 % (95 % CI 15.5 – 18.5) in CT. In patients undergoing chest radiograph, detection of SPN with an irregular border was more frequent among smokers. In patients who had a CT, larger SPNs appeared to be associated with 60 years of age or over, diagnosis of a respiratory illness, or male gender. In addition, an irregular border was also more common among men.

Conclusions

The prevalence of SPNs detected by both radiograph and CT was lower than that shown in screening studies. Patient characteristics such as age, sex, respiratory disease, or smoking habit were associated with nodule characteristics that are known to be related with malignancy.

Key Points

• There is a lower SPN prevalence in the clinical population than in screening studies.

• SPN prevalence is associated with some patient characteristics: sex, age, imaging test.

• Nodule characteristics related to malignancy were associated with some patient characteristics.

Flat-panel detector computed tomography imaging: observer performance in detecting pulmonary nodules in comparison with conventional chest radiography and multidetector computed tomography

PURPOSE

The aim of this study was to compare the detectability of lung nodules on images obtained with a flat-panel detector computed tomography (FPD-CT) system and by chest radiographs (CXRs) using receiver-operating characteristic (ROC) analysis.

MATERIALS AND METHODS

FPD-CT was conducted with the patients in the sitting position. For the CXR study, the patients stood erect. Our study population consisted of 26 individuals ranging in age from 50 to 83 years. The reference standard was based on the interpretations obtained by consensus of 2 radiologists on multidetector CT images for the presence or absence of nodules. Four other radiologists independently assessed and recorded the absence or presence of lung nodules and their location on FPD-CT and CXR images. ROC analysis was used to evaluate lung nodule detectability by both imaging modalities.

RESULTS

Two radiologists identified 34 nodules whose diameter was 5 to 42 mm (mean, 19.3 mm) in 23 of the 26 study participants on the multidetector CT images. Overall, analysis of variance for ROC analysis showed that FPD-CT was significantly better in detecting nodules than CXR (P=0.02). The estimated mean Az value was 0.9818±0.0083 with FPD-CT and 0.7610±0.0908 with CXR. The sensitivity for nodule detection on FPD-CT and CXR images was 79.4% and 33.8%, respectively.

CONCLUSION

The detectability of pulmonary nodules was better on images of FPD-CT than on CXRs.

Small peripheral lung adenocarcinoma: CT and histopathologic characteristics and prognostic implications

Since the introduction of computed tomography (CT), detection of small lung cancer, especially small peripheral adenocarcinoma, is common. Recently, the morphological characteristics, including thin-section CT and pathologic findings, and prognosis of small peripheral lung adenocarcinomas have been studied extensively. The radiologic and microscopic findings correlate well with each other and are closely associated with tumour prognosis. Most importantly, some subtypes of small lung adenocarcinomas with specific CT or pathologic features are curable. Therefore, all defining characteristics (CT, pathologic and prognostic) of this kind of tumour should be integrated to improve our understanding, provide guidelines for management and accurately assess its prognosis.

Systematic review of the cost-effectiveness of positron-emission tomography in staging of non--small-cell lung cancer and management of solitary pulmonary nodules

Implementation of positron-emission tomography (PET) is variable depending on jurisdiction in part due to uncertainty about cost-effectiveness. Our objective was to perform a systematic review describing cost-effectiveness of PET in staging of non-small-cell lung cancer (NSCLC) and management of solitary pulmonary nodules (SPN). Systematic literature searches were conducted using separate search strategies for multiple databases. Our validity criteria included measurement of study quality by means of the validated Quality of Health Economic Studies (QHES) instrument. Metrics such as mean PET costs, median average cost savings per patient, incremental cost-effectiveness ratio based on life years saved and quality-adjusted life years were calculated. Eighteen studies met our inclusion criteria with average QHES scores > 75. Studies were primarily based on the national health insurance payer perspective from 10 different countries. Cost-effectiveness was assessed primarily using decision-tree modeling and sensitivity analysis to determine the effects of changing variables on expected cost and life expectancy. After adjusting for currency exchange rates and inflation to 2010 United States dollars, the mean cost of PET was $1478. The cost-effectiveness metrics used in these studies were variable depending on sensitivity and specificity of diagnostic tests used in the models, probability of malignancy, and baseline strategy. Despite observed study heterogeneity, the consensus of these studies conclude that the additional information gained from PET imaging in the staging of NSCLC and diagnosis of SPNs is worth the cost in context of proper medical indications.

