Follow-up Low-dose Computed Tomography Research Articles

Using Telehealth to Increase Lung Cancer Screening Referrals for At-Risk Veterans in Rural Communities.

At-risk rural veterans have low rates of lung cancer screening (LCS). This proof-of-principle quality improvement project aimed to determine whether a telehealth intervention would increase referrals for at-risk veterans living in the rural upper Midwest and attending a smoking cessation program to LCS with low-dose computed tomography (LDCT) of the chest. Sixty-eight of 74 LCS-eligible rural veterans who self-enrolled in a smoking cessation program were contacted by telephone. Those who agreed to enroll in LCS were referred to LDCT and followed for 4 months. At the conclusion of the intervention, the number of referrals and screenings performed were tabulated. LDCT reports were reviewed and scored according to Lung CT Screening Reporting and Data System (Lung-RADS) version 1.1. Only 3 of 74 LCS-eligible veterans (4%) underwent LDCT before initiation of this telehealth intervention. By the conclusion of this 4-month project, 19 of 74 veterans (26%) underwent LDCT. Forty-one veterans were successfully contacted and 29 agreed to participate in LCS. Of those who agreed to participate, 19 underwent LDCT within 4 months. Of the veterans who received LDCT, 10 were diagnosed with Lung-RADS 1, 7 with Lung-RADS 2, 1 with Lung-RADS 3, and 1 with Lung-RADS 4B. Annual follow-up LDCT or referral for further evaluation were pursued in each case. Collectively, these data suggest that telehealth intervention could increase referrals of at-risk rural veterans to a centralized LCS program at a regional US Department of Veterans Affairs medical facility.

Patient Adherence in an Academic Medical Center's Low-dose Computed Tomography Screening Program.

Low-dose computed tomography (LDCT) screening is an important tool for reducing lung cancer mortality. This study describes a single center's experience with LDCT and attempts to identify any barriers to compliance with standard guidelines. This is a retrospective review of a single university-based hospital system from 2015 to 2019. All individuals who met eligibility for lung cancer screening were entered into a database. The definition of adherence with the screening program was determined by the recommended timeline for the follow-up LDCT. Cohorts were split by adherence and demographics were compared. A total of 203 LDCTs were performed in 121 patients who met eligibility for LDCT and had appropriate surveillance from 2015 to 2019. The average age was 64 years old. The overall adherence rate for prescribed LDCTs was 59.1%. Patients with Lung-RADS score 2 had 2.43 times higher odds of adherence relative to patients with Lung-RADS score 1 (odds ratio [OR]=2.43; 95% confidence interval [CI]: 1.23-4.83; P=0.011). African American patients had 42% lower odds of adherence relative to white patients (OR=0.58; 95% CI: 0.32-1.06; P=0.076). Patients with non-District of Columbia zip codes had 57% higher odds of adherence relative to those with District of Columbia zip codes, although this did not reach statistical significance (OR=1.57; 95% CI: 0.87-2.82; P=0.136). Despite the implementation of a multidisciplinary, academic LDCT screening program, overall adherence rate to prescribed follow-up scans was suboptimal. Socioeconomic disparities and African American race may negatively affect adherence to lung cancer screening LDCT guidelines. Patients with concerning findings on initial LDCT had a higher association of adherence to guidelines.

Optimum diameter threshold for lung nodules at baseline lung cancer screening with low-dose chest CT: exploration of results from the Korean Lung Cancer Screening Project.

