Detection Of Small Pulmonary Nodules Research Articles

CT-guided percutaneous marking of small pulmonary nodules with [99mTc]Tc-Macrosalb is very accurate and allows minimally invasive lung-sparing resection: a single-centre quality control.

The detection of small lung nodules in thoracoscopic procedure is difficult when the lesions are not located within the outer border of the lung. In the case of ground-glass opacities, it is often impossible to palpate the lesion. Marking lung nodules using a radiotracer is a known technique. We analysed the accuracy and safety of the technique and the potential benefits of operating in a hybrid operating room. 57 patients, including 33 (58%) females with a median age of 67 years (range 21-82) were included. In 27 patients, we marked and resected the lesion in a hybrid room. In 30 patients, the lesion was marked at the department of radiology the day before resection. [99mTc]Tc-Macrosalb (Pulmocis®) was used at an activity of 1 MBq in the hybrid room and at an activity of 3 MBq the day before to get technical feasible results. Radioactivity was detected using the Neoprobe® detection system. Precise detection and resection of the nodules was possible in 95% of the lesions and in 93% of the patients. Complete thoracoscopic resection was possible in 90% of the patients. Total conversion rate was 10%, but conversion due to failure of the marking of the nodule was observed in only 5% of the patients. Histology revealed 28 (37%) primary lung cancers, 24 (32%) metastases and 21 (28%) benign lesions. In 13 (23%) patients, minor complications were observed. None of them required additional interventions. The radio-guided detection of small pulmonary nodules is very accurate and safe after CT-guided injection of [99mTc]Tc-Macrosalb. Performing the operation in a hybrid room has several logistic advantages and allows using lower technetium-99m activities. The technique allows minimally invasive lung sparing resection and prevents overtreatment of benign and metastatic lesions.

Abnormal origin of the right posterior segmental bronchus: case report and literature review

BackgroundWith the increasing availability of chest computed tomography (CT), the detection of small pulmonary nodules has become more common, facilitating the development of lung segmental resection. However, anatomical variations of the bronchi are common, particularly in the right upper lobe of the lung.Case presentationWe report a case of thoracoscopic resection of the posterior segment of the right upper lobe of the lung. Preoperatively, the nodule was believed to be located in the superior segment of the right lower lobe. However, intraoperative exploration revealed that the nodule was located in the posterior segment of the right upper lobe, further showing that the bronchi of the posterior segment of the right lung opened into the bronchus intermedius. The procedure was completed uneventfully. Postoperative retrospective three-dimensional (3D) reconstruction of the lung CT images confirmed that the bronchi of the posterior segment of the right upper lobe originated from the bronchus intermedius.ConclusionsThis rare case highlights the importance of 3D reconstruction to guide accurate segmentectomy in patients with anatomic variations.

Thoracic surgery in Taiwan.

Taiwanese surgeons have pioneered major advances in the field of minimally invasive thoracic surgery. Since the establishment of the Taiwan Association of Thoracic and Cardiovascular Surgery [1986], the landscape of thoracic surgery has rapidly evolved from traditional thoracotomy to multi-port video-assisted thoracoscopic approaches. By early 21st century, further developments have included the single-port and subxiphoid techniques. This paper provides an overview of the Taiwanese thoracic surgery environment and its major accomplishments. With the increasing use of low-dose computed tomography for lung cancer screening, the detection of small pulmonary nodules has been growing steadily. High-end hybrid operating rooms comprising both imaging and surgical equipment are increasingly being applied in Taiwan as platforms for image-guided video-assisted thoracoscopic surgery (iVATS). Recently, we described an iVATS workflow for simultaneous detection and removal of small pulmonary nodules which was entirely performed by thoracic surgeons. With respect to esophageal malignancies, the implementation of robot-assisted esophagectomy has been a significant milestone in Taiwan. This technique allowed conducting an extensive lymph node dissection along the bilateral recurrent laryngeal nerve in a safe and effective manner. With 14 medical schools and 26 medical centers located on the island, Taiwan has been able to maintain a constant doctor-to-population ratio of 1-to-500. By partnering with the National Health Insurance and by taking advantage of state-of-the-art technologies, Taiwanese thoracic surgeons are continuously striving to deliver high-quality and cost-effective surgical care.