Different efficacy of CT screening for lung cancer according to histological type: analysis of Japanese-smoker cases detected using a low-dose CT screen

The efficacy of CT screening for lung cancers is still a controversial issue, although one of the recently publicized large randomized controlled trials of this methodology, the National Lung Screening Trial (NLST), reported a decrease in the lung cancer-specific mortality for heavy smokers. We here performed case-matched comparative analyses, as a retrospective study, of three lung cancer arms detected by CT screen, X-ray screen, and by individual analysis of the clinicopathological features and outcomes in smokers from a symptomatic-prompted group of patients. We also considered the impacts of various potential biases in this cohort. The total study cohort comprised 136 patients in the CT screen group, 263 in the X-ray screen group and 254 in the symptomatic-prompted group. The ratio of stage IA cancers in the CT screen group was 67.7% and the ratio of advanced cases (i.e. stages IIIB+IV) was 12.5%. The percentage of bronchioloalveolar carcinoma (BAC) was 28.7% in the CT screen group. The 5-year survival rates were 82.4% in the CT screen group, 38.0% in the X-ray screen group and 17.8% in the symptomatic-prompted group. CT screening was found to be an independent prognostic factor for lung cancer even when BAC cases were eliminated (HR 0.35, P<0.01). Based on our sub-analysis by individual histological sub-type, CT screen lung cancer cases had a better survival rate than non-screened patients, which included adenocarcinoma, squamous cell carcinoma and large/small cell carcinoma. However, by multi-variant analysis a CT scan would not be expected to reduce the risk of lung cancer mortality in patients with large/small cell carcinoma, although would be expected to reduce the risk of lung cancer death by 80% in cases of both adenocarcinoma and squamous cell carcinoma. In conclusion, our current findings indicate that CT screening for lung cancer is an effective strategy for smokers and that patients with adenocarcinoma and squamous cell carcinoma of all variant histological types may benefit from this test. In this regard, early stage large/small cell carcinomas are insufficiently detected by the existing annual screening system.

Relationship between tumor size and disease stage in non-small cell lung cancer

Background

Whether tumor size and stage distribution are correlated remains controversial. The objective is to assess the relationship between tumor size and disease stage distribution in non-small cell lung cancer (NSCLC).

Methods

We conducted a retrospective analysis of 917 cases of NSCLC that were resected in the Cancer Hospital of Fudan University and Shanghai Sixth Hospital between January 2000 and February 2009. Tumor sizes were grouped into five categories: ≤20 mm, 21 to 30 mm, 31 to 50 mm, 51 to 70 mm and ≥71 mm.

Results

Age and tumor size affected stage distribution: patients 60 years or older had a higher percentage of N0M0 disease than patients younger than 60 years (61.67% vs. 44.85%, p < 0.01). The smaller the tumor, the more likely the disease was N0M0 status (p < 0.05). For tumors ≤20 mm in diameter, the proportion of cases with N0M0 status was 70.79%, compared to 58.88% for 21 to 30 mm, 48.03% for 31 to 50 mm, 47.55% for 51 to 70 mm, 33.33% for ≥71 mm. The mean (± SD) tumor size of cases with N0M0 status was 37.17 ± 21.34 mm, compared to 45.75 ± 23.19 mm for cases with other status.

Conclusions

There is a statistically significant relationship between tumor size and distribution of disease stage of primary NSCLC tumors: the smaller the tumor, the more likely the disease is N0M0 status.

