TL;DR
Attenuation change utilizing VUE images and iodine quantification can differentiate enhancing from nonenhancing hyperdense adnexal lesions at PCCT with excellent diagnostic performance.
BACKGROUND To investigate whether virtual unenhanced (VUE) images can permit selective omission of true unenhanced (TUE) images in multiphasic parotid dual-energy CT (DECT) without compromising attenuation accuracy or diagnostic performance. MATERIALS AND METHODS This retrospective study included 446 lesions from 436 patients with surgically confirmed parotid lesions who underwent three-phase DECT (TUE, early and late contrast); VUE was reconstructed from both contrast phases. Agreement between VUE and TUE attenuation was assessed using Bland-Altman analysis and two one-sided tests (TOST; equivalence margin, ±10 HU), both overall and across six histopathological subgroups. Lesion detection and border clarity were compared between VUE and TUE images. XGBoost-based six-category classifiers using TUE, VUE_C1, or VUE_C2 images as input were compared to evaluate diagnostic performance. The radiation dose attributable to the TUE acquisition was estimated from the dose-length product. RESULTS VUE reproduced lesion attenuation with a mean bias of less than 1 HU. TOST confirmed equivalence overall and across all six subgroups (p < 0.001), with 84.3% and 81.6% of differences within ± 10 HU. Six-category XGBoost classifiers demonstrated comparable diagnostic performance across TUE, VUE_C1, and VUE_C2 baselines. SHAP feature importance showed strong correlation across models. Background gland attenuation was overestimated on VUE by 14.8 and 16.7 HU, while lesion detection and border clarity were modestly reduced. Omitting the TUE acquisition would provide an estimated dose reduction of 2.41 ± 0.37 mSv. CONCLUSION VUE is quantitatively equivalent to TUE for parotid lesion attenuation and largely preserves internally validated diagnostic performance. These findings support reduced-dose DECT protocols with selective omission of TUE in appropriately selected patients, pending broader multicentre and multi-vendor validation.
Background: Focal hepatic lesions span a wide spectrum from benign incidental findings to aggressive malignancies, and accurate characterisation is essential for management. Conventional grayscale ultrasonography is the usual first-line modality but is limited by artefacts, low signal-to-noise ratio and poor margin delineation. Tissue harmonic imaging (THI) reconstructs images from harmonic signals generated within tissue, potentially improving image quality. This study compared THI with conventional ultrasonography and assessed its diagnostic performance against histopathology. Materials and Methods: In this prospective observational study, 80 patients with focal hepatic lesions underwent paired conventional ultrasonography and THI. Lesion conspicuity, margin definition, artefact burden, signal-to-noise ratio, posterior acoustic enhancement, fluid–solid differentiation and overall image quality were graded on an ordinal scale by two observers. Imaging was correlated with histopathology obtained by fine-needle aspiration cytology or biopsy. Paired image-quality scores were compared using the Wilcoxon signed-rank test. Results: The cohort was predominantly elderly (mean age 62.5 years) and male (67.5%), with multifocal, right-lobe, hypoechoic or heterogeneously hypoechoic lesions predominating. Metastatic disease (47.5%) and hepatocellular carcinoma (38.8%) were the commonest diagnoses. THI was significantly superior for lesion conspicuity, margin definition, artefact suppression, signal-to-noise ratio, posterior acoustic enhancement, fluid–solid differentiation and overall image quality (p < 0.05). Against histopathology, THI showed a sensitivity of 85.5%, specificity of 77.8%, positive predictive value of 93.0%, negative predictive value of 60.9% and accuracy of 83.8% (area under the curve 0.816). Conclusion: Tissue harmonic imaging significantly improves image quality and diagnostic confidence over conventional ultrasonography and should be routinely incorporated into hepatic ultrasound protocols. Key words: Tissue harmonic imaging, Conventional ultrasonography, Focal hepatic lesions, Image quality, Hepatocellular carcinoma, Liver metastases.
Background: CT is limited for local staging of bladder cancer due to insufficient soft-tissue contrast. Photon-counting detector (PCD) CT with low-keV virtual monoenergetic images (VMIs) provides greater lesion contrast with acceptable image noise and high resolution and may aid assessment for muscle invasion. Objective: To compare the performance of low-keV VMIs and conventional polychromatic images for diagnosing muscle invasion on PCD CT in patients with bladder cancer. Methods: This prospective study included patients with pathologically confirmed bladder cancer who underwent preoperative PCD CT between August 2025 and March 2026. VMIs at 40, 50, 60, and 70 keV and T3D images (representing conventional polychromatic images) were reconstructed from portal venous-phase acquisitions. Two radiologists assessed objective and subjective image quality measures to identify an optimal VMI reconstruction. Three radiologists independently reviewed the optimal VMI and T3D reconstructions to assess muscle invasion using an algorithm based on bladder wall continuity at the lesion base, incorporating ancillary features (stalk, inner-layer enhancement, tumor size ≤1 cm) in equivocal cases. Diagnostic performance was assessed using transurethral resection or cystectomy as the reference. Results: The analysis included 110 patients (81 male, 29 female; median age, 63 years); 27 had muscle-invasive disease. Among VMI reconstructions, 40 keV was selected as the optimal energy level based on highest tumor SNR, tumor CNR, subjective tumor conspicuity, and subjective tumor-bladder wall interface delineation. Accuracy, sensitivity, and specificity for muscle invasion for reader 1 were 86.4%, 96.3%, and 83.1% for 40-keV VMIs and 66.4%, 96.3%, and 56.6% for T3D; for reader 2 were 87.3%, 88.9%, and 86.7% for 40-keV VMIs and 71.8%, 85.2%, and 67.5% for T3D; and for reader 3 were 80.9%, 88.9%, and 78.3% for 40-keV VMIs and 65.5%, 85.2%, and 59.0% for T3D. For all readers, accuracy and specificity were higher for 40-keV VMIs than for T3D (p<.001), whereas sensitivity was not significantly different (p>.99). Conclusion: In patients with bladder cancer undergoing PCD CT, diagnostic performance for muscle invasion was greater for 40-keV VMIs than for conventional polychromatic images. Clinical Impact: PCD CT with low-keV VMIs may have a complementary role for preoperative local staging of bladder cancer.