‘One-stop-shop’ diagnosis and stage-adapted surgical therapy for small nodules of early stage lung cancer in a hybrid operating room

Abstract Objective Emergent lung cancer screening programs increased detection of small pulmonary nodules. Anatomical resection in case of early-stage lung cancer with only one intervention becomes increasingly desirable. Current literature lacks procedure data about both diagnosis and subsequent indicated resection. After starting our hybrid operating room program, we reviewed the efficacy of detection, diagnosis and therapy in one-step. Methods Undiagnosed pulmonary nodules suspicious of lung cancer, which were not detectable by conventional video-assisted thoracoscopic surgery (VATS) due to localization and size, were scheduled for a hybrid procedure consisting of a cone-beam CT-guided hookwire insertion and C-arm assisted thoracoscopic wedge resection for frozen section. All procedures were analyzed for perioperative outcomes including success rate of image-guided nodule resection and rate of concomitant correct anatomical resection. Results Between July 2020 and July 2021, 23 patients with 25 nodules underwent image-guided VATS (iVATS) in the hybrid room. Twenty-two nodules were successfully marked by hookwire, three nodules were detected by ultrasound in one case and palpation in two cases. In 16 patients (70%) wedge resection with frozen section showed malignancy. Five patients with previous history of operated lung cancer received only a diagnostic wedge, as frozen section could not differentiate between primary or metastatic lung cancer. Eleven patients (48%) had early-stage primary lung cancer (8 adenocarcinoma, one typical carcinoid, one small-cell lung cancer and one squamous-cell lung cancer). Ten of them (91%) received a synchronous completion anatomical resection (seven lobectomies, three segmentectomies). In one patient, malignancy was only confirmed in final histology. Conclusion One-stop-shop diagnosis and treatment by iVATS with frozen section and concomitant completion anatomical resection in a hybrid operating room for otherwise non-well approachable early stage lung cancer is patient-convenient for the increasingly detected small pulmonary nodules.

Abstract 1002: Immune microenvironment features of lung adenomatous premalignancy in a Chinese cohort

Abstract Introduction: The widespread of implementation of computed tomography (CT) has resulted in a drastic increase in the detection of small pulmonary nodules presenting as ground glass opacities (GGOs). Many of these GGOs are atypical adenomatous hyperplasia (AAH), adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), and sometimes invasive adenocarcinoma (IAC). The concept of a continuum between the precursor lesions AAH and AIS to MIA and frankly invasive IAC is backed by a wealth of recent data showing a gradual decrease in overall survival from 100% for AAH, AIS and MIA to moderately lower rates for IAC. A growing body of evidence suggests that the immune response is a significant determinant of cancer progression. However, little is known about the immune microenvironment features in the early stages of lung carcinogenesis. Methods: A total of 40 tumor tissue samples including 10 AAH, 10 AIS, 10 MIA and 10 early IAC from 40 patients who underwent surgical resection of pulmonary nodules at Yancheng No.1 People's Hospital, China were included. Immunohistochemistry (IHC) staining for the expression of CD3, CD4, CD8 and programmed death ligand 1 (PD-L1) to assess the role of T-cell immune surveillance in these pre- and early lung cancers were performed. Results: We observed CD3, CD4, CD8 and PD-L1 positivity in AAH, AIS, MIA and IAC, suggesting that immunoediting has started before the invasion. Higher expressions of CD3, CD4, CD8 and PD-L1 in IAC implying tumor invasion. Conclusions: Our preliminary results of the immune subgroups provide evidence for immune recognition in pulmonary premalignancy and are critical for understanding tumorigenesis and the development of effective preventive and interception strategies. Associations with genomic landscape is underway. Citation Format: Liting Guo, Weiwei Shao. Immune microenvironment features of lung adenomatous premalignancy in a Chinese cohort [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1002.