To explore the optimum diameter threshold for solid nodules to define positive results at baseline screening low-dose CT (LDCT) and to compare two-dimensional and volumetric measurement of lung nodules for the diagnosis of lung cancers. We included consecutive participants from the Korean Lung Cancer Screening project between 2017 and 2018. The average transverse diameter and effective diameter (diameter of a sphere with the same volume) of lung nodules were measured by semi-automated segmentation. Diagnostic performances for lung cancers diagnosed within 1 year after LDCT were evaluated using area under receiver-operating characteristic curves (AUCs), sensitivities, and specificities, with diameter thresholds for solid nodules ranging from 6 to 10 mm. The reduction of unnecessary follow-up LDCTs and the diagnostic delay of lung cancers were estimated for each threshold. Fifty-two lung cancers were diagnosed among 10,424 (10,141 men; median age 62 years) participants within 1 year after LDCT. Average transverse (0.980) and effective diameters (0.981) showed similar AUCs (p = .739). Elevating the average transverse diameter threshold from 6 to 9 mm resulted in a significantly increased specificity (91.7 to 96.7%, p < .001), a modest reduction in sensitivity (96.2 to 94.2%, p = .317), a 60.2% estimated reduction of unnecessary follow-up LDCTs, and a diagnostic delay in 1.9% of lung cancers. Elevating the threshold to 10 mm led to a significant reduction in sensitivity (86.5%, p = .025). Elevating the diameter threshold for solid nodules from 6 to 9 mm may lead to a substantial reduction in unnecessary follow-up LDCTs with a small proportion of diagnostic delay of lung cancers. • Elevation of the diameter threshold for solid nodules from 6 to 9 mm can substantially reduce unnecessary follow-up LDCTs with a small proportion of diagnostic delay of lung cancers. • The average transverse and effective diameters of lung nodules showed similar performances for the prediction of a lung cancer diagnosis.

P2.11-08 CT Screening of Never Smokers

We wanted to update our previous reports of the impact of SHTS on lung cancer and cardiovascular disease in never smokers and the usefulness of low-dose CT (LDCT) screening using the I-ELCAP protocol. Never smokers, defined as having smoked less than 100 cigarettes in their lifetime, were enrolled in our LDCT screening program. All signed IRB-HIPAA compliant consents. Patient demographics, medical history, and validated SHTS-exposure questionnaire were obtained at baseline. The SHTS-exposure score was computed for all participants together with LDCT Ordinal score for coronary artery calcifications (CAC), emphysema, lung cancer diagnosis and treatment were documented. At two of the institutions, we also performed pulmonary function tests, and measured the main pulmonary artery (MPA) and ascending aorta (AA) measurements, determined the automated aortic calcium score and extent of atherosclerotic plaque present in the coronary arteries using CT angiograms. Frequency of abnormal pulmonary function (FEV1/FVC ratio<0.7) and MPA/AA ratio≥1.0 were evaluated. We examined the relationship between SHTS exposure and these disease conditions. Among 14,018 never smokers, 6733 (48.1%) were women, 7276 (51.9%) men. Among them, 5236 (37.4%) had at least one noncalcified nodules (NCNs). Of the 14,018, 855 (6.1%) had at least one NCN 6.0 mm but less than 15.0 mm for which follow-up LDCT is recommended and 113 (0.8%) had NCN 15.0 mm or larger (Table 1). Lung cancer was diagnosed in 55 (0.4%); 53(96.4%) resulting from findings on baseline LDCT and 2(3.6%) from the subsequent annual repeat LDCTs. Of the 55, 47 (85.5%) were clinical stage I; 49 had surgical resection, 4 treated with radiation therapy, and 2 with chemotherapy. Diagnosis was adenocarcinoma in 44, squamous-cell in 7, small-cell in 1 and other in 3. Post-surgically, 45 (81.8%) of the 47 were pathologic Stage IA (T1a-1cN0M0). Of the 14,018 never smokers, the CAC score was 0 for 10,956 (78.2%), 1-3 for 1941 (13.9%), and 4-12 for 1211(8.0%). Emphysema was present in 310 (2.2%) participants. The prevalence of lung cancer (p=0.04) was significantly associated with SHTS exposure, as was CAC (p<0.0001) and emphysema (p=0.03). In the subset of participants where additional measurements are available, abnormal pulmonary function tests (p=0.04), automated aortic calcium score (p=0.009), MPA/AA ratio≥1.0 (p=0.009) and presence and extent of coronary artery plaque (p<0.0001). These results suggest that LDCT screening is of benefit for never smokers exposed to SHTS for identification of early lung cancer, cardiovascular disease and emphysema.

