Vol.:(0123456789) 1 3 La radiologia medica https://doi.org/10.1007/s11547-020-01139-5 CHEST RADIOLOGY Image quality and radiation dose reduction in chest CT in pulmonary infection Massimo Cristofaro 1  · Elisa Busi Rizzi 1  · Pierluca Piselli 2  · Elisa Pianura 1  · Ada Petrone 1  · Nicoletta Fusco 1  · Federica Di Stefano 1  · Vincenzo Schinina’ 1 Received: 3 May 2019 / Accepted: 16 January 2020 © Italian Society of Medical Radiology 2020 Abstract Purpose To evaluate the efect of dose reduction with iterative reconstruction (IR) on image quality of chest CT scan com- paring two protocols. Materials and methods Fifty-nine patients were enrolled. The two CT protocols were applied using Iterative Reconstruc- tion (ASIR™) 40% but diferent noise indexes, recording dose-length product (DLP) and volume computed tomography dose index (CTDI vol ). The subjective IQ was rated based on the distinction of anatomic details using a 4-point Likert scale based on the European Guidelines on Quality Criteria for CT. For each patient, two single CTs, at enrollment (group 1) and at follow-up after lowering the dose (group 2), were evaluated by two radiologists evaluating, for each examination, fve diferent lung regions (central zone—CZ; peripheral zone—PZ; sub-pleural region—SPR; centrilobular region—CLR; and apical zone—AZ). An inter-observer agreement was expressed by weighted Cohen’s kappa statistics (k) and intra-individual diferences of subjective image analysis through visual grading characteristic (VGC) analysis. Results An average 50.4% reduction in CTDI vol and 51.5% reduction in DLP delivered were observed using the dose-reduced protocol. An agreement between observers evaluating group 1 CTs was perfect (100%) and moderate to good in group 2 examinations (k-Cohen ranging from 0.56 for PZ and AZ to 0.70 for SPR). In the VGC analysis, image quality ratings were signifcantly better for group 1 than group 2 scans for all regions (AUC VGC ranging from 0.56 for CZ to 0.62). However, disagreement was limited to a score 4 (excellent)-to-score 3 (good) IQ transition; apart from a single case in PZ, both the observers scored the IQ at follow-up as 2 (sufcient) starting from a score 4 (excellent). Conclusion Dose reduction achieved in the follow-up CT scans, although a lower IQ still allows a good diagnostic confdence. Keywords Chest · Computerized tomography · Iterative reconstruction · Image quality · Radiation dose Introduction In the past decades, the average annual per capita efective dose from medicine has approximately doubled worldwide [1–4]. Computed tomography (CT) examinations are associ- ated with absorbed doses much higher than conventional radiology, and although they account approximately for 17% of the total number of medical radiation-based procedures, they contribute to 50% of the overall dose delivered to the population [5–7]. Although, in the past, the literature estimates that between 0.7 and 2% of new cancer cases in the USA each year can be attributed exclusively to CT scanning [8, 9], nowadays several studies stated that the risk is defnitely lower and is needed to provide more robust analysis in defning the can- cer risks potentially induced by CT scans [10–13]. Therefore, it is understood that frst of all CT studies must be performed tailoring examinations in an appropriate clinical setting, there is a remarkable technologic efort to decrease the radiation dose during justifed CT scanning “as low as reasonably achievable” [14–17], and furthermore, we must keep in mind that some subjects often required * Pierluca Piselli pierluca.piselli@inmi.it 1 Radiology Unit, National Institute for Infectious Diseases “L. Spallanzani” IRCCS, Via Portuense 292, 00149 Rome, Italy 2 Clinical Epidemiology Unit, National Institute for Infectious Diseases “L. Spallanzani” IRCCS, Via Portuense 292, 00149 Rome, Italy