The Impact of Iterative Reconstruction in Low-Dose Computed Tomography on the Evaluation of Diffuse Interstitial Lung Disease

Abstract

ObjectiveTo evaluate the impact of iterative reconstruction (IR) on the assessment of diffuse interstitial lung disease (DILD) using CT.Materials and MethodsAn American College of Radiology (ACR) phantom (module 4 to assess spatial resolution) was scanned with 10–100 effective mAs at 120 kVp. The images were reconstructed using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), with blending ratios of 0%, 30%, 70% and 100%, and model-based iterative reconstruction (MBIR), and their spatial resolution was objectively assessed by the line pair structure method. The patient study was based on retrospective interpretation of prospectively acquired data, and it was approved by the institutional review board. Chest CT scans of 23 patients (mean age 64 years) were performed at 120 kVp using 1) standard dose protocol applying 142–275 mA with dose modulation (high-resolution computed tomography [HRCT]) and 2) low-dose protocol applying 20 mA (low dose CT, LDCT). HRCT images were reconstructed with FBP, and LDCT images were reconstructed using FBP, ASIR, and MBIR. Matching images were randomized and independently reviewed by chest radiologists. Subjective assessment of disease presence and radiological diagnosis was made on a 10-point scale. In addition, semi-quantitative results were compared for the extent of abnormalities estimated to the nearest 5% of parenchymal involvement.ResultsIn the phantom study, ASIR was comparable to FBP in terms of spatial resolution. However, for MBIR, the spatial resolution was greatly decreased under 10 mA. In the patient study, the detection of the presence of disease was not significantly different. The values for area under the curve for detection of DILD by HRCT, FBP, ASIR, and MBIR were as follows: 0.978, 0.979, 0.972, and 0.963. LDCT images reconstructed with FBP, ASIR, and MBIR tended to underestimate reticular or honeycombing opacities (-2.8%, -4.1%, and -5.3%, respectively) and overestimate ground glass opacities (+4.6%, +8.9%, and +8.5%, respectively) compared to the HRCT images. However, the reconstruction methods did not differ with respect to radiologic diagnosis.ConclusionThe diagnostic performance of LDCT with MBIR was similar to that of HRCT in typical DILD cases. However, caution should be exercised when comparing disease extent, especially in follow-up studies with IR.

Dynamic Changes of Chest CT Follow-up In Coronavirus Disease-19 (COVID-19) Pneumonia: Relationship To Clinical Typing

“…Although the radiation dose has been reduced by low dose technology, iterative algorithm, care dose, and reduction of tube voltage [23,24], appropriate CT follow-up interval can help reduce the radiation dose. Therefore, the frequency of CT follow-up should be decreased by prolonging the interval time in the late stage of severe and critical type and the early stage of moderate type.…”

Quantitative Image Quality and Histogram-Based Evaluations of an Iterative Reconstruction Algorithm at Low-to-Ultralow Radiation Dose Levels: A Phantom Study in Chest CT

“…Recently, several studies ( 34 35 36 ) also reported degradation of image quality of CT with an IR algorithm at low radiation dose. When image quality of CT images with IR was evaluated by using an American College of Radiology CT accreditation phantom, SNR improvement was decreased below a CTDI vol of 1.42 mGy ( 34 ) almost equivalent to the 60%-reduced radiation dose (1.4 mGy) that began to demonstrate image quality degradation in our study, high-contrast resolution was decreased between 6 line pairs/cm and 7 line pairs/cm under 120 kVp and 10 mA ( 35 ), and low-contrast resolution was sacrificed at dose reduction of 25% or more ( 36 ). Of interest, Infante et al ( 34 ) showed that the adverse effect of low dose on SNR of SAFIRE images was most pronounced for strengths of 3 and 5 and least pronounced with a strength of 1, which was exactly consistent with the findings demonstrated by our study.…”

A Comparative Study of Target Reconstruction of Ultra-High-Resolution CT for Patients with Corona-Virus Disease 2019 (COVID-19)

“…In addition, iterative reconstruction techniques can also reduce SD and improve SNR [16][17]. However, the reconstruction speed will be slower with higher iDose 4 iteration level, and the densities of the lesion and normal tissues tend to become homogeneous, which affects the observation of the internal structure of the lesion [18].…”