Factors associated with subcentimeter pulmonary nodule outcomes followed with computed tomography imaging in oncology patients

IntroductionTechnological advancements in computed tomography (CT) have enabled the frequent detection of small pulmonary nodules (PNs), especially in patients with an oncologic history. It is important the malignant versus benign etiology of PNs be determined. The aim of the present study was to evaluate the behavior and clinical/radiological characteristics of subcentimeter PNs detected by CT in oncologic patients. MethodsAn observational, longitudinal, retrospective and single-center study was conducted with a sample of 100 patients with a diagnosis of a primary malignant solid tumor outside of the lungs who developed indeterminate subcentimeter PNs (n = 251) detected on consecutive thoracic CT scans from 2015 to 2017. Follow-up CTs for each patients were examined in each of three periods (0–3 months, 3–6 months, and 6 months to 1 year). ResultsIn our study sample, 28 patients (28 %) showed one or more signs suspicious of pulmonary metastasis, including ≥50 % PN growth, nodule growth followed by size reduction in patients undergoing chemotherapy, and the appearance of multiple nodules. The majority (56 %) of the PNs were detected during the 3–6-month follow-up CT scan. PNs with irregular, lobuled, or spiculated margins exhibited faster growth than PNs with regular, smooth margins. Malignancy of PNs was found to be significantly associated with being male, a primary colorectal cancer diagnosis, and advanced stage disease. ConclusionOur findings reinforce the necessity of an individualized CT follow-up strategy for patients with an oncologic history, as well as the importance of early nodule screening, with the inter-scan interval being dependent on the primary neoplasm.

Fluorescence-navigated Thoracoscopy for Detection of Small Pulmonary Nodules

Fluorescence-navigated Thoracoscopy for Detection of Small Pulmonary Nodules

Automatic Pulmonary Nodule Detection in CT Scans Using Convolutional Neural Networks Based on Maximum Intensity Projection.

Accurate pulmonary nodule detection is a crucial step in lung cancer screening. Computer-aided detection (CAD) systems are not routinely used by radiologists for pulmonary nodule detection in clinical practice despite their potential benefits. Maximum intensity projection (MIP) images improve the detection of pulmonary nodules in radiological evaluation with computed tomography (CT) scans. Inspired by the clinical methodology of radiologists, we aim to explore the feasibility of applying MIP images to improve the effectiveness of automatic lung nodule detection using convolutional neural networks (CNNs). We propose a CNN-based approach that takes MIP images of different slab thicknesses (5 mm, 10 mm, 15 mm) and 1 mm axial section slices as input. Such an approach augments the two-dimensional (2-D) CT slice images with more representative spatial information that helps discriminate nodules from vessels through their morphologies. Our proposed method achieves sensitivity of 92.7% with 1 false positive per scan and sensitivity of 94.2% with 2 false positives per scan for lung nodule detection on 888 scans in the LIDC-IDRI dataset. The use of thick MIP images helps the detection of small pulmonary nodules (3 mm-10 mm) and results in fewer false positives. Experimental results show that utilizing MIP images can increase the sensitivity and lower the number of false positives, which demonstrates the effectiveness and significance of the proposed MIP-based CNNs framework for automatic pulmonary nodule detection in CT scans. The proposed method also shows the potential that CNNs could gain benefits for nodule detection by combining the clinical procedure.

The Added Value of Computer-aided Detection of Small Pulmonary Nodules and Missed Lung Cancers.

Lung cancer at its earliest stage is typically manifested on computed tomography as a pulmonary nodule, which could be detected by low-dose multidetector computed tomography technology and the use of thinner collimation. Within the last 2 decades, computer-aided detection (CAD) of pulmonary nodules has been developed to meet the increasing demand for lung cancer screening computed tomography with a larger set of images per scan. This review introduced the basic techniques and then summarized the up-to-date applications of CAD systems in clinical and research programs and in the low-dose lung cancer screening trials, especially in the detection of small pulmonary nodules and missed lung cancers. Many studies have already shown that the CAD systems could increase the sensitivity and reduce the false-positive rate in the diagnosis of pulmonary nodules, especially for the small and isolated nodules. Further improvements to the current CAD schemes are needed to detect nodules accurately, particularly for subsolid nodules.