Ten-year results of the Multicentric Italian Lung Detection trial demonstrate the safety and efficacy of biennial lung cancer screening

BackgroundThe Multicentric Italian Lung Detection (MILD) trial demonstrated that prolonged low-dose computed tomography (LDCT) screening could achieve a 39% reduction in lung cancer (LC) mortality. We have here evaluated the long-term results of annual vs. biennial LDCT and the impact of screening intensity on overall and LC-specific mortality at 10 years. Patients and methodsBetween 2005 and 2018, the MILD trial prospectively randomised the 2376 screening arm participants to annual (n = 1190) or biennial (n = 1186) LDCT, for a median screening period of 6.2 years and 23,083 person-years of follow-up. The primary outcomes were 10-year overall and LC-specific mortality, and the secondary end-points were the frequency of advanced-stage and interval LCs. ResultsThe biennial LDCT arm showed a similar overall mortality (hazard ratio [HR] 0.80, 95% confidence interval [CI] 0.57–1.12) and LC-specific mortality at 10 years (HR 1.10, 95% CI 0.59–2.05), as compared with the annual LDCT arm. Biennial screening saved 44% of follow-up LDCTs in subjects with negative baseline LDCT, and 38% of LDCTs in all participants, with no increase in the occurrence of stage II-IV or interval LCs. ConclusionsThe MILD trial provides original evidence that prolonged screening beyond five years with biennial LDCT can achieve an LC mortality reduction comparable to annual LDCT, in subjects with a negative baseline examination.

Statistical CT reconstruction using region-aware texture preserving regularization learning from prior normal-dose CT image

In some clinical applications, prior normal-dose CT (NdCT) images are available, and the valuable textures and structure features in them may be used to promote follow-up low-dose CT (LdCT) reconstruction. This study aims to learn texture information from the NdCT images and leverage it for follow-up LdCT image reconstruction to preserve textures and structure features. Specifically, the proposed reconstruction method first learns the texture information from those patches with similar structures in NdCT image, and the similar patches can be clustered by searching context features efficiently from the surroundings of the current patch. Then it utilizes redundant texture information from the similar patches as a priori knowledge to describe specific regions in the LdCT image. The advanced region-aware texture preserving prior is termed as ‘RATP’. The main advantage of the PATP prior is that it can properly learn the texture features from available NdCT images and adaptively characterize the region-specific structures in the LdCT image. The experiments using patient data were performed to evaluate the performance of the proposed method. The proposed RATP method demonstrated superior performance in LdCT imaging compared to the filtered back projection (FBP) and statistical iterative reconstruction (SIR) methods using Gaussian regularization, Huber regularization and the original texture preserving regularization.

ADHERENCE TO ANNUAL LUNG CANCER SCREENING WITHIN THE VETERANS HEALTH ADMINISTRATION LUNG CANCER SCREENING DEMONSTRATION PROJECT

