In routine dose, non-enhanced chest CT, ASIR-V shows greater potential in reducing image noise and artefacts and maintaining image sharpness when compared to the recommended level of 40%ASIR algorithm. Combining both the objective and subjective evaluation of images, non-enhanced chest CT images reconstructed with 60% ASIR-V have the highest image quality. Advances in knowledge: This is the first clinical study to evaluate the clinical value of ASIR-V in the same patients using the same CT scanner in the non-enhanced chest CT scans. It suggests that ASIR-V provides the better image quality and higher diagnostic confidence in comparison with ASIR algorithm.
Objective: To evaluate the clinical value of low-dose chest CT combined with the new generation adaptive statistical iterative reconstruction (ASIR-V) algorithm in the diagnosis of pulmonary nodule. Methods: 30 patients with pulmonary nodules underwent chest CT using Revolution CT. The patients were first scanned with standard-dose at a noise index (NI) of 14, and the images were reconstructed with filtered back projection (FBP) algorithm. If pulmonary nodules were found, a low-dose targeted scan, with NI of 24, was performed localized on the nodules, and the images were reconstructed with 60% ASIR-V. The detection rate of pulmonary nodules in the two scanning modes was recorded. The size of nodules, CT value and standard deviation of nodules were measured. The signal-to-noise ratio and contrast-to-noise ratio were also calculated. Two experienced radiologists used a 5-point method to score the image quality. The volumetric CT dose index, and dose–length product were recorded and the effective dose (ED) was calculated of the two scanning modes. Results: Volumetric CT dose index (ED) of the standard-dose scan covering the entire lungs was 7.29 ± 2.38 mGy (3.52 ± 1.09 mSv), and that of low-dose targeted scan was 2.56 ± 1.87 mGy (0.51 ± 0.32 mSv). However, the ED of the virtual low-dose scan for the entire lungs was 1.44 ± 0.15 mSv, which would mean a dose reduction of 59.1% compared with the standard-dose scan. 85 of the 87 pulmonary nodules were detected in the low-dose targeted scan, with 2 of the ground-glass density nodules with size less than 1 cm missed, resulting in 97.7% overall detection rate. There was no difference between the low-dose ASIR-V images and standard-dose FBP images for the size (1.49 ± 0.74 cm vs 1.48 ± 0.75 cm), CT value [33.02 ± 1.95 Hounsfield unit (HU) vs 34.6 ± 3.07 HU], standard deviation (27.64 ± 14.42 HU vs 30.38 ± 20.04 HU), signal-to-noise ratio (1.44 ± 0.88 vs 1.43 ± 1.31) and contrast-to-noise ratio (38.95 ± 18.43 vs 38.23 ± 14.99) of nodules (all p > 0.05). There was no difference in the subjective scores between the two scanning modes. Conclusion: The low-dose CT scan combined with ASIR-V algorithm is of comparable value in the detection and the display of pulmonary nodules when compared with the FBP images obtained by standard-dose scan. Advances in knowledge: This is a clinical study to evaluate the clinical value of pulmonary nodules using ASIR-V algorithm in the same patients in the low-dose chest CT scans. It suggests that ASIR-V provides similar image quality and detection rate for pulmonary nodules at much reduced radiation dose.
To the editor Carcinoma of the lung is the leading cause of cancerassociated death and the second most common carcinoma following breast cancer worldwide according to global cancer statistics for 2020. 1 It is reported that 2 206 771 new lung cancer cases and 1 796 144 lung cancer deaths were estimated globally in 2020. 1 Lung cancer is the first cause of cancer-related death followed by colorectal cancer. 2 Small-cell lung cancer (SCLC), one of the two main types of lung carcinoma, accounts for 15%-20% of all lung cancers and has poor prognosis due to advanced stages when first diagnosis. 3 However, about 5% of SCLC cases were at early stages (T1-2N0M0) when first diagnosed, which may be a result of lung cancer early screening projects for highrisk individuals and routine physical examination. Because of the potential to cure early stages of SCLC (T1-2N0M0), operations such as lobectomy and mediastinal lymph nodes sampling are recommended according to the current SCLC treatment guidelines for operable cases. For inoperable cases, concurrent chemoradiation is recommended according to literature. However, the toxicity of the concurrent chemoradiation modality is severe and risk of grade 3-5 treatment-related toxicity is high.Recent studies have indicated that stereotactic ablative radiotherapy (SABR) is not inferior to conventional radiation in the aspects of local control or survival, and is even comparable to operation for early-stage non-small-cell lung cancer (NSCLC). 4 SABR in the treatment of early stage (T1-2N0M0) SCLC has been also investigated in recent clinical studies, has demonstrated satisfactory outcomes, and is recommended by American Society for Radiation Oncology (ASTRO) Clinical Practice Guidelines. 5 However, the ASTRO guidelines were based on single-arm small sample size clinical studies with limited statistical power and weak evidence. Safavi and his colleagues 6 have therefore performed a comprehensive metaanalysis relevant to SABR in T1-2N0M0 SCLC by combining 11 clinical studies, including 399 early-stage cases, on aspects of local control, overall survival, 1-year survival, 2-year survival, recurrence and treatment toxicity. The authors found that SABR for inoperable early-stage, node-negative SCLC was effective for local control and the treatment toxicity was limited and acceptable. The statistical power of SABR for
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