Clinical value of ultra high resolution CT in the diagnosis of pulmonary nodules

Objective To explore the clinical value of ultra high resolution CT in the diagnosis of pulmonary nodules. Methods From January 2014 to December 2016, 120 cases with small pulmonary nodules and confirmed by pathology(maximum diameter less than or equal to 2cm) in the Fifth People's Hospital of Datong were included in the study.The 120 patients received high resolution CT scan(512×512 matrix), ultra high resolution CT scan(1 024×1 024 matrix). The images of two kinds of resolution CT were observed and analyzed, compared with high-resolution CT scan, ultra high resolution CT scanning for detection of small pulmonary nodules, CT signs detection situation, qualitative diagnosis, image quality. Results Compared with the high resolution CT scan, ultra high resolution CT scan had no statistically significant differences in the detective rate of maximum diameter of 0.5~2cm small pulmonary nodules (χ2=0.695, P>0.05), but the maximum diameter of the ultra high resolution CT scan less than or equal to 0.5cm small lung nodules detected more than that of the high resolution CT scan(χ2=6.021, P 0.05). The diagnostic accordance rates of the ultra high resolution CT scan for pulmonary malignant nodules and benign nodules were 98.08%, 97.06%, respectively, which were higher than those of the high resolution CT scan(86.54%, 85.29%, χ2=4.875, 5.850, all P 0.05). Conclusion Compared with the conventional high resolution CT scan, ultra high resolution CT scan is better for small pulmonary nodules image quality, and can accurately diagnose small pulmonary nodules, with high diagnostic accuracy, especially for the maximum diameter of less than 0.5cm of small pulmonary nodules. Key words: Solitary pulmonary nodule; Tomography, X-ray computed; Diagnosis

How to Provide Gadolinium-Free PET/MR Cancer Staging of Children and Young Adults in Less than 1h: the Stanford Approach.

To provide clinically useful gadolinium-free whole-body cancer staging of children and young adults with integrated positron emission tomography/magnetic resonance (PET/MR) imaging in less than 1h. In this prospective clinical trial, 20 children and young adults (11-30 years old, 6 male, 14 female) with solid tumors underwent 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) PET/MR on a 3T PET/MR scanner after intravenous injection of ferumoxytol (5mg Fe/kg) and [18F]FDG (2-3MBq/kg). Time needed for patient preparation, PET/MR image acquisition, and data processing was compared before (n=5) and after (n=15) time-saving interventions, using a Wilcoxon test. The ferumoxytol-enhanced PET/MR images were compared with clinical standard staging tests regarding radiation exposure and tumor staging results, using Fisher's exact tests. Tailored workflows significantly reduced scan times from 36 to 24min for head to mid thigh scans (p<0.001). These streamlined PET/MR scans were obtained with significantly reduced radiation exposure (mean 3.4mSv) compared to PET/CT with diagnostic CT (mean 13.1mSv; p=0.003). Using the iron supplement ferumoxytol "off label" as an MR contrast agent avoided gadolinium chelate administration. The ferumoxytol-enhanced PET/MR scans provided equal or superior tumor staging results compared to clinical standard tests in 17 out of 20 patients. Compared to PET/CT, PET/MR had comparable detection rates for pulmonary nodules with diameters of equal or greater than 5mm (94 vs. 100%), yet detected significantly fewer nodules with diameters of less than 5 mm (20 vs 100%) (p=0.03). [18F]FDG-avid nodules were detected with slightly higher sensitivity on the PET of the PET/MR compared to the PET of the PET/CT (59 vs 49%). Our streamlined ferumoxytol-enhanced PET/MR protocol provided cancer staging of children and young adults in less than 1h with equivalent or superior clinical information compared to clinical standard staging tests. The detection of small pulmonary nodules with PET/MR needs to be improved.

Risk assessment in relation to the detection of small pulmonary nodules.