Principles of cancer screening: lessons from history and study design issues

Early detection of cancer has held great promise and intuitive appeal in the medical community for well over a century. Its history developed in tandem with that of the periodic health examination, in which any deviations--subtle or glaring--from a clearly demarcated "normal" were to be rooted out, given the underlying hypothesis that diseases develop along progressive linear paths of increasing abnormalities. This model of disease development drove the logical deduction that early detection, by "breaking the chain" of cancer development, must be of benefit to affected individuals. In the latter half of the 20th century, researchers and guidelines organizations began to explicitly challenge the core assumptions underpinning many clinical practices. A move away from intuitive thinking began with the development of evidence-based medicine. One key method developed to explicitly quantify the overall risk-benefit profile of a given procedure was the analytic framework. The shift away from pure deductive reasoning and reliance on personal observation was driven, in part, by a rising awareness of critical biases in cancer screening that can mislead clinicians, including healthy volunteer bias, length-biased sampling, lead-time bias, and overdiagnosis. A new focus on the net balance of both benefits and harms when determining the overall worth of an intervention also arose: it was recognized that the potential downsides of early detection were frequently overlooked or discounted because screening is performed on basically healthy persons and initially involves relatively noninvasive methods. Although still inconsistently applied to early detection programs, policies, and belief systems in the United States, an evidence-based approach is essential to counteract the misleading--even potentially harmful--allure of intuition and individual observation.

Long-term outcomes of a pilot CT screening for lung cancer

BACKGROUND

Low-dose computed tomography (CT) screening can detect early stage lung cancer in high-risk populations. However, no data on repeated annual screening over more than 5 years are available, and the impact of screening on lung cancer mortality is controversial.

METHODS

We analysed outcomes in high-risk asymptomatic volunteers (smokers and former smokers, >50 years) enrolled in a pilot study over 1 year from June 2000, who received annual low-dose CT for 7 years. Cumulative lung cancer incidence and survival were represented by Kaplan-Meier curves. Standardized incidence and mortality ratios were used to estimate risks relative to the general Italian and US population.

RESULTS

Compliance was 86% at the end of the seventh year in 1035 recruited volunteers (71% men, mean age 58 years). Lung cancer was diagnosed in 54 (5.3%); radical surgery was possible in 48/54 (87%); 39/54 (72%) had stage I disease. Five-year survival was 63% overall, 89% for stage I cases. During 6308 person-years of observation, 47 participants had died versus 75 expected in the Italian general population standardised for age and sex. Fourteen lung cancer deaths were registered versus 27 expected in a standardised US smoker population.

CONCLUSIONS

Seventy percent of screening-diagnosed patients had stage I disease, and the survival of screen-detected cancer patients was high. Lung cancer mortality was favourable compared to age- and sex-matched population of US smokers, suggesting that mortality can be lowered by screening, although larger trials with longer follow-up are necessary to confirm these findings.

HRCT features of small peripheral lung carcinomas detected in a low-dose CT screening program

RATIONALE AND OBJECTIVES

To define high-resolution computed tomography (HRCT) features of lung cancers detected by computed tomography (CT) screening according to histopathology and prognosis.

METHODS AND MATERIALS

Tumor size, CT value, morphology, and tumor volume doubling time (TVDT) were determined for 10 atypical adenomatous hyperplasias (AAH) and 50 lung cancers followed between 1996 and 1998 to 2007.

RESULTS

For the 10 AAHs, the density less than -500 HU in all lesions (mean, -654 HU) and the size was up to 14 mm (mean, 9 mm); all patients remain alive. Focal bronchioloalveolar cell carcinomas (BAC) were denser (mean, -537 HU) than AAH and mostly less dense than -350 HU; all patients remain alive. All 22 adenocarcinomas (ADC) were denser than -450 HU (mean, -186 HU); 6 were problematic and measured >-150HU and >10 mm or had >10 mm of central denser zone (CDZ) (partly solid tumors) or tumor size (solid tumor). Two of four squamous cell carcinomas (SCC) measuring 15 and 10 mm, respectively, were problematic. Two patients with small-cell lung carcinomas (SCLC) measuring 15 and 23 mm, respectively, remain alive. AAH, BAC, ADC, and SCC lesions were in general polygonal in shape. SCLC lesions appeared as round nodules with excrescence. The mean TVDT for AAH, BAC, ADC, SCC, and SCLC was 1278, 557, 466, 212, and 103 days, respectively.

