Purpose To evaluate the impact of adjunctive partial cryoablation on checkpoint inhibitor (CPI) immunotherapy response. Materials and Methods One hundred fifty-six mice (equal number of male and female animals) with dual-implanted tumor models were treated with dual CPI or a vehicle and randomized to treatment of a single tumor with partial cryoablation. Tumors were followed for 60 days following cryoablation for response assessment. In additional groups, the tumor microenvironment was characterized via flow cytometry, cytokine analysis, and immunohistochemistry. Statistical comparison was made between the different treatment groups regarding T-cell infiltration and activation characteristics within the noncryoablated tumor and cytokine levels within the partially ablated tumor. Additionally, qualitative assessment of T-cell activation within the cryoablated and noncryoablated tumors at immunofluorescence was carried out. Results At 60 days following treatment, CPI and adjunctive cryoablation-treated MC-38 mice had a significantly increased survival rate (79%) compared with mice treated with CPI alone (61%; P < .001). CT-26 mice also had an increased survival rate (57% vs 35%, respectively; P = .04). Following cryoablation, increases in inflammatory cytokines and chemokines within the treated tumors were observed. Flow cytometry of noncryoablated tumor showed increased CD8 T-cell activation. Immunofluorescence and histologic evaluation following cryoablation further demonstrated a robust CD8 T-cell and myeloid infiltrate. Conclusion Adjunctive cryoablation significantly increased the response to dual CPI in multiple cancer models at both partially ablated and distant (nonablated) tumor sites. Immune analysis suggests cryoablation promotes a vigorous immune response within the partially cryoablated tumor that increases activation of the adaptive immune system within distant tumor sites. Keywords: Cancer, Cryoablation, Checkpoint Inhibitor Immunotherapy, Tumor Response Supplemental material is available for this article. © RSNA, 2024.

Purpose To investigate the clinical impact and prognostic value of gallium 68 (68Ga)-labeled fibroblast activation protein inhibitor (FAPI) PET/CT in gastric mucinous adenocarcinoma (MAC) and signet ring cell carcinoma (SRCC). Materials and Methods Eighty-six participants with newly diagnosed or recurrent gastric MAC or SRCC were prospectively enrolled from April 2021 to October 2021 and underwent both fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT and 68Ga-FAPI PET/CT. The sensitivity, specificity, and accuracy of the two scans in primary and metastatic tumors were evaluated using the McNemar test. Changes of treatment strategies were recorded to compare the treatment management value of the two PET/CT scans. The maximum standardized uptake value (SUVmax) and peritoneal cancer index (PCI) were recorded for survival analysis. Progression-free survival (PFS) was defined as the time interval from the date of PET/CT scans to the date of disease progression. Results Eighty-six participants (median age, 62 years [IQR, 45-78 years]; 49 female) were evaluated. 68Ga-FAPI PET/CT showed higher diagnostic accuracy in detecting involved lymph nodes (87% [212 of 244] vs 71% [173 of 244], P < .001) and peritoneal metastases (96% [70 of 73] vs 55% [40 of 73], P < .001) than 18F-FDG PET/CT. Twenty-six participants (30% [26 of 86]) had treatment changes due to more accurate diagnosis with 68Ga-FAPI PET/CT. Additionally, the 68Ga-FAPI PCI was an independent predictor for PFS (hazard ratio, 6.9; 95% CI: 2.1, 23.1; P = .002). Conclusion 68Ga-FAPI PET/CT had higher accuracy in diagnosis of gastric MAC/SRCC compared with 18F-FDG PET/CT and demonstrated the potential to improve treatment strategies and predict prognosis. Keywords: PET/CT, Mucinous Adenocarcinoma, Signet Ring Cell Carcinoma, Oncology, Abdomen/GI, Molecular Imaging Supplemental material is available for this article. © RSNA, 2024.

Purpose To evaluate the safety and feasibility of a novel hybrid nuclear and fluoroscopy C-arm scanner to be used during the work-up procedure of hepatic radioembolization. Materials and Methods In this prospective first-in-human clinical study, 12 participants (median age, 67 years [range: 37-78 years]; nine [75%] male, three [25%] female) with liver tumors undergoing work-up for yttrium 90 radioembolization were included (ClinicalTrials.gov NCT06013774). Work-up angiography and technetium 99m-macroaggregated albumin injection were performed in an angiography suite equipped with a hybrid C-arm that could simultaneously perform fluoroscopy and planar nuclear imaging. Technetium 99m-macroaggregated albumin was injected under real-time hybrid imaging, followed by in-room SPECT imaging. Safety and feasibility were studied by assessing adverse events, technical performance, additional x-ray radiation dose, and questionnaires completed by radiologists and technologists. Results No adverse events were attributed to the hybrid C-arm scanner. The additional x-ray radiation dose was low (median, 19 Gy · cm2; minimum: 12 Gy · cm2; maximum: 21 Gy · cm2 for participants who completed all imaging steps). The interventional personnel considered use of the hybrid C-arm scanner safe and feasible, although the additional time spent in the intervention room was considered long (median, 64 minutes; minimum: 55 minutes; maximum: 77 minutes for participants who completed all imaging steps). Conclusion Use of the hybrid C-arm scanner during the work-up procedure of hepatic radioembolization was found to be safe and feasible in this first-in-human clinical study. Keywords: Angiography, Fluoroscopy, Interventional-Vascular, Radionuclide Studies, Radiosurgery, Gamma Knife, Cyberknife, SPECT, Instrumentation, Physics, Technical Aspects, Technology Assessment Supplemental material is available for this article. Published under a CC BY 4.0 license. Clinical trial registration no. NCT06013774.

