Yasunori Nagayama

Objectives: To evaluate the diagnostic performance of spectral imaging for differentiating intrapancreatic accessory spleen (IPAS) from hypervascular pancreatic neoplasms using portal-venous phase (PVP) spectral CT. Materials and methods: This retrospective study included patients with hypervascular pancreatic lesions identified on PVP spectral CT. Lesion and splenic densities were measured on conventional images, virtual monochromatic images (VMI; 40–140 keV), virtual non-contrast (VNC) images, iodine maps, and effective atomic number (Z_eff) maps. Relative lesion-to-spleen ratios (RLSRs), with values closer to zero indicating greater similarity to the spleen, were compared between IPAS and neoplasms; diagnostic performance in the whole cohort and among patients with pancreatic tail lesions was assessed using the area under the receiver operating characteristic curve (AUC). For pancreatic tail lesions, three radiologists visually graded IPAS likelihood using conventional imaging alone and conventional imaging plus spectral imaging. Pooled sensitivity/specificity/accuracy and intraclass correlation coefficients (ICCs) were used to evaluate visual discriminative performance and inter-observer reproducibility, respectively. Results: Eighty-five patients (median age, 63.0 [IQR: 56.0–73.0] years; 45 men) with 34 IPAS and 51 neoplasms (34 IPAS and 22 neoplasms in the pancreatic tail) were included. RLSRs were lower in IPAS than in neoplasms across all image series ( p < 0.001). In the whole-cohort/pancreatic-tail subgroup, AUCs of RLSR on conventional imaging, VNC, 40-keV VMI, iodine density, and Z_eff were 0.799/0.737, 0.835/0.899, 0.950/0.972, 0.960/0.980, and 0.969/0.992, respectively. In visual assessment, conventional plus spectral imaging improved pooled sensitivity/specificity/accuracy and ICC compared with conventional imaging alone (86.3%/90.9%/88.1% vs. 61.8%/59.1%/60.7%, 0.929 vs. 0.649, all p < 0.001). Conclusion: Spectral imaging may facilitate differentiation of IPAS from hypervascular pancreatic neoplasms using only portal-venous-phase CT. Key Points: Question Can spectral imaging applied to hypervascular pancreatic lesions differentiate intrapancreatic accessory spleen (IPAS) from hypervascular neoplasms when only a single contrast-enhanced phase is available? Findings Use of spectral imaging yielded higher quantitative and qualitative performance for differentiating IPAS from neoplasms than conventional imaging, with better interobserver reproducibility in visual assessment . Clinical relevance Evaluating spectral properties may facilitate discrimination of IPAS from hypervascular pancreatic neoplasms identified on routine portal venous phase CT that would otherwise remain indeterminate on conventional CT and require additional diagnostic procedures .

Purpose Hepatic venous outflow block (HVOB) is a potentially serious complication after hepatectomy. Although routine anatomical fixation of the remnant liver is often advocated to prevent HVOB, its universal necessity remains controversial. We conducted this study to evaluate the utility of intraoperative Doppler ultrasonography for guiding selective remnant liver fixation. Methods A total of 26 patients who underwent right-sided or central hepatectomy with transection of the falciform ligament between April 2016 and January 2025 were enrolled prospectively in this study. Intraoperative Doppler ultrasonography was used to assess venous flow in spontaneous and anatomical liver positions. Fixation using the round ligament, with or without the falciform ligament, was performed selectively when venous outflow impairment was observed. Results Eight patients (31%) required fixation. Portal vein thrombosis occurred in five patients, including one with concurrent hepatic vein thrombosis caused by incorrect positioning. Apart from the illustrative case, all thrombotic events were asymptomatic and resolved with anticoagulation. Postoperative complications and liver regeneration were comparable between the groups. Postoperative abdominal discomfort was more frequent in the anatomical group, but the difference was not significant. Conclusion Intraoperative Doppler ultrasonography may facilitate on-demand remnant liver fixation by allowing real-time assessment of venous outflow impairment. This approach may help prevent complications and avoid unnecessary fixation.