SESSION TITLE: Lung Cancer Screening: New Questions and New Answers SESSION TYPE: Original Investigations PRESENTED ON: 10/09/2018 08:45 AM - 09:45 AM PURPOSE: The National Lung Screening Trial (NLST) demonstrated a lung cancer mortality reduction from screening high risk individuals with low-dose computed tomography (LDCT) annually for three years. Mortality benefit and cost-efficacy of LDCT screening is dependent on adherence with screening and in the NLST the adherence rate was 95%. This is high compared to adherence rates from colon cancer, breast cancer, and cervical cancer in the community which have reportedly averaged 40-65%. We aimed to examine the adherence to annual LDCT screening after baseline LDCT within the Veterans Health Administration (VHA) Lung Cancer Screening Demonstration Project (LCSDP). METHODS: This is a retrospective observational cohort study of Veterans screened for lung cancer within the VHA LCSDP. The original project was conducted from July 1, 2013, and June 30, 2015 at eight geographically diverse Veterans Affairs hospitals. Screening was performed in current or former smokers (quit within the past 15 years) ages 55-80 with at least a 30-pack year smoking history. We utilized data generated from the LCSDP and 18 months following its completion stored in the VHA Corporate Data Warehouse. Adherence to screening was defined as it was in the NLST as having undergone a follow-up LDCT within 15 months from baseline scan. RESULTS: A total 2,106 Veterans underwent a baseline LDCT across all sites. Sixty percent (n=1269) had scans negative for nodules ≥ 4mm in size and repeat annual LDCT was recommended. In this group with a negative baseline scan, 149 were considered no longer eligible for screening because they had been diagnosed with lung cancer, were undergoing evaluation for cancer, no longer met the target age or years of cessation, were considered to have other life-limiting disease or were no longer interested in participating. Of the 1120 remaining eligible for repeat annual LDCT, 870 went on to undergo the follow-up scan yielding a 77.6% adherence rate for annual screening in those with a normal baseline scan. CONCLUSIONS: The American College of Chest Physicians (ACCP) and the American Thoracic Society (ATS) have outlined the components necessary for high-quality screening programs. One highlighted component is adherence with annual repeat LDCT. This study demonstrates that even within the context of a well-designed, implemented and guideline adherent LDCT screening program, adherence is not optimal and does not reach the reported 95% of the NLST when the baseline scan is negative. Both mortality benefit and cost-efficacy are likely to suffer without better adherence. Future research is needed to identify mechanisms and interventions to improve adherence. CLINICAL IMPLICATIONS: This study demonstrates that adherence with annual LDCT following a negative baseline scan is not optimal and highlights the need for measures to improve adherence to ensure that lung cancer screening achieves the most benefit possible. DISCLOSURES: No relevant relationships by Paul Brasher, source=Web Response research grant relationship with auris Please note: $5001 - $20000 Added 05/24/2018 by Gerard Silvestri, source=Web Response, value=Grant/Research Support Research grant relationship with Exact Sciences Please note: $20001 - $100000 Added 11/21/2017 by Nichole Tanner, source=Web Response, value=Grant/Research Consultant relationship with Exact Sciences Please note: $1001 - $5000 Added 11/21/2017 by Nichole Tanner, source=Web Response, value=Honoraria Grant/Research relationship with Oncimmune Please note: $5001 - $20000 Added 11/21/2017 by Nichole Tanner, source=Web Response, value=Grant/Research Support Speaker/Speaker's Bureau relationship with Oncocyte Please note: $1-$1000 Added 11/21/2017 by Nichole Tanner, source=Web Response, value=Honoraria Consultant relationship with Cook Medical Please note: $1001 - $5000 Added 11/21/2017 by Nichole Tanner, source=Web Response, value=Consulting fee Consultant relationship with Olympus America Please note: $1-$1000 Added 11/21/2017 by Nichole Tanner, source=Web Response, value=Consulting fee Grant relationship with Cook Medical Please note: >$100000 Added 11/21/2017 by Nichole Tanner, source=Web Response, value=Grant/Research Support Research relationship with Olympus Medical Please note: >$100000 Added 11/21/2017 by Nichole Tanner, source=Web Response, value=Grant/Research Support No relevant relationships by Derik Yeager, source=Web Response

Assessment of prior image induced nonlocal means regularization for low-dose CT reconstruction: Change in anatomy.

Repeated computed tomography (CT) scans are prescribed for some clinical applications such as lung nodule surveillance. Several studies have demonstrated that incorporating a high-quality prior image into the reconstruction of subsequent low-dose CT (LDCT) acquisitions can either improve image quality or reduce data fidelity requirements. Our proposed previous normal-dose image induced nonlocal means (ndiNLM) regularization method for LDCT is an example of such a method. However, one major concern with prior image based methods is that they might produce false information when the prior image and the current LDCT image show different structures (for example, if a lung nodule emerges, grows, shrinks, or disappears over time). This study aims to assess the performance of the ndiNLM regularization method insituations with change in anatomy. We incorporated the ndiNLM regularization into the statistical image reconstruction (SIR) framework for reconstruction of subsequent LDCT images. Because of its patch-based search mechanism, a rough registration between the prior image and the current LDCT image is adequate for the SIR-ndiNLM method. We assessed the performance of the SIR-ndiNLM method in lung nodule surveillance for two different scenarios: (a) the nodule was not found in a baseline exam but appears in a follow-up LDCT scan; (b) the nodule was present in a baseline exam but disappears in a follow-up LDCT scan. We further investigated the effect of nodule size on the performance of the SIR-ndiNLM method. We found that a relatively large search-window (e.g., 33×33) should be used for the SIR-ndiNLM method to account for misalignment between the prior image and the current LDCT image, and to ensure that enough similar patches can be found in the prior image. With proper selection of other parameters, experimental results with two patient datasets demonstrated that the SIR-ndiNLM method did not miss true nodules nor introduce false nodules in the lung nodule surveillance scenarios described above. We also found that the SIR-ndiNLM reconstruction shows improved image quality when the prior image is similar to the current LDCT image in anatomy. These gains in image quality might appear small upon visual inspection, but they can be detected using quantitative measures. Finally, the SIR-ndiNLM method also performed well in ultra-low-dose conditions and with different nodule sizes. This study assessed the performance of the SIR-ndiNLM method insituations in which the prior image and the current LDCT image show substantial anatomical differences, specifically, changes in lung nodules. The experimental results demonstrate that the SIR-ndiNLM method does not introduce false lung nodules nor miss true nodules, which relieves the concern that this method might produce false information. However, there is insufficient evidence that these findings will hold true for all kinds of anatomical changes.