The National Lung Cancer Screening trial (NLST) demonstrated that individuals assigned to the LDCT screening arm had a 20% lower mortality than those who were assigned to the conventional chest radiography. The NLST was thoroughly analyzed by the US Preventive Task Force on CT Screening and they recommended that lung cancer screening should be implemented. A number of other countries have also recommended implementation, whilst others are awaiting the outcome of the NELSON Trial. However, recommendations for the management of CT screen detected nodules have only recently had any clarity. The management of CT detected nodules in the NLST was based on the identification and reporting of 4 mm diameter nodules found on the CT screens but there was no NLST radiology protocol in place for the management of nodules. The use of volumetric analysis is not routinely used in the USA and there is still a reliance on utilising the CT nodule diameter as the management parameter. The first pulmonary risk model was developed by the Canadians, utilising data sets from the Pan-Canadian Early detection of Lung cancer (PanCan) and validated in the chemoprevention trial dataset at the British Columbian Agency. This Canadian model, known as the Brock Model, is currently available and has been integrated into the British Thoracic Society guidelines on the management of pulmonary nodules. The American College of Radiology setup a Lung Cancer Screening Committee subgroup on Lung-RADS, to standardize lung cancer screening CT reporting and provide management recommendations. However, it has been recommended that the Lung-RADS system should be revised as the system as it has never been studied in a prospective fashion. The NELSON trial introduced a third screening test, the "indeterminate" screening test result, this was done with the aim to reduce the false-positives CT screening results and also utilized by the UKLS trial successfully. On comparing the radiological CT screen volumetric and diameter based protocols in the NELSON trial, the sensitivity and negative predictive value appeared to be comparable, however a higher specificity and positive predictive value was found for the volume-based protocols, thus confirming the advantage of utilising the volumetric approach over diameter The British Thoracic Society (BTS) has undertaken an in-depth piece of work developing guidelines on the management of pulmonary nodules, utilising the wealth of data published by the NELSON team and support the use of volumetric analysis for the management of pulmonary nodules.

Image-guided thoracoscopic surgery with dye localization in a hybrid operating room.

The rate of detection of small pulmonary nodules (SPNs) has increased. Thoracoscopic resection following image-guided localization had been a reliable alternative in their treatment. We present our experience with image-guided dye localization using robotic C-arm computed tomography (CT) followed by immediate video-assisted thoracoscopic surgery (VATS) for SPNs in a hybrid operating room (OR). From July 2015 to July 2016, 25 consecutive patients with SPNs smaller than 2 cm underwent robotic C-arm CT-guided blue dye tattooing followed by immediate VATS in a hybrid OR. Their medical records were retrospectively reviewed to evaluate the feasibility and safety of this novel procedure. Robotic C-arm CT-guided dye localization was successfully performed in 23 patients (92%). Wound extension was required for nodule identification in the remaining two patients. The median size of the nodules was 1.0 cm (range, 0.6-2.0 cm). The median needle localization time and surgery time were 46 and 109 min, respectively. All 25 patients had successful resection of their lesions. The pathological diagnoses were primary lung adenocarcinoma in 18 (72%), benign tumors in 5 (20%), and metastatic lesions in 2 (8%). There was no operative mortality. The median length of the postoperative stay was 3 days (range, 2-8 days). Complications were noted in two patients (8%). One patient had a penetrating injury of the diaphragm during needle localization. The other had pneumonia postoperatively. Both patients were managed conservatively. Our experience showed that robotic C-arm CT-guided dye localization followed by immediate thoracoscopic surgery in a hybrid OR is safe and feasible. It may become an effective and attractive alternative in managing SPNs.

The additional value of the lateral chest radiograph for the detection of small pulmonary nodules-a ROC analysis.

For the past 30 years, many authors have described different advantages of the use of the additional lateral chest radiograph. However, some radiologic departments gave up performing the lateral view recently. A potential reason for this might be a lack of evidence for any diagnostic benefit of the additional lateral view of the thorax in recent studies. The objective of this study was to evaluate the diagnostic benefit of the additional lateral view for the detection of small pulmonary nodules compared with CT examinations as a gold standard. The patient population consisted of 45 patients with SPN and 45 patients without SPN. Four radiologists with varying experience in the assessment of thoracic imaging first examined the sole posteroanterior (PA) projection. After a few days, they were instructed to examine the PA and the additional lateral view. A receiver-operating characteristic analysis was accomplished to compare the documented results. The mean Az value of the sole PA view was 0.75 and 0.77 by the combination of PA and additional lateral view. So, there was no significant difference between the detectable Az values (Δ = 0.02; p = 0.384). With a cut-off value of >3, the additional view even reduced the sensitivity by averaging to 5.6%. The decrease of sensitivity by using the additional view was most detectable within the group of more experienced radiologists. The additional lateral view of the chest provides no diagnostic benefit in the detection of small pulmonary nodules in comparison with the sole PA projection. Nevertheless, the results of the present study must not be understood as a general evaluation of the benefits of the lateral radiograph per se, because we did not examine other relevant issues (i.e. cardiac failure, lung parenchyma diseases or abnormalities in hilar anatomy). Advances in knowledge: Our study demonstrates a lack of evidence for any diagnostic benefit of the additional lateral view of the thorax in detecting SPN.

