The investigation of solitary pulmonary nodule (SPN) and non-small cell lung cancer (NSCLC) has rapidly become one of the main indications for F-fluorodeoxyglucose (FDG) positron emission tomography (PET), currently combined with computed tomography (PET-CT). In this literature review, we first attempt to clarify how PET imaging contributes to investigating SPN, in conjunction with conventional CT. We highlight the prospects of research underway to improve our understanding of SPN. In the second part of this review, we analyze the current role of PET-CT in the overall care process for lung cancer. We review the indications for which consensus has been reached, for example initial staging, as well as new indications such as radiation therapy planning or prognostic assessment.

Background The role and performance of chest CT in the diagnosis of the coronavirus disease 2019 (COVID-19) pandemic remains under active investigation. Purpose To evaluate the French national experience using Chest CT for COVID-19, results of chest CT and RT-PCR were compared together and with the final discharge diagnosis used as reference standard. Materials and Methods A structured CT scan survey (NCT04339686) was sent to 26 hospital radiology departments in France between March 2 and April 24 2020. These dates correspond to the peak of the national COVID-19 epidemic. Radiology departments were selected to reflect the estimated geographical prevalence heterogeneities of the epidemic. All symptomatic patients suspected of having a COVID-19 pneumonia who underwent within 48 hours both initial chest CT and at least one RT-PCR testing were included. The final discharge diagnosis, based on multiparametric items, was recorded. Data for each center were prospectively collected and gathered each week. Test efficacy was determined by using Mann-Whitney Test, Student’s t-test, Chi-square test and Pearson’s correlation. A p value <.05 determined statistical significance. Results Twenty-six of 26 hospital radiology departments responded to the survey with 7500 patients entered; 2652 did not have RT-PCR results or had unknown or excess delay between RT-PCR and CT. After exclusions, 4824 patients (mean age 64, ± 19 yrs, 2669 males) were included. Using final diagnosis as the reference, 2564 of the 4824 patients were positive for COVID-19 (53%). Sensitivity, specificity, NPV and PPV of chest CT for diagnosing COVID-19 were 2319/2564 (90%, 95% confidence interval [CI]: 89, 91), 2056/2260 (91%, 95%CI: 91, 92%), 2056/2300 (89%, 95%CI; 87, 90%) and 2319/2524 (92%, 95%CI 91, 93%) respectively. There was no significant difference for chest CT efficacy among the 26 geographically separate sites, each with varying amounts of disease prevalence. Conclusion Use of chest CT for the initial diagnosis and triage of suspected COVID-19 patients was successful.

DiscussionAlthough each DWI-ASPECTS point corresponded to a wide range of Vol DWI , all patients with extensive changes on DWI-ASPECTS (0-3) had large Vol DWI , whereas all patients with limited DWI-ASPECTS changes (≥7) had Vol DWI <70 mL.DWI-ASPECTS is increasingly used for description or prognostic purposes in stroke populations. Although not designed to substitute for Vol DWI , DWI-ASPECTS does provide some semiquantitative estimate of it. However, DWI-ASPECTS overlooks lesions within the striatocapsular region and only partially covers the middle cerebral artery territory. This explains the wide range of true lesion volumes for a given DWI-ASPECTS point found here, in line with other studies. 2,7 Our finding that DWI-ASPECTS <4 invariably predicted Vol DWI ≥93 mL is entirely consistent with 1 previous report 7 and highly relevant to the Diffusion and perfusion imaging Evaluation For Understanding Stroke Evolution (DEFUSE)-2 malignant profile 100 mL cut point. 4 However, patients with DWI-ASPECTS ≥7 all had Vol DWI <70 mL, which corresponds to the cut point incorporated in the target mismatch definition.4 Although debated, 11 these volume cut-offs are proposed to identify poor or good responders to reperfusion therapy, 4 and particularly the 100-mL cut point serves as an exclusion criterion in several ongoing trials. However, fully automated softwares to calculate Vol DWI are not yet commonly used and can fail in real time. This may lead to imbalanced groups on baseline characteristics in trials where randomization is based on automated MR-image segmentation.14 Failure of automated volumetry may also restrain patient's inclusion in trials. To overcome these difficulties, DWI-ASPECTS <4 could replace the poorly reproducible greater than one third of the middle cerebral artery territory CT rule as an alternative exclusion criterion in MR-based trials.The tight relationships between extreme DWI-ASPECTS values (ie, <4 or ≥7) and the >100-or <70-mL, respectively, cut points found here suggest that DWI-ASPECTS could serve as a surrogate for these volumes. This concerned almost 3 quarters (241/330) of the studied population and may have clinical relevance. However, in those patients with intermediate DWI-ASPECTS (4-6), Vol DWI straddled widely across the above cut point volumes, indicating that intermediate DWI-ASPECTS cannot substitute for Vol DWI to identify patients with target mismatch or malignant profile. Of note, no DWI-ASPECTS cut point identified lesion volume >145 mL, 15 above witch decompressive hemicraniectomy is indicated.Limitations of our study include its retrospective and single-center nature, and the focus on patients who underwent thrombolysis, which limits generalizability to nonthrombolized patients and may, in part, explain the low proportion of patients with large Vol DWI and consequently the relative large 95% confidence interval for patients with low ASPECTS.In conclusion, in the first 6 hours, each DWI-ASPECTS point corresponds to a wide range of Vol DWI . However, extreme DWI-ASPECTS scor...