CONCLUSION

The CT features reflected tumor aggressiveness. Non-SCLC lesions of >-150HU and >10 mm (or >-100HU and >10 mm for the solid portion of the tumor) are associated with unfavorable prognosis. Timely interventions should be undertaken before problematic increase in number of cases.

Effect of CAD on radiologists' detection of lung nodules on thoracic CT scans: analysis of an observer performance study by nodule size

RATIONALE AND OBJECTIVES

To retrospectively investigate the effect of a computer-aided detection (CAD) system on radiologists' performance for detecting small pulmonary nodules in computed tomography (CT) examinations, with a panel of expert radiologists serving as the reference standard.

MATERIALS AND METHODS

Institutional review board approval was obtained. Our dataset contained 52 CT examinations collected by the Lung Image Database Consortium, and 33 from our institution. All CTs were read by multiple expert thoracic radiologists to identify the reference standard for detection. Six other thoracic radiologists read the CT examinations first without and then with CAD. Performance was evaluated using free-response receiver operating characteristics (FROC) and the jackknife FROC analysis methods (JAFROC) for nodules above different diameter thresholds.

RESULTS

A total of 241 nodules, ranging in size from 3.0 to 18.6 mm (mean, 5.3 mm) were identified as the reference standard. At diameter thresholds of 3, 4, 5, and 6 mm, the CAD system had a sensitivity of 54%, 64%, 68%, and 76%, respectively, with an average of 5.6 false positives (FPs) per scan. Without CAD, the average figures of merit (FOMs) for the six radiologists, obtained from JAFROC analysis, were 0.661, 0.729, 0.793, and 0.838 for the same nodule diameter thresholds, respectively. With CAD, the corresponding average FOMs improved to 0.705, 0.763, 0.810, and 0.862, respectively. The improvement achieved statistical significance for nodules at the 3 and 4 mm thresholds (P = .002 and .020, respectively), and did not achieve significance at 5 and 6 mm (P = .18 and .13, respectively). At a nodule diameter threshold of 3 mm, the radiologists' average sensitivity and FP rate were 0.56 and 0.67, respectively, without CAD, and 0.67 and 0.78 with CAD.

CONCLUSION

CAD improves thoracic radiologists' performance for detecting pulmonary nodules smaller than 5 mm on CT examinations, which are often overlooked by visual inspection alone.

Enhanced CT images by the wavelet transform improving diagnostic accuracy of chest nodules

The objective of this study was to compare the diagnostic accuracy in the interpretation of chest nodules using original CT images versus enhanced CT images based on the wavelet transform. The CT images of 118 patients with cancers and 60 with benign nodules were used in this study. All images were enhanced through an algorithm based on the wavelet transform. Two experienced radiologists interpreted all the images in two reading sessions. The reading sessions were separated by a minimum of 1 month in order to minimize the effect of observer's recall. The Mann-Whitney U nonparametric test was used to analyze the interpretation results between original and enhanced images. The Kruskal-Wallis H nonparametric test of K independent samples was used to investigate the related factors which could affect the diagnostic accuracy of observers. The area under the ROC curves for the original and enhanced images was 0.681 and 0.736, respectively. There is significant difference in diagnosing the malignant nodules between the original and enhanced images (z = 7.122, P < 0.001), whereas there is no significant difference in diagnosing the benign nodules (z = 0.894, P = 0.371). The results showed that there is significant difference between original and enhancement images when the size of nodules was larger than 2 cm (Z = -2.509, P = 0.012, indicating the size of the nodules is a critical evaluating factor of the diagnostic accuracy of observers). This study indicated that the image enhancement based on wavelet transform could improve the diagnostic accuracy of radiologists for the malignant chest nodules.

