Low-dose CT screening using hybrid iterative reconstruction: confidence ratings of diagnoses of simulated lesions other than lung cancer

Abstract

Objective: To evaluate the confidence ratings of diagnoses of simulated lesions other than lung cancer on low-dose screening CT with hybrid iterative reconstruction (IR). Methods: Simulated lesions (emphysema, mediastinal masses and interstitial pneumonia) in a chest phantom were scanned by a 320-row area detector CT. The scans were performed by 64-row and 160-row helical scans at various dose levels and were reconstructed by filtered back projection (FBP) and IR. Emphysema, honeycombing and reticular opacity were visually scored on a four-point scale by six thoracic radiologists. The ground-glass opacity as a percentage of total lung volume (%GGO), CT value and contrast-to-noise ratio (CNR) of mediastinal masses were calculated. These scores and values were compared between FBP and IR. Wilcoxon's signed-rank test was used (p , 0.05). Interobserver agreements were evaluated by k statistics.Results: There were no significant differences in visual assessment. Interobserver agreement was almost perfect. CT values were almost equivalent between FBP and IR, whereas CNR with IR was significantly higher than that with FBP. %GGO significantly increased at low-dose levels with FBP; however, IR suppressed the elevation. Conclusion: The confidence ratings of diagnoses of simulated lesions other than lung cancer on low-dose CT screening were not degraded with hybrid IR compared with FBP. Advances in knowledge: Hybrid IR did not degrade the confidence ratings of diagnoses on visual assessment and differential diagnoses based on CT value of mediastinal masses, and it showed the advantage of higher GGO conspicuity at low-dose level. Radiologists can analyse images of hybrid IR alone on low-dose CT screening for lung cancer. INTRODUCTIONRecently, there have been discussions regarding the efficacy of lung cancer screening using low-dose CT. For example, the National Lung Screening Trial research team's 1 randomized clinical trial comparing the efficacies of chest radiographs and low-dose CT. They found that lung cancer screening using low-dose CT reduces lung cancer-related mortality in groups at high risk of lung cancer. With regard to dose-reduction techniques in CT, a new method of image reconstruction, iterative reconstruction (IR), has been developed and is now widely used for various clinical purposes. This technique has an advantage over the filtered back projection (FBP) method of image reconstruction in that FBP contains quantum noise; IR reduces this quantum noise by repeatedly comparing projection data, including quantum noise or primary reconstruction image data, with ideal anatomical and statistical models.

Balancing act between quantitative and qualitative image quality between nonionic iodinated dimer and monomer at various vessel sizes during computed tomography: a phantom study

“…Interestingly, Iodixanol demonstrated superior CNR levels compared to Iohexol at 200 and 400 mAs where no difference between both ICM was noted at 350 mAs. Previous studies have demonstrated that IR application provides a reduction in image noise and an increase in CNR compared to FBP [25][26][27][28]. In our study, no significant difference in image noise and phantom opacification was noted when employing FBP, MBIR and MBIR.…”

Low-dose CT in COVID-19 outbreak: radiation safety, image wisely, and image gently pledge

“…Sakai et al used simulated GGO and reticular Conventional CT chest protocol in the same patient would result in DLP of 264.55 mGy × cm and CTDIvol of 5.92 mGy, which means that low-dose protocol decreased the radiation dose to about 50% without a significant impact on the diagnostic value. (CT protocol: 100 kVp, 50 mAs, 0.5 s without iterative reconstruction) opacity lesions and implemented them inside the apex and lower lobe of the lung [30]. They obtained LDCT images using the IR method in various levels of radiation dose and compared it with filtered back projection (FBP) method which is widely used in scanners.…”

Low-Dose CT for Lung Cancer Screening

“…Several studies have demonstrated that IR techniques help improve image quality and retain diagnostic value of LDCT at substantially reduced radiation dose [6][7][8].…”