Functional assessment of the future liver remnant (FLR) has become increasingly important for improving the safety of major hepatectomy. Conventional evaluation based on computed tomography (CT) volumetry estimates anatomical liver volume but does not fully reflect the functional capacity of the remnant liver, particularly in patients with underlying liver disease or those receiving preoperative therapy. In recent years, functional liver volumetry using technetium‐99 m–labeled galactosyl human serum albumin (99mTc‐GSA) scintigraphy combined with single‐photon emission computed tomography/computed tomography (SPECT/CT) fusion imaging has emerged as a reliable method for quantitative assessment of regional liver function. This review summarizes recent advances in functional liver volumetry with particular focus on 99mTc‐GSA SPECT/CT fusion imaging and its clinical applications in patients undergoing major hepatectomy. Functional imaging enables simultaneous evaluation of FLR volume and function and has demonstrated superior predictive value for post‐hepatectomy liver failure compared with volumetric assessment alone. Functional imaging has also clarified important aspects of liver regeneration following portal vein embolization, hepatic vein embolization, and associating liver partition and portal vein ligation for staged hepatectomy, demonstrating that functional recovery often exceeds or precedes volumetric hypertrophy. Our studies using 99mTc‐GSA SPECT/CT further demonstrated that functional liver regeneration after hepatectomy occurs earlier than volumetric regeneration and that factors such as liver fibrosis, chemotherapy exposure, and hepatic venous congestion influence regional functional recovery. Integration of functional volumetry into preoperative planning can improve risk stratification and optimize surgical decision‐making.

The objective of the study is to assess the impact of super-resolution deep-learning reconstruction (SR-DLR) on image quality in low-dose thin-slice pediatric abdominal CT. Thirty-eight children (< 10 years; median age, 2.0 [IQR: 0.0-3.8] years) who had available low-radiation abdominal CT data were retrospectively analyzed. The mean size-specific dose estimate was 1.71 ± 0.38 mGy. From the raw datasets, 0.5-mm images were generated using SR-DLR developed for helical body imaging as well as hybrid-iterative reconstruction (hybrid-IR) and conventional deep-learning reconstruction (C-DLR), with matrices of 1024, 512, and 512, respectively. Quantitative assessments included measurements of image noise and contrast-to-noise ratio (CNR). Image noise characteristics were evaluated using the noise power spectrum (NPS), while edge sharpness was evaluated based on the edge-rise slope (ERS). For qualitative evaluation, noise magnitude, texture, sharpness, and small structure delineation were ranked among three reconstructions (1 = worst, 3 = best). Diagnostic confidence was scored with a five-point scale (1 = undiagnostic, 5 = most confident). Quantitative and qualitative data were compared among hybrid-IR, C-DLR, and SR-DLR. SR-DLR showed the greatest noise reduction and the highest CNR, outperforming the other reconstructions (p < 0.001). SR-DLR also achieved the highest ERS and maintained the lowest noise throughout the full range of spatial frequencies without a shift toward lower frequency. Subjective scores aligned with these quantitative findings, with SR-DLR consistently achieving the highest scores across all qualitative metrics (all p < 0.001). In conclusion, SR-DLR with 1024-matrix for helical body imaging enhanced sharpness and reduced noise in low-dose thin-slice pediatric abdominal CT, outperforming hybrid-IR and C-DLR in small structure delineation and overall diagnostic quality.

Purpose Fumarate hydratase (FH)-deficient renal cell carcinoma (RCC) is a rare and aggressive RCC subtype defined in the 2022 WHO classification. This study aimed to describe its imaging and clinicopathological features. Methods A retrospective analysis was conducted on 11 patients (12 tumors) diagnosed with FH-deficient RCC between 2015 and 2024 across multiple institutions. Clinical data, imaging findings (CT, MRI, [¹⁸F] fluorodeoxyglucose (FDG) -PET/CT), and histopathological results were reviewed. Results The median age at diagnosis was 54 years (range: 35–81), with a male predominance (64%). At presentation, distant metastases were observed in 27% of patients. Based on contrast-enhanced CT findings, tumors were morphologically classified into three types: cystic-predominant (n = 5), solid-predominant (n = 4), and purely solid (n = 3). The dynamic enhancement pattern of the solid components showed progressive enhancement in 54.5% and mild corticomedullary enhancement with delayed washout in 45.5%, suggesting vascular heterogeneity. MRI showed high signal intensity of cystic components on both T1WI and T2WI, suggestive of hemorrhage. Solid components exhibited restricted diffusion on DWI in all cases, with a median ADC value of 0.88 (range: 0.77–1.18) × 10⁻³ mm²/s. On FDG-PET/CT, solid components demonstrated elevated FDG uptake (median SUVmax: 7.25; range: 6.81–10.10). Among nine cases with available follow-up data, three (33%) developed recurrence within two years after surgery. Conclusion FH-deficient RCC has a high risk of metastasis and recurrence, requiring strict follow-up. Although definitive diagnosis relies on immunohistochemistry, imaging features—such as mixed cystic-solid morphology, hemorrhagic cysts, and, compared with clear cell RCC, lower enhancement, restricted diffusion, and higher FDG uptake—may serve as important diagnostic clues that facilitate accurate pathological diagnosis and management.