A novel multithreshold method for nodule detection in lung CT

Multislice computed tomography (MSCT) is a valuable tool for lung cancer detection, thanks to its ability to identify noncalcified nodules of small size (from about 3 mm). Due to the large number of images generated by MSCT, there is much interest in developing computer-aided detection (CAD) systems that could assist radiologists in the lung nodule detection task. A complete multistage CAD system, including lung boundary segmentation, regions of interest (ROIs) selection, feature extraction, and false positive reduction is presented. The selection of ROIs is based on a multithreshold surface-triangulation approach. Surface triangulation is performed at different threshold values, varying from a minimum to a maximum value in a wide range. At a given threshold value, a ROI is defined as the volume inside a connected component of the triangulated isosurface. The evolution of a ROI as a function of the threshold can be represented by a treelike structure. A multithreshold ROI is defined as a path on this tree, which starts from a terminal ROI and ends on the root ROI. For each ROI, the volume, surface area, roundness, density, and moments of inertia are computed as functions of the threshold and used as input to a classification system based on artificial neural networks. The method is suitable to detect different types of nodules, including juxta-pleural nodules and nodules connected to blood vessels. A training set of 109 low-dose MSCT scans made available by the Pisa center of the Italung-CT trial and annotated by expert radiologists was used for the algorithm design and optimization. The system performance was tested on an independent set of 23 low-dose MSCT scans coming from the Pisa Italung-CT center and on 83 scans made available by the Lung Image Database Consortium (LIDC) annotated by four expert radiologists. On the Italung-CT test set, for nodules having a diameter greater than or equal to 3 mm, the system achieved 84% and 71% sensitivity at false positive/scan rates of 10 and 4, respectively. For nodules having a diameter greater than or equal to 4 mm, the sensitivities were 97% and 80% at false positive/scan rates of 10 and 4, respectively. On the LIDC data set, the system achieved a 79% sensitivity at a false positive/scan rate of 4 in the detection of nodules with a diameter greater than or equal to 3 mm that have been annotated by all four radiologists.

Performance evaluation of a computer-aided detection algorithm for solid pulmonary nodules in low-dose and standard-dose MDCT chest examinations and its influence on radiologists

The aim of the study was to evaluate the performance of a computer-aided detection (CAD) algorithm in low-dose and full-dose multidetector-row CT (MDCT) of the thorax and its impact on radiologists' performance. Chest CT examinations of 77 patients were evaluated retrospectively for pulmonary nodules. All patients had undergone a 16-slice MDCT chest examination with a standard acquisition protocol. Artificial image noise was added to the raw data to simulate image acquisition at 10 mAs(eff.) The data were transferred to dedicated lung analysis software (LungCare) with a prototype CAD algorithm (LungCAD). CAD was applied to both dose settings. Images were read by a radiologist and a first-year resident with and without the software at both dose settings. All images were reviewed in consensus by the two radiologists to set the reference standard. Sensitivity results with respect to the reference standard were compared. No statistically significant differences in the detection rate for all pulmonary nodules could be found between low-dose and full-dose settings for the CAD software alone (p = 0.0065). Both radiologists displayed a statistically significant increase in sensitivity with the use of CAD (p<0.0001). In conclusion, CAD is beneficial in both low-dose and standard-dose settings. This may be beneficial in reducing false-negative diagnosis in lung cancer screening, standard chest examinations and the search for metastases.

Computer-aided diagnosis in lung nodule assessment

Computed tomography (CT) imaging is playing an increasingly important role in cancer detection, diagnosis, and lesion characterization, and it is the most sensitive test for lung nodule detection. Interpretation of lung nodules involves characterization and integration of clinical and other imaging information. Advances in lung nodule management using CT require optimization of CT data acquisition, postprocessing tools, and computer-aided diagnosis (CAD). The goal of CAD systems being developed is to both assist radiologists in the more sensitive detection of nodules and noninvasively differentiate benign from malignant lesions; the latter is important given that malignant lesions account for between 1% and 11% of pulmonary nodules. The aim of this review is to summarize the current state of the art regarding CAD techniques for the detection and characterization of solitary pulmonary nodules and their potential applications in the clinical workup of these lesions.

