Local ablation for hepatocellular carcinoma (HCC), a non-surgical option that directly targets and destroys tumor cells, has advanced significantly since the 1990s. Therapies with different energy sources, such as radiofrequency ablation, microwave ablation, and cryoablation, employ different mechanisms to induce tumor necrosis. The precision, safety, and effectiveness of these therapies have increased with advances in guiding technologies and device improvements. Consequently, local ablation has become the first-line treatment for early-stage HCC. The lack of organized evidence and expert opinions regarding patient selection, pre-procedure preparation, procedural methods, swift post-treatment evaluation, and follow-up has resulted in clinicians following varied practices. Therefore, an expert consensus-based practical recommendation for local ablation was developed by a group of experts in radiology and hepatology from the Research Committee of the Korean Liver Cancer Association in collaboration with the Korean Society of Image-guided Tumor Ablation to provide useful information and guidance for performing local ablation and for the pre- and post-treatment management of patients.

Objective: To investigate the potential association among preoperative breast MRI features, axillary nodal burden (ANB), and disease-free survival (DFS) in patients with early-stage breast cancer. Materials and Methods: We retrospectively reviewed 297 patients with early-stage breast cancer (cT1-2N0M0) who underwent preoperative MRI between December 2016 and December 2018. Based on the number of positive axillary lymph nodes (LNs) determined by postoperative pathology, the patients were divided into high nodal burden (HNB; ≥3 positive LNs) and non-HNB (<3 positive LNs) groups. Univariable and multivariable logistic regression analyses were performed to identify independent risk factors associated with ANB. Predictive efficacy was evaluated using the receiver operating characteristic (ROC) curve and area under the curve (AUC). Univariable and multivariable Cox proportional hazards regression analyses were performed to determine preoperative features associated with DFS. Results: We included 47 and 250 patients in the HNB and non-HNB groups, respectively. Multivariable logistic regression analysis revealed that multifocality/multicentricity (adjusted odds ratio [OR] = 3.905, 95% confidence interval [CI]: 1.685-9.051, P = 0.001) and peritumoral edema (adjusted OR = 3.734, 95% CI: 1.644-8.479, P = 0.002) were independent risk factors for HNB. Combined peritumoral edema and ultifocality/multicentricity achieved an AUC of 0.760 (95% CI: 0.707-0.807) for predicting HNB, with a sensitivity and specificity of 83.0% and 63.2%, respectively. During the median follow-up period of 45 months (range, 5-61 months), 26 cases (8.75%) of breast cancer recurrence were observed. Multivariable Cox proportional hazards regression analysis indicated that younger age (adjusted hazard ratio [HR] = 3.166, 95% CI: 1.200-8.352, P = 0.021), larger tumor size (adjusted HR = 4.370, 95% CI: 1.671-11.428, P = 0.002), and multifocality/multicentricity (adjusted HR = 5.059, 95% CI: 2.166-11.818, P < 0.001) were independently associated with DFS. Conclusion: Preoperative breast MRI features may be associated with ANB and DFS in patients with early-stage breast cancer.

Objective: Dual-layer CT (DLCT) can create virtual monochromatic images (VMIs) at various monochromatic X-ray energies, particularly at low keV levels, with high contrast-to-noise ratio. The purpose of this study was to assess the clinical feasibility of contrast-enhanced chest DLCT with a low keV VMI for preoperative breast cancer staging, in comparison to breast MRI. Materials and Methods: A total of 152 patients with 155 index breast cancers were enrolled in the study. VMIs were generated from contrast-enhanced chest DLCT at 40 keV and maximum intensity projection (MIP) with three-dimensional (3D) reconstruction was performed for both bilateral breast areas. Two radiologists reviewed in consensus the 3D MIP images of the chest DLCT with VMI and breast MRI in separate sessions with a 3-month wash-out period. The detection rate and mean tumor size of the index cancer were compared between the chest DLCT with VMI and breast MRI. Additionally, the agreement of tumor size measurement between the two imaging modalities were evaluated. Results: Of all index cancers, 84.5% (131/155) were detected in the chest DLCT with VMI, while 88.4% (137/155) were detected in the breast MRI (P = 0.210). The Bland-Altman agreement between the chest DLCT with VMI and breast MRI was a mean difference of -0.05 cm with 95% limits of agreement of -1.29 to 1.19 cm. The tumor size in the chest DLCT with VMI (2.3 ± 1.7 cm) was not significantly different from that in the breast MRI (2.4 ± 1.6 cm) (P = 0.106). Conclusion: The feasibility of chest DLCT with VMI was demonstrated for preoperative tumor staging in breast cancer patients, showing comparable cancer detectability and good agreement in tumor size measurement compared to breast MRI. This suggests that chest DLCT with VMI can serve as a potential alternative for patients who have contraindications to breast MRI.