Purpose: To investigate whether virtual-monoenergetic images (VMI) from dual-layer spectral-detector computed tomography (DLCT) improve right adrenal vein (RAV) assessment before adrenal venous sampling (AVS), and portal-venous-phase (PVP) images alone can replace conventional multiphase CT combining late-arterial phase (LAP) and PVP. Methods: Sixty-three patients with primary aldosteronism who underwent LAP and PVP DLCT before AVS were retrospectively analyzed. Conventional polyenergetic-images (PEI) and VMI at 40–70 keV (VMI _40–70 ) were reconstructed. Image noise and contrast-to-noise ratio (CNR) of RAV were quantified. VMI with the highest CNR was predefined as the best-VMI. Two radiologists evaluated four image series (PEI and best-VMI at LAP and PVP) separately for RAV visibility, accessory hepatic vein (AHV) assessability, and image noise using five-point scales (1 = worst, 5 = best). RAV detection and AHV assessability rates were compared among image series. Results: In both enhancement phases, VMI _40–70 showed lower image noise and VMI _40–60 higher CNR than PEI (all p < 0.05), with VMI ₄₀ providing the highest CNR and being designated as the best VMI. Compared to PEI at LAP, CNR was lower with PEI at PVP but higher with VMI ₄₀ at PVP (both, p < 0.001). In subjective analysis, VMI ₄₀ showed better scores than PEI for image noise (LAP: 4.0 ± 0.5 vs. 2.4 ± 0.6; PVP: 4.0 ± 0.6 vs. 2.5 ± 0.5) and RAV visibility (LAP: 4.5 ± 0.8 vs. 3.5 ± 0.8; PVP: 3.7 ± 1.0 vs. 2.6 ± 0.9) (all p < 0.001). With PEI, the RAV detection rate was lower at PVP than at LAP (54.8% vs. 89.7%, p < 0.001). Use of VMI ₄₀ at PVP achieved the same detection rate as PEI at LAP (89.7%, p = 1.0) and higher AHV assessability rate than PEI at PVP (96.8% vs. 80.2%, p < 0.001). Conclusion: DLCT-VMI improved RAV assessments before AVS. Using VMI ₄₀ for PVP provided RAV depiction equivalent to PEI at LAP and superior AHV assessability to PEI at PVP, suggesting its potential as a surrogate for dedicated multiphase CT.

With the increasing use of contrast-enhanced CT, optimizing the iodinated contrast medium (ICM) dose while maintaining diagnostically adequate image quality is essential to mitigate potential adverse effects on patients, the environment, and public health, as well as to reduce medical costs and address potential supply shortages. Multi-energy CT technologies including dual-energy CT and photon-counting detector CT enable data acquisition at multiple energy spectra, allowing for material characterization beyond the capabilities of conventional single-energy CT. Recent technical advancements and the growing adoption of these technologies in clinical practice have enhanced patient care across various diagnostic tasks. Among the spectral-based imaging options offered by multi-energy CT, virtual monoenergetic imaging holds significant promise for substantial ICM dose reduction due to the drastic improvement in iodine contrast at lower energy levels. This article aims to provide an overview of multi-energy CT technology and its utility for ICM dose optimization across various clinical indications, while also discussing current issues and related topics.

Tract hemostasis using radiofrequency ablation for hepatic arterial bleeding after percutaneous transhepatic portal embolization