Long-term follow-up study of a population-based 1996–1998 mass screening programme for lung cancer using mobile low-dose spiral computed tomography

Early diagnosis and treatment are important for improvement of the low survival rate of patients with lung cancer. The objective of this study was to evaluate the long-term survival rate of patients identified to have lung cancer by our population-based baseline and annual repeat low-radiation dose computed tomography (low-dose CT) screenings, conducted in 1996-1998. A total of 13,037 CT scans were obtained from 5480 subjects (2969 men, 2511 women) aged 40-74 years at the initial CT screening. Lung cancer was detected in 63 subjects (57 were detected by CT scans and underwent surgery; 1 was detected by sputum cytology and underwent surgery; 3 rejected treatment; and 2 were interval cases that developed symptoms prior to the next annual repeat CT screening). Follow-up study included review of medical records. Death certificates were examined to check for any deceased interval case among participants. Postoperative follow-up of the 50 survived patients ranged from 70 to 117 (median, 101) months. Eight patients died during follow-up (6 due to lung cancer from 20 to 67 months after surgery and 2 deaths unrelated to lung cancer, each 7 and 60 months following surgery). Three patients who rejected treatment died 14 months to 6 years after positive screening CT scans, and the 2 interval cases died at each 17 and 30 months, respectively, following negative screening CT scans. Survival was analysed in 59 patients with lung cancer detected by low-dose CT screening (excluding two patients; one was detected by sputum cytology and the other had mass lesion already noted on the chest radiograph of the previous year). The 10-year survival calculated by the Kaplan-Meier method was 83.1% (95% CI: 0.735-0.927) for death from all causes and 86.2% (95% CI: 0.773-0.951) for death from lung cancer. The survival rate was excellent for never-smokers, patients with BAC and adenocarcinoma/mixed types with non-solid CT density pattern, associated with Noguchi's type A or B and pathologic stage IA. A poorer prognosis was noted in smokers with adenocarcinomas/mixed types, associated with part-solid or solid CT density pattern and Noguchi's type C or D. All patients with non-solid tumours measuring 6-13.5mm at presentation are alive, patients with part-solid tumours, measuring 17mm or more, or solid tumours, measuring 13mm or more at presentation were associated with increased risk of lung cancer-related morbidity or mortality. The estimated rate of possible over-diagnosis was 13% in total and we failed to cure 17% of patients encountered in the programme. Low-dose CT screening substantially improves the 10-year survival for lung cancer with minimal use of invasive treatment procedures.

Evolution of lung nodules < or =5 mm detected with low-dose CT in asymptomatic smokers

Low-dose CT is widely employed for the early diagnosis of lung cancer in high-risk populations even if screening programmes have not been clinically validated yet; however, the optimum follow-up schedule for small lung nodules of uncertain status has not been defined. The aim of this study was to assess outcomes for small pulmonary nodules (diameter < or =5 mm) detected by CT in asymptomatic smokers In 2000-2001, 1035 high-risk people were enrolled in an observational study for the early detection of lung cancer by yearly CT. The prevalence, incidence and evolution of small lung solid nodules are described 238 solid lung nodules < or = 5 mm were identified at initial low-dose CT in 165 people (prevalence 15.9%). 26% of them were not detected in the following 4 years, 43.3% did not change and 10.1% grew to >5 mm; three were removed and found to be malignant (all T1N0); the remaining 21 were followed yearly In the following year, 79 new small nodules were detected (incidence 7.9%). 11.4% were not detected in the subsequent 3 years, 79.7% did not change, 2.5% grew to > 5 mm and were followed yearly In conclusion, prevalent and incident nodules < or =5 mm detected by low-dose CT screening for lung cancer can be safely checked at 1 year intervals.

Pulmonary nodule detection on MDCT images: evaluation of diagnostic performance using thin axial images, maximum intensity projections, and computer-assisted detection

This study aimed at evaluating the diagnostic benefits of maximum intensity projections (MIP) and a commercially available computed-assisted detection system (CAD) for the detection of pulmonary nodules on MDCT as compared with standard 1-mm images on lung cancer screening material. Thirty subjects were randomly selected from our database. Three radiologists independently reviewed three types of images: axial 1-mm images, axial MIP slabs, and CAD system detections. Two independent experienced chest radiologists decided which were true-positive nodules. Two hundred eighty-five nodules > or =1 mm were identified as true-positive by consensus of two independent chest radiologists. The detection rates of the three independent observers with 1-mm axial images were 22 +/- 4.8%, 30 +/- 5.3%, and 47 +/- 2.8%; with MIP: 33 +/- 5.4%, 39 +/- 5.7%, and 45 +/- 5.8%; and with CAD: 35 +/- 5.6%, 36 +/- 5.6%, and 36 +/- 5.6%. There was a reading technique effect on the observers' sensitivity for nodule detection: sensitivities with MIP were higher than with 1-mm images or CAD for all nodules (F-values = 0.046). For nodules > or =3 mm, readers' sensitivities were higher with 1-mm images or MIP than with CAD (p < 0.0001). CAD was the most and MIP the less time-consuming technique (p < 0.0001). MIP and CAD reduced the number of overlooked small nodules. As MIP is more sensitive and less time consuming than the CAD we used, we recommend viewing MIP and 1-mm images for the detection of pulmonary nodules.