MA01.10 Performance of ACR Lung-RADS in the 1st Brazilian Lung Cancer Screening Trial (BRELT1)

In BRELT1 we found a significant number of low dose CT (LDCT) considered positive (nodules > 4mm). The aim of this study was to assess the effect of applying ACR Lung-RADS and Pre-Test Probability of Malignancy (PTPM) in suspicious nodules ≥ 8mm founded in a clinical CT lung screening program. Clinical LDCT (baseline and follow up) containing nodules ≥ 8mm were retroactively reclassified using the new ACR Lung-RADS™ structured reporting system and PTPM. The model used in this study to predict the probability of malignancy was designed by Swensen et al and included patient’s age, current or former smoker, diameter of the nodule, speculation and location. All LDCT had initially been interpreted by radiologists accredited in CT lung screening reporting following the National Comprehensive Cancer Network’s Clinical Practice Guidelines in Oncology: Lung Cancer Screening (version 1.2012), which considered as positive the same criteria from the National Lung Screening Trial. In BRELT1 were recruited 790 current or former smokers, with a heavy smoking history. A total of 552 nodules were found in 312 positive LDCT at baseline (39%). LDCT follow up was performed in 89.1% of this population. From them 74 patients presented solid or semi solid nodules ≥ 8mm in the highest diameter. According to ACR Lung-RADS™ 39 baseline LDCT were classified as 4A (52.7%), 6 as 4B (8.1%), 17 as 4X (22.9%) and 10 as 2 (13.5%). Follow-up LDCT showed reduction in the category in more than 80% of cases. Using the PTPM, 44 cases were considered at moderate risk (between 6 and 60%) and 30 cases of high risk for malignancy (over 60%). None was considered low risk (5% or less). Among 26 patients who underwent biopsy in BRELT1, we found 12 cases of lung cancer, of which 90% were stage IA or IB. The application of ACR Lung-RADS and PTPM associated with careful multidisciplinary assessment can help in the decision process. The follow-up of patients with positive nodules requires careful analysis of the main factors related to malignancy.

Subcentimeter lung nodules stable for 2 years at LDCT: long-term follow-up using volumetry.

Subcentimeter nodules without change in size during long-term follow-up period (for minimum 2 years) are assumed as benign lesions. However, the 2-year stability rule has not been fully verified so far and is still questionable. Thus, we aimed to retrospectively investigate long-term follow-up results for 2-year stable subcentimeter nodules at screening low-dose computed tomography (LDCT). A total of 635 subjects having had follow-up LDCTs for the initial 2-year screening period and additional 3 years thereafter and having had non-calcified subcentimeter nodules were included. By using computed tomography (CT) nodule volumetry software, we measured interval changes in nodule volume. A total of 1107 subcentimeter nodules (1037 solid, 70 ground-glass opacity nodules (GGNs)) were detected at baseline CT. Of 1037 solid nodules, 1032 showed no growth during the initial 2-year and 5-year follow-up period. Fifty-nine GGNs were stable for initial 2 years, but two (3.4%) were later proved as adenocarcinomas. Among five solid nodules that showed growth during the initial 2-year follow-up period, one (20%) proved to be an adenocarcinoma, whereas four (36.4%) of 11 GGNs that demonstrated growth were diagnosed as lung cancers. All solid subcentimeter nodules having initial 2-year stability at screening LDCT can be considered benign because none shows growth at further follow-up CT. On the other hand, subcentimeter GGNs have more chance of growth than solid nodules and need further follow-up CT for more than 2 years.

