Combining Automatic Tube Current Modulation with Adaptive Statistical Iterative Reconstruction for Low-Dose Chest CT Screening

Abstract

ObjectiveTo reduce radiation dose while maintaining image quality in low-dose chest computed tomography (CT) by combining adaptive statistical iterative reconstruction (ASIR) and automatic tube current modulation (ATCM).MethodsPatients undergoing cancer screening (n = 200) were subjected to 64-slice multidetector chest CT scanning with ASIR and ATCM. Patients were divided into groups 1, 2, 3, and 4 (n = 50 each), with a noise index (NI) of 15, 20, 30, and 40, respectively. Each image set was reconstructed with 4 ASIR levels (0% ASIR, 30% ASIR, 50% ASIR, and 80% ASIR) in each group. Two radiologists assessed subjective image noise, image artifacts, and visibility of the anatomical structures. Objective image noise and signal-to-noise ratio (SNR) were measured, and effective dose (ED) was recorded.ResultsIncreased NI was associated with increased subjective and objective image noise results (P<0.001), and SNR decreased with increasing NI (P<0.001). These values improved with increased ASIR levels (P<0.001). Images from all 4 groups were clinically diagnosable. Images with NI = 30 and 50% ASIR had average subjective image noise scores and nearly average anatomical structure visibility scores, with a mean objective image noise of 23.42 HU. The EDs for groups 1, 2, 3 and 4 were 2.79±1.17, 1.69±0.59, 0.74±0.29, and 0.37±0.22 mSv, respectively. Compared to group 1 (NI = 15), the ED reductions were 39.43%, 73.48%, and 86.74% for groups 2, 3, and 4, respectively.ConclusionsUsing NI = 30 with 50% ASIR in the chest CT protocol, we obtained average or above-average image quality but a reduced ED.

Ultralow-dose CT with tin filtration for detection of solid and sub solid pulmonary nodules: a phantom study

“…19 Chen et al 10 evaluated automated tube current modulation in combination with adaptive statistical IR and found that it was possible to reduce the effective radiation dose of chest CT down to 0.74 mSv while maintaining a reasonable image quality. 10 Gordic et al 3 used a single-energy protocol with tin filtration and ADMIRE ex vivo for the detection of solid pulmonary nodules and were able to lower effective radiation doses further down to 0.06 mSv. By contrast, our study indicates that reduction of effective dose is possible down to 0.14 mSv while high detection of both nodule entities is guaranteed.…”

“…The studies mentioned above 3,10,19 altogether conclude that IR techniques have the potential to significantly reduce radiation dose while maintaining image quality. However, IR techniques Iterative reconstruction (IR).…”

Achievable dose reduction using iterative reconstruction for chest computed tomography: A systematic review

“…IR at reduced dose compared to FBP at local reference dose led to worse image quality in two studies (11%), whereas image quality remained the same (5 studies, 26%) or improved in most studies (12 studies, 63%). The study of Chen et al [32] and Li et al [35] reported a decrease in objective image quality which both used a relatively large dose reduction of 87% and 71% respectively. At reduced dose level, objective image quality improved in all fourteen studies with IR compared to FBP [13,20,31].…”

“…IR at reduced dose compared to FBP at local reference dose resulted in improved (1 study, 6%), the same (14 studies, 78%) or worse (3 studies, 17%) image quality. Two studies reporting a decrease in subjective image quality used a very low dose namely 0.36 [32] and 0.11 mSv [6]. The third study investigated radiologists' preference and reported that radiologists preferred local reference dose images reconstructed with FBP over reduced dose images reconstructed with IR [24].…”

SPECT/CT radiation dosimetry

“…It has been found that ATCM, ATVS, and IR algorithms work even better together, allowing greater dose reductions in examinations of the chest [62][63][64], abdomen [62,65], pelvis [65], and in coronary CT [66].…”