Detection of Small Pulmonary Nodules with Ultrashort Echo Time Sequences in Oncology Patients by Using a PET/MR System.

To investigate the utility of a free-breathing ultrashort echo time (UTE) sequence for the evaluation of small pulmonary nodules in oncology patients by using a hybrid positron emission tomography (PET)/magnetic resonance (MR) imaging system and to compare the nodule detection rate between UTE and a conventional three-dimensional gradient-recalled-echo (GRE) technique. In this HIPAA-compliant, institutional review board-approved prospective study, 82 pulmonary nodules were identified in eight patients with extrathoracic malignancies. Patients underwent free-breathing UTE and dual-echo three-dimensional GRE imaging of the lungs in a hybrid PET/MR imaging unit immediately after clinical PET/computed tomography (CT). CT was considered the reference standard for nodule detection. Two reviewers identified nodules and obtained measurements on MR images. The McNemar test was used to evaluate differences in nodule detection rate between MR techniques, and interrater agreement was assessed by using Bland-Altman plots. Mean nodule diameter ± standard deviation was 6.2 mm ± 2.7 (range, 3-17 mm). The detection rate was higher for UTE imaging than for dual-echo GRE imaging for nodules of at least 4 mm (82% vs 34%, respectively; P < .001), with the largest difference in detection noted in the 4-8-mm nodule group (79% vs 21%, P < .001). UTE imaging displayed a higher detection rate than dual-echo GRE imaging for nodules without fluorodeoxyglucose avidity (68% vs 22%, respectively; P < .001). Interrater reliability of nodule detection with MR imaging was high (κ = 0.90 for UTE imaging and κ = 0.92 for dual-echo GRE imaging). A free-breathing UTE sequence has high sensitivity for the detection of small pulmonary nodules (4-8 mm) and outperformed a three-dimensional dual-echo GRE technique for the detection of small, non-fluorodeoxyglucose-avid nodules.

Optimal image reconstruction for detection and characterization of small pulmonary nodules during low-dose CT

To optimize the slice thickness/overlap parameters for image reconstruction and to study the effect of iterative reconstruction (IR) on detectability and characterization of small non-calcified pulmonary nodules during low-dose thoracic CT. Data was obtained from computer simulations, phantom, and patient CTs. Simulations and phantom CTs were performed with 9 nodules (5, 8, and 10mm with 100, -630, and -800 HU). Patient data were based on 11 ground glass opacities (GGO) and 9 solid nodules. For each analysis the nodules were reconstructed with filtered back projection and IR algorithms using 10 different combinations of slice thickness/overlap (0.5-5mm). The attenuation (CT#) and the contrast to noise ratio (CNR) were measured. Spearman's coefficient was used to correlate the error in CT# measurements and slice thickness. Paired Student's t test was used to measure the significance of the errors. CNR measurements: CNR increases with increasing slice thickness/overlap for large nodules and peaks at 4.0/2.0mm for smaller ones. Use of IR increases the CNR of GGOs by 60%. CT# measurements: Increasing slice thickness/overlap above 3.0/1.5mm results in decreased CT# measurement accuracy. Optimal detection of small pulmonary nodules requires slice thickness/overlap of 4.0/2.0mm. Slice thickness/overlap of 2.0/2.0mm is required for optimal nodule characterization. IR improves conspicuity of small ground glass nodules through a significant increase in nodule CNR. • Slice thickness/overlap affects the accuracy of pulmonary nodule detection and characterization. • Slice thickness ≥3mm increases the risk of misclassifying small nodules. • Optimal nodule detection during low-dose CT requires 4.0/2.0-mm reconstructions. • Optimal nodule characterization during low-dose CT requires 2.0/2.0-mm reconstructions. • Iterative reconstruction improves the CNR of ground glass nodules by 60%.