Four-Year Results of Low-Dose CT Screening and Nodule Management in the ITALUNG Trial

Recruitment and nodule management are critical issues of lung cancer screening with low-dose computed tomography (LDCT). We report subjects' compliance and results of LDCT screening and management protocol in the active arm of the ITALUNG trial. Three thousand two hundred six smokers or former smokers invited by mail were randomized to receive four annual LDCT (n = 1613) or usual care (n = 1593). Management protocol included follow-up LDCT, 2-[18F]fluoro-2-deoxy-D glucose positron emission tomography (FDG-PET), and CT-guided fine-needle aspiration biopsy (FNAB). One thousand four hundred six subjects (87%) underwent baseline LDCT, and 1263 (79%) completed four screening rounds. LDCT was positive in 30.3% of the subjects at baseline and 15.8% subsequently. Twenty-one lung tumors in 20 subjects (1.5% detection) were found at baseline, and 20 lung tumors in 18 subjects (0.5% detection) in subsequent screening rounds. Ten of 18 prevalent (55%) and 13 of 17 incident (76%) non-small-cell cancers were in stage I. Interval growth enabled diagnosis of lung cancer in 16 subjects (42%), but at least one follow-up LDCT was obtained in 741 subjects (52.7%) over the screening period. FDG-PET obtained in 6.5% of subjects had 84% sensitivity and 90% specificity for malignant lesions. FNAB obtained in 2.4% of subjects showed 90% sensitivity and 88% specificity. Positivity of both FDG-PET and FNAB invariably predicted malignancy. Surgery for benign lesions was performed on four subjects (10% of procedures) but followed protocol violations on three subjects. High-risk subjects recruited by mail who entered LDCT screening showed a high and stable compliance. Efficacy of screening is, however, weakened by low detection rate and specificity. Adhesion to management protocol might lessen surgery for benign lesions.

Dose exposure in the ITALUNG trial of lung cancer screening with low-dose CT

Few data are available on the effective dose received by participants in lung cancer screening programmes with low-dose CT (LDCT). We report the collective effective dose delivered to 1406 current or former smokers enrolled in the ITALUNG trial who completed 4 annual LDCT examinations and related further investigations including follow-up LDCT, 2-[(18)F]flu-2-deoxy-d-glucose positron emission tomography (FDG-PET) or CT-guided fine needle aspiration biopsy (FNAB). Using the air CT dose index and Monte Carlo simulations on an anthropomorphic phantom, the whole-body effective dose associated with LDCT was determined for the eight CT scanners used in the trial. A value of 7 mSv was assigned to FDG-PET while the measured mean effective dose of CT-guided FNAB was 1.5 mSv. The mean collective effective dose in the 1406 subjects ranged between 8.75 and 9.36 Sv and the mean effective dose to the single subject over 4 years was between 6.2 and 6.8 mSv (range 1.7-21.5 mSv) according to the cranial-caudal length of the LDCT volume. 77.4% of the dose was owing to annual LDCT and 22.6% to further investigations. Considering the nominal risk coefficients for stochastic effects after exposure to low-dose radiation according to the National Radiological Protection Board, International Commission on Radiological Protection (ICRP) 60, ICRP103 and Biological Effects of Ionizing Radiation VII, the mean number of radiation-induced cancers ranged between 0.12 and 0.33 per 1000 subjects. The individual effective dose to participants in a 4-year lung cancer screening programme with annual LDCT is very low and about one-third of the effective dose that is associated with natural background radiation and diagnostic radiology in the same time period.

Defining the Intra-subject Variability of Whole-lung CT Densitometry in Two Lung Cancer Screening Trials

To define a statistically based variation of individual whole-lung densitometry above which a real increase of pulmonary extent can be suspected in lung cancer screening trials. Baseline and 3-month follow-up low-dose computed tomography (LDCT) examinations of 131 smokers or former smokers recruited in the ITALUNG (32 subjects) and MILD (99 subjects) trials were compared using for each data set two different image processing tools for whole-lung densitometry. Both trials were approved by institutional review boards, and written informed consent was obtained from all participants. Assuming that no change of emphysema extent can occur in a 3-month interval, the Bland and Altman method was used to assess the agreement between baseline and follow-up LDCT examinations for lung volume, 15th percentile (Perc15) of lung density and Perc15 corrected for lung volume by application of a linear detrend on log-transformed data. Similar results were obtained in each data set using two different image processing tools. In the ITALUNG cohort the 95% limits of agreement (LoA) interval of volume corrected Perc15 was -9.7 to 10.7% using image processing method 1 and -10.3 to 11.5% using image processing method 2. In the MILD cohort, the 95% LoA interval of volume corrected Perc15 was -14.7 to 17.3% with both image processing methods. In the two considered lung cancer screening settings a range of 9.7-14.7% decrease of volume corrected Perc15 represents a statistically defined threshold to suspect a real increase of emphysema extent in serial LDCT examinations.