Population screening for lung cancer using computed tomography, is there evidence of clinical effectiveness? A systematic review of the literature

Lung cancer is the leading cause of death among all cancer types in the UK, killing approximately 34 000 people per year. By the time symptoms develop, the tumour is often at an advanced stage and the prognosis is bleak. Treatment at a less advanced stage of disease by surgical resection has been shown to substantially reduce mortality. Screening would be attractive if it could detect presymptomatic lung cancer at a stage when surgical intervention is feasible but has been the subject of scientific debate for the past three decades. The aim of this review was to examine the current evidence on the clinical effectiveness of screening for lung cancer using computed tomography. A systematic literature review searching 15 electronic databases and Internet resources from 1994 until December 2004/January 2005 was carried out. Information was summarised narratively. A total of 12 studies of computed tomography screening for lung cancer were identified including two RCTs and 10 studies of screening without comparator groups. The two RCTs were of short duration (1 year). None examined the effect of screening on mortality compared with no screening. The proportion of people with abnormal computed tomography findings varied widely between studies (5-51%). The prevalence of lung cancer detected was between 0.4% and 3.2% (number needed to screen to detect one lung cancer = 31 to 249). Incidence rates of lung cancer were lower (0.1-1%). Among the detected tumours, a high proportion were stage I or resectable tumours, 100% in some studies. Currently, there is insufficient evidence that computed tomography screening is clinically effective in reducing mortality from lung cancer.

Partnerships in oncology and radiology: the role of radiology in the detection, staging, and follow-up of lung cancer

In this review, I examine the multifaceted role of radiology in the diagnosis, staging, and management of lung cancer, highlighting new applications and modalities such as computer-aided detection of lung nodules and positron emission tomography/computed tomography for staging and monitoring response to therapy. Lung cancer screening is also discussed.

Pulmonary nodules: estimation of malignancy at thin-section helical CT--effect of computer-aided diagnosis on performance of radiologists

PURPOSE

To evaluate the effect of a computer-aided diagnosis (CAD) system on the diagnostic performance of radiologists for the estimation of the malignancy of pulmonary nodules on thin-section helical computed tomographic (CT) scans.

MATERIALS AND METHODS

The institutional review board approved use of the CT database; informed specific study-related consent was waived. The institutional review board approved participation of radiologists; informed consent was obtained from all observers. Thirty-three (18 malignant, 15 benign) pulmonary nodules of less than 3.0 cm in maximal diameter were evaluated. Receiver operating characteristic (ROC) analysis with a continuous rating scale was used to compare observer performance for the estimation of the likelihood of malignancy first without and then with the CAD system. The participants were 10 board-certified radiologists and nine radiology residents.

RESULTS

For all 19 participants, the mean area under the best-fit ROC curve (A(z)) values achieved without and with the CAD system were 0.843 +/- 0.097 (standard deviation) and 0.924 +/- 0.043, respectively. The difference was significant (P = .021). The mean A(z) values achieved without and with the CAD system were 0.910 +/- 0.052 and 0.944 +/- 0.040, respectively, for the 10 board-certified radiologists (P = .190) and 0.768 +/- 0.078 and 0.901 +/- 0.036, respectively, for the nine radiology residents (P = .009).

CONCLUSION

Use of the CAD system significantly (P = .009) improved the diagnostic performance of radiology residents for assessment of the malignancy of pulmonary nodules; however, it did not improve that of board-certified radiologists.