Autoimmune encephalitis (AE) is a category of immune-mediated disorders of the central nervous system (CNS) affecting children and adults. It is characterized by the subacute onset of altered mentation, neurocognitive issues, refractory seizures/drug-resistant epilepsy, movement disorders, and/or autonomic dysfunction. AE is mediated by autoantibodies targeting specific surface components or intracytoplasmic antigens in the CNS, leading to functional or structural alterations. Multiple triggers that induce autoimmunity have been described, which are mainly parainfectious and paraneoplastic. The imaging features of AE often overlap with each other and with other common causes of encephalitis/encephalopathy (infections and toxic-metabolic etiologies). Limbic encephalitis is the most common imaging finding shared by most of these entities. Cortical, basal ganglia, diencephalon, and brainstem involvement may also be present. Cerebellar involvement is rare and is often a part of paraneoplastic degeneration. Owing to an improved understanding of AE, their incidence and detection have increased. Hence, in an appropriate setting, a high degree of suspicion is crucial when reporting clinical MRIs to ensure prompt treatment and better patient outcomes. In this review, we discuss the pathophysiology of AE and common etiologies encountered in clinical practice.

Objective: To determine the preventive effect of changing gadolinium-based contrast agents (GBCAs) to reduce the recurrence of GBCA-associated acute adverse drug reactions (ADRs). Materials and Methods: This retrospective, observational, single-center study-conducted between January 2016 and December 2021-included 238743 consecutive GBCA-enhanced MRI examinations. We focused on a subgroup of patients who experienced acute GBCA-associated ADRs during any of these examinations and subsequently underwent follow-up GBCA-enhanced MRI examinations up until July 2023. The follow-up examinations involved either the same (non-change group) or different (change group) GBCAs compared to the ones that initially caused the acute ADR. Baseline participant characteristics, generic profile of the GBCAs, administration of premedication, history of prior ADR to iodinated contrast media, and symptoms of GBCA-associated acute ADRs were retrospectively analyzed. Multivariable logistic regression with generalized estimating equations and propensity score matching were used. Results: A total of 1042 instances of acute ADRs (0.44%; 95% confidence interval [CI]: 0.41%-0.46%) were reported. Three-hundred and seventy-three patients underwent GBCA-enhanced MRI examinations after experiencing GBCA-associated acute ADRs within the study period; 31.9% (119/373) reexperienced acute ADRs at any of the follow-up examinations. The ADR recurrence was significantly lower in the GBCA change group than in the non-change group according to multivariable logistic regression (adjusted odds ratio [OR]: 0.35; 95% CI: 0.13-0.90; P = 0.03) and analysis with propensity score matching (14.3% [6/42] vs. 36.9% [31/84], respectively; OR: 0.32, 95% CI: 0.11-0.94; P = 0.04). A history of an ADR to iodinated contrast media (OR: 1.14, 95% CI: 0.68-1.90; P = 0.62) and premedication (adjusted OR: 2.09, 95% CI: 0.93-4.68; P = 0.07) were not significantly associated with GBCA-associated acute ADR recurrence. A separate analysis for recurrent allergic-like hypersensitivity reactions demonstrated similar results (adjusted OR: 0.20, 95% CI: 0.06-0.65; P < 0.01). Conclusion: Changing GBCAs may reduce the risk of GBCA-associated acute ADR recurrence.