Purpose To further define anatomic criteria for resection and ablation using an expert panel-based three-dimensional liver model to objectively predict local treatment recommendations for colorectal liver metastases (CRLM). Materials and Methods This study analyzed data from participants with small CRLM (≤3 cm) considered suitable for resection, thermal ablation, or irreversible electroporation (IRE), according to a multidisciplinary expert panel, who were included in two prospective multicenter trials (COLLISION [NCT03088150] and COLDFIRE-2 [NCT02082782]) between August 2017 and June 2022. Ten randomly selected participants were used to standardize the model's Couinaud segments. CRLM coordinates were measured and plotted in the model as color-coded lesions according to the treatment recommendations. Statistical validation was achieved through leave-one-out cross-validation. Results A total of 611 CRLM in 202 participants (mean age, 63 [range, 29-87] years; 138 male and 64 female) were included. Superficially located CRLM were considered suitable for resection, whereas more deep-seated CRLM were preferably ablated, with the transition zone at a subsurface depth of 3 cm. Ninety-three percent (25 of 27) of perihilar CRLM treated with IRE were at least partially located within 1 cm from the portal triad. Use of the model correctly predicted the preferred treatment in 313 of 424 CRLM (73.8%). Conclusion The results suggest that CRLM can be defined as superficial (preferably resected) and deep-seated (preferably ablated) if the tumor center is within versus beyond 3 cm from the liver surface, respectively, and as perihilar if the tumor margins extend to within 1 cm from the portal triad. Keywords: Ablation Techniques, CT, MRI, Liver, Abdomen/GI, Metastases, Oncology Supplemental material is available for this article. © RSNA, 2024.

Purpose To develop a radiology-pathology coregistration method for 1:1 automated spatial mapping between preoperative rectal MRI and ex vivo rectal whole-mount histology (WMH). Materials and Methods This retrospective study included consecutive patients with rectal adenocarcinoma who underwent total neoadjuvant therapy followed by total mesorectal excision with preoperative rectal MRI and WMH from January 2019 to January 2022. A gastrointestinal pathologist and a radiologist established three corresponding levels for each patient at rectal MRI and WMH, subsequently delineating external and internal rectal wall contours and the tumor bed at each level and defining eight point-based landmarks. An advanced deformable image coregistration model based on the linearized iterative boundary reconstruction (LIBR) approach was compared with rigid point-based registration (PBR) and state-of-the-art deformable intensity-based multiscale spectral embedding registration (MSERg). Dice similarity coefficient (DSC), modified Hausdorff distance (MHD), and target registration error (TRE) across patients were calculated to assess the coregistration accuracy of each method. Results Eighteen patients (mean age, 54 years ± 13 [SD]; nine female) were included. LIBR demonstrated higher DSC versus PBR for external and internal rectal wall contours and tumor bed (external: 0.95 ± 0.03 vs 0.86 ± 0.04, respectively, P < .001; internal: 0.71 ± 0.21 vs 0.61 ± 0.21, P < .001; tumor bed: 0.61 ± 0.17 vs 0.52 ± 0.17, P = .001) and versus MSERg for internal rectal wall contours (0.71 ± 0.21 vs 0.63 ± 0.18, respectively; P < .001). LIBR demonstrated lower MHD versus PBR for external and internal rectal wall contours and tumor bed (external: 0.56 ± 0.25 vs 1.68 ± 0.56, respectively, P < .001; internal: 1.00 ± 0.35 vs 1.62 ± 0.59, P < .001; tumor bed: 2.45 ± 0.99 vs 2.69 ± 1.05, P = .03) and versus MSERg for internal rectal wall contours (1.00 ± 0.35 vs 1.62 ± 0.59, respectively; P < .001). LIBR demonstrated lower TRE (1.54 ± 0.39) versus PBR (2.35 ± 1.19, P = .003) and MSERg (2.36 ± 1.43, P = .03). Computation time per WMH slice for LIBR was 35.1 seconds ± 12.1. Conclusion This study demonstrates feasibility of accurate MRI-WMH coregistration using the advanced LIBR method. Keywords: MR Imaging, Abdomen/GI, Rectum, Oncology Supplemental material is available for this article. © RSNA, 2024.

