[Low-dose helical CT projection data restoration using noise estimation]

OBJECTIVE

To build a helical CT projection data restoration model at random low-dose levels.

METHODS

We used a noise estimation module to achieve noise estimation and obtained a low-dose projection noise variance map, which was used to guide projection data recovery by the projection data restoration module. A filtering back-projection algorithm (FBP) was finally used to reconstruct the images. The 3D wavelet group residual dense network (3DWGRDN) was adopted to build the network architecture of the noise estimation and projection data restoration module using asymmetric loss and total variational regularization. For validation of the model, 1/10 and 1/15 of normal dose helical CT images were restored using the proposed model and 3 other restoration models (IRLNet, REDCNN and MWResNet), and the results were visually and quantitatively compared.

RESULTS

Quantitative comparisons of the restored images showed that the proposed helical CT projection data restoration model increased the structural similarity index by 5.79% to 17.46% compared with the other restoration algorithms (P < 0.05). The image quality scores of the proposed method rated by clinical radiologists ranged from 7.19% to 17.38%, significantly higher than the other restoration algorithms (P < 0.05).

CONCLUSION

The proposed method can effectively suppress noises and reduce artifacts in the projection data at different low-dose levels while preserving the integrity of the edges and fine details of the reconstructed CT images.

From focal pulmonary pure ground-glass opacity nodule detected by low-dose computed tomography into invasive lung adenocarcinoma: A growth pattern analysis in the elderly

Background

Elderly patients are under‐represented in studies of pure ground‐glass opacity (pGGO) nodules; thus, this study analyzed the growth pattern and clinical outcomes of pGGO nodules in the elderly in order to help make treatment decisions.

Methods

We retrospectively reviewed patients aged over 60 years with screening‐detected and pathologically confirmed growing focal pGGO nodules.

Results

During the study period, 858 subjects had undergone at least three low‐dose computed tomography scans in our center. Twenty patients were treated for growing focal pGGO nodules. The median age at detection was 66 years (range: 60–80). The median time to an increase of at least 2 mm was 348 days (range: 98–1527) and to develop a solid portion, 1141 days (range: 480–3010). Seven patients had surgery for increased nodule size, four had surgery immediately after the solid portion appeared, and nine were treated after a median follow‐up of 1153 days (range: 240–2342) since the solid portion developed. The median size of the solid component was 8 mm (2–13) before surgery. No recurrence was observed after a median follow‐up of 41 months. Pathology revealed adenocarcinoma in situ in five patients, and minimally invasive or invasive adenocarcinoma in the remainder. The appearance of a solid portion was significantly associated with invasive adenocarcinoma compared to increased size alone (100% vs. 44.4%; P = 0.005).

Conclusions

pGGO nodules had an indolent growth pattern and good prognosis in our patient sample, even after the appearance of a solid portion. Therefore, minimally invasive surgery after the development of a solid component may be an option for the elderly.

Use of lung cancer screening tests in the United States: results from the 2010 National Health Interview Survey

BACKGROUND

Before evidence of efficacy, lung cancer screening was being ordered by many physicians. The National Lung Screening Trial (NLST), which showed a 20% reduction in lung cancer mortality among those randomized to receive low-dose computed tomography (LDCT), will likely lead to increased screening use.

METHODS

We estimated the prevalence of chest X-ray and CT use in the United States using data from the 2010 National Health Interview Survey (NHIS). Subjects included 15,537 NHIS respondents aged ≥40 years without prior diagnosis of lung cancer. Estimates of the size of the U. S. population by age and smoking status were calculated. Multivariate logistic regression examined predictors of test use adjusting for potential confounders.

RESULTS

Twenty-three percent of adults reported chest X-ray in the previous year and 2.5% reported chest X-ray specifically to check for lung cancer; corresponding numbers for chest CT were 7.5% and 1.3%. Older age, black race, male gender, smoking, respiratory disease, personal history of cancer, and having health insurance were associated with test use. Approximately, 8.7 million adults in the United States would be eligible for LDCT screening according to NLST eligibility criteria.

CONCLUSIONS AND IMPACT

Monitoring of trends in the use of lung screening tests will be vital to assess the impact of NLST and possible changes in lung cancer screening recommendations and insurance coverage in the future. Education of patients by their physicians, and of the general public, may help ensure that screening is used appropriately, in those most likely to benefit.