Objective: To assess the effect of a new lung enhancement filter combined with deep learning image reconstruction (DLIR) algorithm on image quality and ground-glass nodule (GGN) sharpness compared to hybrid iterative reconstruction or DLIR alone. Materials and Methods: Five artificial spherical GGNs with various densities (-250, -350, -450, -550, and -630 Hounsfield units) and 10 mm in diameter were placed in a thorax anthropomorphic phantom. Four scans at four different radiation dose levels were performed using a 256-slice CT (Revolution Apex CT, GE Healthcare). Each scan was reconstructed using three different reconstruction algorithms: adaptive statistical iterative reconstruction-V at a level of 50% (AR50), Truefidelity (TF), which is a DLIR method, and TF with a lung enhancement filter (TF + Lu). Thus, 12 sets of reconstructed images were obtained and analyzed. Image noise, signal-to-noise ratio, and contrast-to-noise ratio were compared among the three reconstruction algorithms. Nodule sharpness was compared among the three reconstruction algorithms using the full-width at half-maximum value. Furthermore, subjective image quality analysis was performed. Results: AR50 demonstrated the highest level of noise, which was decreased by using TF + Lu and TF alone (P = 0.001). TF + Lu significantly improved nodule sharpness at all radiation doses compared to TF alone (P = 0.001). The nodule sharpness of TF + Lu was similar to that of AR50. Using TF alone resulted in the lowest nodule sharpness. Conclusion: Adding a lung enhancement filter to DLIR (TF + Lu) significantly improved the nodule sharpness compared to DLIR alone (TF). TF + Lu can be an effective reconstruction technique to enhance image quality and GGN evaluation in ultralow-dose chest CT scans.

Radiation recall pneumonitis is an inflammatory reaction of previously radiated lung parenchyma triggered by systemic pharmacological agents (such as chemotherapy and immunotherapy) or vaccination. Patients present with non-specific symptoms such as cough, shortness of breath, or hypoxia soon after the initiation of medication or vaccination. Careful assessment of the patient's history, including the thoracic radiation treatment plan and timing of the initiation of the triggering agent, in conjunction with CT findings, contribute to the diagnosis. Once a diagnosis is established, treatment includes cessation of the causative medication and/or initiation of steroid therapy. Differentiating this relatively rare entity from other common post-therapeutic complications in oncology patients, such as recurrent malignancy, infection, or medication-induced pneumonitis, is essential for guiding downstream clinical management.

Objective: This study investigates the long-term efficacy and safety of ultrasound (US)-guided radiofrequency ablation (RFA) for treating locally recurrent papillary thyroid cancer (PTC). Materials and Methods: We retrospectively analyzed 39 consecutive patients with 61 locally recurrent PTCs (14 males, 25 females; mean ± standard deviation age, 52.8 ± 16.7 years; range 21-92 years) who underwent US-guided RFA with curative intent between September 2008 and April 2012. A subgroup of 24 patients with 37 recurrent PTCs who had a follow-up of at least 10 years were analyzed separately. All patients were followed for changes in lesion size on US and thyroglobulin (Tg) levels at 1, 3, 6, and 12 months after RFA, with follow-up every 6-12 months thereafter. Any complications were documented during the follow-up period. Recurrence-free survival (RFS) rates were assessed using Kaplan-Meier estimates. Long-term outcomes were evaluated in patients with follow-up of at least 10 years. Results: The follow-up period ranged from 7 to 180 months (median 133 months). The RFS rates for the 39 patients at 3, 5, and 10 years were 86.8%, 75.5%, and 60.6%, respectively. Among the 24 patients with 37 recurrent PTCs followed for more than 10 years, the volume reduction rate was 99.9% (range 96%-100%), and the complete tumor disappearance rate was 91.9%. The mean serum Tg level also decreased significantly, from 2.66 ± 86.5 mIU/L before ablation to 0.43 ± 0.73 mIU/L (P < 0.001) at the final follow-up. In 14 (58.3%) of the 24 patients, Tg levels were undetectable (below 0.08 mIU/L) at the last follow-up. No life-threatening or delayed complications were observed during the 10-year follow-up period. Conclusion: The high RFS throughout the follow-up period, with efficacy and safety lasting beyond 10 years, supports US-guided RFA as a valuable option for local control of recurrent PTCs.