Purpose To compare the diagnostic performance of time-intensity curve (TIC) analysis and subjective visual assessment of contrast-enhanced US (CEUS) when integrated with the Ovarian-Adnexal Reporting and Data System (O-RADS) US risk stratification system for characterizing adnexal lesions with solid components. Materials and Methods In this prospective multicenter study conducted from September 2021 to December 2022, female individuals with suspected adnexal lesions containing solid components detected at routine US were enrolled. All participants underwent preoperative CEUS examinations. Histopathologic findings were used as the reference standard for diagnosis. Lesions were classified according to the O-RADS US system. Enhancement of solid tissue compared with the outer myometrium was evaluated using both TIC analysis and subjective visual assessment. The diagnostic performance of O-RADS alone and each CEUS assessment method when integrated with the O-RADS US system was assessed and compared using receiver operating characteristic curve analysis. Results A total of 180 lesions (80 malignant and 100 benign histopathologic outcomes) in 175 participants (median age, 47 years [IQR, 33-56]) were analyzed. Incorporating CEUS (assessed through both TIC analysis and subjective visual assessment) with O-RADS US showed significantly improved diagnostic performance over O-RADS US alone, with an area under the receiver operating characteristic curve (AUC) of 0.86 (95% CI: 0.80, 0.91) compared with 0.78 (95% CI: 0.71, 0.84). No evidence of a difference was observed between the AUCs of TIC analysis and subjective visual assessment in the enhancement evaluation of solid tissue with CEUS for adnexal malignancy categorization (P = .83). Conclusion Subjective visual assessment and TIC analysis of CEUS features when integrated with the O-RADS US scoring system showed comparable diagnostic performance in assigning adnexal malignancy risk. Keywords: Adnexal Lesions, Contrast-enhanced US, O-RADS, Time-intensity Curve Analysis Supplemental material is available for this article. © RSNA, 2024.

Neuroblastoma commonly occurs in children. MRI is a radiation-free imaging modality and has played an important role in identifying image-defined risk factors of neuroblastoma, providing necessary guidance for surgical resection and treatment response evaluation. However, image-defined risk factors are limited to providing structural information about neuroblastoma. With the evolution of MRI technologies, quantitative MRI can not only help assess image-defined risk factors but can also quantitatively reflect the biologic features of neuroblastoma in a noninvasive manner. Therefore, compared with anatomic imaging, these emerging quantitative MRI technologies are expected to provide more imaging biomarkers for the management of neuroblastoma. This review article discusses the current applications of quantitative MRI technologies in evaluating childhood neuroblastoma. Keywords: Pediatrics, MR-Functional Imaging, Children, MRI, Neuroblastoma, Quantitative Imaging © RSNA, 2024.

Purpose To evaluate the performance of an artificial intelligence (AI) model in detecting overall and clinically significant prostate cancer (csPCa)-positive lesions on paired external and in-house biparametric MRI (bpMRI) scans and assess performance differences between each dataset. Materials and Methods This single-center retrospective study included patients who underwent prostate MRI at an external institution and were rescanned at the authors' institution between May 2015 and May 2022. A genitourinary radiologist performed prospective readouts on in-house MRI scans following the Prostate Imaging Reporting and Data System (PI-RADS) version 2.0 or 2.1 and retrospective image quality assessments for all scans. A subgroup of patients underwent an MRI/US fusion-guided biopsy. A bpMRI-based lesion detection AI model previously developed using a completely separate dataset was tested on both MRI datasets. Detection rates were compared between external and in-house datasets with use of the paired comparison permutation tests. Factors associated with AI detection performance were assessed using multivariable generalized mixed-effects models, incorporating features selected through forward stepwise regression based on the Akaike information criterion. Results The study included 201 male patients (median age, 66 years [IQR, 62-70 years]; prostate-specific antigen density, 0.14 ng/mL2 [IQR, 0.10-0.22 ng/mL2]) with a median interval between external and in-house MRI scans of 182 days (IQR, 97-383 days). For intraprostatic lesions, AI detected 39.7% (149 of 375) on external and 56.0% (210 of 375) on in-house MRI scans (P < .001). For csPCa-positive lesions, AI detected 61% (54 of 89) on external and 79% (70 of 89) on in-house MRI scans (P < .001). On external MRI scans, better overall lesion detection was associated with a higher PI-RADS score (odds ratio [OR] = 1.57; P = .005), larger lesion diameter (OR = 3.96; P < .001), better diffusion-weighted MRI quality (OR = 1.53; P = .02), and fewer lesions at MRI (OR = 0.78; P = .045). Better csPCa detection was associated with a shorter MRI interval between external and in-house scans (OR = 0.58; P = .03) and larger lesion size (OR = 10.19; P < .001). Conclusion The AI model exhibited modest performance in identifying both overall and csPCa-positive lesions on external bpMRI scans. Keywords: MR Imaging, Urinary, Prostate Supplemental material is available for this article. © RSNA, 2024.