Feasible Method to Assess the Performance of a Lung Cancer CT Screening CAD System in Clinical Practice: Dependence on Nodule Size and Density

Detection of small pulmonary nodules is the goal of lung cancer screening. Computer-aided detection (CAD) systems are recommended to use in lung cancer computed tomography (CT) screening to increase the accuracy of nodule detection. Size and density of lung nodules are primary factors in determining the risk of malignancy. Therefore, purpose of this study is to apply computer-simulated virtual nodules based on the point spread function (PSF) measured in same scanner (maintaining spatial resolution condition) to assess the CAD system performance dependence on nodule size and density. Virtual nodules with density differences between lung background and nodule density (ΔCT) values (200, 300 and 400 HU) and different sizes (4 to 8 mm) were generated and fused on clinical images. CAD detection was performed and free-response receiver operating characteristic (FROC) curves were obtained. Results show that both density and size of virtual nodules can affect detection efficiency. Detailed results are possible to use for quantitative analysis of a CAD system performance. This study suggests that PSF-based virtual nodules could be effectively used to assess the lung cancer CT screening CAD system performance dependence on nodule size and density.

Standard versus inverted digital luminescence radiography in detecting pulmonary nodules: A ROC analysis

ObjectiveObserver performance tests were conducted to compare the effect of presenting digital luminescence radiography (DLR) monitor images in positive mode (“bones black”) or negative mode (“bones white”) in the detectability of subtle lung nodules. MethodsFive radiologists independently reviewed digital radiographs of 55 patients with either (a) a single, small (6–12mm), non- calcified peripheral nodule confirmed by chest CT (n=47) or (b) normal finding (n=8) confirmed by chest CT, respectively. Mean size of pulmonary nodules was 8.3mm (range 6–12mm, median 7mm). Radiographs were displayed either in standard mode (bones white) or inverse intensity (bones black). A total of 550 observations resulted. For the evaluation ROC analysis was performed using a specialized computer algorithm. ResultsThe standard presentation mode showed a sensitivity of 61.7% and a specificity of 72.5%, the inverse presentation mode a sensitivity of 68.1% and a specificity of 75.0%. ROC- analysis showed that the difference between the standard mode (Az- value 0.694) and the inverse mode (Az- value 0.810) was significant in favour of the inverse presentation mode (p=0.001). This finding was especially observed in more experienced radiologist (Az- values 0.716 vs. 0.909, P<0.001). ConclusionOur study demonstrates a significant advantage of the inverse mode in the detection of small pulmonary nodules compared with the commonly used negative mode when interpreted by more experienced radiologists. Advance in knowledgeInverse intensity images (“bones black”) may have some advantages in the detection of small pulmonary nodules in experienced readers when presented on a stand-alone display.

Gray-Scale Reversal for the Detection of Pulmonary Nodules on a PACS Workstation

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

Image Analysis of Small Pulmonary Nodules Identified by Computed Tomography

Detection of small pulmonary nodules has markedly increased as computed tomography (CT) technology has advanced and interpretation evolved from viewing small CT images on film to magnified images on large, high-resolution computer monitors. Despite these advances, determining the etiology of a lung nodule short of major surgery remains problematic. Initial nodule size is a major criterion in evaluating the risk for malignancy, and the majority of CT detected nodules are <10 mm in diameter. Also, the likelihood that the nodule is a lung cancer increases with increasing age and smoking history, and such clinical information needs to be integrated into algorithms that guide the workup of such nodules. Baseline and annual repeat screening results are also very helpful in developing and assessing the usefulness of such algorithms. Based on CT morphology, subtypes of nodules have been identified; today nodules are routinely classified as being solid, part-solid, or nonsolid. It has been shown that part-solid nodules have a higher frequency of being malignant than solid or nonsolid ones. Other nodule characteristics such as spiculation are useful, although granulomas and fibrosis also have such features, so these characteristics have not been as useful as nodule-growth assessment. Depending on the aggressiveness of the lung cancer and the size of the nodule when it is initially seen, a follow-up CT scan 1-3 months after the first CT scan can identify those nodules with growth at a malignant rate. Software has been developed by all CT scanner manufacturers for such growth assessment, but the inherent variability of such assessments needs further development. Nodule-growth assessment based on 2-dimensional approaches is limited; therefore, software has been developed for the 3-dimensional assessment of growth. Different approaches for such growth assessment have been developed, either using automated computer segmentation techniques or hybrid methods that allow the radiologist to adjust such segmentation. There are, however, inherent reasons for variability in such measurements that need to be carefully considered, and this, together with continued technologic advances and integration of the relevant clinical information, will allow for individualization of the algorithms for the workup of small pulmonary nodules.